Enzymatic properties of the caenorhabditis elegans Dna2 endonuclease/helicase and the species-specific interaction between RPA and Dna2

Abstract

Unlike budding or fission yeasts, the null mutation of Caenorhabditis elegans dna2+ caused a delayed lethality, allowing survival of some of the mutant C. elegans adults to F2 generation. In order to understand the underlying cause of this difference in requirements of Dna2 between yeasts and metazoa, we examined enzymatic properties of recombinant C. elegans Dna2 (CeDna2) and its interaction with replication protein A (RPA) from various sources. Like budding yeast Dna2 (ScDna2), CeDna2 possessed DNA-dependent ATPase, helicase, and endonuclease activities. However, CeDna2 had higher specific activities (~10-fold and 20-fold, respectively) of ATPase and endonuclease than ScDna2. CeDna2 endonuclease efficiently degraded a short 5’ ssDNA tail (< 10 nucleotides) that was hardly cleaved by ScDna2. Both endonuclease and helicase activities of CeDna2 were stimulated by C. elegans RPA, but not by human or yeast RPA, demonstrating a species-specific interaction between Dna2 and RPA. These and other enzymatic properties of CeDna2 described in this report may shed lights on the observation that C. elegans is less stringently dependent on Dna2 for its viability than S. cerevisiae. We propose that flaps generated by polymerase δ-mediated displacement DNA synthesis are mostly short in C. elegans eukaryotes, and hence less dependent on Dna2 for viability.