title: Mechanism of site-selective DNA nicking by the hydrodioxyl (perhydroxyl) radical.
abstract: In previous studies, the ability of the hydrodioxyl (perhydroxyl) radical [HOO., the conjugate acid of superoxide (O2.-] to "nick" DNA under biomimetic conditions was demonstrated, and a sequence selectivity was observed. A background level of nonspecific nicking also was noted. This paper provides support for 5'-hydrogen atom abstraction from the deoxyribose ring as the initial event in the sequence-selective nicking by 02.-/HOO.. Two experiments support the proposed mechanism. First, using a defined sequence 5'-32P-labeled restriction fragment as the DNA substrate, only free (unalkylated) 3'-phosphate is produced at the site of nicking. Second, using poly (dA).poly (T) as the substrate, furfural is formed in the reaction from deoxyribose ring breakdown. Both results are consistent with 5'-hydrogen atom abstraction for initiation of the site-selective nicking. Hydrogen atom abstraction at other sites of the deoxyribose ring and/or base oxidation and loss followed by strand scission likely are responsible for the nonspecific nicking. The 5'-abstraction mechanism contrasts to those elicited by other 02-derived and metal-associated oxidants, which may provide a biomarker for the reactivity of HOO. in vivo.
authors.affiliation: Department of Pharmaceutical Sciences, Medical University of South Carolina, Charleston 29425-2303, USA.
authors.forename: T A
authors.initials: TA
authors.lastname: Dix
authors.forename: K M
authors.initials: KM
authors.lastname: Hess
authors.forename: M A
authors.initials: MA
authors.lastname: Medina
authors.forename: R W
authors.initials: RW
authors.lastname: Sullivan
authors.forename: S L
authors.initials: SL
authors.lastname: Tilly
authors.forename: T L
authors.initials: TL
authors.lastname: Webb
mesh_terms: D001665:Binding Sites; D004247:DNA / Q000737:chemistry / Q000187:drug effects*; D004249:DNA Damage; D005609:Free Radicals / Q000737:chemistry / Q000633:toxicity; D008956:Models, Chemical; D015335:Molecular Probes; D010545:Peroxides / Q000737:chemistry / Q000633:toxicity*; D010957:Plasmids / Q000737:chemistry / Q000187:drug effects; D011067:Poly dA-dT / Q000737:chemistry
chemical_list: D005609:Free Radicals; D015335:Molecular Probes; D010545:Peroxides; D011067:Poly dA-dT; C049375:perhydroxyl radical; D004247:DNA