title: Hyperactivation of PARP triggers nonhomologous end-joining in repair-deficient mouse fibroblasts.
abstract: Regulation of poly(ADP-ribose) (PAR) synthesis and turnover is critical to determining cell fate after genotoxic stress. Hyperactivation of PAR synthesis by poly(ADP-ribose) polymerase-1 (PARP-1) occurs when cells deficient in DNA repair are exposed to genotoxic agents; however, the function of this hyperactivation has not been adequately explained. Here, we examine PAR synthesis in mouse fibroblasts deficient in the base excision repair enzyme DNA polymerase β (pol β). The extent and duration of PARP-1 activation was measured after exposure to either the DNA alkylating agent, methyl methanesulfonate (MMS), or to low energy laser-induced DNA damage. There was strong DNA damage-induced hyperactivation of PARP-1 in pol β nullcells, but not in wild-type cells. In the case of MMS treatment, PAR synthesis did not lead to cell death in the pol β null cells, but instead resulted in increased PARylation of the nonhomologous end-joining (NHEJ) protein Ku70 and increased association of Ku70 with PARP-1. Inhibition of the NHEJ factor DNA-PK, under conditions of MMS-induced PARP-1 hyperactivation, enhanced necrotic cell death. These data suggest that PARP-1 hyperactivation is a protective mechanism triggering the classical-NHEJ DNA repair pathway when the primary alkylated base damage repair pathway is compromised.
authors.affiliation: Laboratory of Structural Biology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States of America.
authors.forename: Natalie R
authors.initials: NR
authors.lastname: Gassman
authors.forename: Donna F
authors.initials: DF
authors.lastname: Stefanick
authors.forename: Padmini S
authors.initials: PS
authors.lastname: Kedar
authors.forename: Julie K
authors.initials: JK
authors.lastname: Horton
authors.forename: Samuel H
authors.initials: SH
authors.lastname: Wilson
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000378:metabolism; D004249:DNA Damage; D059766:DNA End-Joining Repair; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase / Q000037:antagonists & inhibitors; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D000072200:Ku Autoantigen; D007834:Lasers; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D051379:Mice; D009336:Necrosis; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors; D000071137:Poly (ADP-Ribose) Polymerase-1; D011064:Poly Adenosine Diphosphate Ribose / Q000096:biosynthesis; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism / Q000502:physiology*
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011064:Poly Adenosine Diphosphate Ribose; D008741:Methyl Methanesulfonate; C499321:Parp1 protein, mouse; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D051747:DNA-Activated Protein Kinase; C497264:Prkdc protein, mouse; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen