Interrogating the roles of canonical versus variant histone H3 in genome function during aging

项目总结 组蛋白将DNA打包并组织成染色质，染色质调节每一个依赖DNA的过程。 染色质结构的改变是衰老的标志，其特征是基因的全局变化 表达、组蛋白丰度、组蛋白PTM景观和染色质可及性。我建议严格控制 过高的组蛋白丰度和组蛋白类型，我们称之为组蛋白动态平衡，是正常细胞所必需的。 衰老。细胞含有两种组蛋白类型：典型的组蛋白，在细胞周期的S期表达， 以及在整个细胞周期和非分裂细胞中表达的变异组蛋白。变异组蛋白是 对衰老特别感兴趣，因为它们是非分裂细胞中新组蛋白的唯一来源， 随着年龄的增长而积累。此外，变异组蛋白的错误调节会导致染色质缺陷和减少 寿命。了解标准组蛋白和变异组蛋白如何调节基因组功能是理解 正常和病理性的以染色质为基础的衰老过程。典型的组蛋白H3.2和变异组蛋白H3.3是 真核生物中一些高度保守的蛋白质。氨基酸差异的高度保守性 经典的H3.2和变异的H3.3之间的差异表明，它们可能在基因组中发挥独特的功能 目前尚不清楚H3.3变异体的功能是由其独立于细胞周期的表达还是由独特的蛋白质介导的 序列。在果蝇身上，我发现H3.3变体在正常情况下对发育是必不可少的 组蛋白基因拷贝数减少，暗示了以前未知的对组蛋白基因之间协调的要求 规范的H3.2和变异型H3.3的表达。然而，这种协调的基础机制是 未知。拟议的项目测试了正常染色质所需的变异体H3.3的假设 衰老过程和细胞具有维持正确的相对表达的动态平衡机制 在整个开发过程中，规范的H3.2和变种H3.3。本项目的目的是(1)确定 H3.3表达与蛋白质序列在染色质衰老过程中的作用 通过规范和变异组蛋白的协调获得适当的H3丰度的机制 表情。这项工作将扩大对正则组蛋白和变异组蛋白如何 合作调节衰老过程中的基因组功能。

PROJECT SUMMARY Histone proteins package and organize DNA into chromatin, which regulates every DNA-dependent process. Alterations to chromatin structure is a hallmark of aging and is characterized by global changes in gene expression, histone abundance, histone PTM landscape, and chromatin accessibility. I propose that tight control over histone abundance and histone type, which we term histone homeostasis, is essential for normal cellular aging. Cells contain two histone types: canonical histones that are expressed during S phase of the cell cycle, and variant histones that are expressed throughout the cell cycle and in non-dividing cells. Variant histones are of particular interest to aging because they are the only source of new histones in non-dividing cells and accumulate with age. Additionally, variant histone misregulation results in chromatin defects and reduced lifespan. Knowing how canonical and variant histones regulate genome function is integral to understanding normal and pathological chromatin-based aging processes. Canonical histone H3.2 and variant histone H3.3 are some of the most highly conserved proteins across eukaryotes. The high conservation of amino acid differences between canonical H3.2 and variant H3.3 suggests that they may perform unique functions in the genome, yet it is not understood if variant H3.3 function is mediated by its cell-cycle independent expression or unique protein sequence. In Drosophila, I have discovered that variant H3.3 is essential for development when canonical histone gene copy number is reduced, suggesting a previously unknown requirement for coordination between canonical H3.2 and variant H3.3 expression. However, the mechanisms underlying this coordination are unknown. The proposed project tests the hypotheses that variant H3.3 is required for normal chromatin-based aging processes and that cells possess a homeostatic mechanism to maintain the correct relative expression of canonical H3.2 and variant H3.3 throughout development. The aims of this project are to (1) determine the contributions of H3.3 expression versus protein sequence to chromatin-based aging processes and, (2) elucidate the mechanisms that achieve proper H3 abundance through the coordination of canonical and variant histone expression. This work will expand the fundamental understanding of how canonical and variant histones cooperate to regulate genome function during aging.