Spindle Assembly in the Absence of a RanGTP Gradient Requires Localized CPC Activity
Spindle Assembly in the Absence of a RanGTP Gradient Requires Localized CPC Activity
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DOI：
10.1016/j.cub.2009.05.061
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发表时间：
2009-07-28
期刊：
影响因子：
9.2
通讯作者：
Salmon, Edward D.
中科院分区：
文献类型：
--
作者：
Maresca, Thomas J.;Groen, Aaron C.;Salmon, Edward D.
在动物细胞分裂过程中，有丝分裂染色质周围产生一个与GTP结合的Ran的梯度[1，2]。人们普遍认为，这种RanGTP梯度对于组织主轴是必不可少的，因为它在局部激活了关键的主轴组装因子[3-5]。这里，我们在非洲爪哇卵提取液中展示了，在没有RanGTP梯度的情况下，纺锤体可以在没有RanGTP梯度的情况下组装。无梯度纺锤体组装发生在精子核周围，但不发生在染色质涂层的珠子周围，需要染色体乘客复合体(CPC)。在含有固定化染色质和CPC的混合微珠阵列中人工浓缩CPC活性支持局部微管组装，即使在没有RanGTP梯度的情况下也是如此。我们得出结论，RanGTP和CPC构成了两个主要的分子信号，它们在空间上促进了染色质周围的微管聚合。此外，我们假设这两个信号主要来自染色体上离散的物理位置，以定位染色质周围的微管组装：来自任何染色质的RanGTP信号和主要来自着丝粒染色质的CPC依赖的信号。
During animal cell division, a gradient of GTP-bound Ran is generated around mitotic chromatin [1, 2]. It is generally accepted that this RanGTP gradient is essential for organizing the spindle, because it locally activates critical spindle assembly factors [3-5]. Here, we show in Xenopus laevis egg extract, where the gradient is best characterized, that spindles can assemble in the absence of a RanGTP gradient. Gradient-free spindle assembly occurred around sperm nuclei but not around chromatin-coated beads and required the chromosomal passenger complex (CPC). Artificial enrichment of CPC activity within hybrid bead arrays containing both immobilized chromatin and the CPC supported local microtubule assembly even in the absence of a RanGTP gradient. We conclude that RanGTP and the CPC constitute the two major molecular signals that spatially promote microtubule polymerization around chromatin. Furthermore, we hypothesize that the two signals mainly originate from discreet physical sites on the chromosomes to localize microtubule assembly around chromatin: a RanGTP signal from any chromatin and a CPC-dependent signal predominantly generated from centromeric chromatin.