Transmission of Epigenetic Information through Histone Proteins at Replication Forks

“表观遗传学”一词指的是改变基因表达的染色质变化。与DNA中编码的遗传信息不同，环境因素进一步影响和多样化细胞的表观遗传景观。重要的是，染色质的这些变化可以通过细胞分裂遗传，并使表型从母体细胞延续到子细胞。 我的研究项目主要集中在哺乳动物细胞如何继承和维持表观遗传信息，因为他们分裂。我对组蛋白特别感兴趣，它可以将DNA折叠并组织成核小体，最终形成染色质纤维。组蛋白被一系列酶严重修饰。这些修饰对染色质结构和基因表达有直接影响，并且可以通过许多细胞分裂遗传以影响基因活性。我的长期目标是确定在组蛋白上发现的表观遗传信息在细胞分裂时传递的细胞机制。这包括组蛋白本身的传递和繁殖，它们携带的表观遗传标记，以及影响染色质结构和基因表达的组蛋白结合蛋白。这项提议的直接目标是确定携带表观遗传信息的组蛋白在遇到复制叉时是如何分离的。 本文提出的工作使用了我开发的两种新的生化分析方法：第一种方法允许我分离出允许复制解旋酶解旋核小体DNA的因子;而第二种方法则测量组蛋白驱逐。总之，这些测定将用于鉴定在复制叉处分离组蛋白的蛋白质，以及启动组蛋白上发现的表观遗传信息的传递所需的蛋白质。然后将使用相同的测定来确定是否需要不同的因子来传递S期中的“开放”常染色质和“抑制”异染色质上的表观遗传信息。 这些结果将促进我们对细胞如何保持正确的DNA组织作为DNA复制的理解。它触及了一个基本的，但至关重要的问题，细胞功能与生物技术和细胞工程的直接影响。

The term 'epigenetics' refers to changes on chromatin that alter gene expression. Unlike the genetic information encoded in DNA proper, environmental factors further influence and diversify the epigenetic landscape of cells. Importantly, these changes to chromatin can be inherited through cell division and perpetuate phenotypes from mother to daughter cells. My research program focuses on how mammalian cells inherit and maintain epigenetic information as they divide. I am particularly interested in histone proteins, which fold and organize DNA into nucleosomes and, ultimately, chromatin fibres. Histones are heavily modified by a gamut of enzymes. These modifications have a direct impact on chromatin structure and gene expression, and can be inherited to influence gene activity through numerous cell divisions. My long-term goals are to identify the cellular mechanisms by which epigenetic information found on histones is transmitted as cells divide. This includes the transmission and propagation of histones proper, the epigenetic marks that they carry, and the histone-binding proteins that affect chromatin structures and gene expression. The immediate goals of this proposal are to determine how histones carrying epigenetic information segregate as they encounter the replication fork. The work proposed herein uses two novel biochemical assays that I have developed: the first will allow me to isolate factors that allow the replicative helicase to unwind nucleosomal DNA; whereas the second measures histone eviction. Together, these assays will be used to identify the proteins that segregate histones at replication forks and which are needed to initiate the transmission of epigenetic information found on histones. The same assays will then be used to determine whether different factors are needed to transmit epigenetic information on 'open' euchromatin and 'repressed' heterochromatin in S-phase. The results will advance our understanding of how cells maintain correct DNA organization as DNA duplicates. It touches on a fundamental, but vital question on cell function with direct implications in biotechnology and cell engineering.