Molecular analyses of an unusual translesion DNA polymerase from Methanosarcina acetivorans C2A.

Abstract:

The domain Archaea is composed of several subdomains, and prominent among them are the Crenarchaeota and the Euryarchaeota. Biochemically characterized archaeal family Y DNA polymerases (Pols) or DinB homologs, to date, are all from crenarchaeal organisms, especially the genus Sulfolobus. Here, we demonstrate that archaeal family Y Pols fall into five clusters based on phylogenetic analysis. MacDinB-1, the homolog from the euryarchaeon Methanosarcina acetivorans that is characterized in this study, belongs to cluster II. Therefore, MacDinB-1 is different from the Sulfolobus DinB proteins, which are members of cluster I. In addition to translesion DNA synthesis activity, MacDinB-1 synthesized unusually long products ( approximately 7.2 kb) in the presence of its cognate proliferating cell nuclear antigen (PCNA). The PCNA-interacting site in MacDinB-1 was identified by mutational analysis in a C-terminally located heptapeptide akin to a PIP (PCNA-interacting protein) box. In vitro assays from the present report suggested that MacDinB-1 works in an error-free mode to repair cyclobutane pyrimidine dimers. This study on a euryarchaeal DinB homolog provides important insights into the functional diversity of the family Y Pols, and the availability of a genetic system for this archaeon should allow subsequent elucidation of the physiological significance of this enzyme in M. acetivorans cells.

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