Yeast Rev1 Protein Is a G Template-specific DNA Polymerase*

Rev1 protein of Saccharomyces cerevisiae functions with DNA polymerase ζ in mutagenictrans-lesion synthesis. Because of the reported preferential incorporation of a C residue opposite an abasic site, Rev1 has been referred to as a deoxycytidyltransferase. Here, we use steady-state kinetics to examine nucleotide incorporation by Rev1 opposite undamaged and damaged template residues. We show that Rev1 specifically inserts a C residue opposite template G, and it is ∼25-, 40-, and 400-fold less efficient at inserting a C residue opposite an abasic site, an O⁶-methylguanine, and an 8-oxoguanine lesion, respectively. Rev1 misincorporates G, A, and T residues opposite template G with a frequency of ∼10⁻³to 10⁻⁴. Consistent with this finding, Rev1 replicates DNA containing a string of Gs in a template-specific manner, but it has a low processivity incorporating 1.6 nucleotides per DNA binding event on the average. From these observations, we infer that Rev1 is a G template-specific DNA polymerase.