title: Replicative resolution of integron cassette insertion.
abstract: Site-specific recombination catalyzed by tyrosine recombinases follows a common pathway consisting of two consecutive strand exchanges. The first strand exchange generates a Holliday junction (HJ), which is resolved by a second strand exchange. In integrons, attC sites recombine as folded single-stranded substrates. Only one of the two attC site strands, the bottom one, is efficiently bound and cleaved by the integrase during the insertion of gene cassettes at the double-stranded attI site. Due to the asymmetry of this complex, a second strand exchange on the attC bottom strand (bs) would form linearized abortive recombination products. We had proposed that HJ resolution would rely on an uncharacterized mechanism, probably replication. Using an attC site carried on a plasmid with each strand specifically tagged, we followed the destiny of each strand after recombination. We demonstrated that only one strand, the one carrying the attC bs, is exchanged. Furthermore, we show that the recombination products contain the attC site bs and its entire de novo synthesized complementary strand. Therefore, we demonstrate the replicative resolution of single-strand recombination in integrons and rule out the involvement of a second strand exchange of any kind in the attC×attI reaction.
authors: Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS UMR3525, Paris 75724, France.
authors: Céline
authors: C
authors: Loot
authors: Magaly
authors: M
authors: Ducos-Galand
authors: José Antonio
authors: JA
authors: Escudero
authors: Marie
authors: M
authors: Bouvier
authors: Didier
authors: D
authors: Mazel
mesh_terms: D001287:Attachment Sites, Microbiological; D001426:Bacterial Proteins / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism; D004261:DNA Replication; D045566:DNA, Cruciform / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism; D032023:Integrons; D011995:Recombination, Genetic
chemical_list: D001426:Bacterial Proteins; D045566:DNA, Cruciform; D029968:Escherichia coli Proteins; C061260:RuvB protein, Bacteria; C069806:ruvC protein, E coli; C071446:RecG protein, E coli; D004706:Endodeoxyribonucleases; C071059:Holliday junction DNA helicase, E coli; D004265:DNA Helicases