The XMAP215 Ortholog Alp14 Promotes Microtubule Nucleation in Fission Yeast.
The XMAP215 Ortholog Alp14 Promotes Microtubule Nucleation in Fission Yeast.
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DOI：
10.1016/j.cub.2018.04.008
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发表时间：
2018-06-04
期刊：
影响因子：
--
通讯作者：
Chang F
中科院分区：
文献类型：
--
作者：
Flor-Parra I;Iglesias-Romero AB;Chang F
细胞内微管的组织和数量取决于微管成核的适当调控。目前，成核机制是MT动力学中最鲜为人知的一个方面。XMAP215/chTOG/Alp14/Stu2蛋白是一种MT聚合酶，通过结合和释放微管蛋白二聚体来刺激MT+末端的MT聚合。虽然这些蛋白在体外也定位于MT组织中心并具有成核活性，但这些蛋白在体内是否参与MT成核尚不清楚。在这里，我们证明了在裂殖酵母中，XMAP215同源基因Alp14对于体内高效的MT成核至关重要。在多次检测中，Alp14功能的丧失导致成核率和间期MT束数量减少。相反，Alp14的激活导致成核频率增加。ALP14与MTO-1和γ-微管蛋白复合体结合，并人工靶向γ-TURCS刺激成核。在对单个成核事件进行成像时，我们发现Alp14在新MT出现前不久与γ-微管蛋白颗粒短暂地联系在一起。TACC同源Alp7介导Alp14在成核位而不是正末端定位，是有效成核所必需的，但不是MT聚合所必需的。我们的发现提供了迄今为止最有力的证据，证明Alp14在体内是一个关键的MT成核因子。我们建议了一个模型，在该模型中，Alp14以Alp7依赖的方式与γ-微管蛋白复合体结合，以促进新生MT的组装或稳定。微管是一种动态聚合物，有助于组织细胞内容物并分裂细胞。新的微管是通过成核过程产生的，在这个过程中，微管蛋白亚单位被缝合在一起，开始形成中空管。Flor-Parra等人。确定XMAP215/Alp14是一个可能促进微管组装的成核因子。
The organization and number of microtubules (MTs) in a cell depends on the proper regulation of MT nucleation. Currently, the mechanism of nucleation is the most poorly understood aspect of MT dynamics. XMAP215/chTOG/Alp14/Stu2 proteins are MT polymerases that stimulate MT polymerization at MT plus ends by binding and releasing tubulin dimers. Although these proteins also localize to MT organizing centers and have nucleating activity in vitro, it is not yet clear whether these proteins participate in MT nucleation in vivo. Here, we demonstrate that in the fission yeast Schizosaccharomyces pombe, the XMAP215 ortholog Alp14 is critical for efficient MT nucleation in vivo. In multiple assays, loss of Alp14 function led to reduced nucleation rate and numbers of interphase MT bundles. Conversely, activation of Alp14 led to increased nucleation frequency. Alp14 associated with Mto1 and γ-tubulin complex components, and artificially targeting Alp14 to the γ-TuRCs stimulated nucleation. In imaging individual nucleation events, we found that Alp14 transiently associated with a γ-tubulin particle shortly before the appearance of a new MT. The TACC ortholog Alp7 mediated the localization of Alp14 at nucleation sites but not plus ends, and was required for efficient nucleation but not for MT polymerization. Our findings provide the strongest evidence to date that Alp14 serves as a critical MT nucleation factor in vivo. We suggest a model in which Alp14 associates with the γ-tubulin complex in an Alp7-dependent manner to facilitate the assembly or stabilization of the nascent MT. Microtubules are dynamic polymers that help to organize cellular contents and divide the cell. New microtubules arise by a process of nucleation, in which tubulin subunits are stitched together to begin forming a hollow tube. Flor-Parra et al. identify XMAP215/Alp14 as a nucleation factor that may facilitate the assembly of the microtubule.
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