Microtubules assemble near most kinetochores during early prometaphase in human cells.
Microtubules assemble near most kinetochores during early prometaphase in human cells.
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DOI：
10.1083/jcb.201710094
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发表时间：
2018-08-06
期刊：
影响因子：
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通讯作者：
Khodjakov A
中科院分区：
文献类型：
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作者：
Sikirzhytski V;Renda F;Tikhonenko I;Magidson V;McEwen BF;Khodjakov A
相关的光电子显微镜显示微管组装在人类细胞有丝分裂开始时大多数动粒附近。这些微管和动粒之间的初始横向相互作用转化为端对附件是由驱动蛋白CenpE促进的。这项工作表明，动粒纤维主要通过捕获局部有核的非中心体微管形成。为了在细胞分裂过程中正确分离，每条染色体必须通过称为动粒纤维（K-纤维）的微管束连接到纺锤体的两极。K-纤维通过两种不同的机制形成：（1）由染色体的着丝粒捕获在中心体处成核的星形微管;或（2）着丝粒附着到非中心体微管，随后将这些微管的负端运输到纺锤体极。这些替代机制的相对贡献正常主轴组装仍然未知。在这项研究中，我们报告说，人类细胞中的大多数动粒通过第二种机制产生K纤维。相关的光电子显微镜表明，从发病的纺锤体组装，短随机取向的非中心体微管出现在紧邻的动粒。最初，这些微管相互作用的动粒横向，但端对附件的形式迅速在前中期的前3分钟。从横向到端上相互作用的转换受到阻碍后，抑制的正末端导向的kinetochore-associated驱动蛋白CenpE。
Correlative light electron microscopy reveals microtubule assembly near most kinetochores at the onset of mitosis in human cells. Conversion of the initially lateral interactions between these microtubules and kinetochores into end-on attachments is facilitated by the kinesin CenpE. This work suggests that kinetochore fibers predominately form via capture of locally nucleated noncentrosomal microtubules. For proper segregation during cell division, each chromosome must connect to the poles of the spindle via microtubule bundles termed kinetochore fibers (K-fibers). K-fibers form by two distinct mechanisms: (1) capture of astral microtubules nucleated at the centrosome by the chromosomes’ kinetochores or (2) attachment of kinetochores to noncentrosomal microtubules with subsequent transport of the minus ends of these microtubules toward the spindle poles. The relative contributions of these alternative mechanisms to normal spindle assembly remain unknown. In this study, we report that most kinetochores in human cells develop K-fibers via the second mechanism. Correlative light electron microscopy demonstrates that from the onset of spindle assembly, short randomly oriented noncentrosomal microtubules appear in the immediate vicinity of the kinetochores. Initially, these microtubules interact with the kinetochores laterally, but end-on attachments form rapidly in the first 3 min of prometaphase. Conversion from lateral to end-on interactions is impeded upon inhibition of the plus end–directed kinetochore-associated kinesin CenpE.