Phenylalanine-tRNA aminoacylation is compromised by ALS/FTD-associated C9orf72 C4G2 repeat RNA

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• The C9orf72 gene hexanucleotide repeat expansion is a primary genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD).
• A proposed disease mechanism involves repeat transcripts interfering with RNA-binding proteins, leading to cellular dysfunction.

Purpose of the Study:

• To identify interactors of the C9orf72 antisense repeat RNA in the cytosol.
• To investigate the functional consequences of this interaction on protein synthesis.

Main Methods:

• Identification of phenylalanine-tRNA synthetase (FARS) subunit alpha (FARSA) as a key interactor of the CCCCGG antisense repeat RNA.
• Assessing the impact of antisense RNA on tRNA^Phe aminoacylation by FARS.
• Analyzing global protein synthesis and expression of phenylalanine-rich proteins in cellular models and patient tissues.

Main Results:

• Antisense repeat RNA directly inhibits the aminoacylation activity of FARSA.
• This inhibition leads to decreased levels of charged tRNA^Phe.
• A global reduction in phenylalanine incorporation into proteins and decreased expression of phenylalanine-rich proteins were observed in cellular models and patient tissues.

Conclusions:

• The study reveals functional inhibition of FARSA by antisense C9orf72 repeat RNA.
• Impaired tRNA aminoacylation contributes to protein synthesis deficits.
• This mechanism offers new insights into the molecular pathology of C9orf72-associated ALS and FTD.