title: PARP-1 and Ku compete for repair of DNA double strand breaks by distinct NHEJ pathways.
abstract: Poly(ADP-ribose)polymerase 1 (PARP-1) recognizes DNA strand interruptions in vivo and triggers its own modification as well as that of other proteins by the sequential addition of ADP-ribose to form polymers. This modification causes a release of PARP-1 from DNA ends and initiates a variety of responses including DNA repair. While PARP-1 has been firmly implicated in base excision and single strand break repair, its role in the repair of DNA double strand breaks (DSBs) remains unclear. Here, we show that PARP-1, probably together with DNA ligase III, operates in an alternative pathway of non-homologous end joining (NHEJ) that functions as backup to the classical pathway of NHEJ that utilizes DNA-PKcs, Ku, DNA ligase IV, XRCC4, XLF/Cernunnos and Artemis. PARP-1 binds to DNA ends in direct competition with Ku. However, in irradiated cells the higher affinity of Ku for DSBs and an excessive number of other forms of competing DNA lesions limit its contribution to DSB repair. When essential components of the classical pathway of NHEJ are absent, PARP-1 is recruited for DSB repair, particularly in the absence of Ku and non-DSB lesions. This form of DSB repair is sensitive to PARP-1 inhibitors. The results define the function of PARP-1 in DSB repair and characterize a candidate pathway responsible for joining errors causing genomic instability and cancer.
authors.affiliation: University of Duisburg-Essen, Medical School, Institute of Medical Radiation Biology, Hufeland street 55, 45122 Essen, Germany.
authors.forename: Minli
authors.initials: M
authors.lastname: Wang
authors.forename: Weizhong
authors.initials: W
authors.lastname: Wu
authors.forename: Wenqi
authors.initials: W
authors.lastname: Wu
authors.forename: Bustanur
authors.initials: B
authors.lastname: Rosidi
authors.forename: Lihua
authors.initials: L
authors.lastname: Zhang
authors.forename: Huichen
authors.initials: H
authors.lastname: Wang
authors.forename: George
authors.initials: G
authors.lastname: Iliakis
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism*; D001549:Benzamides / Q000494:pharmacology; D001667:Binding, Competitive; D002460:Cell Line; D006224:Cricetinae; D004247:DNA / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000235:genetics; D004260:DNA Repair / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D000072200:Ku Autoantigen; D051379:Mice; D018345:Mice, Knockout; D000071137:Poly (ADP-Ribose) Polymerase-1; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism* / Q000502:physiology; D017434:Protein Structure, Tertiary
chemical_list: D034961:Antigens, Nuclear; D001549:Benzamides; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C000607893:LIG4 protein, human; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; C025160:3-aminobenzamide; D004247:DNA; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen; D011088:DNA Ligases; D000072481:DNA Ligase ATP