title: Growth site localization of Rho1 small GTP-binding protein and its involvement in bud formation in Saccharomyces cerevisiae.
abstract: The Rho small GTP-binding protein family regulates various actomyosin-dependent cell functions, such as cell morphology, locomotion, cytokinesis, membrane ruffling, and smooth muscle contraction. In the yeast Saccharomyces cerevisiae, there is a homologue of mammalian RhoA, RHO1, which is essential for vegetative growth of yeast cells. To explore the function of the RHO1 gene, we isolated a recessive temperature-sensitive mutation of RHO1, rho1-104. The rho1-104 mutation caused amino acid substitutions of Asp 72 to Asn and Cys 164 to Tyr of Rho1p. Strains bearing the rho1-104 mutation accumulated tiny- or small-budded cells in which cortical actin patches were clustered to buds at the restrictive temperature. Cell lysis and cell death were also seen with the rho1-104 mutant. Indirect immunofluorescence microscopic study demonstrated that Rho1p was concentrated to the periphery of the cells where cortical actin patches were clustered, including the site of bud emergence, the tip of the growing buds, and the mother-bud neck region of cells prior to cytokinesis. Indirect immunofluorescence study with cells overexpressing RHO1 suggested that the Rho1p-binding site was saturable. A mutant Rho1p with an amino acid substitution at the lipid modification site remained in the cytoplasm. These results suggest that Rho1 small GTP-binding protein binds to a specific site at the growth region of cells, where Rho1p exerts its function in controlling cell growth.
authors.affiliation: Department of Biochemistry, Kobe University School of Medicine, Japan.
authors.forename: W
authors.initials: W
authors.lastname: Yamochi
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
authors.forename: H
authors.initials: H
authors.lastname: Nonaka
authors.forename: A
authors.initials: A
authors.lastname: Maeda
authors.forename: T
authors.initials: T
authors.lastname: Musha
authors.forename: Y
authors.initials: Y
authors.lastname: Takai
mesh_terms: D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D002451:Cell Compartmentation; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000648:ultrastructure*; D029701:Saccharomyces cerevisiae Proteins; D013045:Species Specificity; D013329:Structure-Activity Relationship; D013696:Temperature; D020741:rho GTP-Binding Proteins
chemical_list: D000199:Actins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D019204:GTP-Binding Proteins; C051302:RHO1 protein, S cerevisiae; D020741:rho GTP-Binding Proteins