Ribosomal A-site UAG premature termination codon (PTC) (PTC)

The ribosomal A-site UAG premature termination codon (PTC) is a specialized therapeutic target within the ribosome–mRNA complex, primarily relevant in genetic diseases caused by nonsense mutations. In these conditions, a point mutation converts a sense codon into a UAG (amber) stop codon, leading to the premature cessation of translation and the production of truncated, non-functional proteins (Linde and Kerem, 2008, Trends in Genetics). The target specifically involves the interaction between the mRNA's UAG sequence and the ribosome's decoding center within the aminoacyl (A) site, where eukaryotic release factors (eRF1 and eRF3) normally bind to terminate protein synthesis. Drugs targeting this site, such as ataluren and the synthetic aminoglycoside ELX-02, aim to reduce the fidelity of the codon-anticodon interaction (Welch et al., 2007, Nature). This allows for "translational read-through," where a near-cognate tRNA is incorporated at the PTC, resulting in the synthesis of a full-length, functional protein. This approach is a form of precision medicine intended to treat the underlying cause of disorders like cystic fibrosis and Duchenne muscular dystrophy by restoring essential protein levels (Crawford et al., 2020, J Med Chem).

Other names

Amber premature stop codonUAG nonsense mutationRibosomal decoding center A-sitePremature termination codonNonsense-mediated decay substrate

Induction of translational read-through (nonsense suppression) by binding to the ribosomal decoding center and promoting the insertion of a near-cognate aminoacyl-tRNA at the UAG site instead of a release factor.