title: Xer-mediated site-specific recombination at cer generates Holliday junctions in vivo.
abstract: Normal segregation of the Escherichia coli chromosome and stable inheritance of multicopy plasmids such as ColE1 requires the Xer site-specific recombination system. Two putative lambda integrase family recombinases, XerC and XerD, participate in the recombination reactions. We have constructed an E. coli strain in which the expression of xerC can be tightly regulated, thereby allowing the analysis of controlled recombination reactions in vivo. Xer-mediated recombination in this strain generates Holliday junction-containing DNA molecules in which a specific pair of strands has been exchanged in addition to complete recombinant products. This suggests that Xer site-specific recombination utilizes a strand exchange mechanism similar or identical to that of other members of the lambda integrase family of recombination systems. The controlled in vivo recombination reaction at cer requires recombinase and two accessory proteins, ArgR and PepA. Generation of Holliday junctions and recombinant products is equally efficient in RuvC- and RuvC+ cells, and in cells containing a multicopy RuvC+ plasmid. Controlled XerC expression is also used to analyse the efficiency of recombination between variant cer sites containing sequence alterations and heterologies within their central regions.
authors.affiliation: University of Glasgow, Institute of Genetics, UK.
authors.forename: R
authors.initials: R
authors.lastname: McCulloch
authors.forename: L W
authors.initials: LW
authors.lastname: Coggins
authors.forename: S D
authors.initials: SD
authors.lastname: Colloms
authors.forename: D J
authors.initials: DJ
authors.lastname: Sherratt
mesh_terms: D000626:Aminopeptidases / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D004254:DNA Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004706:Endodeoxyribonucleases; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D043384:Glutamyl Aminopeptidase; D019426:Integrases; D008957:Models, Genetic; D008969:Molecular Sequence Data; D045522:Recombinases; D011995:Recombination, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C087018:ArgR protein, Bacteria; C490177:ArgR protein, E coli; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D045522:Recombinases; D012097:Repressor Proteins; C473360:XerC protein, E coli; C069806:ruvC protein, E coli; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C473361:XerD protein, E coli; C115006:integron integrase IntI1; D004706:Endodeoxyribonucleases; D000626:Aminopeptidases; D043384:Glutamyl Aminopeptidase