CAS Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic Molecular Physics, National Center for Magnetic Resonance at Wuhan, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, Hubei 430071, China.
Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics-Huazhong University of Science and Technology, Wuhan, Hubei 430074, China.
J Am Chem Soc. 2022 Mar 23;144(11):4716-4720. doi: 10.1021/jacs.1c12085. Epub 2022 Feb 18.
RNA molecules with repeat expansion sequences can phase separate into gel-like condensate, which could lead to neurodegenerative diseases. Here, we report that, in the presence of Mg, RNA molecules containing 20× CAG repeats self-assemble into three morphologically distinct droplets. Using hyperspectral stimulated Raman microscopy, we show that RNA phase separation is accompanied by the clustering of nucleobases while forfeiting the canonical base-paired structure. As the RNA/Mg ratio increases, the RNA droplets first expand and then shrink to adopt hollow vesicle-like structures. Significantly, for both large and vesicle-like RNA droplets, the nucleobase-clustered structure is more prominent at the rim, suggesting a continuously hardening process. This mechanism may be implicated in the general aging processes of RNA-containing membrane-less organelles.
具有重复扩展序列的 RNA 分子可以相分离成凝胶状的凝聚物，这可能导致神经退行性疾病。在这里，我们报告说，在镁的存在下，含有 20×CAG 重复的 RNA 分子自组装成三种形态上明显不同的液滴。使用高光谱受激拉曼显微镜，我们表明 RNA 相分离伴随着核碱基的聚集，同时放弃了典型的碱基配对结构。随着 RNA/Mg 比的增加，RNA 液滴首先膨胀，然后收缩以采用空心囊泡样结构。重要的是，对于大的和囊泡样的 RNA 液滴，核碱基聚集结构在边缘处更为明显，这表明存在一个不断硬化的过程。这种机制可能与包含无膜细胞器的 RNA 的一般老化过程有关。
