Mechanism of Epigenetic Inheritance

在真核细胞中，基因组 DNA 被包装到染色质中，染色质编码表观遗传信息并维持 基因组完整性。染色质进一步组织成不同的功能域，例如异染色质和 常染色质，包含不同的翻译后组蛋白修饰 (PTM)。染色质状态如何不同 在细胞周期的 S 期遗传是染色质中最具挑战性的问题之一 表观遗传领域。这个复杂过程的“第一步”是将复制的 DNA 组装成核小体 在与正在进行的 DNA 合成紧密耦合的过程中使用亲本和新合成的组蛋白。 我们一直在研究 DNA 复制后核小体是如何形成的，并取得了多项重大成果 对此过程的贡献。然而，亲本组蛋白 (H3-H4)2 四聚体（表观遗传的主要载体）如何 修饰，转移到复制DNA仍然知之甚少，这阻碍了我们的理解 将表观遗传信息传递到子细胞中。理解父母的主要挑战 组蛋白(H3-H4)2组装目前缺乏追踪这一过程的方法。我们开发了eSPAN （富集和测序蛋白质相关新生 DNA）可以辨别蛋白质是否存在的方法 与酵母和小鼠胚胎干 (ES) 细胞中 DNA 复制叉的前导链或滞后链结合。 该方法使得鉴定在亲本组蛋白（H3- H4)2。此外，我们发现亲代组蛋白转移缺陷的细胞会损害对 内源性逆转录病毒 (ERV)，通常通过基于异染色质的沉默的重复 DNA 元件 机制。其他研究表明，癌细胞中的 ERV 重新激活会导致对免疫疗法的反应增强。 在本提案中，我们将阐明亲本 (H3-H4)2 重新组装成的分子机制 酵母和小鼠 ES 细胞中 DNA 复制后的核小体，并确定这种缺陷如何 过程影响 ERV 沉默。这些研究将共同解决有关染色质的基本问题 复制和表观遗传，同时还提供了对主要表观遗传机制的新见解 增强癌细胞对免疫疗法的反应。

In eukaryotic cells, genomic DNA is packaged into chromatin that encodes epigenetic information and maintain genome integrity. Chromatin is further organized into distinct functional domains, such as heterochromatin and euchromatin, that contain different post-translational histone modifications (PTM). How different chromatin states are inherited during S phase of the cell cycle is one of the most challenging questions in the chromatin and epigenetic fields. The “first” step in this complex process is the assembly of replicated DNA into nucleosomes using both parental and newly-synthesized histones in a process that is tightly coupled to ongoing DNA synthesis. We have been studying how nucleosomes are formed following DNA replication and have made multiple major contributions to this process. However, how parental histone (H3-H4)2 tetramers, the primary carrier of epigenetic modifications, are transferred to replicating DNA is still poorly understood, which hinders our understanding of the transmission of epigenetic information into daughter cells. The major challenge to understanding parental histone (H3-H4)2 assembly is a lack of methods to track this process. We have developed the eSPAN (enrichment and Sequencing Protein- Associated Nascent DNA) method that can discern whether a protein binds to leading or lagging strands of DNA replication forks in both yeast and mouse embryonic stem (ES) cells. This method makes it possible to identify factors that function in nucleosome assembly of parental histone (H3- H4)2. Moreover, we discovered that cells defective in parental histone transfer compromise the repression of endogenous retrovirus (ERVs), repetitive DNA elements that are normally silenced via a heterochromatin-based mechanism. Others show that ERV reactivation in cancer cells leads to increased response to immunotherapy. In this proposal, we will elucidate the molecular mechanisms whereby parental (H3-H4)2 are reassembled into nucleosomes following DNA replication in yeast and mouse ES cells and determine how deficiencies in this process impact ERV silencing. Together, these studies will address fundamental questions regarding chromatin replication and epigenetic inheritance, while also providing novel insights into a major epigenetic mechanism that boosts the response of cancer cells to immunotherapy.