Mechanism of Epigenetic Inheritance

摘要 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细胞内的遗传信息。 基因组完整性染色质进一步组织成不同的功能结构域，如异染色质和异染色质。 常染色质，含有不同的翻译后组蛋白修饰（PTM）。不同的染色质 在细胞周期的S期，状态是遗传的，这是细胞周期中最具挑战性的问题之一。 染色质和表观遗传领域。这个复杂过程的“第一”步是将复制的DNA组装成 核小体使用亲本和新合成的组蛋白的过程中，是紧密耦合到正在进行的 DNA合成我们一直在研究DNA复制后核小体是如何形成的， 为这一进程做出了重大贡献。然而，亲本组蛋白（H3-H4）2四聚体， 表观遗传修饰的主要载体，转移到复制DNA仍然知之甚少， 阻碍了我们对表观遗传信息传递到子细胞的理解。主要 理解亲本组蛋白（H3-H4）2组装的挑战是缺乏跟踪这一过程的方法。 过程我们已经开发了eSPAN（富集和测序蛋白质相关新生DNA） 一种可以辨别蛋白质是否与DNA复制叉的前导链或滞后链结合的方法， 酵母和小鼠胚胎干（ES）细胞。这种方法使得有可能确定在以下方面起作用的因素： 亲本组蛋白的核小体组装（H3-H4）2.此外，我们还发现， 组蛋白转移损害内源性逆转录病毒（ERVs）的抑制，ERVs是重复DNA元件， 通常通过基于异染色质的机制沉默。其他研究表明，癌症中ERV的重新激活 细胞导致对免疫疗法的反应增加。在这个建议中，我们将阐明分子 亲本（H3-H4）2在酵母中DNA复制后重新组装成核小体的机制 和小鼠ES细胞，并确定该过程中的缺陷如何影响ERV沉默。所有这些 研究将解决有关染色质复制和表观遗传的基本问题， 还提供了新的见解，一个主要的表观遗传机制，提高了癌细胞的反应， 免疫疗法

Abstract 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.