Drosophila Linker Histone H1 Functions in Chromosome Architecture and Activity

描述（由申请人提供）：本提案的长期目标是了解H1连接体组蛋白在染色体结构和活性中的功能。我们建议使用果蝇（Drosphila melanogaster）作为模型系统，因为它为染色体结构和遗传活性的研究提供了许多优势，而且果蝇H1与哺乳动物H1连接蛋白非常相似。在后生动物中，H1几乎与核小体核心颗粒一样丰富，这表明它在建立和维持染色质纤维结构中起着重要作用。H1可以在多个水平上影响染色质功能，包括局部核小体颗粒和阵列水平，以及在长范围内决定染色质折叠成高阶结构。预计H1会影响基因表达和核DNA代谢的许多其他反应，如复制、重组和修复。我们对连接蛋白作用的了解大多来自体外研究。然而，体内对H1功能的分析一直滞后。最近，我们利用RNA干扰（RNAi）在体内几乎完全耗尽了黑腹果蝇的H1。这种方法使我们能够证明H1对果蝇的发育是必不可少的，并且它是正常染色体结构所必需的。我们发现异染色质结构和活性是H1调控的主要目标。我们还发现H1对基因表达有积极和消极的影响。为了更深入地了解H1控制染色体结构和基因活性的机制，确定与H1协同工作以调节基因组表观遗传状态的因素，并发现依赖H1正常功能的其他细胞过程，我们建议追求以下具体目标。(1)我们将阐明H1调控异染色质结构和活性的机制。(2)我们将在体内描述与H1功能相互作用的蛋白质网络。(3)我们将对H1进行详细的体内结构功能分析。这项研究的成功完成有望为染色质的主要组成部分影响真核生物染色体的结构和活性的方式提供重要的见解。

DESCRIPTION (provided by applicant): The long-term goal of this proposal is to understand the functions of H1 linker histone in chromosome structure and activity. We propose to use the fruit fly, Drosphila melanogaster, as a model system because it provides many advantages for studies of chromosome structure and genetic activity and because Drosophila H1 strongly resembles mammalian H1 linker histones. In metazoans, H1 is nearly as abundant as nucleosome core particles, suggesting that it plays important roles in establishing and maintaining the architecture of the chromatin fiber. H1 can influence chromatin functions at several levels, including locally at the level of individual nucleosome particles and arrays as well as over long range to determine the folding of chromatin into higher order structures. H1 is expected to affect gene expression and many other reactions of nuclear DNA metabolism, such as replication, recombination and repair. Much of our knowledge about the roles of linker histones comes from in vitro studies. However, in vivo analyses of H1 functions have been lagging. Recently, we used RNA interference (RNAi) to nearly completely deplete H1 in Drosophila melanogaster in vivo. This approach allowed us to demonstrate that H1 is essential for Drosophila development and that it is required for normal chromosome architecture. We identified heterochromatin structure and activity as primary targets of H1 regulation. We also found that H1 has both positive and negative effects on gene expression. To gain a deeper understanding of the mechanisms by which H1 controls chromosome structure and gene activity, to identify the factors that work in concert with H1 to regulate the epigenetic states of the genome, and to discover other cellular processes that depend upon H1 for proper function, we propose to pursue the following specific aims. (1) We will elucidate mechanisms by which H1 regulates the structure and activity of heterochromatin. (2) We will characterize the network of proteins that functionally interact with H1 in vivo. (3) We will perform a detailed in vivo structure-function analysis of H1. The successful completion of the proposed studies is expected to provide crucial insights into the ways in which this major component of chromatin affects the structure and activity of eukaryotic chromosomes. PUBLIC HEALTH RELEVANCE: The goals of this project are to understand the functions of a major component of all eukaryotic chromosomes called H1 linker histone. H1 is a key determinant of the structure and genetic activity of chromosomes. By collaborating with other components of chromosomes, H1 regulates the epigenetic state of the genome. Thus, H1 is a key intermediate in process that control normal embryonic/fetal development. When these processes are perturbed they contribute to the development of numerous human diseases including cancer.