title: Ionizing radiations in Caenorhabditis elegans induce poly(ADP-ribosyl)ation, a conserved DNA-damage response essential for survival.
abstract: Poly(ADP-ribosyl)ation is one of the first responses to DNA damage in mammals. Although it is involved in base excision repair, its exact role has not been ascertained yet. Poly(ADP-ribose) polymerase-1 (PARP-1) and PARP-2 mediate most of the poly(ADP-ribosyl)ation response in mammals and are well conserved in evolution. Their respective homologues PME-1 and PME-2 are found in the nematode Caenorhabditis elegans, a well-known genetically tractable model currently used in DNA damage response research. Here we report the functional analysis of PME-1 and PME-2 in presence of DNA damage. Worms irradiated with high doses of ionizing radiations displayed a sharp drop in their NAD(+) content immediately after treatment, and a biphasic increase in poly(ADP-ribose). The physiological importance of the poly(ADP-ribosyl)ation response was highlighted when worms were preincubated with mammalian PARP inhibitors (3AB, DHQ, PJ34) and irradiated. The embryonic survival rate of the progeny was significantly decreased in a dose-dependent manner. The inhibitor 3AB had a weak effect on embryonic survival, followed closely by DHQ. However, PJ34, a member of the phenantridinone family, was very effective even when used at low concentration (100nM). In vitro PARP assay using recombinant PME-1 and PME-2 showed a similar pattern of inhibition where 3AB and DHQ were weak inhibitors, and PJ34 a stronger one. Inhibitors affect mostly the poly(ADP-ribose) polymers elongation at high concentrations. These results suggest that poly(ADP-ribosyl)ation in response to DNA damage is an ancient and very important biochemical process protecting DNA from deleterious modification.
authors.affiliation: Pediatrics Research Unit, CHUQ-CHUL Research Centre, Department of Pediatrics, Laval University, Sainte-Foy, Que., Canada.
authors.forename: Florence
authors.initials: F
authors.lastname: Dequen
authors.forename: Steve N
authors.initials: SN
authors.lastname: Gagnon
authors.forename: Serge
authors.initials: S
authors.lastname: Desnoyers
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000201:enzymology* / Q000528:radiation effects; D004249:DNA Damage; D009243:NAD / Q000378:metabolism; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000528:radiation effects*; D011839:Radiation, Ionizing; D038501:Tankyrases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D009243:NAD; D011064:Poly Adenosine Diphosphate Ribose; C504211:PME-1 protein, C elegans; C504212:PME-2 protein, C elegans; D038501:Tankyrases