| Structural highlights
Function
[IMA1_MOUSE] Functions in nuclear protein import as an adapter protein for nuclear receptor KPNB1. Binds specifically and directly to substrates containing either a simple or bipartite NLS motif. Docking of the importin/substrate complex to the nuclear pore complex (NPC) is mediated by KPNB1 through binding to nucleoporin FxFG repeats and the complex is subsequently translocated through the pore by an energy requiring, Ran-dependent mechanism. At the nucleoplasmic side of the NPC, Ran binds to importin-beta and the three components separate and importin-alpha and -beta are re-exported from the nucleus to the cytoplasm where GTP hydrolysis releases Ran from importin. The directionality of nuclear import is thought to be conferred by an asymmetric distribution of the GTP- and GDP-bound forms of Ran between the cytoplasm and nucleus. [RCC1_YEAST] Guanine nucleotide exchange factor that promotes the exchange of GSP1/GSP2-bound GDP by GTP and controls RNA metabolism and transport. Involved in yeast pheromone response pathway and in mRNA metabolism. Involved in nuclear pore complex (NPC) assembly and required for mRNA and ribosome nuclear export. Binds chromatin and is involved NPC-mediated transcriptional control.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]
Publication Abstract from PubMed
The translocation of macromolecules into the nucleus is a fundamental eukaryotic process, regulating gene expression, cell division and differentiation, but which is impaired in a range of significant diseases including cancer and viral infection. The import of proteins into the nucleus is generally initiated by a specific, high affinity interaction between nuclear localisation signals (NLSs) and nuclear import receptors in the cytoplasm, and terminated through the disassembly of these complexes in the nucleus. For classical NLSs (cNLSs), this import is mediated by the importin-alpha (IMPalpha) adaptor protein, which in turn binds to IMPbeta to mediate translocation of nuclear cargo across the nuclear envelope. The interaction and disassembly of import receptor:cargo complexes is reliant on the differential localisation of nucleotide bound Ran across the envelope, maintained in its low affinity, GDP-bound form in the cytoplasm, and its high affinity, GTP-bound form in the nucleus. This in turn is maintained by the differential localisation of Ran regulating proteins, with RanGAP in the cytoplasm maintaining Ran in its GDP-bound form, and RanGEF (Prp20 in yeast) in the nucleus maintaining Ran in its GTP-bound form. Here, we describe the 2.1 A resolution x-ray crystal structure of IMPalpha in complex with the NLS of Prp20. We observe 1,091 A(2) of buried surface area mediated by an extensive array of contacts involving residues on armadillo repeats 2-7, utilising both the major and minor NLS binding sites of IMPalpha to contact bipartite NLS clusters (17)RAKKMSK(23) and (3)KR(4), respectively. One notable feature of the major site is the insertion of Prp20NLS Ala(18) between the P0 and P1 NLS sites, noted in only a few classical bipartite NLSs. This study provides a detailed account of the binding mechanism enabling Prp20 interaction with the nuclear import receptor, and additional new information for the interaction between IMPalpha and cargo.
Structural Characterisation of the Nuclear Import Receptor Importin Alpha in Complex with the Bipartite NLS of Prp20.,Roman N, Christie M, Swarbrick CM, Kobe B, Forwood JK PLoS One. 2013 Dec 10;8(12):e82038. doi: 10.1371/journal.pone.0082038., eCollection 2013. PMID:24339986[15]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Clark KL, Sprague GF Jr. Yeast pheromone response pathway: characterization of a suppressor that restores mating to receptorless mutants. Mol Cell Biol. 1989 Jun;9(6):2682-94. PMID:2548085
- ↑ Aebi M, Clark MW, Vijayraghavan U, Abelson J. A yeast mutant, PRP20, altered in mRNA metabolism and maintenance of the nuclear structure, is defective in a gene homologous to the human gene RCC1 which is involved in the control of chromosome condensation. Mol Gen Genet. 1990 Oct;224(1):72-80. PMID:2277633
- ↑ Clark KL, Ohtsubo M, Nishimoto T, Goebl M, Sprague GF Jr. The yeast SRM1 protein and human RCC1 protein share analogous functions. Cell Regul. 1991 Oct;2(10):781-92. PMID:1666302
- ↑ Fleischmann M, Clark MW, Forrester W, Wickens M, Nishimoto T, Aebi M. Analysis of yeast prp20 mutations and functional complementation by the human homologue RCC1, a protein involved in the control of chromosome condensation. Mol Gen Genet. 1991 Jul;227(3):417-23. PMID:1865879
- ↑ Forrester W, Stutz F, Rosbash M, Wickens M. Defects in mRNA 3'-end formation, transcription initiation, and mRNA transport associated with the yeast mutation prp20: possible coupling of mRNA processing and chromatin structure. Genes Dev. 1992 Oct;6(10):1914-26. PMID:1398069
- ↑ Amberg DC, Fleischmann M, Stagljar I, Cole CN, Aebi M. Nuclear PRP20 protein is required for mRNA export. EMBO J. 1993 Jan;12(1):233-41. PMID:7679070
- ↑ Kirkpatrick D, Solomon F. Overexpression of yeast homologs of the mammalian checkpoint gene RCC1 suppresses the class of alpha-tubulin mutations that arrest with excess microtubules. Genetics. 1994 Jun;137(2):381-92. PMID:8070652
- ↑ Hurt E, Hannus S, Schmelzl B, Lau D, Tollervey D, Simos G. A novel in vivo assay reveals inhibition of ribosomal nuclear export in ran-cycle and nucleoporin mutants. J Cell Biol. 1999 Feb 8;144(3):389-401. PMID:9971735
- ↑ Stage-Zimmermann T, Schmidt U, Silver PA. Factors affecting nuclear export of the 60S ribosomal subunit in vivo. Mol Biol Cell. 2000 Nov;11(11):3777-89. PMID:11071906
- ↑ Brodsky AS, Silver PA. Pre-mRNA processing factors are required for nuclear export. RNA. 2000 Dec;6(12):1737-49. PMID:11142374
- ↑ Baker RP, Harreman MT, Eccleston JF, Corbett AH, Stewart M. Interaction between Ran and Mog1 is required for efficient nuclear protein import. J Biol Chem. 2001 Nov 2;276(44):41255-62. Epub 2001 Aug 16. PMID:11509570 doi:10.1074/jbc.M106060200
- ↑ Clement M, Lavallee F, Barbes-Morin G, de Repentigny L, Belhumeur P. Overexpression of Bud5p can suppress mutations in the Gsp1p guanine nucleotide exchange factor Prp20p in Saccharomyces cerevisiae. Mol Genet Genomics. 2001 Sep;266(1):20-7. PMID:11589573
- ↑ Ryan KJ, McCaffery JM, Wente SR. The Ran GTPase cycle is required for yeast nuclear pore complex assembly. J Cell Biol. 2003 Mar 31;160(7):1041-53. Epub 2003 Mar 24. PMID:12654904 doi:10.1083/jcb.200209116
- ↑ Dilworth DJ, Tackett AJ, Rogers RS, Yi EC, Christmas RH, Smith JJ, Siegel AF, Chait BT, Wozniak RW, Aitchison JD. The mobile nucleoporin Nup2p and chromatin-bound Prp20p function in endogenous NPC-mediated transcriptional control. J Cell Biol. 2005 Dec 19;171(6):955-65. PMID:16365162 doi:10.1083/jcb.200509061
- ↑ Roman N, Christie M, Swarbrick CM, Kobe B, Forwood JK. Structural Characterisation of the Nuclear Import Receptor Importin Alpha in Complex with the Bipartite NLS of Prp20. PLoS One. 2013 Dec 10;8(12):e82038. doi: 10.1371/journal.pone.0082038., eCollection 2013. PMID:24339986 doi:http://dx.doi.org/10.1371/journal.pone.0082038
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