Kinetochore Specification and Function

项目摘要 细胞分裂过程中复制基因组的精确划分对于所有细胞的正常发育都是至关重要的。 有机体染色体分离错误导致非整倍体，这是癌症的标志，也是癌症的常见起源 出生缺陷染色体分离机制也是癌症治疗中的重要靶标， 在许多癌症中观察到的染色体错误分离率升高与治疗相关， 阻力因此，阐明确保准确染色体分离的机制具有潜力， 有助于了解癌症的起源，并指导新的治疗策略的发展。一 染色体分离的中心角色是动粒，它是有丝分裂时进行装配的机器。 染色体与纺锤体微管的界面。该接口的机制与 调节机制，调节肌动蛋白微管附着的强度，正确的附着 错误，并阻止细胞周期的进展，直到所有的染色体连接到纺锤体。机械和 在动粒处，通过保守的Knl 1复合物/Mis 12复合物/Ndc 80协调调节功能 KMN蛋白质网络。虽然在表征激酶方面已经取得了实质性进展， 控制染色体分离的机械和调节方面，了解保守的 相对于激动素定位的磷酸酶，蛋白磷酸酶1（PP 1c）已经落后。目标1和2 通过定义控制动粒定位、活性和底物的机制来解决这一差距 PP 1c的特异性，除了确定Kinetochore-docked PP 1c如何控制后期开始， 调节微管附着。为了确保染色体的准确分离，染色体必须达到 在纺锤体上的双向取向，姐妹染色单体只与相反的纺锤体相连的状态 波兰人广泛研究的途径，如纺锤体检查点和极光激酶的纠错， 确保双向性。我们定义了一种在双向定位后起作用的途径，以确保准确的分离， 稳定正确定向的运动舞蹈-微管附着。目标2还侧重于了解 这一途径的机制基础，其中涉及保守的kinetochore定位之间的协调， 微管结合Ndc 80和Ska复合物及其通过PP 1c协调的潜在调节。最后， 目标3追求我们在多细胞遗传模型中的工作中出现的两个新方向。一是 基于我们发现KMN网络在神经细胞的形成中具有重要的非有丝分裂作用， 胚胎发育过程中的系统。第二个是基于我们令人惊讶的发现， 保守的纺锤体检查点成分的功能是不依赖于着丝粒的促进有丝分裂进入， 生殖细胞在这一最终目标中提出的工作将定义新的和意想不到的生物学功能， 研究了染色体分离机制，并有可能影响针对 癌症中这种机制的治疗靶向。

PROJECT SUMMARY Accurate partitioning of the replicated genome during cell division is essential for the normal development of all organisms. Chromosome segregation errors lead to aneuploidy, a hallmark of cancer and a common origin of birth defects. The chromosome segregation machinery is also an important target in cancer therapy and elevated rates of chromosome missegregation, observed in many cancers, are associated with therapeutic resistance. Thus, elucidating the mechanisms ensuring accurate chromosome segregation has the potential to contribute to understanding the genesis of cancer and guide the development of new therapeutic strategies. A central player in chromosome segregation is the kinetochore, the machine that assembles on mitotic chromosomes to interface with spindle microtubules. The mechanics of this interface are integrated with regulatory mechanisms that modulate the strength of kinetochore-microtubule attachments, correct attachment errors, and prevent cell cycle progression until all chromosomes are connected to the spindle. Mechanical and regulatory functions are coordinated at the kinetochore by the conserved Knl1 complex/Mis12 complex /Ndc80 complex (KMN) protein network. While substantial progress has been made in characterizing the kinases that control the mechanical and regulatory aspects of chromosome segregation, understanding of the conserved opposing kinetochore-localized phosphatase, protein phosphatase 1 (PP1c) has lagged behind. Aims 1 and 2 address this gap by defining the mechanisms that control kinetochore localization, activity and substrate specificity of PP1c, in addition to determining how kinetochore-docked PP1c controls anaphase onset and regulates microtubule attachments. To ensure accurate chromosome segregation, chromosomes must achieve bi-orientation on the spindle, the state in which sister chromatids are exclusively connected to opposite spindle poles. Widely studied pathways such as the spindle checkpoint and error correction by Aurora kinases act to ensure bi-orientation. We defined a pathway that acts after bi-orientation to ensure accurate segregation by stabilizing properly oriented kinetochore-microtubule attachments. Aim 2 also focuses on understanding the mechanistic basis of this pathway, which involves coordination between the conserved kinetochore-localized microtubule-binding Ndc80 and Ska complexes and potential regulation of their coordination by PP1c. Finally, Aim 3 pursues two new directions that emerged from our working in a multicellular genetic model. The first is based on our discovery that the KMN network has an important non-mitotic role in formation of the nervous system during embryogenesis. The second is based on our surprising finding that the critical organismal function of conserved spindle checkpoint components is kinetochore-independent promotion of mitotic entry in the germline. The work proposed in this final aim will define new and unexpected biological functions for well- studied chromosome segregation machinery and has the potential to influence strategies directed at therapeutic targeting of this machinery in cancer.