DNA Polymerase ν Rapidly Bypasses O⁶-Methyl-dG but Not O⁶-[4-(3-Pyridyl)-4-oxobutyl-dG and O²-Alkyl-dTs

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent tobacco carcinogen that forms mutagenic DNA adducts including O⁶-methyl-2′-deoxyguanosine (O⁶-Me-dG), O⁶-[4-(3-pyridyl)-4-oxobut-1-yl]-dG (O⁶-POB-dG), O²-methylthymidine (O²-Me-dT), and O²-POB-dT. We evaluated the ability of human DNA polymerase ν to bypass this damage to evaluate the structural constraints on substrates for pol ν and to evaluate if there is kinetic evidence suggesting the in vivo activity of pol ν on tobacco-induced DNA damage. Presteady-state kinetic analysis has indicated that O⁶-Me-dG is a good substrate for pol ν, while O⁶-POB-dG and the O²-alkyl-dT adducts are poor substrates for pol ν. The reactivity with O⁶-Me-dG is high with a preference for dCTP > dGTP > dATP > dTTP. The catalytic activity of pol ν toward O⁶-Me-dG is high and can potentially be involved in its bypass in vivo. In contrast, pol ν is unlikely to bypass O⁶-POB-dG or the O²-alkyl-dTs in vivo.