Biogenesis of Small Ribonucleoproteins

描述（由申请人提供）：小核糖核蛋白（RNPs）是所有真核细胞的基本成分。作为剪接体的核心元件，小RNA是前信使RNA剪接所必需的。剪接的基本机制是相当清楚的，然而，执行这一过程的小核（sn）RNPs的生物发生相对不清楚。该建议的长期目标是了解控制snRNPs的生物发生和亚细胞定位的分子机制。简而言之，我们试图揭示snRNPs被包装、运输和传递到其作用位点的过程。snRNP生物发生的初始阶段开始于细胞质，随后snRNA转录物的核输出。组装成稳定的颗粒被认为是由运动神经元存活（SMN）蛋白复合物与蛋白质精氨酸甲基转移酶5 （PRMT5）复合物协同介导的。随后，这些小RNPs被输入细胞核。sm类小RNPs组装缺陷与脊髓性肌萎缩症（SMA）有关。SMA患者通常死于儿童早期。尽管snRNP生物发生在患者来源的细胞中受损，但SMA表型的根本原因尚不清楚。其他snRNP生物发生基因的突变可能导致SMA的表型。因此，对snRNP代谢的详细了解不仅对RNA加工的研究至关重要，而且对开发神经肌肉疾病的治疗也很重要。为了深入了解这些过程，我们开发了一个果蝇模型系统。该提案的具体目的是：(1)表征SMN复合物在snRNP生物发生和神经肌肉发育中的功能；(2)了解snRNA转运体PHAX在神经肌肉系统发育中的作用，并分析PHAX和SMN突变对snRNP功能的影响；(3)研究PRMT5复合物在一类潜在的新型sm - rnp生物发生中的活性。摘要：脊髓性肌萎缩症（SMA）是一种常见于幼儿的遗传性疾病；他们中的大多数不到两岁就死了。导致这种疾病的基因已经确定，但基因如何在细胞中起作用的潜在基础尚不清楚。为了最终开发出一种治疗方法，我们首先需要了解疾病基因及其伴侣基因的正常功能。

DESCRIPTION (provided by applicant): Small ribonucleoproteins (RNPs) are essential components of all eukaryotic cells. As the core elements of the spliceosome, small RNPs are required for pre-messenger RNA splicing. The basic mechanics of splicing are fairly well-understood, however, the biogenesis of the small nuclear (sn)RNPs that carry out this process is relatively unclear. The long-term goal of this proposal is to understand the molecular mechanisms that govern the biogenesis and subcellular localization of snRNPs. In short, we seek to uncover the process by which snRNPs are packaged, transported and delivered to their sites of action. The initial phases of snRNP biogenesis begin in the cytoplasm, following nuclear export of the snRNA transcript. Assembly into stable particles is thought to be mediated by the Survival of Motor Neurons (SMN) protein complex in collaboration with the Protein Arginine Methyltransferase 5 (PRMT5) complex. Subsequently, these small RNPs are imported back into the nucleus. Defects in the assembly of Sm-class small RNPs are associated with a disorder called Spinal Muscular Atrophy (SMA). Patients with SMA typically die in early childhood. Although snRNP biogenesis is compromised in patient-derived cells, the underlying cause of the SMA phenotype is not understood. Mutations in other snRNP biogenesis genes may phenocopy SMA. Thus a detailed understanding of snRNP metabolism is essential not only to the study of RNA processing, but will also be important in developing treatments for neuromuscular disease. To gain insight into these processes, we have developed a Drosophila model system. Specific Aims of this proposal are: (1) to characterize the function of the SMN complex in snRNP biogenesis and neuromuscular development, (2) to understand the role played by the snRNA transporter, PHAX, in development of the neuromuscular system and to assay the consequences of mutations in phax and smn on snRNP function, and (3) to investigate the activity of the PRMT5 complex in the biogenesis of a potentially novel class of Sm-RNPs. Lay Summary: Spinal Muscular Atrophy (SMA) is a common genetic disease that strikes young children; most of them die before reaching the age of two years. The gene responsible for this disease has been identified, but the underlying basis for how the gene functions in the cell is not known. To ultimately develop a treatment, we first need to understand the normal function(s) of the disease gene and its partner genes.