title: Cdc42-dependent localization of polarisome component Spa2 to the incipient bud site is independent of the GDP/GTP exchange factor Cdc24.
abstract: Cdc42, a member of the Rho subfamily of small GTPases, is highly conserved in both sequence and function across eukaryotic species. In budding yeast, Cdc42 triggers polarized growth necessary for bud emergence via rearrangement of the actin cytoskeleton. It has been shown that the role of Cdc42 in bud emergence requires both Cdc28-Cln (G1) kinase and the passage through START. In this report, we show that Cdc42 also serves an essential function in the establishment of bud site prior to START by catalyzing the translocation of bud-site components such as Spa2 to the cell cortex. Our analysis of various conditional alleles of CDC42 suggests that these two functions (bud site establishment and bud emergence) are genetically separable. Surprisingly, the role of Cdc42 in the cortical localization of Spa2 appears to be independent of its well known GTP/GDP exchange factor Cdc24. We also provide evidence that this role of Cdc42 requires the function of the COPI coatomer complex.
authors.affiliation: Institute of Molecular and Cell Biology, Proteos, Republic of Singapore.
authors.forename: Padmashree C G
authors.initials: PC
authors.lastname: Rida
authors.forename: Uttam
authors.initials: U
authors.lastname: Surana
mesh_terms: D000483:Alleles; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000737:chemistry; D016764:Cell Polarity; D020755:Coat Protein Complex I / Q000502:physiology; D003598:Cytoskeletal Proteins; D003599:Cytoskeleton / Q000502:physiology; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013696:Temperature; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology*
chemical_list: C073594:CDC24 protein, S cerevisiae; D018797:Cell Cycle Proteins; D020755:Coat Protein Complex I; D003598:Cytoskeletal Proteins; D020662:Guanine Nucleotide Exchange Factors; C065889:SPA2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae