Tight translation regulation of the canonical C9ORF72 through a multi-component system

Haizel, S.; Ko, A. N.; Manning, L.; Ge, X.; Zou, H.; Cheng, R. C.; Widjaja, A.; Jean-Baptiste, J.; Khazhinsky, S.; Spealman, P.; Vogel, C.

doi:10.1101/2025.08.09.669471

bioRxiv · 10.1101/2025.08.09.669471

Tight translation regulation of the canonical C9ORF72 through a multi-component system

Haizel, S.·Ko, A. N.·Manning, L.·Ge, X.·Zou, H.·Cheng, R. C.·Widjaja, A.·Jean-Baptiste, J.·Khazhinsky, S.·Spealman, P.·Vogel, C.

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Abstract

C9ORF72 is involved in multiple neuronal functions and a major factor in Amyotrophic Lateral Sclerosis, a fatal neurodegenerative disease. Pathogenicity is implemented through an intronic repeat expansion in the genes mRNA leader that produces long, repetitive RNA and dipeptides when translated through a non-canonical mechanism. In contrast, despite the presence of ribosome-occupied, regulatory elements in the mRNA leader, nothing is known about C9ORF72 translation regulation under normal conditions. Surprisingly, when analyzing a series of mutants of the C9ORF72 mRNA leader, we found that translation of C9ORF72 is tightly regulated through a multi-layer system. First, non-canonical, multi-initiation upstream open reading frames (nc-uORFs) in all three frames, a start-stop element in frame 2, and a canonical uORF in frame 1work together to keep baseline C9ORF72 translation very low. Second, a strong secondary structure enhances these repressive elements, mainly the two nc-uORFs in frames 0 and 2. Finally, as initiation at the nc-uORFs reduces initiation at the downstream start-stop, the nc-uORFs effectively dampen the start-stops repressive function, forming a feedforward loop. We hypothesize that this buffered repressor system has likely evolved to ensure reliable, noise-insensitive expression of this critical regulator of neuronal function.

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Haizel, S., Ko, A. N., Manning, L., Ge, X., Zou, H., Cheng, R. C., Widjaja, A., Jean-Baptiste, J., Khazhinsky, S., Spealman, P., Vogel, C.. 2025-08-09. Tight translation regulation of the canonical C9ORF72 through a multi-component system. https://doi.org/10.1101/2025.08.09.669471

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