Nucleic acid metabolism in yeast II. Metabolism of thymidylate during thymidylate excess death.

A discrete class of strains of Saccharomyces cerevisiae, able to utilize, highly efficiently, exogenous deoxythymidine-5'-monophosphate (dTMP),was found to be sensitive to concentrations greater than 10 Micro M dTMP in an otherwise complete growth medium. Excess dTMP is cytostatic and cytotoxic: 90% of exponentially growing cells lose colony forming ability within 1 h of exposure to excess dTMP is a growth medium. Uptake of dTMP, adenine, histidine, and leucine does occur during this thymidylate excess death (TED). dTMP is anabolized to higher phosphorylated synthesis is blocked under TED-conditions but not RNA and protein biosynthesis.