Molecular and cellular characterization of SMN-mediated U7 snRNP assembly

描述（由申请人提供）：脊髓性肌萎缩症（SMA）是一种运动神经元疾病，目前尚无有效治疗方法。SMA是由进化上保守且普遍表达的运动神经元（SMN）存活蛋白水平降低引起的。SMN与其他几个核心蛋白一起形成大分子SMN复合物，在核糖核蛋白（RNPs）的组装中起作用。虽然SMN被认为可以组装多种RNPs，但迄今为止，其唯一明确的功能是组装剪接体小核核糖核蛋白（snRNPs）， snRNPs是真核mRNA剪接机制的关键组成部分。SMN依赖性RNA剪接途径的破坏尚未能够解释SMA的潜在疾病机制，这突出了鉴定SMN控制的其他途径的重要性。我们的初步工作确定了U7 snRNP（一种依赖于复制的组蛋白mrna的3'端加工所需的RNP因子）的组装在体内依赖于smn。由于SMN缺乏导致这一途径的破坏导致组蛋白合成的失调，对下游细胞过程具有潜在的有害影响。本研究项目旨在以这些发现为基础，确定SMN介导的U7 snRNP生物发生的关键RNA和蛋白质决定因素，以及确定由U7功能障碍引起的组蛋白合成改变是否有助于SMN缺乏引起的细胞表型，包括运动神经元存活。综上所述，该项目旨在表征SMA中被破坏的smn依赖性RNA通路，该通路可能具有有害的细胞后果，并在该疾病的病因学中具有重要意义。！ ！

DESCRIPTION (provided by applicant): Spinal muscular atrophy (SMA) is a motor neuron disease for which no effective treatment is currently available. SMA is caused by reduced levels of the evolutionarily conserved and ubiquitously expressed survival of motor neuron (SMN) protein. SMN together with several other core proteins forms the macromolecular SMN complex, which functions in the assembly of ribonucleoproteins (RNPs). While SMN is believed to assemble a variety of RNPs, to date its only well-characterized function is in the assembly of spliceosomal small nuclear ribonucleoproteins (snRNPs), critical components of the eukaryotic mRNA splicing machinery. Disruption of an SMN-dependent RNA splicing pathway has not yet been able to explain the underlying disease mechanisms in SMA, highlighting the significance of identifying additional pathways controlled by SMN. Our preliminary work identifies the assembly of the U7 snRNP - a RNP factor required for 3'-end processing of replication dependent histone mRNAs - as SMN-dependent in vivo. Disruption of this pathway due to SMN deficiency causes deregulation of histone synthesis with potentially detrimental effects on downstream cellular processes. This research project aims to build on these findings to identify the critical RNA and protein determinants of SMN-mediated U7 snRNP biogenesis, as well as to determine whether altered histone synthesis caused by U7 dysfunction contributes to cellular phenotypes caused by SMN deficiency, including motor neuron survival. Taken together, this project aims to characterize an SMN-dependent RNA pathway that is disrupted is SMA and may have deleterious cellular consequences with important implications in etiology of the disease. ! ! PUBLIC HEALTH RELEVANCE: Spinal muscular atrophy (SMA), a childhood neurodegenerative disease for which no effective treatment is currently available, is caused by a deficiency in the survival motor neuron (SMN) protein. To identify targets for effective SMA therapeutics, it is essential to characterize the fundamental biological pathways controlled by SMN. This project aims to characterize a novel SMN-dependent pathway that is disrupted in the disease in an effort to reveal novel disease mechanisms, which may provide new avenues for SMA therapeutic targeting.