Characterization of synthetic-lethal mutants reveals a role for the Saccharomyces cerevisiae guanine-nucleotide exchange factor Cdc24p in vacuole function and Na+ tolerance

• Published in: Genetics (Austin) 1997-09, Vol.147 (1), p.43-55
• Main Authors: White, W.H. (University of Vermont, Burlington, VT.), Johnson, D.I
• Format: Article
• Language: English
• Subjects: ADENOSINETRIPHOSPHATASE; ATPASA; ATPASE; BINDING PROTEINS; CALCIO; CALCIUM; Calcium Chloride - pharmacology; Carboxy-Lyases - genetics; CATION; CATIONES; CATIONS; Cell Cycle Proteins - genetics; Cell Cycle Proteins - physiology; Cell Polarity - genetics; CITOLOGIA; COMPLEMENTATION; Crosses, Genetic; CYTOLOGIE; CYTOLOGY; FENOTIPOS; FUNGAL MORPHOLOGY; GENE LETAL; Genes; GENES LETALES; Genes, Fungal - physiology; Genes, Lethal - physiology; Genetic Complementation Test; GENETIC TRANSFORMATION; GENETICA; GENETICS; GENETIQUE; Guanine Nucleotide Exchange Factors; GUANOSINE DIPHOSPHATE; GUANOSINE TRIPHOSPHATE; Investigations; LETHAL GENES; Microbiology; MORFOLOGIA FUNGICA; MORPHOLOGIE DE CHAMPIGNON; MUTANT; MUTANTES; MUTANTS; Mutation - physiology; NUCLEOTIDE; NUCLEOTIDES; NUCLEOTIDOS; PHENOTYPE; PHENOTYPES; PROTEINAS AGLUTINANTES; PROTEINE DE LIAISON; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins - physiology; Proton-Translocating ATPases - genetics; SACCHAROMYCES CEREVISIAE; Saccharomyces cerevisiae - cytology; Saccharomyces cerevisiae - drug effects; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae Proteins; SODIO; SODIUM; Sodium Chloride - pharmacology; TRANSFORMACION GENETICA; TRANSFORMATION GENETIQUE; VACUOLA; Vacuolar Proton-Translocating ATPases; VACUOLE; VACUOLES; Vacuoles - physiology; Yeast
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1093/genetics/147.1.43

Cdc24p is the guanine-nucleotide exchange factor for the Cdc42p GTPase, which controls cell polarity in Saccharomyces cerevisiae. To identify new genes that may affect cell polarity, we characterized six UV-induced csl (CDC24 synthetic-lethal) mutants that exhibited synthetic-lethality with cdc24-4ls at 23 degrees. Five mutants were not complemented by plasmid-borne CDC42, RSR1, BUD5, BEM1, BEM2, BEM3 or CLA4 genes, which are known to play a role in cell polarity. The csl3 mutant displayed phenotypes similar to those observed with calcium-sensitive, Pet- vna mutants defective in vacuole function. CSL5 was allelic to VMA5, the vacuolar H(+)-ATPase subunit C, and one third of csl5 cdc24-4ls cells were elongated or had misshapen buds. A cdc24-4ls delta vma5::LEU2 double mutant did not exhibit synthetic lethality, suggesting that the csl5/vma5 cdc24-4ls synthetic-lethality was not simply due to altered vacuole function. The cdc24-4ls mutant, like delta vma5::LEU2 and csl3 mutants, was sensitive to high levels of Ca2+ as well as Na+ in the growth media, which did not appear to be a result of a fragile cell wall because the phenotypes were not remedied by 1 M sorbitol. Our results indicated that Cdc24p was required in one V-ATPase mutant and another mutant affecting vacuole morphology, and also implicated Cdc24p in Na+ tolerance.