ACE-tRNAs are a platform technology for suppressing nonsense mutations that cause cystic fibrosis

Nonsense mutations arise from single nucleotide substitutions that result in premature termination codons (PTCs). PTCs result in little to no full-length protein production and decreased mRNA stability due to the nonsense-mediated mRNA decay (NMD) pathway. We provide evidence that anticodon-edited (ACE-) tRNAs efficiently suppress the most prevalent cystic fibrosis (CF)-causing PTCs, promoting significant rescue of endogenous cystic fibrosis transmembrane conductance regulator (CFTR) transcript abundance and channel function in different model systems. We show that our best-performing ACE-tRNA, which decodes all UGA PTCs to a leucine amino acid, markedly rescues CFTR function from the most prevalent CF-causing PTCs, all of which arose from nonleucine encoding codons. Using this single ACE-tRNA variant, we demonstrate significant rescue of CFTR function in an immortalized airway cell line and two different primary CF patient-derived intestinal cell models with CFTR nonsense mutations. Further, we demonstrate that leucine substitution CFTR variants are highly functional. Thus, ACE-tRNAs have promise as a platform therapeutic for CF and other nonsense-associated diseases.