Ribosome excursions during mRNA translocation mediate broad branching of frameshift pathways

Cell. 2015 Feb 26;160(5):870-881. doi: 10.1016/j.cell.2015.02.003. Epub 2015 Feb 19.


Programmed ribosomal frameshifting produces alternative proteins from a single transcript. -1 frameshifting occurs on Escherichia coli's dnaX mRNA containing a slippery sequence AAAAAAG and peripheral mRNA structural barriers. Here, we reveal hidden aspects of the frameshifting process, including its exact location on the mRNA and its timing within the translation cycle. Mass spectrometry of translated products shows that ribosomes enter the -1 frame from not one specific codon but various codons along the slippery sequence and slip by not just -1 but also -4 or +2 nucleotides. Single-ribosome translation trajectories detect distinctive codon-scale fluctuations in ribosome-mRNA displacement across the slippery sequence, representing multiple ribosomal translocation attempts during frameshifting. Flanking mRNA structural barriers mechanically stimulate the ribosome to undergo back-and-forth translocation excursions, broadly exploring reading frames. Both experiments reveal aborted translation around mutant slippery sequences, indicating that subsequent fidelity checks on newly adopted codon position base pairings lead to either resumed translation or early termination.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / genetics
  • Base Sequence
  • DNA Polymerase III / genetics
  • Escherichia coli / metabolism
  • Frameshift Mutation*
  • In Vitro Techniques
  • Mass Spectrometry
  • Molecular Sequence Data
  • Protein Biosynthesis*
  • RNA, Messenger / genetics*
  • Ribosomes / metabolism*


  • Bacterial Proteins
  • DnaX protein, Bacteria
  • RNA, Messenger
  • DNA Polymerase III