A microtubule polymerase cooperates with the kinesin-6 motor and a microtubule cross-linker to promote bipolar spindle assembly in the absence of kinesin-5 and kinesin-14 in fission yeast.
A microtubule polymerase cooperates with the kinesin-6 motor and a microtubule cross-linker to promote bipolar spindle assembly in the absence of kinesin-5 and kinesin-14 in fission yeast.
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DOI：
10.1091/mbc.e17-08-0497
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发表时间：
2017-12-01
影响因子：
3.3
通讯作者：
Toda T
中科院分区：
文献类型：
--
作者：
Yukawa M;Kawakami T;Okazaki M;Kume K;Tang NH;Toda T
双极主轴组装需要Kinesin-5；然而，在缺乏驱动蛋白-5和-14的情况下，细胞可以形成纺锤体。在裂殖酵母中，三种不同的途径补偿了它们的损失。微管聚合酶、驱动蛋白-6 和微管交联剂在不同的有丝分裂阶段代替两种驱动蛋白协同发挥各自的作用。准确的染色体分离依赖于双极有丝分裂纺锤体。在许多真核生物中，纺锤体的形成是由正端定向运动驱动蛋白 5 驱动的，它产生向外的力以建立纺锤体双极性。它的抑制导致出现有丝分裂停滞的单极纺锤体。有趣的是，同时失活负端定向的运动驱动蛋白 14 可恢复许多系统中的纺锤体双极性。在这里，我们表明，在裂殖酵母中，在缺乏驱动蛋白-5/Cut7 和驱动蛋白-14/Pkl1 的情况下，三个独立的途径有助于纺锤体双极性。一种是驱动蛋白-6/Klp9，一旦短双极纺锤体组装起来，它就会与纺锤体伸长结合。 Klp9 还确保后期纺锤体的内侧定位，以防止不均匀的染色体分离。另一个是 Alp7/TACC-Alp14/TOG 微管聚合酶复合物。温度敏感的 alp7cut7pkl1 突变体被单极或非常短的纺锤体捕获。 Alp14 强制靶向纺锤体极体足以使 alp7cut7pkl1 三重缺失细胞存活并促进纺锤体组装，表明 Alp14 介导的来自纺锤体极体核面的微管聚合可以在早期有丝分裂期间产生向外的力代替 Cut7。第三条途径涉及 Ase1/PRC1 微管交联剂，可稳定反平行微管。因此，我们的研究揭示了导致有丝分裂双极纺锤体组装的驱动蛋白依赖和独立途径之间的多方面相互作用。
Kinesin-5 is required for bipolar spindle assembly; yet in the absence of kinesins-5 and -14, cells can form spindles. In fission yeast, three distinct pathways compensate for their loss. Microtubule polymerase, kinesin-6, and microtubule cross-linker execute individual roles in concert at different mitotic stages in place of the two kinesins. Accurate chromosome segregation relies on the bipolar mitotic spindle. In many eukaryotes, spindle formation is driven by the plus-end–directed motor kinesin-5 that generates outward force to establish spindle bipolarity. Its inhibition leads to the emergence of monopolar spindles with mitotic arrest. Intriguingly, simultaneous inactivation of the minus-end–directed motor kinesin-14 restores spindle bipolarity in many systems. Here we show that in fission yeast, three independent pathways contribute to spindle bipolarity in the absence of kinesin-5/Cut7 and kinesin-14/Pkl1. One is kinesin-6/Klp9 that engages with spindle elongation once short bipolar spindles assemble. Klp9 also ensures the medial positioning of anaphase spindles to prevent unequal chromosome segregation. Another is the Alp7/TACC-Alp14/TOG microtubule polymerase complex. Temperature-sensitive alp7cut7pkl1 mutants are arrested with either monopolar or very short spindles. Forced targeting of Alp14 to the spindle pole body is sufficient to render alp7cut7pkl1 triply deleted cells viable and promote spindle assembly, indicating that Alp14-mediated microtubule polymerization from the nuclear face of the spindle pole body could generate outward force in place of Cut7 during early mitosis. The third pathway involves the Ase1/PRC1 microtubule cross-linker that stabilizes antiparallel microtubules. Our study, therefore, unveils multifaceted interplay among kinesin-dependent and -independent pathways leading to mitotic bipolar spindle assembly.