A dominant interfering mutation in RAS1 of Saccharomyces cerevisiae.

A mutant allele of RAS1 that dominantly interferes with the wild-type Ras function in the yeast Saccharomyces cerevisiae was discovered during screening of mutants that suppress an ira2 disruption mutation. A single amino acid substitution, serine for glycine at position 22, was found to cause the mutant phenotype. The inhibitory effect of the RAS1Ser22 gene could be overcome either by overexpression of CDC25 or by the ira2 disruption mutation. These results suggest that the RAS1Ser22 gene product interferes with the normal interaction of Ras with Cdc25 by forming a dead-end complex between Ras1Ser22 and Cdc25 proteins.