Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
J Cell Biol. 2012 Oct 15;199(2):285-301. doi: 10.1083/jcb.201203091. Epub 2012 Oct 8.
Accurate chromosome segregation during mitosis relies on a dynamic kinetochore (KT)-microtubule (MT) interface that switches from a labile to a stable condition in response to correct MT attachments. This transition is essential to satisfy the spindle-assembly checkpoint (SAC) and couple MT-generated force with chromosome movements, but the underlying regulatory mechanism remains unclear. In this study, we show that during mitosis the MT- and KT-associated protein CLASP2 is progressively and distinctively phosphorylated by Cdk1 and Plk1 kinases, concomitant with the establishment of KT-MT attachments. CLASP2 S1234 was phosphorylated by Cdk1, which primed CLASP2 for association with Plk1. Plk1 recruitment to KTs was enhanced by CLASP2 phosphorylation on S1234. This was specifically required to stabilize KT-MT attachments important for chromosome alignment and to coordinate KT and non-KT MT dynamics necessary to maintain spindle bipolarity. CLASP2 C-terminal phosphorylation by Plk1 was also required for chromosome alignment and timely satisfaction of the SAC. We propose that Cdk1 and Plk1 mediate a fine CLASP2 "phospho-switch" that temporally regulates KT-MT attachment stability.
在有丝分裂过程中，染色体的正确分离依赖于一个动态的着丝粒（KT）-微管（MT）界面，该界面能够对正确的 MT 附着做出反应，从而从不稳定状态转变为稳定状态。这种转变对于满足纺锤体组装检查点（SAC）并将 MT 产生的力与染色体运动耦联至关重要，但潜在的调节机制尚不清楚。在这项研究中，我们表明，在有丝分裂过程中，MT 和 KT 相关蛋白 CLASP2 被 Cdk1 和 Plk1 激酶逐步且明显地磷酸化，伴随着 KT-MT 附着的建立。CLASP2 S1234 被 Cdk1 磷酸化，这为 CLASP2 与 Plk1 结合做好了准备。CLASP2 S1234 的磷酸化增强了 Plk1 向 KT 的募集。这对于稳定对染色体排列很重要的 KT-MT 附着以及协调维持纺锤体双极所必需的 KT 和非 KT MT 动力学是特别必需的。Plk1 对 CLASP2 C 端的磷酸化对于染色体排列和及时满足 SAC 也是必需的。我们提出，Cdk1 和 Plk1 介导了精细的 CLASP2“磷酸开关”，该开关可在时间上调节 KT-MT 附着的稳定性。
