AtREV1, a Y-family DNA polymerase in Arabidopsis, has deoxynucleotidyl transferase activity in vitro.

To clarify the functions of the Arabidopsis thaliana REV1 (AtREV1) protein, we expressed it in Escherichia coli and purified it to near homogeneity. The deoxynucleotidyl transferase activity of the recombinant AtREV1 was examined in vitro using a primer extension assay. The recombinant AtREV1 transferred one or two nucleotides to the primer end. It efficiently inserted dCMP regardless of the opposite base. AtREV1 also inserted a dCMP opposite an apurinic/apyrimidinic site, which is physiologically generated or induced by various DNA-damaging agents. In contrast, AtREV1 had no insertion activities against UV-inducible DNA lesions as reported in yeast or mammalian system. Although the substrate specificity of AtREV1 was rather narrow in the presence of magnesium ion, it widened in the presence of manganese ion. These results suggest that AtREV1 serves as a deoxycytidyl transferase in plant cells.