title: Defining the roles of the N-terminal region and the helicase activity of RECQ4A in DNA repair and homologous recombination in Arabidopsis.
abstract: RecQ helicases are critical for the maintenance of genomic stability. The Arabidopsis RecQ helicase RECQ4A is the functional counterpart of human BLM, which is mutated in the genetic disorder Bloom's syndrome. RECQ4A performs critical roles in regulation of homologous recombination (HR) and DNA repair. Loss of RECQ4A leads to elevated HR frequencies and hypersensitivity to genotoxic agents. Through complementation studies, we were now able to demonstrate that the N-terminal region and the helicase activity of RECQ4A are both essential for the cellular response to replicative stress induced by methyl methanesulfonate and cisplatin. In contrast, loss of helicase activity or deletion of the N-terminus only partially complemented the mutant hyper-recombination phenotype. Furthermore, the helicase-deficient protein lacking its N-terminus did not complement the hyper-recombination phenotype at all. Therefore, RECQ4A seems to possess at least two different and independent sub-functions involved in the suppression of HR. By in vitro analysis, we showed that the helicase core was able to regress an artificial replication fork. Swapping of the terminal regions of RECQ4A with the closely related but functionally distinct helicase RECQ4B indicated that in contrast to the C-terminus, the N-terminus of RECQ4A was required for its specific functions in DNA repair and recombination.
authors.affiliation: Botanical Institute II, Karlsruhe Institute of Technology, Hertzstrasse 16, Karlsruhe 76187, Germany and Institute for Biosafety in Plant Biotechnology, Julius Kühn Institute (JKI), Erwin-Baur-Strasse 27, Quedlinburg 06484, Germany.
authors.forename: Susan
authors.initials: S
authors.lastname: Schröpfer
authors.forename: Daniela
authors.initials: D
authors.lastname: Kobbe
authors.forename: Frank
authors.initials: F
authors.lastname: Hartung
authors.forename: Alexander
authors.initials: A
authors.lastname: Knoll
authors.forename: Holger
authors.initials: H
authors.lastname: Puchta
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004265:DNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair; D059765:Homologous Recombination; D008239:Lysine / Q000235:genetics; D009154:Mutation; D010641:Phenotype; D017434:Protein Structure, Tertiary
chemical_list: D029681:Arabidopsis Proteins; D000251:Adenosine Triphosphatases; D004265:DNA Helicases; C514439:RecQ4A protein, Arabidopsis; D008239:Lysine