Repair of damaged and mismatched DNA by the XPC homologues Rhp41 and Rhp42 of fission yeast

Rhp41 and Rhp42 of Schizosaccharomyces pombe are homologues of human XPC, which is involved in nucleotide excision repair (NER) of damaged DNA. Inactivation of rhp41 caused moderate sensitivity to ultraviolet (UV) radiation. In addition, an increase of mitotic mutation rates was observed in the rhp41 mutant, which was dependent on active translesion polymerase Z. UV sensitivity and mutation rates were not different between rhp42 and wild type, but compared to rhp41 were further increased in rhp41 rhp42 cells. Transcription of the fbp1 gene (induced in vegetative cells) and of the SPBC1289.14 gene (induced during meiosis) was strongly blocked by UV-induced damages in the rhp41 mutant, but not, or only slightly, reduced in rhp42 background. NER-dependent short-patch repair of mismatches formed during meiosis was slightly affected in rhp41, moderately affected in rhp42, and absent in rhp41 rhp42. Epistasis analysis with rhp7 and rhp26 indicates that Rhp41 and Rhp42 are both involved in the global genome and transcription-coupled repair subpathways of NER. Rhp41 plays a major role in damage repair and Rhp42 in mismatch repair.