DMA-Tudor interaction modules: a novel approach to Survival Motor Neuron protein (SMN) and Cajal body function

运动神经元存活蛋白（SMN）缺乏会导致脊髓性肌萎缩症（SMA），最常见的 婴儿和幼儿死亡的遗传原因。虽然SMN与转录有关，但RNA 尽管运动神经元的功能在加工和翻译过程中起着重要作用，但运动神经元丢失的分子基础仍然是未知的。我们最近发现了一个 SMN的新活性：由SMN的球状tudor结构域（SMNTud）引起的生物分子缩合， 结合由二甲基精氨酸（DMA）修饰的配体。尽管有数百种DMA修饰的蛋白质 在细胞中，Tudor结构域和它们的DMA配体之间的对应关系仍然未知。这 未充分研究的翻译后修饰是潜在的动态的，并且在多个方面具有新兴的作用。 神经系统疾病通过改变功能的细胞区室称为生物分子 冷凝物（BMC）。我们的中心假设是SMNTud与DMA配体的结合在细胞凋亡中起关键作用。 组织，这是特别脆弱的神经肌肉系统。 我们的研究结果强调了全面确定SMNTud的DMA配体及其活性的迫切需要。 它们所形成的交互模块。SMN呈弥漫性胞质分布，存在于称为Cajal的核BMC中 身体，这是胚胎发育所必需的。Cajal小体由已知的SMNTud配体支撑 并在SMA中改变。在应激期间，SMN在细胞质中形成BMC。我们的初步结果直接 表明SMA中DMA结合和生物分子缩合，因为SMNTud活性被 单一氨基酸突变E134 K，阻断与DMA配体的结合并导致SMA。化学抑制剂 DMA的显著改变了Cajal体的组成和亚结构，这是我们首次确定的。 与我们的合作者兼共同研究者Joerg Bewersdorf博士进行交流。完整的DMA配体的身份 结合SMNTud和影响Cajal体的蛋白质至今仍不清楚。我们的初步数据显示 ~70种新型和特异性SMNTud配体，表明我们掌握了与SMA相关的新见解。 该新申请的总体目标是（i）鉴定SMNTud的DMA配体，其介导 生物分子缩合，（ii）了解不对称（aDMA）和对称（sDMA）的动态性 由精氨酸甲基转移酶安装并由脱甲基酶去除， BMC的功能，以及（iii）通过利用DMA-SMNTud交互模块揭示新的SMN功能。我们 基本原理是，关于DMA-SMNTud交互模块的目标将最容易被严格的 使用小鼠和斑马鱼细胞，通过生物化学和最先进的成像相结合进行分析 和组织，包括运动神经元，我们有专业知识。如果实现了，我们的目标将是新颖的。 SMN结合配偶体和SMNTud在生物分子缩合中的功能。监管潜力和 将确定DMA修饰的动态性，组织特异性和疾病病因的来源。 DMA-SMNTud相互作用模块的鉴定将为SMA提供新的治疗方法。

Survival Motor Neuron protein (SMN) deficiencies cause Spinal Muscular Atrophy (SMA), the most common genetic cause of infant and toddler mortality. Although SMN has been implicated in transcription, RNA processing and translation, the molecular basis of motoneuron loss is still unknown. We recently discovered a novel activity of SMN: biomolecular condensation caused by SMN’s globular tudor domain (SMNTud), which binds ligands modified by dimethylarginine (DMA). Although there are hundreds of DMA-modified proteins in cells, the correspondence between tudor domains and their DMA ligands remains unknown. This understudied post-translational modification is potentially dynamic and has emerging roles in multiple neurological diseases through the altered functions of cellular compartments known as biomolecular condensates (BMCs). Our central hypothesis is SMNTud binding to DMA ligands plays critical roles in cellular organization, which are especially vulnerable in the neuromuscular system. Our findings highlight a critical need to comprehensively determine the DMA ligands of SMNTud and the activities of the interaction modules they form. SMN is diffusely cytoplasmic and present in nuclear BMCs called Cajal bodies, which are essential for embryonic development. Cajal bodies are scaffolded by a known SMNTud ligand and altered in SMA. During stress, SMN forms BMCs in the cytoplasm. Our preliminary results directly implicate DMA binding and biomolecular condensation in SMA, because SMNTud activity was blocked by a single amino acid mutation, E134K, that blocks binding to DMA ligands and causes SMA. Chemical inhibitors of DMA drastically altered the composition and substructure of Cajal bodies, which we determined for the first time with our collaborator and co-I, Dr Joerg Bewersdorf. The identities of the full complement of DMA ligands that bind SMNTud and those that affect Cajal bodies have been unknown until now. Our preliminary data reveal ~70 novel and specific SMNTud ligands, indicating that new insights relevant to SMA are within our grasp. The overall objectives of this new application are to (i) identify the DMA ligands of SMNTud that mediate biomolecular condensation, (ii) understand the dynamicity of asymmetric (aDMA) and symmetric (sDMA) installed by arginine methyltransferases and removed by demethylases with respect to the structure and function of BMCs, and (iii) reveal novel SMN functions by leveraging DMA-SMNTud interaction modules. Our rationale is that objectives concerning DMA-SMNTud interaction modules will be most accessible to rigorous analysis through a combination of biochemistry and state-of-the-art imaging, using mouse and zebrafish cells and tissues, including motoneurons, with which we have expertise. If achieved, our aims will discover novel SMN binding partners and functions of SMNTud in biomolecular condensation. The regulatory potential and dynamicity of the DMA modification, a source of tissue specificity and disease etiology, will be determined. Identification of DMA-SMNTud interaction modules will suggest new therapeutic approaches for SMA.