title: HO* radicals induce an unexpected high proportion of tandem base lesions refractory to repair by DNA glycosylases.
abstract: Reaction of HO(*) radicals with double-stranded calf thymus DNA produces high levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) and, to a minor extent, 8-oxo-7,8-dihydro-2'-deoxyadenosine (8-oxodAdo). Formation of the hydroxylated purine lesions is explained by addition of HO(*) to the C8 position of the purine moiety. It has been reported that tandem lesions containing a formylamine residue neighboring 8-oxodGuo could be produced through addition of a transiently generated pyrimidine peroxyl radical onto the C8 of an adjacent purine base. Formation of such tandem lesions accounted for approximately 10% of the total 8-oxodGuo. In the present work we show that addition of HO(*) onto the C8 of purine accounts for only approximately 5% of the generated 8-oxodGuo. About 50% of the 8-hydroxylated purine lesions, including 8-oxodGuo and 8-oxodAdo, are involved in tandem damage and are produced by peroxyl addition onto the C8 of a vicinal purine base. In addition, the remaining 45% of the 8-oxodGuo are produced by an electron transfer reaction, providing an explanation for the higher yield of formation of 8-oxodGuo compared to 8-oxodAdo. Interestingly, we show that >40% of the 8-oxodGuo involved in tandem lesions is refractory to excision by DNA glycosylases. Altogether our results demonstrate that, subsequently to a single oxidation event, peroxidation reactions significantly increase the yield of formation of hydroxylated purine modifications, generating a high proportion of tandem lesions partly refractory to base excision repair.
authors.affiliation: Commissariat à l'Energie Atomique, Institut Nanosciences et Cryogénie, Lésions des Acides Nucléiques, F-38054 Grenoble Cedex 9, France.
authors.forename: François
authors.initials: F
authors.lastname: Bergeron
authors.forename: Frédéric
authors.initials: F
authors.lastname: Auvré
authors.forename: J Pablo
authors.initials: JP
authors.lastname: Radicella
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Ravanat
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D002417:Cattle; D004247:DNA / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D004249:DNA Damage; D045647:DNA Glycosylases / Q000378:metabolism*; D004260:DNA Repair / Q000502:physiology*; D003839:Deoxyadenosines / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D005720:Gamma Rays; D017665:Hydroxyl Radical / Q000378:metabolism / Q000494:pharmacology*; D066298:In Vitro Techniques; D008954:Models, Biological; D010084:Oxidation-Reduction
chemical_list: D003839:Deoxyadenosines; D017665:Hydroxyl Radical; C078251:2'-deoxy-7,8-dihydro-8-oxoadenosine; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA; D045647:DNA Glycosylases; D003849:Deoxyguanosine