Rad26, the yeast homolog of the cockayne syndrome B gene product, counteracts inhibition of DNA repair due to RNA polymerase II transcription.
Transcription-coupled DNA repair (TCR) is responsible for the preferential removal of DNA lesions from the transcribed strands of RNA polymerase II transcribed genes. Saccharomyces cerevisiae rad26 mutants and cells from patients suffering from the hereditary disease Cockayne syndrome display a TCR defective phenotype. Whether this lack of preferential repair has to be explained by a defect in repair or in general transcription is unclear at present. To discriminate between both possibilities, we analyzed repair of UV-induced cyclobutane pyrimidine dimers at single base resolution in yeast cells lacking RAD26, the homolog of the Cockayne syndrome B gene. Disrupting RAD26 affects nucleotide excision repair of transcribed DNA irrespective of the chromatin context, resulting in similar rates of removal for individual cyclobutane pyrimidine dimers throughout the transcribed strand. Notably, repair of transcribed sequences in between core nucleosomal regions is less efficient compared with nontranscribed DNA at these positions, pointing to a nucleotide excision repair impediment caused by blocked RNA polymerase. Our in vivo data demonstrate that the TCR defect in rad26 mutant cells is not due to a general transcription deficiency but results from the inability to release the transcription complex trapped at sites of base damage.
Tijsterman
M
M
Medical Genetic Centre, Department of Molecular Genetics, Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P. O. Box 9502, 2300 RA Leiden, The Netherlands.
Brouwer
J
J
D018797:Cell Cycle Proteins; D004249:DNA Damage; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair / Q000235:genetics; D045643:DNA Repair Enzymes; D004271:DNA, Fungal / Q000528:radiation effects; D019281:Dimerization; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D000075223:Poly-ADP-Ribose Binding Proteins; D012319:RNA Polymerase II / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins; D014158:Transcription, Genetic; D014466:Ultraviolet Rays
D018797:Cell Cycle Proteins; D004271:DNA, Fungal; D005656:Fungal Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; D029702:Schizosaccharomyces pombe Proteins; C088086:rad26 protein, S pombe; D012319:RNA Polymerase II; D004265:DNA Helicases; C078673:ERCC6 protein, human; D045643:DNA Repair Enzymes