Abstract
Unlike the DNA of higher eucaryotes, the DNA of Saccharomyces cerevisiae (bakers' yeast) is not methylated. Introduction of the Escherichia coli dam gene into yeast cells results in methylation of the N-6 position of adenine. The UV excision repair system of yeast cells specifically responds to the methylation, suggesting that it is capable of recognizing modifications which do not lead to major helix distortion. The UV repair functions examined in this report are involved in the incision step of pyrimidine dimer repair. These observations may have relevance to the rearrangements and recombination events observed when yeast or higher eucaryotic cells are transformed or transfected with DNA grown in E. coli.