Organization and Function of the Heterochromatin Holodomain and Subdomains

项目摘要/摘要 该项目的长期目标是阐明其组成、结构和生物物理特性。 异染色质，并了解它们对核功能的贡献。异染色质富含 重复的DNA，集中在着丝粒周围和端粒区域，形成明显的动态3D 核内结构域。异染色质是正常姐妹染色体配对和分离所必需的， 核结构、重组抑制、转座子沉默和基因沉默。异染色质 招募由表观遗传成分和机制调节，特别是二甲基化和三甲基化 组蛋白H3赖氨酸9(H3K9me2/3)通过特定的甲基转移酶。异染色质蛋白1(HP1)结合于此 “标记”并招募许多蛋白质和复合体到异染色质。我们目前缺乏一个明确的 了解异染色质结构域的精细结构和组织，以及生物物理 负责其功能和行为的属性。我们对果蝇的初步研究揭示了 异染色质出人意料的结构复杂性和生物物理特性提出了关于我们的 目前对该结构域的结构和功能的理解，并提示异染色质可能形成 并通过生物物理机制发挥作用，这些机制尚未与染色质结构和 功能。特别是，我们的发现导致了新的假设，即异染色质结构域通过一种 相分离机制，它最近被证明是功能分子的区隔 将网络转化为缺乏约束膜的结构，但到目前为止还没有应用于染色质 域名。 我们将利用这些新发现，并应用先进的成像、表观基因组学、生化和 生物物理方法阐明：1)结构、生化和生物物理性质 异染色质结构域，2)负责异染色质形成的成分和机制，以及 3)异染色质亚结构和生物物理性质对核和生物体的贡献 功能。检验相分离假说将阐明有关组织的重要信息 异染色质在细胞和动物中的作用，提供了提供范式转换的可能性 为了解其他染色质结构域的形成和功能奠定了基础。此外，有缺陷的 异染色质导致基因组不稳定和基因表达改变，导致癌症、出生 缺陷和老化。了解人类疾病和状况如何改变生物物理特性 潜在的异染色质的形成和功能最终将影响其诊断和治疗的方法 治疗。

PROJECT SUMMARY/ABSTRACT The long term goal of this project is to elucidate the composition, architecture, and biophysical properties of heterochromatin, and to understand how they contribute to nuclear functions. Heterochromatin is enriched in repeated DNAs, is concentrated in pericentromeric and telomeric regions, and forms a distinct and dynamic 3D domain inside nuclei. Heterochromatin is required for normal sister chromosome pairing and segregation, nuclear architecture, recombination suppression, transposon silencing, and gene silencing. Heterochromatin recruitment is regulated by epigenetic components and mechanisms, specifically di- and tri- methylation of histone H3 lysine 9 (H3K9me2/3) by specific methyltransferases. Heterochromatin Protein 1 (HP1) binds this `mark' and recruits many proteins and complexes to the heterochromatin. We currently lack a clear understanding of the fine structure and organization of the heterochromatin domain, and the biophysical properties responsible for its functions and behaviors. Our preliminary studies in Drosophila have revealed unexpected structural complexity and biophysical properties of heterochromatin that raise questions about our current understanding of the structure and function of this domain, and suggest that heterochromatin may form and function through biophysical mechanisms that have not been associated with chromatin structure and function. In particular, our findings led to the novel hypothesis that the heterochromatin domain forms through a phase separation mechanism, which has recently been shown to compartmentalize functional molecular networks into structures that lack constraining membranes, but has not until now been applied to chromatin domains. We will capitalize on these novel findings and apply advanced imaging, epigenomics, biochemical and biophysical approaches to elucidate: 1) the structural, biochemical and biophysical properties of the heterochromatin domain, 2) the components and mechanisms responsible for heterochromatin formation, and 3) the ways that heterochromatin substructure and biophysical properties contribute to nuclear and organismal functions. Testing the phase separation hypothesis will elucidate important information about the organization and function of heterochromatin in cells and animals, offering the potential of providing a paradigm-shifting foundation for understanding how other chromatin domains form and function. In addition, defective heterochromatin produces genome instability and altered gene expression, contributing to cancer, birth defects, and aging. Understanding how human diseases and conditions alter the biophysical properties that underlie heterochromatin formation and function will ultimately impact the approaches to their diagnosis and treatment.