1un0

Structural highlights

Function

[IMA1_YEAST] Binds specifically and directly to substrates containing either a simple or bipartite NLS motif. Promotes docking of import substrates to the nuclear envelope. Seems to act as a cytosolic receptor for both simple and bipartite NLS motifs (By similarity).^{[1] [2] [3]} [NUP2_YEAST] Functions as a component of the nuclear pore complex (NPC). NPC components, collectively referred to as nucleoporins (NUPs), can play the role of both NPC structural components and of docking or interaction partners for transiently associated nuclear transport factors. Active directional transport is assured by both, a Phe-Gly (FG) repeat affinity gradient for these transport factors across the NPC and a transport cofactor concentration gradient across the nuclear envelope (GSP1 and GSP2 GTPases associated predominantly with GTP in the nucleus, with GDP in the cytoplasm). As one of the FG repeat nucleoporins NUP2 is involved in interactions with and guidance of nuclear transport receptors such as SRP1-KAP95 (importin alpha and beta) through the NPC. Like the closely related NUP1 it also plays an important role in disassembling and recycling SRP1-KAP95 to the cytoplasm after nuclear import. Upon entry of the heterotrimeric SRP1-KAP95-cargo complex in the nucleus, NUP2 binds through its N-terminus to the SRP1 nuclear localization signal (NLS) binding site, thus accelerating the release of the NLS-cargo. SRP1 in turn is released from NUP2 by binding of the GSP1-GTP associated export factor CSE1. NUP2 may also have a chromatin boundary/insulator activity through indirect interaction with genomic DNA via CSE1 and blocking of heterochromatin spreading.^{[4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]}

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

See Also

• Importin
• Nucleoporin

References

1. ↑ Kussel P, Frasch M. Yeast Srp1, a nuclear protein related to Drosophila and mouse pendulin, is required for normal migration, division, and integrity of nuclei during mitosis. Mol Gen Genet. 1995 Aug 21;248(3):351-63. PMID:7565597
2. ↑ Tabb MM, Tongaonkar P, Vu L, Nomura M. Evidence for separable functions of Srp1p, the yeast homolog of importin alpha (Karyopherin alpha): role for Srp1p and Sts1p in protein degradation. Mol Cell Biol. 2000 Aug;20(16):6062-73. PMID:10913188
3. ↑ Chen L, Romero L, Chuang SM, Tournier V, Joshi KK, Lee JA, Kovvali G, Madura K. Sts1 plays a key role in targeting proteasomes to the nucleus. J Biol Chem. 2011 Jan 28;286(4):3104-18. doi: 10.1074/jbc.M110.135863. Epub 2010 , Nov 12. PMID:21075847 doi:10.1074/jbc.M110.135863
4. ↑ Solsbacher J, Maurer P, Vogel F, Schlenstedt G. Nup2p, a yeast nucleoporin, functions in bidirectional transport of importin alpha. Mol Cell Biol. 2000 Nov;20(22):8468-79. PMID:11046143
5. ↑ Allen NP, Huang L, Burlingame A, Rexach M. Proteomic analysis of nucleoporin interacting proteins. J Biol Chem. 2001 Aug 3;276(31):29268-74. Epub 2001 May 31. PMID:11387327 doi:http://dx.doi.org/10.1074/jbc.M102629200
6. ↑ Dilworth DJ, Suprapto A, Padovan JC, Chait BT, Wozniak RW, Rout MP, Aitchison JD. Nup2p dynamically associates with the distal regions of the yeast nuclear pore complex. J Cell Biol. 2001 Jun 25;153(7):1465-78. PMID:11425876
7. ↑ Denning D, Mykytka B, Allen NP, Huang L, Al Burlingame, Rexach M. The nucleoporin Nup60p functions as a Gsp1p-GTP-sensitive tether for Nup2p at the nuclear pore complex. J Cell Biol. 2001 Sep 3;154(5):937-50. PMID:11535617 doi:http://dx.doi.org/10.1083/jcb.200101007
8. ↑ Bayliss R, Littlewood T, Strawn LA, Wente SR, Stewart M. GLFG and FxFG nucleoporins bind to overlapping sites on importin-beta. J Biol Chem. 2002 Dec 27;277(52):50597-606. Epub 2002 Oct 7. PMID:12372823 doi:10.1074/jbc.M209037200
9. ↑ Allen NP, Patel SS, Huang L, Chalkley RJ, Burlingame A, Lutzmann M, Hurt EC, Rexach M. Deciphering networks of protein interactions at the nuclear pore complex. Mol Cell Proteomics. 2002 Dec;1(12):930-46. PMID:12543930
10. ↑ Ishii K, Arib G, Lin C, Van Houwe G, Laemmli UK. Chromatin boundaries in budding yeast: the nuclear pore connection. Cell. 2002 May 31;109(5):551-62. PMID:12062099
11. ↑ Gilchrist D, Mykytka B, Rexach M. Accelerating the rate of disassembly of karyopherin.cargo complexes. J Biol Chem. 2002 May 17;277(20):18161-72. Epub 2002 Feb 26. PMID:11867631 doi:http://dx.doi.org/10.1074/jbc.M112306200
12. ↑ Pyhtila B, Rexach M. A gradient of affinity for the karyopherin Kap95p along the yeast nuclear pore complex. J Biol Chem. 2003 Oct 24;278(43):42699-709. Epub 2003 Aug 12. PMID:12917401 doi:http://dx.doi.org/10.1074/jbc.M307135200
13. ↑ Denning DP, Patel SS, Uversky V, Fink AL, Rexach M. Disorder in the nuclear pore complex: the FG repeat regions of nucleoporins are natively unfolded. Proc Natl Acad Sci U S A. 2003 Mar 4;100(5):2450-5. Epub 2003 Feb 25. PMID:12604785 doi:10.1073/pnas.0437902100
14. ↑ Gilchrist D, Rexach M. Molecular basis for the rapid dissociation of nuclear localization signals from karyopherin alpha in the nucleoplasm. J Biol Chem. 2003 Dec 19;278(51):51937-49. Epub 2003 Sep 26. PMID:14514698 doi:http://dx.doi.org/10.1074/jbc.M307371200
15. ↑ Strawn LA, Shen T, Shulga N, Goldfarb DS, Wente SR. Minimal nuclear pore complexes define FG repeat domains essential for transport. Nat Cell Biol. 2004 Mar;6(3):197-206. Epub 2004 Feb 22. PMID:15039779 doi:10.1038/ncb1097
16. ↑ Matsuura Y, Lange A, Harreman MT, Corbett AH, Stewart M. Structural basis for Nup2p function in cargo release and karyopherin recycling in nuclear import. EMBO J. 2003 Oct 15;22(20):5358-69. PMID:14532109 doi:10.1093/emboj/cdg538