Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany. Electronic address: https://twitter.com/@IsabelMMartin.
Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany; Max Planck Tandem Group in Computational Biophysics, University of Los Andes, Cra. 1 #18a-12, 111711 Bogotá, Colombia. Electronic address: https://twitter.com/@camiloapontelab.
J Mol Biol. 2022 Jan 15;434(1):167387. doi: 10.1016/j.jmb.2021.167387. Epub 2021 Dec 6.
The inner centromere protein, INCENP, is crucial for correct chromosome segregation during mitosis. It connects the kinase Aurora B to the inner centromere allowing this kinase to dynamically access its kinetochore targets. However, the function of its central, 440-residue long intrinsically disordered region (IDR) and its multiple phosphorylation sites is unclear. Here, we determined the conformational ensemble of INCENP's IDR, systematically varying the level of phosphorylation, using all-atom and coarse-grain molecular dynamics simulations. Our simulations show that phosphorylation expands INCENP's IDR, both locally and globally, mainly by increasing its overall net charge. The disordered region undergoes critical globule-to-coil conformational transitions and the transition temperature non-monotonically depends on the degree of phosphorylation, with a mildly phosphorylated case of neutral net charge featuring the highest collapse propensity. The IDR transitions from a multitude of globular states, accompanied by several specific internal contacts that reduce INCENP length by loop formation, to weakly interacting and highly extended coiled conformations. Phosphorylation critically shifts the population between these two regimes. It thereby influences cohesiveness and phase behavior of INCENP IDR assemblies, a feature presumably relevant for INCENP's function in the chromosomal passenger complex. Overall, we propose the disordered region of INCENP to act as a phosphorylation-regulated and length-variable component, within the previously defined "dog-leash" model, that thereby regulates how Aurora B reaches its targets for proper chromosome segregation.
着丝粒内蛋白 INCENP 对于有丝分裂过程中正确的染色体分离至关重要。它将激酶 Aurora B 连接到着丝粒内部，使该激酶能够动态地接近其动粒靶标。然而，其中央 440 个残基长的固有无序区域（IDR）及其多个磷酸化位点的功能尚不清楚。在这里，我们使用全原子和粗粒度分子动力学模拟，系统地改变磷酸化水平，确定了 INCENP 的 IDR 的构象整体。我们的模拟表明，磷酸化会扩展 INCENP 的 IDR，无论是局部还是全局，主要是通过增加其总净电荷。无规区域经历关键的球状物到线圈构象转变，并且转变温度与磷酸化程度呈非单调依赖性，带有轻度磷酸化的中性净电荷的情况具有最高的坍塌倾向。IDR 从多种球状状态转变，伴随着几个特定的内部接触，通过环形成减少 INCENP 的长度，到弱相互作用和高度扩展的卷曲构象。磷酸化会严重改变这两种状态之间的种群。因此，它会影响 INCENP IDR 组装体的内聚性和相行为，这一特征大概与 INCENP 在染色体乘客复合物中的功能相关。总体而言，我们提出 INCENP 的无序区域作为一个磷酸化调节和长度可变的组件，在以前定义的“狗皮带”模型内，从而调节 Aurora B 如何到达其目标以进行正确的染色体分离。
