Effects of 8-halo-7-deaza-2'-deoxyguanosine triphosphate on DNA synthesis by DNA polymerases and cell proliferation.

8-OxodG (8-oxo-2'-deoxyguanosine) is representative of nucleoside damage and shows a genotoxicity. To significantly reveal the contributions of 7-NH and C8-oxygen to the mutagenic effect of 8-oxodG by DNA polymerases, we evaluated the effects of the 8-halo-7-deaza-dG (8-halogenated 7-deaza-2'-deoxyguanosine) derivatives by DNA polymerases. 8-Halo-7-deaza-dGTPs were poorly incorporated by both KF(exo(-)) and human DNA polymerase β opposite dC or dA into the template DNA. Furthermore, it was found that KF(exo(-)) was very sensitive to the introduction of the C8-halogen, while polymerase β can accommodate the C8-halogen resulting in an efficient dCTP insertion opposite the 8-halo-7-deaza-dG in the template DNA. These results indicate that strong hydrogen bonding between 7-NH in the 8-oxo-G nucleobase and 1-N in the adenine at the active site of the DNA polymerase is required for the mutagenic effects. Whereas, I-deaza-dGTP shows an antiproliferative effect for the HeLa cells, suggesting that it could become a candidate as a new antitumor agent.