Abstract
Abnormal expansions of GGGGCC repeat sequence in the noncoding region of the C9orf72 gene is the most common cause of familial amyotrophic lateral sclerosis and frontotemporal dementia (C9-ALS/FTD). The expanded repeat sequence is translated into dipeptide repeat proteins (DPRs) by noncanonical repeat-associated non-AUG (RAN) translation. Since DPRs play central roles in the pathogenesis of C9-ALS/FTD, we here investigate the regulatory mechanisms of RAN translation, focusing on the effects of RNA-binding proteins (RBPs) targeting GGGGCC repeat RNAs. Using C9-ALS/FTD model flies, we demonstrated that the ALS/FTD-linked RBP FUS suppresses RAN translation and neurodegeneration in an RNA-binding activity-dependent manner. Moreover, we found that FUS directly binds to and modulates the G-quadruplex structure of GGGGCC repeat RNA as an RNA chaperone, resulting in the suppression of RAN translation in vitro. These results reveal a previously unrecognized regulatory mechanism of RAN translation by G-quadruplex-targeting RBPs, providing therapeutic insights for C9-ALS/FTD and other repeat expansion diseases.
Competing Interest Statement
Some of the authors previously belonged to the Department of Neurotherapeutics, Osaka University Graduate School of Medicine, that is an endowment department supported by Nihon Medi-Physics Co., AbbVie GK., Otsuka Pharm Co., Kyowakai Med. Co., Fujiikai Med. Co., Yukioka Hosp., Osaka Gyoumeikan Hosp., Kyorin Co., and Tokuyukai Med. Co.
Footnotes
We have performed a series of additional experiments, including in vitro translation assay using FUS-RRMmut protein (Figures 5F and 5G), and immunohistochemistry of fly larvae expressing (G4C2)89 and G-quadruplex-targeting RBPs (Figures 6E and 6F). Corresponding to these additional results, sections on introduction and results were updated. Other changes are as follows. Section on discussion updated to clarify the interpretations of RNA chaperones; Figures 1, 5, 6, 5-S1 revised; Figure 3-S1 added; Key resources tables added; Author orders updated.
