Mammalian translesion DNA synthesis across an acrolein-derived deoxyguanosine adduct: Participation of DNA polymerase η in error-prone synthesis in human cells

α-OH-PdG, an acrolein-derived deoxyguanosine adduct, inhibits DNA synthesis and miscodes significantly in human cells. To probe the cellular mechanism underlying the error-free and error-prone translesion DNA syntheses, in vitro primer extension experiments using purified DNA polymerases and site-specific α-OH-PdG were conducted. The results suggest the involvement of pol η in the cellular error-prone translesion synthesis. Experiments with xeroderma pigmentosum variant cells, which lack pol η, confirmed this hypothesis. The in vitro results also suggested the involvement of pol ι and/or REV1 in inserting correct dCMP opposite α-OH-PdG during error-free synthesis. However, none of translesion-specialized DNA polymerases catalyzed significant extension from a dC terminus when paired opposite α-OH-PdG. Thus, our results indicate the following. (i) Multiple DNA polymerases are involved in the bypass of α-OH-PdG in human cells. (ii) The accurate and inaccurate syntheses are catalyzed by different polymerases. (iii) A modification of the current eukaryotic bypass model is necessary to account for the accurate bypass synthesis in human cells.