We have analysed the removal of UV-induced cyclobutane pyrimidine dimers (CPDs) at nucleotide resolution from the MFA2 gene of wild-type Saccharomyces cerevisiae and in strains harbouring mutations in one of the yeast replication protein A (RPA) genes, RFA1. This gene codes for the 70 kDa subunit of RPA and it has previously been shown to have a role in nucleotide excision repair. Here two RFA1 mutants were examined: rfa1-M2 which is mutated in the protein interaction domain and rfa1-M4 which is mutated in the DNA-binding domain. A distinct difference in the removal of CPDs from the MFA2 sequence of these two mutants was observed. Compared to the parental strain, there was no defect in CPD removal in the rfa1-M2 mutant. Contrarily, the rfa1-M4 mutant was totally defective in the global repair of CPDs from the non-transcribed strand and the non-transcribed portions of the strand containing the transcribed sequence, yet it was able to perform reduced transcription coupled repair of the transcribed strand. These results indicate that the role of the DNA-binding domain of RPA is different for global repair versus transcription coupled nucleotide excision repair.
Copyright 1998 Academic Press.