Mutagenic spectrum resulting from DNA damage by oxygen radicals

Abstract

Oxygen free radicals are highly reactive species that damage DNA and cause mutations. We determined the mutagenic spectrum of oxygen free radicals produced by the aerobic incubation of single-stranded M13mp2 DNA with Fe2+. The Fe2(+)-treated DNA was transfected into component Escherichia coli, and mutants within the nonessential lac Z alpha gene for beta-galactosidase were identified by decreased alpha-complementation. The frequency of mutants obtained with 10 microM Fe2+ was 20- to 80-fold greater than that obtained with untreated DNA. Mutagenesis was greater after the host cells were exposed to UV irradiation to induce the SOS "error-prone" response. The ability of catalase, mannitol, and superoxide dismutase to diminish mutagenesis indicates the involvement of oxygen free radicals. The sequence data on 94 of the mutants establish that mutagenesis results primarily from an increase in single-base substitutions. Ninety-four percent of the mutants with detectable changes in nucleotide sequence were single-base substitutions, the most frequent being G----C transversions, followed by C----T transitions and G----T transversions. The clustering of mutations at distinct gene positions suggests that Fe2+/oxygen damage to DNA is nonrandom. This mutational spectrum provides evidence that a multiplicity of DNA lesions produced by oxygen free radicals in vitro are promutagenic and could be a source of spontaneous mutations.

Mutations of the p53 gene in canine lymphoma and evidence for germ line p53 mutations in the dog

“…Anthracycline drugs, such as epirubicin, exhibit strong redox cycling properties within the cell and can generate a signi®cant amount of DNA-damaging hydroxyl radicals (Kappus, 1986;Cervantes et al, 1988;Keizer et al, 1990;Turner III et al, 1990;Doroshow, 1996). The mutations observed at GC base pairs within the p53 genes of both patients 2 and 3 would be consistent with a mechanism involving radical ion attack of guanine or cytosine DNA base residues (Muindi et al, 1985;McBride et al, 1991;Akman et al, 1992). Long term exposure to epirubicin could select for canine lymphoma cells containing therapy-induced p53 gene mutations and displaying a chemoresistant phenotype.…”

Identification and Characterization of a Novel Human DNA Glycosylase for Repair of Cytosine-derived Lesions

“…In contrast, the mammalian bypass DNA polymerase Pol preferentially incorporates T and to a lesser extent G opposite 5-OHU (19). The T⅐5-OHU pair would result in GC 3 TA transversion as frequently observed in vivo (22). In contrast, only the correct nucleotide G is inserted opposite 5-OHC (19).…”

Differential expression of Hsp27 in normal oesophagus, Barrett’s metaplasia and oesophageal adenocarcinomas

“…Elevated mucosal ROS concentrations have been demonstrated by chemiluminescence in mucosal biopsy specimens from patients with macroscopic oesophagitis and from patients with BarrettÕs metaplasia with or without oesophagitis (Olayee et al, 1995). Free radicals injure cell membranes and are mutagenic (Hinder and Stein, 1991;McBride et al, 1991). Huot et al (1996) demonstrated that overexpression of Hsp27 provides protection against actin disruption and cell death by oxyradicals.…”