Abstract
Translesion DNA synthesis (TLS) is one of the damage tolerant mechanisms avoiding detrimental effects of DNA damages due to exposure to several mutagens. REV1 protein is a component of error-prone TLS in yeast and mammals. Previously, we isolated and characterized AtREV1, which is an Arabidopsis homolog of the REV1 gene. The AtREV1 disrupted mutants, rev1, showed hypersensitive to UV-B and DNA cross-linkers suggesting the importance of AtREV1 to be tolerant to several DNA damaging agents.
To clarify the functions of AtREV1, we overexpressed AtREV1 in E.coli cells and obtained a functional recombinant protein. The activity of AtREV1 recombinant protein was measured by primer extension assay. The AtREV1 recombinant protein transferred one or two nucleotides to the primer end. Especially, it efficiently inserted a dCMP regardless the opposite base. The AtREV1 also inserted a dTMP or a dGMP opposite the guanine. These results indicate that the AtREV1 has a deoxynucleotidyl transferase activity.
The AtREV1 inserted a dCMP or other nucleosides opposite the apurinic/apyrimidinic (AP) sites. This result suggests that AtREV1 is involved in the bypass of AP sites that provide a damage-tolerance in plant cells. However, AtREV1 showed no insertion or extension activities against UV-inducible DNA lesions, cyclobutane pyrimidine dimer (CPD) and 6-4 photoproduct. We speculate that AtREV1 has unknown function(s) other than the transferase activity and the second function is involved in the bypass of CPDs and 6-4 photoproducts.
