AtRECQ2, a RecQ-helicase homologue from Arabidopsis thaliana, is able to disrupt different recombinogenic DNA-structures in vitro

Abstract

RecQ helicases play an important role in the maintenance of genomic stability in pro- and eukaryotes. This is highlighted by the human genetic diseases Werner, Bloom's and Rothmund-Thomson syndrome, caused by respective mutations in three of the five human RECQ genes. The highest numbers of RECQ homologous genes are found in plants, e.g. seven in Arabidopsis thaliana. However, only limited information is available on the functions of plant RecQ helicases, and no biochemical characterization has been performed. Here, we demonstrate that AtRECQ2 is a (d)NTP-dependent 3'-->5' DNA helicase. We further characterized its basal properties and its action on various partial DNA duplexes. Importantly, we demonstrate that AtRECQ2 is able to disrupt recombinogenic structures: by disrupting various D-loop structures, AtRECQ2 may prevent non-productive recombination events on the one hand, and may channel repair processes into non-recombinogenic pathways on the other hand, thus facilitating genomic stability. We show that a synthetic partially mobile Holliday junction is processed towards splayed-arm products, possibly indicating a branch migration function for AtRECQ2. The biochemical properties defined in this work support the hypothesis that AtRECQ2 might be functionally orthologous to the helicase part of the human RecQ homologue HsWRN.