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BIRS Workshop Lecture Videos

Lattice knots and links in tubes Shimokawa, Koya


In Escherichia coli, complete unlinking of newly replicated sister chromosomes is required to ensure their proper segregation at cell division. While replication links are removed primarily by topoisomerase IV (TopoIV), XerCD-dif site-specific recombination can mediate sister chromosome unlinking in TopoIV-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, XerCD-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. This is a joint work with: Kai Ishihara, Ian Grainge, David J. Sherratt, and Mariel V azquez.

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