title: Unlinking chromosome catenanes in vivo by site-specific recombination.
abstract: A challenge for chromosome segregation in all domains of life is the formation of catenated progeny chromosomes, which arise during replication as a consequence of the interwound strands of the DNA double helix. Topoisomerases play a key role in DNA unlinking both during and at the completion of replication. Here we report that chromosome unlinking can instead be accomplished by multiple rounds of site-specific recombination. We show that step-wise, site-specific recombination by XerCD-dif or Cre-loxP can unlink bacterial chromosomes in vivo, in reactions that require KOPS-guided DNA translocation by FtsK. Furthermore, we show that overexpression of a cytoplasmic FtsK derivative is sufficient to allow chromosome unlinking by XerCD-dif recombination when either subunit of TopoIV is inactivated. We conclude that FtsK acts in vivo to simplify chromosomal topology as Xer recombination interconverts monomeric and dimeric chromosomes.
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Grainge
authors.forename: Migena
authors.initials: M
authors.lastname: Bregu
authors.forename: Mariel
authors.initials: M
authors.lastname: Vazquez
authors.forename: Viknesh
authors.initials: V
authors.lastname: Sivanathan
authors.forename: Stephen C Y
authors.initials: SC
authors.lastname: Ip
authors.forename: David J
authors.initials: DJ
authors.lastname: Sherratt
mesh_terms: D002876:Chromosomes, Bacterial / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication / Q000502:physiology*; D027101:DNA Topoisomerase IV / Q000235:genetics / Q000378:metabolism*; D043864:DNA, Catenated / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D019426:Integrases / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic / Q000502:physiology*