Sister chromatids separate during anaphase in a three-stage program as directed by interaxis bridges

Abstract

Significance A central feature of mitosis is segregation of sister chromatids to opposite poles during anaphase. Our recent work revealed that sister chromatids are linked by robust structural bridges built on topological sister/sister catenations. This unexpected finding implies that separation of sister chromatids is more complex than previously thought. The present study reveals that bridges are removed in a highly programmed three-stage process, all licensed by anaphase onset and cohesin removal, and all promoted by distinct types of intersister separation forces. Removal of bridge-associated cohesin and topoisomerase II–mediated decatenation plays a central role. These findings raise the possibility that the presence and programmed removal of bridges are required for smooth, synchronous, and regular movement of sisters to opposite poles.