title: Mechanism of RecA-mediated homologous recombination revisited by single molecule nanomanipulation.
abstract: The mechanisms of RecA-mediated three-strand homologous recombination are investigated at the single-molecule level, using magnetic tweezers. Probing the mechanical response of DNA molecules and nucleoprotein filaments in tension and in torsion allows a monitoring of the progression of the exchange in real time, both from the point of view of the RecA-bound single-stranded DNA and from that of the naked double-stranded DNA (dsDNA). We show that strand exchange is able to generate torsion even along a molecule with freely rotating ends. RecA readily depolymerizes during the reaction, a process presenting numerous advantages for the cell's 'protein economy' and for the management of topological constraints. Invasion of an untwisted dsDNA by a nucleoprotein filament leads to an exchanged duplex that remains topologically linked to the exchanged single strand, suggesting multiple initiations of strand exchange on the same molecule. Overall, our results seem to support several important assumptions of the monomer redistribution model.
authors.affiliation: Laboratoire Physico-Chimie Curie, Institut Curie, UMR CNRS 168, Paris, France.
authors.forename: Renaud
authors.initials: R
authors.lastname: Fulconis
authors.forename: Judith
authors.initials: J
authors.lastname: Mine
authors.forename: Aurélien
authors.initials: A
authors.lastname: Bancaud
authors.forename: Marie
authors.initials: M
authors.lastname: Dutreix
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Viovy
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D005821:Genetic Techniques; D007700:Kinetics; D046911:Macromolecular Substances; D008280:Magnetics; D036103:Nanotechnology; D009690:Nucleic Acid Conformation; D011938:Rec A Recombinases / Q000737:chemistry / Q000378:metabolism*; D011995:Recombination, Genetic
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D046911:Macromolecular Substances; D011938:Rec A Recombinases