Releasin' Cohesin

Abstract

Cohesin attaches chromosomes to the mitotic spindle and allows separation of sister chromatids at anaphase. Phosphorylation of cohesin by a Polo-like kinase in yeast enhances cohesin degradation by separase at the onset of anaphase. However, in other eurkaryotes, the bulk of cohesin is removed from chromosomes earlier in mitosis (prophase and prometaphase) by a mechanism that is thought to be cleavage-independent. Sumara et al. show that a Xenopus Polo-like kinase, PLX1, is required for this bulk release before anaphase. Addition of recombinant purified PLX1 to PLX1-depleted Xenopus mitotic extracts rescued cohesin dissociation in vitro. Phosphorylation of cohesin by PLK1 also decreased cohesin binding to chromatin. Immunofluorescence microscopy confirmed that PLX1 stimulated cohesin dissociation from mitotic chromosomes. Transfected human HeLa cells expressing a constitutively activated form of PLK1 induced cohesin dissociation in vivo. PLK1 enhanced cleavage of cohesin by separase in vitro, suggesting that phosphorylation of cohesin by PLK1 may be part of the release mechanism. I. Sumara, E. Vorlaufer, P. T. Stukemberg, O. Kelm, N. Redemann, E. A. Nigg, J.-M. Peters, The dissociation of cohesin from chromosomes in prophase is regulated by Polo-like kinase. Mol. Cell 9 , 515-525 (2002). [Online Journal]