The Scripps Research Institute, Department of Neuroscience, Jupiter, FL, USA.
The Scripps Research Institute, Genomic Core, Jupiter, FL, USA.
Nat Commun. 2021 Mar 5;12(1):1461. doi: 10.1038/s41467-021-21637-y.
The polyglutamine expansion of huntingtin (mHTT) causes Huntington disease (HD) and neurodegeneration, but the mechanisms remain unclear. Here, we found that mHtt promotes ribosome stalling and suppresses protein synthesis in mouse HD striatal neuronal cells. Depletion of mHtt enhances protein synthesis and increases the speed of ribosomal translocation, while mHtt directly inhibits protein synthesis in vitro. Fmrp, a known regulator of ribosome stalling, is upregulated in HD, but its depletion has no discernible effect on protein synthesis or ribosome stalling in HD cells. We found interactions of ribosomal proteins and translating ribosomes with mHtt. High-resolution global ribosome footprint profiling (Ribo-Seq) and mRNA-Seq indicates a widespread shift in ribosome occupancy toward the 5' and 3' end and unique single-codon pauses on selected mRNA targets in HD cells, compared to controls. Thus, mHtt impedes ribosomal translocation during translation elongation, a mechanistic defect that can be exploited for HD therapeutics.
亨廷顿病（HD）是由亨廷顿蛋白（mHTT）的多聚谷氨酰胺扩展引起的神经退行性疾病，但具体机制尚不清楚。在这里，我们发现 mHtt 可促进核糖体停滞并抑制小鼠 HD 纹状体神经元细胞中的蛋白质合成。mHtt 的耗竭可增强蛋白质合成并增加核糖体易位的速度，而 mHtt 在体外可直接抑制蛋白质合成。Fmrp 是已知的核糖体停滞调节剂，在 HD 中上调，但它的耗竭对 HD 细胞中的蛋白质合成或核糖体停滞没有明显影响。我们发现核糖体蛋白和翻译核糖体与 mHtt 之间存在相互作用。高分辨率全局核糖体足迹分析（Ribo-Seq）和 mRNA-Seq 表明，与对照相比，HD 细胞中的核糖体占有率广泛向 5' 和 3' 端转移，并且在选定的 mRNA 靶标上存在独特的单密码子暂停。因此，mHtt 在翻译延伸过程中阻碍核糖体易位，这是一种可用于 HD 治疗的机制缺陷。
