Identification and characterization of the rhp23(+) DNA repair gene in Schizosaccharomyces pombe

We have identified rhp23(+), the ortholog of the Saccharomyces cerevisiae R AD23 and human HHR23A and HHR23B genes, in Schizosaccharomyces pombe and ex amined its role in cell survival and DNA repair. In S. pombe two repair mec hanisms are operative on UV-induced photoproducts, i.e., UV damage repair ( UVDR) and nucleotide excision repair (NER). Here we show that Rhp23 is sole ly involved in NER and study its role in DNA repair in the absence of the U VDR pathway. S, pombe rhp23-deficient cells are sensitive toward UV irradia tion, although not as sensitive as complete NER-deficient cells. Furthermor e we demonstrate that the residual survival observed in rhp23-deficient cel ls is NER dependent. Despite this NER-dependent survival, uvde rhp23 double mutants are unable to repair cyclobutane pyrimidine dimers. The inability to remove these photolesions from both DNA strands clearly demonstrates tha t rhp23(+) is involved in transcription coupled repair as well as global ge nome repair. (C) 2000 Academic Press.