anno_start	anno_end	anno_text	entity_type	sentence	section
3	11	extended	protein_state	An extended U2AF65–RNA-binding domain recognizes the 3′ splice site signal	TITLE
12	37	U2AF65–RNA-binding domain	structure_element	An extended U2AF65–RNA-binding domain recognizes the 3′ splice site signal	TITLE
53	67	3′ splice site	site	An extended U2AF65–RNA-binding domain recognizes the 3′ splice site signal	TITLE
18	42	pre-mRNA splicing factor	protein_type	How the essential pre-mRNA splicing factor U2AF65 recognizes the polypyrimidine (Py) signals of the major class of 3′ splice sites in human gene transcripts remains incompletely understood.	ABSTRACT
43	49	U2AF65	protein	How the essential pre-mRNA splicing factor U2AF65 recognizes the polypyrimidine (Py) signals of the major class of 3′ splice sites in human gene transcripts remains incompletely understood.	ABSTRACT
65	79	polypyrimidine	chemical	How the essential pre-mRNA splicing factor U2AF65 recognizes the polypyrimidine (Py) signals of the major class of 3′ splice sites in human gene transcripts remains incompletely understood.	ABSTRACT
81	83	Py	chemical	How the essential pre-mRNA splicing factor U2AF65 recognizes the polypyrimidine (Py) signals of the major class of 3′ splice sites in human gene transcripts remains incompletely understood.	ABSTRACT
115	130	3′ splice sites	site	How the essential pre-mRNA splicing factor U2AF65 recognizes the polypyrimidine (Py) signals of the major class of 3′ splice sites in human gene transcripts remains incompletely understood.	ABSTRACT
134	139	human	species	How the essential pre-mRNA splicing factor U2AF65 recognizes the polypyrimidine (Py) signals of the major class of 3′ splice sites in human gene transcripts remains incompletely understood.	ABSTRACT
3	29	determined four structures	experimental_method	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
36	44	extended	protein_state	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
45	70	U2AF65–RNA-binding domain	structure_element	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
71	79	bound to	protein_state	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
80	105	Py-tract oligonucleotides	chemical	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
150	160	structures	evidence	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
175	206	RNA binding and splicing assays	experimental_method	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
235	241	U2AF65	protein	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
242	263	inter-domain residues	site	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
281	291	contiguous	structure_element	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
298	308	nucleotide	chemical	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
309	317	Py tract	chemical	We determined four structures of an extended U2AF65–RNA-binding domain bound to Py-tract oligonucleotides at resolutions between 2.0 and 1.5 Å. These structures together with RNA binding and splicing assays reveal unforeseen roles for U2AF65 inter-domain residues in recognizing a contiguous, nine-nucleotide Py tract.	ABSTRACT
4	10	U2AF65	protein	The U2AF65 linker residues between the dual RNA recognition motifs (RRMs) recognize the central nucleotide, whereas the N- and C-terminal RRM extensions recognize the 3′ terminus and third nucleotide.	ABSTRACT
11	17	linker	structure_element	The U2AF65 linker residues between the dual RNA recognition motifs (RRMs) recognize the central nucleotide, whereas the N- and C-terminal RRM extensions recognize the 3′ terminus and third nucleotide.	ABSTRACT
44	66	RNA recognition motifs	structure_element	The U2AF65 linker residues between the dual RNA recognition motifs (RRMs) recognize the central nucleotide, whereas the N- and C-terminal RRM extensions recognize the 3′ terminus and third nucleotide.	ABSTRACT
68	72	RRMs	structure_element	The U2AF65 linker residues between the dual RNA recognition motifs (RRMs) recognize the central nucleotide, whereas the N- and C-terminal RRM extensions recognize the 3′ terminus and third nucleotide.	ABSTRACT
96	106	nucleotide	chemical	The U2AF65 linker residues between the dual RNA recognition motifs (RRMs) recognize the central nucleotide, whereas the N- and C-terminal RRM extensions recognize the 3′ terminus and third nucleotide.	ABSTRACT
138	152	RRM extensions	structure_element	The U2AF65 linker residues between the dual RNA recognition motifs (RRMs) recognize the central nucleotide, whereas the N- and C-terminal RRM extensions recognize the 3′ terminus and third nucleotide.	ABSTRACT
167	178	3′ terminus	site	The U2AF65 linker residues between the dual RNA recognition motifs (RRMs) recognize the central nucleotide, whereas the N- and C-terminal RRM extensions recognize the 3′ terminus and third nucleotide.	ABSTRACT
183	188	third	residue_number	The U2AF65 linker residues between the dual RNA recognition motifs (RRMs) recognize the central nucleotide, whereas the N- and C-terminal RRM extensions recognize the 3′ terminus and third nucleotide.	ABSTRACT
189	199	nucleotide	chemical	The U2AF65 linker residues between the dual RNA recognition motifs (RRMs) recognize the central nucleotide, whereas the N- and C-terminal RRM extensions recognize the 3′ terminus and third nucleotide.	ABSTRACT
0	20	Single-molecule FRET	experimental_method	Single-molecule FRET experiments suggest that conformational selection and induced fit of the U2AF65 RRMs are complementary mechanisms for Py-tract association.	ABSTRACT
94	100	U2AF65	protein	Single-molecule FRET experiments suggest that conformational selection and induced fit of the U2AF65 RRMs are complementary mechanisms for Py-tract association.	ABSTRACT
101	105	RRMs	structure_element	Single-molecule FRET experiments suggest that conformational selection and induced fit of the U2AF65 RRMs are complementary mechanisms for Py-tract association.	ABSTRACT
139	147	Py-tract	chemical	Single-molecule FRET experiments suggest that conformational selection and induced fit of the U2AF65 RRMs are complementary mechanisms for Py-tract association.	ABSTRACT
110	121	splice site	site	Altogether, these results advance the mechanistic understanding of molecular recognition for a major class of splice site signals.	ABSTRACT
5	29	pre-mRNA splicing factor	protein_type	 The pre-mRNA splicing factor U2AF65 recognizes 3′ splice sites in human gene transcripts, but the details are not fully understood.	ABSTRACT
30	36	U2AF65	protein	 The pre-mRNA splicing factor U2AF65 recognizes 3′ splice sites in human gene transcripts, but the details are not fully understood.	ABSTRACT
48	63	3′ splice sites	site	 The pre-mRNA splicing factor U2AF65 recognizes 3′ splice sites in human gene transcripts, but the details are not fully understood.	ABSTRACT
67	72	human	species	 The pre-mRNA splicing factor U2AF65 recognizes 3′ splice sites in human gene transcripts, but the details are not fully understood.	ABSTRACT
25	31	U2AF65	protein	Here, the authors report U2AF65 structures and single molecule FRET that reveal mechanistic insights into splice site recognition.	ABSTRACT
32	42	structures	evidence	Here, the authors report U2AF65 structures and single molecule FRET that reveal mechanistic insights into splice site recognition.	ABSTRACT
47	67	single molecule FRET	experimental_method	Here, the authors report U2AF65 structures and single molecule FRET that reveal mechanistic insights into splice site recognition.	ABSTRACT
106	117	splice site	site	Here, the authors report U2AF65 structures and single molecule FRET that reveal mechanistic insights into splice site recognition.	ABSTRACT
64	80	pre-mRNA regions	structure_element	The differential skipping or inclusion of alternatively spliced pre-mRNA regions is a major source of diversity for nearly all human gene transcripts.	INTRO
127	132	human	species	The differential skipping or inclusion of alternatively spliced pre-mRNA regions is a major source of diversity for nearly all human gene transcripts.	INTRO
4	16	splice sites	site	The splice sites are marked by relatively short consensus sequences and are regulated by additional pre-mRNA motifs (reviewed in ref.).	INTRO
42	67	short consensus sequences	structure_element	The splice sites are marked by relatively short consensus sequences and are regulated by additional pre-mRNA motifs (reviewed in ref.).	INTRO
100	115	pre-mRNA motifs	structure_element	The splice sites are marked by relatively short consensus sequences and are regulated by additional pre-mRNA motifs (reviewed in ref.).	INTRO
7	21	3′ splice site	site	At the 3′ splice site of the major intron class, these include a polypyrimidine (Py) tract comprising primarily Us or Cs, which is preceded by a branch point sequence (BPS) that ultimately serves as the nucleophile in the splicing reaction and an AG-dinucleotide at the 3′ splice site junction.	INTRO
65	90	polypyrimidine (Py) tract	chemical	At the 3′ splice site of the major intron class, these include a polypyrimidine (Py) tract comprising primarily Us or Cs, which is preceded by a branch point sequence (BPS) that ultimately serves as the nucleophile in the splicing reaction and an AG-dinucleotide at the 3′ splice site junction.	INTRO
112	113	U	residue_name	At the 3′ splice site of the major intron class, these include a polypyrimidine (Py) tract comprising primarily Us or Cs, which is preceded by a branch point sequence (BPS) that ultimately serves as the nucleophile in the splicing reaction and an AG-dinucleotide at the 3′ splice site junction.	INTRO
118	119	C	residue_name	At the 3′ splice site of the major intron class, these include a polypyrimidine (Py) tract comprising primarily Us or Cs, which is preceded by a branch point sequence (BPS) that ultimately serves as the nucleophile in the splicing reaction and an AG-dinucleotide at the 3′ splice site junction.	INTRO
145	166	branch point sequence	site	At the 3′ splice site of the major intron class, these include a polypyrimidine (Py) tract comprising primarily Us or Cs, which is preceded by a branch point sequence (BPS) that ultimately serves as the nucleophile in the splicing reaction and an AG-dinucleotide at the 3′ splice site junction.	INTRO
168	171	BPS	site	At the 3′ splice site of the major intron class, these include a polypyrimidine (Py) tract comprising primarily Us or Cs, which is preceded by a branch point sequence (BPS) that ultimately serves as the nucleophile in the splicing reaction and an AG-dinucleotide at the 3′ splice site junction.	INTRO
247	262	AG-dinucleotide	chemical	At the 3′ splice site of the major intron class, these include a polypyrimidine (Py) tract comprising primarily Us or Cs, which is preceded by a branch point sequence (BPS) that ultimately serves as the nucleophile in the splicing reaction and an AG-dinucleotide at the 3′ splice site junction.	INTRO
270	284	3′ splice site	site	At the 3′ splice site of the major intron class, these include a polypyrimidine (Py) tract comprising primarily Us or Cs, which is preceded by a branch point sequence (BPS) that ultimately serves as the nucleophile in the splicing reaction and an AG-dinucleotide at the 3′ splice site junction.	INTRO
43	51	pre-mRNA	chemical	Disease-causing mutations often compromise pre-mRNA splicing (reviewed in refs), yet a priori predictions of splice sites and the consequences of their mutations are challenged by the brevity and degeneracy of known splice site sequences.	INTRO
109	121	splice sites	site	Disease-causing mutations often compromise pre-mRNA splicing (reviewed in refs), yet a priori predictions of splice sites and the consequences of their mutations are challenged by the brevity and degeneracy of known splice site sequences.	INTRO
216	227	splice site	site	Disease-causing mutations often compromise pre-mRNA splicing (reviewed in refs), yet a priori predictions of splice sites and the consequences of their mutations are challenged by the brevity and degeneracy of known splice site sequences.	INTRO
16	26	structures	evidence	High-resolution structures of intact splicing factor–RNA complexes would offer key insights regarding the juxtaposition of the distinct splice site consensus sequences and their relationship to disease-causing point mutations.	INTRO
30	36	intact	protein_state	High-resolution structures of intact splicing factor–RNA complexes would offer key insights regarding the juxtaposition of the distinct splice site consensus sequences and their relationship to disease-causing point mutations.	INTRO
37	56	splicing factor–RNA	complex_assembly	High-resolution structures of intact splicing factor–RNA complexes would offer key insights regarding the juxtaposition of the distinct splice site consensus sequences and their relationship to disease-causing point mutations.	INTRO
136	147	splice site	site	High-resolution structures of intact splicing factor–RNA complexes would offer key insights regarding the juxtaposition of the distinct splice site consensus sequences and their relationship to disease-causing point mutations.	INTRO
16	40	pre-mRNA splicing factor	protein_type	The early-stage pre-mRNA splicing factor U2AF65 is essential for viability in vertebrates and other model organisms (for example, ref.).	INTRO
41	47	U2AF65	protein	The early-stage pre-mRNA splicing factor U2AF65 is essential for viability in vertebrates and other model organisms (for example, ref.).	INTRO
78	89	vertebrates	taxonomy_domain	The early-stage pre-mRNA splicing factor U2AF65 is essential for viability in vertebrates and other model organisms (for example, ref.).	INTRO
21	29	assembly	complex_assembly	A tightly controlled assembly among U2AF65, the pre-mRNA, and partner proteins sequentially identifies the 3′ splice site and promotes association of the spliceosome, which ultimately accomplishes the task of splicing.	INTRO
36	42	U2AF65	protein	A tightly controlled assembly among U2AF65, the pre-mRNA, and partner proteins sequentially identifies the 3′ splice site and promotes association of the spliceosome, which ultimately accomplishes the task of splicing.	INTRO
48	56	pre-mRNA	chemical	A tightly controlled assembly among U2AF65, the pre-mRNA, and partner proteins sequentially identifies the 3′ splice site and promotes association of the spliceosome, which ultimately accomplishes the task of splicing.	INTRO
107	121	3′ splice site	site	A tightly controlled assembly among U2AF65, the pre-mRNA, and partner proteins sequentially identifies the 3′ splice site and promotes association of the spliceosome, which ultimately accomplishes the task of splicing.	INTRO
154	165	spliceosome	complex_assembly	A tightly controlled assembly among U2AF65, the pre-mRNA, and partner proteins sequentially identifies the 3′ splice site and promotes association of the spliceosome, which ultimately accomplishes the task of splicing.	INTRO
10	16	U2AF65	protein	Initially U2AF65 recognizes the Py-tract splice site signal.	INTRO
32	40	Py-tract	chemical	Initially U2AF65 recognizes the Py-tract splice site signal.	INTRO
41	52	splice site	site	Initially U2AF65 recognizes the Py-tract splice site signal.	INTRO
13	28	ternary complex	complex_assembly	In turn, the ternary complex of U2AF65 with SF1 and U2AF35 identifies the surrounding BPS and 3′ splice site junctions.	INTRO
32	38	U2AF65	protein	In turn, the ternary complex of U2AF65 with SF1 and U2AF35 identifies the surrounding BPS and 3′ splice site junctions.	INTRO
44	47	SF1	protein	In turn, the ternary complex of U2AF65 with SF1 and U2AF35 identifies the surrounding BPS and 3′ splice site junctions.	INTRO
52	58	U2AF35	protein	In turn, the ternary complex of U2AF65 with SF1 and U2AF35 identifies the surrounding BPS and 3′ splice site junctions.	INTRO
86	89	BPS	site	In turn, the ternary complex of U2AF65 with SF1 and U2AF35 identifies the surrounding BPS and 3′ splice site junctions.	INTRO
94	108	3′ splice site	site	In turn, the ternary complex of U2AF65 with SF1 and U2AF35 identifies the surrounding BPS and 3′ splice site junctions.	INTRO
13	19	U2AF65	protein	Subsequently U2AF65 recruits the U2 small nuclear ribonucleoprotein particle (snRNP) and ultimately dissociates from the active spliceosome.	INTRO
33	76	U2 small nuclear ribonucleoprotein particle	complex_assembly	Subsequently U2AF65 recruits the U2 small nuclear ribonucleoprotein particle (snRNP) and ultimately dissociates from the active spliceosome.	INTRO
78	83	snRNP	complex_assembly	Subsequently U2AF65 recruits the U2 small nuclear ribonucleoprotein particle (snRNP) and ultimately dissociates from the active spliceosome.	INTRO
121	127	active	protein_state	Subsequently U2AF65 recruits the U2 small nuclear ribonucleoprotein particle (snRNP) and ultimately dissociates from the active spliceosome.	INTRO
128	139	spliceosome	complex_assembly	Subsequently U2AF65 recruits the U2 small nuclear ribonucleoprotein particle (snRNP) and ultimately dissociates from the active spliceosome.	INTRO
0	29	Biochemical characterizations	experimental_method	Biochemical characterizations of U2AF65 demonstrated that tandem RNA recognition motifs (RRM1 and RRM2) recognize the Py tract (Fig. 1a).	INTRO
33	39	U2AF65	protein	Biochemical characterizations of U2AF65 demonstrated that tandem RNA recognition motifs (RRM1 and RRM2) recognize the Py tract (Fig. 1a).	INTRO
65	87	RNA recognition motifs	structure_element	Biochemical characterizations of U2AF65 demonstrated that tandem RNA recognition motifs (RRM1 and RRM2) recognize the Py tract (Fig. 1a).	INTRO
89	93	RRM1	structure_element	Biochemical characterizations of U2AF65 demonstrated that tandem RNA recognition motifs (RRM1 and RRM2) recognize the Py tract (Fig. 1a).	INTRO
98	102	RRM2	structure_element	Biochemical characterizations of U2AF65 demonstrated that tandem RNA recognition motifs (RRM1 and RRM2) recognize the Py tract (Fig. 1a).	INTRO
118	126	Py tract	chemical	Biochemical characterizations of U2AF65 demonstrated that tandem RNA recognition motifs (RRM1 and RRM2) recognize the Py tract (Fig. 1a).	INTRO
10	28	crystal structures	evidence	Milestone crystal structures of the core U2AF65 RRM1 and RRM2 connected by a shortened inter-RRM linker (dU2AF651,2) detailed a subset of nucleotide interactions with the individual U2AF65 RRMs.	INTRO
36	40	core	protein_state	Milestone crystal structures of the core U2AF65 RRM1 and RRM2 connected by a shortened inter-RRM linker (dU2AF651,2) detailed a subset of nucleotide interactions with the individual U2AF65 RRMs.	INTRO
41	47	U2AF65	protein	Milestone crystal structures of the core U2AF65 RRM1 and RRM2 connected by a shortened inter-RRM linker (dU2AF651,2) detailed a subset of nucleotide interactions with the individual U2AF65 RRMs.	INTRO
48	52	RRM1	structure_element	Milestone crystal structures of the core U2AF65 RRM1 and RRM2 connected by a shortened inter-RRM linker (dU2AF651,2) detailed a subset of nucleotide interactions with the individual U2AF65 RRMs.	INTRO
57	61	RRM2	structure_element	Milestone crystal structures of the core U2AF65 RRM1 and RRM2 connected by a shortened inter-RRM linker (dU2AF651,2) detailed a subset of nucleotide interactions with the individual U2AF65 RRMs.	INTRO
77	86	shortened	protein_state	Milestone crystal structures of the core U2AF65 RRM1 and RRM2 connected by a shortened inter-RRM linker (dU2AF651,2) detailed a subset of nucleotide interactions with the individual U2AF65 RRMs.	INTRO
87	103	inter-RRM linker	structure_element	Milestone crystal structures of the core U2AF65 RRM1 and RRM2 connected by a shortened inter-RRM linker (dU2AF651,2) detailed a subset of nucleotide interactions with the individual U2AF65 RRMs.	INTRO
105	115	dU2AF651,2	mutant	Milestone crystal structures of the core U2AF65 RRM1 and RRM2 connected by a shortened inter-RRM linker (dU2AF651,2) detailed a subset of nucleotide interactions with the individual U2AF65 RRMs.	INTRO
182	188	U2AF65	protein	Milestone crystal structures of the core U2AF65 RRM1 and RRM2 connected by a shortened inter-RRM linker (dU2AF651,2) detailed a subset of nucleotide interactions with the individual U2AF65 RRMs.	INTRO
189	193	RRMs	structure_element	Milestone crystal structures of the core U2AF65 RRM1 and RRM2 connected by a shortened inter-RRM linker (dU2AF651,2) detailed a subset of nucleotide interactions with the individual U2AF65 RRMs.	INTRO
13	16	NMR	experimental_method	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
17	26	structure	evidence	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
45	57	side-by-side	protein_state	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
77	84	minimal	protein_state	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
85	91	U2AF65	protein	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
92	96	RRM1	structure_element	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
101	105	RRM2	structure_element	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
121	127	linker	structure_element	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
131	145	natural length	protein_state	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
147	156	U2AF651,2	mutant	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
179	189	dU2AF651,2	mutant	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
190	208	crystal structures	evidence	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
213	216	RNA	chemical	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
261	277	inter-RRM linker	structure_element	A subsequent NMR structure characterized the side-by-side arrangement of the minimal U2AF65 RRM1 and RRM2 connected by a linker of natural length (U2AF651,2), yet depended on the dU2AF651,2 crystal structures for RNA interactions and an ab initio model for the inter-RRM linker conformation.	INTRO
38	46	Py-tract	chemical	As such, the molecular mechanisms for Py-tract recognition by the intact U2AF65–RNA-binding domain remained unknown.	INTRO
66	72	intact	protein_state	As such, the molecular mechanisms for Py-tract recognition by the intact U2AF65–RNA-binding domain remained unknown.	INTRO
73	98	U2AF65–RNA-binding domain	structure_element	As such, the molecular mechanisms for Py-tract recognition by the intact U2AF65–RNA-binding domain remained unknown.	INTRO
13	34	X-ray crystallography	experimental_method	Here, we use X-ray crystallography and biochemical studies to reveal new roles in Py-tract recognition for the inter-RRM linker and key residues surrounding the core U2AF65 RRMs.	INTRO
39	58	biochemical studies	experimental_method	Here, we use X-ray crystallography and biochemical studies to reveal new roles in Py-tract recognition for the inter-RRM linker and key residues surrounding the core U2AF65 RRMs.	INTRO
82	90	Py-tract	chemical	Here, we use X-ray crystallography and biochemical studies to reveal new roles in Py-tract recognition for the inter-RRM linker and key residues surrounding the core U2AF65 RRMs.	INTRO
111	127	inter-RRM linker	structure_element	Here, we use X-ray crystallography and biochemical studies to reveal new roles in Py-tract recognition for the inter-RRM linker and key residues surrounding the core U2AF65 RRMs.	INTRO
161	165	core	protein_state	Here, we use X-ray crystallography and biochemical studies to reveal new roles in Py-tract recognition for the inter-RRM linker and key residues surrounding the core U2AF65 RRMs.	INTRO
166	172	U2AF65	protein	Here, we use X-ray crystallography and biochemical studies to reveal new roles in Py-tract recognition for the inter-RRM linker and key residues surrounding the core U2AF65 RRMs.	INTRO
173	177	RRMs	structure_element	Here, we use X-ray crystallography and biochemical studies to reveal new roles in Py-tract recognition for the inter-RRM linker and key residues surrounding the core U2AF65 RRMs.	INTRO
7	56	single-molecule Förster resonance energy transfer	experimental_method	We use single-molecule Förster resonance energy transfer (smFRET) to characterize the conformational dynamics of this extended U2AF65–RNA-binding domain during Py-tract recognition.	INTRO
58	64	smFRET	experimental_method	We use single-molecule Förster resonance energy transfer (smFRET) to characterize the conformational dynamics of this extended U2AF65–RNA-binding domain during Py-tract recognition.	INTRO
86	109	conformational dynamics	evidence	We use single-molecule Förster resonance energy transfer (smFRET) to characterize the conformational dynamics of this extended U2AF65–RNA-binding domain during Py-tract recognition.	INTRO
118	126	extended	protein_state	We use single-molecule Förster resonance energy transfer (smFRET) to characterize the conformational dynamics of this extended U2AF65–RNA-binding domain during Py-tract recognition.	INTRO
127	152	U2AF65–RNA-binding domain	structure_element	We use single-molecule Förster resonance energy transfer (smFRET) to characterize the conformational dynamics of this extended U2AF65–RNA-binding domain during Py-tract recognition.	INTRO
160	168	Py-tract	chemical	We use single-molecule Förster resonance energy transfer (smFRET) to characterize the conformational dynamics of this extended U2AF65–RNA-binding domain during Py-tract recognition.	INTRO
8	14	U2AF65	protein	Cognate U2AF65–Py-tract recognition requires RRM extensions	RESULTS
15	23	Py-tract	chemical	Cognate U2AF65–Py-tract recognition requires RRM extensions	RESULTS
45	59	RRM extensions	structure_element	Cognate U2AF65–Py-tract recognition requires RRM extensions	RESULTS
4	16	RNA affinity	evidence	The RNA affinity of the minimal U2AF651,2 domain comprising the core RRM1–RRM2 folds (U2AF651,2, residues 148–336) is relatively weak compared with full-length U2AF65 (Fig. 1a,b; Supplementary Fig. 1).	RESULTS
24	31	minimal	protein_state	The RNA affinity of the minimal U2AF651,2 domain comprising the core RRM1–RRM2 folds (U2AF651,2, residues 148–336) is relatively weak compared with full-length U2AF65 (Fig. 1a,b; Supplementary Fig. 1).	RESULTS
32	41	U2AF651,2	mutant	The RNA affinity of the minimal U2AF651,2 domain comprising the core RRM1–RRM2 folds (U2AF651,2, residues 148–336) is relatively weak compared with full-length U2AF65 (Fig. 1a,b; Supplementary Fig. 1).	RESULTS
64	68	core	protein_state	The RNA affinity of the minimal U2AF651,2 domain comprising the core RRM1–RRM2 folds (U2AF651,2, residues 148–336) is relatively weak compared with full-length U2AF65 (Fig. 1a,b; Supplementary Fig. 1).	RESULTS
69	73	RRM1	structure_element	The RNA affinity of the minimal U2AF651,2 domain comprising the core RRM1–RRM2 folds (U2AF651,2, residues 148–336) is relatively weak compared with full-length U2AF65 (Fig. 1a,b; Supplementary Fig. 1).	RESULTS
74	78	RRM2	structure_element	The RNA affinity of the minimal U2AF651,2 domain comprising the core RRM1–RRM2 folds (U2AF651,2, residues 148–336) is relatively weak compared with full-length U2AF65 (Fig. 1a,b; Supplementary Fig. 1).	RESULTS
79	84	folds	structure_element	The RNA affinity of the minimal U2AF651,2 domain comprising the core RRM1–RRM2 folds (U2AF651,2, residues 148–336) is relatively weak compared with full-length U2AF65 (Fig. 1a,b; Supplementary Fig. 1).	RESULTS
86	95	U2AF651,2	mutant	The RNA affinity of the minimal U2AF651,2 domain comprising the core RRM1–RRM2 folds (U2AF651,2, residues 148–336) is relatively weak compared with full-length U2AF65 (Fig. 1a,b; Supplementary Fig. 1).	RESULTS
106	113	148–336	residue_range	The RNA affinity of the minimal U2AF651,2 domain comprising the core RRM1–RRM2 folds (U2AF651,2, residues 148–336) is relatively weak compared with full-length U2AF65 (Fig. 1a,b; Supplementary Fig. 1).	RESULTS
148	159	full-length	protein_state	The RNA affinity of the minimal U2AF651,2 domain comprising the core RRM1–RRM2 folds (U2AF651,2, residues 148–336) is relatively weak compared with full-length U2AF65 (Fig. 1a,b; Supplementary Fig. 1).	RESULTS
160	166	U2AF65	protein	The RNA affinity of the minimal U2AF651,2 domain comprising the core RRM1–RRM2 folds (U2AF651,2, residues 148–336) is relatively weak compared with full-length U2AF65 (Fig. 1a,b; Supplementary Fig. 1).	RESULTS
52	58	U2AF65	protein	Historically, this difference was attributed to the U2AF65 arginine–serine rich domain, which contacts pre-mRNA–U2 snRNA duplexes outside of the Py tract.	RESULTS
59	86	arginine–serine rich domain	structure_element	Historically, this difference was attributed to the U2AF65 arginine–serine rich domain, which contacts pre-mRNA–U2 snRNA duplexes outside of the Py tract.	RESULTS
103	129	pre-mRNA–U2 snRNA duplexes	complex_assembly	Historically, this difference was attributed to the U2AF65 arginine–serine rich domain, which contacts pre-mRNA–U2 snRNA duplexes outside of the Py tract.	RESULTS
145	153	Py tract	chemical	Historically, this difference was attributed to the U2AF65 arginine–serine rich domain, which contacts pre-mRNA–U2 snRNA duplexes outside of the Py tract.	RESULTS
20	40	RNA-binding affinity	evidence	We noticed that the RNA-binding affinity of the U2AF651,2 domain was greatly enhanced by the addition of seven and six residues at the respective N and C termini of the minimal RRM1 and RRM2 (U2AF651,2L, residues 141–342; Fig. 1a).	RESULTS
48	57	U2AF651,2	mutant	We noticed that the RNA-binding affinity of the U2AF651,2 domain was greatly enhanced by the addition of seven and six residues at the respective N and C termini of the minimal RRM1 and RRM2 (U2AF651,2L, residues 141–342; Fig. 1a).	RESULTS
93	127	addition of seven and six residues	experimental_method	We noticed that the RNA-binding affinity of the U2AF651,2 domain was greatly enhanced by the addition of seven and six residues at the respective N and C termini of the minimal RRM1 and RRM2 (U2AF651,2L, residues 141–342; Fig. 1a).	RESULTS
169	176	minimal	protein_state	We noticed that the RNA-binding affinity of the U2AF651,2 domain was greatly enhanced by the addition of seven and six residues at the respective N and C termini of the minimal RRM1 and RRM2 (U2AF651,2L, residues 141–342; Fig. 1a).	RESULTS
177	181	RRM1	structure_element	We noticed that the RNA-binding affinity of the U2AF651,2 domain was greatly enhanced by the addition of seven and six residues at the respective N and C termini of the minimal RRM1 and RRM2 (U2AF651,2L, residues 141–342; Fig. 1a).	RESULTS
186	190	RRM2	structure_element	We noticed that the RNA-binding affinity of the U2AF651,2 domain was greatly enhanced by the addition of seven and six residues at the respective N and C termini of the minimal RRM1 and RRM2 (U2AF651,2L, residues 141–342; Fig. 1a).	RESULTS
192	202	U2AF651,2L	mutant	We noticed that the RNA-binding affinity of the U2AF651,2 domain was greatly enhanced by the addition of seven and six residues at the respective N and C termini of the minimal RRM1 and RRM2 (U2AF651,2L, residues 141–342; Fig. 1a).	RESULTS
213	220	141–342	residue_range	We noticed that the RNA-binding affinity of the U2AF651,2 domain was greatly enhanced by the addition of seven and six residues at the respective N and C termini of the minimal RRM1 and RRM2 (U2AF651,2L, residues 141–342; Fig. 1a).	RESULTS
5	34	fluorescence anisotropy assay	experimental_method	In a fluorescence anisotropy assay for binding a representative Py tract derived from the well-characterized splice site of the adenovirus major late promoter (AdML), the RNA affinity of U2AF651,2L increased by 100-fold relative to U2AF651,2 to comparable levels as full-length U2AF65 (Fig. 1b; Supplementary Fig. 1a–d).	RESULTS
64	72	Py tract	chemical	In a fluorescence anisotropy assay for binding a representative Py tract derived from the well-characterized splice site of the adenovirus major late promoter (AdML), the RNA affinity of U2AF651,2L increased by 100-fold relative to U2AF651,2 to comparable levels as full-length U2AF65 (Fig. 1b; Supplementary Fig. 1a–d).	RESULTS
109	120	splice site	site	In a fluorescence anisotropy assay for binding a representative Py tract derived from the well-characterized splice site of the adenovirus major late promoter (AdML), the RNA affinity of U2AF651,2L increased by 100-fold relative to U2AF651,2 to comparable levels as full-length U2AF65 (Fig. 1b; Supplementary Fig. 1a–d).	RESULTS
128	158	adenovirus major late promoter	gene	In a fluorescence anisotropy assay for binding a representative Py tract derived from the well-characterized splice site of the adenovirus major late promoter (AdML), the RNA affinity of U2AF651,2L increased by 100-fold relative to U2AF651,2 to comparable levels as full-length U2AF65 (Fig. 1b; Supplementary Fig. 1a–d).	RESULTS
160	164	AdML	gene	In a fluorescence anisotropy assay for binding a representative Py tract derived from the well-characterized splice site of the adenovirus major late promoter (AdML), the RNA affinity of U2AF651,2L increased by 100-fold relative to U2AF651,2 to comparable levels as full-length U2AF65 (Fig. 1b; Supplementary Fig. 1a–d).	RESULTS
171	183	RNA affinity	evidence	In a fluorescence anisotropy assay for binding a representative Py tract derived from the well-characterized splice site of the adenovirus major late promoter (AdML), the RNA affinity of U2AF651,2L increased by 100-fold relative to U2AF651,2 to comparable levels as full-length U2AF65 (Fig. 1b; Supplementary Fig. 1a–d).	RESULTS
187	197	U2AF651,2L	mutant	In a fluorescence anisotropy assay for binding a representative Py tract derived from the well-characterized splice site of the adenovirus major late promoter (AdML), the RNA affinity of U2AF651,2L increased by 100-fold relative to U2AF651,2 to comparable levels as full-length U2AF65 (Fig. 1b; Supplementary Fig. 1a–d).	RESULTS
232	241	U2AF651,2	mutant	In a fluorescence anisotropy assay for binding a representative Py tract derived from the well-characterized splice site of the adenovirus major late promoter (AdML), the RNA affinity of U2AF651,2L increased by 100-fold relative to U2AF651,2 to comparable levels as full-length U2AF65 (Fig. 1b; Supplementary Fig. 1a–d).	RESULTS
266	277	full-length	protein_state	In a fluorescence anisotropy assay for binding a representative Py tract derived from the well-characterized splice site of the adenovirus major late promoter (AdML), the RNA affinity of U2AF651,2L increased by 100-fold relative to U2AF651,2 to comparable levels as full-length U2AF65 (Fig. 1b; Supplementary Fig. 1a–d).	RESULTS
278	284	U2AF65	protein	In a fluorescence anisotropy assay for binding a representative Py tract derived from the well-characterized splice site of the adenovirus major late promoter (AdML), the RNA affinity of U2AF651,2L increased by 100-fold relative to U2AF651,2 to comparable levels as full-length U2AF65 (Fig. 1b; Supplementary Fig. 1a–d).	RESULTS
15	25	U2AF651,2L	mutant	Likewise, both U2AF651,2L and full-length U2AF65 showed similar sequence specificity for U-rich stretches in the 5′-region of the Py tract and promiscuity for C-rich regions in the 3′-region (Fig. 1c, Supplementary Fig. 1e–h).	RESULTS
30	41	full-length	protein_state	Likewise, both U2AF651,2L and full-length U2AF65 showed similar sequence specificity for U-rich stretches in the 5′-region of the Py tract and promiscuity for C-rich regions in the 3′-region (Fig. 1c, Supplementary Fig. 1e–h).	RESULTS
42	48	U2AF65	protein	Likewise, both U2AF651,2L and full-length U2AF65 showed similar sequence specificity for U-rich stretches in the 5′-region of the Py tract and promiscuity for C-rich regions in the 3′-region (Fig. 1c, Supplementary Fig. 1e–h).	RESULTS
64	84	sequence specificity	evidence	Likewise, both U2AF651,2L and full-length U2AF65 showed similar sequence specificity for U-rich stretches in the 5′-region of the Py tract and promiscuity for C-rich regions in the 3′-region (Fig. 1c, Supplementary Fig. 1e–h).	RESULTS
89	105	U-rich stretches	structure_element	Likewise, both U2AF651,2L and full-length U2AF65 showed similar sequence specificity for U-rich stretches in the 5′-region of the Py tract and promiscuity for C-rich regions in the 3′-region (Fig. 1c, Supplementary Fig. 1e–h).	RESULTS
113	122	5′-region	site	Likewise, both U2AF651,2L and full-length U2AF65 showed similar sequence specificity for U-rich stretches in the 5′-region of the Py tract and promiscuity for C-rich regions in the 3′-region (Fig. 1c, Supplementary Fig. 1e–h).	RESULTS
130	138	Py tract	chemical	Likewise, both U2AF651,2L and full-length U2AF65 showed similar sequence specificity for U-rich stretches in the 5′-region of the Py tract and promiscuity for C-rich regions in the 3′-region (Fig. 1c, Supplementary Fig. 1e–h).	RESULTS
159	173	C-rich regions	structure_element	Likewise, both U2AF651,2L and full-length U2AF65 showed similar sequence specificity for U-rich stretches in the 5′-region of the Py tract and promiscuity for C-rich regions in the 3′-region (Fig. 1c, Supplementary Fig. 1e–h).	RESULTS
181	190	3′-region	site	Likewise, both U2AF651,2L and full-length U2AF65 showed similar sequence specificity for U-rich stretches in the 5′-region of the Py tract and promiscuity for C-rich regions in the 3′-region (Fig. 1c, Supplementary Fig. 1e–h).	RESULTS
0	12	U2AF65-bound	protein_state	U2AF65-bound Py tract comprises nine contiguous nucleotides	RESULTS
13	21	Py tract	chemical	U2AF65-bound Py tract comprises nine contiguous nucleotides	RESULTS
37	47	contiguous	structure_element	U2AF65-bound Py tract comprises nine contiguous nucleotides	RESULTS
48	59	nucleotides	chemical	U2AF65-bound Py tract comprises nine contiguous nucleotides	RESULTS
48	54	U2AF65	protein	To investigate the structural basis for cognate U2AF65 recognition of a contiguous Py tract, we determined four crystal structures of U2AF651,2L bound to Py-tract oligonucleotides (Fig. 2a; Table 1).	RESULTS
72	82	contiguous	structure_element	To investigate the structural basis for cognate U2AF65 recognition of a contiguous Py tract, we determined four crystal structures of U2AF651,2L bound to Py-tract oligonucleotides (Fig. 2a; Table 1).	RESULTS
83	91	Py tract	chemical	To investigate the structural basis for cognate U2AF65 recognition of a contiguous Py tract, we determined four crystal structures of U2AF651,2L bound to Py-tract oligonucleotides (Fig. 2a; Table 1).	RESULTS
96	106	determined	experimental_method	To investigate the structural basis for cognate U2AF65 recognition of a contiguous Py tract, we determined four crystal structures of U2AF651,2L bound to Py-tract oligonucleotides (Fig. 2a; Table 1).	RESULTS
112	130	crystal structures	evidence	To investigate the structural basis for cognate U2AF65 recognition of a contiguous Py tract, we determined four crystal structures of U2AF651,2L bound to Py-tract oligonucleotides (Fig. 2a; Table 1).	RESULTS
134	144	U2AF651,2L	mutant	To investigate the structural basis for cognate U2AF65 recognition of a contiguous Py tract, we determined four crystal structures of U2AF651,2L bound to Py-tract oligonucleotides (Fig. 2a; Table 1).	RESULTS
145	153	bound to	protein_state	To investigate the structural basis for cognate U2AF65 recognition of a contiguous Py tract, we determined four crystal structures of U2AF651,2L bound to Py-tract oligonucleotides (Fig. 2a; Table 1).	RESULTS
154	179	Py-tract oligonucleotides	chemical	To investigate the structural basis for cognate U2AF65 recognition of a contiguous Py tract, we determined four crystal structures of U2AF651,2L bound to Py-tract oligonucleotides (Fig. 2a; Table 1).	RESULTS
3	28	sequential boot strapping	experimental_method	By sequential boot strapping (Methods), we optimized the oligonucleotide length, the position of a Br-dU, and the identity of the terminal nucleotide (rU, dU and rC) to achieve full views of U2AF651,2L bound to contiguous Py tracts at up to 1.5 Å resolution.	RESULTS
57	72	oligonucleotide	chemical	By sequential boot strapping (Methods), we optimized the oligonucleotide length, the position of a Br-dU, and the identity of the terminal nucleotide (rU, dU and rC) to achieve full views of U2AF651,2L bound to contiguous Py tracts at up to 1.5 Å resolution.	RESULTS
99	104	Br-dU	chemical	By sequential boot strapping (Methods), we optimized the oligonucleotide length, the position of a Br-dU, and the identity of the terminal nucleotide (rU, dU and rC) to achieve full views of U2AF651,2L bound to contiguous Py tracts at up to 1.5 Å resolution.	RESULTS
139	149	nucleotide	chemical	By sequential boot strapping (Methods), we optimized the oligonucleotide length, the position of a Br-dU, and the identity of the terminal nucleotide (rU, dU and rC) to achieve full views of U2AF651,2L bound to contiguous Py tracts at up to 1.5 Å resolution.	RESULTS
151	153	rU	residue_name	By sequential boot strapping (Methods), we optimized the oligonucleotide length, the position of a Br-dU, and the identity of the terminal nucleotide (rU, dU and rC) to achieve full views of U2AF651,2L bound to contiguous Py tracts at up to 1.5 Å resolution.	RESULTS
155	157	dU	residue_name	By sequential boot strapping (Methods), we optimized the oligonucleotide length, the position of a Br-dU, and the identity of the terminal nucleotide (rU, dU and rC) to achieve full views of U2AF651,2L bound to contiguous Py tracts at up to 1.5 Å resolution.	RESULTS
162	164	rC	residue_name	By sequential boot strapping (Methods), we optimized the oligonucleotide length, the position of a Br-dU, and the identity of the terminal nucleotide (rU, dU and rC) to achieve full views of U2AF651,2L bound to contiguous Py tracts at up to 1.5 Å resolution.	RESULTS
191	201	U2AF651,2L	mutant	By sequential boot strapping (Methods), we optimized the oligonucleotide length, the position of a Br-dU, and the identity of the terminal nucleotide (rU, dU and rC) to achieve full views of U2AF651,2L bound to contiguous Py tracts at up to 1.5 Å resolution.	RESULTS
202	210	bound to	protein_state	By sequential boot strapping (Methods), we optimized the oligonucleotide length, the position of a Br-dU, and the identity of the terminal nucleotide (rU, dU and rC) to achieve full views of U2AF651,2L bound to contiguous Py tracts at up to 1.5 Å resolution.	RESULTS
211	221	contiguous	structure_element	By sequential boot strapping (Methods), we optimized the oligonucleotide length, the position of a Br-dU, and the identity of the terminal nucleotide (rU, dU and rC) to achieve full views of U2AF651,2L bound to contiguous Py tracts at up to 1.5 Å resolution.	RESULTS
222	231	Py tracts	chemical	By sequential boot strapping (Methods), we optimized the oligonucleotide length, the position of a Br-dU, and the identity of the terminal nucleotide (rU, dU and rC) to achieve full views of U2AF651,2L bound to contiguous Py tracts at up to 1.5 Å resolution.	RESULTS
16	31	oligonucleotide	chemical	The protein and oligonucleotide conformations are nearly identical among the four new U2AF651,2L structures (Supplementary Fig. 2a).	RESULTS
86	96	U2AF651,2L	mutant	The protein and oligonucleotide conformations are nearly identical among the four new U2AF651,2L structures (Supplementary Fig. 2a).	RESULTS
97	107	structures	evidence	The protein and oligonucleotide conformations are nearly identical among the four new U2AF651,2L structures (Supplementary Fig. 2a).	RESULTS
4	14	U2AF651,2L	mutant	The U2AF651,2L RRM1 and RRM2 associate with the Py tract in a parallel, side-by-side arrangement (shown for representative structure iv in Fig. 2b,c; Supplementary Movie 1).	RESULTS
15	19	RRM1	structure_element	The U2AF651,2L RRM1 and RRM2 associate with the Py tract in a parallel, side-by-side arrangement (shown for representative structure iv in Fig. 2b,c; Supplementary Movie 1).	RESULTS
24	28	RRM2	structure_element	The U2AF651,2L RRM1 and RRM2 associate with the Py tract in a parallel, side-by-side arrangement (shown for representative structure iv in Fig. 2b,c; Supplementary Movie 1).	RESULTS
48	56	Py tract	chemical	The U2AF651,2L RRM1 and RRM2 associate with the Py tract in a parallel, side-by-side arrangement (shown for representative structure iv in Fig. 2b,c; Supplementary Movie 1).	RESULTS
62	70	parallel	protein_state	The U2AF651,2L RRM1 and RRM2 associate with the Py tract in a parallel, side-by-side arrangement (shown for representative structure iv in Fig. 2b,c; Supplementary Movie 1).	RESULTS
72	84	side-by-side	protein_state	The U2AF651,2L RRM1 and RRM2 associate with the Py tract in a parallel, side-by-side arrangement (shown for representative structure iv in Fig. 2b,c; Supplementary Movie 1).	RESULTS
3	24	extended conformation	protein_state	An extended conformation of the U2AF65 inter-RRM linker traverses across the α-helical surface of RRM1 and the central β-strands of RRM2 and is well defined in the electron density (Fig. 2b).	RESULTS
32	38	U2AF65	protein	An extended conformation of the U2AF65 inter-RRM linker traverses across the α-helical surface of RRM1 and the central β-strands of RRM2 and is well defined in the electron density (Fig. 2b).	RESULTS
39	55	inter-RRM linker	structure_element	An extended conformation of the U2AF65 inter-RRM linker traverses across the α-helical surface of RRM1 and the central β-strands of RRM2 and is well defined in the electron density (Fig. 2b).	RESULTS
77	94	α-helical surface	structure_element	An extended conformation of the U2AF65 inter-RRM linker traverses across the α-helical surface of RRM1 and the central β-strands of RRM2 and is well defined in the electron density (Fig. 2b).	RESULTS
98	102	RRM1	structure_element	An extended conformation of the U2AF65 inter-RRM linker traverses across the α-helical surface of RRM1 and the central β-strands of RRM2 and is well defined in the electron density (Fig. 2b).	RESULTS
119	128	β-strands	structure_element	An extended conformation of the U2AF65 inter-RRM linker traverses across the α-helical surface of RRM1 and the central β-strands of RRM2 and is well defined in the electron density (Fig. 2b).	RESULTS
132	136	RRM2	structure_element	An extended conformation of the U2AF65 inter-RRM linker traverses across the α-helical surface of RRM1 and the central β-strands of RRM2 and is well defined in the electron density (Fig. 2b).	RESULTS
164	180	electron density	evidence	An extended conformation of the U2AF65 inter-RRM linker traverses across the α-helical surface of RRM1 and the central β-strands of RRM2 and is well defined in the electron density (Fig. 2b).	RESULTS
4	14	extensions	structure_element	The extensions at the N terminus of RRM1 and C terminus of RRM2 adopt well-ordered α-helices.	RESULTS
36	40	RRM1	structure_element	The extensions at the N terminus of RRM1 and C terminus of RRM2 adopt well-ordered α-helices.	RESULTS
59	63	RRM2	structure_element	The extensions at the N terminus of RRM1 and C terminus of RRM2 adopt well-ordered α-helices.	RESULTS
83	92	α-helices	structure_element	The extensions at the N terminus of RRM1 and C terminus of RRM2 adopt well-ordered α-helices.	RESULTS
5	9	RRM1	structure_element	Both RRM1/RRM2 extensions and the inter-RRM linker of U2AF651,2L directly recognize the bound oligonucleotide.	RESULTS
10	14	RRM2	structure_element	Both RRM1/RRM2 extensions and the inter-RRM linker of U2AF651,2L directly recognize the bound oligonucleotide.	RESULTS
15	25	extensions	structure_element	Both RRM1/RRM2 extensions and the inter-RRM linker of U2AF651,2L directly recognize the bound oligonucleotide.	RESULTS
34	50	inter-RRM linker	structure_element	Both RRM1/RRM2 extensions and the inter-RRM linker of U2AF651,2L directly recognize the bound oligonucleotide.	RESULTS
54	64	U2AF651,2L	mutant	Both RRM1/RRM2 extensions and the inter-RRM linker of U2AF651,2L directly recognize the bound oligonucleotide.	RESULTS
88	93	bound	protein_state	Both RRM1/RRM2 extensions and the inter-RRM linker of U2AF651,2L directly recognize the bound oligonucleotide.	RESULTS
94	109	oligonucleotide	chemical	Both RRM1/RRM2 extensions and the inter-RRM linker of U2AF651,2L directly recognize the bound oligonucleotide.	RESULTS
42	52	U2AF651,2L	mutant	We compare the global conformation of the U2AF651,2L structures with the prior dU2AF651,2 crystal structure and U2AF651,2 NMR structure in the Supplementary Discussion and Supplementary Fig. 2.	RESULTS
53	63	structures	evidence	We compare the global conformation of the U2AF651,2L structures with the prior dU2AF651,2 crystal structure and U2AF651,2 NMR structure in the Supplementary Discussion and Supplementary Fig. 2.	RESULTS
79	89	dU2AF651,2	mutant	We compare the global conformation of the U2AF651,2L structures with the prior dU2AF651,2 crystal structure and U2AF651,2 NMR structure in the Supplementary Discussion and Supplementary Fig. 2.	RESULTS
90	107	crystal structure	evidence	We compare the global conformation of the U2AF651,2L structures with the prior dU2AF651,2 crystal structure and U2AF651,2 NMR structure in the Supplementary Discussion and Supplementary Fig. 2.	RESULTS
112	121	U2AF651,2	mutant	We compare the global conformation of the U2AF651,2L structures with the prior dU2AF651,2 crystal structure and U2AF651,2 NMR structure in the Supplementary Discussion and Supplementary Fig. 2.	RESULTS
122	125	NMR	experimental_method	We compare the global conformation of the U2AF651,2L structures with the prior dU2AF651,2 crystal structure and U2AF651,2 NMR structure in the Supplementary Discussion and Supplementary Fig. 2.	RESULTS
126	135	structure	evidence	We compare the global conformation of the U2AF651,2L structures with the prior dU2AF651,2 crystal structure and U2AF651,2 NMR structure in the Supplementary Discussion and Supplementary Fig. 2.	RESULTS
22	42	U2AF65-binding sites	site	The discovery of nine U2AF65-binding sites for contiguous Py-tract nucleotides was unexpected.	RESULTS
47	57	contiguous	structure_element	The discovery of nine U2AF65-binding sites for contiguous Py-tract nucleotides was unexpected.	RESULTS
58	78	Py-tract nucleotides	chemical	The discovery of nine U2AF65-binding sites for contiguous Py-tract nucleotides was unexpected.	RESULTS
9	19	dU2AF651,2	mutant	Based on dU2AF651,2 structures, we originally hypothesized that the U2AF65 RRMs would bind the minimal seven nucleotides observed in these structures.	RESULTS
20	30	structures	evidence	Based on dU2AF651,2 structures, we originally hypothesized that the U2AF65 RRMs would bind the minimal seven nucleotides observed in these structures.	RESULTS
68	74	U2AF65	protein	Based on dU2AF651,2 structures, we originally hypothesized that the U2AF65 RRMs would bind the minimal seven nucleotides observed in these structures.	RESULTS
75	79	RRMs	structure_element	Based on dU2AF651,2 structures, we originally hypothesized that the U2AF65 RRMs would bind the minimal seven nucleotides observed in these structures.	RESULTS
95	102	minimal	protein_state	Based on dU2AF651,2 structures, we originally hypothesized that the U2AF65 RRMs would bind the minimal seven nucleotides observed in these structures.	RESULTS
109	120	nucleotides	chemical	Based on dU2AF651,2 structures, we originally hypothesized that the U2AF65 RRMs would bind the minimal seven nucleotides observed in these structures.	RESULTS
139	149	structures	evidence	Based on dU2AF651,2 structures, we originally hypothesized that the U2AF65 RRMs would bind the minimal seven nucleotides observed in these structures.	RESULTS
18	32	RRM2 extension	structure_element	Surprisingly, the RRM2 extension/inter-RRM linker contribute new central nucleotide-binding sites near the RRM1/RRM2 junction and the RRM1 extension recognizes the 3′-terminal nucleotide (Fig. 2c; Supplementary Movie 1).	RESULTS
33	49	inter-RRM linker	structure_element	Surprisingly, the RRM2 extension/inter-RRM linker contribute new central nucleotide-binding sites near the RRM1/RRM2 junction and the RRM1 extension recognizes the 3′-terminal nucleotide (Fig. 2c; Supplementary Movie 1).	RESULTS
73	97	nucleotide-binding sites	site	Surprisingly, the RRM2 extension/inter-RRM linker contribute new central nucleotide-binding sites near the RRM1/RRM2 junction and the RRM1 extension recognizes the 3′-terminal nucleotide (Fig. 2c; Supplementary Movie 1).	RESULTS
107	125	RRM1/RRM2 junction	site	Surprisingly, the RRM2 extension/inter-RRM linker contribute new central nucleotide-binding sites near the RRM1/RRM2 junction and the RRM1 extension recognizes the 3′-terminal nucleotide (Fig. 2c; Supplementary Movie 1).	RESULTS
134	148	RRM1 extension	structure_element	Surprisingly, the RRM2 extension/inter-RRM linker contribute new central nucleotide-binding sites near the RRM1/RRM2 junction and the RRM1 extension recognizes the 3′-terminal nucleotide (Fig. 2c; Supplementary Movie 1).	RESULTS
176	186	nucleotide	chemical	Surprisingly, the RRM2 extension/inter-RRM linker contribute new central nucleotide-binding sites near the RRM1/RRM2 junction and the RRM1 extension recognizes the 3′-terminal nucleotide (Fig. 2c; Supplementary Movie 1).	RESULTS
4	14	U2AF651,2L	mutant	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
15	25	structures	evidence	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
39	45	ribose	chemical	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
47	48	r	chemical	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
50	61	nucleotides	chemical	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
76	89	binding sites	site	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
101	108	seventh	residue_number	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
113	119	eighth	residue_number	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
120	130	deoxy-(d)U	chemical	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
191	200	RNA-bound	protein_state	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
201	211	dU2AF651,2	mutant	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
212	221	structure	evidence	The U2AF651,2L structures characterize ribose (r) nucleotides at all of the binding sites except the seventh and eighth deoxy-(d)U, which are likely to lack 2′-hydroxyl contacts based on the RNA-bound dU2AF651,2 structure.	RESULTS
31	66	U2AF651,2L-nucleotide-binding sites	site	Qualitatively, a subset of the U2AF651,2L-nucleotide-binding sites (sites 1–3 and 7–9) share similar locations to those of the dU2AF651,2 structures (Supplementary Figs 2c,d and 3).	RESULTS
68	77	sites 1–3	site	Qualitatively, a subset of the U2AF651,2L-nucleotide-binding sites (sites 1–3 and 7–9) share similar locations to those of the dU2AF651,2 structures (Supplementary Figs 2c,d and 3).	RESULTS
82	85	7–9	site	Qualitatively, a subset of the U2AF651,2L-nucleotide-binding sites (sites 1–3 and 7–9) share similar locations to those of the dU2AF651,2 structures (Supplementary Figs 2c,d and 3).	RESULTS
127	137	dU2AF651,2	mutant	Qualitatively, a subset of the U2AF651,2L-nucleotide-binding sites (sites 1–3 and 7–9) share similar locations to those of the dU2AF651,2 structures (Supplementary Figs 2c,d and 3).	RESULTS
138	148	structures	evidence	Qualitatively, a subset of the U2AF651,2L-nucleotide-binding sites (sites 1–3 and 7–9) share similar locations to those of the dU2AF651,2 structures (Supplementary Figs 2c,d and 3).	RESULTS
14	24	U2AF651,2L	mutant	Yet, only the U2AF651,2L interactions at sites 1 and 7 are nearly identical to those of the dU2AF651,2 structures (Supplementary Fig. 3a,f).	RESULTS
41	54	sites 1 and 7	site	Yet, only the U2AF651,2L interactions at sites 1 and 7 are nearly identical to those of the dU2AF651,2 structures (Supplementary Fig. 3a,f).	RESULTS
92	102	dU2AF651,2	mutant	Yet, only the U2AF651,2L interactions at sites 1 and 7 are nearly identical to those of the dU2AF651,2 structures (Supplementary Fig. 3a,f).	RESULTS
103	113	structures	evidence	Yet, only the U2AF651,2L interactions at sites 1 and 7 are nearly identical to those of the dU2AF651,2 structures (Supplementary Fig. 3a,f).	RESULTS
53	63	U2AF651,2L	mutant	In striking departures from prior partial views, the U2AF651,2L structures reveal three unanticipated nucleotide-binding sites at the centre of the Py tract, as well as numerous new interactions that underlie cognate recognition of the Py tract (Fig. 3a–h).	RESULTS
64	74	structures	evidence	In striking departures from prior partial views, the U2AF651,2L structures reveal three unanticipated nucleotide-binding sites at the centre of the Py tract, as well as numerous new interactions that underlie cognate recognition of the Py tract (Fig. 3a–h).	RESULTS
102	126	nucleotide-binding sites	site	In striking departures from prior partial views, the U2AF651,2L structures reveal three unanticipated nucleotide-binding sites at the centre of the Py tract, as well as numerous new interactions that underlie cognate recognition of the Py tract (Fig. 3a–h).	RESULTS
148	156	Py tract	chemical	In striking departures from prior partial views, the U2AF651,2L structures reveal three unanticipated nucleotide-binding sites at the centre of the Py tract, as well as numerous new interactions that underlie cognate recognition of the Py tract (Fig. 3a–h).	RESULTS
236	244	Py tract	chemical	In striking departures from prior partial views, the U2AF651,2L structures reveal three unanticipated nucleotide-binding sites at the centre of the Py tract, as well as numerous new interactions that underlie cognate recognition of the Py tract (Fig. 3a–h).	RESULTS
0	6	U2AF65	protein	U2AF65 inter-RRM linker interacts with the Py tract	RESULTS
7	23	inter-RRM linker	structure_element	U2AF65 inter-RRM linker interacts with the Py tract	RESULTS
43	51	Py tract	chemical	U2AF65 inter-RRM linker interacts with the Py tract	RESULTS
4	14	U2AF651,2L	mutant	The U2AF651,2L RRM2, the inter-RRM linker and RRM1 concomitantly recognize the three central nucleotides of the Py tract, which are likely to coordinate the conformational arrangement of these disparate portions of the protein.	RESULTS
15	19	RRM2	structure_element	The U2AF651,2L RRM2, the inter-RRM linker and RRM1 concomitantly recognize the three central nucleotides of the Py tract, which are likely to coordinate the conformational arrangement of these disparate portions of the protein.	RESULTS
25	41	inter-RRM linker	structure_element	The U2AF651,2L RRM2, the inter-RRM linker and RRM1 concomitantly recognize the three central nucleotides of the Py tract, which are likely to coordinate the conformational arrangement of these disparate portions of the protein.	RESULTS
46	50	RRM1	structure_element	The U2AF651,2L RRM2, the inter-RRM linker and RRM1 concomitantly recognize the three central nucleotides of the Py tract, which are likely to coordinate the conformational arrangement of these disparate portions of the protein.	RESULTS
93	104	nucleotides	chemical	The U2AF651,2L RRM2, the inter-RRM linker and RRM1 concomitantly recognize the three central nucleotides of the Py tract, which are likely to coordinate the conformational arrangement of these disparate portions of the protein.	RESULTS
112	120	Py tract	chemical	The U2AF651,2L RRM2, the inter-RRM linker and RRM1 concomitantly recognize the three central nucleotides of the Py tract, which are likely to coordinate the conformational arrangement of these disparate portions of the protein.	RESULTS
16	33	C-terminal region	structure_element	Residues in the C-terminal region of the U2AF65 inter-RRM linker comprise a centrally located binding site for the fifth nucleotide on the RRM2 surface and abutting the RRM1/RRM2 interface (Fig. 3d).	RESULTS
41	47	U2AF65	protein	Residues in the C-terminal region of the U2AF65 inter-RRM linker comprise a centrally located binding site for the fifth nucleotide on the RRM2 surface and abutting the RRM1/RRM2 interface (Fig. 3d).	RESULTS
48	64	inter-RRM linker	structure_element	Residues in the C-terminal region of the U2AF65 inter-RRM linker comprise a centrally located binding site for the fifth nucleotide on the RRM2 surface and abutting the RRM1/RRM2 interface (Fig. 3d).	RESULTS
94	106	binding site	site	Residues in the C-terminal region of the U2AF65 inter-RRM linker comprise a centrally located binding site for the fifth nucleotide on the RRM2 surface and abutting the RRM1/RRM2 interface (Fig. 3d).	RESULTS
115	120	fifth	residue_number	Residues in the C-terminal region of the U2AF65 inter-RRM linker comprise a centrally located binding site for the fifth nucleotide on the RRM2 surface and abutting the RRM1/RRM2 interface (Fig. 3d).	RESULTS
121	131	nucleotide	chemical	Residues in the C-terminal region of the U2AF65 inter-RRM linker comprise a centrally located binding site for the fifth nucleotide on the RRM2 surface and abutting the RRM1/RRM2 interface (Fig. 3d).	RESULTS
139	151	RRM2 surface	site	Residues in the C-terminal region of the U2AF65 inter-RRM linker comprise a centrally located binding site for the fifth nucleotide on the RRM2 surface and abutting the RRM1/RRM2 interface (Fig. 3d).	RESULTS
169	188	RRM1/RRM2 interface	site	Residues in the C-terminal region of the U2AF65 inter-RRM linker comprise a centrally located binding site for the fifth nucleotide on the RRM2 surface and abutting the RRM1/RRM2 interface (Fig. 3d).	RESULTS
26	32	linker	structure_element	The backbone amide of the linker V254 and the carbonyl of T252 engage in hydrogen bonds with the rU5-O4 and -N3H atoms.	RESULTS
33	37	V254	residue_name_number	The backbone amide of the linker V254 and the carbonyl of T252 engage in hydrogen bonds with the rU5-O4 and -N3H atoms.	RESULTS
58	62	T252	residue_name_number	The backbone amide of the linker V254 and the carbonyl of T252 engage in hydrogen bonds with the rU5-O4 and -N3H atoms.	RESULTS
73	87	hydrogen bonds	bond_interaction	The backbone amide of the linker V254 and the carbonyl of T252 engage in hydrogen bonds with the rU5-O4 and -N3H atoms.	RESULTS
97	100	rU5	residue_name_number	The backbone amide of the linker V254 and the carbonyl of T252 engage in hydrogen bonds with the rU5-O4 and -N3H atoms.	RESULTS
18	26	β-strand	structure_element	In the C-terminal β-strand of RRM1, the side chains of K225 and R227 donate additional hydrogen bonds to the rU5-O2 lone pair electrons.	RESULTS
30	34	RRM1	structure_element	In the C-terminal β-strand of RRM1, the side chains of K225 and R227 donate additional hydrogen bonds to the rU5-O2 lone pair electrons.	RESULTS
55	59	K225	residue_name_number	In the C-terminal β-strand of RRM1, the side chains of K225 and R227 donate additional hydrogen bonds to the rU5-O2 lone pair electrons.	RESULTS
64	68	R227	residue_name_number	In the C-terminal β-strand of RRM1, the side chains of K225 and R227 donate additional hydrogen bonds to the rU5-O2 lone pair electrons.	RESULTS
87	101	hydrogen bonds	bond_interaction	In the C-terminal β-strand of RRM1, the side chains of K225 and R227 donate additional hydrogen bonds to the rU5-O2 lone pair electrons.	RESULTS
109	112	rU5	residue_name_number	In the C-terminal β-strand of RRM1, the side chains of K225 and R227 donate additional hydrogen bonds to the rU5-O2 lone pair electrons.	RESULTS
4	21	C-terminal region	structure_element	The C-terminal region of the inter-RRM linker also participates in the preceding rU4-binding site, where the V254 backbone carbonyl and D256 carboxylate position the K260 side chain to hydrogen bond with the rU4-O4 (Fig. 3c).	RESULTS
29	45	inter-RRM linker	structure_element	The C-terminal region of the inter-RRM linker also participates in the preceding rU4-binding site, where the V254 backbone carbonyl and D256 carboxylate position the K260 side chain to hydrogen bond with the rU4-O4 (Fig. 3c).	RESULTS
81	97	rU4-binding site	site	The C-terminal region of the inter-RRM linker also participates in the preceding rU4-binding site, where the V254 backbone carbonyl and D256 carboxylate position the K260 side chain to hydrogen bond with the rU4-O4 (Fig. 3c).	RESULTS
109	113	V254	residue_name_number	The C-terminal region of the inter-RRM linker also participates in the preceding rU4-binding site, where the V254 backbone carbonyl and D256 carboxylate position the K260 side chain to hydrogen bond with the rU4-O4 (Fig. 3c).	RESULTS
136	140	D256	residue_name_number	The C-terminal region of the inter-RRM linker also participates in the preceding rU4-binding site, where the V254 backbone carbonyl and D256 carboxylate position the K260 side chain to hydrogen bond with the rU4-O4 (Fig. 3c).	RESULTS
166	170	K260	residue_name_number	The C-terminal region of the inter-RRM linker also participates in the preceding rU4-binding site, where the V254 backbone carbonyl and D256 carboxylate position the K260 side chain to hydrogen bond with the rU4-O4 (Fig. 3c).	RESULTS
185	198	hydrogen bond	bond_interaction	The C-terminal region of the inter-RRM linker also participates in the preceding rU4-binding site, where the V254 backbone carbonyl and D256 carboxylate position the K260 side chain to hydrogen bond with the rU4-O4 (Fig. 3c).	RESULTS
208	211	rU4	residue_name_number	The C-terminal region of the inter-RRM linker also participates in the preceding rU4-binding site, where the V254 backbone carbonyl and D256 carboxylate position the K260 side chain to hydrogen bond with the rU4-O4 (Fig. 3c).	RESULTS
15	18	rU4	residue_name_number	Otherwise, the rU4 nucleotide packs against F304 in the signature ribonucleoprotein consensus motif (RNP)-2 of RRM2.	RESULTS
19	29	nucleotide	chemical	Otherwise, the rU4 nucleotide packs against F304 in the signature ribonucleoprotein consensus motif (RNP)-2 of RRM2.	RESULTS
44	48	F304	residue_name_number	Otherwise, the rU4 nucleotide packs against F304 in the signature ribonucleoprotein consensus motif (RNP)-2 of RRM2.	RESULTS
66	107	ribonucleoprotein consensus motif (RNP)-2	structure_element	Otherwise, the rU4 nucleotide packs against F304 in the signature ribonucleoprotein consensus motif (RNP)-2 of RRM2.	RESULTS
111	115	RRM2	structure_element	Otherwise, the rU4 nucleotide packs against F304 in the signature ribonucleoprotein consensus motif (RNP)-2 of RRM2.	RESULTS
36	41	fifth	residue_number	At the opposite side of the central fifth nucleotide, the sixth rU6 nucleotide is located at the inter-RRM1/RRM2 interface (Fig. 3e; Supplementary Movie 1).	RESULTS
42	52	nucleotide	chemical	At the opposite side of the central fifth nucleotide, the sixth rU6 nucleotide is located at the inter-RRM1/RRM2 interface (Fig. 3e; Supplementary Movie 1).	RESULTS
58	63	sixth	residue_number	At the opposite side of the central fifth nucleotide, the sixth rU6 nucleotide is located at the inter-RRM1/RRM2 interface (Fig. 3e; Supplementary Movie 1).	RESULTS
64	67	rU6	residue_name_number	At the opposite side of the central fifth nucleotide, the sixth rU6 nucleotide is located at the inter-RRM1/RRM2 interface (Fig. 3e; Supplementary Movie 1).	RESULTS
68	78	nucleotide	chemical	At the opposite side of the central fifth nucleotide, the sixth rU6 nucleotide is located at the inter-RRM1/RRM2 interface (Fig. 3e; Supplementary Movie 1).	RESULTS
97	122	inter-RRM1/RRM2 interface	site	At the opposite side of the central fifth nucleotide, the sixth rU6 nucleotide is located at the inter-RRM1/RRM2 interface (Fig. 3e; Supplementary Movie 1).	RESULTS
5	15	nucleotide	chemical	This nucleotide twists to face away from the U2AF65 linker and instead inserts the rU6-uracil into a sandwich between the β2/β3 loops of RRM1 and RRM2.	RESULTS
45	51	U2AF65	protein	This nucleotide twists to face away from the U2AF65 linker and instead inserts the rU6-uracil into a sandwich between the β2/β3 loops of RRM1 and RRM2.	RESULTS
52	58	linker	structure_element	This nucleotide twists to face away from the U2AF65 linker and instead inserts the rU6-uracil into a sandwich between the β2/β3 loops of RRM1 and RRM2.	RESULTS
83	86	rU6	residue_name_number	This nucleotide twists to face away from the U2AF65 linker and instead inserts the rU6-uracil into a sandwich between the β2/β3 loops of RRM1 and RRM2.	RESULTS
87	93	uracil	residue_name	This nucleotide twists to face away from the U2AF65 linker and instead inserts the rU6-uracil into a sandwich between the β2/β3 loops of RRM1 and RRM2.	RESULTS
122	133	β2/β3 loops	structure_element	This nucleotide twists to face away from the U2AF65 linker and instead inserts the rU6-uracil into a sandwich between the β2/β3 loops of RRM1 and RRM2.	RESULTS
137	141	RRM1	structure_element	This nucleotide twists to face away from the U2AF65 linker and instead inserts the rU6-uracil into a sandwich between the β2/β3 loops of RRM1 and RRM2.	RESULTS
146	150	RRM2	structure_element	This nucleotide twists to face away from the U2AF65 linker and instead inserts the rU6-uracil into a sandwich between the β2/β3 loops of RRM1 and RRM2.	RESULTS
4	7	rU6	residue_name_number	The rU6 base edge is relatively solvent exposed; accordingly, the rU6 hydrogen bonds with U2AF65 are water mediated apart from a single direct interaction by the RRM1-N196 side chain.	RESULTS
32	47	solvent exposed	protein_state	The rU6 base edge is relatively solvent exposed; accordingly, the rU6 hydrogen bonds with U2AF65 are water mediated apart from a single direct interaction by the RRM1-N196 side chain.	RESULTS
66	69	rU6	residue_name_number	The rU6 base edge is relatively solvent exposed; accordingly, the rU6 hydrogen bonds with U2AF65 are water mediated apart from a single direct interaction by the RRM1-N196 side chain.	RESULTS
70	84	hydrogen bonds	bond_interaction	The rU6 base edge is relatively solvent exposed; accordingly, the rU6 hydrogen bonds with U2AF65 are water mediated apart from a single direct interaction by the RRM1-N196 side chain.	RESULTS
90	96	U2AF65	protein	The rU6 base edge is relatively solvent exposed; accordingly, the rU6 hydrogen bonds with U2AF65 are water mediated apart from a single direct interaction by the RRM1-N196 side chain.	RESULTS
101	106	water	chemical	The rU6 base edge is relatively solvent exposed; accordingly, the rU6 hydrogen bonds with U2AF65 are water mediated apart from a single direct interaction by the RRM1-N196 side chain.	RESULTS
162	166	RRM1	structure_element	The rU6 base edge is relatively solvent exposed; accordingly, the rU6 hydrogen bonds with U2AF65 are water mediated apart from a single direct interaction by the RRM1-N196 side chain.	RESULTS
167	171	N196	residue_name_number	The rU6 base edge is relatively solvent exposed; accordingly, the rU6 hydrogen bonds with U2AF65 are water mediated apart from a single direct interaction by the RRM1-N196 side chain.	RESULTS
3	26	tested the contribution	experimental_method	We tested the contribution of the U2AF651,2L interactions with the new central nucleotide to Py-tract affinity (Fig. 3i; Supplementary Fig. 4a,b).	RESULTS
34	44	U2AF651,2L	mutant	We tested the contribution of the U2AF651,2L interactions with the new central nucleotide to Py-tract affinity (Fig. 3i; Supplementary Fig. 4a,b).	RESULTS
79	89	nucleotide	chemical	We tested the contribution of the U2AF651,2L interactions with the new central nucleotide to Py-tract affinity (Fig. 3i; Supplementary Fig. 4a,b).	RESULTS
93	110	Py-tract affinity	evidence	We tested the contribution of the U2AF651,2L interactions with the new central nucleotide to Py-tract affinity (Fig. 3i; Supplementary Fig. 4a,b).	RESULTS
0	11	Mutagenesis	experimental_method	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
22	26	V254	residue_name_number	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
34	40	U2AF65	protein	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
41	57	inter-RRM linker	structure_element	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
61	68	proline	residue_name	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
72	76	RRM1	structure_element	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
77	81	R227	residue_name_number	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
85	92	alanine	residue_name	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
111	124	hydrogen bond	bond_interaction	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
134	139	fifth	residue_number	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
140	146	uracil	residue_name	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
170	180	affinities	evidence	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
184	194	U2AF651,2L	mutant	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
218	222	AdML	gene	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
223	231	Py tract	chemical	Mutagenesis of either V254 in the U2AF65 inter-RRM linker to proline or RRM1–R227 to alanine, which remove the hydrogen bond with the fifth uracil-O4 or -O2, reduced the affinities of U2AF651,2L for the representative AdML Py tract by four- or five-fold, respectively.	RESULTS
48	51	ΔΔG	evidence	The energetic penalties due to these mutations (ΔΔG 0.8–0.9 kcal mol−1) are consistent with the loss of each hydrogen bond with the rU5 base and support the relevance of the central nucleotide interactions observed in the U2AF651,2L structures.	RESULTS
109	122	hydrogen bond	bond_interaction	The energetic penalties due to these mutations (ΔΔG 0.8–0.9 kcal mol−1) are consistent with the loss of each hydrogen bond with the rU5 base and support the relevance of the central nucleotide interactions observed in the U2AF651,2L structures.	RESULTS
132	135	rU5	residue_name_number	The energetic penalties due to these mutations (ΔΔG 0.8–0.9 kcal mol−1) are consistent with the loss of each hydrogen bond with the rU5 base and support the relevance of the central nucleotide interactions observed in the U2AF651,2L structures.	RESULTS
222	232	U2AF651,2L	mutant	The energetic penalties due to these mutations (ΔΔG 0.8–0.9 kcal mol−1) are consistent with the loss of each hydrogen bond with the rU5 base and support the relevance of the central nucleotide interactions observed in the U2AF651,2L structures.	RESULTS
233	243	structures	evidence	The energetic penalties due to these mutations (ΔΔG 0.8–0.9 kcal mol−1) are consistent with the loss of each hydrogen bond with the rU5 base and support the relevance of the central nucleotide interactions observed in the U2AF651,2L structures.	RESULTS
0	6	U2AF65	protein	U2AF65 RRM extensions interact with the Py tract	RESULTS
7	21	RRM extensions	structure_element	U2AF65 RRM extensions interact with the Py tract	RESULTS
40	48	Py tract	chemical	U2AF65 RRM extensions interact with the Py tract	RESULTS
4	32	N- and C-terminal extensions	structure_element	The N- and C-terminal extensions of the U2AF65 RRM1 and RRM2 directly contact the bound Py tract.	RESULTS
40	46	U2AF65	protein	The N- and C-terminal extensions of the U2AF65 RRM1 and RRM2 directly contact the bound Py tract.	RESULTS
47	51	RRM1	structure_element	The N- and C-terminal extensions of the U2AF65 RRM1 and RRM2 directly contact the bound Py tract.	RESULTS
56	60	RRM2	structure_element	The N- and C-terminal extensions of the U2AF65 RRM1 and RRM2 directly contact the bound Py tract.	RESULTS
82	87	bound	protein_state	The N- and C-terminal extensions of the U2AF65 RRM1 and RRM2 directly contact the bound Py tract.	RESULTS
88	96	Py tract	chemical	The N- and C-terminal extensions of the U2AF65 RRM1 and RRM2 directly contact the bound Py tract.	RESULTS
47	57	nucleotide	chemical	Rather than interacting with a new 5′-terminal nucleotide as we had hypothesized, the C-terminal α-helix of RRM2 instead folds across one surface of rU3 in the third binding site (Fig. 3b).	RESULTS
97	104	α-helix	structure_element	Rather than interacting with a new 5′-terminal nucleotide as we had hypothesized, the C-terminal α-helix of RRM2 instead folds across one surface of rU3 in the third binding site (Fig. 3b).	RESULTS
108	112	RRM2	structure_element	Rather than interacting with a new 5′-terminal nucleotide as we had hypothesized, the C-terminal α-helix of RRM2 instead folds across one surface of rU3 in the third binding site (Fig. 3b).	RESULTS
149	152	rU3	residue_name_number	Rather than interacting with a new 5′-terminal nucleotide as we had hypothesized, the C-terminal α-helix of RRM2 instead folds across one surface of rU3 in the third binding site (Fig. 3b).	RESULTS
160	178	third binding site	site	Rather than interacting with a new 5′-terminal nucleotide as we had hypothesized, the C-terminal α-helix of RRM2 instead folds across one surface of rU3 in the third binding site (Fig. 3b).	RESULTS
9	20	salt bridge	bond_interaction	There, a salt bridge between the K340 side chain and nucleotide phosphate, as well as G338-base stacking and a hydrogen bond between the backbone amide of G338 and the rU3-O4, secure the RRM2 extension.	RESULTS
33	37	K340	residue_name_number	There, a salt bridge between the K340 side chain and nucleotide phosphate, as well as G338-base stacking and a hydrogen bond between the backbone amide of G338 and the rU3-O4, secure the RRM2 extension.	RESULTS
53	63	nucleotide	chemical	There, a salt bridge between the K340 side chain and nucleotide phosphate, as well as G338-base stacking and a hydrogen bond between the backbone amide of G338 and the rU3-O4, secure the RRM2 extension.	RESULTS
86	90	G338	residue_name_number	There, a salt bridge between the K340 side chain and nucleotide phosphate, as well as G338-base stacking and a hydrogen bond between the backbone amide of G338 and the rU3-O4, secure the RRM2 extension.	RESULTS
96	104	stacking	bond_interaction	There, a salt bridge between the K340 side chain and nucleotide phosphate, as well as G338-base stacking and a hydrogen bond between the backbone amide of G338 and the rU3-O4, secure the RRM2 extension.	RESULTS
111	124	hydrogen bond	bond_interaction	There, a salt bridge between the K340 side chain and nucleotide phosphate, as well as G338-base stacking and a hydrogen bond between the backbone amide of G338 and the rU3-O4, secure the RRM2 extension.	RESULTS
155	159	G338	residue_name_number	There, a salt bridge between the K340 side chain and nucleotide phosphate, as well as G338-base stacking and a hydrogen bond between the backbone amide of G338 and the rU3-O4, secure the RRM2 extension.	RESULTS
168	171	rU3	residue_name_number	There, a salt bridge between the K340 side chain and nucleotide phosphate, as well as G338-base stacking and a hydrogen bond between the backbone amide of G338 and the rU3-O4, secure the RRM2 extension.	RESULTS
187	201	RRM2 extension	structure_element	There, a salt bridge between the K340 side chain and nucleotide phosphate, as well as G338-base stacking and a hydrogen bond between the backbone amide of G338 and the rU3-O4, secure the RRM2 extension.	RESULTS
45	50	third	residue_number	Indirectly, the additional contacts with the third nucleotide shift the rU2 nucleotide in the second binding site closer to the C-terminal β-strand of RRM2.	RESULTS
51	61	nucleotide	chemical	Indirectly, the additional contacts with the third nucleotide shift the rU2 nucleotide in the second binding site closer to the C-terminal β-strand of RRM2.	RESULTS
72	75	rU2	residue_name_number	Indirectly, the additional contacts with the third nucleotide shift the rU2 nucleotide in the second binding site closer to the C-terminal β-strand of RRM2.	RESULTS
76	86	nucleotide	chemical	Indirectly, the additional contacts with the third nucleotide shift the rU2 nucleotide in the second binding site closer to the C-terminal β-strand of RRM2.	RESULTS
94	113	second binding site	site	Indirectly, the additional contacts with the third nucleotide shift the rU2 nucleotide in the second binding site closer to the C-terminal β-strand of RRM2.	RESULTS
139	147	β-strand	structure_element	Indirectly, the additional contacts with the third nucleotide shift the rU2 nucleotide in the second binding site closer to the C-terminal β-strand of RRM2.	RESULTS
151	155	RRM2	structure_element	Indirectly, the additional contacts with the third nucleotide shift the rU2 nucleotide in the second binding site closer to the C-terminal β-strand of RRM2.	RESULTS
18	34	U2AF651,2L-bound	protein_state	Consequently, the U2AF651,2L-bound rU2-O4 and -N3H form dual hydrogen bonds with the K329 backbone atoms (Fig. 3a), rather than a single hydrogen bond with the K329 side chain as in the prior dU2AF651,2 structure (Supplementary Fig. 3b).	RESULTS
35	38	rU2	residue_name_number	Consequently, the U2AF651,2L-bound rU2-O4 and -N3H form dual hydrogen bonds with the K329 backbone atoms (Fig. 3a), rather than a single hydrogen bond with the K329 side chain as in the prior dU2AF651,2 structure (Supplementary Fig. 3b).	RESULTS
61	75	hydrogen bonds	bond_interaction	Consequently, the U2AF651,2L-bound rU2-O4 and -N3H form dual hydrogen bonds with the K329 backbone atoms (Fig. 3a), rather than a single hydrogen bond with the K329 side chain as in the prior dU2AF651,2 structure (Supplementary Fig. 3b).	RESULTS
85	89	K329	residue_name_number	Consequently, the U2AF651,2L-bound rU2-O4 and -N3H form dual hydrogen bonds with the K329 backbone atoms (Fig. 3a), rather than a single hydrogen bond with the K329 side chain as in the prior dU2AF651,2 structure (Supplementary Fig. 3b).	RESULTS
137	150	hydrogen bond	bond_interaction	Consequently, the U2AF651,2L-bound rU2-O4 and -N3H form dual hydrogen bonds with the K329 backbone atoms (Fig. 3a), rather than a single hydrogen bond with the K329 side chain as in the prior dU2AF651,2 structure (Supplementary Fig. 3b).	RESULTS
160	164	K329	residue_name_number	Consequently, the U2AF651,2L-bound rU2-O4 and -N3H form dual hydrogen bonds with the K329 backbone atoms (Fig. 3a), rather than a single hydrogen bond with the K329 side chain as in the prior dU2AF651,2 structure (Supplementary Fig. 3b).	RESULTS
192	202	dU2AF651,2	mutant	Consequently, the U2AF651,2L-bound rU2-O4 and -N3H form dual hydrogen bonds with the K329 backbone atoms (Fig. 3a), rather than a single hydrogen bond with the K329 side chain as in the prior dU2AF651,2 structure (Supplementary Fig. 3b).	RESULTS
203	212	structure	evidence	Consequently, the U2AF651,2L-bound rU2-O4 and -N3H form dual hydrogen bonds with the K329 backbone atoms (Fig. 3a), rather than a single hydrogen bond with the K329 side chain as in the prior dU2AF651,2 structure (Supplementary Fig. 3b).	RESULTS
23	42	α-helical extension	structure_element	At the N terminus, the α-helical extension of U2AF65 RRM1 positions the Q147 side chain to bridge the eighth and ninth nucleotides at the 3′ terminus of the Py tract (Fig. 3f–h).	RESULTS
46	52	U2AF65	protein	At the N terminus, the α-helical extension of U2AF65 RRM1 positions the Q147 side chain to bridge the eighth and ninth nucleotides at the 3′ terminus of the Py tract (Fig. 3f–h).	RESULTS
53	57	RRM1	structure_element	At the N terminus, the α-helical extension of U2AF65 RRM1 positions the Q147 side chain to bridge the eighth and ninth nucleotides at the 3′ terminus of the Py tract (Fig. 3f–h).	RESULTS
72	76	Q147	residue_name_number	At the N terminus, the α-helical extension of U2AF65 RRM1 positions the Q147 side chain to bridge the eighth and ninth nucleotides at the 3′ terminus of the Py tract (Fig. 3f–h).	RESULTS
102	108	eighth	residue_number	At the N terminus, the α-helical extension of U2AF65 RRM1 positions the Q147 side chain to bridge the eighth and ninth nucleotides at the 3′ terminus of the Py tract (Fig. 3f–h).	RESULTS
113	118	ninth	residue_number	At the N terminus, the α-helical extension of U2AF65 RRM1 positions the Q147 side chain to bridge the eighth and ninth nucleotides at the 3′ terminus of the Py tract (Fig. 3f–h).	RESULTS
119	130	nucleotides	chemical	At the N terminus, the α-helical extension of U2AF65 RRM1 positions the Q147 side chain to bridge the eighth and ninth nucleotides at the 3′ terminus of the Py tract (Fig. 3f–h).	RESULTS
138	149	3′ terminus	site	At the N terminus, the α-helical extension of U2AF65 RRM1 positions the Q147 side chain to bridge the eighth and ninth nucleotides at the 3′ terminus of the Py tract (Fig. 3f–h).	RESULTS
157	165	Py tract	chemical	At the N terminus, the α-helical extension of U2AF65 RRM1 positions the Q147 side chain to bridge the eighth and ninth nucleotides at the 3′ terminus of the Py tract (Fig. 3f–h).	RESULTS
4	8	Q147	residue_name_number	The Q147 residue participates in hydrogen bonds with the -N3H of the eighth uracil and -O2 of the ninth pyrimidine.	RESULTS
33	47	hydrogen bonds	bond_interaction	The Q147 residue participates in hydrogen bonds with the -N3H of the eighth uracil and -O2 of the ninth pyrimidine.	RESULTS
69	75	eighth	residue_number	The Q147 residue participates in hydrogen bonds with the -N3H of the eighth uracil and -O2 of the ninth pyrimidine.	RESULTS
76	82	uracil	residue_name	The Q147 residue participates in hydrogen bonds with the -N3H of the eighth uracil and -O2 of the ninth pyrimidine.	RESULTS
98	103	ninth	residue_number	The Q147 residue participates in hydrogen bonds with the -N3H of the eighth uracil and -O2 of the ninth pyrimidine.	RESULTS
104	114	pyrimidine	chemical	The Q147 residue participates in hydrogen bonds with the -N3H of the eighth uracil and -O2 of the ninth pyrimidine.	RESULTS
13	17	R146	residue_name_number	The adjacent R146 guanidinium group donates hydrogen bonds to the 3′-terminal ribose-O2′ and O3′ atoms, where it could form a salt bridge with a phospho-diester group in the context of a longer pre-mRNA.	RESULTS
44	58	hydrogen bonds	bond_interaction	The adjacent R146 guanidinium group donates hydrogen bonds to the 3′-terminal ribose-O2′ and O3′ atoms, where it could form a salt bridge with a phospho-diester group in the context of a longer pre-mRNA.	RESULTS
78	84	ribose	chemical	The adjacent R146 guanidinium group donates hydrogen bonds to the 3′-terminal ribose-O2′ and O3′ atoms, where it could form a salt bridge with a phospho-diester group in the context of a longer pre-mRNA.	RESULTS
126	137	salt bridge	bond_interaction	The adjacent R146 guanidinium group donates hydrogen bonds to the 3′-terminal ribose-O2′ and O3′ atoms, where it could form a salt bridge with a phospho-diester group in the context of a longer pre-mRNA.	RESULTS
194	202	pre-mRNA	chemical	The adjacent R146 guanidinium group donates hydrogen bonds to the 3′-terminal ribose-O2′ and O3′ atoms, where it could form a salt bridge with a phospho-diester group in the context of a longer pre-mRNA.	RESULTS
26	39	hydrogen bond	bond_interaction	Consistent with loss of a hydrogen bond with the ninth pyrimidine-O2 (ΔΔG 1.0 kcal mol−1), mutation of the Q147 to an alanine reduced U2AF651,2L affinity for the AdML Py tract by five-fold (Fig. 3i; Supplementary Fig. 4c).	RESULTS
49	54	ninth	residue_number	Consistent with loss of a hydrogen bond with the ninth pyrimidine-O2 (ΔΔG 1.0 kcal mol−1), mutation of the Q147 to an alanine reduced U2AF651,2L affinity for the AdML Py tract by five-fold (Fig. 3i; Supplementary Fig. 4c).	RESULTS
55	65	pyrimidine	chemical	Consistent with loss of a hydrogen bond with the ninth pyrimidine-O2 (ΔΔG 1.0 kcal mol−1), mutation of the Q147 to an alanine reduced U2AF651,2L affinity for the AdML Py tract by five-fold (Fig. 3i; Supplementary Fig. 4c).	RESULTS
70	73	ΔΔG	evidence	Consistent with loss of a hydrogen bond with the ninth pyrimidine-O2 (ΔΔG 1.0 kcal mol−1), mutation of the Q147 to an alanine reduced U2AF651,2L affinity for the AdML Py tract by five-fold (Fig. 3i; Supplementary Fig. 4c).	RESULTS
91	99	mutation	experimental_method	Consistent with loss of a hydrogen bond with the ninth pyrimidine-O2 (ΔΔG 1.0 kcal mol−1), mutation of the Q147 to an alanine reduced U2AF651,2L affinity for the AdML Py tract by five-fold (Fig. 3i; Supplementary Fig. 4c).	RESULTS
107	111	Q147	residue_name_number	Consistent with loss of a hydrogen bond with the ninth pyrimidine-O2 (ΔΔG 1.0 kcal mol−1), mutation of the Q147 to an alanine reduced U2AF651,2L affinity for the AdML Py tract by five-fold (Fig. 3i; Supplementary Fig. 4c).	RESULTS
118	125	alanine	residue_name	Consistent with loss of a hydrogen bond with the ninth pyrimidine-O2 (ΔΔG 1.0 kcal mol−1), mutation of the Q147 to an alanine reduced U2AF651,2L affinity for the AdML Py tract by five-fold (Fig. 3i; Supplementary Fig. 4c).	RESULTS
134	153	U2AF651,2L affinity	evidence	Consistent with loss of a hydrogen bond with the ninth pyrimidine-O2 (ΔΔG 1.0 kcal mol−1), mutation of the Q147 to an alanine reduced U2AF651,2L affinity for the AdML Py tract by five-fold (Fig. 3i; Supplementary Fig. 4c).	RESULTS
162	166	AdML	gene	Consistent with loss of a hydrogen bond with the ninth pyrimidine-O2 (ΔΔG 1.0 kcal mol−1), mutation of the Q147 to an alanine reduced U2AF651,2L affinity for the AdML Py tract by five-fold (Fig. 3i; Supplementary Fig. 4c).	RESULTS
167	175	Py tract	chemical	Consistent with loss of a hydrogen bond with the ninth pyrimidine-O2 (ΔΔG 1.0 kcal mol−1), mutation of the Q147 to an alanine reduced U2AF651,2L affinity for the AdML Py tract by five-fold (Fig. 3i; Supplementary Fig. 4c).	RESULTS
3	10	compare	experimental_method	We compare U2AF65 interactions with uracil relative to cytosine pyrimidines at the ninth binding site in Fig. 3g,h and the Supplementary Discussion.	RESULTS
11	17	U2AF65	protein	We compare U2AF65 interactions with uracil relative to cytosine pyrimidines at the ninth binding site in Fig. 3g,h and the Supplementary Discussion.	RESULTS
36	42	uracil	residue_name	We compare U2AF65 interactions with uracil relative to cytosine pyrimidines at the ninth binding site in Fig. 3g,h and the Supplementary Discussion.	RESULTS
55	63	cytosine	residue_name	We compare U2AF65 interactions with uracil relative to cytosine pyrimidines at the ninth binding site in Fig. 3g,h and the Supplementary Discussion.	RESULTS
64	75	pyrimidines	chemical	We compare U2AF65 interactions with uracil relative to cytosine pyrimidines at the ninth binding site in Fig. 3g,h and the Supplementary Discussion.	RESULTS
83	101	ninth binding site	site	We compare U2AF65 interactions with uracil relative to cytosine pyrimidines at the ninth binding site in Fig. 3g,h and the Supplementary Discussion.	RESULTS
34	40	U2AF65	protein	Versatile primary sequence of the U2AF65 inter-RRM linker	RESULTS
41	57	inter-RRM linker	structure_element	Versatile primary sequence of the U2AF65 inter-RRM linker	RESULTS
4	14	U2AF651,2L	mutant	The U2AF651,2L structures reveal that the inter-RRM linker mediates an extensive interface with the second α-helix of RRM1, the β2/β3 strands of RRM2 and the N-terminal α-helical extension of RRM1.	RESULTS
15	25	structures	evidence	The U2AF651,2L structures reveal that the inter-RRM linker mediates an extensive interface with the second α-helix of RRM1, the β2/β3 strands of RRM2 and the N-terminal α-helical extension of RRM1.	RESULTS
42	58	inter-RRM linker	structure_element	The U2AF651,2L structures reveal that the inter-RRM linker mediates an extensive interface with the second α-helix of RRM1, the β2/β3 strands of RRM2 and the N-terminal α-helical extension of RRM1.	RESULTS
71	90	extensive interface	site	The U2AF651,2L structures reveal that the inter-RRM linker mediates an extensive interface with the second α-helix of RRM1, the β2/β3 strands of RRM2 and the N-terminal α-helical extension of RRM1.	RESULTS
107	114	α-helix	structure_element	The U2AF651,2L structures reveal that the inter-RRM linker mediates an extensive interface with the second α-helix of RRM1, the β2/β3 strands of RRM2 and the N-terminal α-helical extension of RRM1.	RESULTS
118	122	RRM1	structure_element	The U2AF651,2L structures reveal that the inter-RRM linker mediates an extensive interface with the second α-helix of RRM1, the β2/β3 strands of RRM2 and the N-terminal α-helical extension of RRM1.	RESULTS
128	141	β2/β3 strands	structure_element	The U2AF651,2L structures reveal that the inter-RRM linker mediates an extensive interface with the second α-helix of RRM1, the β2/β3 strands of RRM2 and the N-terminal α-helical extension of RRM1.	RESULTS
145	149	RRM2	structure_element	The U2AF651,2L structures reveal that the inter-RRM linker mediates an extensive interface with the second α-helix of RRM1, the β2/β3 strands of RRM2 and the N-terminal α-helical extension of RRM1.	RESULTS
169	188	α-helical extension	structure_element	The U2AF651,2L structures reveal that the inter-RRM linker mediates an extensive interface with the second α-helix of RRM1, the β2/β3 strands of RRM2 and the N-terminal α-helical extension of RRM1.	RESULTS
192	196	RRM1	structure_element	The U2AF651,2L structures reveal that the inter-RRM linker mediates an extensive interface with the second α-helix of RRM1, the β2/β3 strands of RRM2 and the N-terminal α-helical extension of RRM1.	RESULTS
16	22	U2AF65	protein	Altogether, the U2AF65 inter-RRM linker residues (R228–K260) bury 2,800 Å2 of surface area in the U2AF651,2L holo-protein, suggestive of a cognate interface compared with 1,900 Å2 for a typical protein–protein complex.	RESULTS
23	39	inter-RRM linker	structure_element	Altogether, the U2AF65 inter-RRM linker residues (R228–K260) bury 2,800 Å2 of surface area in the U2AF651,2L holo-protein, suggestive of a cognate interface compared with 1,900 Å2 for a typical protein–protein complex.	RESULTS
50	59	R228–K260	residue_range	Altogether, the U2AF65 inter-RRM linker residues (R228–K260) bury 2,800 Å2 of surface area in the U2AF651,2L holo-protein, suggestive of a cognate interface compared with 1,900 Å2 for a typical protein–protein complex.	RESULTS
98	108	U2AF651,2L	mutant	Altogether, the U2AF65 inter-RRM linker residues (R228–K260) bury 2,800 Å2 of surface area in the U2AF651,2L holo-protein, suggestive of a cognate interface compared with 1,900 Å2 for a typical protein–protein complex.	RESULTS
109	121	holo-protein	protein_state	Altogether, the U2AF65 inter-RRM linker residues (R228–K260) bury 2,800 Å2 of surface area in the U2AF651,2L holo-protein, suggestive of a cognate interface compared with 1,900 Å2 for a typical protein–protein complex.	RESULTS
139	156	cognate interface	site	Altogether, the U2AF65 inter-RRM linker residues (R228–K260) bury 2,800 Å2 of surface area in the U2AF651,2L holo-protein, suggestive of a cognate interface compared with 1,900 Å2 for a typical protein–protein complex.	RESULTS
16	22	linker	structure_element	The path of the linker initiates at P229 following the core RRM1 β-strand, in a kink that is positioned by intra-molecular stacking among the consecutive R228, Y232 and P234 side chains (Fig. 4a, lower right).	RESULTS
36	40	P229	residue_name_number	The path of the linker initiates at P229 following the core RRM1 β-strand, in a kink that is positioned by intra-molecular stacking among the consecutive R228, Y232 and P234 side chains (Fig. 4a, lower right).	RESULTS
55	59	core	protein_state	The path of the linker initiates at P229 following the core RRM1 β-strand, in a kink that is positioned by intra-molecular stacking among the consecutive R228, Y232 and P234 side chains (Fig. 4a, lower right).	RESULTS
60	64	RRM1	structure_element	The path of the linker initiates at P229 following the core RRM1 β-strand, in a kink that is positioned by intra-molecular stacking among the consecutive R228, Y232 and P234 side chains (Fig. 4a, lower right).	RESULTS
65	73	β-strand	structure_element	The path of the linker initiates at P229 following the core RRM1 β-strand, in a kink that is positioned by intra-molecular stacking among the consecutive R228, Y232 and P234 side chains (Fig. 4a, lower right).	RESULTS
80	84	kink	structure_element	The path of the linker initiates at P229 following the core RRM1 β-strand, in a kink that is positioned by intra-molecular stacking among the consecutive R228, Y232 and P234 side chains (Fig. 4a, lower right).	RESULTS
107	131	intra-molecular stacking	bond_interaction	The path of the linker initiates at P229 following the core RRM1 β-strand, in a kink that is positioned by intra-molecular stacking among the consecutive R228, Y232 and P234 side chains (Fig. 4a, lower right).	RESULTS
154	158	R228	residue_name_number	The path of the linker initiates at P229 following the core RRM1 β-strand, in a kink that is positioned by intra-molecular stacking among the consecutive R228, Y232 and P234 side chains (Fig. 4a, lower right).	RESULTS
160	164	Y232	residue_name_number	The path of the linker initiates at P229 following the core RRM1 β-strand, in a kink that is positioned by intra-molecular stacking among the consecutive R228, Y232 and P234 side chains (Fig. 4a, lower right).	RESULTS
169	173	P234	residue_name_number	The path of the linker initiates at P229 following the core RRM1 β-strand, in a kink that is positioned by intra-molecular stacking among the consecutive R228, Y232 and P234 side chains (Fig. 4a, lower right).	RESULTS
2	13	second kink	structure_element	A second kink at P236, coupled with respective packing of the L235 and M238 side chains on the N-terminal α-helical RRM1 extension and the core RRM1 α2-helix, reverses the direction of the inter-RRM linker towards the RRM1/RRM2 interface and away from the RNA-binding site.	RESULTS
17	21	P236	residue_name_number	A second kink at P236, coupled with respective packing of the L235 and M238 side chains on the N-terminal α-helical RRM1 extension and the core RRM1 α2-helix, reverses the direction of the inter-RRM linker towards the RRM1/RRM2 interface and away from the RNA-binding site.	RESULTS
62	66	L235	residue_name_number	A second kink at P236, coupled with respective packing of the L235 and M238 side chains on the N-terminal α-helical RRM1 extension and the core RRM1 α2-helix, reverses the direction of the inter-RRM linker towards the RRM1/RRM2 interface and away from the RNA-binding site.	RESULTS
71	75	M238	residue_name_number	A second kink at P236, coupled with respective packing of the L235 and M238 side chains on the N-terminal α-helical RRM1 extension and the core RRM1 α2-helix, reverses the direction of the inter-RRM linker towards the RRM1/RRM2 interface and away from the RNA-binding site.	RESULTS
106	130	α-helical RRM1 extension	structure_element	A second kink at P236, coupled with respective packing of the L235 and M238 side chains on the N-terminal α-helical RRM1 extension and the core RRM1 α2-helix, reverses the direction of the inter-RRM linker towards the RRM1/RRM2 interface and away from the RNA-binding site.	RESULTS
139	143	core	protein_state	A second kink at P236, coupled with respective packing of the L235 and M238 side chains on the N-terminal α-helical RRM1 extension and the core RRM1 α2-helix, reverses the direction of the inter-RRM linker towards the RRM1/RRM2 interface and away from the RNA-binding site.	RESULTS
144	148	RRM1	structure_element	A second kink at P236, coupled with respective packing of the L235 and M238 side chains on the N-terminal α-helical RRM1 extension and the core RRM1 α2-helix, reverses the direction of the inter-RRM linker towards the RRM1/RRM2 interface and away from the RNA-binding site.	RESULTS
149	157	α2-helix	structure_element	A second kink at P236, coupled with respective packing of the L235 and M238 side chains on the N-terminal α-helical RRM1 extension and the core RRM1 α2-helix, reverses the direction of the inter-RRM linker towards the RRM1/RRM2 interface and away from the RNA-binding site.	RESULTS
189	205	inter-RRM linker	structure_element	A second kink at P236, coupled with respective packing of the L235 and M238 side chains on the N-terminal α-helical RRM1 extension and the core RRM1 α2-helix, reverses the direction of the inter-RRM linker towards the RRM1/RRM2 interface and away from the RNA-binding site.	RESULTS
218	237	RRM1/RRM2 interface	site	A second kink at P236, coupled with respective packing of the L235 and M238 side chains on the N-terminal α-helical RRM1 extension and the core RRM1 α2-helix, reverses the direction of the inter-RRM linker towards the RRM1/RRM2 interface and away from the RNA-binding site.	RESULTS
256	272	RNA-binding site	site	A second kink at P236, coupled with respective packing of the L235 and M238 side chains on the N-terminal α-helical RRM1 extension and the core RRM1 α2-helix, reverses the direction of the inter-RRM linker towards the RRM1/RRM2 interface and away from the RNA-binding site.	RESULTS
41	47	linker	structure_element	In the neighbouring apical region of the linker, the V244 and V246 side chains pack in a hydrophobic pocket between two α-helices of the core RRM1.	RESULTS
53	57	V244	residue_name_number	In the neighbouring apical region of the linker, the V244 and V246 side chains pack in a hydrophobic pocket between two α-helices of the core RRM1.	RESULTS
62	66	V246	residue_name_number	In the neighbouring apical region of the linker, the V244 and V246 side chains pack in a hydrophobic pocket between two α-helices of the core RRM1.	RESULTS
89	107	hydrophobic pocket	site	In the neighbouring apical region of the linker, the V244 and V246 side chains pack in a hydrophobic pocket between two α-helices of the core RRM1.	RESULTS
120	129	α-helices	structure_element	In the neighbouring apical region of the linker, the V244 and V246 side chains pack in a hydrophobic pocket between two α-helices of the core RRM1.	RESULTS
137	141	core	protein_state	In the neighbouring apical region of the linker, the V244 and V246 side chains pack in a hydrophobic pocket between two α-helices of the core RRM1.	RESULTS
142	146	RRM1	structure_element	In the neighbouring apical region of the linker, the V244 and V246 side chains pack in a hydrophobic pocket between two α-helices of the core RRM1.	RESULTS
13	17	V249	residue_name_number	The adjacent V249 and V250 are notable for their respective interactions that connect RRM1 and RRM2 at this distal interface from the RNA-binding site (Fig. 4a, top).	RESULTS
22	26	V250	residue_name_number	The adjacent V249 and V250 are notable for their respective interactions that connect RRM1 and RRM2 at this distal interface from the RNA-binding site (Fig. 4a, top).	RESULTS
86	90	RRM1	structure_element	The adjacent V249 and V250 are notable for their respective interactions that connect RRM1 and RRM2 at this distal interface from the RNA-binding site (Fig. 4a, top).	RESULTS
95	99	RRM2	structure_element	The adjacent V249 and V250 are notable for their respective interactions that connect RRM1 and RRM2 at this distal interface from the RNA-binding site (Fig. 4a, top).	RESULTS
115	124	interface	site	The adjacent V249 and V250 are notable for their respective interactions that connect RRM1 and RRM2 at this distal interface from the RNA-binding site (Fig. 4a, top).	RESULTS
134	150	RNA-binding site	site	The adjacent V249 and V250 are notable for their respective interactions that connect RRM1 and RRM2 at this distal interface from the RNA-binding site (Fig. 4a, top).	RESULTS
2	12	third kink	structure_element	A third kink stacks P247 and G248 with Y245 and re-orients the C-terminal region of the linker towards the RRM2 and bound RNA.	RESULTS
13	19	stacks	bond_interaction	A third kink stacks P247 and G248 with Y245 and re-orients the C-terminal region of the linker towards the RRM2 and bound RNA.	RESULTS
20	24	P247	residue_name_number	A third kink stacks P247 and G248 with Y245 and re-orients the C-terminal region of the linker towards the RRM2 and bound RNA.	RESULTS
29	33	G248	residue_name_number	A third kink stacks P247 and G248 with Y245 and re-orients the C-terminal region of the linker towards the RRM2 and bound RNA.	RESULTS
39	43	Y245	residue_name_number	A third kink stacks P247 and G248 with Y245 and re-orients the C-terminal region of the linker towards the RRM2 and bound RNA.	RESULTS
63	80	C-terminal region	structure_element	A third kink stacks P247 and G248 with Y245 and re-orients the C-terminal region of the linker towards the RRM2 and bound RNA.	RESULTS
88	94	linker	structure_element	A third kink stacks P247 and G248 with Y245 and re-orients the C-terminal region of the linker towards the RRM2 and bound RNA.	RESULTS
107	111	RRM2	structure_element	A third kink stacks P247 and G248 with Y245 and re-orients the C-terminal region of the linker towards the RRM2 and bound RNA.	RESULTS
116	121	bound	protein_state	A third kink stacks P247 and G248 with Y245 and re-orients the C-terminal region of the linker towards the RRM2 and bound RNA.	RESULTS
122	125	RNA	chemical	A third kink stacks P247 and G248 with Y245 and re-orients the C-terminal region of the linker towards the RRM2 and bound RNA.	RESULTS
7	10	RNA	chemical	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
28	32	V254	residue_name_number	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
53	58	fifth	residue_number	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
59	65	uracil	residue_name	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
81	101	hydrophobic contacts	bond_interaction	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
133	148	β-sheet surface	structure_element	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
152	156	RRM2	structure_element	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
180	184	RNP1	structure_element	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
185	189	F304	residue_name_number	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
203	209	stacks	bond_interaction	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
219	225	fourth	residue_number	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
226	232	uracil	residue_name	At the RNA surface, the key V254 that recognizes the fifth uracil is secured via hydrophobic contacts between its side chain and the β-sheet surface of RRM2, chiefly the consensus RNP1-F304 residue that stacks with the fourth uracil (Fig. 4a, lower left).	RESULTS
67	73	linker	structure_element	Few direct contacts are made between the remaining residues of the linker and the U2AF65 RRM2; instead, the C-terminal conformation of the linker appears primarily RNA mediated (Fig. 3c,d).	RESULTS
82	88	U2AF65	protein	Few direct contacts are made between the remaining residues of the linker and the U2AF65 RRM2; instead, the C-terminal conformation of the linker appears primarily RNA mediated (Fig. 3c,d).	RESULTS
89	93	RRM2	structure_element	Few direct contacts are made between the remaining residues of the linker and the U2AF65 RRM2; instead, the C-terminal conformation of the linker appears primarily RNA mediated (Fig. 3c,d).	RESULTS
139	145	linker	structure_element	Few direct contacts are made between the remaining residues of the linker and the U2AF65 RRM2; instead, the C-terminal conformation of the linker appears primarily RNA mediated (Fig. 3c,d).	RESULTS
164	167	RNA	chemical	Few direct contacts are made between the remaining residues of the linker and the U2AF65 RRM2; instead, the C-terminal conformation of the linker appears primarily RNA mediated (Fig. 3c,d).	RESULTS
58	62	RRMs	structure_element	We investigated whether the observed contacts between the RRMs and linker were critical for RNA binding by structure-guided mutagenesis (Fig. 4b).	RESULTS
67	73	linker	structure_element	We investigated whether the observed contacts between the RRMs and linker were critical for RNA binding by structure-guided mutagenesis (Fig. 4b).	RESULTS
107	135	structure-guided mutagenesis	experimental_method	We investigated whether the observed contacts between the RRMs and linker were critical for RNA binding by structure-guided mutagenesis (Fig. 4b).	RESULTS
3	11	titrated	experimental_method	We titrated these mutant U2AF651,2L proteins into fluorescein-labelled AdML Py-tract RNA and fit the fluorescence anisotropy changes to obtain the apparent equilibrium affinities (Supplementary Fig. 4d–h).	RESULTS
18	24	mutant	protein_state	We titrated these mutant U2AF651,2L proteins into fluorescein-labelled AdML Py-tract RNA and fit the fluorescence anisotropy changes to obtain the apparent equilibrium affinities (Supplementary Fig. 4d–h).	RESULTS
25	35	U2AF651,2L	mutant	We titrated these mutant U2AF651,2L proteins into fluorescein-labelled AdML Py-tract RNA and fit the fluorescence anisotropy changes to obtain the apparent equilibrium affinities (Supplementary Fig. 4d–h).	RESULTS
50	61	fluorescein	chemical	We titrated these mutant U2AF651,2L proteins into fluorescein-labelled AdML Py-tract RNA and fit the fluorescence anisotropy changes to obtain the apparent equilibrium affinities (Supplementary Fig. 4d–h).	RESULTS
71	75	AdML	gene	We titrated these mutant U2AF651,2L proteins into fluorescein-labelled AdML Py-tract RNA and fit the fluorescence anisotropy changes to obtain the apparent equilibrium affinities (Supplementary Fig. 4d–h).	RESULTS
76	88	Py-tract RNA	chemical	We titrated these mutant U2AF651,2L proteins into fluorescein-labelled AdML Py-tract RNA and fit the fluorescence anisotropy changes to obtain the apparent equilibrium affinities (Supplementary Fig. 4d–h).	RESULTS
101	132	fluorescence anisotropy changes	evidence	We titrated these mutant U2AF651,2L proteins into fluorescein-labelled AdML Py-tract RNA and fit the fluorescence anisotropy changes to obtain the apparent equilibrium affinities (Supplementary Fig. 4d–h).	RESULTS
156	178	equilibrium affinities	evidence	We titrated these mutant U2AF651,2L proteins into fluorescein-labelled AdML Py-tract RNA and fit the fluorescence anisotropy changes to obtain the apparent equilibrium affinities (Supplementary Fig. 4d–h).	RESULTS
14	21	glycine	residue_name	We introduced glycine substitutions to maximally reduce the buried surface area without directly interfering with its hydrogen bonds between backbone atoms and the base.	RESULTS
22	35	substitutions	experimental_method	We introduced glycine substitutions to maximally reduce the buried surface area without directly interfering with its hydrogen bonds between backbone atoms and the base.	RESULTS
118	132	hydrogen bonds	bond_interaction	We introduced glycine substitutions to maximally reduce the buried surface area without directly interfering with its hydrogen bonds between backbone atoms and the base.	RESULTS
10	18	replaced	experimental_method	First, we replaced V249 and V250 at the RRM1/RRM2 interface and V254 at the bound RNA site with glycine (3Gly).	RESULTS
19	23	V249	residue_name_number	First, we replaced V249 and V250 at the RRM1/RRM2 interface and V254 at the bound RNA site with glycine (3Gly).	RESULTS
28	32	V250	residue_name_number	First, we replaced V249 and V250 at the RRM1/RRM2 interface and V254 at the bound RNA site with glycine (3Gly).	RESULTS
40	59	RRM1/RRM2 interface	site	First, we replaced V249 and V250 at the RRM1/RRM2 interface and V254 at the bound RNA site with glycine (3Gly).	RESULTS
64	68	V254	residue_name_number	First, we replaced V249 and V250 at the RRM1/RRM2 interface and V254 at the bound RNA site with glycine (3Gly).	RESULTS
76	81	bound	protein_state	First, we replaced V249 and V250 at the RRM1/RRM2 interface and V254 at the bound RNA site with glycine (3Gly).	RESULTS
82	85	RNA	chemical	First, we replaced V249 and V250 at the RRM1/RRM2 interface and V254 at the bound RNA site with glycine (3Gly).	RESULTS
96	103	glycine	residue_name	First, we replaced V249 and V250 at the RRM1/RRM2 interface and V254 at the bound RNA site with glycine (3Gly).	RESULTS
105	109	3Gly	mutant	First, we replaced V249 and V250 at the RRM1/RRM2 interface and V254 at the bound RNA site with glycine (3Gly).	RESULTS
39	43	AdML	gene	However, the resulting decrease in the AdML RNA affinity of the U2AF651,2L-3Gly mutant relative to wild-type protein was not significant (Fig. 4b).	RESULTS
44	56	RNA affinity	evidence	However, the resulting decrease in the AdML RNA affinity of the U2AF651,2L-3Gly mutant relative to wild-type protein was not significant (Fig. 4b).	RESULTS
64	79	U2AF651,2L-3Gly	mutant	However, the resulting decrease in the AdML RNA affinity of the U2AF651,2L-3Gly mutant relative to wild-type protein was not significant (Fig. 4b).	RESULTS
80	86	mutant	protein_state	However, the resulting decrease in the AdML RNA affinity of the U2AF651,2L-3Gly mutant relative to wild-type protein was not significant (Fig. 4b).	RESULTS
99	108	wild-type	protein_state	However, the resulting decrease in the AdML RNA affinity of the U2AF651,2L-3Gly mutant relative to wild-type protein was not significant (Fig. 4b).	RESULTS
109	116	protein	protein	However, the resulting decrease in the AdML RNA affinity of the U2AF651,2L-3Gly mutant relative to wild-type protein was not significant (Fig. 4b).	RESULTS
16	24	replaced	experimental_method	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
30	45	linker residues	structure_element	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
47	51	S251	residue_name_number	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
53	57	T252	residue_name_number	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
59	63	V253	residue_name_number	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
65	69	V254	residue_name_number	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
74	78	P255	residue_name_number	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
87	116	fifth nucleotide-binding site	site	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
122	130	glycines	residue_name	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
132	136	5Gly	mutant	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
162	174	RNA affinity	evidence	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
182	197	U2AF651,2L-5Gly	mutant	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
198	204	mutant	protein_state	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
250	259	wild-type	protein_state	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
260	267	protein	protein	In parallel, we replaced five linker residues (S251, T252, V253, V254 and P255) at the fifth nucleotide-binding site with glycines (5Gly) and also found that the RNA affinity of the U2AF651,2L-5Gly mutant likewise decreased only slightly relative to wild-type protein.	RESULTS
7	32	conservative substitution	experimental_method	A more conservative substitution of these five residues (251–255) with an unrelated sequence capable of backbone-mediated hydrogen bonds (STVVP>NLALA) confirmed the subtle impact of this versatile inter-RRM sequence on affinity for the AdML Py tract.	RESULTS
57	64	251–255	residue_range	A more conservative substitution of these five residues (251–255) with an unrelated sequence capable of backbone-mediated hydrogen bonds (STVVP>NLALA) confirmed the subtle impact of this versatile inter-RRM sequence on affinity for the AdML Py tract.	RESULTS
122	136	hydrogen bonds	bond_interaction	A more conservative substitution of these five residues (251–255) with an unrelated sequence capable of backbone-mediated hydrogen bonds (STVVP>NLALA) confirmed the subtle impact of this versatile inter-RRM sequence on affinity for the AdML Py tract.	RESULTS
138	149	STVVP>NLALA	mutant	A more conservative substitution of these five residues (251–255) with an unrelated sequence capable of backbone-mediated hydrogen bonds (STVVP>NLALA) confirmed the subtle impact of this versatile inter-RRM sequence on affinity for the AdML Py tract.	RESULTS
197	215	inter-RRM sequence	structure_element	A more conservative substitution of these five residues (251–255) with an unrelated sequence capable of backbone-mediated hydrogen bonds (STVVP>NLALA) confirmed the subtle impact of this versatile inter-RRM sequence on affinity for the AdML Py tract.	RESULTS
219	227	affinity	evidence	A more conservative substitution of these five residues (251–255) with an unrelated sequence capable of backbone-mediated hydrogen bonds (STVVP>NLALA) confirmed the subtle impact of this versatile inter-RRM sequence on affinity for the AdML Py tract.	RESULTS
236	240	AdML	gene	A more conservative substitution of these five residues (251–255) with an unrelated sequence capable of backbone-mediated hydrogen bonds (STVVP>NLALA) confirmed the subtle impact of this versatile inter-RRM sequence on affinity for the AdML Py tract.	RESULTS
241	249	Py tract	chemical	A more conservative substitution of these five residues (251–255) with an unrelated sequence capable of backbone-mediated hydrogen bonds (STVVP>NLALA) confirmed the subtle impact of this versatile inter-RRM sequence on affinity for the AdML Py tract.	RESULTS
81	87	linker	structure_element	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
88	91	RRM	structure_element	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
105	116	substituted	experimental_method	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
117	124	glycine	residue_name	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
180	196	inter-RRM linker	structure_element	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
208	212	M144	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
214	218	L235	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
220	224	M238	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
226	230	V244	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
232	236	V246	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
238	242	V249	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
244	248	V250	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
250	254	S251	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
256	260	T252	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
262	266	V253	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
268	272	V254	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
274	278	P255	residue_name_number	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
287	292	12Gly	mutant	Finally, to ensure that these selective mutations were sufficient to disrupt the linker/RRM contacts, we substituted glycine for the majority of buried hydrophobic residues in the inter-RRM linker (including M144, L235, M238, V244, V246, V249, V250, S251, T252, V253, V254, P255; called 12Gly).	RESULTS
8	31	12 concurrent mutations	experimental_method	Despite 12 concurrent mutations, the AdML RNA affinity of the U2AF651,2L-12Gly variant was reduced by only three-fold relative to the unmodified protein (Fig. 4b), which is less than the penalty of the V254P mutation that disrupts the rU5 hydrogen bond (Fig. 3d,i).	RESULTS
37	41	AdML	gene	Despite 12 concurrent mutations, the AdML RNA affinity of the U2AF651,2L-12Gly variant was reduced by only three-fold relative to the unmodified protein (Fig. 4b), which is less than the penalty of the V254P mutation that disrupts the rU5 hydrogen bond (Fig. 3d,i).	RESULTS
42	54	RNA affinity	evidence	Despite 12 concurrent mutations, the AdML RNA affinity of the U2AF651,2L-12Gly variant was reduced by only three-fold relative to the unmodified protein (Fig. 4b), which is less than the penalty of the V254P mutation that disrupts the rU5 hydrogen bond (Fig. 3d,i).	RESULTS
62	78	U2AF651,2L-12Gly	mutant	Despite 12 concurrent mutations, the AdML RNA affinity of the U2AF651,2L-12Gly variant was reduced by only three-fold relative to the unmodified protein (Fig. 4b), which is less than the penalty of the V254P mutation that disrupts the rU5 hydrogen bond (Fig. 3d,i).	RESULTS
79	86	variant	protein_state	Despite 12 concurrent mutations, the AdML RNA affinity of the U2AF651,2L-12Gly variant was reduced by only three-fold relative to the unmodified protein (Fig. 4b), which is less than the penalty of the V254P mutation that disrupts the rU5 hydrogen bond (Fig. 3d,i).	RESULTS
134	144	unmodified	protein_state	Despite 12 concurrent mutations, the AdML RNA affinity of the U2AF651,2L-12Gly variant was reduced by only three-fold relative to the unmodified protein (Fig. 4b), which is less than the penalty of the V254P mutation that disrupts the rU5 hydrogen bond (Fig. 3d,i).	RESULTS
145	152	protein	protein	Despite 12 concurrent mutations, the AdML RNA affinity of the U2AF651,2L-12Gly variant was reduced by only three-fold relative to the unmodified protein (Fig. 4b), which is less than the penalty of the V254P mutation that disrupts the rU5 hydrogen bond (Fig. 3d,i).	RESULTS
202	207	V254P	mutant	Despite 12 concurrent mutations, the AdML RNA affinity of the U2AF651,2L-12Gly variant was reduced by only three-fold relative to the unmodified protein (Fig. 4b), which is less than the penalty of the V254P mutation that disrupts the rU5 hydrogen bond (Fig. 3d,i).	RESULTS
235	238	rU5	residue_name_number	Despite 12 concurrent mutations, the AdML RNA affinity of the U2AF651,2L-12Gly variant was reduced by only three-fold relative to the unmodified protein (Fig. 4b), which is less than the penalty of the V254P mutation that disrupts the rU5 hydrogen bond (Fig. 3d,i).	RESULTS
239	252	hydrogen bond	bond_interaction	Despite 12 concurrent mutations, the AdML RNA affinity of the U2AF651,2L-12Gly variant was reduced by only three-fold relative to the unmodified protein (Fig. 4b), which is less than the penalty of the V254P mutation that disrupts the rU5 hydrogen bond (Fig. 3d,i).	RESULTS
29	35	U2AF65	protein	To test the interplay of the U2AF65 inter-RRM linker with its N- and C-terminal RRM extensions, we constructed an internal linker deletion of 20-residues within the extended RNA-binding domain (dU2AF651,2L).	RESULTS
36	52	inter-RRM linker	structure_element	To test the interplay of the U2AF65 inter-RRM linker with its N- and C-terminal RRM extensions, we constructed an internal linker deletion of 20-residues within the extended RNA-binding domain (dU2AF651,2L).	RESULTS
80	94	RRM extensions	structure_element	To test the interplay of the U2AF65 inter-RRM linker with its N- and C-terminal RRM extensions, we constructed an internal linker deletion of 20-residues within the extended RNA-binding domain (dU2AF651,2L).	RESULTS
99	110	constructed	experimental_method	To test the interplay of the U2AF65 inter-RRM linker with its N- and C-terminal RRM extensions, we constructed an internal linker deletion of 20-residues within the extended RNA-binding domain (dU2AF651,2L).	RESULTS
123	138	linker deletion	experimental_method	To test the interplay of the U2AF65 inter-RRM linker with its N- and C-terminal RRM extensions, we constructed an internal linker deletion of 20-residues within the extended RNA-binding domain (dU2AF651,2L).	RESULTS
142	153	20-residues	residue_range	To test the interplay of the U2AF65 inter-RRM linker with its N- and C-terminal RRM extensions, we constructed an internal linker deletion of 20-residues within the extended RNA-binding domain (dU2AF651,2L).	RESULTS
165	173	extended	protein_state	To test the interplay of the U2AF65 inter-RRM linker with its N- and C-terminal RRM extensions, we constructed an internal linker deletion of 20-residues within the extended RNA-binding domain (dU2AF651,2L).	RESULTS
174	192	RNA-binding domain	structure_element	To test the interplay of the U2AF65 inter-RRM linker with its N- and C-terminal RRM extensions, we constructed an internal linker deletion of 20-residues within the extended RNA-binding domain (dU2AF651,2L).	RESULTS
194	205	dU2AF651,2L	mutant	To test the interplay of the U2AF65 inter-RRM linker with its N- and C-terminal RRM extensions, we constructed an internal linker deletion of 20-residues within the extended RNA-binding domain (dU2AF651,2L).	RESULTS
18	26	affinity	evidence	We found that the affinity of dU2AF651,2L for the AdML RNA was significantly reduced relative to U2AF651,2L (four-fold, Figs 1b and 4b; Supplementary Fig. 4i).	RESULTS
30	41	dU2AF651,2L	mutant	We found that the affinity of dU2AF651,2L for the AdML RNA was significantly reduced relative to U2AF651,2L (four-fold, Figs 1b and 4b; Supplementary Fig. 4i).	RESULTS
50	54	AdML	gene	We found that the affinity of dU2AF651,2L for the AdML RNA was significantly reduced relative to U2AF651,2L (four-fold, Figs 1b and 4b; Supplementary Fig. 4i).	RESULTS
55	58	RNA	chemical	We found that the affinity of dU2AF651,2L for the AdML RNA was significantly reduced relative to U2AF651,2L (four-fold, Figs 1b and 4b; Supplementary Fig. 4i).	RESULTS
97	107	U2AF651,2L	mutant	We found that the affinity of dU2AF651,2L for the AdML RNA was significantly reduced relative to U2AF651,2L (four-fold, Figs 1b and 4b; Supplementary Fig. 4i).	RESULTS
31	46	linker deletion	experimental_method	Yet, it is well known that the linker deletion in the context of the minimal RRM1–RRM2 boundaries has no detectable effect on the RNA affinities of dU2AF651,2 compared with U2AF651,2 (refs; Figs 1b and 4b; Supplementary Fig. 4j).	RESULTS
69	76	minimal	protein_state	Yet, it is well known that the linker deletion in the context of the minimal RRM1–RRM2 boundaries has no detectable effect on the RNA affinities of dU2AF651,2 compared with U2AF651,2 (refs; Figs 1b and 4b; Supplementary Fig. 4j).	RESULTS
77	81	RRM1	structure_element	Yet, it is well known that the linker deletion in the context of the minimal RRM1–RRM2 boundaries has no detectable effect on the RNA affinities of dU2AF651,2 compared with U2AF651,2 (refs; Figs 1b and 4b; Supplementary Fig. 4j).	RESULTS
82	86	RRM2	structure_element	Yet, it is well known that the linker deletion in the context of the minimal RRM1–RRM2 boundaries has no detectable effect on the RNA affinities of dU2AF651,2 compared with U2AF651,2 (refs; Figs 1b and 4b; Supplementary Fig. 4j).	RESULTS
130	144	RNA affinities	evidence	Yet, it is well known that the linker deletion in the context of the minimal RRM1–RRM2 boundaries has no detectable effect on the RNA affinities of dU2AF651,2 compared with U2AF651,2 (refs; Figs 1b and 4b; Supplementary Fig. 4j).	RESULTS
148	158	dU2AF651,2	mutant	Yet, it is well known that the linker deletion in the context of the minimal RRM1–RRM2 boundaries has no detectable effect on the RNA affinities of dU2AF651,2 compared with U2AF651,2 (refs; Figs 1b and 4b; Supplementary Fig. 4j).	RESULTS
173	182	U2AF651,2	mutant	Yet, it is well known that the linker deletion in the context of the minimal RRM1–RRM2 boundaries has no detectable effect on the RNA affinities of dU2AF651,2 compared with U2AF651,2 (refs; Figs 1b and 4b; Supplementary Fig. 4j).	RESULTS
4	14	U2AF651,2L	mutant	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
15	25	structures	evidence	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
42	63	extended conformation	protein_state	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
71	80	truncated	protein_state	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
81	91	dU2AF651,2	mutant	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
92	108	inter-RRM linker	structure_element	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
138	148	U2AF651,2L	mutant	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
149	153	RRM1	structure_element	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
186	190	RRM2	structure_element	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
214	224	U2AF651,2L	mutant	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
225	229	R227	residue_name_number	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
233	237	H259	residue_name_number	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
279	293	RNA affinities	evidence	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
297	307	dU2AF651,2	mutant	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
312	321	U2AF651,2	mutant	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
322	326	dual	protein_state	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
327	331	RRMs	structure_element	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
350	360	individual	protein_state	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
361	367	U2AF65	protein	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
368	372	RRMs	structure_element	The U2AF651,2L structures suggest that an extended conformation of the truncated dU2AF651,2 inter-RRM linker would suffice to connect the U2AF651,2L RRM1 C terminus to the N terminus of RRM2 (24 Å distance between U2AF651,2L R227-Cα–H259-Cα atoms), which agrees with the greater RNA affinities of dU2AF651,2 and U2AF651,2 dual RRMs compared with the individual U2AF65 RRMs.	RESULTS
27	36	truncated	protein_state	However, stretching of the truncated dU2AF651,2L linker to connect the RRM termini is expected to disrupt its nucleotide interactions.	RESULTS
37	48	dU2AF651,2L	mutant	However, stretching of the truncated dU2AF651,2L linker to connect the RRM termini is expected to disrupt its nucleotide interactions.	RESULTS
49	55	linker	structure_element	However, stretching of the truncated dU2AF651,2L linker to connect the RRM termini is expected to disrupt its nucleotide interactions.	RESULTS
71	82	RRM termini	structure_element	However, stretching of the truncated dU2AF651,2L linker to connect the RRM termini is expected to disrupt its nucleotide interactions.	RESULTS
10	18	deletion	experimental_method	Likewise, deletion of the N-terminal RRM1 extension in the shortened constructs would remove packing interactions that position the linker in a kinked turn following P229 (Fig. 4a), consistent with the lower RNA affinities of dU2AF651,2L, dU2AF651,2 and U2AF651,2 compared with U2AF651,2L.	RESULTS
37	51	RRM1 extension	structure_element	Likewise, deletion of the N-terminal RRM1 extension in the shortened constructs would remove packing interactions that position the linker in a kinked turn following P229 (Fig. 4a), consistent with the lower RNA affinities of dU2AF651,2L, dU2AF651,2 and U2AF651,2 compared with U2AF651,2L.	RESULTS
59	68	shortened	protein_state	Likewise, deletion of the N-terminal RRM1 extension in the shortened constructs would remove packing interactions that position the linker in a kinked turn following P229 (Fig. 4a), consistent with the lower RNA affinities of dU2AF651,2L, dU2AF651,2 and U2AF651,2 compared with U2AF651,2L.	RESULTS
132	138	linker	structure_element	Likewise, deletion of the N-terminal RRM1 extension in the shortened constructs would remove packing interactions that position the linker in a kinked turn following P229 (Fig. 4a), consistent with the lower RNA affinities of dU2AF651,2L, dU2AF651,2 and U2AF651,2 compared with U2AF651,2L.	RESULTS
144	155	kinked turn	structure_element	Likewise, deletion of the N-terminal RRM1 extension in the shortened constructs would remove packing interactions that position the linker in a kinked turn following P229 (Fig. 4a), consistent with the lower RNA affinities of dU2AF651,2L, dU2AF651,2 and U2AF651,2 compared with U2AF651,2L.	RESULTS
166	170	P229	residue_name_number	Likewise, deletion of the N-terminal RRM1 extension in the shortened constructs would remove packing interactions that position the linker in a kinked turn following P229 (Fig. 4a), consistent with the lower RNA affinities of dU2AF651,2L, dU2AF651,2 and U2AF651,2 compared with U2AF651,2L.	RESULTS
208	222	RNA affinities	evidence	Likewise, deletion of the N-terminal RRM1 extension in the shortened constructs would remove packing interactions that position the linker in a kinked turn following P229 (Fig. 4a), consistent with the lower RNA affinities of dU2AF651,2L, dU2AF651,2 and U2AF651,2 compared with U2AF651,2L.	RESULTS
226	237	dU2AF651,2L	mutant	Likewise, deletion of the N-terminal RRM1 extension in the shortened constructs would remove packing interactions that position the linker in a kinked turn following P229 (Fig. 4a), consistent with the lower RNA affinities of dU2AF651,2L, dU2AF651,2 and U2AF651,2 compared with U2AF651,2L.	RESULTS
239	249	dU2AF651,2	mutant	Likewise, deletion of the N-terminal RRM1 extension in the shortened constructs would remove packing interactions that position the linker in a kinked turn following P229 (Fig. 4a), consistent with the lower RNA affinities of dU2AF651,2L, dU2AF651,2 and U2AF651,2 compared with U2AF651,2L.	RESULTS
254	263	U2AF651,2	mutant	Likewise, deletion of the N-terminal RRM1 extension in the shortened constructs would remove packing interactions that position the linker in a kinked turn following P229 (Fig. 4a), consistent with the lower RNA affinities of dU2AF651,2L, dU2AF651,2 and U2AF651,2 compared with U2AF651,2L.	RESULTS
278	288	U2AF651,2L	mutant	Likewise, deletion of the N-terminal RRM1 extension in the shortened constructs would remove packing interactions that position the linker in a kinked turn following P229 (Fig. 4a), consistent with the lower RNA affinities of dU2AF651,2L, dU2AF651,2 and U2AF651,2 compared with U2AF651,2L.	RESULTS
38	44	U2AF65	protein	To further test cooperation among the U2AF65 RRM extensions and inter-RRM linker for RNA recognition, we tested the impact of a triple Q147A/V254P/R227A mutation (U2AF651,2L-3Mut) for RNA binding (Fig. 4b; Supplementary Fig. 4d).	RESULTS
45	59	RRM extensions	structure_element	To further test cooperation among the U2AF65 RRM extensions and inter-RRM linker for RNA recognition, we tested the impact of a triple Q147A/V254P/R227A mutation (U2AF651,2L-3Mut) for RNA binding (Fig. 4b; Supplementary Fig. 4d).	RESULTS
64	80	inter-RRM linker	structure_element	To further test cooperation among the U2AF65 RRM extensions and inter-RRM linker for RNA recognition, we tested the impact of a triple Q147A/V254P/R227A mutation (U2AF651,2L-3Mut) for RNA binding (Fig. 4b; Supplementary Fig. 4d).	RESULTS
135	140	Q147A	mutant	To further test cooperation among the U2AF65 RRM extensions and inter-RRM linker for RNA recognition, we tested the impact of a triple Q147A/V254P/R227A mutation (U2AF651,2L-3Mut) for RNA binding (Fig. 4b; Supplementary Fig. 4d).	RESULTS
141	146	V254P	mutant	To further test cooperation among the U2AF65 RRM extensions and inter-RRM linker for RNA recognition, we tested the impact of a triple Q147A/V254P/R227A mutation (U2AF651,2L-3Mut) for RNA binding (Fig. 4b; Supplementary Fig. 4d).	RESULTS
147	152	R227A	mutant	To further test cooperation among the U2AF65 RRM extensions and inter-RRM linker for RNA recognition, we tested the impact of a triple Q147A/V254P/R227A mutation (U2AF651,2L-3Mut) for RNA binding (Fig. 4b; Supplementary Fig. 4d).	RESULTS
153	161	mutation	experimental_method	To further test cooperation among the U2AF65 RRM extensions and inter-RRM linker for RNA recognition, we tested the impact of a triple Q147A/V254P/R227A mutation (U2AF651,2L-3Mut) for RNA binding (Fig. 4b; Supplementary Fig. 4d).	RESULTS
163	178	U2AF651,2L-3Mut	mutant	To further test cooperation among the U2AF65 RRM extensions and inter-RRM linker for RNA recognition, we tested the impact of a triple Q147A/V254P/R227A mutation (U2AF651,2L-3Mut) for RNA binding (Fig. 4b; Supplementary Fig. 4d).	RESULTS
13	18	Q147A	mutant	Notably, the Q147A/V254P/R227A mutation reduced the RNA affinity of the U2AF651,2L-3Mut protein by 30-fold more than would be expected based on simple addition of the ΔΔG's for the single mutations.	RESULTS
19	24	V254P	mutant	Notably, the Q147A/V254P/R227A mutation reduced the RNA affinity of the U2AF651,2L-3Mut protein by 30-fold more than would be expected based on simple addition of the ΔΔG's for the single mutations.	RESULTS
25	30	R227A	mutant	Notably, the Q147A/V254P/R227A mutation reduced the RNA affinity of the U2AF651,2L-3Mut protein by 30-fold more than would be expected based on simple addition of the ΔΔG's for the single mutations.	RESULTS
31	39	mutation	experimental_method	Notably, the Q147A/V254P/R227A mutation reduced the RNA affinity of the U2AF651,2L-3Mut protein by 30-fold more than would be expected based on simple addition of the ΔΔG's for the single mutations.	RESULTS
52	64	RNA affinity	evidence	Notably, the Q147A/V254P/R227A mutation reduced the RNA affinity of the U2AF651,2L-3Mut protein by 30-fold more than would be expected based on simple addition of the ΔΔG's for the single mutations.	RESULTS
72	87	U2AF651,2L-3Mut	mutant	Notably, the Q147A/V254P/R227A mutation reduced the RNA affinity of the U2AF651,2L-3Mut protein by 30-fold more than would be expected based on simple addition of the ΔΔG's for the single mutations.	RESULTS
167	170	ΔΔG	evidence	Notably, the Q147A/V254P/R227A mutation reduced the RNA affinity of the U2AF651,2L-3Mut protein by 30-fold more than would be expected based on simple addition of the ΔΔG's for the single mutations.	RESULTS
35	51	linearly distant	protein_state	This difference indicates that the linearly distant regions of the U2AF65 primary sequence, including Q147 in the N-terminal RRM1 extension and R227/V254 in the N-/C-terminal linker regions at the fifth nucleotide site, cooperatively recognize the Py tract.	RESULTS
52	59	regions	structure_element	This difference indicates that the linearly distant regions of the U2AF65 primary sequence, including Q147 in the N-terminal RRM1 extension and R227/V254 in the N-/C-terminal linker regions at the fifth nucleotide site, cooperatively recognize the Py tract.	RESULTS
67	73	U2AF65	protein	This difference indicates that the linearly distant regions of the U2AF65 primary sequence, including Q147 in the N-terminal RRM1 extension and R227/V254 in the N-/C-terminal linker regions at the fifth nucleotide site, cooperatively recognize the Py tract.	RESULTS
102	106	Q147	residue_name_number	This difference indicates that the linearly distant regions of the U2AF65 primary sequence, including Q147 in the N-terminal RRM1 extension and R227/V254 in the N-/C-terminal linker regions at the fifth nucleotide site, cooperatively recognize the Py tract.	RESULTS
125	139	RRM1 extension	structure_element	This difference indicates that the linearly distant regions of the U2AF65 primary sequence, including Q147 in the N-terminal RRM1 extension and R227/V254 in the N-/C-terminal linker regions at the fifth nucleotide site, cooperatively recognize the Py tract.	RESULTS
144	148	R227	residue_name_number	This difference indicates that the linearly distant regions of the U2AF65 primary sequence, including Q147 in the N-terminal RRM1 extension and R227/V254 in the N-/C-terminal linker regions at the fifth nucleotide site, cooperatively recognize the Py tract.	RESULTS
149	153	V254	residue_name_number	This difference indicates that the linearly distant regions of the U2AF65 primary sequence, including Q147 in the N-terminal RRM1 extension and R227/V254 in the N-/C-terminal linker regions at the fifth nucleotide site, cooperatively recognize the Py tract.	RESULTS
175	189	linker regions	structure_element	This difference indicates that the linearly distant regions of the U2AF65 primary sequence, including Q147 in the N-terminal RRM1 extension and R227/V254 in the N-/C-terminal linker regions at the fifth nucleotide site, cooperatively recognize the Py tract.	RESULTS
197	218	fifth nucleotide site	site	This difference indicates that the linearly distant regions of the U2AF65 primary sequence, including Q147 in the N-terminal RRM1 extension and R227/V254 in the N-/C-terminal linker regions at the fifth nucleotide site, cooperatively recognize the Py tract.	RESULTS
248	256	Py tract	chemical	This difference indicates that the linearly distant regions of the U2AF65 primary sequence, including Q147 in the N-terminal RRM1 extension and R227/V254 in the N-/C-terminal linker regions at the fifth nucleotide site, cooperatively recognize the Py tract.	RESULTS
53	59	U2AF65	protein	Altogether, we conclude that the conformation of the U2AF65 inter-RRM linker is key for recognizing RNA and is positioned by the RRM extension but otherwise relatively independent of the side chain composition.	RESULTS
60	76	inter-RRM linker	structure_element	Altogether, we conclude that the conformation of the U2AF65 inter-RRM linker is key for recognizing RNA and is positioned by the RRM extension but otherwise relatively independent of the side chain composition.	RESULTS
100	103	RNA	chemical	Altogether, we conclude that the conformation of the U2AF65 inter-RRM linker is key for recognizing RNA and is positioned by the RRM extension but otherwise relatively independent of the side chain composition.	RESULTS
129	142	RRM extension	structure_element	Altogether, we conclude that the conformation of the U2AF65 inter-RRM linker is key for recognizing RNA and is positioned by the RRM extension but otherwise relatively independent of the side chain composition.	RESULTS
32	37	Q147A	mutant	The non-additive effects of the Q147A/V254P/R227A triple mutation, coupled with the context-dependent penalties of an internal U2AF65 linker deletion, highlights the importance of the structural interplay among the U2AF65 linker and the N- and C-terminal extensions flanking the core RRMs.	RESULTS
38	43	V254P	mutant	The non-additive effects of the Q147A/V254P/R227A triple mutation, coupled with the context-dependent penalties of an internal U2AF65 linker deletion, highlights the importance of the structural interplay among the U2AF65 linker and the N- and C-terminal extensions flanking the core RRMs.	RESULTS
44	49	R227A	mutant	The non-additive effects of the Q147A/V254P/R227A triple mutation, coupled with the context-dependent penalties of an internal U2AF65 linker deletion, highlights the importance of the structural interplay among the U2AF65 linker and the N- and C-terminal extensions flanking the core RRMs.	RESULTS
50	65	triple mutation	experimental_method	The non-additive effects of the Q147A/V254P/R227A triple mutation, coupled with the context-dependent penalties of an internal U2AF65 linker deletion, highlights the importance of the structural interplay among the U2AF65 linker and the N- and C-terminal extensions flanking the core RRMs.	RESULTS
127	133	U2AF65	protein	The non-additive effects of the Q147A/V254P/R227A triple mutation, coupled with the context-dependent penalties of an internal U2AF65 linker deletion, highlights the importance of the structural interplay among the U2AF65 linker and the N- and C-terminal extensions flanking the core RRMs.	RESULTS
134	149	linker deletion	experimental_method	The non-additive effects of the Q147A/V254P/R227A triple mutation, coupled with the context-dependent penalties of an internal U2AF65 linker deletion, highlights the importance of the structural interplay among the U2AF65 linker and the N- and C-terminal extensions flanking the core RRMs.	RESULTS
215	221	U2AF65	protein	The non-additive effects of the Q147A/V254P/R227A triple mutation, coupled with the context-dependent penalties of an internal U2AF65 linker deletion, highlights the importance of the structural interplay among the U2AF65 linker and the N- and C-terminal extensions flanking the core RRMs.	RESULTS
222	228	linker	structure_element	The non-additive effects of the Q147A/V254P/R227A triple mutation, coupled with the context-dependent penalties of an internal U2AF65 linker deletion, highlights the importance of the structural interplay among the U2AF65 linker and the N- and C-terminal extensions flanking the core RRMs.	RESULTS
237	265	N- and C-terminal extensions	structure_element	The non-additive effects of the Q147A/V254P/R227A triple mutation, coupled with the context-dependent penalties of an internal U2AF65 linker deletion, highlights the importance of the structural interplay among the U2AF65 linker and the N- and C-terminal extensions flanking the core RRMs.	RESULTS
279	283	core	protein_state	The non-additive effects of the Q147A/V254P/R227A triple mutation, coupled with the context-dependent penalties of an internal U2AF65 linker deletion, highlights the importance of the structural interplay among the U2AF65 linker and the N- and C-terminal extensions flanking the core RRMs.	RESULTS
284	288	RRMs	structure_element	The non-additive effects of the Q147A/V254P/R227A triple mutation, coupled with the context-dependent penalties of an internal U2AF65 linker deletion, highlights the importance of the structural interplay among the U2AF65 linker and the N- and C-terminal extensions flanking the core RRMs.	RESULTS
14	24	U2AF65–RNA	complex_assembly	Importance of U2AF65–RNA contacts for pre-mRNA splicing	RESULTS
38	46	pre-mRNA	chemical	Importance of U2AF65–RNA contacts for pre-mRNA splicing	RESULTS
43	58	U2AF65–Py-tract	complex_assembly	We proceeded to test the importance of new U2AF65–Py-tract interactions for splicing of a model pre-mRNA substrate in a human cell line (Fig. 5; Supplementary Fig. 5).	RESULTS
96	104	pre-mRNA	chemical	We proceeded to test the importance of new U2AF65–Py-tract interactions for splicing of a model pre-mRNA substrate in a human cell line (Fig. 5; Supplementary Fig. 5).	RESULTS
120	125	human	species	We proceeded to test the importance of new U2AF65–Py-tract interactions for splicing of a model pre-mRNA substrate in a human cell line (Fig. 5; Supplementary Fig. 5).	RESULTS
73	99	minigene splicing reporter	chemical	As a representative splicing substrate, we utilized a well-characterized minigene splicing reporter (called pyPY) comprising a weak (that is, degenerate, py) and strong (that is, U-rich, PY) polypyrimidine tracts preceding two alternative splice sites (Fig. 5a).	RESULTS
108	112	pyPY	chemical	As a representative splicing substrate, we utilized a well-characterized minigene splicing reporter (called pyPY) comprising a weak (that is, degenerate, py) and strong (that is, U-rich, PY) polypyrimidine tracts preceding two alternative splice sites (Fig. 5a).	RESULTS
154	156	py	chemical	As a representative splicing substrate, we utilized a well-characterized minigene splicing reporter (called pyPY) comprising a weak (that is, degenerate, py) and strong (that is, U-rich, PY) polypyrimidine tracts preceding two alternative splice sites (Fig. 5a).	RESULTS
179	185	U-rich	structure_element	As a representative splicing substrate, we utilized a well-characterized minigene splicing reporter (called pyPY) comprising a weak (that is, degenerate, py) and strong (that is, U-rich, PY) polypyrimidine tracts preceding two alternative splice sites (Fig. 5a).	RESULTS
187	189	PY	chemical	As a representative splicing substrate, we utilized a well-characterized minigene splicing reporter (called pyPY) comprising a weak (that is, degenerate, py) and strong (that is, U-rich, PY) polypyrimidine tracts preceding two alternative splice sites (Fig. 5a).	RESULTS
191	212	polypyrimidine tracts	chemical	As a representative splicing substrate, we utilized a well-characterized minigene splicing reporter (called pyPY) comprising a weak (that is, degenerate, py) and strong (that is, U-rich, PY) polypyrimidine tracts preceding two alternative splice sites (Fig. 5a).	RESULTS
239	251	splice sites	site	As a representative splicing substrate, we utilized a well-characterized minigene splicing reporter (called pyPY) comprising a weak (that is, degenerate, py) and strong (that is, U-rich, PY) polypyrimidine tracts preceding two alternative splice sites (Fig. 5a).	RESULTS
5	16	transfected	experimental_method	When transfected into HEK293T cells containing only endogenous U2AF65, the PY splice site is used and the remaining transcript remains unspliced.	RESULTS
52	62	endogenous	protein_state	When transfected into HEK293T cells containing only endogenous U2AF65, the PY splice site is used and the remaining transcript remains unspliced.	RESULTS
63	69	U2AF65	protein	When transfected into HEK293T cells containing only endogenous U2AF65, the PY splice site is used and the remaining transcript remains unspliced.	RESULTS
75	89	PY splice site	site	When transfected into HEK293T cells containing only endogenous U2AF65, the PY splice site is used and the remaining transcript remains unspliced.	RESULTS
5	19	co-transfected	experimental_method	When co-transfected with an expression plasmid for wild-type U2AF65, use of the py splice site significantly increases (by more than five-fold) and as documented converts a fraction of the unspliced to spliced transcript.	RESULTS
28	46	expression plasmid	experimental_method	When co-transfected with an expression plasmid for wild-type U2AF65, use of the py splice site significantly increases (by more than five-fold) and as documented converts a fraction of the unspliced to spliced transcript.	RESULTS
51	60	wild-type	protein_state	When co-transfected with an expression plasmid for wild-type U2AF65, use of the py splice site significantly increases (by more than five-fold) and as documented converts a fraction of the unspliced to spliced transcript.	RESULTS
61	67	U2AF65	protein	When co-transfected with an expression plasmid for wild-type U2AF65, use of the py splice site significantly increases (by more than five-fold) and as documented converts a fraction of the unspliced to spliced transcript.	RESULTS
80	94	py splice site	site	When co-transfected with an expression plasmid for wild-type U2AF65, use of the py splice site significantly increases (by more than five-fold) and as documented converts a fraction of the unspliced to spliced transcript.	RESULTS
11	25	PY splice site	site	The strong PY splice site is insensitive to added U2AF65, suggesting that endogenous U2AF65 levels are sufficient to saturate this site (Supplementary Fig. 5b).	RESULTS
50	56	U2AF65	protein	The strong PY splice site is insensitive to added U2AF65, suggesting that endogenous U2AF65 levels are sufficient to saturate this site (Supplementary Fig. 5b).	RESULTS
74	84	endogenous	protein_state	The strong PY splice site is insensitive to added U2AF65, suggesting that endogenous U2AF65 levels are sufficient to saturate this site (Supplementary Fig. 5b).	RESULTS
85	91	U2AF65	protein	The strong PY splice site is insensitive to added U2AF65, suggesting that endogenous U2AF65 levels are sufficient to saturate this site (Supplementary Fig. 5b).	RESULTS
18	33	triple mutation	experimental_method	We introduced the triple mutation (V254P/R227A/Q147A) that significantly reduced U2AF651,2L association with the Py tract (Fig. 4b) in the context of full-length U2AF65 (U2AF65-3Mut).	RESULTS
35	40	V254P	mutant	We introduced the triple mutation (V254P/R227A/Q147A) that significantly reduced U2AF651,2L association with the Py tract (Fig. 4b) in the context of full-length U2AF65 (U2AF65-3Mut).	RESULTS
41	46	R227A	mutant	We introduced the triple mutation (V254P/R227A/Q147A) that significantly reduced U2AF651,2L association with the Py tract (Fig. 4b) in the context of full-length U2AF65 (U2AF65-3Mut).	RESULTS
47	52	Q147A	mutant	We introduced the triple mutation (V254P/R227A/Q147A) that significantly reduced U2AF651,2L association with the Py tract (Fig. 4b) in the context of full-length U2AF65 (U2AF65-3Mut).	RESULTS
81	91	U2AF651,2L	mutant	We introduced the triple mutation (V254P/R227A/Q147A) that significantly reduced U2AF651,2L association with the Py tract (Fig. 4b) in the context of full-length U2AF65 (U2AF65-3Mut).	RESULTS
113	121	Py tract	chemical	We introduced the triple mutation (V254P/R227A/Q147A) that significantly reduced U2AF651,2L association with the Py tract (Fig. 4b) in the context of full-length U2AF65 (U2AF65-3Mut).	RESULTS
150	161	full-length	protein_state	We introduced the triple mutation (V254P/R227A/Q147A) that significantly reduced U2AF651,2L association with the Py tract (Fig. 4b) in the context of full-length U2AF65 (U2AF65-3Mut).	RESULTS
162	168	U2AF65	protein	We introduced the triple mutation (V254P/R227A/Q147A) that significantly reduced U2AF651,2L association with the Py tract (Fig. 4b) in the context of full-length U2AF65 (U2AF65-3Mut).	RESULTS
170	181	U2AF65-3Mut	mutant	We introduced the triple mutation (V254P/R227A/Q147A) that significantly reduced U2AF651,2L association with the Py tract (Fig. 4b) in the context of full-length U2AF65 (U2AF65-3Mut).	RESULTS
0	15	Co-transfection	experimental_method	Co-transfection of the U2AF65-3Mut with the pyPY splicing substrate significantly reduced splicing of the weak ‘py' splice site relative to wild-type U2AF65 (Fig. 5b,c).	RESULTS
23	34	U2AF65-3Mut	mutant	Co-transfection of the U2AF65-3Mut with the pyPY splicing substrate significantly reduced splicing of the weak ‘py' splice site relative to wild-type U2AF65 (Fig. 5b,c).	RESULTS
44	48	pyPY	chemical	Co-transfection of the U2AF65-3Mut with the pyPY splicing substrate significantly reduced splicing of the weak ‘py' splice site relative to wild-type U2AF65 (Fig. 5b,c).	RESULTS
111	127	‘py' splice site	site	Co-transfection of the U2AF65-3Mut with the pyPY splicing substrate significantly reduced splicing of the weak ‘py' splice site relative to wild-type U2AF65 (Fig. 5b,c).	RESULTS
140	149	wild-type	protein_state	Co-transfection of the U2AF65-3Mut with the pyPY splicing substrate significantly reduced splicing of the weak ‘py' splice site relative to wild-type U2AF65 (Fig. 5b,c).	RESULTS
150	156	U2AF65	protein	Co-transfection of the U2AF65-3Mut with the pyPY splicing substrate significantly reduced splicing of the weak ‘py' splice site relative to wild-type U2AF65 (Fig. 5b,c).	RESULTS
21	29	Py-tract	chemical	We conclude that the Py-tract interactions with these residues of the U2AF65 inter-RRM linker and RRM extensions are important for splicing as well as for binding a representative of the major U2-class of splice sites.	RESULTS
70	76	U2AF65	protein	We conclude that the Py-tract interactions with these residues of the U2AF65 inter-RRM linker and RRM extensions are important for splicing as well as for binding a representative of the major U2-class of splice sites.	RESULTS
77	93	inter-RRM linker	structure_element	We conclude that the Py-tract interactions with these residues of the U2AF65 inter-RRM linker and RRM extensions are important for splicing as well as for binding a representative of the major U2-class of splice sites.	RESULTS
98	112	RRM extensions	structure_element	We conclude that the Py-tract interactions with these residues of the U2AF65 inter-RRM linker and RRM extensions are important for splicing as well as for binding a representative of the major U2-class of splice sites.	RESULTS
187	217	major U2-class of splice sites	structure_element	We conclude that the Py-tract interactions with these residues of the U2AF65 inter-RRM linker and RRM extensions are important for splicing as well as for binding a representative of the major U2-class of splice sites.	RESULTS
7	16	inter-RRM	structure_element	Sparse inter-RRM contacts underlie apo-U2AF65 dynamics	RESULTS
35	38	apo	protein_state	Sparse inter-RRM contacts underlie apo-U2AF65 dynamics	RESULTS
39	45	U2AF65	protein	Sparse inter-RRM contacts underlie apo-U2AF65 dynamics	RESULTS
11	20	interface	site	The direct interface between U2AF651,2L RRM1 and RRM2 is minor, burying 265 Å2 of solvent accessible surface area compared with 570 Å2 on average for a crystal packing interface.	RESULTS
29	39	U2AF651,2L	mutant	The direct interface between U2AF651,2L RRM1 and RRM2 is minor, burying 265 Å2 of solvent accessible surface area compared with 570 Å2 on average for a crystal packing interface.	RESULTS
40	44	RRM1	structure_element	The direct interface between U2AF651,2L RRM1 and RRM2 is minor, burying 265 Å2 of solvent accessible surface area compared with 570 Å2 on average for a crystal packing interface.	RESULTS
49	53	RRM2	structure_element	The direct interface between U2AF651,2L RRM1 and RRM2 is minor, burying 265 Å2 of solvent accessible surface area compared with 570 Å2 on average for a crystal packing interface.	RESULTS
13	22	inter-RRM	structure_element	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
23	37	hydrogen bonds	bond_interaction	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
78	82	RRM1	structure_element	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
83	87	N155	residue_name_number	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
92	96	RRM2	structure_element	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
97	101	K292	residue_name_number	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
103	107	RRM1	structure_element	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
108	112	N155	residue_name_number	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
117	121	RRM2	structure_element	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
122	126	D272	residue_name_number	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
160	164	RRM1	structure_element	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
165	169	G221	residue_name_number	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
174	178	RRM2	structure_element	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
179	183	D273	residue_name_number	A handful of inter-RRM hydrogen bonds are apparent between the side chains of RRM1-N155 and RRM2-K292, RRM1-N155 and RRM2-D272 as well as the backbone atoms of RRM1-G221 and RRM2-D273 (Fig. 4c).	RESULTS
11	17	U2AF65	protein	This minor U2AF65 RRM1/RRM2 interface, coupled with the versatile sequence of the inter-RRM linker, highlighted the potential role for inter-RRM conformational dynamics in U2AF65-splice site recognition.	RESULTS
18	37	RRM1/RRM2 interface	site	This minor U2AF65 RRM1/RRM2 interface, coupled with the versatile sequence of the inter-RRM linker, highlighted the potential role for inter-RRM conformational dynamics in U2AF65-splice site recognition.	RESULTS
82	98	inter-RRM linker	structure_element	This minor U2AF65 RRM1/RRM2 interface, coupled with the versatile sequence of the inter-RRM linker, highlighted the potential role for inter-RRM conformational dynamics in U2AF65-splice site recognition.	RESULTS
135	144	inter-RRM	structure_element	This minor U2AF65 RRM1/RRM2 interface, coupled with the versatile sequence of the inter-RRM linker, highlighted the potential role for inter-RRM conformational dynamics in U2AF65-splice site recognition.	RESULTS
172	178	U2AF65	protein	This minor U2AF65 RRM1/RRM2 interface, coupled with the versatile sequence of the inter-RRM linker, highlighted the potential role for inter-RRM conformational dynamics in U2AF65-splice site recognition.	RESULTS
0	34	Paramagnetic resonance enhancement	experimental_method	Paramagnetic resonance enhancement (PRE) measurements previously had suggested a predominant back-to-back, or ‘closed' conformation of the apo-U2AF651,2 RRM1 and RRM2 in equilibrium with a minor ‘open' conformation resembling the RNA-bound inter-RRM arrangement.	RESULTS
36	39	PRE	experimental_method	Paramagnetic resonance enhancement (PRE) measurements previously had suggested a predominant back-to-back, or ‘closed' conformation of the apo-U2AF651,2 RRM1 and RRM2 in equilibrium with a minor ‘open' conformation resembling the RNA-bound inter-RRM arrangement.	RESULTS
93	105	back-to-back	protein_state	Paramagnetic resonance enhancement (PRE) measurements previously had suggested a predominant back-to-back, or ‘closed' conformation of the apo-U2AF651,2 RRM1 and RRM2 in equilibrium with a minor ‘open' conformation resembling the RNA-bound inter-RRM arrangement.	RESULTS
111	117	closed	protein_state	Paramagnetic resonance enhancement (PRE) measurements previously had suggested a predominant back-to-back, or ‘closed' conformation of the apo-U2AF651,2 RRM1 and RRM2 in equilibrium with a minor ‘open' conformation resembling the RNA-bound inter-RRM arrangement.	RESULTS
139	142	apo	protein_state	Paramagnetic resonance enhancement (PRE) measurements previously had suggested a predominant back-to-back, or ‘closed' conformation of the apo-U2AF651,2 RRM1 and RRM2 in equilibrium with a minor ‘open' conformation resembling the RNA-bound inter-RRM arrangement.	RESULTS
143	152	U2AF651,2	mutant	Paramagnetic resonance enhancement (PRE) measurements previously had suggested a predominant back-to-back, or ‘closed' conformation of the apo-U2AF651,2 RRM1 and RRM2 in equilibrium with a minor ‘open' conformation resembling the RNA-bound inter-RRM arrangement.	RESULTS
153	157	RRM1	structure_element	Paramagnetic resonance enhancement (PRE) measurements previously had suggested a predominant back-to-back, or ‘closed' conformation of the apo-U2AF651,2 RRM1 and RRM2 in equilibrium with a minor ‘open' conformation resembling the RNA-bound inter-RRM arrangement.	RESULTS
162	166	RRM2	structure_element	Paramagnetic resonance enhancement (PRE) measurements previously had suggested a predominant back-to-back, or ‘closed' conformation of the apo-U2AF651,2 RRM1 and RRM2 in equilibrium with a minor ‘open' conformation resembling the RNA-bound inter-RRM arrangement.	RESULTS
196	200	open	protein_state	Paramagnetic resonance enhancement (PRE) measurements previously had suggested a predominant back-to-back, or ‘closed' conformation of the apo-U2AF651,2 RRM1 and RRM2 in equilibrium with a minor ‘open' conformation resembling the RNA-bound inter-RRM arrangement.	RESULTS
230	239	RNA-bound	protein_state	Paramagnetic resonance enhancement (PRE) measurements previously had suggested a predominant back-to-back, or ‘closed' conformation of the apo-U2AF651,2 RRM1 and RRM2 in equilibrium with a minor ‘open' conformation resembling the RNA-bound inter-RRM arrangement.	RESULTS
240	249	inter-RRM	structure_element	Paramagnetic resonance enhancement (PRE) measurements previously had suggested a predominant back-to-back, or ‘closed' conformation of the apo-U2AF651,2 RRM1 and RRM2 in equilibrium with a minor ‘open' conformation resembling the RNA-bound inter-RRM arrangement.	RESULTS
5	33	small-angle X-ray scattering	experimental_method	Yet, small-angle X-ray scattering (SAXS) data indicated that both the minimal U2AF651,2 and longer constructs comprise a highly diverse continuum of conformations in the absence of RNA that includes the ‘closed' and ‘open' conformations.	RESULTS
35	39	SAXS	experimental_method	Yet, small-angle X-ray scattering (SAXS) data indicated that both the minimal U2AF651,2 and longer constructs comprise a highly diverse continuum of conformations in the absence of RNA that includes the ‘closed' and ‘open' conformations.	RESULTS
70	77	minimal	protein_state	Yet, small-angle X-ray scattering (SAXS) data indicated that both the minimal U2AF651,2 and longer constructs comprise a highly diverse continuum of conformations in the absence of RNA that includes the ‘closed' and ‘open' conformations.	RESULTS
78	87	U2AF651,2	mutant	Yet, small-angle X-ray scattering (SAXS) data indicated that both the minimal U2AF651,2 and longer constructs comprise a highly diverse continuum of conformations in the absence of RNA that includes the ‘closed' and ‘open' conformations.	RESULTS
121	162	highly diverse continuum of conformations	protein_state	Yet, small-angle X-ray scattering (SAXS) data indicated that both the minimal U2AF651,2 and longer constructs comprise a highly diverse continuum of conformations in the absence of RNA that includes the ‘closed' and ‘open' conformations.	RESULTS
170	180	absence of	protein_state	Yet, small-angle X-ray scattering (SAXS) data indicated that both the minimal U2AF651,2 and longer constructs comprise a highly diverse continuum of conformations in the absence of RNA that includes the ‘closed' and ‘open' conformations.	RESULTS
181	184	RNA	chemical	Yet, small-angle X-ray scattering (SAXS) data indicated that both the minimal U2AF651,2 and longer constructs comprise a highly diverse continuum of conformations in the absence of RNA that includes the ‘closed' and ‘open' conformations.	RESULTS
204	210	closed	protein_state	Yet, small-angle X-ray scattering (SAXS) data indicated that both the minimal U2AF651,2 and longer constructs comprise a highly diverse continuum of conformations in the absence of RNA that includes the ‘closed' and ‘open' conformations.	RESULTS
217	221	open	protein_state	Yet, small-angle X-ray scattering (SAXS) data indicated that both the minimal U2AF651,2 and longer constructs comprise a highly diverse continuum of conformations in the absence of RNA that includes the ‘closed' and ‘open' conformations.	RESULTS
38	48	U2AF651,2L	mutant	To complement the static portraits of U2AF651,2L structure that we had determined by X-ray crystallography, we used smFRET to characterize the probability distribution functions and time dependence of U2AF65 inter-RRM conformational dynamics in solution.	RESULTS
49	58	structure	evidence	To complement the static portraits of U2AF651,2L structure that we had determined by X-ray crystallography, we used smFRET to characterize the probability distribution functions and time dependence of U2AF65 inter-RRM conformational dynamics in solution.	RESULTS
85	106	X-ray crystallography	experimental_method	To complement the static portraits of U2AF651,2L structure that we had determined by X-ray crystallography, we used smFRET to characterize the probability distribution functions and time dependence of U2AF65 inter-RRM conformational dynamics in solution.	RESULTS
116	122	smFRET	experimental_method	To complement the static portraits of U2AF651,2L structure that we had determined by X-ray crystallography, we used smFRET to characterize the probability distribution functions and time dependence of U2AF65 inter-RRM conformational dynamics in solution.	RESULTS
143	177	probability distribution functions	evidence	To complement the static portraits of U2AF651,2L structure that we had determined by X-ray crystallography, we used smFRET to characterize the probability distribution functions and time dependence of U2AF65 inter-RRM conformational dynamics in solution.	RESULTS
201	207	U2AF65	protein	To complement the static portraits of U2AF651,2L structure that we had determined by X-ray crystallography, we used smFRET to characterize the probability distribution functions and time dependence of U2AF65 inter-RRM conformational dynamics in solution.	RESULTS
208	217	inter-RRM	structure_element	To complement the static portraits of U2AF651,2L structure that we had determined by X-ray crystallography, we used smFRET to characterize the probability distribution functions and time dependence of U2AF65 inter-RRM conformational dynamics in solution.	RESULTS
4	13	inter-RRM	structure_element	The inter-RRM dynamics of U2AF65 were followed using FRET between fluorophores attached to RRM1 and RRM2 (Fig. 6a,b, Methods).	RESULTS
26	32	U2AF65	protein	The inter-RRM dynamics of U2AF65 were followed using FRET between fluorophores attached to RRM1 and RRM2 (Fig. 6a,b, Methods).	RESULTS
53	57	FRET	experimental_method	The inter-RRM dynamics of U2AF65 were followed using FRET between fluorophores attached to RRM1 and RRM2 (Fig. 6a,b, Methods).	RESULTS
66	78	fluorophores	chemical	The inter-RRM dynamics of U2AF65 were followed using FRET between fluorophores attached to RRM1 and RRM2 (Fig. 6a,b, Methods).	RESULTS
91	95	RRM1	structure_element	The inter-RRM dynamics of U2AF65 were followed using FRET between fluorophores attached to RRM1 and RRM2 (Fig. 6a,b, Methods).	RESULTS
100	104	RRM2	structure_element	The inter-RRM dynamics of U2AF65 were followed using FRET between fluorophores attached to RRM1 and RRM2 (Fig. 6a,b, Methods).	RESULTS
24	32	cysteine	residue_name	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
33	42	mutations	experimental_method	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
47	58	fluorophore	chemical	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
71	76	A181C	mutant	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
80	84	RRM1	structure_element	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
89	94	Q324C	mutant	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
98	102	RRM2	structure_element	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
143	153	U2AF651,2L	mutant	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
154	164	structures	evidence	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
174	180	closed	protein_state	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
191	194	apo	protein_state	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
195	204	U2AF651,2	mutant	The positions of single cysteine mutations for fluorophore attachment (A181C in RRM1 and Q324C in RRM2) were chosen based on inspection of the U2AF651,2L structures and the ‘closed' model of apo-U2AF651,2.	RESULTS
107	114	RRM/RNA	complex_assembly	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
118	138	inter-RRM interfaces	site	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
175	194	U2AF651,2L–Py tract	complex_assembly	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
212	218	closed	protein_state	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
219	222	apo	protein_state	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
263	282	Förster radius (Ro)	experimental_method	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
291	294	Cy3	chemical	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
295	298	Cy5	chemical	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
405	422	FRET efficiencies	evidence	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
480	486	closed	protein_state	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
488	491	apo	protein_state	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
517	521	open	protein_state	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
523	532	RNA-bound	protein_state	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
533	543	structures	evidence	Criteria included (i) residue locations that are distant from and hence not expected to interfere with the RRM/RNA or inter-RRM interfaces, (ii) inter-dye distances (50 Å for U2AF651,2L–Py tract and 30 Å for the closed apo-model) that are expected to be near the Förster radius (Ro) for the Cy3/Cy5 pair (56 Å), where changes in the efficiency of energy transfer are most sensitive to distance, and (iii) FRET efficiencies that are calculated to be significantly greater for the ‘closed' apo-model as opposed to the ‘open' RNA-bound structures (by ∼30%).	RESULTS
4	21	FRET efficiencies	evidence	The FRET efficiencies of either of these structurally characterized conformations also are expected to be significantly greater than elongated U2AF65 conformations that lack inter-RRM contacts.	RESULTS
133	142	elongated	protein_state	The FRET efficiencies of either of these structurally characterized conformations also are expected to be significantly greater than elongated U2AF65 conformations that lack inter-RRM contacts.	RESULTS
143	149	U2AF65	protein	The FRET efficiencies of either of these structurally characterized conformations also are expected to be significantly greater than elongated U2AF65 conformations that lack inter-RRM contacts.	RESULTS
169	173	lack	protein_state	The FRET efficiencies of either of these structurally characterized conformations also are expected to be significantly greater than elongated U2AF65 conformations that lack inter-RRM contacts.	RESULTS
180	183	RRM	structure_element	The FRET efficiencies of either of these structurally characterized conformations also are expected to be significantly greater than elongated U2AF65 conformations that lack inter-RRM contacts.	RESULTS
7	15	cysteine	residue_name	Double-cysteine variant of U2AF651,2 was modified with equimolar amount of Cy3 and Cy5.	RESULTS
16	23	variant	protein_state	Double-cysteine variant of U2AF651,2 was modified with equimolar amount of Cy3 and Cy5.	RESULTS
27	36	U2AF651,2	mutant	Double-cysteine variant of U2AF651,2 was modified with equimolar amount of Cy3 and Cy5.	RESULTS
41	49	modified	experimental_method	Double-cysteine variant of U2AF651,2 was modified with equimolar amount of Cy3 and Cy5.	RESULTS
75	78	Cy3	chemical	Double-cysteine variant of U2AF651,2 was modified with equimolar amount of Cy3 and Cy5.	RESULTS
83	86	Cy5	chemical	Double-cysteine variant of U2AF651,2 was modified with equimolar amount of Cy3 and Cy5.	RESULTS
5	11	traces	evidence	Only traces that showed single photobleaching events for both donor and acceptor dyes and anti-correlated changes in acceptor and donor fluorescence were included in smFRET data analysis.	RESULTS
166	172	smFRET	experimental_method	Only traces that showed single photobleaching events for both donor and acceptor dyes and anti-correlated changes in acceptor and donor fluorescence were included in smFRET data analysis.	RESULTS
63	69	U2AF65	protein	We first characterized the conformational dynamics spectrum of U2AF65 in the absence of RNA (Fig. 6c,d; Supplementary Fig. 7a,b).	RESULTS
77	87	absence of	protein_state	We first characterized the conformational dynamics spectrum of U2AF65 in the absence of RNA (Fig. 6c,d; Supplementary Fig. 7a,b).	RESULTS
88	91	RNA	chemical	We first characterized the conformational dynamics spectrum of U2AF65 in the absence of RNA (Fig. 6c,d; Supplementary Fig. 7a,b).	RESULTS
20	34	U2AF651,2LFRET	mutant	The double-labelled U2AF651,2LFRET(Cy3/Cy5) protein was tethered to a slide via biotin-NTA/Ni+2 resin.	RESULTS
35	38	Cy3	chemical	The double-labelled U2AF651,2LFRET(Cy3/Cy5) protein was tethered to a slide via biotin-NTA/Ni+2 resin.	RESULTS
39	42	Cy5	chemical	The double-labelled U2AF651,2LFRET(Cy3/Cy5) protein was tethered to a slide via biotin-NTA/Ni+2 resin.	RESULTS
56	64	tethered	protein_state	The double-labelled U2AF651,2LFRET(Cy3/Cy5) protein was tethered to a slide via biotin-NTA/Ni+2 resin.	RESULTS
80	101	biotin-NTA/Ni+2 resin	chemical	The double-labelled U2AF651,2LFRET(Cy3/Cy5) protein was tethered to a slide via biotin-NTA/Ni+2 resin.	RESULTS
56	66	absence of	protein_state	Virtually no fluorescent molecules were detected in the absence of biotin-NTA/Ni+2, which demonstrates the absence of detectable non-specific binding of U2AF651,2LFRET to the slide.	RESULTS
67	82	biotin-NTA/Ni+2	chemical	Virtually no fluorescent molecules were detected in the absence of biotin-NTA/Ni+2, which demonstrates the absence of detectable non-specific binding of U2AF651,2LFRET to the slide.	RESULTS
107	117	absence of	protein_state	Virtually no fluorescent molecules were detected in the absence of biotin-NTA/Ni+2, which demonstrates the absence of detectable non-specific binding of U2AF651,2LFRET to the slide.	RESULTS
153	167	U2AF651,2LFRET	mutant	Virtually no fluorescent molecules were detected in the absence of biotin-NTA/Ni+2, which demonstrates the absence of detectable non-specific binding of U2AF651,2LFRET to the slide.	RESULTS
4	31	FRET distribution histogram	evidence	The FRET distribution histogram built from more than a thousand traces of U2AF651,2LFRET(Cy3/Cy5) in the absence of ligand showed an extremely broad distribution centred at a FRET efficiency of ∼0.4 (Fig. 6d).	RESULTS
64	70	traces	evidence	The FRET distribution histogram built from more than a thousand traces of U2AF651,2LFRET(Cy3/Cy5) in the absence of ligand showed an extremely broad distribution centred at a FRET efficiency of ∼0.4 (Fig. 6d).	RESULTS
74	88	U2AF651,2LFRET	mutant	The FRET distribution histogram built from more than a thousand traces of U2AF651,2LFRET(Cy3/Cy5) in the absence of ligand showed an extremely broad distribution centred at a FRET efficiency of ∼0.4 (Fig. 6d).	RESULTS
89	92	Cy3	chemical	The FRET distribution histogram built from more than a thousand traces of U2AF651,2LFRET(Cy3/Cy5) in the absence of ligand showed an extremely broad distribution centred at a FRET efficiency of ∼0.4 (Fig. 6d).	RESULTS
93	96	Cy5	chemical	The FRET distribution histogram built from more than a thousand traces of U2AF651,2LFRET(Cy3/Cy5) in the absence of ligand showed an extremely broad distribution centred at a FRET efficiency of ∼0.4 (Fig. 6d).	RESULTS
105	115	absence of	protein_state	The FRET distribution histogram built from more than a thousand traces of U2AF651,2LFRET(Cy3/Cy5) in the absence of ligand showed an extremely broad distribution centred at a FRET efficiency of ∼0.4 (Fig. 6d).	RESULTS
116	122	ligand	chemical	The FRET distribution histogram built from more than a thousand traces of U2AF651,2LFRET(Cy3/Cy5) in the absence of ligand showed an extremely broad distribution centred at a FRET efficiency of ∼0.4 (Fig. 6d).	RESULTS
175	190	FRET efficiency	evidence	The FRET distribution histogram built from more than a thousand traces of U2AF651,2LFRET(Cy3/Cy5) in the absence of ligand showed an extremely broad distribution centred at a FRET efficiency of ∼0.4 (Fig. 6d).	RESULTS
25	31	smFRET	experimental_method	Approximately 40% of the smFRET traces showed apparent transitions between multiple FRET values (for example, Fig. 6c).	RESULTS
32	38	traces	evidence	Approximately 40% of the smFRET traces showed apparent transitions between multiple FRET values (for example, Fig. 6c).	RESULTS
84	95	FRET values	evidence	Approximately 40% of the smFRET traces showed apparent transitions between multiple FRET values (for example, Fig. 6c).	RESULTS
31	58	FRET-distribution histogram	evidence	Despite the large width of the FRET-distribution histogram, the majority (80%) of traces that showed fluctuations sampled only two distinct FRET states (for example, Supplementary Fig. 7a).	RESULTS
82	88	traces	evidence	Despite the large width of the FRET-distribution histogram, the majority (80%) of traces that showed fluctuations sampled only two distinct FRET states (for example, Supplementary Fig. 7a).	RESULTS
140	151	FRET states	evidence	Despite the large width of the FRET-distribution histogram, the majority (80%) of traces that showed fluctuations sampled only two distinct FRET states (for example, Supplementary Fig. 7a).	RESULTS
89	100	FRET values	evidence	Approximately 70% of observed fluctuations were interchanges between the ∼0.65 and ∼0.45 FRET values (Supplementary Fig. 7b).	RESULTS
50	64	U2AF651,2LFRET	mutant	We cannot exclude a possibility that tethering of U2AF651,2LFRET(Cy3/Cy5) to the microscope slide introduces structural heterogeneity into the protein and, thus, contributes to the breadth of the FRET distribution histogram.	RESULTS
65	68	Cy3	chemical	We cannot exclude a possibility that tethering of U2AF651,2LFRET(Cy3/Cy5) to the microscope slide introduces structural heterogeneity into the protein and, thus, contributes to the breadth of the FRET distribution histogram.	RESULTS
69	72	Cy5	chemical	We cannot exclude a possibility that tethering of U2AF651,2LFRET(Cy3/Cy5) to the microscope slide introduces structural heterogeneity into the protein and, thus, contributes to the breadth of the FRET distribution histogram.	RESULTS
196	223	FRET distribution histogram	evidence	We cannot exclude a possibility that tethering of U2AF651,2LFRET(Cy3/Cy5) to the microscope slide introduces structural heterogeneity into the protein and, thus, contributes to the breadth of the FRET distribution histogram.	RESULTS
68	79	FRET values	evidence	However, the presence of repetitive fluctuations between particular FRET values supports the hypothesis that RNA-free U2AF65 samples several distinct conformations.	RESULTS
109	117	RNA-free	protein_state	However, the presence of repetitive fluctuations between particular FRET values supports the hypothesis that RNA-free U2AF65 samples several distinct conformations.	RESULTS
118	124	U2AF65	protein	However, the presence of repetitive fluctuations between particular FRET values supports the hypothesis that RNA-free U2AF65 samples several distinct conformations.	RESULTS
54	62	extended	protein_state	This result is consistent with the broad ensembles of extended solution conformations that best fit the SAXS data collected for U2AF651,2 as well as for a longer construct (residues 136–347).	RESULTS
104	108	SAXS	experimental_method	This result is consistent with the broad ensembles of extended solution conformations that best fit the SAXS data collected for U2AF651,2 as well as for a longer construct (residues 136–347).	RESULTS
128	137	U2AF651,2	mutant	This result is consistent with the broad ensembles of extended solution conformations that best fit the SAXS data collected for U2AF651,2 as well as for a longer construct (residues 136–347).	RESULTS
182	189	136–347	residue_range	This result is consistent with the broad ensembles of extended solution conformations that best fit the SAXS data collected for U2AF651,2 as well as for a longer construct (residues 136–347).	RESULTS
43	49	U2AF65	protein	We conclude that weak contacts between the U2AF65 RRM1 and RRM2 permit dissociation of these RRMs in the absence of RNA.	RESULTS
50	54	RRM1	structure_element	We conclude that weak contacts between the U2AF65 RRM1 and RRM2 permit dissociation of these RRMs in the absence of RNA.	RESULTS
59	63	RRM2	structure_element	We conclude that weak contacts between the U2AF65 RRM1 and RRM2 permit dissociation of these RRMs in the absence of RNA.	RESULTS
93	97	RRMs	structure_element	We conclude that weak contacts between the U2AF65 RRM1 and RRM2 permit dissociation of these RRMs in the absence of RNA.	RESULTS
105	115	absence of	protein_state	We conclude that weak contacts between the U2AF65 RRM1 and RRM2 permit dissociation of these RRMs in the absence of RNA.	RESULTS
116	119	RNA	chemical	We conclude that weak contacts between the U2AF65 RRM1 and RRM2 permit dissociation of these RRMs in the absence of RNA.	RESULTS
0	6	U2AF65	protein	U2AF65 conformational selection and induced fit by bound RNA	RESULTS
51	56	bound	protein_state	U2AF65 conformational selection and induced fit by bound RNA	RESULTS
57	60	RNA	chemical	U2AF65 conformational selection and induced fit by bound RNA	RESULTS
13	19	smFRET	experimental_method	We next used smFRET to probe the conformational selection of distinct inter-RRM arrangements following association of U2AF65 with the AdML Py-tract prototype.	RESULTS
70	79	inter-RRM	structure_element	We next used smFRET to probe the conformational selection of distinct inter-RRM arrangements following association of U2AF65 with the AdML Py-tract prototype.	RESULTS
118	124	U2AF65	protein	We next used smFRET to probe the conformational selection of distinct inter-RRM arrangements following association of U2AF65 with the AdML Py-tract prototype.	RESULTS
134	138	AdML	gene	We next used smFRET to probe the conformational selection of distinct inter-RRM arrangements following association of U2AF65 with the AdML Py-tract prototype.	RESULTS
139	147	Py-tract	chemical	We next used smFRET to probe the conformational selection of distinct inter-RRM arrangements following association of U2AF65 with the AdML Py-tract prototype.	RESULTS
16	20	AdML	gene	Addition of the AdML RNA to tethered U2AF651,2LFRET(Cy3/Cy5) selectively increases a fraction of molecules showing an ∼0.45 apparent FRET efficiency, suggesting that RNA binding stabilizes a single conformation, which corresponds to the 0.45 FRET state (Fig. 6e,f).	RESULTS
21	24	RNA	chemical	Addition of the AdML RNA to tethered U2AF651,2LFRET(Cy3/Cy5) selectively increases a fraction of molecules showing an ∼0.45 apparent FRET efficiency, suggesting that RNA binding stabilizes a single conformation, which corresponds to the 0.45 FRET state (Fig. 6e,f).	RESULTS
28	36	tethered	protein_state	Addition of the AdML RNA to tethered U2AF651,2LFRET(Cy3/Cy5) selectively increases a fraction of molecules showing an ∼0.45 apparent FRET efficiency, suggesting that RNA binding stabilizes a single conformation, which corresponds to the 0.45 FRET state (Fig. 6e,f).	RESULTS
37	51	U2AF651,2LFRET	mutant	Addition of the AdML RNA to tethered U2AF651,2LFRET(Cy3/Cy5) selectively increases a fraction of molecules showing an ∼0.45 apparent FRET efficiency, suggesting that RNA binding stabilizes a single conformation, which corresponds to the 0.45 FRET state (Fig. 6e,f).	RESULTS
52	55	Cy3	chemical	Addition of the AdML RNA to tethered U2AF651,2LFRET(Cy3/Cy5) selectively increases a fraction of molecules showing an ∼0.45 apparent FRET efficiency, suggesting that RNA binding stabilizes a single conformation, which corresponds to the 0.45 FRET state (Fig. 6e,f).	RESULTS
56	59	Cy5	chemical	Addition of the AdML RNA to tethered U2AF651,2LFRET(Cy3/Cy5) selectively increases a fraction of molecules showing an ∼0.45 apparent FRET efficiency, suggesting that RNA binding stabilizes a single conformation, which corresponds to the 0.45 FRET state (Fig. 6e,f).	RESULTS
133	148	FRET efficiency	evidence	Addition of the AdML RNA to tethered U2AF651,2LFRET(Cy3/Cy5) selectively increases a fraction of molecules showing an ∼0.45 apparent FRET efficiency, suggesting that RNA binding stabilizes a single conformation, which corresponds to the 0.45 FRET state (Fig. 6e,f).	RESULTS
242	252	FRET state	evidence	Addition of the AdML RNA to tethered U2AF651,2LFRET(Cy3/Cy5) selectively increases a fraction of molecules showing an ∼0.45 apparent FRET efficiency, suggesting that RNA binding stabilizes a single conformation, which corresponds to the 0.45 FRET state (Fig. 6e,f).	RESULTS
40	48	RNA-free	protein_state	To assess the possible contributions of RNA-free conformations of U2AF65 and/or structural heterogeneity introduced by tethering of U2AF651,2LFRET(Cy3/Cy5) to the slide to the observed distribution of FRET values, we reversed the immobilization scheme.	RESULTS
66	72	U2AF65	protein	To assess the possible contributions of RNA-free conformations of U2AF65 and/or structural heterogeneity introduced by tethering of U2AF651,2LFRET(Cy3/Cy5) to the slide to the observed distribution of FRET values, we reversed the immobilization scheme.	RESULTS
119	128	tethering	experimental_method	To assess the possible contributions of RNA-free conformations of U2AF65 and/or structural heterogeneity introduced by tethering of U2AF651,2LFRET(Cy3/Cy5) to the slide to the observed distribution of FRET values, we reversed the immobilization scheme.	RESULTS
132	146	U2AF651,2LFRET	mutant	To assess the possible contributions of RNA-free conformations of U2AF65 and/or structural heterogeneity introduced by tethering of U2AF651,2LFRET(Cy3/Cy5) to the slide to the observed distribution of FRET values, we reversed the immobilization scheme.	RESULTS
147	150	Cy3	chemical	To assess the possible contributions of RNA-free conformations of U2AF65 and/or structural heterogeneity introduced by tethering of U2AF651,2LFRET(Cy3/Cy5) to the slide to the observed distribution of FRET values, we reversed the immobilization scheme.	RESULTS
151	154	Cy5	chemical	To assess the possible contributions of RNA-free conformations of U2AF65 and/or structural heterogeneity introduced by tethering of U2AF651,2LFRET(Cy3/Cy5) to the slide to the observed distribution of FRET values, we reversed the immobilization scheme.	RESULTS
185	212	distribution of FRET values	evidence	To assess the possible contributions of RNA-free conformations of U2AF65 and/or structural heterogeneity introduced by tethering of U2AF651,2LFRET(Cy3/Cy5) to the slide to the observed distribution of FRET values, we reversed the immobilization scheme.	RESULTS
217	251	reversed the immobilization scheme	experimental_method	To assess the possible contributions of RNA-free conformations of U2AF65 and/or structural heterogeneity introduced by tethering of U2AF651,2LFRET(Cy3/Cy5) to the slide to the observed distribution of FRET values, we reversed the immobilization scheme.	RESULTS
3	11	tethered	protein_state	We tethered the AdML RNA to the slide via a biotinylated oligonucleotide DNA handle and added U2AF651,2LFRET(Cy3/Cy5) in the absence of biotin-NTA resin (Fig. 6g,h; Supplementary Fig. 7c–g).	RESULTS
16	20	AdML	gene	We tethered the AdML RNA to the slide via a biotinylated oligonucleotide DNA handle and added U2AF651,2LFRET(Cy3/Cy5) in the absence of biotin-NTA resin (Fig. 6g,h; Supplementary Fig. 7c–g).	RESULTS
21	24	RNA	chemical	We tethered the AdML RNA to the slide via a biotinylated oligonucleotide DNA handle and added U2AF651,2LFRET(Cy3/Cy5) in the absence of biotin-NTA resin (Fig. 6g,h; Supplementary Fig. 7c–g).	RESULTS
44	76	biotinylated oligonucleotide DNA	chemical	We tethered the AdML RNA to the slide via a biotinylated oligonucleotide DNA handle and added U2AF651,2LFRET(Cy3/Cy5) in the absence of biotin-NTA resin (Fig. 6g,h; Supplementary Fig. 7c–g).	RESULTS
88	93	added	experimental_method	We tethered the AdML RNA to the slide via a biotinylated oligonucleotide DNA handle and added U2AF651,2LFRET(Cy3/Cy5) in the absence of biotin-NTA resin (Fig. 6g,h; Supplementary Fig. 7c–g).	RESULTS
94	108	U2AF651,2LFRET	mutant	We tethered the AdML RNA to the slide via a biotinylated oligonucleotide DNA handle and added U2AF651,2LFRET(Cy3/Cy5) in the absence of biotin-NTA resin (Fig. 6g,h; Supplementary Fig. 7c–g).	RESULTS
109	112	Cy3	chemical	We tethered the AdML RNA to the slide via a biotinylated oligonucleotide DNA handle and added U2AF651,2LFRET(Cy3/Cy5) in the absence of biotin-NTA resin (Fig. 6g,h; Supplementary Fig. 7c–g).	RESULTS
113	116	Cy5	chemical	We tethered the AdML RNA to the slide via a biotinylated oligonucleotide DNA handle and added U2AF651,2LFRET(Cy3/Cy5) in the absence of biotin-NTA resin (Fig. 6g,h; Supplementary Fig. 7c–g).	RESULTS
125	135	absence of	protein_state	We tethered the AdML RNA to the slide via a biotinylated oligonucleotide DNA handle and added U2AF651,2LFRET(Cy3/Cy5) in the absence of biotin-NTA resin (Fig. 6g,h; Supplementary Fig. 7c–g).	RESULTS
136	152	biotin-NTA resin	chemical	We tethered the AdML RNA to the slide via a biotinylated oligonucleotide DNA handle and added U2AF651,2LFRET(Cy3/Cy5) in the absence of biotin-NTA resin (Fig. 6g,h; Supplementary Fig. 7c–g).	RESULTS
7	17	FRET value	evidence	A 0.45 FRET value was again predominant, indicating a similar RNA-bound conformation and structural dynamics for the untethered and tethered U2AF651,2LFRET(Cy3/Cy5).	RESULTS
62	71	RNA-bound	protein_state	A 0.45 FRET value was again predominant, indicating a similar RNA-bound conformation and structural dynamics for the untethered and tethered U2AF651,2LFRET(Cy3/Cy5).	RESULTS
117	127	untethered	protein_state	A 0.45 FRET value was again predominant, indicating a similar RNA-bound conformation and structural dynamics for the untethered and tethered U2AF651,2LFRET(Cy3/Cy5).	RESULTS
132	140	tethered	protein_state	A 0.45 FRET value was again predominant, indicating a similar RNA-bound conformation and structural dynamics for the untethered and tethered U2AF651,2LFRET(Cy3/Cy5).	RESULTS
141	155	U2AF651,2LFRET	mutant	A 0.45 FRET value was again predominant, indicating a similar RNA-bound conformation and structural dynamics for the untethered and tethered U2AF651,2LFRET(Cy3/Cy5).	RESULTS
156	159	Cy3	chemical	A 0.45 FRET value was again predominant, indicating a similar RNA-bound conformation and structural dynamics for the untethered and tethered U2AF651,2LFRET(Cy3/Cy5).	RESULTS
160	163	Cy5	chemical	A 0.45 FRET value was again predominant, indicating a similar RNA-bound conformation and structural dynamics for the untethered and tethered U2AF651,2LFRET(Cy3/Cy5).	RESULTS
26	36	U2AF651,2L	mutant	We examined the effect on U2AF651,2L conformations of purine interruptions that often occur in relatively degenerate human Py tracts.	RESULTS
54	74	purine interruptions	experimental_method	We examined the effect on U2AF651,2L conformations of purine interruptions that often occur in relatively degenerate human Py tracts.	RESULTS
117	122	human	species	We examined the effect on U2AF651,2L conformations of purine interruptions that often occur in relatively degenerate human Py tracts.	RESULTS
123	132	Py tracts	chemical	We examined the effect on U2AF651,2L conformations of purine interruptions that often occur in relatively degenerate human Py tracts.	RESULTS
3	13	introduced	experimental_method	We introduced an rArA purine dinucleotide within a variant of the AdML Py tract (detailed in Methods).	RESULTS
17	21	rArA	chemical	We introduced an rArA purine dinucleotide within a variant of the AdML Py tract (detailed in Methods).	RESULTS
22	41	purine dinucleotide	chemical	We introduced an rArA purine dinucleotide within a variant of the AdML Py tract (detailed in Methods).	RESULTS
66	70	AdML	gene	We introduced an rArA purine dinucleotide within a variant of the AdML Py tract (detailed in Methods).	RESULTS
71	79	Py tract	chemical	We introduced an rArA purine dinucleotide within a variant of the AdML Py tract (detailed in Methods).	RESULTS
0	9	Insertion	experimental_method	Insertion of adenine nucleotides decreased binding affinity of U2AF65 to RNA by approximately five-fold.	RESULTS
13	32	adenine nucleotides	chemical	Insertion of adenine nucleotides decreased binding affinity of U2AF65 to RNA by approximately five-fold.	RESULTS
43	59	binding affinity	evidence	Insertion of adenine nucleotides decreased binding affinity of U2AF65 to RNA by approximately five-fold.	RESULTS
63	69	U2AF65	protein	Insertion of adenine nucleotides decreased binding affinity of U2AF65 to RNA by approximately five-fold.	RESULTS
73	76	RNA	chemical	Insertion of adenine nucleotides decreased binding affinity of U2AF65 to RNA by approximately five-fold.	RESULTS
62	66	rArA	chemical	Nevertheless, in the presence of saturating concentrations of rArA-interrupted RNA slide-tethered U2AF651,2LFRET(Cy3/Cy5) showed a prevalent ∼0.45 apparent FRET value (Fig. 6i,j), which was also predominant in the presence of continuous Py tract.	RESULTS
79	82	RNA	chemical	Nevertheless, in the presence of saturating concentrations of rArA-interrupted RNA slide-tethered U2AF651,2LFRET(Cy3/Cy5) showed a prevalent ∼0.45 apparent FRET value (Fig. 6i,j), which was also predominant in the presence of continuous Py tract.	RESULTS
83	97	slide-tethered	protein_state	Nevertheless, in the presence of saturating concentrations of rArA-interrupted RNA slide-tethered U2AF651,2LFRET(Cy3/Cy5) showed a prevalent ∼0.45 apparent FRET value (Fig. 6i,j), which was also predominant in the presence of continuous Py tract.	RESULTS
98	112	U2AF651,2LFRET	mutant	Nevertheless, in the presence of saturating concentrations of rArA-interrupted RNA slide-tethered U2AF651,2LFRET(Cy3/Cy5) showed a prevalent ∼0.45 apparent FRET value (Fig. 6i,j), which was also predominant in the presence of continuous Py tract.	RESULTS
113	116	Cy3	chemical	Nevertheless, in the presence of saturating concentrations of rArA-interrupted RNA slide-tethered U2AF651,2LFRET(Cy3/Cy5) showed a prevalent ∼0.45 apparent FRET value (Fig. 6i,j), which was also predominant in the presence of continuous Py tract.	RESULTS
117	120	Cy5	chemical	Nevertheless, in the presence of saturating concentrations of rArA-interrupted RNA slide-tethered U2AF651,2LFRET(Cy3/Cy5) showed a prevalent ∼0.45 apparent FRET value (Fig. 6i,j), which was also predominant in the presence of continuous Py tract.	RESULTS
156	166	FRET value	evidence	Nevertheless, in the presence of saturating concentrations of rArA-interrupted RNA slide-tethered U2AF651,2LFRET(Cy3/Cy5) showed a prevalent ∼0.45 apparent FRET value (Fig. 6i,j), which was also predominant in the presence of continuous Py tract.	RESULTS
237	245	Py tract	chemical	Nevertheless, in the presence of saturating concentrations of rArA-interrupted RNA slide-tethered U2AF651,2LFRET(Cy3/Cy5) showed a prevalent ∼0.45 apparent FRET value (Fig. 6i,j), which was also predominant in the presence of continuous Py tract.	RESULTS
11	15	RRM1	structure_element	Therefore, RRM1-to-RRM2 distance remains similar regardless of whether U2AF65 is bound to interrupted or continuous Py tract.	RESULTS
19	23	RRM2	structure_element	Therefore, RRM1-to-RRM2 distance remains similar regardless of whether U2AF65 is bound to interrupted or continuous Py tract.	RESULTS
71	77	U2AF65	protein	Therefore, RRM1-to-RRM2 distance remains similar regardless of whether U2AF65 is bound to interrupted or continuous Py tract.	RESULTS
81	89	bound to	protein_state	Therefore, RRM1-to-RRM2 distance remains similar regardless of whether U2AF65 is bound to interrupted or continuous Py tract.	RESULTS
116	124	Py tract	chemical	Therefore, RRM1-to-RRM2 distance remains similar regardless of whether U2AF65 is bound to interrupted or continuous Py tract.	RESULTS
4	31	inter-fluorophore distances	evidence	The inter-fluorophore distances derived from the observed 0.45 FRET state agree with the distances between the α-carbon atoms of the respective residues in the crystal structures of U2AF651,2L bound to Py-tract oligonucleotides.	RESULTS
63	73	FRET state	evidence	The inter-fluorophore distances derived from the observed 0.45 FRET state agree with the distances between the α-carbon atoms of the respective residues in the crystal structures of U2AF651,2L bound to Py-tract oligonucleotides.	RESULTS
160	178	crystal structures	evidence	The inter-fluorophore distances derived from the observed 0.45 FRET state agree with the distances between the α-carbon atoms of the respective residues in the crystal structures of U2AF651,2L bound to Py-tract oligonucleotides.	RESULTS
182	192	U2AF651,2L	mutant	The inter-fluorophore distances derived from the observed 0.45 FRET state agree with the distances between the α-carbon atoms of the respective residues in the crystal structures of U2AF651,2L bound to Py-tract oligonucleotides.	RESULTS
193	201	bound to	protein_state	The inter-fluorophore distances derived from the observed 0.45 FRET state agree with the distances between the α-carbon atoms of the respective residues in the crystal structures of U2AF651,2L bound to Py-tract oligonucleotides.	RESULTS
202	227	Py-tract oligonucleotides	chemical	The inter-fluorophore distances derived from the observed 0.45 FRET state agree with the distances between the α-carbon atoms of the respective residues in the crystal structures of U2AF651,2L bound to Py-tract oligonucleotides.	RESULTS
49	60	FRET values	evidence	It should be noted that inferring distances from FRET values is prone to significant error because of uncertainties in the determination of fluorophore orientation factor κ2 and Förster radius R0, the parameters used in distance calculations.	RESULTS
35	45	FRET state	evidence	Nevertheless, the predominant 0.45 FRET state in the presence of RNA agrees with the Py-tract-bound crystal structure of U2AF651,2L.	RESULTS
65	68	RNA	chemical	Nevertheless, the predominant 0.45 FRET state in the presence of RNA agrees with the Py-tract-bound crystal structure of U2AF651,2L.	RESULTS
85	99	Py-tract-bound	protein_state	Nevertheless, the predominant 0.45 FRET state in the presence of RNA agrees with the Py-tract-bound crystal structure of U2AF651,2L.	RESULTS
100	117	crystal structure	evidence	Nevertheless, the predominant 0.45 FRET state in the presence of RNA agrees with the Py-tract-bound crystal structure of U2AF651,2L.	RESULTS
121	131	U2AF651,2L	mutant	Nevertheless, the predominant 0.45 FRET state in the presence of RNA agrees with the Py-tract-bound crystal structure of U2AF651,2L.	RESULTS
29	35	traces	evidence	Importantly, the majority of traces (∼70%) of U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA lacked FRET fluctuations and predominately exhibited a ∼0.45 FRET value (for example, Fig. 6g).	RESULTS
46	60	U2AF651,2LFRET	mutant	Importantly, the majority of traces (∼70%) of U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA lacked FRET fluctuations and predominately exhibited a ∼0.45 FRET value (for example, Fig. 6g).	RESULTS
61	64	Cy3	chemical	Importantly, the majority of traces (∼70%) of U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA lacked FRET fluctuations and predominately exhibited a ∼0.45 FRET value (for example, Fig. 6g).	RESULTS
65	68	Cy5	chemical	Importantly, the majority of traces (∼70%) of U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA lacked FRET fluctuations and predominately exhibited a ∼0.45 FRET value (for example, Fig. 6g).	RESULTS
70	78	bound to	protein_state	Importantly, the majority of traces (∼70%) of U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA lacked FRET fluctuations and predominately exhibited a ∼0.45 FRET value (for example, Fig. 6g).	RESULTS
98	101	RNA	chemical	Importantly, the majority of traces (∼70%) of U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA lacked FRET fluctuations and predominately exhibited a ∼0.45 FRET value (for example, Fig. 6g).	RESULTS
163	173	FRET value	evidence	Importantly, the majority of traces (∼70%) of U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA lacked FRET fluctuations and predominately exhibited a ∼0.45 FRET value (for example, Fig. 6g).	RESULTS
22	28	traces	evidence	The remaining ∼30% of traces for U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA showed fluctuations between distinct FRET values.	RESULTS
33	47	U2AF651,2LFRET	mutant	The remaining ∼30% of traces for U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA showed fluctuations between distinct FRET values.	RESULTS
48	51	Cy3	chemical	The remaining ∼30% of traces for U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA showed fluctuations between distinct FRET values.	RESULTS
52	55	Cy5	chemical	The remaining ∼30% of traces for U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA showed fluctuations between distinct FRET values.	RESULTS
57	65	bound to	protein_state	The remaining ∼30% of traces for U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA showed fluctuations between distinct FRET values.	RESULTS
85	88	RNA	chemical	The remaining ∼30% of traces for U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA showed fluctuations between distinct FRET values.	RESULTS
126	137	FRET values	evidence	The remaining ∼30% of traces for U2AF651,2LFRET(Cy3/Cy5) bound to the slide-tethered RNA showed fluctuations between distinct FRET values.	RESULTS
16	22	traces	evidence	The majority of traces that show fluctuations began at high (0.65–0.8) FRET value and transitioned to a ∼0.45 FRET value (Supplementary Fig. 7c–g).	RESULTS
71	81	FRET value	evidence	The majority of traces that show fluctuations began at high (0.65–0.8) FRET value and transitioned to a ∼0.45 FRET value (Supplementary Fig. 7c–g).	RESULTS
110	120	FRET value	evidence	The majority of traces that show fluctuations began at high (0.65–0.8) FRET value and transitioned to a ∼0.45 FRET value (Supplementary Fig. 7c–g).	RESULTS
0	32	Hidden Markov modelling analysis	experimental_method	Hidden Markov modelling analysis of smFRET traces suggests that RNA-bound U2AF651,2L can sample at least two other conformations corresponding to ∼0.7–0.8 and ∼0.3 FRET values in addition to the predominant conformation corresponding to the 0.45 FRET state.	RESULTS
36	42	smFRET	experimental_method	Hidden Markov modelling analysis of smFRET traces suggests that RNA-bound U2AF651,2L can sample at least two other conformations corresponding to ∼0.7–0.8 and ∼0.3 FRET values in addition to the predominant conformation corresponding to the 0.45 FRET state.	RESULTS
43	49	traces	evidence	Hidden Markov modelling analysis of smFRET traces suggests that RNA-bound U2AF651,2L can sample at least two other conformations corresponding to ∼0.7–0.8 and ∼0.3 FRET values in addition to the predominant conformation corresponding to the 0.45 FRET state.	RESULTS
64	73	RNA-bound	protein_state	Hidden Markov modelling analysis of smFRET traces suggests that RNA-bound U2AF651,2L can sample at least two other conformations corresponding to ∼0.7–0.8 and ∼0.3 FRET values in addition to the predominant conformation corresponding to the 0.45 FRET state.	RESULTS
74	84	U2AF651,2L	mutant	Hidden Markov modelling analysis of smFRET traces suggests that RNA-bound U2AF651,2L can sample at least two other conformations corresponding to ∼0.7–0.8 and ∼0.3 FRET values in addition to the predominant conformation corresponding to the 0.45 FRET state.	RESULTS
164	175	FRET values	evidence	Hidden Markov modelling analysis of smFRET traces suggests that RNA-bound U2AF651,2L can sample at least two other conformations corresponding to ∼0.7–0.8 and ∼0.3 FRET values in addition to the predominant conformation corresponding to the 0.45 FRET state.	RESULTS
246	256	FRET state	evidence	Hidden Markov modelling analysis of smFRET traces suggests that RNA-bound U2AF651,2L can sample at least two other conformations corresponding to ∼0.7–0.8 and ∼0.3 FRET values in addition to the predominant conformation corresponding to the 0.45 FRET state.	RESULTS
63	73	U2AF651,2L	mutant	Although a compact conformation (or multiple conformations) of U2AF651,2L corresponding to ∼0.7–0.8 FRET values can bind RNA, on RNA binding, these compact conformations of U2AF651,2L transition into a more stable structural state that corresponds to ∼0.45 FRET value and is likely similar to the side-by-side inter-RRM-arrangement of the U2AF651,2L crystal structures.	RESULTS
100	111	FRET values	evidence	Although a compact conformation (or multiple conformations) of U2AF651,2L corresponding to ∼0.7–0.8 FRET values can bind RNA, on RNA binding, these compact conformations of U2AF651,2L transition into a more stable structural state that corresponds to ∼0.45 FRET value and is likely similar to the side-by-side inter-RRM-arrangement of the U2AF651,2L crystal structures.	RESULTS
121	124	RNA	chemical	Although a compact conformation (or multiple conformations) of U2AF651,2L corresponding to ∼0.7–0.8 FRET values can bind RNA, on RNA binding, these compact conformations of U2AF651,2L transition into a more stable structural state that corresponds to ∼0.45 FRET value and is likely similar to the side-by-side inter-RRM-arrangement of the U2AF651,2L crystal structures.	RESULTS
129	132	RNA	chemical	Although a compact conformation (or multiple conformations) of U2AF651,2L corresponding to ∼0.7–0.8 FRET values can bind RNA, on RNA binding, these compact conformations of U2AF651,2L transition into a more stable structural state that corresponds to ∼0.45 FRET value and is likely similar to the side-by-side inter-RRM-arrangement of the U2AF651,2L crystal structures.	RESULTS
148	155	compact	protein_state	Although a compact conformation (or multiple conformations) of U2AF651,2L corresponding to ∼0.7–0.8 FRET values can bind RNA, on RNA binding, these compact conformations of U2AF651,2L transition into a more stable structural state that corresponds to ∼0.45 FRET value and is likely similar to the side-by-side inter-RRM-arrangement of the U2AF651,2L crystal structures.	RESULTS
173	183	U2AF651,2L	mutant	Although a compact conformation (or multiple conformations) of U2AF651,2L corresponding to ∼0.7–0.8 FRET values can bind RNA, on RNA binding, these compact conformations of U2AF651,2L transition into a more stable structural state that corresponds to ∼0.45 FRET value and is likely similar to the side-by-side inter-RRM-arrangement of the U2AF651,2L crystal structures.	RESULTS
257	267	FRET value	evidence	Although a compact conformation (or multiple conformations) of U2AF651,2L corresponding to ∼0.7–0.8 FRET values can bind RNA, on RNA binding, these compact conformations of U2AF651,2L transition into a more stable structural state that corresponds to ∼0.45 FRET value and is likely similar to the side-by-side inter-RRM-arrangement of the U2AF651,2L crystal structures.	RESULTS
297	309	side-by-side	protein_state	Although a compact conformation (or multiple conformations) of U2AF651,2L corresponding to ∼0.7–0.8 FRET values can bind RNA, on RNA binding, these compact conformations of U2AF651,2L transition into a more stable structural state that corresponds to ∼0.45 FRET value and is likely similar to the side-by-side inter-RRM-arrangement of the U2AF651,2L crystal structures.	RESULTS
310	319	inter-RRM	structure_element	Although a compact conformation (or multiple conformations) of U2AF651,2L corresponding to ∼0.7–0.8 FRET values can bind RNA, on RNA binding, these compact conformations of U2AF651,2L transition into a more stable structural state that corresponds to ∼0.45 FRET value and is likely similar to the side-by-side inter-RRM-arrangement of the U2AF651,2L crystal structures.	RESULTS
339	349	U2AF651,2L	mutant	Although a compact conformation (or multiple conformations) of U2AF651,2L corresponding to ∼0.7–0.8 FRET values can bind RNA, on RNA binding, these compact conformations of U2AF651,2L transition into a more stable structural state that corresponds to ∼0.45 FRET value and is likely similar to the side-by-side inter-RRM-arrangement of the U2AF651,2L crystal structures.	RESULTS
350	368	crystal structures	evidence	Although a compact conformation (or multiple conformations) of U2AF651,2L corresponding to ∼0.7–0.8 FRET values can bind RNA, on RNA binding, these compact conformations of U2AF651,2L transition into a more stable structural state that corresponds to ∼0.45 FRET value and is likely similar to the side-by-side inter-RRM-arrangement of the U2AF651,2L crystal structures.	RESULTS
51	57	U2AF65	protein	Thus, the sequence of structural rearrangements of U2AF65 observed in smFRET traces (Supplementary Fig. 7c–g) suggests that a ‘conformational selection' mechanism of Py-tract recognition (that is, RNA ligand stabilization of a pre-configured U2AF65 conformation) is complemented by ‘induced fit' (that is, RNA-induced rearrangement of the U2AF65 RRMs to achieve the final ‘side-by-side' conformation), as discussed below.	RESULTS
70	76	smFRET	experimental_method	Thus, the sequence of structural rearrangements of U2AF65 observed in smFRET traces (Supplementary Fig. 7c–g) suggests that a ‘conformational selection' mechanism of Py-tract recognition (that is, RNA ligand stabilization of a pre-configured U2AF65 conformation) is complemented by ‘induced fit' (that is, RNA-induced rearrangement of the U2AF65 RRMs to achieve the final ‘side-by-side' conformation), as discussed below.	RESULTS
77	83	traces	evidence	Thus, the sequence of structural rearrangements of U2AF65 observed in smFRET traces (Supplementary Fig. 7c–g) suggests that a ‘conformational selection' mechanism of Py-tract recognition (that is, RNA ligand stabilization of a pre-configured U2AF65 conformation) is complemented by ‘induced fit' (that is, RNA-induced rearrangement of the U2AF65 RRMs to achieve the final ‘side-by-side' conformation), as discussed below.	RESULTS
166	174	Py-tract	chemical	Thus, the sequence of structural rearrangements of U2AF65 observed in smFRET traces (Supplementary Fig. 7c–g) suggests that a ‘conformational selection' mechanism of Py-tract recognition (that is, RNA ligand stabilization of a pre-configured U2AF65 conformation) is complemented by ‘induced fit' (that is, RNA-induced rearrangement of the U2AF65 RRMs to achieve the final ‘side-by-side' conformation), as discussed below.	RESULTS
227	241	pre-configured	protein_state	Thus, the sequence of structural rearrangements of U2AF65 observed in smFRET traces (Supplementary Fig. 7c–g) suggests that a ‘conformational selection' mechanism of Py-tract recognition (that is, RNA ligand stabilization of a pre-configured U2AF65 conformation) is complemented by ‘induced fit' (that is, RNA-induced rearrangement of the U2AF65 RRMs to achieve the final ‘side-by-side' conformation), as discussed below.	RESULTS
242	248	U2AF65	protein	Thus, the sequence of structural rearrangements of U2AF65 observed in smFRET traces (Supplementary Fig. 7c–g) suggests that a ‘conformational selection' mechanism of Py-tract recognition (that is, RNA ligand stabilization of a pre-configured U2AF65 conformation) is complemented by ‘induced fit' (that is, RNA-induced rearrangement of the U2AF65 RRMs to achieve the final ‘side-by-side' conformation), as discussed below.	RESULTS
339	345	U2AF65	protein	Thus, the sequence of structural rearrangements of U2AF65 observed in smFRET traces (Supplementary Fig. 7c–g) suggests that a ‘conformational selection' mechanism of Py-tract recognition (that is, RNA ligand stabilization of a pre-configured U2AF65 conformation) is complemented by ‘induced fit' (that is, RNA-induced rearrangement of the U2AF65 RRMs to achieve the final ‘side-by-side' conformation), as discussed below.	RESULTS
346	350	RRMs	structure_element	Thus, the sequence of structural rearrangements of U2AF65 observed in smFRET traces (Supplementary Fig. 7c–g) suggests that a ‘conformational selection' mechanism of Py-tract recognition (that is, RNA ligand stabilization of a pre-configured U2AF65 conformation) is complemented by ‘induced fit' (that is, RNA-induced rearrangement of the U2AF65 RRMs to achieve the final ‘side-by-side' conformation), as discussed below.	RESULTS
373	385	side-by-side	protein_state	Thus, the sequence of structural rearrangements of U2AF65 observed in smFRET traces (Supplementary Fig. 7c–g) suggests that a ‘conformational selection' mechanism of Py-tract recognition (that is, RNA ligand stabilization of a pre-configured U2AF65 conformation) is complemented by ‘induced fit' (that is, RNA-induced rearrangement of the U2AF65 RRMs to achieve the final ‘side-by-side' conformation), as discussed below.	RESULTS
4	10	U2AF65	protein	The U2AF65 structures and analyses presented here represent a successful step towards defining a molecular map of the 3′ splice site.	DISCUSS
11	21	structures	evidence	The U2AF65 structures and analyses presented here represent a successful step towards defining a molecular map of the 3′ splice site.	DISCUSS
26	34	analyses	evidence	The U2AF65 structures and analyses presented here represent a successful step towards defining a molecular map of the 3′ splice site.	DISCUSS
118	132	3′ splice site	site	The U2AF65 structures and analyses presented here represent a successful step towards defining a molecular map of the 3′ splice site.	DISCUSS
97	113	inter-RRM linker	structure_element	Several observations indicate that the numerous intramolecular contacts, here revealed among the inter-RRM linker and RRM1, RRM2, and the N-terminal RRM1 extension, synergistically coordinate U2AF65–Py-tract recognition.	DISCUSS
118	122	RRM1	structure_element	Several observations indicate that the numerous intramolecular contacts, here revealed among the inter-RRM linker and RRM1, RRM2, and the N-terminal RRM1 extension, synergistically coordinate U2AF65–Py-tract recognition.	DISCUSS
124	128	RRM2	structure_element	Several observations indicate that the numerous intramolecular contacts, here revealed among the inter-RRM linker and RRM1, RRM2, and the N-terminal RRM1 extension, synergistically coordinate U2AF65–Py-tract recognition.	DISCUSS
149	163	RRM1 extension	structure_element	Several observations indicate that the numerous intramolecular contacts, here revealed among the inter-RRM linker and RRM1, RRM2, and the N-terminal RRM1 extension, synergistically coordinate U2AF65–Py-tract recognition.	DISCUSS
192	198	U2AF65	protein	Several observations indicate that the numerous intramolecular contacts, here revealed among the inter-RRM linker and RRM1, RRM2, and the N-terminal RRM1 extension, synergistically coordinate U2AF65–Py-tract recognition.	DISCUSS
199	207	Py-tract	chemical	Several observations indicate that the numerous intramolecular contacts, here revealed among the inter-RRM linker and RRM1, RRM2, and the N-terminal RRM1 extension, synergistically coordinate U2AF65–Py-tract recognition.	DISCUSS
0	10	Truncation	experimental_method	Truncation of U2AF65 to the core RRM1–RRM2 region reduces its RNA affinity by 100-fold.	DISCUSS
14	20	U2AF65	protein	Truncation of U2AF65 to the core RRM1–RRM2 region reduces its RNA affinity by 100-fold.	DISCUSS
28	32	core	protein_state	Truncation of U2AF65 to the core RRM1–RRM2 region reduces its RNA affinity by 100-fold.	DISCUSS
33	49	RRM1–RRM2 region	structure_element	Truncation of U2AF65 to the core RRM1–RRM2 region reduces its RNA affinity by 100-fold.	DISCUSS
62	74	RNA affinity	evidence	Truncation of U2AF65 to the core RRM1–RRM2 region reduces its RNA affinity by 100-fold.	DISCUSS
10	18	deletion	experimental_method	Likewise, deletion of 20 inter-RRM linker residues significantly reduces U2AF65–RNA binding only when introduced in the context of the longer U2AF651,2L construct comprising the RRM extensions, which in turn position the linker for RNA interactions.	DISCUSS
22	24	20	residue_range	Likewise, deletion of 20 inter-RRM linker residues significantly reduces U2AF65–RNA binding only when introduced in the context of the longer U2AF651,2L construct comprising the RRM extensions, which in turn position the linker for RNA interactions.	DISCUSS
25	50	inter-RRM linker residues	structure_element	Likewise, deletion of 20 inter-RRM linker residues significantly reduces U2AF65–RNA binding only when introduced in the context of the longer U2AF651,2L construct comprising the RRM extensions, which in turn position the linker for RNA interactions.	DISCUSS
73	79	U2AF65	protein	Likewise, deletion of 20 inter-RRM linker residues significantly reduces U2AF65–RNA binding only when introduced in the context of the longer U2AF651,2L construct comprising the RRM extensions, which in turn position the linker for RNA interactions.	DISCUSS
80	83	RNA	chemical	Likewise, deletion of 20 inter-RRM linker residues significantly reduces U2AF65–RNA binding only when introduced in the context of the longer U2AF651,2L construct comprising the RRM extensions, which in turn position the linker for RNA interactions.	DISCUSS
135	141	longer	protein_state	Likewise, deletion of 20 inter-RRM linker residues significantly reduces U2AF65–RNA binding only when introduced in the context of the longer U2AF651,2L construct comprising the RRM extensions, which in turn position the linker for RNA interactions.	DISCUSS
142	152	U2AF651,2L	mutant	Likewise, deletion of 20 inter-RRM linker residues significantly reduces U2AF65–RNA binding only when introduced in the context of the longer U2AF651,2L construct comprising the RRM extensions, which in turn position the linker for RNA interactions.	DISCUSS
178	192	RRM extensions	structure_element	Likewise, deletion of 20 inter-RRM linker residues significantly reduces U2AF65–RNA binding only when introduced in the context of the longer U2AF651,2L construct comprising the RRM extensions, which in turn position the linker for RNA interactions.	DISCUSS
221	227	linker	structure_element	Likewise, deletion of 20 inter-RRM linker residues significantly reduces U2AF65–RNA binding only when introduced in the context of the longer U2AF651,2L construct comprising the RRM extensions, which in turn position the linker for RNA interactions.	DISCUSS
232	235	RNA	chemical	Likewise, deletion of 20 inter-RRM linker residues significantly reduces U2AF65–RNA binding only when introduced in the context of the longer U2AF651,2L construct comprising the RRM extensions, which in turn position the linker for RNA interactions.	DISCUSS
11	26	triple mutation	protein_state	Notably, a triple mutation of three residues (V254P, Q147A and R227A) in the respective inter-RRM linker, N- and C-terminal extensions non-additively reduce RNA binding by 150-fold.	DISCUSS
46	51	V254P	mutant	Notably, a triple mutation of three residues (V254P, Q147A and R227A) in the respective inter-RRM linker, N- and C-terminal extensions non-additively reduce RNA binding by 150-fold.	DISCUSS
53	58	Q147A	mutant	Notably, a triple mutation of three residues (V254P, Q147A and R227A) in the respective inter-RRM linker, N- and C-terminal extensions non-additively reduce RNA binding by 150-fold.	DISCUSS
63	68	R227A	mutant	Notably, a triple mutation of three residues (V254P, Q147A and R227A) in the respective inter-RRM linker, N- and C-terminal extensions non-additively reduce RNA binding by 150-fold.	DISCUSS
88	104	inter-RRM linker	structure_element	Notably, a triple mutation of three residues (V254P, Q147A and R227A) in the respective inter-RRM linker, N- and C-terminal extensions non-additively reduce RNA binding by 150-fold.	DISCUSS
106	134	N- and C-terminal extensions	structure_element	Notably, a triple mutation of three residues (V254P, Q147A and R227A) in the respective inter-RRM linker, N- and C-terminal extensions non-additively reduce RNA binding by 150-fold.	DISCUSS
157	168	RNA binding	evidence	Notably, a triple mutation of three residues (V254P, Q147A and R227A) in the respective inter-RRM linker, N- and C-terminal extensions non-additively reduce RNA binding by 150-fold.	DISCUSS
60	66	U2AF65	protein	Altogether, these data indicate that interactions among the U2AF65 RRM1/RRM2, inter-RRM linker, N-and C-terminal extensions are mutually inter-dependent for cognate Py-tract recognition.	DISCUSS
67	71	RRM1	structure_element	Altogether, these data indicate that interactions among the U2AF65 RRM1/RRM2, inter-RRM linker, N-and C-terminal extensions are mutually inter-dependent for cognate Py-tract recognition.	DISCUSS
72	76	RRM2	structure_element	Altogether, these data indicate that interactions among the U2AF65 RRM1/RRM2, inter-RRM linker, N-and C-terminal extensions are mutually inter-dependent for cognate Py-tract recognition.	DISCUSS
78	94	inter-RRM linker	structure_element	Altogether, these data indicate that interactions among the U2AF65 RRM1/RRM2, inter-RRM linker, N-and C-terminal extensions are mutually inter-dependent for cognate Py-tract recognition.	DISCUSS
96	123	N-and C-terminal extensions	structure_element	Altogether, these data indicate that interactions among the U2AF65 RRM1/RRM2, inter-RRM linker, N-and C-terminal extensions are mutually inter-dependent for cognate Py-tract recognition.	DISCUSS
165	173	Py-tract	chemical	Altogether, these data indicate that interactions among the U2AF65 RRM1/RRM2, inter-RRM linker, N-and C-terminal extensions are mutually inter-dependent for cognate Py-tract recognition.	DISCUSS
37	43	U2AF65	protein	The implications of this finding for U2AF65 conservation and Py-tract recognition are detailed in the Supplementary Discussion.	DISCUSS
61	69	Py-tract	chemical	The implications of this finding for U2AF65 conservation and Py-tract recognition are detailed in the Supplementary Discussion.	DISCUSS
10	44	high-throughput sequencing studies	experimental_method	Recently, high-throughput sequencing studies have shown that somatic mutations in pre-mRNA splicing factors occur in the majority of patients with myelodysplastic syndrome (MDS).	DISCUSS
82	107	pre-mRNA splicing factors	protein_type	Recently, high-throughput sequencing studies have shown that somatic mutations in pre-mRNA splicing factors occur in the majority of patients with myelodysplastic syndrome (MDS).	DISCUSS
41	46	small	protein_state	MDS-relevant mutations are common in the small U2AF subunit (U2AF35, or U2AF1), yet such mutations are rare in the large U2AF65 subunit (also called U2AF2)—possibly due to the selective versus nearly universal requirements of these factors for splicing.	DISCUSS
47	59	U2AF subunit	protein_type	MDS-relevant mutations are common in the small U2AF subunit (U2AF35, or U2AF1), yet such mutations are rare in the large U2AF65 subunit (also called U2AF2)—possibly due to the selective versus nearly universal requirements of these factors for splicing.	DISCUSS
61	67	U2AF35	protein	MDS-relevant mutations are common in the small U2AF subunit (U2AF35, or U2AF1), yet such mutations are rare in the large U2AF65 subunit (also called U2AF2)—possibly due to the selective versus nearly universal requirements of these factors for splicing.	DISCUSS
72	77	U2AF1	protein	MDS-relevant mutations are common in the small U2AF subunit (U2AF35, or U2AF1), yet such mutations are rare in the large U2AF65 subunit (also called U2AF2)—possibly due to the selective versus nearly universal requirements of these factors for splicing.	DISCUSS
115	120	large	protein_state	MDS-relevant mutations are common in the small U2AF subunit (U2AF35, or U2AF1), yet such mutations are rare in the large U2AF65 subunit (also called U2AF2)—possibly due to the selective versus nearly universal requirements of these factors for splicing.	DISCUSS
121	127	U2AF65	protein	MDS-relevant mutations are common in the small U2AF subunit (U2AF35, or U2AF1), yet such mutations are rare in the large U2AF65 subunit (also called U2AF2)—possibly due to the selective versus nearly universal requirements of these factors for splicing.	DISCUSS
149	154	U2AF2	protein	MDS-relevant mutations are common in the small U2AF subunit (U2AF35, or U2AF1), yet such mutations are rare in the large U2AF65 subunit (also called U2AF2)—possibly due to the selective versus nearly universal requirements of these factors for splicing.	DISCUSS
32	38	U2AF65	protein	A confirmed somatic mutation of U2AF65 in patients with MDS, L187V, is located on a solvent-exposed surface of RRM1 that is distinct from the RNA interface (Fig. 7a).	DISCUSS
61	66	L187V	mutant	A confirmed somatic mutation of U2AF65 in patients with MDS, L187V, is located on a solvent-exposed surface of RRM1 that is distinct from the RNA interface (Fig. 7a).	DISCUSS
84	107	solvent-exposed surface	site	A confirmed somatic mutation of U2AF65 in patients with MDS, L187V, is located on a solvent-exposed surface of RRM1 that is distinct from the RNA interface (Fig. 7a).	DISCUSS
111	115	RRM1	structure_element	A confirmed somatic mutation of U2AF65 in patients with MDS, L187V, is located on a solvent-exposed surface of RRM1 that is distinct from the RNA interface (Fig. 7a).	DISCUSS
142	155	RNA interface	site	A confirmed somatic mutation of U2AF65 in patients with MDS, L187V, is located on a solvent-exposed surface of RRM1 that is distinct from the RNA interface (Fig. 7a).	DISCUSS
5	9	L187	residue_name_number	This L187 surface is oriented towards the N terminus of the U2AF651,2L construct, where it is expected to abut the U2AF35-binding site in the context of the full-length U2AF heterodimer.	DISCUSS
60	70	U2AF651,2L	mutant	This L187 surface is oriented towards the N terminus of the U2AF651,2L construct, where it is expected to abut the U2AF35-binding site in the context of the full-length U2AF heterodimer.	DISCUSS
115	134	U2AF35-binding site	site	This L187 surface is oriented towards the N terminus of the U2AF651,2L construct, where it is expected to abut the U2AF35-binding site in the context of the full-length U2AF heterodimer.	DISCUSS
157	168	full-length	protein_state	This L187 surface is oriented towards the N terminus of the U2AF651,2L construct, where it is expected to abut the U2AF35-binding site in the context of the full-length U2AF heterodimer.	DISCUSS
169	173	U2AF	protein	This L187 surface is oriented towards the N terminus of the U2AF651,2L construct, where it is expected to abut the U2AF35-binding site in the context of the full-length U2AF heterodimer.	DISCUSS
174	185	heterodimer	oligomeric_state	This L187 surface is oriented towards the N terminus of the U2AF651,2L construct, where it is expected to abut the U2AF35-binding site in the context of the full-length U2AF heterodimer.	DISCUSS
25	30	M144I	mutant	Likewise, an unconfirmed M144I mutation reported by the same group corresponds to the N-terminal residue of U2AF651,2L, which is separated by only ∼20 residues from the U2AF35-binding site.	DISCUSS
108	118	U2AF651,2L	mutant	Likewise, an unconfirmed M144I mutation reported by the same group corresponds to the N-terminal residue of U2AF651,2L, which is separated by only ∼20 residues from the U2AF35-binding site.	DISCUSS
169	188	U2AF35-binding site	site	Likewise, an unconfirmed M144I mutation reported by the same group corresponds to the N-terminal residue of U2AF651,2L, which is separated by only ∼20 residues from the U2AF35-binding site.	DISCUSS
42	48	U2AF65	protein	As such, we suggest that the MDS-relevant U2AF65 mutations contribute to MDS progression indirectly, by destabilizing a relevant conformation of the conjoined U2AF35 subunit rather than affecting U2AF65 functions in RNA binding or spliceosome recruitment per se.	DISCUSS
159	165	U2AF35	protein	As such, we suggest that the MDS-relevant U2AF65 mutations contribute to MDS progression indirectly, by destabilizing a relevant conformation of the conjoined U2AF35 subunit rather than affecting U2AF65 functions in RNA binding or spliceosome recruitment per se.	DISCUSS
196	202	U2AF65	protein	As such, we suggest that the MDS-relevant U2AF65 mutations contribute to MDS progression indirectly, by destabilizing a relevant conformation of the conjoined U2AF35 subunit rather than affecting U2AF65 functions in RNA binding or spliceosome recruitment per se.	DISCUSS
216	219	RNA	chemical	As such, we suggest that the MDS-relevant U2AF65 mutations contribute to MDS progression indirectly, by destabilizing a relevant conformation of the conjoined U2AF35 subunit rather than affecting U2AF65 functions in RNA binding or spliceosome recruitment per se.	DISCUSS
231	242	spliceosome	complex_assembly	As such, we suggest that the MDS-relevant U2AF65 mutations contribute to MDS progression indirectly, by destabilizing a relevant conformation of the conjoined U2AF35 subunit rather than affecting U2AF65 functions in RNA binding or spliceosome recruitment per se.	DISCUSS
4	10	smFRET	experimental_method	Our smFRET results agree with prior NMR/PRE evidence for multi-domain conformational selection as one mechanistic basis for U2AF65–RNA association (Fig. 7b).	DISCUSS
36	39	NMR	experimental_method	Our smFRET results agree with prior NMR/PRE evidence for multi-domain conformational selection as one mechanistic basis for U2AF65–RNA association (Fig. 7b).	DISCUSS
40	43	PRE	experimental_method	Our smFRET results agree with prior NMR/PRE evidence for multi-domain conformational selection as one mechanistic basis for U2AF65–RNA association (Fig. 7b).	DISCUSS
124	130	U2AF65	protein	Our smFRET results agree with prior NMR/PRE evidence for multi-domain conformational selection as one mechanistic basis for U2AF65–RNA association (Fig. 7b).	DISCUSS
131	134	RNA	chemical	Our smFRET results agree with prior NMR/PRE evidence for multi-domain conformational selection as one mechanistic basis for U2AF65–RNA association (Fig. 7b).	DISCUSS
9	19	FRET value	evidence	An ∼0.45 FRET value is likely to correspond to the U2AF65 conformation visualized in our U2AF651,2L crystal structures, in which the RRM1 and RRM2 bind side-by-side to the Py-tract oligonucleotide.	DISCUSS
51	57	U2AF65	protein	An ∼0.45 FRET value is likely to correspond to the U2AF65 conformation visualized in our U2AF651,2L crystal structures, in which the RRM1 and RRM2 bind side-by-side to the Py-tract oligonucleotide.	DISCUSS
89	99	U2AF651,2L	mutant	An ∼0.45 FRET value is likely to correspond to the U2AF65 conformation visualized in our U2AF651,2L crystal structures, in which the RRM1 and RRM2 bind side-by-side to the Py-tract oligonucleotide.	DISCUSS
100	118	crystal structures	evidence	An ∼0.45 FRET value is likely to correspond to the U2AF65 conformation visualized in our U2AF651,2L crystal structures, in which the RRM1 and RRM2 bind side-by-side to the Py-tract oligonucleotide.	DISCUSS
133	137	RRM1	structure_element	An ∼0.45 FRET value is likely to correspond to the U2AF65 conformation visualized in our U2AF651,2L crystal structures, in which the RRM1 and RRM2 bind side-by-side to the Py-tract oligonucleotide.	DISCUSS
142	146	RRM2	structure_element	An ∼0.45 FRET value is likely to correspond to the U2AF65 conformation visualized in our U2AF651,2L crystal structures, in which the RRM1 and RRM2 bind side-by-side to the Py-tract oligonucleotide.	DISCUSS
152	164	side-by-side	protein_state	An ∼0.45 FRET value is likely to correspond to the U2AF65 conformation visualized in our U2AF651,2L crystal structures, in which the RRM1 and RRM2 bind side-by-side to the Py-tract oligonucleotide.	DISCUSS
172	196	Py-tract oligonucleotide	chemical	An ∼0.45 FRET value is likely to correspond to the U2AF65 conformation visualized in our U2AF651,2L crystal structures, in which the RRM1 and RRM2 bind side-by-side to the Py-tract oligonucleotide.	DISCUSS
32	43	FRET values	evidence	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
51	61	untethered	protein_state	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
62	76	U2AF651,2LFRET	mutant	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
77	80	Cy3	chemical	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
81	84	Cy5	chemical	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
145	151	closed	protein_state	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
154	166	back-to-back	protein_state	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
167	173	U2AF65	protein	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
205	208	NMR	experimental_method	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
209	212	PRE	experimental_method	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
225	233	extended	protein_state	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
234	240	U2AF65	protein	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
284	288	RRM1	structure_element	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
289	293	RRM2	structure_element	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
328	335	protein	protein	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
339	347	bound to	protein_state	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
348	351	RNA	chemical	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
356	362	single	protein_state	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
363	367	RRMs	structure_element	The lesser 0.65–0.8 and 0.2–0.3 FRET values in the untethered U2AF651,2LFRET(Cy3/Cy5) experiment could correspond to respective variants of the ‘closed', back-to-back U2AF65 conformations characterized by NMR/PRE data, or to extended U2AF65 conformations, in which the intramolecular RRM1/RRM2 interactions have dissociated the protein is bound to RNA via single RRMs.	DISCUSS
37	47	FRET value	evidence	An increased prevalence of the ∼0.45 FRET value following U2AF65–RNA binding, coupled with the apparent absence of transitions in many ∼0.45-value single molecule traces (for example, Fig. 6e), suggests a population shift in which RNA binds to (and draws the equilibrium towards) a pre-configured inter-RRM proximity that most often corresponds to the ∼0.45 FRET value.	DISCUSS
58	64	U2AF65	protein	An increased prevalence of the ∼0.45 FRET value following U2AF65–RNA binding, coupled with the apparent absence of transitions in many ∼0.45-value single molecule traces (for example, Fig. 6e), suggests a population shift in which RNA binds to (and draws the equilibrium towards) a pre-configured inter-RRM proximity that most often corresponds to the ∼0.45 FRET value.	DISCUSS
65	68	RNA	chemical	An increased prevalence of the ∼0.45 FRET value following U2AF65–RNA binding, coupled with the apparent absence of transitions in many ∼0.45-value single molecule traces (for example, Fig. 6e), suggests a population shift in which RNA binds to (and draws the equilibrium towards) a pre-configured inter-RRM proximity that most often corresponds to the ∼0.45 FRET value.	DISCUSS
104	114	absence of	protein_state	An increased prevalence of the ∼0.45 FRET value following U2AF65–RNA binding, coupled with the apparent absence of transitions in many ∼0.45-value single molecule traces (for example, Fig. 6e), suggests a population shift in which RNA binds to (and draws the equilibrium towards) a pre-configured inter-RRM proximity that most often corresponds to the ∼0.45 FRET value.	DISCUSS
163	169	traces	evidence	An increased prevalence of the ∼0.45 FRET value following U2AF65–RNA binding, coupled with the apparent absence of transitions in many ∼0.45-value single molecule traces (for example, Fig. 6e), suggests a population shift in which RNA binds to (and draws the equilibrium towards) a pre-configured inter-RRM proximity that most often corresponds to the ∼0.45 FRET value.	DISCUSS
231	234	RNA	chemical	An increased prevalence of the ∼0.45 FRET value following U2AF65–RNA binding, coupled with the apparent absence of transitions in many ∼0.45-value single molecule traces (for example, Fig. 6e), suggests a population shift in which RNA binds to (and draws the equilibrium towards) a pre-configured inter-RRM proximity that most often corresponds to the ∼0.45 FRET value.	DISCUSS
282	296	pre-configured	protein_state	An increased prevalence of the ∼0.45 FRET value following U2AF65–RNA binding, coupled with the apparent absence of transitions in many ∼0.45-value single molecule traces (for example, Fig. 6e), suggests a population shift in which RNA binds to (and draws the equilibrium towards) a pre-configured inter-RRM proximity that most often corresponds to the ∼0.45 FRET value.	DISCUSS
297	306	inter-RRM	structure_element	An increased prevalence of the ∼0.45 FRET value following U2AF65–RNA binding, coupled with the apparent absence of transitions in many ∼0.45-value single molecule traces (for example, Fig. 6e), suggests a population shift in which RNA binds to (and draws the equilibrium towards) a pre-configured inter-RRM proximity that most often corresponds to the ∼0.45 FRET value.	DISCUSS
358	368	FRET value	evidence	An increased prevalence of the ∼0.45 FRET value following U2AF65–RNA binding, coupled with the apparent absence of transitions in many ∼0.45-value single molecule traces (for example, Fig. 6e), suggests a population shift in which RNA binds to (and draws the equilibrium towards) a pre-configured inter-RRM proximity that most often corresponds to the ∼0.45 FRET value.	DISCUSS
13	19	smFRET	experimental_method	Notably, our smFRET results reveal that U2AF65–Py-tract recognition can be characterized by an ‘extended conformational selection' model (Fig. 7b).	DISCUSS
40	46	U2AF65	protein	Notably, our smFRET results reveal that U2AF65–Py-tract recognition can be characterized by an ‘extended conformational selection' model (Fig. 7b).	DISCUSS
47	55	Py-tract	chemical	Notably, our smFRET results reveal that U2AF65–Py-tract recognition can be characterized by an ‘extended conformational selection' model (Fig. 7b).	DISCUSS
13	21	extended	protein_state	Examples of ‘extended conformational selection' during ligand binding have been characterized for a growing number of macromolecules (for example, adenylate kinase, LAO-binding protein, poly-ubiquitin, maltose-binding protein and the preQ1 riboswitch, among others).	DISCUSS
147	163	adenylate kinase	protein_type	Examples of ‘extended conformational selection' during ligand binding have been characterized for a growing number of macromolecules (for example, adenylate kinase, LAO-binding protein, poly-ubiquitin, maltose-binding protein and the preQ1 riboswitch, among others).	DISCUSS
165	184	LAO-binding protein	protein_type	Examples of ‘extended conformational selection' during ligand binding have been characterized for a growing number of macromolecules (for example, adenylate kinase, LAO-binding protein, poly-ubiquitin, maltose-binding protein and the preQ1 riboswitch, among others).	DISCUSS
186	200	poly-ubiquitin	protein_type	Examples of ‘extended conformational selection' during ligand binding have been characterized for a growing number of macromolecules (for example, adenylate kinase, LAO-binding protein, poly-ubiquitin, maltose-binding protein and the preQ1 riboswitch, among others).	DISCUSS
202	225	maltose-binding protein	protein_type	Examples of ‘extended conformational selection' during ligand binding have been characterized for a growing number of macromolecules (for example, adenylate kinase, LAO-binding protein, poly-ubiquitin, maltose-binding protein and the preQ1 riboswitch, among others).	DISCUSS
234	250	preQ1 riboswitch	protein_type	Examples of ‘extended conformational selection' during ligand binding have been characterized for a growing number of macromolecules (for example, adenylate kinase, LAO-binding protein, poly-ubiquitin, maltose-binding protein and the preQ1 riboswitch, among others).	DISCUSS
33	39	smFRET	experimental_method	Here, the majority of changes in smFRET traces for U2AF651,2LFRET(Cy3/Cy5) bound to slide-tethered RNA began at high (0.65–0.8) FRET value and transition to the predominant 0.45 FRET value (Supplementary Fig. 7c–g).	DISCUSS
40	46	traces	evidence	Here, the majority of changes in smFRET traces for U2AF651,2LFRET(Cy3/Cy5) bound to slide-tethered RNA began at high (0.65–0.8) FRET value and transition to the predominant 0.45 FRET value (Supplementary Fig. 7c–g).	DISCUSS
51	65	U2AF651,2LFRET	mutant	Here, the majority of changes in smFRET traces for U2AF651,2LFRET(Cy3/Cy5) bound to slide-tethered RNA began at high (0.65–0.8) FRET value and transition to the predominant 0.45 FRET value (Supplementary Fig. 7c–g).	DISCUSS
66	69	Cy3	chemical	Here, the majority of changes in smFRET traces for U2AF651,2LFRET(Cy3/Cy5) bound to slide-tethered RNA began at high (0.65–0.8) FRET value and transition to the predominant 0.45 FRET value (Supplementary Fig. 7c–g).	DISCUSS
70	73	Cy5	chemical	Here, the majority of changes in smFRET traces for U2AF651,2LFRET(Cy3/Cy5) bound to slide-tethered RNA began at high (0.65–0.8) FRET value and transition to the predominant 0.45 FRET value (Supplementary Fig. 7c–g).	DISCUSS
75	83	bound to	protein_state	Here, the majority of changes in smFRET traces for U2AF651,2LFRET(Cy3/Cy5) bound to slide-tethered RNA began at high (0.65–0.8) FRET value and transition to the predominant 0.45 FRET value (Supplementary Fig. 7c–g).	DISCUSS
99	102	RNA	chemical	Here, the majority of changes in smFRET traces for U2AF651,2LFRET(Cy3/Cy5) bound to slide-tethered RNA began at high (0.65–0.8) FRET value and transition to the predominant 0.45 FRET value (Supplementary Fig. 7c–g).	DISCUSS
128	138	FRET value	evidence	Here, the majority of changes in smFRET traces for U2AF651,2LFRET(Cy3/Cy5) bound to slide-tethered RNA began at high (0.65–0.8) FRET value and transition to the predominant 0.45 FRET value (Supplementary Fig. 7c–g).	DISCUSS
178	188	FRET value	evidence	Here, the majority of changes in smFRET traces for U2AF651,2LFRET(Cy3/Cy5) bound to slide-tethered RNA began at high (0.65–0.8) FRET value and transition to the predominant 0.45 FRET value (Supplementary Fig. 7c–g).	DISCUSS
62	68	closed	protein_state	These transitions could correspond to rearrangement from the ‘closed' NMR/PRE-based U2AF65 conformation in which the RNA-binding surface of only a single RRM is exposed and available for RNA binding, to the structural state seen in the side-by-side, RNA-bound crystal structure.	DISCUSS
70	73	NMR	experimental_method	These transitions could correspond to rearrangement from the ‘closed' NMR/PRE-based U2AF65 conformation in which the RNA-binding surface of only a single RRM is exposed and available for RNA binding, to the structural state seen in the side-by-side, RNA-bound crystal structure.	DISCUSS
74	77	PRE	experimental_method	These transitions could correspond to rearrangement from the ‘closed' NMR/PRE-based U2AF65 conformation in which the RNA-binding surface of only a single RRM is exposed and available for RNA binding, to the structural state seen in the side-by-side, RNA-bound crystal structure.	DISCUSS
84	90	U2AF65	protein	These transitions could correspond to rearrangement from the ‘closed' NMR/PRE-based U2AF65 conformation in which the RNA-binding surface of only a single RRM is exposed and available for RNA binding, to the structural state seen in the side-by-side, RNA-bound crystal structure.	DISCUSS
117	136	RNA-binding surface	site	These transitions could correspond to rearrangement from the ‘closed' NMR/PRE-based U2AF65 conformation in which the RNA-binding surface of only a single RRM is exposed and available for RNA binding, to the structural state seen in the side-by-side, RNA-bound crystal structure.	DISCUSS
147	153	single	protein_state	These transitions could correspond to rearrangement from the ‘closed' NMR/PRE-based U2AF65 conformation in which the RNA-binding surface of only a single RRM is exposed and available for RNA binding, to the structural state seen in the side-by-side, RNA-bound crystal structure.	DISCUSS
154	157	RRM	structure_element	These transitions could correspond to rearrangement from the ‘closed' NMR/PRE-based U2AF65 conformation in which the RNA-binding surface of only a single RRM is exposed and available for RNA binding, to the structural state seen in the side-by-side, RNA-bound crystal structure.	DISCUSS
236	248	side-by-side	protein_state	These transitions could correspond to rearrangement from the ‘closed' NMR/PRE-based U2AF65 conformation in which the RNA-binding surface of only a single RRM is exposed and available for RNA binding, to the structural state seen in the side-by-side, RNA-bound crystal structure.	DISCUSS
250	259	RNA-bound	protein_state	These transitions could correspond to rearrangement from the ‘closed' NMR/PRE-based U2AF65 conformation in which the RNA-binding surface of only a single RRM is exposed and available for RNA binding, to the structural state seen in the side-by-side, RNA-bound crystal structure.	DISCUSS
260	277	crystal structure	evidence	These transitions could correspond to rearrangement from the ‘closed' NMR/PRE-based U2AF65 conformation in which the RNA-binding surface of only a single RRM is exposed and available for RNA binding, to the structural state seen in the side-by-side, RNA-bound crystal structure.	DISCUSS
13	19	smFRET	experimental_method	As such, the smFRET approach reconciles prior inconsistencies between two major conformations that were detected by NMR/PRE experiments and a broad ensemble of diverse inter-RRM arrangements that fit the SAXS data for the apo-protein.	DISCUSS
116	119	NMR	experimental_method	As such, the smFRET approach reconciles prior inconsistencies between two major conformations that were detected by NMR/PRE experiments and a broad ensemble of diverse inter-RRM arrangements that fit the SAXS data for the apo-protein.	DISCUSS
120	123	PRE	experimental_method	As such, the smFRET approach reconciles prior inconsistencies between two major conformations that were detected by NMR/PRE experiments and a broad ensemble of diverse inter-RRM arrangements that fit the SAXS data for the apo-protein.	DISCUSS
168	177	inter-RRM	structure_element	As such, the smFRET approach reconciles prior inconsistencies between two major conformations that were detected by NMR/PRE experiments and a broad ensemble of diverse inter-RRM arrangements that fit the SAXS data for the apo-protein.	DISCUSS
204	208	SAXS	experimental_method	As such, the smFRET approach reconciles prior inconsistencies between two major conformations that were detected by NMR/PRE experiments and a broad ensemble of diverse inter-RRM arrangements that fit the SAXS data for the apo-protein.	DISCUSS
222	225	apo	protein_state	As such, the smFRET approach reconciles prior inconsistencies between two major conformations that were detected by NMR/PRE experiments and a broad ensemble of diverse inter-RRM arrangements that fit the SAXS data for the apo-protein.	DISCUSS
226	233	protein	protein	As such, the smFRET approach reconciles prior inconsistencies between two major conformations that were detected by NMR/PRE experiments and a broad ensemble of diverse inter-RRM arrangements that fit the SAXS data for the apo-protein.	DISCUSS
176	179	RRM	structure_element	Similar interdisciplinary structural approaches are likely to illuminate whether similar mechanistic bases for RNA binding are widespread among other members of the vast multi-RRM family.	DISCUSS
17	23	U2AF65	protein	The finding that U2AF65 recognizes a nine base pair Py tract contributes to an elusive ‘code' for predicting splicing patterns from primary sequences in the post-genomic era (reviewed in ref.).	DISCUSS
52	60	Py tract	chemical	The finding that U2AF65 recognizes a nine base pair Py tract contributes to an elusive ‘code' for predicting splicing patterns from primary sequences in the post-genomic era (reviewed in ref.).	DISCUSS
21	35	RNA affinities	evidence	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
39	45	U2AF65	protein	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
50	60	U2AF651,2L	mutant	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
110	120	U2AF651,2L	mutant	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
121	131	structures	evidence	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
188	197	penalties	evidence	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
201	227	structure-guided mutations	experimental_method	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
231	262	RNA binding and splicing assays	experimental_method	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
284	292	extended	protein_state	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
293	310	inter-RRM regions	structure_element	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
318	328	U2AF651,2L	mutant	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
329	339	structures	evidence	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
357	365	Py-tract	chemical	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
385	396	full-length	protein_state	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
397	403	U2AF65	protein	Based on (i) similar RNA affinities of U2AF65 and U2AF651,2L, (ii) indistinguishable conformations among four U2AF651,2L structures in two different crystal packing arrangements and (iii) penalties of structure-guided mutations in RNA binding and splicing assays, we suggest that the extended inter-RRM regions of the U2AF651,2L structures underlie cognate Py-tract recognition by the full-length U2AF65 protein.	DISCUSS
59	62	SF1	protein	Further research will be needed to understand the roles of SF1 and U2AF35 subunits in the conformational equilibria underlying U2AF65 association with Py tracts.	DISCUSS
67	73	U2AF35	protein	Further research will be needed to understand the roles of SF1 and U2AF35 subunits in the conformational equilibria underlying U2AF65 association with Py tracts.	DISCUSS
127	133	U2AF65	protein	Further research will be needed to understand the roles of SF1 and U2AF35 subunits in the conformational equilibria underlying U2AF65 association with Py tracts.	DISCUSS
151	160	Py tracts	chemical	Further research will be needed to understand the roles of SF1 and U2AF35 subunits in the conformational equilibria underlying U2AF65 association with Py tracts.	DISCUSS
39	45	U2AF65	protein	Moreover, structural differences among U2AF65 homologues and paralogues may regulate splice site selection.	DISCUSS
85	96	splice site	site	Moreover, structural differences among U2AF65 homologues and paralogues may regulate splice site selection.	DISCUSS
63	78	3′ splice sites	site	Ultimately, these guidelines will assist the identification of 3′ splice sites and the relationship of disease-causing mutations to penalties for U2AF65 association.	DISCUSS
146	152	U2AF65	protein	Ultimately, these guidelines will assist the identification of 3′ splice sites and the relationship of disease-causing mutations to penalties for U2AF65 association.	DISCUSS
4	10	intact	protein_state	The intact U2AF65 RRM1/RRM2-containing domain and flanking residues are required for binding contiguous Py tracts.	FIG
11	17	U2AF65	protein	The intact U2AF65 RRM1/RRM2-containing domain and flanking residues are required for binding contiguous Py tracts.	FIG
18	22	RRM1	structure_element	The intact U2AF65 RRM1/RRM2-containing domain and flanking residues are required for binding contiguous Py tracts.	FIG
23	27	RRM2	structure_element	The intact U2AF65 RRM1/RRM2-containing domain and flanking residues are required for binding contiguous Py tracts.	FIG
93	103	contiguous	structure_element	The intact U2AF65 RRM1/RRM2-containing domain and flanking residues are required for binding contiguous Py tracts.	FIG
104	113	Py tracts	chemical	The intact U2AF65 RRM1/RRM2-containing domain and flanking residues are required for binding contiguous Py tracts.	FIG
27	38	full-length	protein_state	(a) Domain organization of full-length (fl) U2AF65 and constructs used for RNA binding and structural experiments.	FIG
40	42	fl	protein_state	(a) Domain organization of full-length (fl) U2AF65 and constructs used for RNA binding and structural experiments.	FIG
44	50	U2AF65	protein	(a) Domain organization of full-length (fl) U2AF65 and constructs used for RNA binding and structural experiments.	FIG
75	78	RNA	chemical	(a) Domain organization of full-length (fl) U2AF65 and constructs used for RNA binding and structural experiments.	FIG
22	23	d	mutant	An internal deletion (d, Δ) of residues 238–257 removes a portion of the inter-RRM linker from the dU2AF651,2 and dU2AF651,2L constructs.	FIG
25	26	Δ	mutant	An internal deletion (d, Δ) of residues 238–257 removes a portion of the inter-RRM linker from the dU2AF651,2 and dU2AF651,2L constructs.	FIG
40	47	238–257	residue_range	An internal deletion (d, Δ) of residues 238–257 removes a portion of the inter-RRM linker from the dU2AF651,2 and dU2AF651,2L constructs.	FIG
73	89	inter-RRM linker	structure_element	An internal deletion (d, Δ) of residues 238–257 removes a portion of the inter-RRM linker from the dU2AF651,2 and dU2AF651,2L constructs.	FIG
99	109	dU2AF651,2	mutant	An internal deletion (d, Δ) of residues 238–257 removes a portion of the inter-RRM linker from the dU2AF651,2 and dU2AF651,2L constructs.	FIG
114	125	dU2AF651,2L	mutant	An internal deletion (d, Δ) of residues 238–257 removes a portion of the inter-RRM linker from the dU2AF651,2 and dU2AF651,2L constructs.	FIG
31	53	equilibrium affinities	evidence	(b) Comparison of the apparent equilibrium affinities of various U2AF65 constructs for binding the prototypical AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
65	71	U2AF65	protein	(b) Comparison of the apparent equilibrium affinities of various U2AF65 constructs for binding the prototypical AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
112	116	AdML	gene	(b) Comparison of the apparent equilibrium affinities of various U2AF65 constructs for binding the prototypical AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
117	125	Py tract	chemical	(b) Comparison of the apparent equilibrium affinities of various U2AF65 constructs for binding the prototypical AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
127	146	5′-CCCUUUUUUUUCC-3′	chemical	(b) Comparison of the apparent equilibrium affinities of various U2AF65 constructs for binding the prototypical AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
4	12	flU2AF65	protein	The flU2AF65 protein includes a heterodimerization domain of the U2AF35 subunit to promote solubility and folding.	FIG
32	57	heterodimerization domain	structure_element	The flU2AF65 protein includes a heterodimerization domain of the U2AF35 subunit to promote solubility and folding.	FIG
65	71	U2AF35	protein	The flU2AF65 protein includes a heterodimerization domain of the U2AF35 subunit to promote solubility and folding.	FIG
13	47	equilibrium dissociation constants	evidence	The apparent equilibrium dissociation constants (KD) for binding the AdML 13mer are as follows: flU2AF65, 30±3 nM; U2AF651,2L, 35±6 nM; U2AF651,2, 3,600±300 nM. (c) Comparison of the RNA sequence specificities of flU2AF65 and U2AF651,2L constructs binding C-rich Py tracts with 4U's embedded in either the 5′- (light grey fill) or 3′- (dark grey fill) regions.	FIG
49	51	KD	evidence	The apparent equilibrium dissociation constants (KD) for binding the AdML 13mer are as follows: flU2AF65, 30±3 nM; U2AF651,2L, 35±6 nM; U2AF651,2, 3,600±300 nM. (c) Comparison of the RNA sequence specificities of flU2AF65 and U2AF651,2L constructs binding C-rich Py tracts with 4U's embedded in either the 5′- (light grey fill) or 3′- (dark grey fill) regions.	FIG
69	73	AdML	gene	The apparent equilibrium dissociation constants (KD) for binding the AdML 13mer are as follows: flU2AF65, 30±3 nM; U2AF651,2L, 35±6 nM; U2AF651,2, 3,600±300 nM. (c) Comparison of the RNA sequence specificities of flU2AF65 and U2AF651,2L constructs binding C-rich Py tracts with 4U's embedded in either the 5′- (light grey fill) or 3′- (dark grey fill) regions.	FIG
96	104	flU2AF65	protein	The apparent equilibrium dissociation constants (KD) for binding the AdML 13mer are as follows: flU2AF65, 30±3 nM; U2AF651,2L, 35±6 nM; U2AF651,2, 3,600±300 nM. (c) Comparison of the RNA sequence specificities of flU2AF65 and U2AF651,2L constructs binding C-rich Py tracts with 4U's embedded in either the 5′- (light grey fill) or 3′- (dark grey fill) regions.	FIG
115	125	U2AF651,2L	mutant	The apparent equilibrium dissociation constants (KD) for binding the AdML 13mer are as follows: flU2AF65, 30±3 nM; U2AF651,2L, 35±6 nM; U2AF651,2, 3,600±300 nM. (c) Comparison of the RNA sequence specificities of flU2AF65 and U2AF651,2L constructs binding C-rich Py tracts with 4U's embedded in either the 5′- (light grey fill) or 3′- (dark grey fill) regions.	FIG
136	145	U2AF651,2	mutant	The apparent equilibrium dissociation constants (KD) for binding the AdML 13mer are as follows: flU2AF65, 30±3 nM; U2AF651,2L, 35±6 nM; U2AF651,2, 3,600±300 nM. (c) Comparison of the RNA sequence specificities of flU2AF65 and U2AF651,2L constructs binding C-rich Py tracts with 4U's embedded in either the 5′- (light grey fill) or 3′- (dark grey fill) regions.	FIG
183	209	RNA sequence specificities	evidence	The apparent equilibrium dissociation constants (KD) for binding the AdML 13mer are as follows: flU2AF65, 30±3 nM; U2AF651,2L, 35±6 nM; U2AF651,2, 3,600±300 nM. (c) Comparison of the RNA sequence specificities of flU2AF65 and U2AF651,2L constructs binding C-rich Py tracts with 4U's embedded in either the 5′- (light grey fill) or 3′- (dark grey fill) regions.	FIG
213	221	flU2AF65	protein	The apparent equilibrium dissociation constants (KD) for binding the AdML 13mer are as follows: flU2AF65, 30±3 nM; U2AF651,2L, 35±6 nM; U2AF651,2, 3,600±300 nM. (c) Comparison of the RNA sequence specificities of flU2AF65 and U2AF651,2L constructs binding C-rich Py tracts with 4U's embedded in either the 5′- (light grey fill) or 3′- (dark grey fill) regions.	FIG
226	236	U2AF651,2L	mutant	The apparent equilibrium dissociation constants (KD) for binding the AdML 13mer are as follows: flU2AF65, 30±3 nM; U2AF651,2L, 35±6 nM; U2AF651,2, 3,600±300 nM. (c) Comparison of the RNA sequence specificities of flU2AF65 and U2AF651,2L constructs binding C-rich Py tracts with 4U's embedded in either the 5′- (light grey fill) or 3′- (dark grey fill) regions.	FIG
256	262	C-rich	structure_element	The apparent equilibrium dissociation constants (KD) for binding the AdML 13mer are as follows: flU2AF65, 30±3 nM; U2AF651,2L, 35±6 nM; U2AF651,2, 3,600±300 nM. (c) Comparison of the RNA sequence specificities of flU2AF65 and U2AF651,2L constructs binding C-rich Py tracts with 4U's embedded in either the 5′- (light grey fill) or 3′- (dark grey fill) regions.	FIG
263	272	Py tracts	chemical	The apparent equilibrium dissociation constants (KD) for binding the AdML 13mer are as follows: flU2AF65, 30±3 nM; U2AF651,2L, 35±6 nM; U2AF651,2, 3,600±300 nM. (c) Comparison of the RNA sequence specificities of flU2AF65 and U2AF651,2L constructs binding C-rich Py tracts with 4U's embedded in either the 5′- (light grey fill) or 3′- (dark grey fill) regions.	FIG
4	6	KD	evidence	The KD's for binding 5′-CCUUUUCCCCCCC-3′ are: flU2AF65, 41±2 nM; U2AF651,2L, 31±3 nM. The KD's for binding 5′-CCCCCCCUUUUCC-3′ are: flU2AF65, 414±12 nM; U2AF651,2L, 417±10 nM. Bar graphs are hatched to match the constructs shown in a. The average apparent equilibrium affinity (KA) and s.e.m. for three independent titrations are plotted.	FIG
21	40	5′-CCUUUUCCCCCCC-3′	chemical	The KD's for binding 5′-CCUUUUCCCCCCC-3′ are: flU2AF65, 41±2 nM; U2AF651,2L, 31±3 nM. The KD's for binding 5′-CCCCCCCUUUUCC-3′ are: flU2AF65, 414±12 nM; U2AF651,2L, 417±10 nM. Bar graphs are hatched to match the constructs shown in a. The average apparent equilibrium affinity (KA) and s.e.m. for three independent titrations are plotted.	FIG
46	54	flU2AF65	protein	The KD's for binding 5′-CCUUUUCCCCCCC-3′ are: flU2AF65, 41±2 nM; U2AF651,2L, 31±3 nM. The KD's for binding 5′-CCCCCCCUUUUCC-3′ are: flU2AF65, 414±12 nM; U2AF651,2L, 417±10 nM. Bar graphs are hatched to match the constructs shown in a. The average apparent equilibrium affinity (KA) and s.e.m. for three independent titrations are plotted.	FIG
65	75	U2AF651,2L	mutant	The KD's for binding 5′-CCUUUUCCCCCCC-3′ are: flU2AF65, 41±2 nM; U2AF651,2L, 31±3 nM. The KD's for binding 5′-CCCCCCCUUUUCC-3′ are: flU2AF65, 414±12 nM; U2AF651,2L, 417±10 nM. Bar graphs are hatched to match the constructs shown in a. The average apparent equilibrium affinity (KA) and s.e.m. for three independent titrations are plotted.	FIG
90	92	KD	evidence	The KD's for binding 5′-CCUUUUCCCCCCC-3′ are: flU2AF65, 41±2 nM; U2AF651,2L, 31±3 nM. The KD's for binding 5′-CCCCCCCUUUUCC-3′ are: flU2AF65, 414±12 nM; U2AF651,2L, 417±10 nM. Bar graphs are hatched to match the constructs shown in a. The average apparent equilibrium affinity (KA) and s.e.m. for three independent titrations are plotted.	FIG
107	126	5′-CCCCCCCUUUUCC-3′	chemical	The KD's for binding 5′-CCUUUUCCCCCCC-3′ are: flU2AF65, 41±2 nM; U2AF651,2L, 31±3 nM. The KD's for binding 5′-CCCCCCCUUUUCC-3′ are: flU2AF65, 414±12 nM; U2AF651,2L, 417±10 nM. Bar graphs are hatched to match the constructs shown in a. The average apparent equilibrium affinity (KA) and s.e.m. for three independent titrations are plotted.	FIG
132	140	flU2AF65	protein	The KD's for binding 5′-CCUUUUCCCCCCC-3′ are: flU2AF65, 41±2 nM; U2AF651,2L, 31±3 nM. The KD's for binding 5′-CCCCCCCUUUUCC-3′ are: flU2AF65, 414±12 nM; U2AF651,2L, 417±10 nM. Bar graphs are hatched to match the constructs shown in a. The average apparent equilibrium affinity (KA) and s.e.m. for three independent titrations are plotted.	FIG
153	163	U2AF651,2L	mutant	The KD's for binding 5′-CCUUUUCCCCCCC-3′ are: flU2AF65, 41±2 nM; U2AF651,2L, 31±3 nM. The KD's for binding 5′-CCCCCCCUUUUCC-3′ are: flU2AF65, 414±12 nM; U2AF651,2L, 417±10 nM. Bar graphs are hatched to match the constructs shown in a. The average apparent equilibrium affinity (KA) and s.e.m. for three independent titrations are plotted.	FIG
239	276	average apparent equilibrium affinity	evidence	The KD's for binding 5′-CCUUUUCCCCCCC-3′ are: flU2AF65, 41±2 nM; U2AF651,2L, 31±3 nM. The KD's for binding 5′-CCCCCCCUUUUCC-3′ are: flU2AF65, 414±12 nM; U2AF651,2L, 417±10 nM. Bar graphs are hatched to match the constructs shown in a. The average apparent equilibrium affinity (KA) and s.e.m. for three independent titrations are plotted.	FIG
278	280	KA	evidence	The KD's for binding 5′-CCUUUUCCCCCCC-3′ are: flU2AF65, 41±2 nM; U2AF651,2L, 31±3 nM. The KD's for binding 5′-CCCCCCCUUUUCC-3′ are: flU2AF65, 414±12 nM; U2AF651,2L, 417±10 nM. Bar graphs are hatched to match the constructs shown in a. The average apparent equilibrium affinity (KA) and s.e.m. for three independent titrations are plotted.	FIG
25	82	average fitted fluorescence anisotropy RNA-binding curves	evidence	The purified protein and average fitted fluorescence anisotropy RNA-binding curves are shown in Supplementary Fig. 1.	FIG
0	3	RRM	structure_element	RRM, RNA recognition motif; RS, arginine-serine rich; UHM, U2AF homology motif; ULM, U2AF ligand motif.	FIG
5	26	RNA recognition motif	structure_element	RRM, RNA recognition motif; RS, arginine-serine rich; UHM, U2AF homology motif; ULM, U2AF ligand motif.	FIG
28	30	RS	structure_element	RRM, RNA recognition motif; RS, arginine-serine rich; UHM, U2AF homology motif; ULM, U2AF ligand motif.	FIG
32	52	arginine-serine rich	structure_element	RRM, RNA recognition motif; RS, arginine-serine rich; UHM, U2AF homology motif; ULM, U2AF ligand motif.	FIG
54	57	UHM	structure_element	RRM, RNA recognition motif; RS, arginine-serine rich; UHM, U2AF homology motif; ULM, U2AF ligand motif.	FIG
59	78	U2AF homology motif	structure_element	RRM, RNA recognition motif; RS, arginine-serine rich; UHM, U2AF homology motif; ULM, U2AF ligand motif.	FIG
80	83	ULM	structure_element	RRM, RNA recognition motif; RS, arginine-serine rich; UHM, U2AF homology motif; ULM, U2AF ligand motif.	FIG
85	102	U2AF ligand motif	structure_element	RRM, RNA recognition motif; RS, arginine-serine rich; UHM, U2AF homology motif; ULM, U2AF ligand motif.	FIG
0	10	Structures	evidence	Structures of U2AF651,2L recognizing a contiguous Py tract.	FIG
14	24	U2AF651,2L	mutant	Structures of U2AF651,2L recognizing a contiguous Py tract.	FIG
39	49	contiguous	structure_element	Structures of U2AF651,2L recognizing a contiguous Py tract.	FIG
50	58	Py tract	chemical	Structures of U2AF651,2L recognizing a contiguous Py tract.	FIG
4	13	Alignment	experimental_method	(a) Alignment of oligonucleotide sequences that were co-crystallized in the indicated U2AF651,2L structures.	FIG
17	32	oligonucleotide	chemical	(a) Alignment of oligonucleotide sequences that were co-crystallized in the indicated U2AF651,2L structures.	FIG
53	68	co-crystallized	experimental_method	(a) Alignment of oligonucleotide sequences that were co-crystallized in the indicated U2AF651,2L structures.	FIG
86	96	U2AF651,2L	mutant	(a) Alignment of oligonucleotide sequences that were co-crystallized in the indicated U2AF651,2L structures.	FIG
97	107	structures	evidence	(a) Alignment of oligonucleotide sequences that were co-crystallized in the indicated U2AF651,2L structures.	FIG
15	19	RRM1	structure_element	The regions of RRM1, RRM2 and linker contacts are indicated above by respective black and blue arrows from N- to C-terminus.	FIG
21	25	RRM2	structure_element	The regions of RRM1, RRM2 and linker contacts are indicated above by respective black and blue arrows from N- to C-terminus.	FIG
30	36	linker	structure_element	The regions of RRM1, RRM2 and linker contacts are indicated above by respective black and blue arrows from N- to C-terminus.	FIG
40	50	U2AF651,2L	mutant	For clarity, we consistently number the U2AF651,2L nucleotide-binding sites from one to nine, although in some cases the co-crystallized oligonucleotide comprises eight nucleotides and as such leaves the first binding site empty.	FIG
51	75	nucleotide-binding sites	site	For clarity, we consistently number the U2AF651,2L nucleotide-binding sites from one to nine, although in some cases the co-crystallized oligonucleotide comprises eight nucleotides and as such leaves the first binding site empty.	FIG
121	136	co-crystallized	experimental_method	For clarity, we consistently number the U2AF651,2L nucleotide-binding sites from one to nine, although in some cases the co-crystallized oligonucleotide comprises eight nucleotides and as such leaves the first binding site empty.	FIG
137	152	oligonucleotide	chemical	For clarity, we consistently number the U2AF651,2L nucleotide-binding sites from one to nine, although in some cases the co-crystallized oligonucleotide comprises eight nucleotides and as such leaves the first binding site empty.	FIG
169	180	nucleotides	chemical	For clarity, we consistently number the U2AF651,2L nucleotide-binding sites from one to nine, although in some cases the co-crystallized oligonucleotide comprises eight nucleotides and as such leaves the first binding site empty.	FIG
204	222	first binding site	site	For clarity, we consistently number the U2AF651,2L nucleotide-binding sites from one to nine, although in some cases the co-crystallized oligonucleotide comprises eight nucleotides and as such leaves the first binding site empty.	FIG
10	20	dU2AF651,2	mutant	The prior dU2AF651,2 nucleotide-binding sites are given in parentheses (site 4' interacts with dU2AF65 RRM1 and RRM2 by crystallographic symmetry).	FIG
21	45	nucleotide-binding sites	site	The prior dU2AF651,2 nucleotide-binding sites are given in parentheses (site 4' interacts with dU2AF65 RRM1 and RRM2 by crystallographic symmetry).	FIG
95	102	dU2AF65	mutant	The prior dU2AF651,2 nucleotide-binding sites are given in parentheses (site 4' interacts with dU2AF65 RRM1 and RRM2 by crystallographic symmetry).	FIG
103	107	RRM1	structure_element	The prior dU2AF651,2 nucleotide-binding sites are given in parentheses (site 4' interacts with dU2AF65 RRM1 and RRM2 by crystallographic symmetry).	FIG
112	116	RRM2	structure_element	The prior dU2AF651,2 nucleotide-binding sites are given in parentheses (site 4' interacts with dU2AF65 RRM1 and RRM2 by crystallographic symmetry).	FIG
31	62	2|Fo|−|Fc| electron density map	evidence	(b) Stereo views of a ‘kicked' 2|Fo|−|Fc| electron density map contoured at 1σ for the inter-RRM linker, N- and C-terminal residues (blue) or bound oligonucleotide of a representative U2AF651,2L structure (structure iv, bound to 5′-(P)rUrUrUdUrUrU(BrdU)dUrC) (magenta).	FIG
87	103	inter-RRM linker	structure_element	(b) Stereo views of a ‘kicked' 2|Fo|−|Fc| electron density map contoured at 1σ for the inter-RRM linker, N- and C-terminal residues (blue) or bound oligonucleotide of a representative U2AF651,2L structure (structure iv, bound to 5′-(P)rUrUrUdUrUrU(BrdU)dUrC) (magenta).	FIG
148	163	oligonucleotide	chemical	(b) Stereo views of a ‘kicked' 2|Fo|−|Fc| electron density map contoured at 1σ for the inter-RRM linker, N- and C-terminal residues (blue) or bound oligonucleotide of a representative U2AF651,2L structure (structure iv, bound to 5′-(P)rUrUrUdUrUrU(BrdU)dUrC) (magenta).	FIG
184	194	U2AF651,2L	mutant	(b) Stereo views of a ‘kicked' 2|Fo|−|Fc| electron density map contoured at 1σ for the inter-RRM linker, N- and C-terminal residues (blue) or bound oligonucleotide of a representative U2AF651,2L structure (structure iv, bound to 5′-(P)rUrUrUdUrUrU(BrdU)dUrC) (magenta).	FIG
220	228	bound to	protein_state	(b) Stereo views of a ‘kicked' 2|Fo|−|Fc| electron density map contoured at 1σ for the inter-RRM linker, N- and C-terminal residues (blue) or bound oligonucleotide of a representative U2AF651,2L structure (structure iv, bound to 5′-(P)rUrUrUdUrUrU(BrdU)dUrC) (magenta).	FIG
82	92	U2AF651,2L	mutant	Crystallographic statistics are given in Table 1 and the overall conformations of U2AF651,2L and prior dU2AF651,2/U2AF651,2 structures are compared in Supplementary Fig. 2.	FIG
103	113	dU2AF651,2	mutant	Crystallographic statistics are given in Table 1 and the overall conformations of U2AF651,2L and prior dU2AF651,2/U2AF651,2 structures are compared in Supplementary Fig. 2.	FIG
114	123	U2AF651,2	mutant	Crystallographic statistics are given in Table 1 and the overall conformations of U2AF651,2L and prior dU2AF651,2/U2AF651,2 structures are compared in Supplementary Fig. 2.	FIG
124	134	structures	evidence	Crystallographic statistics are given in Table 1 and the overall conformations of U2AF651,2L and prior dU2AF651,2/U2AF651,2 structures are compared in Supplementary Fig. 2.	FIG
0	4	BrdU	chemical	BrdU, 5-bromo-deoxy-uridine; d, deoxy-ribose; P-, 5′-phosphorylation; r, ribose.	FIG
6	27	5-bromo-deoxy-uridine	chemical	BrdU, 5-bromo-deoxy-uridine; d, deoxy-ribose; P-, 5′-phosphorylation; r, ribose.	FIG
29	30	d	chemical	BrdU, 5-bromo-deoxy-uridine; d, deoxy-ribose; P-, 5′-phosphorylation; r, ribose.	FIG
32	44	deoxy-ribose	chemical	BrdU, 5-bromo-deoxy-uridine; d, deoxy-ribose; P-, 5′-phosphorylation; r, ribose.	FIG
46	48	P-	chemical	BrdU, 5-bromo-deoxy-uridine; d, deoxy-ribose; P-, 5′-phosphorylation; r, ribose.	FIG
50	68	5′-phosphorylation	chemical	BrdU, 5-bromo-deoxy-uridine; d, deoxy-ribose; P-, 5′-phosphorylation; r, ribose.	FIG
70	71	r	chemical	BrdU, 5-bromo-deoxy-uridine; d, deoxy-ribose; P-, 5′-phosphorylation; r, ribose.	FIG
73	79	ribose	chemical	BrdU, 5-bromo-deoxy-uridine; d, deoxy-ribose; P-, 5′-phosphorylation; r, ribose.	FIG
28	38	U2AF651,2L	mutant	Representative views of the U2AF651,2L interactions with each new nucleotide of the bound Py tract.	FIG
66	76	nucleotide	chemical	Representative views of the U2AF651,2L interactions with each new nucleotide of the bound Py tract.	FIG
84	89	bound	protein_state	Representative views of the U2AF651,2L interactions with each new nucleotide of the bound Py tract.	FIG
90	98	Py tract	chemical	Representative views of the U2AF651,2L interactions with each new nucleotide of the bound Py tract.	FIG
20	30	U2AF651,2L	mutant	New residues of the U2AF651,2L structures are coloured a darker shade of blue, apart from residues that were tested by site-directed mutagenesis, which are coloured yellow.	FIG
31	41	structures	evidence	New residues of the U2AF651,2L structures are coloured a darker shade of blue, apart from residues that were tested by site-directed mutagenesis, which are coloured yellow.	FIG
119	144	site-directed mutagenesis	experimental_method	New residues of the U2AF651,2L structures are coloured a darker shade of blue, apart from residues that were tested by site-directed mutagenesis, which are coloured yellow.	FIG
4	28	nucleotide-binding sites	site	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
36	46	U2AF651,2L	mutant	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
57	67	dU2AF651,2	mutant	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
68	77	structure	evidence	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
123	165	first and seventh U2AF651,2L-binding sites	site	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
195	209	dU2AF651,2–RNA	complex_assembly	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
210	219	structure	evidence	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
275	285	U2AF651,2L	mutant	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
286	296	structures	evidence	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
362	372	ninth site	site	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
438	448	U2AF651,2L	mutant	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
449	458	structure	evidence	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
499	516	ribose nucleotide	chemical	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
540	543	rU2	residue_name_number	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
565	568	rU3	residue_name_number	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
591	594	rU4	residue_name_number	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
615	618	rU5	residue_name_number	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
641	644	rU6	residue_name_number	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
666	669	dU8	residue_name_number	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
692	695	dU9	residue_name_number	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
718	721	rC9	residue_name_number	The nucleotide-binding sites of the U2AF651,2L and prior dU2AF651,2 structure are compared in Supplementary Fig. 3a–h. The first and seventh U2AF651,2L-binding sites are unchanged from the prior dU2AF651,2–RNA structure and are portrayed in Supplementary Fig. 3a,f. The four U2AF651,2L structures are similar with the exception of pH-dependent variations at the ninth site that are detailed in Supplementary Fig. 3i,j. The representative U2AF651,2L structure shown has the highest resolution and/or ribose nucleotide at the given site: (a) rU2 of structure iv; (b) rU3 of structure iii; (c) rU4 of structure i; (d) rU5 of structure iii; (e) rU6 of structure ii; (f) dU8 of structure iii; (g) dU9 of structure iii; (h) rC9 of structure iv.	FIG
26	48	equilibrium affinities	evidence	(i) Bar graph of apparent equilibrium affinities (KA) of the wild type (blue) and the indicated mutant (yellow) U2AF651,2L proteins binding the AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
50	52	KA	evidence	(i) Bar graph of apparent equilibrium affinities (KA) of the wild type (blue) and the indicated mutant (yellow) U2AF651,2L proteins binding the AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
61	70	wild type	protein_state	(i) Bar graph of apparent equilibrium affinities (KA) of the wild type (blue) and the indicated mutant (yellow) U2AF651,2L proteins binding the AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
96	102	mutant	protein_state	(i) Bar graph of apparent equilibrium affinities (KA) of the wild type (blue) and the indicated mutant (yellow) U2AF651,2L proteins binding the AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
112	122	U2AF651,2L	mutant	(i) Bar graph of apparent equilibrium affinities (KA) of the wild type (blue) and the indicated mutant (yellow) U2AF651,2L proteins binding the AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
144	148	AdML	gene	(i) Bar graph of apparent equilibrium affinities (KA) of the wild type (blue) and the indicated mutant (yellow) U2AF651,2L proteins binding the AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
149	157	Py tract	chemical	(i) Bar graph of apparent equilibrium affinities (KA) of the wild type (blue) and the indicated mutant (yellow) U2AF651,2L proteins binding the AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
159	178	5′-CCCUUUUUUUUCC-3′	chemical	(i) Bar graph of apparent equilibrium affinities (KA) of the wild type (blue) and the indicated mutant (yellow) U2AF651,2L proteins binding the AdML Py tract (5′-CCCUUUUUUUUCC-3′).	FIG
13	47	equilibrium dissociation constants	evidence	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; R227A, 166±2 nM; V254P, 137±10 nM; Q147A, 171±21 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
49	51	KD	evidence	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; R227A, 166±2 nM; V254P, 137±10 nM; Q147A, 171±21 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
60	70	U2AF651,2L	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; R227A, 166±2 nM; V254P, 137±10 nM; Q147A, 171±21 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
71	77	mutant	protein_state	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; R227A, 166±2 nM; V254P, 137±10 nM; Q147A, 171±21 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
92	101	wild type	protein_state	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; R227A, 166±2 nM; V254P, 137±10 nM; Q147A, 171±21 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
103	105	WT	protein_state	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; R227A, 166±2 nM; V254P, 137±10 nM; Q147A, 171±21 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
117	122	R227A	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; R227A, 166±2 nM; V254P, 137±10 nM; Q147A, 171±21 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
134	139	V254P	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; R227A, 166±2 nM; V254P, 137±10 nM; Q147A, 171±21 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
152	157	Q147A	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; R227A, 166±2 nM; V254P, 137±10 nM; Q147A, 171±21 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
182	184	KA	evidence	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; R227A, 166±2 nM; V254P, 137±10 nM; Q147A, 171±21 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
43	61	RNA-binding curves	evidence	The average fitted fluorescence anisotropy RNA-binding curves are shown in Supplementary Fig. 4a–c.	FIG
4	10	U2AF65	protein	The U2AF65 linker/RRM and inter-RRM interactions.	FIG
11	17	linker	structure_element	The U2AF65 linker/RRM and inter-RRM interactions.	FIG
18	21	RRM	structure_element	The U2AF65 linker/RRM and inter-RRM interactions.	FIG
32	35	RRM	structure_element	The U2AF65 linker/RRM and inter-RRM interactions.	FIG
20	26	U2AF65	protein	(a) Contacts of the U2AF65 inter-RRM linker with the RRMs.	FIG
27	43	inter-RRM linker	structure_element	(a) Contacts of the U2AF65 inter-RRM linker with the RRMs.	FIG
53	57	RRMs	structure_element	(a) Contacts of the U2AF65 inter-RRM linker with the RRMs.	FIG
58	62	RRM1	structure_element	A semi-transparent space-filling surface is shown for the RRM1 (green) and RRM2 (light blue).	FIG
75	79	RRM2	structure_element	A semi-transparent space-filling surface is shown for the RRM1 (green) and RRM2 (light blue).	FIG
9	13	V249	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
15	19	V250	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
21	25	V254	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
39	46	mutated	experimental_method	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
50	55	V249G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
56	61	V250G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
62	67	V254G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
75	86	3Gly mutant	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
97	101	S251	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
103	107	T252	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
109	113	V253	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
115	119	P255	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
137	141	V254	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
146	153	mutated	experimental_method	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
157	162	S251G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
163	168	T252G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
169	174	V253G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
175	180	V254G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
181	186	P255G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
194	205	5Gly mutant	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
212	217	S251N	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
218	223	T252L	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
224	229	V253A	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
230	235	V254L	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
236	241	P255A	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
249	261	NLALA mutant	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
272	276	M144	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
278	282	L235	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
284	288	M238	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
290	294	V244	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
296	300	V246	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
321	325	V249	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
327	331	V250	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
333	337	S251	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
339	343	T252	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
345	349	V253	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
351	355	V254	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
357	361	P255	residue_name_number	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
366	373	mutated	experimental_method	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
377	382	M144G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
383	388	L235G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
389	394	M238G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
395	400	V244G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
401	406	V246G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
407	412	V249G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
414	419	V250G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
420	425	S251G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
426	431	T252G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
432	437	V253G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
438	443	V254G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
444	449	P255G	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
457	469	12Gly mutant	mutant	Residues V249, V250, V254 (yellow) are mutated to V249G/V250G/V254G in the 3Gly mutant; residues S251, T252, V253, P255 (red) along with V254 are mutated to S251G/T252G/V253G/V254G/P255G in the 5Gly mutant or to S251N/T252L/V253A/V254L/P255A in the NLALA mutant; residues M144, L235, M238, V244, V246 (orange) along with V249, V250, S251, T252, V253, V254, P255 are mutated to M144G/L235G/M238G/V244G/V246G/V249G/ V250G/S251G/T252G/V253G/V254G/P255G in the 12Gly mutant.	FIG
6	12	linker	structure_element	Other linker residues are coloured either dark blue for new residues in the U2AF651,2L structure or light blue for the remaining inter-RRM residues.	FIG
76	86	U2AF651,2L	mutant	Other linker residues are coloured either dark blue for new residues in the U2AF651,2L structure or light blue for the remaining inter-RRM residues.	FIG
129	138	inter-RRM	structure_element	Other linker residues are coloured either dark blue for new residues in the U2AF651,2L structure or light blue for the remaining inter-RRM residues.	FIG
150	172	central linker regions	structure_element	The central panel shows an overall view with stick diagrams for mutated residues; boxed regions are expanded to show the C-terminal (bottom left) and central linker regions (top) at the inter-RRM interfaces, and N-terminal linker region contacts with RRM1 (bottom right).	FIG
186	206	inter-RRM interfaces	structure_element	The central panel shows an overall view with stick diagrams for mutated residues; boxed regions are expanded to show the C-terminal (bottom left) and central linker regions (top) at the inter-RRM interfaces, and N-terminal linker region contacts with RRM1 (bottom right).	FIG
251	255	RRM1	structure_element	The central panel shows an overall view with stick diagrams for mutated residues; boxed regions are expanded to show the C-terminal (bottom left) and central linker regions (top) at the inter-RRM interfaces, and N-terminal linker region contacts with RRM1 (bottom right).	FIG
26	48	equilibrium affinities	evidence	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
50	52	KA	evidence	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
62	66	AdML	gene	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
67	75	Py tract	chemical	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
77	96	5′-CCCUUUUUUUUCC-3′	chemical	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
105	114	wild-type	protein_state	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
122	132	U2AF651,2L	mutant	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
193	197	3Gly	mutant	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
208	212	5Gly	mutant	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
220	225	NLALA	mutant	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
241	246	12Gly	mutant	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
264	280	linker deletions	experimental_method	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
281	291	dU2AF651,2	mutant	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
299	306	minimal	protein_state	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
307	323	RRM1–RRM2 region	structure_element	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
334	341	148–237	residue_range	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
343	350	258–336	residue_range	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
355	366	dU2AF651,2L	mutant	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
377	384	141–237	residue_range	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
386	393	258–342	residue_range	(b) Bar graph of apparent equilibrium affinities (KA) for the AdML Py tract (5′-CCCUUUUUUUUCC-3′) of the wild-type (blue) U2AF651,2L protein compared with mutations of the residues shown in a: 3Gly (yellow), 5Gly (red), NLALA (hatched red), 12Gly (orange) and the linker deletions dU2AF651,2 in the minimal RRM1–RRM2 region (residues 148–237, 258–336) or dU2AF651,2L (residues 141–237, 258–342).	FIG
13	47	equilibrium dissociation constants	evidence	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
49	51	KD	evidence	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
60	70	U2AF651,2L	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
71	77	mutant	protein_state	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
92	101	wild type	protein_state	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
103	105	WT	protein_state	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
117	121	3Gly	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
132	136	5Gly	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
147	152	12Gly	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
164	169	NLALA	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
180	191	dU2AF651,2L	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
203	213	dU2AF651,2	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
228	232	3Mut	mutant	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
258	260	KA	evidence	The apparent equilibrium dissociation constants (KD) of the U2AF651,2L mutant proteins are: wild type (WT), 35±6 nM; 3Gly, 47±4 nM; 5Gly, 61±3 nM; 12Gly, 88±21 nM; NLALA, 45±3 nM; dU2AF651,2L, 123±5 nM; dU2AF651,2, 5000±100 nM; 3Mut, 5630±70 nM. The average KA and s.e.m. for three independent titrations are plotted.	FIG
35	53	RNA-binding curves	evidence	The fitted fluorescence anisotropy RNA-binding curves are shown in Supplementary Fig. 4d–j. (c) Close view of the U2AF65 RRM1/RRM2 interface following a two-fold rotation about the x-axis relative to a.	FIG
114	120	U2AF65	protein	The fitted fluorescence anisotropy RNA-binding curves are shown in Supplementary Fig. 4d–j. (c) Close view of the U2AF65 RRM1/RRM2 interface following a two-fold rotation about the x-axis relative to a.	FIG
121	140	RRM1/RRM2 interface	site	The fitted fluorescence anisotropy RNA-binding curves are shown in Supplementary Fig. 4d–j. (c) Close view of the U2AF65 RRM1/RRM2 interface following a two-fold rotation about the x-axis relative to a.	FIG
0	6	U2AF65	protein	U2AF65 inter-domain residues are important for splicing a representative pre-mRNA substrate in human cells.	FIG
73	81	pre-mRNA	chemical	U2AF65 inter-domain residues are important for splicing a representative pre-mRNA substrate in human cells.	FIG
95	100	human	species	U2AF65 inter-domain residues are important for splicing a representative pre-mRNA substrate in human cells.	FIG
29	33	pyPY	chemical	(a) Schematic diagram of the pyPY reporter minigene construct comprising two alternative splice sites preceded by either the weak IgM Py tract (py) or the strong AdML Py tract (PY) (sequences inset).	FIG
89	101	splice sites	site	(a) Schematic diagram of the pyPY reporter minigene construct comprising two alternative splice sites preceded by either the weak IgM Py tract (py) or the strong AdML Py tract (PY) (sequences inset).	FIG
134	142	Py tract	chemical	(a) Schematic diagram of the pyPY reporter minigene construct comprising two alternative splice sites preceded by either the weak IgM Py tract (py) or the strong AdML Py tract (PY) (sequences inset).	FIG
144	146	py	chemical	(a) Schematic diagram of the pyPY reporter minigene construct comprising two alternative splice sites preceded by either the weak IgM Py tract (py) or the strong AdML Py tract (PY) (sequences inset).	FIG
162	166	AdML	gene	(a) Schematic diagram of the pyPY reporter minigene construct comprising two alternative splice sites preceded by either the weak IgM Py tract (py) or the strong AdML Py tract (PY) (sequences inset).	FIG
167	175	Py tract	chemical	(a) Schematic diagram of the pyPY reporter minigene construct comprising two alternative splice sites preceded by either the weak IgM Py tract (py) or the strong AdML Py tract (PY) (sequences inset).	FIG
177	179	PY	chemical	(a) Schematic diagram of the pyPY reporter minigene construct comprising two alternative splice sites preceded by either the weak IgM Py tract (py) or the strong AdML Py tract (PY) (sequences inset).	FIG
19	25	RT-PCR	experimental_method	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
29	33	pyPY	chemical	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
65	79	co-transfected	experimental_method	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
109	113	pyPY	chemical	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
134	143	wild-type	protein_state	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
145	147	WT	protein_state	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
149	155	U2AF65	protein	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
168	174	U2AF65	protein	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
175	181	mutant	protein_state	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
183	187	3Mut	mutant	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
192	197	Q147A	mutant	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
199	204	R227A	mutant	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
209	214	V254P	mutant	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
274	276	py	chemical	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
285	289	mRNA	chemical	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
317	321	pyPY	chemical	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
401	407	U2AF65	protein	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
422	424	WT	protein_state	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
425	431	U2AF65	protein	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
439	443	3Mut	mutant	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
444	450	U2AF65	protein	(b) Representative RT-PCR of pyPY transcripts from HEK293T cells co-transfected with constructs encoding the pyPY minigene and either wild-type (WT) U2AF65 or a triple U2AF65 mutant (3Mut) of Q147A, R227A and V254P residues. (c) A bar graph of the average percentage of the py-spliced mRNA relative to total detected pyPY transcripts (spliced and unspliced) for the corresponding gel lanes (black, no U2AF65 added; white, WT U2AF65; grey, 3Mut U2AF65).	FIG
0	22	Protein overexpression	experimental_method	Protein overexpression and qRT-PCR results are shown in Supplementary Fig. 5.	FIG
27	34	qRT-PCR	experimental_method	Protein overexpression and qRT-PCR results are shown in Supplementary Fig. 5.	FIG
27	39	side-by-side	protein_state	RNA binding stabilizes the side-by-side conformation of U2AF65 RRMs.	FIG
56	62	U2AF65	protein	RNA binding stabilizes the side-by-side conformation of U2AF65 RRMs.	FIG
63	67	RRMs	structure_element	RNA binding stabilizes the side-by-side conformation of U2AF65 RRMs.	FIG
15	19	FRET	experimental_method	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
68	72	RRM1	structure_element	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
77	81	RRM2	structure_element	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
89	106	crystal structure	evidence	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
111	123	side-by-side	protein_state	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
125	135	U2AF651,2L	mutant	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
136	140	RRMs	structure_element	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
141	149	bound to	protein_state	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
152	176	Py-tract oligonucleotide	chemical	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
214	220	closed	protein_state	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
222	225	NMR	experimental_method	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
226	229	PRE	experimental_method	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
245	254	U2AF651,2	mutant	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
301	305	RRM2	structure_element	(a,b) Views of FRET pairs chosen to follow the relative movement of RRM1 and RRM2 on the crystal structure of ‘side-by-side' U2AF651,2L RRMs bound to a Py-tract oligonucleotide (a, representative structure iv) or ‘closed' NMR/PRE-based model of U2AF651,2 (b, PDB ID 2YH0) in identical orientations of RRM2.	FIG
4	18	U2AF651,2LFRET	mutant	The U2AF651,2LFRET proteins were doubly labelled at A181C/Q324C such that a mixture of Cy3/Cy5 fluorophores are expected to be present at each site.	FIG
52	57	A181C	mutant	The U2AF651,2LFRET proteins were doubly labelled at A181C/Q324C such that a mixture of Cy3/Cy5 fluorophores are expected to be present at each site.	FIG
58	63	Q324C	mutant	The U2AF651,2LFRET proteins were doubly labelled at A181C/Q324C such that a mixture of Cy3/Cy5 fluorophores are expected to be present at each site.	FIG
87	90	Cy3	chemical	The U2AF651,2LFRET proteins were doubly labelled at A181C/Q324C such that a mixture of Cy3/Cy5 fluorophores are expected to be present at each site.	FIG
91	94	Cy5	chemical	The U2AF651,2LFRET proteins were doubly labelled at A181C/Q324C such that a mixture of Cy3/Cy5 fluorophores are expected to be present at each site.	FIG
95	107	fluorophores	chemical	The U2AF651,2LFRET proteins were doubly labelled at A181C/Q324C such that a mixture of Cy3/Cy5 fluorophores are expected to be present at each site.	FIG
14	28	U2AF651,2LFRET	mutant	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
29	32	Cy3	chemical	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
33	36	Cy5	chemical	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
90	105	biotin-NTA/Ni+2	chemical	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
217	227	absence of	protein_state	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
228	235	ligands	chemical	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
267	271	AdML	gene	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
272	284	Py-tract RNA	chemical	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
286	304	5′-CCUUUUUUUUCC-3′	chemical	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
341	350	adenosine	residue_name	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
371	374	RNA	chemical	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
376	396	5′-CUUUUUAAUUUCCA-3′	chemical	(c–f,i,j) The U2AF651,2LFRET(Cy3/Cy5) protein was immobilized on the microscope slide via biotin-NTA/Ni+2 (orange line) on a neutravidin (black X)-biotin-PEG (orange triangle)-treated surface and imaged either in the absence of ligands (c,d), in the presence of 5 μM AdML Py-tract RNA (5′-CCUUUUUUUUCC-3′) (e,f), or in the presence of 10 μM adenosine-interrupted variant RNA (5′-CUUUUUAAUUUCCA-3′) (i,j).	FIG
4	14	untethered	protein_state	The untethered U2AF651,2LFRET(Cy3/Cy5) protein (1 nM) was added to AdML RNA–polyethylene-glycol-linker–DNA oligonucleotide (10 nM), which was immobilized on the microscope slide by annealing with a complementary biotinyl-DNA oligonucleotide (black vertical line).	FIG
15	29	U2AF651,2LFRET	mutant	The untethered U2AF651,2LFRET(Cy3/Cy5) protein (1 nM) was added to AdML RNA–polyethylene-glycol-linker–DNA oligonucleotide (10 nM), which was immobilized on the microscope slide by annealing with a complementary biotinyl-DNA oligonucleotide (black vertical line).	FIG
30	33	Cy3	chemical	The untethered U2AF651,2LFRET(Cy3/Cy5) protein (1 nM) was added to AdML RNA–polyethylene-glycol-linker–DNA oligonucleotide (10 nM), which was immobilized on the microscope slide by annealing with a complementary biotinyl-DNA oligonucleotide (black vertical line).	FIG
34	37	Cy5	chemical	The untethered U2AF651,2LFRET(Cy3/Cy5) protein (1 nM) was added to AdML RNA–polyethylene-glycol-linker–DNA oligonucleotide (10 nM), which was immobilized on the microscope slide by annealing with a complementary biotinyl-DNA oligonucleotide (black vertical line).	FIG
67	71	AdML	gene	The untethered U2AF651,2LFRET(Cy3/Cy5) protein (1 nM) was added to AdML RNA–polyethylene-glycol-linker–DNA oligonucleotide (10 nM), which was immobilized on the microscope slide by annealing with a complementary biotinyl-DNA oligonucleotide (black vertical line).	FIG
72	122	RNA–polyethylene-glycol-linker–DNA oligonucleotide	chemical	The untethered U2AF651,2LFRET(Cy3/Cy5) protein (1 nM) was added to AdML RNA–polyethylene-glycol-linker–DNA oligonucleotide (10 nM), which was immobilized on the microscope slide by annealing with a complementary biotinyl-DNA oligonucleotide (black vertical line).	FIG
212	240	biotinyl-DNA oligonucleotide	chemical	The untethered U2AF651,2LFRET(Cy3/Cy5) protein (1 nM) was added to AdML RNA–polyethylene-glycol-linker–DNA oligonucleotide (10 nM), which was immobilized on the microscope slide by annealing with a complementary biotinyl-DNA oligonucleotide (black vertical line).	FIG
8	28	single-molecule FRET	experimental_method	Typical single-molecule FRET traces (c,e,g,i) show fluorescence intensities from Cy3 (green) and Cy5 (red) and the calculated apparent FRET efficiency (blue).	FIG
29	35	traces	evidence	Typical single-molecule FRET traces (c,e,g,i) show fluorescence intensities from Cy3 (green) and Cy5 (red) and the calculated apparent FRET efficiency (blue).	FIG
81	84	Cy3	chemical	Typical single-molecule FRET traces (c,e,g,i) show fluorescence intensities from Cy3 (green) and Cy5 (red) and the calculated apparent FRET efficiency (blue).	FIG
97	100	Cy5	chemical	Typical single-molecule FRET traces (c,e,g,i) show fluorescence intensities from Cy3 (green) and Cy5 (red) and the calculated apparent FRET efficiency (blue).	FIG
115	150	calculated apparent FRET efficiency	evidence	Typical single-molecule FRET traces (c,e,g,i) show fluorescence intensities from Cy3 (green) and Cy5 (red) and the calculated apparent FRET efficiency (blue).	FIG
11	17	traces	evidence	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
22	32	untethered	protein_state	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
34	43	RNA-bound	protein_state	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
44	58	U2AF651,2LFRET	mutant	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
59	62	Cy3	chemical	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
63	66	Cy5	chemical	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
106	116	Histograms	evidence	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
136	163	distribution of FRET values	evidence	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
167	175	RNA-free	protein_state	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
177	191	slide-tethered	protein_state	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
192	206	U2AF651,2LFRET	mutant	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
207	210	Cy3	chemical	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
211	214	Cy5	chemical	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
221	225	AdML	gene	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
226	235	RNA-bound	protein_state	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
237	251	slide-tethered	protein_state	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
252	266	U2AF651,2LFRET	mutant	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
267	270	Cy3	chemical	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
271	274	Cy5	chemical	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
281	285	AdML	gene	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
286	295	RNA-bound	protein_state	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
297	307	untethered	protein_state	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
308	322	U2AF651,2LFRET	mutant	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
323	326	Cy3	chemical	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
327	330	Cy5	chemical	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
362	371	RNA-bound	protein_state	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
373	387	slide-tethered	protein_state	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
388	402	U2AF651,2LFRET	mutant	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
403	406	Cy3	chemical	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
407	410	Cy5	chemical	Additional traces for untethered, RNA-bound U2AF651,2LFRET(Cy3/Cy5) are shown in Supplementary Fig. 7c,d. Histograms (d,f,h,j) show the distribution of FRET values in RNA-free, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (d); AdML RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (f); AdML RNA-bound, untethered U2AF651,2LFRET(Cy3/Cy5) (h) and adenosine-interrupted RNA-bound, slide-tethered U2AF651,2LFRET(Cy3/Cy5) (j).	FIG
35	41	traces	evidence	N is the number of single-molecule traces compiled for each histogram.	FIG
60	69	histogram	evidence	N is the number of single-molecule traces compiled for each histogram.	FIG
20	26	U2AF65	protein	Schematic models of U2AF65 recognizing the Py tract.	FIG
43	51	Py tract	chemical	Schematic models of U2AF65 recognizing the Py tract.	FIG
19	25	U2AF65	protein	(a) Diagram of the U2AF65, SF1 and U2AF35 splicing factors bound to the consensus elements of the 3′ splice site.	FIG
27	30	SF1	protein	(a) Diagram of the U2AF65, SF1 and U2AF35 splicing factors bound to the consensus elements of the 3′ splice site.	FIG
35	41	U2AF35	protein	(a) Diagram of the U2AF65, SF1 and U2AF35 splicing factors bound to the consensus elements of the 3′ splice site.	FIG
59	67	bound to	protein_state	(a) Diagram of the U2AF65, SF1 and U2AF35 splicing factors bound to the consensus elements of the 3′ splice site.	FIG
98	112	3′ splice site	site	(a) Diagram of the U2AF65, SF1 and U2AF35 splicing factors bound to the consensus elements of the 3′ splice site.	FIG
28	38	U2AF651,2L	mutant	A surface representation of U2AF651,2L is shown bound to nine nucleotides (nt); the relative distances and juxtaposition of the branch point sequence (BPS) and consensus AG dinucleotide at the 3′ splice site are unknown.	FIG
48	56	bound to	protein_state	A surface representation of U2AF651,2L is shown bound to nine nucleotides (nt); the relative distances and juxtaposition of the branch point sequence (BPS) and consensus AG dinucleotide at the 3′ splice site are unknown.	FIG
62	73	nucleotides	chemical	A surface representation of U2AF651,2L is shown bound to nine nucleotides (nt); the relative distances and juxtaposition of the branch point sequence (BPS) and consensus AG dinucleotide at the 3′ splice site are unknown.	FIG
128	149	branch point sequence	site	A surface representation of U2AF651,2L is shown bound to nine nucleotides (nt); the relative distances and juxtaposition of the branch point sequence (BPS) and consensus AG dinucleotide at the 3′ splice site are unknown.	FIG
151	154	BPS	site	A surface representation of U2AF651,2L is shown bound to nine nucleotides (nt); the relative distances and juxtaposition of the branch point sequence (BPS) and consensus AG dinucleotide at the 3′ splice site are unknown.	FIG
170	185	AG dinucleotide	chemical	A surface representation of U2AF651,2L is shown bound to nine nucleotides (nt); the relative distances and juxtaposition of the branch point sequence (BPS) and consensus AG dinucleotide at the 3′ splice site are unknown.	FIG
193	207	3′ splice site	site	A surface representation of U2AF651,2L is shown bound to nine nucleotides (nt); the relative distances and juxtaposition of the branch point sequence (BPS) and consensus AG dinucleotide at the 3′ splice site are unknown.	FIG
33	39	U2AF65	protein	MDS-relevant mutated residues of U2AF65 are shown as yellow spheres (L187 and M144).	FIG
69	73	L187	residue_name_number	MDS-relevant mutated residues of U2AF65 are shown as yellow spheres (L187 and M144).	FIG
78	82	M144	residue_name_number	MDS-relevant mutated residues of U2AF65 are shown as yellow spheres (L187 and M144).	FIG
29	41	Py-tract RNA	chemical	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
75	84	high FRET	evidence	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
110	116	closed	protein_state	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
119	131	back-to-back	protein_state	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
132	135	apo	protein_state	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
136	142	U2AF65	protein	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
164	167	PRE	experimental_method	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
168	171	NMR	experimental_method	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
262	272	FRET value	evidence	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
300	304	open	protein_state	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
307	319	side-by-side	protein_state	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
320	324	RRMs	structure_element	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
337	347	U2AF651,2L	mutant	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
348	366	crystal structures	evidence	(b) Following binding to the Py-tract RNA, a conformation corresponding to high FRET and consistent with the ‘closed', back-to-back apo-U2AF65 model resulting from PRE/NMR characterization (PDB ID 2YH0) often transitions to a conformation corresponding to ∼0.45 FRET value, which is consistent with ‘open', side-by-side RRMs such as the U2AF651,2L crystal structures.	FIG
33	39	U2AF65	protein	Alternatively, a conformation of U2AF65 corresponding to ∼0.45 FRET value can directly bind to RNA; RNA binding stabilizes the ‘open', side-by-side conformation and thus shifts the U2AF65 population towards the ∼0.45 FRET value.	FIG
63	73	FRET value	evidence	Alternatively, a conformation of U2AF65 corresponding to ∼0.45 FRET value can directly bind to RNA; RNA binding stabilizes the ‘open', side-by-side conformation and thus shifts the U2AF65 population towards the ∼0.45 FRET value.	FIG
95	98	RNA	chemical	Alternatively, a conformation of U2AF65 corresponding to ∼0.45 FRET value can directly bind to RNA; RNA binding stabilizes the ‘open', side-by-side conformation and thus shifts the U2AF65 population towards the ∼0.45 FRET value.	FIG
100	103	RNA	chemical	Alternatively, a conformation of U2AF65 corresponding to ∼0.45 FRET value can directly bind to RNA; RNA binding stabilizes the ‘open', side-by-side conformation and thus shifts the U2AF65 population towards the ∼0.45 FRET value.	FIG
128	132	open	protein_state	Alternatively, a conformation of U2AF65 corresponding to ∼0.45 FRET value can directly bind to RNA; RNA binding stabilizes the ‘open', side-by-side conformation and thus shifts the U2AF65 population towards the ∼0.45 FRET value.	FIG
135	147	side-by-side	protein_state	Alternatively, a conformation of U2AF65 corresponding to ∼0.45 FRET value can directly bind to RNA; RNA binding stabilizes the ‘open', side-by-side conformation and thus shifts the U2AF65 population towards the ∼0.45 FRET value.	FIG
181	187	U2AF65	protein	Alternatively, a conformation of U2AF65 corresponding to ∼0.45 FRET value can directly bind to RNA; RNA binding stabilizes the ‘open', side-by-side conformation and thus shifts the U2AF65 population towards the ∼0.45 FRET value.	FIG
217	227	FRET value	evidence	Alternatively, a conformation of U2AF65 corresponding to ∼0.45 FRET value can directly bind to RNA; RNA binding stabilizes the ‘open', side-by-side conformation and thus shifts the U2AF65 population towards the ∼0.45 FRET value.	FIG
0	4	RRM1	structure_element	RRM1, green; RRM2, pale blue; RRM extensions/linker, blue.	FIG
13	17	RRM2	structure_element	RRM1, green; RRM2, pale blue; RRM extensions/linker, blue.	FIG
30	44	RRM extensions	structure_element	RRM1, green; RRM2, pale blue; RRM extensions/linker, blue.	FIG
45	51	linker	structure_element	RRM1, green; RRM2, pale blue; RRM extensions/linker, blue.	FIG