Translesion DNA Synthesis Catalyzed by Human Pol η and Pol κ across 1,N⁶-Ethenodeoxyadenosine

1,N⁶-Ethenodeoxyadenosine, a DNA adduct generated by exogenous and endogenous sources, severely blocks DNA synthesis and induces miscoding events in human cells. To probe the mechanism for in vivo translesion DNA synthesis across this adduct, in vitro primer extension studies were conducted using newly identified human DNA polymerases (pol) η and κ, which have been shown to catalyze translesion DNA synthesis past several DNA lesions. Steady-state kinetic analyses and analysis of translesion products have revealed that the synthesis is > 100-fold more efficient with pol η than with pol κ and that both error-free and error-prone syntheses are observed with these enzymes. The miscoding events include both base substitution and frameshift mutations. These results suggest that both polymerases, particularly pol η, may contribute to the translesion DNA synthesis events observed for 1,N⁶-ethenodeoxyadenosine in human cells.