CRISPR-Cas9 Screens Identify the RNA Helicase DDX3X as a Repressor of C9ORF72 (GGGGCC)n Repeat-Associated Non-AUG Translation
CRISPR-Cas9 Screens Identify the RNA Helicase DDX3X as a Repressor of C9ORF72 (GGGGCC)n Repeat-Associated Non-AUG Translation
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DOI：
10.1016/j.neuron.2019.09.003
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发表时间：
2019-12-04
期刊：
影响因子：
16.2
通讯作者：
Sun, Shuying
中科院分区：
文献类型：
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作者：
Cheng, Weiwei;Wang, Shaopeng;Sun, Shuying
C9 ORF 72中的六核苷酸GGGGCC重复扩增是肌萎缩侧索硬化症（ALS）和额颞叶痴呆（FTD）的最常见遗传原因。一种致病机制是由扩增的RNA重复序列的非常规翻译产生的二肽重复序列（DPR）蛋白的异常积累。在这里，我们进行了全基因组CRISPR-Cas9筛选，以寻找人类细胞中DPR蛋白产生的修饰剂。我们发现，DDX 3X，RNA解旋酶，抑制重复相关的非AUG翻译GGGGCC重复。DDX 3X直接结合（GGGGCC）n RNA，但不结合反义（CCCCGG）n RNA。其解旋酶活性对于翻译抑制是必不可少的。DDX 3X的减少增加C9 ORF 72-ALS/FTD患者细胞中的DPR水平，并增强果蝇中（GGGGCC）n介导的毒性。DDX 3X表达升高足以降低DPR水平，挽救核质转运异常，并改善患者iPSC分化的神经元的存活。这项工作确定了DPR蛋白产生的遗传修饰剂，并为C9 ORF 72-ALS/FTD提供了潜在的治疗靶点。
Hexanucleotide GGGGCC repeat expansion in C9ORF72 is the most prevalent genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). One pathogenic mechanism is the aberrant accumulation of dipeptide repeat (DPR) proteins produced by the unconventional translation of expanded RNA repeats. Here, we performed genome-wide CRISPR-Cas9 screens for modifiers of DPR protein production in human cells. We found that DDX3X, an RNA helicase, suppresses the repeat-associated non-AUG translation of GGGGCC repeats. DDX3X directly binds to (GGGGCC)n RNAs but not antisense (CCCCGG)n RNAs. Its helicase activity is essential for the translation repression. Reduction of DDX3X increases DPR levels in C9ORF72-ALS/FTD patient cells and enhances (GGGGCC)n-mediated toxicity in Drosophila. Elevating DDX3X expression is sufficient to decrease DPR levels, rescue nucleocytoplasmic transport abnormalities, and improve survival of patient iPSC-differentiated neurons. This work identifies genetic modifiers of DPR protein production and provides potential therapeutic targets for C9ORF72-ALS/FTD.