title: Delocalization of nucleolar poly(ADP-ribose) polymerase-1 to the nucleoplasm and its novel link to cellular sensitivity to DNA damage.
abstract: Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme activated by binding to DNA breaks, which causes PARP-1 automodification. PARP-1 activation is required for regulating various cellular processes, including DNA repair and cell death induction. PARP-1 involved in these regulations is localized in the nucleoplasm, but approximately 40% of PARP-1 can be found in the nucleolus. Previously, we have reported that nucleolar PARP-1 is delocalized to the nucleoplasm in cells exposed to DNA-damaging agents. However, the functional roles of this delocalization in cellular response to DNA damage is not well understood, since this approach simultaneously induces the delocalization of PARP-1 and its automodification. We therefore devised an approach for separating these processes. Unmodified PARP-1 was first delocalized from the nucleolus using camptothecin. Then, PARP-1 was activated by exposure of cells to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). In contrast to treatment with MNNG alone, delocalization of PARP-1 by CPT, prior to its activation by MNNG, induced extensive automodification of PARP-1. DNA repair activity and consumption of intracellular NAD(+) were not affected by this activation. On the other hand, activation led to an increased formation of apoptotic cells, and this effect was suppressed by inhibition of PARP-1 activity. These results suggest that delocalization of PARP-1 from the nucleolus to the nucleoplasm sensitizes cells to DNA damage-induced apoptosis. As it has been suggested that the nucleolus has a role in stress sensing, nucleolar PARP-1 could participate in a process involved in nucleolus-mediated stress sensing.
authors.affiliation: Department of Anatomy and Physiology, Division of Health and Environmental Research, Faculty of Medicine, Laval University Medical Centre (CHUQ), Laval University, Quebec, Canada.
authors.forename: Ann
authors.initials: A
authors.lastname: Rancourt
authors.forename: Masahiko S
authors.initials: MS
authors.lastname: Satoh
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D002166:Camptothecin / Q000494:pharmacology; D002467:Cell Nucleus / Q000201:enzymology*; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology; D009243:NAD / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D059004:Topoisomerase I Inhibitors; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D051033:Apoptosis Inducing Factor; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D059004:Topoisomerase I Inhibitors; D009243:NAD; D008769:Methylnitronitrosoguanidine; D000246:Adenosine Diphosphate Ribose; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin