Topological barriers of the bacterial genome (Marc Joyeux / LPT / Seminar) – 9/11, 14H.

Marc Joyeux (Université Grenoble Alpes)

Bacterial genomes are partitioned into several kilobases long chromosomal domains that are topologically independent from each other, meaning that changes of DNA superhelicity in one domain do not propagate to neighbors. Both in vivo and in vitro experiments have been performed to question the nature of the topological barriers at play, leading to several predictions on possible molecular actors.

In this talk, I will address the question of topological barriers using coarse-grained polymer models of supercoiled DNA chains, which are constrained such as to mimic the action of predicted molecular actors. More specifically, I will first discuss under which conditions DNA-bridging proteins may act as topological barriers. Then, I will address the question of the effect of topological barriers on DNA subject to both tension and torque and discuss the mechanism that allows DNA loops secured by a topological barrier to constrain a number of gyres much larger than expected from their length.