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Maintenance of cellular memory through replication

通过复制维持细胞记忆

基本信息

批准号：
10673777
负责人：
Srinivas Ramachandran
金额：
$ 38.88万
依托单位：
UNIVERSITY OF COLORADO DENVER
依托单位国家：
美国
项目类别：
财政年份：
2019
资助国家：
美国
起止时间：
2019-08-09 至 2024-07-31
项目状态：
已结题

项目摘要

SUMMARY The ability to express different genes in different cell types is crucial to development of a multicellular organism. This cell-type specific gene expression relies on memory of activation and repression of genes through successive rounds of cell division as the organism develops from an embryo to an adult. An important component of the memory of cellular identity is the cell’s chromatin state. To maintain a transcriptional program, the cell has to maintain accessibility at active promoters and enhancers and occlusion at repressed promoters and enhancers. However, the passage of replication forks during every cell cycle obliterates cell-type specific chromatin landscapes. Our overarching goal is to determine how chromatin landscapes are sustained in spite of nucleosome dynamics throughout the cell cycle, thus maintaining cellular memory. Here, we will use genomic methods we develop(ed) to identify cellular mechanisms that maintain chromatin landscapes despite the erasing effects of replication. We will pursue two lines of investigations: First, we will identify how transcription factors find their binding sites after being stripped from the DNA during process of replication. We have shown that transcription factors are replaced by nucleosomes genome-wide post-replication. By tracking transcription factor binding to DNA and DNA accessibility as a function of time post-replication, we will uncover the determinants of transcription factor site selectivity. We will also study the effect of chromatin remodeler function in creating transcription factor binding sites post-replication. Second, we will elucidate cellular mechanisms that maintain repressed chromatin landscapes through replication at epigenetically silenced domains that are characterized by trimethylated histone H3 (H3K27me3), which we call “Polycomb domains”. Polycomb group proteins maintain repressed states at these domains. Mechanisms that carry memory of repression through replication have to act within a single cell cycle, every cell cycle. We will combine tracking chromatin states genome-wide post-replication with carefully chosen perturbations of Polycomb group proteins to uncover mechanisms that maintain this repressed state through replication. Taken together, these studies will not only resolve long-standing questions in transcription factor-site selectivity and Polycomb repression, but will also serve as a framework to understand how chromatin dynamics can shape genome function in many biological contexts.

摘要：在不同的细胞类型中表达不同基因的能力对肿瘤的发展至关重要。多细胞生物体。这种特殊的细胞型基因的表达依赖于人的记忆能力。基因的激活和抑制是通过连续几轮的细胞分裂过程来完成的。生物体从胚胎发育到成年，是人类记忆的重要组成部分。细胞身份的改变是细胞的主要染色质状态。因此，我们需要维持一个正常的转录调控程序。 CELL已经努力保持可访问性，包括积极的营养促进剂和促进剂，以及改善阻塞剂。抑制了基因的启动子和基因的增强子。然而，在这段时间里，基因复制的主要通道是分叉的。每一个细胞周期都会抹去细胞类型和特定的染色质景观。这是我们的首要目标。尽管存在核小体的动态变化，但仍无法确定染色质的景观是如何持续变化的。在整个细胞周期中，我们因此无法维持细胞的记忆。在这里，我们将不再使用基因组技术。我们将开发(Ed)方法来进一步确定维持染色质的细胞免疫机制。尽管复制的效果消失了，但景观仍然存在。我们将继续追求以下两条路线。调查：首先，我们将进一步确定转录因子如何找到它们的结合位点。在基因复制的过程中，我们被从DNA中剥离。我们已经证明了这一点。转录因子在复制后可能会被全基因组的核小体取代。跟踪转录因子与DNA的结合，以及提高DNA的可及性，是一项重要的功能。复制后，我们将不会发现转录因子和位点选择性的主要决定因素。我们还将研究染色质和重构体在创造转录过程中的作用。复制后结合结合位点的因素。其次，我们将进一步阐明与此相关的细胞调控机制。在表观遗传沉默的情况下，通过复制基因来维持被抑制的染色质和景观。这些结构域的特征是组蛋白H3(H3K27me3)的三甲基化，我们称之为H3K27me3。 “Polycomb结构域”。Polycomb将蛋白质分组，以维持至少在这些状态下被抑制的状态。域。那些通过复制来承载压抑记忆的机制必须采取行动。在一个单一的细胞周期内，每个细胞周期都是如此。我们还将结合对染色质状态的跟踪。全基因组和复制后测试，以及Polycomb组精心选择的干扰测试。蛋白质需要揭示维持这种状态的机制，这种状态是通过复制来实现的。综上所述，这些研究不仅将解决在转录过程中长期存在的问题。因地制宜的选择性和对Polycomb的压制，但它也将成为一个新的框架。了解染色质的动力学如何在许多生物生物学中塑造其基因组和功能。上下文。