Department of Biochemistry, The University of Western Ontario, London, Ontario N6A 5C1, Canada.
Department of Anatomy & Cell Biology, The University of Western Ontario, London, Ontario N6A 5C1, Canada.
Nucleic Acids Res. 2021 Nov 18;49(20):11883-11899. doi: 10.1093/nar/gkab898.
In neurodegenerative diseases, including pathologies with well-known causative alleles, genetic factors that modify severity or age of onset are not entirely understood. We recently documented the unexpected prevalence of transfer RNA (tRNA) mutants in the human population, including variants that cause amino acid mis-incorporation. We hypothesized that a mistranslating tRNA will exacerbate toxicity and modify the molecular pathology of Huntington's disease-causing alleles. We characterized a tRNAPro mutant that mistranslates proline codons with alanine, and tRNASer mutants, including a tRNASerAGA G35A variant with a phenylalanine anticodon (tRNASerAAA) found in ∼2% of the population. The tRNAPro mutant caused synthetic toxicity with a deleterious huntingtin poly-glutamine (polyQ) allele in neuronal cells. The tRNASerAAA variant showed synthetic toxicity with proteasome inhibition but did not enhance toxicity of the huntingtin allele. Cells mistranslating phenylalanine or proline codons with serine had significantly reduced rates of protein synthesis. Mistranslating cells were slow but effective in forming insoluble polyQ aggregates, defective in protein and aggregate degradation, and resistant to the neuroprotective integrated stress response inhibitor (ISRIB). Our findings identify mistranslating tRNA variants as genetic factors that slow protein aggregation kinetics, inhibit aggregate clearance, and increase drug resistance in cellular models of neurodegenerative disease.
在神经退行性疾病中，包括具有明确致病等位基因的病理学，导致严重程度或发病年龄改变的遗传因素尚未完全被理解。我们最近发现，在人类中存在转移 RNA（tRNA）突变体的意外流行，包括导致氨基酸错误掺入的变体。我们假设，翻译错误的 tRNA 将加剧毒性并改变亨廷顿病致病等位基因的分子病理学。我们对一种翻译错误的 tRNAPro 突变体进行了特征分析，该突变体能将脯氨酸密码子错误翻译成丙氨酸，还分析了 tRNASer 突变体，包括一种 tRNASerAGA G35A 变体，其反密码子为苯丙氨酸（tRNASerAAA），在人群中约占 2%。tRNAPro 突变体能与神经元细胞中的有害亨廷顿聚谷氨酰胺（polyQ）等位基因产生合成毒性。tRNASerAAA 变体与蛋白酶体抑制物联合使用时具有合成毒性，但不会增强亨廷顿等位基因的毒性。翻译错误为丝氨酸的苯丙氨酸或脯氨酸密码子的细胞的蛋白质合成率显著降低。翻译错误的细胞形成不溶性 polyQ 聚集体的速度较慢，但效果较好，其蛋白质和聚集体降解存在缺陷，对神经保护综合应激反应抑制剂（ISRIB）具有抗性。我们的发现确定了翻译错误的 tRNA 变体作为遗传因素，可降低蛋白质聚集动力学速度、抑制聚集体清除，并增加神经退行性疾病细胞模型中的药物抗性。
