A Role for Codon Order in Translation Dynamics

SummaryThe genetic code is degenerate. Each amino acid is encoded by up to six synonymous codons; the choice between these codons influences gene expression. Here, we show that in coding sequences, once a particular codon has been used, subsequent occurrences of the same amino acid do not use codons randomly, but favor codons that use the same tRNA. The effect is pronounced in rapidly induced genes, involves both frequent and rare codons and diminishes only slowly as a function of the distance between subsequent synonymous codons. Furthermore, we found that in S. cerevisiae codon correlation accelerates translation relative to the translation of synonymous yet anticorrelated sequences. The data suggest that tRNA diffusion away from the ribosome is slower than translation, and that some tRNA channeling takes place at the ribosome. They also establish that the dynamics of translation leave a significant signature at the level of the genome.

Graphical SummaryFigure optionsDownload high-quality image (157 K)Download as PowerPoint slideHighlights
► Successive codons for a given amino acid tend to employ the same tRNA
► This increases translation speed by allowing recycling of tRNA molecules
► Effect present in many organisms and across substantial distances between codons
► Predictive of rapid expression, suggests substantial tRNA channeling at the ribosome