Invited Speaker
JORGE B. SCHVARTZMAN
Interplay of DNA Supercoiling and Catenation During the Segregation of Sister Duplexes
The discrete regulation of supercoiling, catenation and knotting by DNA topoisomerases is well documented both in vivo and in vitro, but the interplay between them is still poorly understood. Here we studied DNA catenanes of bacterial plasmids arising as a result of DNA replication in Escherichia coli cells whose topoisomerase IV (TopoIV) activity was inhibited. We combined high-resolution two-dimensional agarose gel electrophoresis with numerical simulations in order to better understand the relationship between the DNA negative supercoiling generated by DNA gyrase and the interlinking that results from replication of circular DNA molecules. We showed that in those replication intermediates formed in vivo, catenation and negative supercoiling compete with each other. In interlinked molecules with high catenation numbers negative supercoiling is greatly limited. However, when interlinking decreases, as required for the segregation of newly replicated sister duplexes, their negative s