Insights into genome recoding from the mechanism of a classic+1-frameshifting tRNA

While genome recoding using quadruplet codons to incorporate non-proteinogenic amino acids is attractive for biotechnology and bioengineering purposes, the mechanism through which such codons are translated is poorly understood. Here we investigate translation of quadruplet codons by a +1-frameshifting tRNA, SufB2, that contains an extra nucleotide in its anticodon loop. Natural post-transcriptional modification of SufB2 in cells prevents it from frameshifting using a quadruplet-pairing mechanism such that it preferentially employs a triplet-slippage mechanism. We show that SufB2 uses triplet anticodon-codon pairing in the 0-frame to initially decode the quadruplet codon, but subsequently shifts to the +1-frame during tRNA-mRNA translocation. SufB2 frameshifting involves perturbation of an essential ribosome conformational change that facilitates tRNA-mRNA movements at a late stage of the translocation reaction. Our results provide a molecular mechanism for SufB2-induced +1 frameshifting and suggest that engineering of a specific ribosome conformational change can improve the efficiency of genome recoding.

Automated summary

The study investigates the translation of quadruplet codons by a +1-frameshifting tRNA SufB2, revealing that SufB2 initially uses triplet anticodon-codon pairing in the 0-frame to decode the quadruplet codon before shifting to the +1-frame during tRNA-mRNA translocation. The frameshifting mechanism of SufB2 involves perturbation of a crucial ribosome conformational change, highlighting the potential for engineering specific ribosome conformational changes to enhance genome recoding efficiency.