Cover image

Two mitotic kinases, Polo-like kinase (Plx1) and aurora B, mediate cohesin dissociation from chromatin at the onset of mitosis in Xenopus. Shown here in the background are metaphase chromosomes assembled in a control Xenopus egg extract (yellow) or an extract depleted of both Plx1 and aurora B (green). The chromosomes have been stained with an antibody directed against condensin to label the axis of each chromatid. Inset are higher magnification images of well-resolved sister chromatids observed in the control extract (left, yellow) and of unresolved chromatids in the Plx1/aurora B-depleted extract (right, green). The mitotic release of cohesin is required for sister chromatid resolution. (For details, see Losada et al., p. 3004.)