Relationship between the induction of mitotic gene conversion and the formation of thymine glycols in yeast S. cerevisiae treated with hydrogen peroxide.

The effects of hydrogen peroxide on yeast Saccharomyces cerevisiae were assessed by measuring gene conversion at the trp 5 locus and the amount of thymine glycols in DNA using a monoclonal antibody specific to this base modification. Our results show that: (a) hydrogen peroxide-induced mitotic gene conversion in yeast strain D7M1 was dose-dependent in the low dose range where no toxicity was observed; (b) in the low dose range, the frequency of gene conversion depended on the temperature of the treatment, with more conversion at 25 degrees C than at 15 degrees C; (c) thymine glycols were induced in DNA in a dose-dependent manner following exposure of cells to up to 400 mM hydrogen peroxide; (d) there was little difference in the amount of thymine glycols formed in DNA when treatment occurred at either 25 degrees C or 15 degrees C.