title: Conditional lethality of a yeast strain expressing human RHOA in place of RHO1.
abstract: The yeast RHO1 GTPase, which has 72% amino acid sequence identity with its human counterpart, RHOA, is essential for growth, although the reason has not been investigated. We report here that yeast strains that rely solely on expression of human RHOA in place of RHO1 are able to grow at 23 degrees C but grow neither at 37 degrees C nor in the presence of 300 mM CaCl2 even at 23 degrees C. Measurements of steady-state protein levels indicate that inability to grow at the restrictive temperature is not due to instability of the protein. Homolog scanning with the two GTPases identified a small, 27-residue region of RHO1 which, when substituted into RHOA, confers full function in yeast. This region corresponds to the alpha 3-helix loop 7 region of RAS; the same region was reported to determine specificity of function between GTPases of the RAB family, Sec4p and Ypt1p. By examining the phenotype of RHOA substitution strains at nonpermissive temperature, we found evidence suggesting that the normal function of RHO1 is to maintain osmotic integrity.
authors.affiliation: Department of Plant Sciences, Graduate School of Science, University of Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Qadota
authors.forename: Y
authors.initials: Y
authors.lastname: Anraku
authors.forename: D
authors.initials: D
authors.lastname: Botstein
authors.forename: Y
authors.initials: Y
authors.lastname: Ohya
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000595:Amino Acid Sequence; D016384:Consensus Sequence; D005656:Fungal Proteins / Q000096:biosynthesis* / Q000235:genetics; D019204:GTP-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D005804:Genes, Lethal; D005816:Genetic Complementation Test; D005838:Genotype; D006801:Humans; D008969:Molecular Sequence Data; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein
chemical_list: D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D000246:Adenosine Diphosphate Ribose; D019204:GTP-Binding Proteins; C051302:RHO1 protein, S cerevisiae; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein