Cohesin resolves to let go

Achromosomal glue needs to get out of the way so that sister chromatids can resolve into two distinct entities, say Ana Losada, Michiko Hirano, and Tatsuya Hirano (Cold Spring Harbor Laboratory, Cold Spring Harbor, NY).Cohesin sticks sister chromatids together from the moment of their replication. During interphase this may aid in homology-based DNA repair. But when it is time to compact chromosomes in mitosis, all that glue could confuse matters. Up to 95% of the cohesin disperses, with the rest remaining in place until chromosome pairs finally split during anaphase.

Hirano and his colleagues found that two kinases—polo-like kinase (Plx1) and aurora B—were necessary for the initial dispersal. Plx1 probably operates via its direct phosphorylation of cohesin, whereas aurora B seems to hit another target such as histone H3.

Cohesin was no longer lost from chromosomes when...