Chromatin regulated DNA replication

描述（由申请人提供）：真核基因组的繁殖取决于从许多起点开始DNA复制。起源活动需要前复制复合物（pre-RC）的结合和激活。然而，在多细胞真核生物中，尚不清楚染色体上的某些区域是如何被选择用于前RC结合和激活的; DNA共识尚未出现。此外，作为起源的基因组位点，以及它们在S期启动的时间，可以在发育过程中改变，但不知道是什么决定了这种发育特异性。我们采用了一个基于发育扩增的果蝇卵壳（绒毛膜）基因的模型系统来研究起源身份和基因组复制的调控。我们以前的研究结果表明，核小体乙酰化调节卵巢绒毛膜和其他起源的发育特异性。我们建议通过研究核小体修饰影响使用遗传和分子方法的起源的活性的机制来扩展这项工作。这一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在起源的染色质修饰的全部剧目，揭示染色质改变起源活性的机制，并发现这些修饰是如何在发育中针对不同细胞类型的特定起源的。这项调查应导致重要的新的见解，在发展过程中的基因组复制的表观遗传控制。 简单描述：每次细胞分裂都必须复制一份完整准确的DNA。为了完成这个庞大的任务，细胞开始从许多“起源”复制。基因组中的某些位点是如何被选择为起源的还不清楚。该提案研究了染色体的结构如何调节DNA复制在不同细胞中的起始位置。研究结果将更深入地了解这一过程中的缺陷如何导致人类癌症，从而更好地诊断和治疗。

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.