Understanding the roles of histone H3 variants in promoting genomic and epigenomic stability during DNA replication and aging

项目摘要： 在有丝分裂和有丝分裂后， 细胞，以防止有害的突变，可导致疾病，如癌症， 神经退行性疾病在增殖细胞中，DNA复制需要 与转录和DNA修复相协调，以防止发生和遗传 的突变。在终末分化的非复制细胞如神经元中，染色质具有 长时间保持稳定，以维持已建立的转录程序。与 这个建议，我们试图了解组蛋白H3变异体对基因组的贡献， 以及DNA复制和老化过程中的表观基因组稳定性。复制级别- 依赖性H3.1/H3.2变异体和复制非依赖性H3.3变异体改变 在增殖细胞中的DNA复制过程中以及在有丝分裂后的细胞中， 细胞我们之前已经表明，H3.1和H3.3变体可以具有不同的 在植物表观基因组上的生化功能，这是由一个可变的氨基介导的 这两种高度保守蛋白质的N-末端尾部的氨基酸残基（位置31）。 通过对H3 K27甲基转移酶ATXR 5和ATXR 6（ATXR 5/6）的研究， 已经证明，新合成的H3.1变异体被特异性甲基化， ATXR/6在DNA复制过程中的突变，以及H3.1变体在K27处未甲基化 （H3.1K27me0）而不是H3.3K27me0诱导基因组不稳定性。我们将调查 H3.1调节植物基因组稳定性的生化和细胞机制 使用遗传和生化筛选染色质相互作用蛋白质， 区分H3.1和H3.3。我们还将使用组蛋白替代策略， 分析所有组蛋白在维持或破坏DNA过程中基因组稳定性的作用 复制的最后，我们将重复这些实验，以研究H3变体在 使用果蝇作为模型系统，在老化的神经元中维持异染色质。的 H3.1、H3.3和染色质修饰蛋白之间的高水平相似性 真核生物表明，通过这种方法将揭示的分子机制， 工作将在人类中保存，并涉及由基因组或 表观基因组不稳定性

Project Summary: Maintaining genome and epigenome stability is required in both mitotic and post-mitotic cells to prevent deleterious mutations that can cause diseases like cancer and neurodegenerative disorders. In proliferative cells, DNA replication needs to be coordinated with transcription and DNA repair to prevent the occurrence and inheritance of mutations. In terminally differentiated, non-replicating cells like neurons, chromatin has to be stable for long periods of time to maintain established transcriptional programs. With this proposal, we seek to understand the contributions of histone H3 variants to genomic and epigenomic stability during DNA replication and aging. Levels of replication- dependent H3.1/H3.2 variants and replication-independent H3.3 variants change drastically during DNA replication in proliferating cells and through time in post-mitotic cells. We have shown previously that H3.1 and H3.3 variants can have different biochemical functions on the epigenome in plants, which are mediated by a variable amino acid residue (position 31) in the N-terminal tail of these two highly conserved proteins. Through the study of the H3K27 methyltransferases ATXR5 and ATXR6 (ATXR5/6), we have demonstrated that newly synthesized H3.1 variants are specifically methylated by ATXR/6 during DNA replication, and that H3.1 variants unmethylated at K27 (H3.1K27me0), but not H3.3K27me0, induce genomic instability. We will investigate the biochemical and cellular mechanisms by which H3.1 regulates genomic stability in plants using genetic and biochemical screens for chromatin-interacting proteins that can discriminate between H3.1 and H3.3. We will also use a histone replacement strategy to analyze the roles of all histones in maintaining or disrupting genomic stability during DNA replication. Finally, we will replicate these experiments to study the role of H3 variants in maintaining heterochromatin in aging neurons using Drosophila as a model system. The high levels of similarity between H3.1, H3.3 and chromatin-modifying proteins across all eukaryotes suggest that the molecular mechanisms that will be uncovered through this work will be conserved in humans and involved in diseases caused by genomic or epigenomic instability.