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

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

Author information

1
Department of Biochemistry and Biophysics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104, USA.
2
Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
3
Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109, USA.
4
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA.
5
Veterans Affairs Medical Center, Ann Arbor, Michigan 48105, USA.

Abstract

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

PMID:
31171704
PMCID:
PMC6601509
[Available on 2020-01-01]
DOI:
10.1101/gad.324715.119
[Indexed for MEDLINE]

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