TLN468 changes the pattern of tRNA used to readthrough premature termination codons in CFTR

Nonsense mutations account for 12 % of the cases of Cystic fibrosis (CF). The gene inactivation resulting from premature termination codon (PTC) can be counteracted by the use of drugs stimulating PTC readthrough, thereby restoring production of the full-length protein. We recently identified a new readthrough inducer named TLN468, acting more efficiently than gentamicin.Here, we measured readthrough induced by these two drugs on different cystic fibrosis transmembrane conductance regulator (CFTR) PTCs. Then we determined the amino acids inserted at theCFTRPTCs S1196X, G542X, W846X and E1418X during TLN468-mediated readthrough. Interestingly, TLN468 significantly promotes the incorporation of one specific amino acid at each stop codon, while gentamicin does not change the proportion of amino acids incorporated in basal conditions. Also, the function of the predicted recoded CFTR channels corresponding to these 4 PTCs was measured with or without potentiator. We found that, for some PTC, suppression induced by TLN468 treatment allows the expression of variants CFTR proteins with proper maturation and significant activity that can be potentiated by the presence of CFTR modulators.These results suggest that TLN468 PTC suppression in combination with CFTR modulators may be beneficial for the treatment of CF patients with PTCs.