Regulation of Microtubule Dynamics and Organization During Cell Division

 描述（由申请人提供）：有丝分裂是一组复制的染色体在两个子细胞之间均匀分布的过程。因为细胞需要完整的遗传蓝图才能正常运作，所以有丝分裂必须在没有错误的情况下发生，即使是单个染色体的错误分离也可能是遗传疾病，癌症和死亡的原因。染色体是由一个基于微管的细胞机器分离的，称为纺锤体。纺锤体的一个关键特征是它的双极几何结构，这种结构自然地允许染色体在两个方向上分离。其他组织状态，如单极或多极，在很大程度上与生命不相容，并通过凋亡引起细胞死亡。本更新申请的重点是如何建立和维持纺锤体双极性。在大多数真核细胞中，纺锤体双极性由驱动蛋白-5马达Eg 5建立。然而，我们在之前的资助周期中发现，人类癌细胞的双极性可以通过一种新的Eg 5依赖机制建立。这一发现具有重要的临床意义，因为驱动蛋白-5抑制剂（K5 I）在早期临床试验中作为抗癌剂表现不佳。我们的工作表明，无效的K5 Is可能源于替代，补偿纺锤体组装途径。一旦纺锤体形成，它必须保持双极，尽管存在与Eg 5相反的力。Eg 5-反对/协助部队的来源，幅度和时间波动没有得到很好的表征，但我们的数据牵连的kinetochore-attached微管（K-MT）的参与。在这项补助金中，我们将：1）确定K-MT何时以及如何有助于双极性维持; 2）研究Eg 5独立纺锤体组装的第二驱动蛋白（Kif 15）关键的特征;以及3）进一步表征非经典纺锤体组装机制及其生理缺陷。这项工作将推进我们的纺锤体力学的理解，并直接相关的发展，抗有丝分裂化疗策略。

 DESCRIPTION (provided by applicant): Mitosis is the process by which a replicated set of chromosomes is equally distributed between two daughter cells. Because cells require a complete genetic blueprint to function properly, it is essential for mitosis to occur without error mis-segregation of even a single chromosome can be the cause of genetic disease, cancer, and death. Chromosomes are segregated by a microtubule-based cellular machine termed the spindle. A key feature of the spindle is its bipolar geometry, an organization that naturally allow chromosomes to be segregated in two directions. Other organizational states, such as monopolarity or multipolarity, are largely incompatible with life and cause cell death via apoptosis. This renewal application is focused on how spindle bipolarity is both established and maintained. Spindle bipolarity in most eukaryotic cells is established by Eg5, a kinesin-5 motor. However, we discovered in the previous grant cycle that bipolarity in human cancer cells can be established through a novel Eg5-indpendent mechanism. This finding has important clinical implications, as kinesin-5 inhibitors (K5Is) have not performed well as anti-cancer agents in early stage clinical trials. Our work suggests that the inefficacy of K5Is may stem from alternative, compensatory spindle assembly pathways. Once the spindle has formed, it must remain bipolar despite the presence of forces that act in opposition to Eg5. The source, magnitude and temporal fluctuations of Eg5-opposing/assisting forces are not well-characterized, but our data implicate the involvement of kinetochore-attached microtubules (K- MTs). In this grant, we will: 1) Determine when and how K-MTs contribute to bipolarity maintenance; 2) Study features of a second kinesin (Kif15) key for Eg5-independent spindle assembly; and 3) Further characterize non-canonical spindle assembly mechanisms and their physiological shortcomings. This work will advance our understanding of spindle mechanics and have immediate relevance to the development of anti-mitotic chemotherapeutic strategies.