Dipartimento di Biologia e Biotecnologie "C Darwin", Sapienza University of Rome, Rome, Italy.
Istituto di Biologia e Patologia Molecolari (IBPM) del CNR, Rome, Italy.
PLoS Genet. 2020 May 26;16(5):e1008815. doi: 10.1371/journal.pgen.1008815. eCollection 2020 May.
Trimethylguanosine synthase 1 (TGS1) is a conserved enzyme that mediates formation of the trimethylguanosine cap on several RNAs, including snRNAs and telomerase RNA. Previous studies have shown that TGS1 binds the Survival Motor Neuron (SMN) protein, whose deficiency causes spinal muscular atrophy (SMA). Here, we analyzed the roles of the Drosophila orthologs of the human TGS1 and SMN genes. We show that the Drosophila TGS1 protein (dTgs1) physically interacts with all subunits of the Drosophila Smn complex (Smn, Gem2, Gem3, Gem4 and Gem5), and that a human TGS1 transgene rescues the mutant phenotype caused by dTgs1 loss. We demonstrate that both dTgs1 and Smn are required for viability of retinal progenitor cells and that downregulation of these genes leads to a reduced eye size. Importantly, overexpression of dTgs1 partially rescues the eye defects caused by Smn depletion, and vice versa. These results suggest that the Drosophila eye model can be exploited for screens aimed at the identification of genes and drugs that modify the phenotypes elicited by Tgs1 and Smn deficiency. These modifiers could help to understand the molecular mechanisms underlying SMA pathogenesis and devise new therapies for this genetic disease.
三甲基鸟苷合酶 1（TGS1）是一种保守的酶，可介导几种 RNA（包括 snRNA 和端粒酶 RNA）的三甲基鸟苷帽形成。先前的研究表明，TGS1 与生存运动神经元（SMN）蛋白结合，后者的缺乏会导致脊髓性肌萎缩症（SMA）。在这里，我们分析了人类 TGS1 和 SMN 基因的果蝇同源物的作用。我们表明，果蝇 TGS1 蛋白（dTgs1）与果蝇 Smn 复合物（Smn、Gem2、Gem3、Gem4 和 Gem5）的所有亚基都有物理相互作用，并且人类 TGS1 转基因可挽救由 dTgs1 缺失引起的突变表型。我们证明 dTgs1 和 Smn 都需要视网膜祖细胞的存活，并且这些基因的下调会导致眼睛变小。重要的是，dTgs1 的过表达部分挽救了 Smn 耗竭引起的眼睛缺陷，反之亦然。这些结果表明，果蝇眼睛模型可用于筛选旨在鉴定可修饰 Tgs1 和 Smn 缺乏引起的表型的基因和药物的筛选。这些修饰因子可以帮助我们理解 SMA 发病机制的分子机制，并为这种遗传疾病设计新的治疗方法。
