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连接子组蛋白在染色体结构和活性中的功能。我们建议使用果蝇作为一个模型系统，因为它为研究染色体结构和遗传活性提供了许多优势，而且因为果蝇H1与哺乳动物H1连接物组蛋白非常相似。在后生动物中，H1几乎和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的结构方面发挥着重要作用。H1可以在几个水平上影响染色质的功能，包括局部水平的单个核小体颗粒和阵列，以及决定染色质折叠成更高阶结构的长期水平。H1被认为影响基因表达和核DNA代谢的许多其他反应，如复制、重组和修复。我们关于连接子组蛋白作用的大部分知识来自于体外研究。然而，对H1功能的体内分析一直滞后。最近，我们利用RNA干扰(RNAi)在体内几乎完全耗尽了果蝇体内的H1。这种方法使我们能够证明H1是果蝇发育所必需的，也是正常染色体结构所必需的。我们确定异染色质的结构和活性是H1调控的主要靶点。我们还发现，H1对基因表达既有积极的影响，也有消极的影响。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协同作用的因素来调节基因组的表观遗传状态，并发现依赖H1发挥正常功能的其他细胞过程，我们建议追求以下特定目标。(1)我们将阐明H1调节异染色质结构和活性的机制。(2)我们将描述在体内与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和功能分析。这项拟议研究的成功完成有望为了解染色质的这一主要成分如何影响真核染色体的结构和活性提供重要的见解。

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.