Ribosomal translation machinery (80S ribosome and eukaryotic release factors eRF1 and eRF3)

The ribosomal translation machinery at CGA-derived nonsense codons refers to the assembly of the 80S ribosome and eukaryotic release factors (eRF1 and eRF3) at premature termination codons (PTCs) that originate from mutations in the CGA arginine codon. In the human genome, CGA is a hypermutable hot spot because it contains a CpG dinucleotide; deamination of the methylated cytosine frequently converts CGA to TGA (UGA in mRNA), making it the most common source of nonsense mutations in genetic diseases. When the translation machinery encounters such a PTC, it typically terminates protein synthesis, leading to truncated, nonfunctional proteins and triggering nonsense-mediated mRNA decay (NMD). This machinery is a critical therapeutic target for nonsense suppression (readthrough) agents like ataluren and aminoglycosides. These drugs bind to the ribosomal decoding center and reduce the stringency of codon recognition, allowing the insertion of a near-cognate amino acid at the PTC and enabling the production of full-length, functional proteins. This therapeutic strategy is being applied to various conditions, including Duchenne muscular dystrophy, cystic fibrosis, and cancers with nonsense mutations in tumor suppressor genes. Additionally, in certain organisms like Saccharomyces cerevisiae, the CGA codon itself can be misdecoded as a stop codon by this machinery, serving as a model for studying ribosome stalling and rescue pathways.

Other names

Translation termination complexNonsense suppression machineryRibosome-eRF1-eRF3 complexCGA-derived nonsense codon translation machineryRibosomal decoding centerPremature termination codon (PTC) readthrough machinery

Nonsense suppression or translational readthrough, where small molecules bind to the ribosomal decoding center (A-site) to decrease the fidelity of codon-anticodon pairing, allowing the insertion of a near-cognate aminoacyl-tRNA at a premature termination codon instead of recruiting release factors.