Functional analysis of DNA polymerase zeta and REV1 protein in Arabidopsis

Sakamoto, Ayako; Nakagawa, Mayu; Takahashi, Shinya*; Tanaka, Atsushi

Translesion synthesis (TLS) is one of the cellular processes to overcome the lethal effect of unrepaired DNA damage. During screening for genes accounting for the UV-resistance in Arabidopsis, we first identified AtREV3 that encodes a catalytic subunit of DNA polymerase zeta (Pol z). Pol z is thought to bypass damaged DNA in an error-prone manner. We subsequently identified AtREV7, a regulatory subunit of Pol z, and AtREV1 that is thought to cooperate with Pol z in bypassing of apurine/apyrimidine (AP) sites. Disruption of any of AtREV3, AtREV7, or AtREV1 made the plants more sensitive to UVB than the wild type, suggesting that these REV proteins are required for plants to tolerate to the UV-induced damage. We further analyzed the UV-induced mutation frequency in rev3 and rev1. We found that the disruption of AtREV3 or AtREV1 reduced the mutation frequency to 1/4 of the level of the wild type. These results are consistent with an idea of that the Pol z and AtREV1 are involved in the UV-induced mutation in Arabidopsis. However, by using the bacterially expressed protein, although we detected AtREV1 inserted a dCMP at the opposite of the AP site in vitro, AtREV1 failed to bypass UV-induced damage as reported in other organisms. Thus, the mechanism by which the REV1 functions remains to be clarified.