Ran GTPase cycle and importins α and β are essential for spindle formation and nuclear envelope assembly in living Caenorhabditis elegans embryos
Ran GTPase cycle and importins α and β are essential for spindle formation and nuclear envelope assembly in living Caenorhabditis elegans embryos
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DOI：
10.1091/mbc.e02-06-0346
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发表时间：
2002-12-01
影响因子：
3.3
通讯作者：
Mattaj, IW
中科院分区：
文献类型：
--
作者：
Askjaer, P;Galy, V;Mattaj, IW
小GTPase Ran已被发现在细胞功能的几个方面发挥关键作用。我们研究了Ran GTPase循环在秀丽隐杆线虫胚胎分裂过程中纺锤体形成和核膜组装中的作用。我们发现Ran及其辅助因子RanBP2、RanGAP和RCC1对细胞分裂后核膜的重组都是必不可少的。通过RNAi减少Ran GTPase循环中任何这些成分的表达会导致完整核膜蛋白和核孔蛋白在核外聚集。Ran、RanBP2和RanGAP也是构建有丝分裂纺锤体所必需的，而星体微管在缺乏这些蛋白质的情况下是正常的。RCC1（RNAi）胚胎在纺锤体形成的初始阶段也有类似的异常，但最终恢复形成双极纺锤体。由于纺锤体失效，染色质结构不规则和染色质桥在Ran周期受到干扰的胚胎中经常被观察到。此外，中心体和雄性原核之间的连接，以及中心体的定位，都取决于Ran周期的成分。最后，我们已经证明，脊椎动物输入α和β的同源蛋白IMA-2和IMB-1在早期胚胎的纺锤体组装和核形成中都是必不可少的。
The small GTPase Ran has been found to play pivotal roles in several aspects of cell function. We have investigated the role of the Ran GTPase cycle in spindle formation and nuclear envelope assembly in dividing Caenorhabditis elegans embryos in real time. We found that Ran and its cofactors RanBP2, RanGAP, and RCC1 are all essential for reformation of the nuclear envelope after cell division. Reducing the expression of any of these components of the Ran GTPase cycle by RNAi leads to strong extranuclear clustering of integral nuclear envelope proteins and nucleoporins. Ran, RanBP2, and RanGAP are also required for building a mitotic spindle, whereas astral microtubules are normal in the absence of these proteins. RCC1(RNAi) embryos have similar abnormalities in the initial phase of spindle formation but eventually recover to form a bipolar spindle. Irregular chromatin structures and chromatin bridges due to spindle failure were frequently observed in embryos where the Ran cycle was perturbed. In addition, connection between the centrosomes and the male pronucleus, and thus centrosome positioning, depends upon the Ran cycle components. Finally, we have demonstrated that both IMA-2 and IMB-1, the homologues of vertebrate importin alpha and beta, are essential for both spindle assembly and nuclear formation in early embryos.