Genetic analysis of Saccharomyces cerevisiae SY 15 relaxed mutant.

Evidence is presented showing that the relaxed phenotype of the SY15 mutant is determined by one nuclear recessive mutation. The most characteristic patterns of the relaxed phenotype in yeast - rRNA accumulation and rRNA processing in the absence of protein synthesis were found to segregate together in first and second generation crosses. Therefore, the interruption of rRNA processing that occurs after starvation for a required amino acid is a pleiotropic manifestation of the stringent control itself. It is suggested that the locus for the stringent response in Saccharomyces cerevisiae (designated STR) coordinates the synthesis of rRNA on transcriptional and post-transcriptional levels.