Genetic control of predominantly error-free replication through an acrolein-derived minor-groove DNA adduct

Acrolein, an alpha,beta-unsaturated aldehyde, is generated in vivo as the end product of lipid peroxidation and from metabolic oxidation of polyamines, and it is a ubiquitous environmental pollutant. The reaction of acrolein with the N-2 of guanine in DNA leads to the formation of gamma-hydroxy-1-N-2-propano-2' deoxyguanosine (gamma-HOPdG), which can exist in DNA in a ring-closed or a ring-opened form. Here, we identified the translesion synthesis (TLS) DNA polymerases (Pols) that conduct replication through the permanently ring-opened reduced form of gamma-HOPdG ((r) gamma-HOPdG) and show that replication through this adduct is mediated via Rev1/Pol eta-, Pol iota/Pol kappa-, and Pol theta-dependent pathways, respectively. Based on biochemical and structural studies, we propose a role for Rev1 and Pol iota in inserting a nucleotide (nt) opposite the adduct and for Pols eta and kappa in extending synthesis from the inserted nt in the respective TLS pathway. Based on genetic analyses and biochemical studies with Pol theta, we infer a role for Pol theta at both the nt insertion and extension steps of TLS. Whereas purified Rev1 and Pol theta primarily incorporate a C opposite (r) gamma-HOPdG, Pol iota incorporates a C or a T opposite the adduct; nevertheless, TLS mediated by the Pol iota-dependent pathway as well as by other pathways occurs in a predominantly error-free manner in human cells. We discuss the implications of these observations for the mechanisms that could affect the efficiency and fidelity of TLS Pols.