Replication past a trans-4-hydroxynonenal minor-groove adduct by the sequential action of human DNA polymerases ι and κ

The X-ray crystal structure of human DNA polymerase iota (Pol iota) has shown that it differs from all known Pols in its dependence upon Hoogsteen base pairing for synthesizing DNA. Hoogsteen base pairing provides an elegant mechanism for synthesizing DNA opposite minor-groove adducts that present a severe block to synthesis by replicative DNA polymerases. Germane to this problem, a variety of DNA adducts form at the N-2 minor-groove position of guanine. Previously, we have shown that proficient and error-free replication through the gamma-HOPdG (gamma-hydroxy-1,N-2-propano-2'-deoxyguanosine) adduct, which is formed from the reaction of acrolein with the N-2 of guanine, is mediated by the sequential action of human PoIL and PoI kappa, in which Pol iota incorporates the nucleotide opposite the lesion site and PoI kappa carries out the subsequent extension reaction. To test the general applicability of these observations to other adducts formed at the N-2 position of guanine, here we examine the proficiency of human PoI iota and PoI kappa to synthesize past stereoisomers of trans-4-hydroxy-2-nonenal-deoxyguanosine (HNE-dG). Even though HNE- and acrolein-modified dGs share common structural features, due to their increased size and other structural differences, HNE adducts are potentially more blocking for replication than gamma-HOPdG. We show here that the sequential action of Pol iota and PoI kappa promotes efficient and error-free synthesis through the HNE-dG adducts, in which Pol iota, incorporates the nucleotide opposite the lesion site and PoI kappa performs the extension reaction.