Ribosome queuing enables non-AUG translation to be resistant to multiple protein synthesis inhibitors

Genes Dev. 2019 Jul 1;33(13-14):871-885. doi: 10.1101/gad.324715.119. Epub 2019 Jun 6.


Aberrant translation initiation at non-AUG start codons is associated with multiple cancers and neurodegenerative diseases. Nevertheless, how non-AUG translation may be regulated differently from canonical translation is poorly understood. Here, we used start codon-specific reporters and ribosome profiling to characterize how translation from non-AUG start codons responds to protein synthesis inhibitors in human cells. These analyses surprisingly revealed that translation of multiple non-AUG-encoded reporters and the endogenous GUG-encoded DAP5 (eIF4G2/p97) mRNA is resistant to cycloheximide (CHX), a translation inhibitor that severely slows but does not completely abrogate elongation. Our data suggest that slowly elongating ribosomes can lead to queuing/stacking of scanning preinitiation complexes (PICs), preferentially enhancing recognition of weak non-AUG start codons. Consistent with this model, limiting PIC formation or scanning sensitizes non-AUG translation to CHX. We further found that non-AUG translation is resistant to other inhibitors that target ribosomes within the coding sequence but not those targeting newly initiated ribosomes. Together, these data indicate that ribosome queuing enables mRNAs with poor initiation context-namely, those with non-AUG start codons-to be resistant to pharmacological translation inhibitors at concentrations that robustly inhibit global translation.

Keywords: RAN translation; cycloheximide; near-cognate; start codon; translation initiation; translational control.

Publication types

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

MeSH terms

  • Codon, Initiator / genetics*
  • Cycloheximide / pharmacology
  • Drug Resistance, Multiple / genetics*
  • Eukaryotic Initiation Factor-4G / genetics
  • Gene Expression Regulation / drug effects
  • Genes, Reporter / genetics
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Protein Synthesis Inhibitors / pharmacology
  • Ribosomes / genetics*
  • Transcription Elongation, Genetic / drug effects*


  • Codon, Initiator
  • EIF4G2 protein, human
  • Eukaryotic Initiation Factor-4G
  • Protein Synthesis Inhibitors
  • Cycloheximide