Abstract

DNA replication is the basis for biological inheritance. In bacteria, reproduction starts with replication of the chromosome into two identical daughter molecules, followed by segregation of the newly replicated chromosomes and division of the parent cell into two daughter cells. In circular chromosomes, problems of entanglement during DNA linking complicate the process of chromosome segregation. In Escherichia coli, DNA unlinking is typically mediated by the type II topoisomerase topoIV. In the absence of topo IV, the site-specific recombination system XerCD mediates sister chromosome unlinking. This reaction is activated at the division septum by a powerful translocase FtsK, which coordinates the last stages of chromosome segregation. The mechanism by which the XerCD-FtsK complex simplifies the topology of DNA remains unclear. Techniques from knot theory and low-dimensional topology, aided by computational tools, are used to study the action of such enzymes. Understanding D NA unlinking by Xer recombination will provide a more complete picture of the chromosome segregation process.

This is joint work with Kai Ishihara, David Sherratt, Koya Shimokawa and Christine Soteros.