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

We have identified rhp23(+), the ortholog of the Saccharomyces cerevisiae RAD23 and human HHR23A and HHR23B genes, in Schizosaccharomyces pombe and examined its role in cell survival and DNA repair. In S. pombe two repair mechanisms are operative on UV-induced photoproducts, i.e., UV damage repair (UVDR) and nucleotide excision repair (NER). Here we show that Rhp23 is solely involved in NER and study its role in DNA repair in the absence of the UVDR pathway. S. pombe rhp23-deficient cells are sensitive toward UV irradiation, although not as sensitive as complete NER-deficient cells. Furthermore we demonstrate that the residual survival observed in rhp23-deficient cells 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 that rhp23(+) is involved in transcription coupled repair as well as global genome repair.