Zhu Hui, Coppinger Judith A, Jang Chang-Young, Yates John R, Fang Guowei
Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA.
J Cell Biol. 2008 Dec 1;183(5):835-48. doi: 10.1083/jcb.200807046. Epub 2008 Nov 24.
Microtubules (MTs) are nucleated from centrosomes and chromatin. In addition, MTs can be generated from preexiting MTs in a gamma-tubulin-dependent manner in yeast, plant, and Drosophila cells, although the underlying mechanism remains unknown. Here we show the spindle-associated protein FAM29A promotes MT-dependent MT amplification and is required for efficient chromosome congression and segregation in mammalian cells. Depletion of FAM29A reduces spindle MT density. FAM29A is not involved in the nucleation of MTs from centrosomes and chromatin, but is required for a subsequent increase in MT mass in cells released from nocodazole. FAM29A interacts with the NEDD1-gamma-tubulin complex and recruits this complex to the spindle, which, in turn, promotes MT polymerization. FAM29A preferentially associates with kinetochore MTs and knockdown of FAM29A reduces the number of MTs in a kinetochore fiber, activates the spindle checkpoint, and delays the mitotic progression. Our study provides a biochemical mechanism for MT-dependent MT amplification and for the maturation of kinetochore fibers in mammalian cells.
微管（MTs）由中心体和染色质成核。此外，在酵母、植物和果蝇细胞中，微管可以以γ-微管蛋白依赖的方式从预先存在的微管生成，尽管其潜在机制尚不清楚。在这里，我们表明纺锤体相关蛋白FAM29A促进微管依赖的微管扩增，并且是哺乳动物细胞中有效染色体汇聚和分离所必需的。FAM29A的缺失会降低纺锤体微管密度。FAM29A不参与从中心体和染色质生成微管，但在从诺考达唑释放的细胞中，微管质量随后增加是必需的。FAM29A与NEDD1-γ-微管蛋白复合物相互作用，并将该复合物招募到纺锤体，进而促进微管聚合。FAM29A优先与动粒微管结合，敲低FAM29A会减少动粒纤维中的微管数量，激活纺锤体检查点，并延迟有丝分裂进程。我们的研究为哺乳动物细胞中微管依赖的微管扩增和动粒纤维成熟提供了一种生化机制。
