8-Hydroxy-5,6,7,8.tetrahydropyrimido[1,2-a]purin-10(3H)-one,3-(2′ -deoxyriboside) (1,N2-γ-hydroxyprano deoxyguanosine, γ-HOPdG) is a major DNA adduct that forms as a result of exposure to acrolein, an environmental pollutant and a product of endogenous lipid peroxidation. γ-HOPdG has been shown previously not to be a miscoding lesion when replicated in Escherichia coli. In contrast to those prokaryotic studies, in vivo replication and mutagenesis assays in COS-7 cells using single stranded DNA containing a specific γ-HOPdG adduct, revealed that the y-HOPdG adduct was significantly mutagenic. Analyses revealed both transversion and transition types of mutations at an overall mutagenic frequency of 7.4 × 10-2/translesion synthesis. In vitro γ-HOPdG strongly blocks DNA synthesis by two major polymerases, pol δ and pol ε. Replicative blockage ofpol δ by γ-HOPdG could be diminished by the addition of proliferating cell nuclear antigen, leading to highly mutagenic translesion bypass across this adduct. The differential functioning and processing capacities of the mammalian polymerases may be responsible for the higher mutation frequencies observed in this study when compared with the accurate and efficient nonmutagenic bypass observed in the bacterial system.
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