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Gene Review

GSP1  -  Ran GTPase GSP1

Saccharomyces cerevisiae S288c

Synonyms: CNR1, CST17, Chromosome stability protein 17, GTP-binding nuclear protein GSP1/CNR1, GTPase Ran homolog, ...
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Disease relevance of GSP1


High impact information on GSP1

  • We reported previously that heat or ethanol shock in Saccharomyces cerevisiae leads to nuclear retention of most poly(A)+ RNA but heat shock mRNAs (encoding Hsp70 proteins Ssa1p and Ssa4p) are efficiently exported in a process that is independent of the small GTPase Ran/Gsp1p, which is essential for most nucleocytoplasmic transport [2].
  • Cex1p co-purifies with the nuclear tRNA export receptors Los1p and Msn5p, the eukaryotic elongation factor eEF-1A, which delivers aminoacylated tRNAs to the ribosome, and the RanGTPase Gsp1p, but not with Cca1p, a tRNA maturation enzyme that facilitates translocation of non-aminoacylated tRNAs across the nuclear pore complex [3].
  • The nucleoporin Nup60p functions as a Gsp1p-GTP-sensitive tether for Nup2p at the nuclear pore complex [4].
  • Mtr10p interacts in vitro with Gsp1p-GTP, but with low affinity [5].
  • Nuclear import of the MAPK under stress conditions requires the activity of the small GTP binding protein Ran-GSP1, but not the NLS-binding importin alpha/beta heterodimer [6].

Biological context of GSP1

  • GSP1 is an essential gene, and GSP2 is not required for cell viability [7].
  • The small GTPase Ran (encoded by GSP1 and GSP2 in yeast) plays a central role in nucleocytoplasmic transport [8].
  • Like all ras-related GTP-binding proteins, Gsp1p undergoes cycles of GTP hydrolysis and GDP/GTP exchange [1].
  • Although neither mutant was viable when integrated into the genome as a single copy, yeast mildly overexpressing the Gsp1p mutant corresponding Ran F72Y on a centromeric plasmid were viable, confirming that this mutant retained the essential properties of wild-type Ran [9].
  • The small GTPase Gsp1p of Saccharomyces cerevisiae and its homologue Ran play essential roles in several nuclear processes, such as cell-cycle progression, nuclear organization and nucleocytoplasmic traffic of RNA and proteins [10].

Anatomical context of GSP1

  • These data indicate that Yrb1p functions with Gsp1p and suggest that together they can control transport of macromolecules across the nuclear envelope [11].
  • Gsp1p, the essential yeast Ran homologue, is a key regulator of transport across the nuclear pore complex (NPC) [12].
  • Based on this, we assume that Ran/Gsp1p GTPase regulates the cell cycle and the nucleus/cytosol exchange of macromolecules through interactions with effectors that were independent of each other, and are differentially affected by mutation [13].

Associations of GSP1 with chemical compounds

  • RCC1/PRP20 act as guanine nucleotide exchange factors for the nuclear Ras-like Ran/GSP1 proteins [14].
  • We have constructed yeast strains that overproduce either wild-type Gsp1 or a form of Gsp1 with glycine-21 converted to valine (Gsp1-G21V), which we show stabilizes the GTP-bound form [15].

Physical interactions of GSP1

  • A mutation in the highly conserved Ran binding region of Yrb1p reduces its ability to interact with Gsp1p [11].
  • On the other hand, Mog1p binds to GTP-Gsp1DeltaC more efficiently than to GTP-Gsp1p [16].
  • However, overexpression of a mutant allele of NTF2 with decreased binding to Gsp1p cannot rescue the temperature sensitivity of gsp1-1 and gsp1-2 [17].
  • Yrb2p binding to Gsp1p (yeast Ran) as well as to a novel 150-kDa GTP-binding protein is also detected [18].
  • Here we report that the yeast protein Gsp1p can directly bind to the nucleoporin Nsp1p in vitro [10].

Regulatory relationships of GSP1

  • Previously, NTF2 was reported to suppress gsp1 but not PDE2 [19].
  • Furthermore, the finding that PDE2 suppressed both gsp1 and rna1-1 indicates that the Ran GTPase cycle is regulated by the Ras-cAMP pathway [19].
  • GSP1 and GSP2 were tagged with protein A and functionally expressed in a gsp1 null mutant [8].
  • Prp20p and Rna1p are GDP/GTP exchanging and GTPase-activating factors of Gsp1p, respectively, and their mutations, prp20-1 and rna1-1, can both be suppressed by Saccharomyces cerevisiae gtr1-11 [20].
  • Overexpression of MOG1 is able to suppress temperature-sensitive gsp1 mutants in yeast; Deltamog1 null mutants display temperature-sensitive defects in nuclear trafficking [21].

Other interactions of GSP1

  • Only CNR1 is essential, but both code for proteins extremely similar to Ran and can suppress mtr1 mutations in allele-specific fashion [22].
  • The gsp1 suppression occurred even in the absence of GSP2, another S. cerevisiae GSP1-like gene [19].
  • A protein required for nuclear-protein import, Mog1p, directly interacts with GTP-Gsp1p, the Saccharomyces cerevisiae ran homologue [19].
  • Using GSP1, encoding the yeast Ran, as bait, we isolated YRB2 [23].
  • It is believed that in order to complete a full GDP/GTP cycle, Gsp1p has to shuttle between the nucleus and the cytoplasm, where its GTPase Activating Protein (GAP) Rna1p is located [24].
  • Taken together, these results suggest that the GSP1 pathway could regulate proper telomeric function in yeast through Sir4p [25].

Analytical, diagnostic and therapeutic context of GSP1


  1. RNA1 encodes a GTPase-activating protein specific for Gsp1p, the Ran/TC4 homologue of Saccharomyces cerevisiae. Becker, J., Melchior, F., Gerke, V., Bischoff, F.R., Ponstingl, H., Wittinghofer, A. J. Biol. Chem. (1995) [Pubmed]
  2. Yeast heat shock mRNAs are exported through a distinct pathway defined by Rip1p. Saavedra, C.A., Hammell, C.M., Heath, C.V., Cole, C.N. Genes Dev. (1997) [Pubmed]
  3. Cex1p is a novel cytoplasmic component of the Saccharomyces cerevisiae nuclear tRNA export machinery. McGuire, A.T., Mangroo, D. EMBO J. (2007) [Pubmed]
  4. The nucleoporin Nup60p functions as a Gsp1p-GTP-sensitive tether for Nup2p at the nuclear pore complex. Denning, D., Mykytka, B., Allen, N.P., Huang, L., Al Burlingame, n.u.l.l., Rexach, M. J. Cell Biol. (2001) [Pubmed]
  5. Mtr10p functions as a nuclear import receptor for the mRNA-binding protein Npl3p. Senger, B., Simos, G., Bischoff, F.R., Podtelejnikov, A., Mann, M., Hurt, E. EMBO J. (1998) [Pubmed]
  6. Regulated nucleo/cytoplasmic exchange of HOG1 MAPK requires the importin beta homologs NMD5 and XPO1. Ferrigno, P., Posas, F., Koepp, D., Saito, H., Silver, P.A. EMBO J. (1998) [Pubmed]
  7. GSP1 and GSP2, genetic suppressors of the prp20-1 mutant in Saccharomyces cerevisiae: GTP-binding proteins involved in the maintenance of nuclear organization. Belhumeur, P., Lee, A., Tam, R., DiPaolo, T., Fortin, N., Clark, M.W. Mol. Cell. Biol. (1993) [Pubmed]
  8. Purification of protein A-tagged yeast ran reveals association with a novel karyopherin beta family member, Pdr6p. Lau, D., Künzler, M., Braunwarth, A., Hellmuth, K., Podtelejnikov, A., Mann, M., Hurt, E. J. Biol. Chem. (2000) [Pubmed]
  9. Engineered mutants in the switch II loop of Ran define the contribution made by key residues to the interaction with nuclear transport factor 2 (NTF2) and the role of this interaction in nuclear protein import. Kent, H.M., Moore, M.S., Quimby, B.B., Baker, A.M., McCoy, A.J., Murphy, G.A., Corbett, A.H., Stewart, M. J. Mol. Biol. (1999) [Pubmed]
  10. The small GTPase Gsp1p binds to the repeat domain of the nucleoporin Nsp1p. Stochaj, U., Héjazi, M., Belhumeur, P. Biochem. J. (1998) [Pubmed]
  11. Mutants in a yeast Ran binding protein are defective in nuclear transport. Schlenstedt, G., Wong, D.H., Koepp, D.M., Silver, P.A. EMBO J. (1995) [Pubmed]
  12. Yrb4p, a yeast ran-GTP-binding protein involved in import of ribosomal protein L25 into the nucleus. Schlenstedt, G., Smirnova, E., Deane, R., Solsbacher, J., Kutay, U., Görlich, D., Ponstingl, H., Bischoff, F.R. EMBO J. (1997) [Pubmed]
  13. Nuclear protein import, but not mRNA export, is defective in all Saccharomyces cerevisiae mutants that produce temperature-sensitive forms of the Ran GTPase homologue Gsp1p. Oki, M., Noguchi, E., Hayashi, N., Nishimoto, T. Mol. Gen. Genet. (1998) [Pubmed]
  14. Allele-specific suppression of a Saccharomyces cerevisiae prp20 mutation by overexpression of a nuclear serine/threonine protein kinase. Fleischmann, M., Stagljar, I., Aebi, M. Mol. Gen. Genet. (1996) [Pubmed]
  15. The GTP-bound form of the yeast Ran/TC4 homologue blocks nuclear protein import and appearance of poly(A)+ RNA in the cytoplasm. Schlenstedt, G., Saavedra, C., Loeb, J.D., Cole, C.N., Silver, P.A. Proc. Natl. Acad. Sci. U.S.A. (1995) [Pubmed]
  16. Yrb1p interaction with the gsp1p C terminus blocks Mog1p stimulation of GTP release from Gsp1p. Oki, M., Nishimoto, T. J. Biol. Chem. (2000) [Pubmed]
  17. Interaction between the small GTPase Ran/Gsp1p and Ntf2p is required for nuclear transport. Wong, D.H., Corbett, A.H., Kent, H.M., Stewart, M., Silver, P.A. Mol. Cell. Biol. (1997) [Pubmed]
  18. Yrb2p is a nuclear protein that interacts with Prp20p, a yeast Rcc1 homologue. Taura, T., Schlenstedt, G., Silver, P.A. J. Biol. Chem. (1997) [Pubmed]
  19. A protein required for nuclear-protein import, Mog1p, directly interacts with GTP-Gsp1p, the Saccharomyces cerevisiae ran homologue. Oki, M., Nishimoto, T. Proc. Natl. Acad. Sci. U.S.A. (1998) [Pubmed]
  20. Saccharomyces cerevisiae putative G protein, Gtr1p, which forms complexes with itself and a novel protein designated as Gtr2p, negatively regulates the Ran/Gsp1p G protein cycle through Gtr2p. Nakashima, N., Noguchi, E., Nishimoto, T. Genetics (1999) [Pubmed]
  21. Crystallization and preliminary X-ray diffraction analysis of the Saccharomyces cerevisiae ran-binding protein Mog1p. Baker, R.P., Stewart, M. Acta Crystallogr. D Biol. Crystallogr. (2000) [Pubmed]
  22. Regulation of RNA processing and transport by a nuclear guanine nucleotide release protein and members of the Ras superfamily. Kadowaki, T., Goldfarb, D., Spitz, L.M., Tartakoff, A.M., Ohno, M. EMBO J. (1993) [Pubmed]
  23. Yrb2p, a Nup2p-related yeast protein, has a functional overlap with Rna1p, a yeast Ran-GTPase-activating protein. Noguchi, E., Hayashi, N., Nakashima, N., Nishimoto, T. Mol. Cell. Biol. (1997) [Pubmed]
  24. Overexpression of Bud5p can suppress mutations in the Gsp1p guanine nucleotide exchange factor Prp20p in Saccharomyces cerevisiae. Clément, M., Lavallée, F., Barbès-Morin, G., de Repentigny, L., Belhumeur, P. Mol. Genet. Genomics (2001) [Pubmed]
  25. The nuclear GTPase Gsp1p can affect proper telomeric function through the Sir4 protein in Saccharomyces cerevisiae. Clément, M., Deshaies, F., de Repentigny, L., Belhumeur, P. Mol. Microbiol. (2006) [Pubmed]
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