Lee Kyung-Ha, Zhang Peipei, Kim Hong Joo, Mitrea Diana M, Sarkar Mohona, Freibaum Brian D, Cika Jaclyn, Coughlin Maura, Messing James, Molliex Amandine, Maxwell Brian A, Kim Nam Chul, Temirov Jamshid, Moore Jennifer, Kolaitis Regina-Maria, Shaw Timothy I, Bai Bing, Peng Junmin, Kriwacki Richard W, Taylor J Paul
Department of Cell and Molecular Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
Cell. 2016 Oct 20;167(3):774-788.e17. doi: 10.1016/j.cell.2016.10.002.
Expansion of a hexanucleotide repeat GGGGCC (GC) in C9ORF72 is the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Transcripts carrying (GC) expansions undergo unconventional, non-ATG-dependent translation, generating toxic dipeptide repeat (DPR) proteins thought to contribute to disease. Here, we identify the interactome of all DPRs and find that arginine-containing DPRs, polyGly-Arg (GR) and polyPro-Arg (PR), interact with RNA-binding proteins and proteins with low complexity sequence domains (LCDs) that often mediate the assembly of membrane-less organelles. Indeed, most GR/PR interactors are components of membrane-less organelles such as nucleoli, the nuclear pore complex and stress granules. Genetic analysis in Drosophila demonstrated the functional relevance of these interactions to DPR toxicity. Furthermore, we show that GR and PR altered phase separation of LCD-containing proteins, insinuating into their liquid assemblies and changing their material properties, resulting in perturbed dynamics and/or functions of multiple membrane-less organelles.
C9ORF72基因中六核苷酸重复序列GGGGCC（GC）的扩增是肌萎缩侧索硬化症（ALS）和额颞叶痴呆（FTD）最常见的病因。携带（GC）扩增的转录本会经历非常规的、非ATG依赖的翻译过程，产生有毒的二肽重复（DPR）蛋白，这些蛋白被认为与疾病的发生有关。在此，我们鉴定了所有DPR的相互作用组，发现含精氨酸的DPR，即聚甘氨酸-精氨酸（GR）和聚脯氨酸-精氨酸（PR），与RNA结合蛋白以及具有低复杂性序列结构域（LCD）的蛋白相互作用，这些蛋白通常介导无膜细胞器的组装。实际上，大多数GR/PR相互作用蛋白是无膜细胞器的组成部分，如核仁、核孔复合体和应激颗粒。果蝇中的遗传分析证明了这些相互作用与DPR毒性的功能相关性。此外，我们表明GR和PR改变了含LCD蛋白的相分离，潜入它们的液体组装体并改变其物质特性，导致多个无膜细胞器的动力学和/或功能受到干扰。
