Sci. Signal., 30 October 2012
Cell Cycle Mastering Early Divisions
Stella M. Hurtley
Science, AAAS, Cambridge CB2 1LQ, UK
The regulation of canonical mitotic cell cycles is well understood, but the basic principles of the rapid, synchronized early mitotic divisions in embryos remain a mystery. Early embryos lack key mitotic regulators, such as checkpoints, the anaphase-promoting complex/cyclosome (APC/C)–inhibitory protein Emi1, and the inhibitory phosphorylations of cyclin-dependent kinase 1 (Cdk1). Working in Xenopus embryos, Tischer et al. identified XErp1 (also known as Emi2) as a mitotic APC/C-inhibitor essential for early mitotic divisions. The mitotic APC/C-inhibitory activity of XErp1 is positively regulated by protein kinase A (PKA) and protein phosphatase IIA (PP2A), which antagonizes Cdk1s inhibitory effect on XErp1. Thus, Cdk1 and PP2A/PKA appear to act antagonistically to control XErp1 activity, which results in the oscillatory activation and inactivation of the APC/C required for fast and synchronous mitotic divisions.
Citation: S. M. Hurtley, Mastering Early Divisions. Sci. Signal. 5, ec283 (2012).
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