title: Rom1p and Rom2p are GDP/GTP exchange proteins (GEPs) for the Rho1p small GTP binding protein in Saccharomyces cerevisiae.
abstract: The RHO1 gene encodes a homolog of the mammalian RhoA small GTP binding protein in the yeast Saccharomyces cerevisiae. Rho1p is localized at the growth site and is required for bud formation. Multicopy suppressors of a temperature-sensitive, dominant negative mutant allele of RHO1, RHO1(G22S, D125N), were isolated and named ROM (RHO1 multicopy suppressor). Rom1p and Rom2p were found to contain a DH (Dbl homologous) domain and a PH (pleckstrin homologous) domain, both of which are conserved among the GDP/GTP exchange proteins (GEPs) for the Rho family small GTP binding proteins. Disruption of ROM2 resulted in a temperature-sensitive growth phenotype, whereas disruption of both ROM1 and ROM2 resulted in lethality. The phenotypes of deltarom1deltarom2 cells were similar to those of deltarho1 cells, including growth arrest with a small bud and cell lysis. Moreover, the temperature-sensitive growth phenotype of deltarom2 was suppressed by overexpression of RHO1 or RHO2, but not of CDC42. The glutathione-S-transferase (GST) fusion protein containing the DH domain of Rom2p showed the lipid-modified Rholp-specific GDP/GTP exchange activity which was sensitive to Rho GDP dissociation inhibitor. These results indicate that Rom1p and Rom2p are GEPs that activate Rho1p in S.cerevisiae.
authors.affiliation: Department of Molecular Biology and Biochemistry, Osaka University Medical School, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ozaki
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
authors.forename: H
authors.initials: H
authors.lastname: Imamura
authors.forename: T
authors.initials: T
authors.lastname: Hihara
authors.forename: T
authors.initials: T
authors.lastname: Kameyama
authors.forename: H
authors.initials: H
authors.lastname: Nonaka
authors.forename: H
authors.initials: H
authors.lastname: Hirano
authors.forename: Y
authors.initials: Y
authors.lastname: Matsuura
authors.forename: Y
authors.initials: Y
authors.lastname: Takai
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D017931:DNA Primers; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016153:Genes, Suppressor; D020662:Guanine Nucleotide Exchange Factors; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D011506:Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D020741:rho GTP-Binding Proteins
chemical_list: D017931:DNA Primers; D020662:Guanine Nucleotide Exchange Factors; D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; D019204:GTP-Binding Proteins; C051302:RHO1 protein, S cerevisiae; D020741:rho GTP-Binding Proteins