Nuclear Pore Complexes As Scaffolds For Genome Architecture And Epigenetic Maintenance

摘要： 核孔复合体(NPC)是一种包埋核膜的多组分复合体， 它调节细胞核和细胞质之间的分子运输。除了……之外 它们在运输中的经典功能，鼻咽癌成分(Nup)已被牵涉到 通过与基因组结合进行转录调控。然而，转录的调控步骤是什么？ 是由NUP控制的，以及NUP的染色质结合作用是如何促进后生动物的 目前事态发展尚不明朗。我们确定了多个核蛋白与数百个核蛋白的结合 果蝇基因组中的启动子和增强子，并发现了一种以前未报道的 NPC在增强子-启动子环形成中的作用。具体地说，我们确定了Nup98 在由一种基因激活的基因上形成增强子-启动子环所必需的 发育激素蜕皮激素。在功能上，我们发现Nup98介导的丢失 增强子-启动子环影响随后激活的启动反应或 转录记忆。有趣的是，蜕皮激素调控的基因与核稳定相关 活化前后的孔洞，这表明后生动物的NPC可以作为一种 为等待未来激活事件的基因组织支架。总而言之，这些发现 暗示NUPS作为一类新的结构蛋白用于增强剂，并提示 通过核孔结合稳定增强子-启动子环构成了 表观遗传维持。我们预计核孔的这一功能将是高度相关的 后生动物发育过程中的基因调控。为了能够研究基因组- NUPS在发育基因调控中的组织作用，我们首先计划鉴定分子 Nup介导的增强子-启动子环的决定因素。因此，在目标1中，我们将定义 NUPS和其他哪些结构蛋白参与蜕皮激素的建立- 诱导的基因组环。此外，我们计划确定足以 系在NPC上或者是稳定环路所必需的。在目标2中，我们建议定义 Nup介导的增强子-启动子环的形成与转录的关系 激活和记忆，通过识别作为特定结果发生的染色质变化 对循环的恐惧。此外，我们将研究核蛋白在维持基因组环中的作用。 并确定一组全面的基因组接触，这些基因组接触是 受到核子核的控制。总而言之，这些实验有望扩大我们对 基因组结构、基因表达和核孔生物学的驱动力和原理。

Abstract: The Nuclear Pore Complex (NPC) is a nuclear envelope-embedded multi-component complex, which mediates transport of molecules between the nucleus and the cytoplasm. In addition to their classical function in transport, NPC components (Nups) have been implicated in transcriptional regulation via binding to the genome. Yet what regulatory steps of transcription are controlled by Nups and how chromatin-binding roles of Nups contribute to metazoan development is currently unclear. We identified the binding of multiple Nups to hundreds of promoters and enhancers in the Drosophila genome, and discovered a previously unreported role of the NPC in the formation of enhancer-promoter loops. Specifically, we identified Nup98 to be required for the formation of an enhancer-promoter loop at a gene activated by a developmental hormone ecdysone. Functionally, we found that the loss of Nup98-mediated enhancer-promoter loop affected the primed response to subsequent activation or transcriptional memory. Interestingly, ecdysone-regulated genes stably associated with nuclear pores before and after activation, suggesting that metazoan NPCs can be utilized as an organizing scaffold for genes awaiting future activation events. Together, these findings implicate Nups as a new class of architectural proteins for enhancers and suggest that stabilization of enhancer-promoter loops by nuclear pore binding constitutes a mechanism of epigenetic maintenance. We project that this function of the nuclear pore will be highly relevant to gene regulation during metazoan development. To be able to investigate the genome- organizing role of Nups in developmental gene regulation, we first plan to identify molecular determinants of Nup-mediated enhancer-promoter looping. Thus, in Aim 1, we will define which Nups and which other architectural proteins participate in the establishment of ecdysone- induced genomic loops. Additionally, we plan to identify DNA elements that are sufficient to tether to the NPC or that are necessary for loop stabilization. In Aim 2, we propose to define the relationship between formation of Nup-mediated enhancer-promoter loops and transcriptional activation and memory, by identifying chromatin changes that occur as a specific consequence of looping. Furthermore, we will examine the effect of Nups on maintenance of genomic loops in fly tissues during development and identify a comprehensive set of genomic contacts that are regulated by Nups. Together, these experiments are expected to expand our knowledge of the driving forces and principles of genome architecture, gene expression and nuclear pore biology.