title: Activation of PARP-1 in response to bleomycin depends on the Ku antigen and protein phosphatase 5.
abstract: Poly (ADP-ribose) polymerase-1 (PARP-1) has an important role in the cellular response to a broad spectrum of DNA lesions. PARP-1 is strongly activated in response to double-stranded DNA breaks (DSBs), yet its contribution to the DSB response is poorly understood. Here we used bleomycin, a radiomimetic that generates DSBs with high specificity to focus on the response of PARP-1 to DSBs. We report that the induction of PARP-1 activity by bleomycin depends on the Ku antigen, a nonhomologous-DNA-End-Joining factor and protein phosphatase 5 (PP5). PARP-1 activation in response to bleomycin was reduced over 10-fold in Ku-deficient cells, whereas its activation in response to U.V. was unaffected. PARP-1 activation was rescued by reexpression of Ku, but was refractory to manipulation of DNA-dependent protein kinase or ATM. Similarly, PARP-1 activation subsequent to bleomycin was reduced 2-fold on ablation of PP5 and was increased 5-fold when PP5 was overexpressed. PP5 seemed to act directly on PARP-1, as its basal phosphorylation was reduced on overexpression of PP5, and PP5 dephosphorylated PARP-1 in vitro. These results highlight the functional importance of Ku antigen and PP5 for PARP-1 activity subsequent to DSBs.
authors.affiliation: Ottawa Health Research Institute, Ottawa, Ontario, Canada.
authors.forename: F
authors.initials: F
authors.lastname: Dong
authors.forename: S
authors.initials: S
authors.lastname: Soubeyrand
authors.forename: R J G
authors.initials: RJ
authors.lastname: Haché
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000378:metabolism*; D001761:Bleomycin / Q000494:pharmacology*; D053903:DNA Breaks, Double-Stranded; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D005786:Gene Expression Regulation; D020868:Gene Silencing; D006801:Humans; D000072200:Ku Autoantigen; D051379:Mice; D009687:Nuclear Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D001761:Bleomycin; D011064:Poly Adenosine Diphosphate Ribose; D011065:Poly(ADP-ribose) Polymerases; D010749:Phosphoprotein Phosphatases; C089641:protein phosphatase 5; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen