γ-Hydroxy-1,N2-propano-2′deoxyguanosine (γ-HOPdG) is a major deoxyguanosine adduct derived from acrolein, a known mutagen. In vitro, this adduct has previously been shown to pose a severe block to translesion synthesis by a number of polymerases (pol). Here we show that both yeast and human pol η can incorporate a C opposite γ-HOPdG at ∼190- and ∼100-fold lower efficiency relative to the control deoxyguanosine and extend from a C paired with the adduct at ∼8- and -19-fold lower efficiency. Although DNA synthesis past γ-HOPdG by yeast pol η was relatively accurate, the human enzyme misincorporated nucleotides opposite the lesion with frequencies of ∼10-1 to 10-2. Because γ-HOPdG can adopt both ring closed and ring opened conformations, comparative replicative bypass studies were also performed with two model adducts, propanodeoxyguanosine and reduced γ-HOPdG. For both yeast and human pol η, the ring open reduced η-HOPdG adduct was less blocking than η-HOPdG, whereas the ring closed propanodeoxyguanosine adduct was a very strong block. Replication of DNAs containing η-HOPdG in wild type and xeroderma pigmentosum variant cells revealed a somewhat decreased mutation frequency in xeroderma pigmentosum variant cells. Collectively, the data suggest that pol η might potentially contribute to both error-free and mutagenic bypass of γ-HOPdG.
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