Centromere Identity and Function

描述(申请人提供)：细胞分裂时染色体平均分割的缺陷会导致非整倍体，这是一种遗传灾难，如果它出现在配子中，就会导致自发流产或出生缺陷，这是几乎所有人类癌症中基因剂量失衡的主要原因。着丝粒是每个染色体上的一个位置，它在健康细胞的细胞分裂时指导着染色体的准确分离。这个项目的重点是解决关于着丝粒的两个相关的主要问题：指定人类着丝粒的表观遗传标记的性质是什么，以及这个表观遗传标记是如何通过细胞分裂传播的？着丝粒是在细胞分裂时赋予遗传稳定性的染色体基因座，但通常在该基因座上发现的DNA序列既不是必需的，也不是必需的 也不足以发挥着丝粒作用。相反，着丝粒是通过表观遗传过程在后生动物和许多其他真核生物中指定的。表遗传着丝粒规范的关键是组蛋白H3变异体CENP-A，在这个提案中，我们现在建立在我们在上一个资助周期中关于其结构/动力学、细胞循环偶联染色质组装以及它定向到人类着丝粒和新着丝粒的着丝粒组件的组织和招募方面的主要发现的基础上。我们已经确定了三个关键的研究领域，现在已经成熟，可以在着丝粒上获得主要的见解：1)确定组蛋白/DNA颗粒的主要形式，它在功能性的人类着丝粒上组装成组蛋白/DNA颗粒--代表着丝粒染色质的基本单位和表观指定着丝粒位置的最佳候选者；2)确定着丝粒遗传的细胞周期耦合程序的分子基础；以及3)研究CENP-A核小体在单个着丝粒上的稳定性和其他着丝粒成分在其中的作用。我们将使用生化、基因组、蛋白质组、分子遗传学和细胞生物学的方法来探讨这些主题，这些研究将有望对指定和保持着丝粒在染色体上的位置的表观遗传学机制产生有价值的见解。

DESCRIPTION (provided by applicant): Defects in the equal partitioning of chromosomes at cell division causes aneuploidy, a genetic catastrophe that results in spontaneous abortion or birth defects if it arises in the gametes and that is a major contributor to gene dosage imbalances in almost all human cancers. The centromere is the locus on each chromosome that directs accurate chromosome segregation at cell division in healthy cells. The focus of this project is to address two related major questions regarding centromeres: what is the nature of the epigenetic mark that specifies human centromeres and how is this epigenetic mark propagated through cell divisions? Centromeres are the chromosomal loci that confer genetic stability at cell division, but the DNA sequences typically found at the loci are neither necessary nor sufficient for centromere function. Rather, centromeres are specified in metazoans and many other eukaryotes through an epigenetic process. Key to epigenetic centromere specification is a histone H3 variant, CENP-A, and in this proposal we now build on the major findings we made in the previous funding cycle regarding its structure/dynamics, cell cycled-coupled chromatin assembly, and the organization and recruitment of centromere components it directs to human centromeres and neocentromeres. We have identified three critical areas of investigation that are now ripe for eliciting major insight at centromeres: 1) identifying the majo form of the histone/DNA particle into which it assembles at functional human centromeres-representing the fundamental unit of centromeric chromatin and the prime candidate to epigenetically specify centromere location, 2) determining the molecular basis for the cell cycle-coupled program of centromere inheritance, and 3) investigating the stability of CENP-A nucleosomes at individual centromeres and the role therein of other centromere constituents. We will pursue these topics using biochemical, genomic, proteomic, molecular genetic and cell biological approaches, and together these studies have the promise to generate valuable insight into the epigenetic mechanisms that specify and maintain centromere location on the chromosome.