How translation stops
Protein synthesis concludes when a ribosome encounters a stop codon in a transcript, which triggers the recruitment of highly conserved release factors to liberate the protein product. Lawson et al. used traditional biochemical methods and single-molecule fluorescence assays to track the interplay of release factors with ribosomes and reveal the molecular choreography of termination. They identified two distinct classes of effectors, small molecules and mRNA sequences, that directly inhibited the release factors and promoted stop codon readthrough. These findings may buttress ongoing efforts to treat diseases caused by premature stop codons, which cause 11% of all heritable human diseases.
Science, abi7801, this issue p. 876
Abstract
Translation termination, which liberates a nascent polypeptide from the ribosome specifically at stop codons, must occur accurately and rapidly. We established single-molecule fluorescence assays to track the dynamics of ribosomes and two requisite release factors (eRF1 and eRF3) throughout termination using an in vitro–reconstituted yeast translation system. We found that the two eukaryotic release factors bound together to recognize stop codons rapidly and elicit termination through a tightly regulated, multistep process that resembles transfer RNA selection during translation elongation. Because the release factors are conserved from yeast to humans, the molecular events that underlie yeast translation termination are likely broadly fundamental to eukaryotic protein synthesis.