6868 Nucleic Acids Research, 2007, Vol. 35, No. 20 the Emory University Research Committee (J.F.K.), and a grant from the NIH (A.H.C.). Funding to pay the Open Access publication charges for this article was waived by Oxford University Press. Conﬂict of interest statement. None declared. REFERENCES 1. Tran,E.J. and Wente,S.R. (2006) Dynamic nuclear pore complexes: life on the edge. Cell, 125, 1041–1053. 2. Suntharalingam,M. and Wente,S.R. (2003) Peering through the pore. Nuclear pore complex structure, assembly, and function. Dev. Cell, 4, 775–789. 3. Lim,R.Y. and Fahrenkrog,B. (2006) The nuclear pore complex up close. Curr. Opin. Cell Biol., 18, 342–347. 4. Lange,A., Mills,R.E., Lange,C.J., Stewart,M., Devine,S.E. and Corbett,A.H. (2007) Classical nuclear localization signals: deﬁnition, function, and interaction with importin alpha. J. Biol. Chem., 282, 5101–5105. 5. Kalderon,D., Richardson,W.D., Markham,A.F. and Smith,A.E. (1984) Sequence requirements for nuclear location of simian virus 40 large-T antigen. Nature, 311, 33–38. 6. Robbins,J., Dilworth,S.M., Laskey,R.A. and Dingwall,C. (1991) Two interdependent basic domains in nucleoplasmin nuclear targeting sequence: identiﬁcation of a class of bipartite nuclear targeting sequence. Cell, 64, 615–623. 7. Dingwall,C. and Laskey,R.A. (1991) Nuclear targeting sequences – a consensus? Trends Biochem. Sci., 16, 478–481. 8. Pemberton,L.F. and Paschal,B.M. (2005) Mechanisms of receptor-mediated nuclear import and nuclear export. Traﬃc, 6, 187–198. 9. Go¨ rlich,D. and Kutay,U. (1999) Transport between the cell nucleus and the cytoplasm. Annu. Rev. Cell Dev. Biol., 15, 607–660. 10. Bayliss,R., Littlewood,T., Strawn,L.A., Wente,S.R. and Stewart,M. (2002) GLFG and FxFG nucleoporins bind to overlapping sites on importin-beta. J. Biol. Chem., 277, 50597–50606. 11. Dasso,M. The Ran GTPase: theme and variations. Curr. Biol., 12, R502–R508. 12. Stewart,M. (2007) Molecular mechanism of the nuclear protein import cycle. Nat. Rev. Mol. Cell. Biol., 8, 195–208. 13. Stewart,M. (2006) Insights into the molecular mechanism of nuclear traﬃcking using nuclear transport factor 2 (NTF2). Cell Struct. Funct., 25, 217–225. 14. Matsuura,Y. and Stewart,M. (2005) Nup50/Npap60 function in nuclear protein import complex disassembly and importin recycling. EMBO J., 24, 3681–3689. 15. Johnson,A.W., Lund,E. and Dahlberg,J. (2002) Nuclear export of ribosomal subunits. Trends Biochem. Sci., 27, 580–585. 16. Strom,A.C. and Weis,K. (2001) Importin-beta-like nuclear transport receptors. Genome Biol., 2, 3008.1–3008.9. 17. Gerace,L. (1995) Nuclear export signals and the fast track to the cytoplasm. Cell, 82, 341–344. 18. Mattaj,I.W. and Englmeier,L. (1998) Nucleocytoplasmic transport: the soluble phase. Annu. Rev. Biochem., 67, 265–306. 19. Li,A.M., Watson,A. and Fridovich-Keil,J.L. (2003) Scp160p associ- ates with speciﬁc mRNAs in yeast. Nucleic Acids Res., 31, 1830–1837. 20. Weber,V., Wernitznig,A., Hager,G., Harata,M., Frank,P. and Wintersberger,U. (1997) Puriﬁcation and nucleic-acid-binding properties of a Saccharomyces cerevisiae protein involved in the control of ploidy. Eur. J. Biochem., 249, 309–317. 21. Currie,J.R. and Brown,W.T. (1999) KH domain-containing proteins of yeast: absence of a fragile X gene homologue. Am. J. Med. Genet., 84, 272–276. 22. Li,A.M., Vargas,C.A., Brykailo,M.A., Openo,K.K., Corbett,A.H. and Fridovich-Keil,J.L. (2004) Both KH and non-KH domain sequences are required for polyribosome association of Scp160p in yeast. Nucleic Acids Res., 32, 4768–4775. 23. Wintersberger,U., Kuhne,C. and Karwan,A. (1995) Scp160p, a new yeast protein associated with the nuclear membrane and the endoplasmic reticulum, is necessary for maintenance of exact ploidy. Yeast, 11, 929–944. 24. Frey,S., Pool,M. and Seedorf,M. (2001) Scp160p, an RNA-binding, polysome-associated protein, localizes to the endoplasmic reticulum of Saccharomyces cerevisiae in a microtubule-dependent manner. J. Biol. Chem., 276, 15905–15912. 25. Lang,B.D., Li,A., Black-Brewster,H.D. and Fridovich-Keil,J.L. (2001) The brefeldin A resistance protein Bfr1p is a component of polyribosome-associated mRNP complexes in yeast. Nucleic Acids Res., 29, 2567–2574. 26. Mangus,D.A., Evans,M.C. and Jacobson,A. (2003) Poly(A)-binding proteins: multifunctional scaﬀolds for the post-transcriptional control of gene expression. Genome Biol., 4, 223. 27. Brune,C., Munchel,S.E., Fischer,N., Podtelejnikov,A.V. and Weis,K. (2005) Yeast poly(A)-binding protein Pab1 shuttles between the nucleus and the cytoplasm and functions in mRNA export. RNA, 11, 517–531. 28. Dunn,E.F., Hammell,C.M., Hodge,C.A. and Cole,C.N. (2005) Yeast poly(A)-binding protein, Pab1, and PAN, a poly(A) nuclease complex recruited by Pab1, connect mRNA biogenesis to export. Genes Dev., 19, 90–103. 29. Guthrie,C. and Fink,G.R. (1991) Guide to yeast genetics and molecular biology. Meth. Enzymol., 194, 281–302. 30. Sambrook,J., Fritsch,E.F. and Maniatis,T. (1989) Molecular Cloning: A Laboratory Manual, 2nd edn. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York. 31. Seedorf,M., Damelin,M., Kahana,J., Taura,T. and Silver,P.A. (1999) Interactions between a nuclear transporter and a subset of nuclear pore complex proteins depend on Ran GTPase. Mol. Cell. Biol., 19, 1547–1557. 32. Marfatia,K.A., Crafton,E.B., Green,D.M. and Corbett,A.H. (2003) Domain analysis of the Saccharomyces cerevisiae heterogeneous nuclear ribonucleoprotein, Nab2p. Dissecting the requirements for Nab2p-facilitated poly(A) RNA export. J. Biol. Chem., 278, 6731–6740. 33. Matsuura,Y., Lange,A., Harreman,M.T., Corbett,A.H. and Stewart,M. (2003) Structural basis for Nup2p function in cargo release and karyopherin recycling in nuclear import. EMBO J., 22, 5358–5369. 34. Boeke,J.D., Trueheart,J., Natsoulis,G. and Fink,G.R. (1987) 5-Fluoroorotic acid as a selective agent in yeast molecular genetics. Meth. Enzymol., 154, 164–175. 35. Cosentino,G.P., Schmelzle,T., Hagnighat,A., Helliwell,S.B., Hall,M.N. and Sonenberg,N. (2000) Eap1p, a novel eukaryotic translation initiation factor 4E-associated protein. Mol. Cell. Biol., 20, 4604–4613. 36. Mendelsohn,B.A., Li,A.M., Vargas,C.A., Riehman,K., Watson,A. and Fridovich-Keil,J.L. (2003) Genetic and biochemical interactions between SCP160 and EAP1 in yeast. Nucleic Acids Res., 31, 5838–5847. 37. Neville,M. and Rosbash,M. (1999) The NES-Crm1p export pathway is not a major mRNA export route in Saccharomyces cerevisiae. EMBO J., 18, 3746–3756. 38. Yan,C., Lee,L.H. and Davis,L.I. (1998) Crm1p mediates regulated nuclear export of a yeast AP-1-like transcription factor. EMBO J., 17, 7416–7429. 39. Taura,T., Krebber,H. and Silver,P. (1998) A member of the Ran-binding protein family, Yrb2p, is invovled in nuclear protein export. Proc. Natl Acad. Sci., USA, 95, 7427–7432. 40. Lee,M.S., Henry,M. and Silver,P.A. (1996) A protein that shuttles between the nucleus and the cytoplasm is an important mediator of RNA export. Genes Dev., 10, 1233–1246. 41. Nonet,M., Scafe,C., Sexton,J. and Young,R. (1987) Eucaryotic RNA polymerase conditional mutant that rapidly ceases mRNA synthesis. Mol. Cell. Biol., 7, 1602–1611. 42. Segref,A., Sharma,K., Doye,V., Hellwig,A., Huber,J., Luhrman,R. and Hurt,E. (1997) Mex67p, a novel factor for nuclear mRNA export, binds to both poly(A)+ RNA and nuclear pores. EMBO J., 16, 3256–3271. 43. Hurt,E., Strasser,K., Segref,A., Bailer,S., Schlaich,N., Presutti,C., Tollervey,D. and Jansen,R. (2000) Mex67p mediates nuclear export of a variety of RNA polymerase II transcripts. J. Biol. Chem., 275, 8361–8363. 44. Green,D.M., Marfatia,K.A., Crafton,E.B., Zhang,X., Cheng,X. and Corbett,A.H. (2002) Nab2p is required for poly(A) RNA export in