(A) Primer-template sequences showing undamaged template, top, and template containing an abasic site (denoted by _), bottom. Primers were labeled at the 5’ end during synthesis with 6-FAM (denoted by *). (B) Polymerase assays on undamaged primer-template DNA containing (a) 160 nM, (b) 40 nM, or (c) 10 nM protein with 40 nM DNA and 1 mM each dATP, dCTP, dGTP and dTTP. Reactions were incubated at 60°C for 5 min. (C) Polymerase assays on primer-template DNA containing abasic site in the template strand immediately adjacent to the terminal basepair. Protein and substrate concentrations were the same as in B. Reactions were incubated at 60°C for 10 min. (D) The undamaged primer-template DNA shown in A was used as the substrate in reactions that separately contained 1mM dCTP (lanes C), dGTP (lanes G), dATP (lanes A), or dTTP (lanes T) with 1µM enzyme, and 40nM primer-template DNA. Reactions were incubated at 37°C for 5 min. See Figure S2 for quantitation.