Quimby B B, Wilson C A, Corbett A H
Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA.
Mol Biol Cell. 2000 Aug;11(8):2617-29. doi: 10.1091/mbc.11.8.2617.
The small GTPase Ran is required for the trafficking of macromolecules into and out of the nucleus. Ran also has been implicated in cell cycle control, specifically in mitotic spindle assembly. In interphase cells, Ran is predominately nuclear and thought to be GTP bound, but it is also present in the cytoplasm, probably in the GDP-bound state. Nuclear transport factor 2 (NTF2) has been shown to import RanGDP into the nucleus. Here, we examine the in vivo role of NTF2 in Ran import and the effect that disruption of Ran imported into the nucleus has on the cell cycle. A temperature-sensitive (ts) mutant of Saccharomyces cerevisiae NTF2 that does not bind to Ran is unable to import Ran into the nucleus at the nonpermissive temperature. Moreover, when Ran is inefficiently imported into the nucleus, cells arrest in G(2) in a MAD2 checkpoint-dependent manner. These findings demonstrate that NTF2 is required to transport Ran into the nucleus in vivo. Furthermore, we present data that suggest that depletion of nuclear Ran triggers a spindle-assembly checkpoint-dependent cell cycle arrest.
小分子GTP酶Ran是大分子进出细胞核运输所必需的。Ran也与细胞周期调控有关，特别是在有丝分裂纺锤体组装方面。在间期细胞中，Ran主要存在于细胞核中，被认为与GTP结合，但它也存在于细胞质中，可能处于与GDP结合的状态。核转运因子2（NTF2）已被证明能将RanGDP导入细胞核。在这里，我们研究了NTF2在Ran导入过程中的体内作用，以及导入细胞核的Ran受到干扰对细胞周期的影响。酿酒酵母NTF2的一个温度敏感（ts）突变体，它不与Ran结合，在非允许温度下无法将Ran导入细胞核。此外，当Ran导入细胞核的效率低下时，细胞会以依赖MAD2检查点的方式在G(2)期停滞。这些发现表明，NTF2在体内是将Ran运输到细胞核所必需的。此外，我们提供的数据表明，细胞核中Ran的耗尽会触发依赖纺锤体组装检查点的细胞周期停滞。
