Generation of GTP-bound Ran by RCC1 is required for chromatin-induced mitotic spindle formation
Generation of GTP-bound Ran by RCC1 is required for chromatin-induced mitotic spindle formation
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DOI：
10.1038/22133
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发表时间：
1999-07-08
期刊：
影响因子：
64.8
通讯作者：
Mattaj, IW
中科院分区：
文献类型：
--
作者：
Carazo-Salas, RE;Guarguaglini, G;Mattaj, IW
染色体由两组反向平行的微管阵列分隔，这些微管排列形成纺锤体装置。在细胞分裂过程中，细胞质微管的成核作用被阻止，纺锤体微管从中心体（在有丝分裂的动物细胞中）或染色体周围（在植物和一些减数分裂细胞中）成核（1,2）。在没有中心体的情况下染色体诱导局部微管成核的分子机制尚不清楚（3 - 5），但可以通过向非洲爪蟾卵提取物中添加染色质珠来研究（6）。这些珠子使微管成核，微管最终重新组织成一个双极纺锤体。RCC1是GTP酶蛋白Ran的鸟嘌呤核苷酸交换因子，是染色质的一个组成部分。利用染色质珠测定法，我们在此表明，染色体相关的RCC1蛋白的活性是纺锤体形成所必需的。当Ran处于与GTP结合的状态（Ran - GTP）时，它自身在M期提取物中诱导微管成核和纺锤体样结构。我们提出，RCC1在染色质周围产生高局部浓度的Ran - GTP，这反过来又诱导微管的局部成核。
Chromosomes are segregated by two antiparallel arrays of microtubules arranged to form the spindle apparatus. During cell division, the nucleation of cytosolic microtubules is prevented and spindle microtubules nucleate from centrosomes (in mitotic animal cells) or around chromosomes (in plants and some meiotic cells)(1,2). The molecular mechanism by which chromosomes induce local microtubule nucleation in the absence of centrosomes is unknown(3-5), but it can be studied by adding chromatin beads to Xenopus egg extracts(6). The beads nucleate microtubules that eventually reorganize into a bipolar spindle. RCC1, the guanine-nucleotide-exchange factor for the GTPase protein Ran, is a component of chromatin. Using the chromatin bead assay, we show here that the activity of chromosome-associated RCC1 protein is required for spindle formation. Ran itself, when in the GTP-bound state (Ran-GTP), induces microtubule nucleation and spindle-like structures in M-phase extract. We propose that RCC1 generates a high local concentration of Ran-GTP around chromatin which in turn induces the local nucleation of microtubules.