Histone acetylation couples DNA replication to nucleosome assembly

描述(由申请人提供)：保持基因组的稳定性对细胞生存至关重要，对预防癌变至关重要。的确，遗传不稳定性是癌细胞的关键特征之一。由于DNA复制中的错误是基因组不稳定的主要原因，因此了解DNA复制调控的各个方面是至关重要的。然而，关于染色质结构的研究相对较少，染色质结构是真核细胞中DNA的生理组织，它如何影响和调节DNA复制过程。在DNA复制过程中，染色质必须临时分解，以允许DNA复制机制访问DNA模板。然后，新合成的DNA链立即重新组装成它们原来的染色质状态。DNA合成和染色质组装的解偶联导致基因组不稳定。由于基因组稳定性的关键性质，了解DNA合成与染色质组装是如何耦合的是很重要的。我们使用酵母酿酒酵母作为真核模式生物来解决有关这一基本但知之甚少的过程的问题。最近的研究表明，组蛋白H3(H3-K56)上赖氨酸56的乙酰化是DNA合成和染色质组装过程中的一个关键调控事件。H3-K56的乙酰化发生在S阶段。H3-K56乙酰化改变的细胞对DNA损伤剂高度敏感，这表明这种修饰对维持基因组的稳定很重要。这一提议的主要目的是检验这样一种假设，即我们最近发现的一种新颖而独特的HAT Rtt109对H3-K56进行乙酰化处理，通过将DNA复制与组蛋白伴侣蛋白介导的新复制的DNA组装成核小体来维持基因组完整性。这些研究的结果将为组蛋白修饰在DNA合成和核小体组装中的作用提供机制方面的见解，这是维持基因组稳定性和正常细胞功能的一个重要方面。

DESCRIPTION (provided by applicant): Maintenance of genome stability is essential for cell survival and is critical for the prevention of carcinogenesis. Indeed, genetic instability is one of the key features of cancer cells. Because errors in DNA replication are a major cause of genomic instability, it is critical to understand all aspects involved in the regulation of DNA replication. However, relatively few studies have addressed how chromatin structure, the physiological organization of DNA in eukaryotic cells, impacts and regulates the DNA replication process. During DNA replication, chromatin must be temporarily disassembled to allow the DNA replication machinery access to the DNA template. The newly-synthesized DNA strands are then immediately reassembled into their original chromatin state. Uncoupling of DNA synthesis and chromatin assembly results in genome instability. Because of the critical nature of genome stability, it is important to understand how DNA synthesis is coupled to chromatin assembly. We use the yeast Saccharomyces cerevisiae as a eukaryotic model organism to address questions regarding this essential, but poorly understood process. Recent studies have implicated the acetylation of lysine 56 on histone H3 (H3-K56) as a key regulatory event during the DNA synthesis and chromatin assembly. Acetylation of H3-K56 occurs transiently during S phase. Cells with altered acetylation of H3-K56 are highly sensitive to DNA damaging agents, suggesting that this modification is important for maintaining genome stability. The main objective of this proposal is to test the hypothesis that acetylation of H3-K56 by a novel and unique HAT Rtt109, which we have recently identified, maintains genome integrity by coupling DNA replication with the assembly of newly-replicated DNA into nucleosomes mediated by histone chaperones. Results from these studies will provide mechanistic insights into the role of histone modifications in coupling DNA synthesis with nucleosome assembly, an important aspect in the maintenance of genome stability and thus normal cell functions.