Role of Linker Histone H1 in Epigenetic Gene Regulation

项目概述：表观遗传机制对哺乳动物发育和细胞分化过程中染色质结构重编程和基因表达至关重要。H1连接组蛋白是与核小体核心颗粒相关的主要染色质结构蛋白，在介导高阶染色质结构折叠中起关键作用。然而，H1在表观遗传基因调控中的作用尚未被探索。之前，我们通过同时灭活3个H1连接组蛋白基因，证明了H1的总量对哺乳动物的发育至关重要。我们获得了三重H1空胚胎干细胞系，并表明H1在控制这些细胞中的几个印迹基因表达方面特别重要。我们还发现，这两个受影响位点的印迹控制区的DNA甲基化水平随着H1的减少而降低，从而提示H1和DNA甲基化之间存在新的联系。我们现在建议解决这种新型表观遗传联系的潜在机制，并在胚胎干细胞和小鼠模型中研究额外的H1调节表观遗传事件。具体来说，我们将：1)测试H1组蛋白是否通过DNA甲基转移酶的募集来调节特定DNA甲基化模式的建立或维持；2)确定额外的关键H1调控表观遗传事件，并描述这些事件的序列和功能依赖性，这些事件是适当控制基因表达所必需的；3)研究H1在胚胎发生和配子体发生过程中对表观遗传基因的体内调控作用。这些研究结果将促进我们对表观遗传基因调控机制的认识。相关性：异常的表观遗传基因调控是许多人类疾病的原因，如癌症和印迹基因疾病。了解表观遗传基因调控机制将为如何通过实验重新编程表观遗传信息以达到治疗目的提供关键线索。

DESCRIPTION (provided by applicant): Role of Linker Histone H1 in Epigenetic Gene Regulation Project Summary Epigenetic mechanisms are crucial for chromatin structure reprogramming and gene expression during mammalian development and cell differentiation. H1 linker histones are major chromatin structural proteins that associate with nucleosome core particles and play a key role in mediating higher order chromatin structure folding. However, the role of H1 in epigenetic gene regulation has not been explored. Previously we showed, by inactivating 3 H1 linker histone genes simultaneously, that the total amount of H1 is essential for mammalian development. We derived triple H1 null embryonic stem cell lines and showed that H1 is particularly important in controlling several imprinted gene expression in these cells. We also found that DNA methylation level at the imprinting control regions of these two affected loci is decreased with H1 reduction, thus suggesting a new link between H1 and DNA methylation. We now propose to address the underlying mechanisms of this novel epigenetic link and to investigate additional H1 regulated epigenetic events in embryonic stem cells and in mouse models. Specifically, we will: 1) Test whether H1 histones regulate establishment or maintenance of specific DNA methylation patterns through recruitment of DNA methyltransferases; 2) Identify additional critical H1 regulated epigenetic events and characterize the sequence and functional dependence of such events that are required for proper control of gene expression; 3) Study the in vivo regulatory role of H1 in epigenetic gene regulation during embryogenesis and gametogenesis. Findings from these studies will advance our knowledge of epigenetic gene regulation mechanisms. Relevance: Aberrant epigenetic gene regulation has been responsible for many human diseases, such as cancer and imprinted gene diseases. Understanding the epigenetic gene regulation mechanisms will provide critical clues as to how the epigenetic information can be experimentally reprogrammed for therapeutic purposes.