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

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 (uve1degrees) 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 (apn2degrees) strain and shown that it is mildly sensitive to H2O2. Furthermore we have also shown that apn2degrees cells have an elevated rate of spontaneous mutation that is similar to uve1degrees. The phenotype of apn2degrees uve 1degrees double mutants indicates that these genes define distinct spontaneous mutation avoidance pathways. While uve1degrees cells show only a modest sensitivity to the oxidizing agent hydrogen peroxide (H2O2), both uve1degrees and apn2degrees cells also display a marked increased in mutation rate following exposure to H2O2 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. (C) 2003 Elsevier B.V. All rights reserved.