Induction of petite “mutants” in an ethidium-resistant strain of Saccharomyces cerevisiae by photoaffinity labeling : Distinction between early and late steps

Abstract

A strain of Saccharomyces cerevisiae (MH41-7B/011) was resistant to petite induction by ethidium bromide at 30°, but was sensitive to induction by photolabeling with ethidium monoazide. These results suggested a defect in the mutant in metabolic activation of ethidium to account for its resistance. Synchronized cultures of both the mutant and the normal parent strains showed a substantial reduction in petite response to photolabeling in stationary phase cells which could not be accounted for by changes in cell penetration of the drug. The use of photolabeling with normal and mutant cells suggested that petite induction can be divided into early and late steps.