Regulation of Centromeric Chromatin

描述（由申请人提供）：细胞分裂的完美执行对所有生物的产生和生存至关重要。在每个细胞周期中，染色体必须准确地划分到子细胞中，以防止基因组不稳定和非整倍体，这是所有肿瘤和许多出生缺陷的标志。我们正在研究出芽酵母的染色体分离，因为它适合遗传学和生化分析，而且染色体分离的机制基本上是保守的。染色体是通过着丝点分离的，着丝点是一种特殊的蛋白质结构，组装在着丝点DNA序列上，并介导与纺锤体的连接。由于着丝粒DNA序列不保守，着丝粒身份是通过表观遗传机制传播的。表观遗传调控的一个标志是一种特殊的染色质结构，其特征是组蛋白变体的存在和组蛋白独特的翻译后修饰。与此一致的是，所有真核着丝粒都含有着丝粒组装所需的基本组蛋白H3变体（CenH3），并且可能是指定着丝粒同一性的表观遗传标记。此外，H2A。在许多生物体中，Z组蛋白变异定位于周着丝粒和着丝粒染色质，着丝粒含有与常染色质不同的组蛋白修饰模式。虽然一个特殊的染色质结构对着丝粒的身份和功能至关重要，但组装和维持着丝粒染色质的机制尚未阐明。因此，我们将采用互补的生化和遗传学方法来确定在着丝粒中沉积CenH3的因素。此外，我们将确定在着丝粒维持CenH3并阻止其定位到常染色质的机制。最后，我们开发了一种富集与着丝粒相关的组蛋白的方法，这将使我们能够识别对染色体分离很重要的着丝粒特异性组蛋白修饰。综上所述，这些研究将有助于更好地理解所有真核生物的染色体分离、着丝粒同一性和基因组稳定性的维持。

DESCRIPTION (provided by applicant): The flawless execution of cell division is essential to the generation and survival of all organisms. During every cell cycle, chromosomes must be accurately partitioned to daughter cells to prevent genomic instability and aneuploidy, a hallmark of all tumors and many birth defects. We are studying chromosome segregation in budding yeast because it is amenable to both genetic and biochemical analyses, and the mechanism of chromosome segregation is fundamentally conserved. Chromosomes segregate using their kinetochores, the specialized protein structures that are assembled on centromeric DNA sequences and mediate attachment to the spindle. Because centromeric DNA sequences are not conserved, centromere identity is propagated by an epigenetic mechanism. A hallmark of epigenetic regulation is a specialized chromatin structure that is characterized by the presence of histone variants and unique post-translational modifications to histones. Consistent with this, all eukaryotic centromeres contain an essential histone H3 variant (CenH3) that is required for kinetochore assembly and is likely to be the epigenetic mark that specifies centromere identity. In addition, the H2A.Z histone variant localizes to pericentromeric and centromeric chromatin in a number of organisms, and centromeres contain a distinct histone modification pattern relative to euchromatin. Although a specialized chromatin structure is essential for centromere identity and function, the mechanisms that assemble and maintain centromeric chromatin have not been elucidated. We will therefore take complementary biochemical and genetic approaches to identify factors that deposit CenH3 at centromeres. In addition, we will identify the mechanisms that maintain CenH3 at the centromere and prevent it from localizing to euchromatin. Finally, we have developed a method to enrich for histones associated with centromeres that will allows us to identify centromere-specific histone modifications that are important for chromosome segregation. Taken together, these studies will lead to a better understanding of chromosome segregation and the maintenance of centromere identity and genomic stability in all eukaryotes. Project Narrative All cells must inherit the right number of chromosomes every time they divide because the wrong number of chromosomes is a hallmark of all cancers and a number of birth defects. We are therefore studying the process of chromosome partitioning to daughter cells when they divide to understand the basis for a number of human diseases.