title: PARP inhibition versus PARP-1 silencing: different outcomes in terms of single-strand break repair and radiation susceptibility.
abstract: The consequences of PARP-1 disruption or inhibition on DNA single-strand break repair (SSBR) and radio-induced lethality were determined in synchronized, isogenic HeLa cells stably silenced or not for poly(ADP-ribose) polymerase-1 (PARP-1) (PARP-1(KD)) or XRCC1 (XRCC1(KD)). PARP-1 inhibition prevented XRCC1-YFP recruitment at sites of 405 nm laser micro irradiation, slowed SSBR 10-fold and triggered the accumulation of large persistent foci of GFP-PARP-1 and GFP-PCNA at photo damaged sites. These aggregates are presumed to hinder the recruitment of other effectors of the base excision repair (BER) pathway. PARP-1 silencing also prevented XRCC1-YFP recruitment but did not lengthen the lifetime of GFP-PCNA foci. Moreover, PARP-1(KD) and XRCC1(KD) cells in S phase completed SSBR as rapidly as controls, while SSBR was delayed in G1. Taken together, the data demonstrate that a PARP-1- and XRCC1-independent SSBR pathway operates when the short patch repair branch of the BER is deficient. Long patch repair is the likely mechanism, as GFP-PCNA recruitment at photo-damaged sites was normal in PARP-1(KD) cells. PARP-1 silencing elicited hyper-radiosensitivity, while radiosensitization by a PARP inhibitor reportedly occurs only in those cells treated in S phase. PARP-1 inhibition and deletion thus have different outcomes in terms of SSBR and radiosensitivity.
authors.affiliation: Institut Curie, Centre de Recherche Inserm, U612, Institut Curie, Bât. 110-112, Centre Universitaire, F-91405 Orsay, France.
authors.forename: Camille
authors.initials: C
authors.lastname: Godon
authors.forename: Fabrice P
authors.initials: FP
authors.lastname: Cordelières
authors.forename: Denis
authors.initials: D
authors.lastname: Biard
authors.forename: Nicole
authors.initials: N
authors.lastname: Giocanti
authors.forename: Frédérique
authors.initials: F
authors.lastname: Mégnin-Chanet
authors.forename: Janet
authors.initials: J
authors.lastname: Hall
authors.forename: Vincent
authors.initials: V
authors.lastname: Favaudon
mesh_terms: D015057:1-Naphthylamine / Q000031:analogs & derivatives / Q000494:pharmacology; D004247:DNA / Q000528:radiation effects; D053904:DNA Breaks, Single-Stranded; D004260:DNA Repair / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016193:G1 Phase; D005720:Gamma Rays; D006367:HeLa Cells; D006801:Humans; D007834:Lasers; D053644:Naphthalimides / Q000494:pharmacology; D000071137:Poly (ADP-Ribose) Polymerase-1; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D015363:Quinolones / Q000494:pharmacology; D034622:RNA Interference; D011836:Radiation Tolerance; D016196:S Phase; D000076105:X-ray Repair Cross Complementing Protein 1
chemical_list: D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D053644:Naphthalimides; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D018809:Proliferating Cell Nuclear Antigen; D015363:Quinolones; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; C086538:4-amino-1,8-naphthalimide; D004247:DNA; D015057:1-Naphthylamine; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases