title: Repair of UV induced DNA lesions in ribosomal gene chromatin and the role of "Odd" RNA polymerases (I and III).
abstract: In fast growing eukaryotic cells, a subset of rRNA genes are transcribed at very high rates by RNA polymerase I (RNAPI). Nuclease digestion-assays and psoralen crosslinking have shown that they are open; that is, largely devoid of nucleosomes. In the yeast Saccharomyces cerevisae, nucleotide excision repair (NER) and photolyase remove UV photoproducts faster from open rRNA genes than from closed and nucleosome-loaded inactive rRNA genes. After UV irradiation, rRNA transcription declines because RNAPI halt at UV photoproducts and are then displaced from the transcribed strand. When the DNA lesion is quickly recognized by NER, it is the sub-pathway transcription-coupled TC-NER that removes the UV photoproduct. If dislodged RNAPI are replaced by nucleosomes before NER recognizes the lesion, then it is the sub-pathway global genome GG-NER that removes the UV photoproducts from the transcribed strand. Also, GG-NER maneuvers in the non-transcribed strand of open genes and in both strands of closed rRNA genes. After repair, transcription resumes and elongating RNAPI reopen the rRNA gene. In higher eukaryotes, NER in rRNA genes is inefficient and there is no evidence for TC-NER. Moreover, TC-NER does not occur in RNA polymerase III transcribed genes of both, yeast and human fibroblast.
authors.affiliation: Département de Microbiologie et Infectiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, QC J1E 4K8, Canada.
authors.forename: Romain
authors.initials: R
authors.lastname: Charton
authors.affiliation: Département de Microbiologie et Infectiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, QC J1E 4K8, Canada.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Guintini
authors.affiliation: Département de Microbiologie et Infectiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, QC J1E 4K8, Canada.
authors.forename: François
authors.initials: F
authors.lastname: Peyresaubes
authors.affiliation: Département de Microbiologie et Infectiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, QC J1E 4K8, Canada. Electronic address: Antonio.Conconi@usherbrooke.ca.
authors.forename: Antonio
authors.initials: A
authors.lastname: Conconi
mesh_terms: D002843:Chromatin / Q000378:metabolism / Q000528:radiation effects; D004247:DNA / Q000378:metabolism / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair; D056890:Eukaryota / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D020459:Genes, rRNA / Q000528:radiation effects*; D006801:Humans; D012318:RNA Polymerase I / Q000378:metabolism*; D012319:RNA Polymerase II / Q000378:metabolism*; D014158:Transcription, Genetic; D014466:Ultraviolet Rays
chemical_list: D002843:Chromatin; D004247:DNA; D012319:RNA Polymerase II; D012318:RNA Polymerase I
keywords: Cyclobutane pyrimidine dimers; Nucleotide excision repair; RNA polymerase I; RNA polymerase III; Transcription coupled repair; rDNA chromatin