The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3b, Copenhagen 2200, Denmark.
Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Headington, Oxford OX3 0BP, UK.
Nat Commun. 2014 Dec 8;5:5563. doi: 10.1038/ncomms6563.
Improperly attached kinetochores activate the spindle assembly checkpoint (SAC) and by an unknown mechanism catalyse the binding of two checkpoint proteins, Mad2 and BubR1, to Cdc20 forming the mitotic checkpoint complex (MCC). Here, to address the functional role of Cdc20 kinetochore localization in the SAC, we delineate the molecular details of its interaction with kinetochores. We find that BubR1 recruits the bulk of Cdc20 to kinetochores through its internal Cdc20 binding domain (IC20BD). We show that preventing Cdc20 kinetochore localization by removal of the IC20BD has a limited effect on the SAC because the IC20BD is also required for efficient SAC silencing. Indeed, the IC20BD can disrupt the MCC providing a mechanism for its role in SAC silencing. We thus uncover an unexpected dual function of the second Cdc20 binding site in BubR1 in promoting both efficient SAC signalling and SAC silencing.
不正确连接的动粒会激活纺锤体检查点（SAC），并通过未知机制促进两个检查点蛋白 Mad2 和 BubR1 与 Cdc20 的结合，形成有丝分裂检查点复合物（MCC）。在这里，为了解决 Cdc20 动粒定位在 SAC 中的功能作用，我们阐明了其与动粒相互作用的分子细节。我们发现 BubR1 通过其内部 Cdc20 结合域（IC20BD）将 Cdc20 的大部分募集到动粒上。我们表明，通过去除 IC20BD 来阻止 Cdc20 动粒定位对 SAC 的影响有限，因为 IC20BD 对于有效的 SAC 沉默也是必需的。事实上，IC20BD 可以破坏 MCC，为其在 SAC 沉默中的作用提供了一种机制。因此，我们揭示了 BubR1 中的第二个 Cdc20 结合位点在促进有效 SAC 信号传递和 SAC 沉默方面的意外双重功能。
