Discovering how Topoisomerase II and Cohesin collaborate to establish sister chromatid cohesion

Sister-DNAs produced during replication are entrapped within cohesin rings till anaphase, when the proteolytic cleavage of cohesin results in sister-DNA disjunction. This phenomenon called Sister Chromatid Cohesion (cohesion) is essential for orderly segregation of chromosomes. The mechanisms that control how cohesion is generated remain enigmatic. I have discovered that Topoisomerase II (TopoII) has an unexpectedly central role in cohesion establishment. This has important implications for the mechanism of cohesion establishment. I will build on this exciting new finding to systematically dissect the role of TopoII in generation of cohesion, focussing on how TopoII promotes DNA entrapment within cohesin rings and how cohesion is established by cohesin and TopoII. I will develop in vivo and in vitro single molecule assays to directly measure entrapment of sister-DNAs within cohesin rings and address the role of TopoII in promoting this. I will ask if cohesin and TopoII need to directly interact for cohesion. I will address the possibility that cohesion is built by complex topological structures arising from a collaboration between cohesin and TopoII. This work will deliver unprecedented insights into the mechanism of cohesion establishment and will bridge the gap in our understanding of a fundamental process that underpins orderly chromosome segregation.