Functional Overlap of Microtubule Assembly Factors in Chromatin-Promoted Spindle Assembly
Functional Overlap of Microtubule Assembly Factors in Chromatin-Promoted Spindle Assembly
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DOI：
10.1091/mbc.e09-01-0043
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发表时间：
2009-06-01
影响因子：
3.3
通讯作者：
Mitchison, Timothy J.
中科院分区：
文献类型：
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作者：
Groen, Aaron C.;Maresca, Thomas J.;Mitchison, Timothy J.
来自中心体和染色质的不同途径被认为在动物细胞有丝分裂纺锤体组装过程中平行地促进微管成核和稳定，但其完整机制尚不清楚。我们研究了三个建议的成核/稳定因子，TPX 2，γ-微管蛋白和XMAP 215，在染色质促进非洲爪蟾卵提取物中的无星纺锤体组装的功能。除了传统的消耗-添加回实验，我们测试了因素是否可以相互替代，表明功能冗余。所有这三个因素都是微管聚合和双极纺锤体组装在染色质珠周围所必需的。通过添加过量的XMAP 215或EB 1或抑制MCAK（一种驱动蛋白-13），TPX 2的消耗被部分挽救。γ-微管蛋白或XMAP 215的消耗通过添加回XMAP 215而被部分挽救，但不能通过添加任何其他因子。这些数据揭示了染色质途径中特定组装因子之间的功能冗余，表明通常被视为必需的单个蛋白质或途径可能不具有完全独特的功能。
Distinct pathways from centrosomes and chromatin are thought to contribute in parallel to microtubule nucleation and stabilization during animal cell mitotic spindle assembly, but their full mechanisms are not known. We investigated the function of three proposed nucleation/stabilization factors, TPX2, gamma-tubulin and XMAP215, in chromatin-promoted assembly of anastral spindles in Xenopus laevis egg extract. In addition to conventional depletion-add back experiments, we tested whether factors could substitute for each other, indicative of functional redundancy. All three factors were required for microtubule polymerization and bipolar spindle assembly around chromatin beads. Depletion of TPX2 was partially rescued by the addition of excess XMAP215 or EB1, or inhibiting MCAK (a Kinesin-13). Depletion of either gamma-tubulin or XMAP215 was partially rescued by adding back XMAP215, but not by adding any of the other factors. These data reveal functional redundancy between specific assembly factors in the chromatin pathway, suggesting individual proteins or pathways commonly viewed to be essential may not have entirely unique functions.