A protein required for nuclear-protein import, Mog1p, directly interacts with GTP-Gsp1p, the Saccharomyces cerevisiae ran homologue.
We previously isolated 25 temperature-sensitive gsp1 alleles of Saccharomyces cerevisiae Ran homologue, each of which possesses amino acid changes that differ from each other. We report here isolation of three multicopy suppressors-PDE2, NTF2, and a gene designated MOG1-all of which rescued a growth defect of these gsp1 strains. The gsp1 suppression occurred even in the absence of GSP2, another S. cerevisiae GSP1-like gene. Previously, NTF2 was reported to suppress gsp1 but not PDE2. Mog1p, with a calculated molecular mass of 24 kDa, was found to be encoded by the yeast ORF YJR074W. Both MOG1 and NTF2 suppressed a series of gsp1 alleles with similar efficiency, and both suppressed gsp1 even with a single gene dose. Consistent with the high efficiency of gsp1 suppression, Mog1p directly bound to GTP, but not to GDP-Gsp1p. The disruption of MOG1 made yeast temperature-sensitive for growth. Deltamog1, which was suppressed by overexpression of NTF2, was found to have a defect in both classic and nonclassic nuclear localization signal-dependent nuclear-protein imports, but not in mRNA export. Thus, Mog1p, which was localized in the nucleus, is a Gsp1p-binding protein involved in nuclear-protein import and that functionally interacts with Ntf2p. Furthermore, the finding that PDE2 suppressed both gsp1 and rna1-1 indicates that the Ran GTPase cycle is regulated by the Ras-cAMP pathway.
Oki
M
M
Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Higashi-ku, Fukuoka 812-8582, Japan.
Nishimoto
T
T
D000595:Amino Acid Sequence; D005656:Fungal Proteins / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005800:Genes, Fungal; D016153:Genes, Suppressor; D015698:Genomic Library; D005838:Genotype; D008969:Molecular Sequence Data; D008970:Molecular Weight; D020559:Monomeric GTP-Binding Proteins; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D016366:Open Reading Frames; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins
D005656:Fungal Proteins; C080324:GSP1 protein, S cerevisiae; D009687:Nuclear Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D019204:GTP-Binding Proteins; D020559:Monomeric GTP-Binding Proteins