Caldas Gina V, DeLuca Keith F, DeLuca Jennifer G
J Cell Biol. 2013 Dec 23;203(6):957-69. doi: 10.1083/jcb.201306054.
Aurora B kinase phosphorylates kinetochore proteins during early mitosis, increasing kinetochore–microtubule (MT) turnover and preventing premature stabilization of kinetochore–MT attachments. Phosphorylation of kinetochore proteins during late mitosis is low, promoting attachment stabilization, which is required for anaphase onset. The kinetochore protein KNL1 recruits Aurora B–counteracting phosphatases and the Aurora B–targeting factor Bub1, yet the consequences of KNL1 depletion on Aurora B phospho-regulation remain unknown. Here, we demonstrate that the KNL1 N terminus is essential for Aurora B activity at kinetochores. This region of KNL1 is also required for Bub1 kinase activity at kinetochores, suggesting that KNL1 promotes Aurora B activity through Bub1-mediated Aurora B targeting. However, ectopic targeting of Aurora B to kinetochores does not fully rescue Aurora B activity in KNL1-depleted cells, suggesting KNL1 influences Aurora B activity through an additional pathway. Our findings establish KNL1 as a requirement for Aurora B activity at kinetochores and for wild-type kinetochore–MT attachment dynamics.
在有丝分裂早期，极光激酶B（Aurora B kinase）使动粒蛋白磷酸化，增加动粒-微管（MT）的周转，并防止动粒-MT附着过早稳定。在有丝分裂后期，动粒蛋白的磷酸化水平较低，促进附着稳定，这是后期开始所必需的。动粒蛋白KNL1招募与极光激酶B相互作用的磷酸酶和靶向极光激酶B的因子Bub1，但KNL1缺失对极光激酶B磷酸化调节的影响尚不清楚。在这里，我们证明KNL1的N端对于动粒处的极光激酶B活性至关重要。KNL1的这一区域对于动粒处的Bub1激酶活性也是必需的，这表明KNL1通过Bub1介导的极光激酶B靶向作用来促进极光激酶B的活性。然而，将极光激酶B异位靶向到动粒并不能完全挽救KNL1缺失细胞中的极光激酶B活性，这表明KNL1通过另一条途径影响极光激酶B的活性。我们的研究结果表明，KNL1是动粒处极光激酶B活性以及野生型动粒-MT附着动力学所必需的。
