Replication of 2-hydroxyadenine-containing DNA and recognition by human MutSα

2-Hydroxyadenine (2-OH-A), a product of DNA oxidation, is a potential source of mutations. We investigated how representative DNA polymerases from the A, B and Y families dealt with 2-OH-A in primer extension experiments. A template 2-OH-A reduced the rate of incorporation by DNA polymerase α (Pol α) and Klenow fragment (Kfexo−). Two Y family DNA polymerases, human polymerase η (Pol η) and the archeal Dpo4 polymerase were affected differently. Bypass by Pol η was very inefficient whereas Dpo4 efficiently replicated 2-OH-A. Replication of a template 2-OH-A by both enzymes was mutagenic and caused base substitutions. Dpo4 additionally introduced single base deletions. Thermodynamic analysis showed that 2-OH-A forms stable base pairs with T, C and G, and to a lesser extent with A. Oligonucleotides containing 2-OH-A base pairs, including the preferred 2-OH-A:T, were recognized by the human MutSα mismatch repair (MMR). MutSα also recognized 2-OH-A located in a repeat sequence that mimics a frameshift intermediate.