title: DDB2-independent role for p53 in the recovery from ultraviolet light-induced replication arrest.
abstract: Ultraviolet light (UV light) induces helix distorting DNA lesions that pose a block to replicative DNA polymerases. Recovery from this replication arrest is reportedly impaired in nucleotide excision repair (NER)-deficient xeroderma pigmentosum (XP) fibroblasts and primary fibroblasts lacking functional p53. These independent observations suggested that the involvement of p53 in the recovery from UV-induced replication arrest was related to its role in regulating the global genomic subpathway of NER (GG-NER). Using primary human fibroblasts, we confirm that the recovery from UV-induced replication arrest is impaired in cells lacking functional p53 and in primary XP fibroblasts derived from complementation groups A or C (XP-A and XP-C) that are defective in GG-NER. Surprisingly, DNA synthesis recovered normally in GG-NER-deficient XP complementation group E (XP-E) cells that carry mutations in the p53 regulated DNA repair gene DDB2 and are specifically defective in the repair of cyclobutane pyrimidine dimers (CPD) but not pyrimidine (6-4) pyrimidone photoproducts. Disruption of p53 in these XP-E fibroblasts prevented the recovery from UV-induced replication arrest. Therefore, the roles of p53 and GG-NER in the recovery from UV-induced replication are separable and DDB2-independent. These results further indicate that primary human fibroblasts expressing functional p53 efficiently replicate DNA containing CPD whereas p53-deficient cells do not, consistent with a role for p53 in permitting translesion synthesis of these DNA lesions.
authors.affiliation: Cancer Therapeutics Program, Ottawa Health Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Lawton J
authors.initials: LJ
authors.lastname: Stubbert
authors.forename: Jeff D
authors.initials: JD
authors.lastname: Hamill
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Spronck
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Smith
authors.forename: Cecilia
authors.initials: C
authors.lastname: Becerril
authors.forename: Bruce C
authors.initials: BC
authors.lastname: McKay
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication / Q000528:radiation effects*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D006801:Humans; D011740:Pyrimidine Dimers; D034622:RNA Interference; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum
chemical_list: C117669:DDB2 protein, human; D004268:DNA-Binding Proteins; D011740:Pyrimidine Dimers; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D004247:DNA