Mechanisms of Kinetochore Assembly

项目摘要 细胞必须在每次分裂时按顺序准确地将它们的染色体分离成子细胞 使细胞得以繁殖和增殖。染色体分离错误导致不平衡 在称为非整倍体的染色体拷贝数中，非整倍体是癌症的标志， 发育疾病，如唐氏综合症，是流产的主要原因。 这项工作的重点是了解细胞如何维持正常的染色体拷贝数 在染色体分离的过程中。染色体分离的关键调节因子 是染色体的动粒。动粒是连接在每条染色体上的位置 有丝分裂纺锤体的微管，这样染色体就可以在 细胞分裂。动点也通过有丝分裂来监测染色体的正确排列。 检查点，以确保每个子细胞获得每个染色体的一个副本。这个 着丝粒形成的基础是染色体上称为着丝粒的区域。 着丝粒是一种染色质结构域，由变体的存在唯一确定 组蛋白又称着丝粒蛋白A(CENP-A)。着丝粒的形成是表观遗传的。 由染色质中CENP-A的存在决定，一旦着丝粒形成，它就可以 稳定地保持，而不管它是基于什么DNA序列构建的。CENP-A染色质是 对于着丝粒和着丝粒的形成和CENP-A的突变或丢失是必不可少的，导致 着丝粒丢失和染色体错误分离。我们正在研究的机制是 CENP-A染色质的组装和维持以及CENP-A染色质如何被识别 着丝粒和着丝粒。在我们的第一个特定目标中，我们剖析了生物化学 在正确的时间和位置在染色体上构建CENP-A核小体的机制。在……里面 特别是，我们专注于了解新的CENP-A核小体的关键调控因子是如何 形成，Mis18复合体，是适当的靶向着丝粒以及它如何在 CENP-A组件。在我们的第二个目标中，我们探索着丝粒中DNA序列的功能 队形。尽管CENP-A是着丝粒功能的主要表观遗传决定因素 着丝粒上的DNA序列促进着丝粒的有效形成 维修。我们测试特定的DNA序列是否刺激CENP-A组装和 DNA或RNA分子是否主动调节新的CENP-A核小体形成。 我们的方法共同定义了着丝粒形成的基础，以及着丝粒的蛋白质如何 着丝粒产生了有丝分裂中染色体分离所需的特性。

Project Summary Cells must accurately segregate their chromosomes into daughter cells at each division in order for cells to reproduce and proliferate. Mistakes in chromosome segregation lead to imbalances in chromosome copy number termed aneuploidies that are hallmarks of cancer, that cause developmental diseases such as Down syndrome and that are a primary cause of miscarriage. This work is focused on understanding how cells maintain a normal chromosome copy number during the process of chromosome segregation. The key regulator of chromosome segregation is the chromosomal kinetochore. The kinetochore is the site on each chromosome that attaches to the microtubules of the mitotic spindle so that chromosome can move to daughter cells during cell division. Kinetochores also monitor proper chromosome alignment through the mitotic checkpoint to ensure that each daughter cell gets one copy of each chromosome. The foundation for kinetochore formation is a region of the chromosome termed the centromere. Centromeres are a chromatin domain that is uniquely determined by the presence of a variant histone termed centromere protein A (CENP-A). The formation of centromeres is epigenetically determined by the presence of CENP-A in chromatin and once a centromere is formed it can be stably maintained regardless of the DNA sequence on which it is built. CENP-A chromatin is essential for centromere and kinetochore formation and mutation or loss of CENP-A results in centromere loss and chromosome missegregation. We are studying the mechanisms that assemble and maintain CENP-A chromatin and how CENP-A chromatin is recognized to build the centromere and kinetochore. In our first specific Aim we dissect the biochemical mechanisms that build CENP-A nucleosomes at the right time and place in the chromosome. In particular, we focus on understanding how a key regulator of new CENP-A nucleosome formation, the Mis18 complex, is properly targeted to centromeres and how it functions in CENP-A assembly. In our second Aim we explore the function of DNA sequences in centromere formation. Although CENP-A is the primary epigenetic determinant of centromere function the sequence of the DNA at centromeres promotes efficient centromere formation and maintenance. We test whether specific DNA sequences stimulate CENP-A assembly and whether DNA or RNA molecules actively regulate new CENP-A nucleosome formation. Together our approach defines the basis for centromere formation and how the proteins of the centromere give rise to the properties required for chromosome segregation in mitosis.