Mechanism of heterochromatin assembly and oncogenic histone mutations

项目摘要 组蛋白的共价修饰，如乙酰化、甲基化、磷酸化和泛素化，是 染色质结构和功能的基本调节因子。对这些修改的监管存在缺陷 在许多发育障碍和疾病中起因果作用。然而，目标是 针对特定基因组位置的组蛋白修饰酶并不能很好地调节其酶活性 明白了。我们的长期目标是了解不同的组蛋白修饰活动是如何协调的 利用异染色质组装和致癌组蛋白启动和维持不同的表观遗传状态 突变作为实验模型。 异染色质优先组装在重复的DNA元件上，对于调节 基因表达和维持基因组完整性。异染色质的形成是至关重要的 依赖于H3赖氨酸9(H3K9)的甲基化，通常认为精确的靶向 组蛋白H3K9甲基转移酶将异染色质限制在特定的基因组区域。然而，我们最近 研究表明，在分裂酵母中，H3K9甲基转移酶CLR4的靶向不是非常精确，并且 细胞严重依赖负性调节因子，如Mst2组蛋白乙酰转移酶和Epe1组蛋白 去甲基酶，以去除不适当位置的异染色质。因此，我们将分析分子 Mst2和Epe1在异染色质形成中的作用，并检测它们的活性是如何变化的 环境信号来调节异染色质动态。 最近的高通量测序分析发现，体细胞组蛋白赖氨酸到组蛋白赖氨酸的发生率很高。 多种癌症中的蛋氨酸(K-to-M)突变。这些突变阻止了野生型组蛋白的甲基化。 然而，人们对这些突变发挥作用的分子细节知之甚少，却知之甚少。 有争议的。我们已经建立了H3K9M或H3K36M导入的裂殖酵母模型 转基因消除了野生型组蛋白上相应赖氨酸的甲基化，类似于 哺乳动物系统中的这些突变。我们将研究这些突变是如何调节细胞功能和 确定可以有针对性地杀死含有K-to-M突变的细胞的途径。 这些研究的最终目标是完全了解组蛋白甲基化是如何调控的，以及 它们的突变和失调是如何导致人类疾病的。

Project Summary Covalent modifications of histones, such as acetylation, methylation, phosphorylation, and ubiquitylation, are essential regulators of chromatin structure and function. Defects in the regulation of these modifications have causal roles in numerous developmental disorders and diseases. However, the mechanisms that target histone-modifying enzymes to specific genomic locations and regulate their enzymatic activities are not well understood. Our long-term goal is to understand how diverse histone modification activities are coordinated to initiate and maintain different epigenetic states using heterochromatin assembly and oncogenic histone mutations as experimental models. Heterochromatin preferentially assembles at repetitive DNA elements and it is essential for the regulation of gene expression and the maintenance of genome integrity. Formation of heterochromatin is critically dependent on the methylation of H3 lysine 9 (H3K9), and it is generally assumed that precise targeting of histone H3K9 methyltransferases confines heterochromatin to specific genomic regions. However, our recent studies demonstrate that in fission yeast the targeting of H3K9 methyltransferases Clr4 is not very precise, and cells rely critically on negatively regulators, such as the Mst2 histone acetyltransferase and the Epe1 histone demethylase, to remove heterochromatin at inappropriate locations. We will therefore analyze the molecular functions of Mst2 and Epe1 in heterochromatin formation, and examine how their activities change in response to environmental signals to regulate heterochromatin dynamics. Recent high throughput sequencing analyses discovered high incidences of somatic histone lysine-to- methionine (K-to-M) mutations in multiple cancers. These mutations block the methylation of wild type histones. However, the molecular details by which these mutations function are poorly understood and are highly controversial. We have established fission yeast models in which the introduction of H3K9M or H3K36M transgenes abolished the methylation of corresponding lysines on wild type histones, similar to the effects of these mutations in mammalian systems. We will examine how these mutations regulate cellular functions and identify pathways that can be targeted to selectively kill cells containing K-to-M mutations. The ultimate goal of these studies is a complete understanding of how histone methylations are regulated and how their mutations and dysregulation contribute to human diseases.