Genetic effects of oxidative DNA damage: comparative mutagenesis of 7,8-dihydro-8-oxoguanine and 7,8-dihydro-8-oxoadenine inEscherichia coli

Abstract

A single 7,8-dihydro-8-oxoguanine (G8-OXO; 8-hydroxyguanine) adduct in the lacZ alpha gene of bacteriophage M13 DNA induces a targeted G-->T transversion after replication in Escherichia coli (Biochemistry, 29, 7024-7031 (1990)). This mutation is thought to be due to the facile formation during DNA synthesis of a G8-OXO.base pair, where G8-OXO is in the syn conformation about the deoxyglycosyl bond. A related modified purine, 7,8-dihydro-8-oxoadenine (A8-OXO; 8-hydroxyadenine), is an abundant product found in irradiated and oxidized DNAs. Similar to G8-OXO, as a mononucleoside A8-OXO assumes the syn conformation. This work has assessed the relative mutagenicities of A8-OXO and G8-OXO in the same experimental system. A deoxypentanucleotide containing A8-OXO [d(GCT-A8-OXOG)] was synthesized. After 5'-phosphorylation with [gamma-32P] ATP, the oligomer was ligated into a duplex M13mp19-derived genome at a unique NheI restriction site. Genomes containing either A8-OXO (at position 6275, [+] strand) or G8-OXO (position 6276) were denatured with heat and introduced into E.coli DL7 cells. Analysis of phage DNA from mutant plaques obtained by plating immediately after transformation (infective centers assay) revealed that G8-OXO induced G-->T transversions at an apparent frequency of approximately 0.3%. The frequency and spectrum of mutations observed in DNA sequences derived from 172 mutant plaques arising from the A8-OXO-modified DNA were almost indistiguishable from those generated from transfection of an adenine-containing control genome. We conclude that A8-OXO is at least an order of magnitude less mutagenic than G8-OXO in E.coli cells with normal DNA repair capabilities.

Mutagenic potency ofHelicobacter pyloriin the gastric mucosa of mice is determined by sex and duration of infection

“…G:C-to-T:A transversions are also caused by adducts produced by oxidative stress or lipid peroxidation, such as 8-oxodG, εdC, and M1G (34,35). The presence of 8-oxodG, a major product of oxidative damage to DNA, results in mispairing of guanine with adenine during replication, thus inducing transversions (36). Although 8-oxodG is believed to be the main cause of this mutation, etheno adducts formed by lipid peroxidation may also play a significant role in mutagenesis observed in vivo (37).…”

Enforced Presentation of an Extrahelical Guanine to the Lesion Recognition Pocket of Human 8-Oxoguanine Glycosylase, hOGG1

“…These powerful electrophiles react with many components of the cell, but the consequences are particularly dangerous when DNA is the target, as the resulting oxidative damage fundamentally alters the covalent structure and therefore the information content of DNA, thus giving rise to mutations. The predominant nucleobase lesion arising from DNA oxidation, 8-oxoguanine (oxoG), 2 is among the most mutagenic of all known endogenous nucleobase lesions (2,3). Despite the fact that the oxoG lesion differs by only two atoms from its progenitor G (Fig.…”

Hydrogen Peroxide Induces Topoisomerase I-mediated DNA Damage and Cell Death

“…In vivo measurements estimate a high number (10 5 ) of such oxidatively modified lesions formed in a cell each day (7). Conversion of guanine to 8-oxoG causes a selective mis-incorporation of adenine opposite to 8-oxoG that can lead to G-T transversions in the DNA (8,9). In the absence of repair, this base modification has been suggested to mediate carcinogenesis (10 -12).…”