[摘要]：3-(2'-Deoxy-beta-D-erythro-pentofuranosyl)pyrimido-[1,2-alpha]purin-10(3H)-one (M(1)dG) is the major adduct derived from the reaction of DNA with the lipid peroxidation product malondialdehyde and the DNA peroxidation product base propenal. M(1)dG is mutagenic in Escherichia coli and mammalian cells, inducing base-pair substitutions (M(1)dG -> A and M(1)dG -> T) and frameshift mutations. Y-family polymerases may contribute to the mutations induced by M(1)dG in vivo. Previous reports described the bypass of M(1)dG by DNA polymerases eta and Dpo4. The present experiments were conducted to evaluate bypass of M(1)dG by the human Y-family DNA polymerases kappa, iota, and Rev1. M(1)dG was incorporated into template-primers containing either dC or dT residues 5' to the adduct, and the template-primers were subjected to in vitro replication by the individual DNA polymerases. Steady-state kinetic analysis of single nucleotide incorporation indicates that dCMP is most frequently inserted by hPol kappa opposite the adduct in both sequence contexts, followed by dTMP and dGMP. dCMP and dTMP were most frequently inserted by hPol iota, and only dCMP was inserted by Rev1. hPol kappa extended template-primers in the order M(1)dG:dC > M(1)dG:dG > M(1)dG:dT similar to M(1)dG:dA, but neither hPol iota nor Rev 1 extended M(1)dG-containing template-primers. Liquid chromatography-mass spectrometry analysis of the products of hPol kappa-catalyzed extension verified this preference in the 3'-GXC-5' template sequence but revealed the generation of a series of complex products in which dAMP is incorporated opposite M(1)dG in the 3'-GXT-5' template sequence. The results indicate that DNA hPol kappa or the combined action of hPol iota or Rev I and hPol kappa bypass M(1)dG residues in DNA and generate products that are consistent with some of the mutations induced by M(1)dG in mammalian cells.
