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+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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
+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