Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, United States.
Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, United States.
J Am Chem Soc. 2021 May 19;143(19):7368-7379. doi: 10.1021/jacs.1c00131. Epub 2021 Apr 15.
The expansion of a hexanucleotide repeat GGGGCC (G4C2) in the gene is the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The G4C2 expansion leads to repeat-associated non-AUG (RAN) translation and the production of toxic dipeptide repeat (DPR) proteins, but the mechanisms of RAN translation remain enigmatic. Here, we report that the RNA helicase DHX36 is a robust positive regulator of RAN translation. DHX36 has a high affinity for the G4C2 repeat RNA, preferentially binds to the repeat RNA's G-quadruplex conformation, and efficiently unwinds the G4C2 G-quadruplex structures. Native DHX36 interacts with the G4C2 repeat RNA and is essential for effective RAN translation in the cell. In induced pluripotent stem cells and differentiated motor neurons derived from C9orf72-linked ALS patients, reducing DHX36 significantly decreased the levels of endogenous DPR proteins. DHX36 is also aberrantly upregulated in tissues of -linked ALS patients. These results indicate that DHX36 facilitates RAN translation by resolving repeat RNA G-quadruplex structures and may be a potential target for therapeutic intervention.
在基因中 GGGGCC（G4C2）六核苷酸重复的扩展是肌萎缩侧索硬化症（ALS）和额颞叶痴呆（FTD）最常见的原因。G4C2 扩展导致重复相关的非 AUG（RAN）翻译和产生毒性二肽重复（DPR）蛋白，但 RAN 翻译的机制仍然神秘。在这里，我们报告 RNA 解旋酶 DHX36 是 RAN 翻译的强大正调节剂。DHX36 对 G4C2 重复 RNA 具有高亲和力，优先结合重复 RNA 的 G-四链体构象，并有效地解开 G4C2 G-四链体结构。天然 DHX36 与 G4C2 重复 RNA 相互作用，是细胞中有效 RAN 翻译所必需的。在源自 C9orf72 相关 ALS 患者的诱导多能干细胞和分化的运动神经元中，降低 DHX36 水平显著降低了内源性 DPR 蛋白的水平。DHX36 在 - 相关 ALS 患者的组织中也异常上调。这些结果表明，DHX36 通过解决重复 RNA G-四链体结构促进 RAN 翻译，可能是治疗干预的潜在靶点。
