Fission yeast Uve1 and Apn2 function in distinct oxidative damage repair pathways in vivo

Abstract

In Schizosaccharomyces pombe, the endonuclease Uve1 functions as the first step in an alternate UV photo-product repair pathway that is distinct from nucleotide excision repair (NER). Based upon the broad substrate specificity of Uve1 in vitro, and the observation that Uve1 mutants accumulate spontaneous mutations at an elevated rate in vivo, we and others have hypothesized that this protein might have a function in a mutation avoidance pathway other than UV photo-product repair. We show here that fission yeast Uve1 also functions in oxidative damage repair in vivo. We have determined the spectrum of spontaneous mutations that arise in uve1 null ( uve1°) cells and have observed that both G→ T ( C→ A) and T→ G ( A→ C) transversions occur at an increased rate relative to wildtype cells. These mutations are indicative of unrepaired oxidative DNA damage and are very similar to the mutation spectrum observed in 8-oxoguanine glycosylase (OGG1) mutants in Saccharomyces cerevisiae. We have generated an apn2 null ( apn2°) strain and shown that it is mildly sensitive to H 2O 2. Furthermore we have also shown that apn2° cells have an elevated rate of spontaneous mutation that is similar to uve1°. The phenotype of apn2°uve1° double mutants indicates that these genes define distinct spontaneous mutation avoidance pathways. While uve1° cells show only a modest sensitivity to the oxidizing agent hydrogen peroxide (H 2O 2), both uve1° and apn2° cells also display a marked increased in mutation rate following exposure to H 2O 2 doses. Collectively these data demonstrate that Uve1 is a component of multiple alternate repair pathways in fission yeast and suggest a possible role for Uve1 in a general alternate incision repair pathway in eukaryotes.