Chromatin regulated DNA replication

描述（由申请人提供）：真核生物基因组的繁殖依赖于从许多起源开始的DNA复制。起源活性需要结合和激活复制前复合体（pre-Replicative Complex, pre-RC）。然而，在多细胞真核生物中，染色体上的某些区域如何被选择用于pre-RC结合和激活尚不清楚；关于DNA的共识尚未形成。此外，作为起源的基因组位点，以及它们在S期启动的时间，可以在发育过程中发生变化，但尚不清楚是什么决定了这种发育特异性。我们采用了一个基于果蝇蛋壳（绒毛膜）基因发育扩增的模型系统来研究果蝇的起源识别和基因组复制的调控。我们之前的研究结果表明，核小体乙酰化调节卵巢中绒毛膜和其他来源的发育特异性。我们建议通过使用遗传和分子方法研究核小体修饰影响起源活性的机制来扩展这项工作。该建议的一个重要方面是，它利用果蝇的方法来解决染色质在起源活动的发育特异性中的作用。我们的长期目标是描述起源处染色质修饰的全部功能，揭示染色质改变起源活性的机制，并发现这些修饰如何针对不同细胞类型发育中的特定起源。这项研究将为研究发育过程中基因组复制的表观遗传控制提供重要的新见解。

DESCRIPTION (provided by applicant): The propagation of the eukaryotic genome depends upon the initiation of DNA replication from numerous origins. Origin activity requires the binding and activation of a pre-Replicative Complex (pre-RC). In multi-cellular eukaryotes, however, it is not known how certain regions on chromosomes are selected for pre-RC binding and activation; a DNA consensus has yet to emerge. Moreover, the genomic sites that act as origins, and the time that they initiate during S phase, can change during development, but it is not known what determines this developmental specificity. We have employed a model system based on developmental amplification of Drosophila eggshell (chorion) genes to investigate origin identity and the regulation of genome duplication. Our previous results indicated that nucleosome acetylation regulates the developmental specificity of chorion and other origins in the ovary. We propose to extend this work by investigating the mechanism by which nucleosome modifications influence the activity of origins using genetic and molecular methods. An important aspect of this proposal is that it takes advantage of methods in Drosophila to address the role of chromatin in developmental specificity of origin activity. Our long term goals are to describe the full repertoire of chromatin modifications at origins, to reveal the mechanism by which chromatin alters origin activity, and to discover how these modifications are targeted to specific origins in different cell types in development. This investigation should lead to important new insights into the epigenetic control of genome duplication during development. Lay description: A complete and accurate copy of DNA must be made each cell division. To accomplish this large task, the cell starts copying from numerous "origins". How certain sites in the genome are chosen to be origins is not understood. This proposal investigates how the structure of chromosomes regulates where DNA replication starts in different cells. The results will provide a deeper understanding for how defects in this process contribute to human cancers, leading to better diagnosis and therapies.