Nuclear export of RNAs by nuclear envelope budding

描述（由申请人提供）：该项目的长期目标是表征超大核糖核蛋白颗粒（megaRNP）的核包装和输出的新途径及其对突触组装的影响。细胞生物学的一个长期原则是所有的核质运输都是通过核孔复合体（NPC）进行的。然而，使用果蝇神经肌肉接头（NMJ）作为模型系统，我们最近发现了megaRNP核输出的替代途径。这种非NPC依赖性途径有可能从根本上改变我们对核质通讯的理解。在该途径中，转录物被包装在细胞核内的megaRNP中，并通过在类似于疱疹型病毒的核出口的过程中通过核膜出芽而输出到细胞质。拟议的项目代表了一种深刻的方法来理解这一途径对细胞生物学的影响，重点是突触的形成。我们将研究megaRNP的蛋白质和mRNA组成，并确定megaRNP是多个或单个mRNA物种的集合。我们将在果蝇中使用分子遗传学工具来确定megaRNP组合物在转录本定位和正确的突触组装中的意义。我们还将确定核膜出芽和NPC依赖的mRNA输出模式之间的关系。最后，我们将开始分析哺乳动物细胞的核膜出芽途径。这些研究很可能是范式转移，我们的理解如何以及在哪里大RNP运输颗粒的形成，这是基本的理解如何实现精确的极化组装的细胞大分子复合物。此外，这些研究将阐明新的生物学途径，这几乎肯定会导致新的临床策略，用于治疗核纤层病，如Emery-Dreifuss肌营养不良症，运动障碍，如肌张力障碍和疱疹病毒型感染。

DESCRIPTION (provided by applicant): The long-term goal of this project is to characterize a novel pathway for the nuclear packaging and export of ultra-large ribonucleoprotein granules (megaRNPs) and its impact on synapse assembly. A long-standing tenet of cellular biology has been that all nucleo-cytoplasmic traffic takes place through the nuclear pore complex (NPC). Using the Drosophila neuromuscular junction (NMJ) as a model system, however, we recently uncovered an alternative pathway for the nuclear export of megaRNPs. This NPC- independent pathway has the potential to fundamentally change our understanding of nucleo-cytoplasmic communication. In this pathway, transcripts are packaged in megaRNPs within the nucleus and are exported to the cytoplasm by budding through nuclear envelope membranes in a process akin to the nuclear egress of Herpes-type viruses. The proposed project represents an incisive approach to understand the impact of this pathway on cellular biology, with a focus on synapse formation. We will investigate the protein and mRNA composition of megaRNPs, and determine if megaRNPs are assemblages of multiple or single mRNAs species. We will use molecular genetic tools in Drosophila to determine the significance of megaRNP composition in transcript localization and proper synapse assembly. We will also determine the relationship between nuclear envelope budding and NPC-dependent modes of mRNA export. Finally, we will begin an analysis of the nuclear envelope budding pathway in mammalian cells. These studies are likely to be paradigm-shifting for our understanding of how and where large RNP transport granules are formed, which is elemental to the understanding of how the precise polarized assembly of cellular macromolecular complexes is achieved. In addition, these studies will elucidate novel biological pathways that will almost certainly lead to new clinical strategies for the treatment of laminophathies such as Emery-Dreifuss muscular dystrophy, movement disorders such as dystonia, and Herpes virus-type infections.