Ministry of Education Key Laboratory of Cell Proliferation and Differentiation and State Key Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, China.
Proc Natl Acad Sci U S A. 2013 Sep 17;110(38):15295-300. doi: 10.1073/pnas.1312382110. Epub 2013 Sep 3.
Kinetochore capture by dynamic kinetochore microtubule fibers (K fibers) is essential for proper chromosome alignment and accurate distribution of the replicated genome during cell division. Although this capture process has been extensively studied, the mechanisms underlying the initiation of this process and the proper formation of the K fibers remain largely unknown. Here we show that transforming acidic coiled-coil-containing protein 3 (TACC3) is essential for kinetochore capture and proper K-fiber formation in HeLa cells. To observe the assembly of acentrosomal microtubules more clearly, the cells were released from higher concentrations of nocodazole into zero or lower concentrations. We find that small acentrosomal TACC3-microtubule aster formation near the kinetochores and binding of the asters with the kinetochores are the initial steps of the kinetochore capture by the acentrosomal microtubules, and that the sorting of kinetochore-captured acentrosomal microtubules with centrosomal microtubules leads to the capture of kinetochore by centrosomal microtubules from both spindle poles. We demonstrate that the sorting of the TACC3-associated microtubules with the centrosomal microtubules is a crucial process for spindle assembly and chromosome movement. These findings, which are also supported in the unperturbed mitosis without nocodazole, reveal a critical TACC3-dependent acentrosomal microtubule nucleation and sorting process to regulate kinetochore-microtubule connections and provide deep insight into the mechanisms of mitotic spindle assembly and chromosome alignment.
动粒捕捉由动态动粒微管纤维（K 纤维）介导，对于细胞分裂过程中染色体的正确排列和复制基因组的准确分配至关重要。尽管这个捕获过程已经被广泛研究，但这个过程的起始机制和 K 纤维的正确形成仍然很大程度上未知。在这里，我们发现转化酸性卷曲螺旋蛋白 3（TACC3）对于 HeLa 细胞中的动粒捕获和适当的 K 纤维形成是必不可少的。为了更清楚地观察无中心体微管的组装，我们将细胞从较高浓度的诺考达唑中释放出来，进入零或更低浓度的环境中。我们发现，在动粒附近形成的小的无中心体 TACC3-微管星状体和星状体与动粒的结合是无中心体微管捕获动粒的初始步骤，并且被捕获的动粒的无中心体微管与中心体微管的分选导致动粒被来自纺锤体两极的中心体微管捕获。我们证明了与中心体微管相关的 TACC3 微管的分选是纺锤体组装和染色体运动的关键过程。这些发现也在没有诺考达唑的未受干扰的有丝分裂中得到支持，揭示了一个关键的 TACC3 依赖的无中心体微管成核和分选过程，以调节动粒-微管连接，并深入了解有丝分裂纺锤体组装和染色体排列的机制。
