Genetic damage during thymidylate starvation in Saccharomyces cerevisiae.

Thymidylate starvation in a yeast mutant auxotrophic for dTMP caused cell death and the induction of mutations in the mitochondrial genome. After 24 h of starvation almost all surviving cells were respiratory deficient petites. In addition, shorter episodes of dTMP starvation induced chloramphenicol and erythromycin resistant mutants, indicating the occurrence of mitochondrial point mutations. Suboptimal concentrations of exogenous thymidylate were also found to induce petites and a decline in cell viability and the magnitude of these effects was acutely dependent upon the dTMP concentration. Cesium chloride gradient analysis of DNA from cells undergoing thymineless incubation revealed a progressive loss of mitochondrial DNA, and a decrease in the molecular weight of nuclear DNA.