FtsK-dependent XerCD-dif recombination unlinks replication catenanes in a stepwise manner.
In Escherichia coli, complete unlinking of newly replicated sister chromosomes is required to ensure their proper segregation at cell division. Whereas replication links are removed primarily by topoisomerase IV, XerC/XerD-dif site-specific recombination can mediate sister chromosome unlinking in Topoisomerase IV-deficient cells. This reaction is activated at the division septum by the DNA translocase FtsK, which coordinates the last stages of chromosome segregation with cell division. It has been proposed that, after being activated by FtsK, XerC/XerD-dif recombination removes DNA links in a stepwise manner. Here, we provide a mathematically rigorous characterization of this topological mechanism of DNA unlinking. We show that stepwise unlinking is the only possible pathway that strictly reduces the complexity of the substrates at each step. Finally, we propose a topological mechanism for this unlinking reaction.
Department of Mathematics, Saitama University, Saitama 380-8570, Japan.
Koya
K
Shimokawa
Kai
K
Ishihara
Ian
I
Grainge
David J
DJ
Sherratt
Mariel
M
Vazquez
D020090:Chromosome Segregation / Q000235:genetics / Q000502:physiology*; D002876:Chromosomes, Bacterial / Q000235:genetics*; D043864:DNA, Catenated / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000378:metabolism; D019426:Integrases / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D011995:Recombination, Genetic / Q000502:physiology*
D043864:DNA, Catenated; D029968:Escherichia coli Proteins; C096452:FtsK protein, E coli; D008565:Membrane Proteins; C473360:XerC protein, E coli; D019426:Integrases; C473361:XerD protein, E coli
DNA topology; Xer recombination; band surgery; tangle method; topology simplification