Alteration of a yeast SH3 protein leads to conditional viability with defects in cytoskeletal and budding patterns.

Mutations in genes necessary for survival in stationary phase were isolated to understand the ability of wild-type Saccharomyces cerevisiae to remain viable during prolonged periods of nutritional deprivation. Here we report results concerning one of these mutants, rvs167, which shows reduced viability and abnormal cell morphology upon carbon and nitrogen starvation. The mutant exhibits the same response when cells are grown in high salt concentrations and other unfavorable growth conditions. The RVS167 gene product displays significant homology with the Rvs161 protein and contains a SH3 domain at the C-terminal end. Abnormal actin distribution is associated with the mutant phenotype. In addition, while the budding pattern of haploid strains remains axial in standard growth conditions, the budding pattern of diploid mutant strains is random. The gene RVS167 therefore could be implicated in cytoskeletal reorganization in response to environmental stresses and could act in the budding site selection mechanism.