Rad23 Is Required for Transcription-Coupled Repair and Efficient Overall Repair in Saccharomyces cerevisiae

The repair of UV-induced photoproducts (cyclobutane pyrimidine dimers) in a well-characterized minichromosome, genomic DNA, and a transcribed genomic gene (RPB2) of a rad23Δ mutant of Saccharomyces cerevisiae was examined. Isogenic wild-type cells show a strong bias for the repair of the transcribed strands in both the plasmid and genomic genes and efficient overall repair of both DNAs (>80% of the dimers were removed in 6 h). However, the rad23Δ mutant shows (i) no strand bias for repair in these genes and decreased repair of both strands, (ii) partial repair of genomic DNA (~45% in 6 h), and (iii) very poor repair of the plasmid overall (~15% in 6 h). These features, coupled with the decreased UV survival of rad23Δ cells, indicate that Rad23 is required for both transcription-coupled repair and efficient overall repair in S. cerevisiae.