Figure 17-26. The triggering of sister-chromatid separation by the APC.

Figure 17-26The triggering of sister-chromatid separation by the APC

The activation of APC by Cdc20 leads to the ubiquitylation and destruction of securin, which normally holds separase in an inactive state. The destruction of securin allows separase to cleave a subunit of the cohesin complex holding the sister chromatids together. The pulling forces of the mitotic spindle then pull the sister chromatids apart. In budding yeasts at least, cohesin cleavage by separase is facilitated by the phosphorylation of the cohesin complex adjacent to the cleavage site, just before anaphase begins. The phosphorylation is mediated by Polo kinase and provides an additional control on the timing of the metaphase-to-anaphase transition.

From: Intracellular Control of Cell-Cycle Events

Cover of Molecular Biology of the Cell
Molecular Biology of the Cell. 4th edition.
Alberts B, Johnson A, Lewis J, et al.
New York: Garland Science; 2002.
Copyright © 2002, Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter; Copyright © 1983, 1989, 1994, Bruce Alberts, Dennis Bray, Julian Lewis, Martin Raff, Keith Roberts, and James D. Watson .

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