Boulder Laboratory for 3-D Electron Microscopy of Cells, University of Colorado Boulder, Boulder, Colorado, United States of America.
PLoS One. 2012;7(1):e29795. doi: 10.1371/journal.pone.0029795. Epub 2012 Jan 10.
As part of a multi-subunit ring complex, γ-tubulin has been shown to promote microtubule nucleation both in vitro and in vivo, and the structural properties of the complex suggest that it also seals the minus ends of the polymers with a conical cap. Cells depleted of γ-tubulin, however, still display many microtubules that participate in mitotic spindle assembly, suggesting that γ-tubulin is not absolutely required for microtubule nucleation in vivo, and raising questions about the function of the minus end cap. Here, we assessed the role of γ-tubulin in centrosomal microtubule organisation using three-dimensional reconstructions of γ-tubulin-depleted C. elegans embryos. We found that microtubule minus-end capping and the PCM component SPD-5 are both essential for the proper placement of microtubules in the centrosome. Our results further suggest that γ-tubulin and SPD-5 limit microtubule polymerization within the centrosome core, and we propose a model for how abnormal microtubule organization at the centrosome could indirectly affect centriole structure and daughter centriole replication.
作为多亚基环复合物的一部分，γ-微管蛋白已被证明可在体外和体内促进微管的核形成，并且该复合物的结构特性表明它还可以用锥形帽密封聚合物的负端。然而，耗尽γ-微管蛋白的细胞仍然显示出许多参与有丝分裂纺锤体组装的微管，这表明γ-微管蛋白在体内并非微管核形成所必需的，这引发了对负端帽功能的质疑。在这里，我们使用三维重构的γ-微管蛋白耗尽的秀丽隐杆线虫胚胎评估了γ-微管蛋白在中心体微管组织中的作用。我们发现微管负端封盖和 PCM 成分 SPD-5 对于微管在中心体中的正确位置都是必需的。我们的结果进一步表明，γ-微管蛋白和 SPD-5 限制了中心体核心内的微管聚合，我们提出了一个模型，解释了中心体中异常的微管组织如何间接影响中心粒结构和子中心粒复制。
