Molecular and cellular characterization of SMN-mediated U7 snRNP assembly

描述(申请人提供)：脊髓性肌萎缩症(SMA)是一种运动神经元疾病，目前还没有有效的治疗方法。SMA是由于运动神经元存活蛋白(SMN)在进化上保守且普遍表达的水平降低所致。SMN与其他几种核心蛋白一起形成大分子SMN复合体，它在核糖核蛋白(RNP)的组装中发挥作用。虽然SMN被认为可以组装各种RNPs，但到目前为止，它唯一被很好描述的功能是组装剪接体小核核糖核蛋白(SnRNPs)，这是真核mRNA剪接机制的关键组成部分。SMN依赖的RNA剪接途径的中断还不能解释SMA的潜在疾病机制，这突显了确定其他由SMN控制的途径的重要性。我们的初步工作发现，U7 SnRNP的组装--一种复制依赖的组蛋白mRNAs的3‘端处理所需的RNP因子--在体内是SMN依赖的。由于SMN缺乏导致这一途径的中断会导致组蛋白合成的放松调控，从而对下游细胞过程产生潜在的有害影响。本研究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，该项目旨在表征一种SMN依赖的RNA途径，该途径被破坏，并可能具有有害的细胞后果，在该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. ! !