Histone acetylation couples DNA replication to nucleosome assembly

描述（由申请人提供）：维持基因组稳定性对细胞存活至关重要，对预防致癌作用至关重要。事实上，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复制调控中涉及的所有方面至关重要。然而，相对较少的研究涉及染色质结构（真核细胞中DNA的生理组织）如何影响和调节DNA复制过程。在DNA复制过程中，染色质必须暂时分解，以允许DNA复制机器访问DNA模板。然后，新合成的DNA链立即重新组装成其原始的染色质状态。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，重要的是要了解DNA合成是如何耦合到染色质组装。我们使用酵母酿酒酵母作为真核模式生物，以解决这个重要的问题，但知之甚少的过程。最近的研究表明，组蛋白H3上赖氨酸56的乙酰化（H3-K56）是DNA合成和染色质组装过程中的关键调控事件。H3-K56的乙酰化在S期短暂发生。H3-K56乙酰化改变的细胞对DNA损伤剂高度敏感，表明这种修饰对维持基因组稳定性很重要。本提案的主要目的是检验H3-K56的乙酰化的一种新的和独特的HAT Rtt 109，我们最近发现，保持基因组的完整性，通过耦合DNA复制与组装的新复制的DNA到核小体介导的组蛋白伴侣。这些研究的结果将提供机制的见解组蛋白修饰的作用，耦合DNA合成与核小体组装，在维持基因组稳定性，从而正常的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.