Differential repair of UV damage inSaccharomyces cerevisiae

Abstract
Preferential repair of UV-induced damage is a phenomenon by which mammalian cells might enhance their survival. This paper presents the first evidence that preferential repair occurs in the lower eukaryote Saccharomyces cerevisiae. Moreover an unique approach is reported to compare identical sequences present on the same chromosome and only differing in expression. We determined the removal of pyrimidine dimers from two identical .alpha.-mating type loci and we were able to show that the active MAT.alpha. locus is repaired preferentially to the inactive HML.alpha. locus. In a sir-3 mutant, in which both loci are active this preference is not observed.