Drug-induced eRF1 degradation promotes readthrough and reveals a new branch of ribosome quality control

Suppression of premature termination codons (PTCs) by translational readthrough is a promising strategy to treat a wide variety of severe genetic diseases caused by nonsense mutations. Here, we present two potent readthrough promoters—NVS1.1 and NVS2.1—that restore substantial levels of functional full-length CFTR and IDUA proteins in disease models for cystic fibrosis and Hurler syndrome, respectively. In contrast to other readthrough promoters that affect stop codon decoding, the NVS compounds stimulate PTC suppression by triggering rapid proteasomal degradation of the translation termination factor eRF1. Our results show that this occurs by trapping eRF1 in the terminating ribosome, causing ribosome stalls and subsequent ribosome collisions, and activating a branch of the ribosome-associated quality control network, which involves the translational stress sensor GCN1 and the catalytic activity of the E3 ubiquitin ligases RNF14 and RNF25. [Display omitted] •NVS1.1 and NVS2.1 restore CFTR and IDUA activity in CF and Hurler disease models•The drugs induce proteasomal eRF1 degradation and readthrough of PTCs•And block translation termination by trapping eRF1 in the A site, causing ribosome collisions•GCN1, RNF14, and RNF25 sense occluded A sites and degrade the trapped eRF1 Gurzeler et al. present two potent readthrough promoters, NVS1.1 and NVS2.1, that restore functional full-length proteins in cystic fibrosis and Hurler disease models. These compounds promote readthrough of premature termination codons by triggering eRF1 degradation by a ribosome-associated quality control pathway involving GCN1, RNF14, and RNF25.