Complementary activities of TPX2 and chTOG constitute an efficient importin-regulated microtubule nucleation module.
Complementary activities of TPX2 and chTOG constitute an efficient importin-regulated microtubule nucleation module.
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DOI：
10.1038/ncb3241
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发表时间：
2015-11
影响因子：
21.3
通讯作者：
Surrey T
中科院分区：
文献类型：
--
作者：
Roostalu J;Cade NI;Surrey T
纺锤体的装配和功能需要对微管成核和动力学进行精确的控制。染色质驱动的纺锤体组装途径在染色体附近局部实施这种控制。该途径的关键靶点之一是TPX2。TPX2如何刺激微管成核的分子机制尚不清楚。对纯化的蛋白质进行基于显微镜的动态体外重建分析，我们发现人TPX2直接稳定生长的微管末端，并通过稳定早期微管成核中间产物来刺激微管成核。人微管聚合酶chTOG(XMAP215/MSPs/Stu2p/Dis1/Alp14同源物)只能微弱地促进核形成，但与TPX2有协同作用。因此，不同和互补的活性组合足以在体外有效地形成微管。Importins通过选择性地阻断TPX2‘S与微管成核中间体的相互作用来控制微管成核的效率。这种体外重组揭示了通过最小成核模块调节微管形成的分子机制，这是细胞中染色质依赖的微管成核所必需的。
Spindle assembly and function require precise control of microtubule nucleation and dynamics. The chromatin-driven spindle assembly pathway exerts such control locally in the vicinity of chromosomes. One of the key targets of this pathway is TPX2. The molecular mechanism of how TPX2 stimulates microtubule nucleation is not understood. Using microscopy-based dynamic in vitro reconstitution assays with purified proteins, we find that human TPX2 directly stabilises growing microtubule ends and stimulates microtubule nucleation by stabilising early microtubule nucleation intermediates. Human microtubule polymerase chTOG (XMAP215/Msps/Stu2p/Dis1/Alp14 homolog) only weakly promotes nucleation, but acts synergistically with TPX2. Hence, a combination of distinct and complementary activities is sufficient for efficient microtubule formation in vitro. Importins control the efficiency of the microtubule nucleation by selectively blocking TPX2’s interaction with microtubule nucleation intermediates. This in vitro reconstitution reveals the molecular mechanism of regulated microtubule formation by a minimal nucleation module essential for chromatin-dependent microtubule nucleation in cells.