The Caenorhabditis elegans protein SAS-5 forms large oligomeric assemblies critical for centriole formation.
The Caenorhabditis elegans protein SAS-5 forms large oligomeric assemblies critical for centriole formation.
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DOI：
10.7554/elife.07410
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发表时间：
2015-05-29
期刊：
影响因子：
7.7
通讯作者：
Vakonakis I
中科院分区：
文献类型：
--
作者：
Rogala KB;Dynes NJ;Hatzopoulos GN;Yan J;Pong SK;Robinson CV;Deane CM;Gönczy P;Vakonakis I
中心粒是基于微管的细胞器，对细胞分裂、感知和运动至关重要。在秀丽隐杆线虫中，中心粒形成的开始特别需要蛋白质SAS-5和SAS-6，它们在真核生物进化中具有功能等同物。尽管SAS-6的分子结构及其在启动中心粒形成中的作用已被充分理解，但SAS-5及其相关功能的机制尚不清楚。在这里，我们结合联合收割机生物物理和结构分析，揭示SAS-5的架构，并检查其在体内的功能意义。我们的工作表明，两个不同的自缔合结构域是必要的，以形成更高阶的SAS-5的低聚物：一个三聚体卷曲螺旋和一个新的球状二聚体的隐式结构域。破坏任何一个结构域导致蠕虫胚胎中心粒复制失败，表明大的SAS-5组件在体内的功能是必要的。http://dx.doi.org/10.7554/eLife.07410.001大多数动物细胞都含有被称为中心粒的结构。通常，不分裂的细胞含有一对中心粒。但是当细胞准备分裂时，中心粒就复制了。然后，这两对中心粒组织起脚手架，在细胞分裂时在新形成的细胞之间平等地分享遗传物质。中心粒组装受到严格的调控，这一过程中的异常可能导致发育缺陷和癌症。中心粒可能含有数百种蛋白质，但其中只有少数是中心粒组装所必需的。新的中心粒通常由一种类似侧手翻的蛋白质排列组装而成，其中包括一种名为SAS-6的蛋白质。在秀丽隐杆线虫中，SAS-6与另一种称为SAS-5的蛋白质结合。这种相互作用对于中心粒的形成是必不可少的，但其背后的原因尚不清楚。现在，Rogala等人已经使用了一系列技术，包括X射线晶体学，生物物理学和蠕虫胚胎研究来研究SAS-5在C.优雅这些实验表明，SAS-5蛋白可以通过每个蛋白的两个区域相互作用，称为“卷曲螺旋”和以前未识别的“隐含结构域”。这些区域驱动包含多个SAS-5蛋白的组装体的形成。接下来，Rogala等人询问SAS-5组装是否对中心粒复制很重要。突变的蠕虫胚胎，其中SAS-5蛋白不能相互作用，未能形成新的中心粒。这导致了细胞分裂的缺陷。Cottee，Muschalik等人的一项独立研究获得了类似的结果，并发现果蝇相当于SAS-5，称为Ana 2，也可以自我缔合，并且这种活性是中心粒复制所必需的。现在需要进一步的工作来了解SAS-5和SAS-6如何相互作用以形成中心粒核心的初始框架。DOI：http://dx.doi.org/10.7554/eLife.07410.002网站
Centrioles are microtubule-based organelles crucial for cell division, sensing and motility. In Caenorhabditis elegans, the onset of centriole formation requires notably the proteins SAS-5 and SAS-6, which have functional equivalents across eukaryotic evolution. Whereas the molecular architecture of SAS-6 and its role in initiating centriole formation are well understood, the mechanisms by which SAS-5 and its relatives function is unclear. Here, we combine biophysical and structural analysis to uncover the architecture of SAS-5 and examine its functional implications in vivo. Our work reveals that two distinct self-associating domains are necessary to form higher-order oligomers of SAS-5: a trimeric coiled coil and a novel globular dimeric Implico domain. Disruption of either domain leads to centriole duplication failure in worm embryos, indicating that large SAS-5 assemblies are necessary for function in vivo. DOI: http://dx.doi.org/10.7554/eLife.07410.001 Most animal cells contain structures known as centrioles. Typically, a cell that is not dividing contains a pair of centrioles. But when a cell prepares to divide, the centrioles are duplicated. The two pairs of centrioles then organize the scaffolding that shares the genetic material equally between the newly formed cells at cell division. Centriole assembly is tightly regulated and abnormalities in this process can lead to developmental defects and cancer. Centrioles likely contain several hundred proteins, but only a few of these are strictly needed for centriole assembly. New centrioles usually assemble from a cartwheel-like arrangement of proteins, which includes a protein called SAS-6. In the worm Caenorhabditis elegans, SAS-6 associates with another protein called SAS-5. This interaction is essential for centrioles to form, but the reason behind this is not clearly understood. Now, Rogala et al. have used a range of techniques including X-ray crystallography, biophysics and studies of worm embryos to investigate the role of SAS-5 in C. elegans. These experiments revealed that SAS-5 proteins can interact with each other, via two regions of each protein termed a ‘coiled-coil’ and a previously unrecognized ‘Implico domain’. These regions drive the formation of assemblies that contain multiple SAS-5 proteins. Next, Rogala et al. asked whether SAS-5 assemblies are important for centriole duplication. Mutant worm embryos, in which SAS-5 proteins could not interact with one another, failed to form new centrioles. This resulted in defects with cell division. An independent study by Cottee, Muschalik et al. obtained similar results and found that the fruit fly equivalent of SAS-5, called Ana2, can also self-associate and this activity is required for centriole duplication. Further work is now needed to understand how SAS-5 and SAS-6 work with each other to form the initial framework at the core of centrioles. DOI: http://dx.doi.org/10.7554/eLife.07410.002