Deoxycytidyl transferase activity of yeast REV1 protein

MUTAGENESIS induced by DNA damage in Saccharomyces cerevisiae requires the products of the REV1, REV3 and REV7 genes1. The Rev3 and Rev7 proteins are subunits of DNA polymerase-zeta2 (Pol-ζ), an enzyme whose sole function appears to be translesion synthesis3. Rev1 protein has weak homology with UmuC protein4, which facilitates translesion synthesis in Escherichia coli by an unknown mechanism. We show here that Revl protein has a deoxycytidyl transferase activity which transfers a dCMP residue from dCTP to the 3′ end of a DNA primer in a template-dependent reaction. Efficient transfer occurred opposite a template abasic site, but ∼20% transfer also occurred opposite a template guanine and ∼10% opposite adenine or uracil; ≤1% was seen opposite thymine or cytosine. Insertion of cytosine opposite an abasic site produced a terminus that was extended efficiently by Pol-ζ, but not by yeast Pol-α.