Poster abstracts

Poster number 65 submitted by Michael Kearse

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

Michael G. Kearse (Department of Biological Chemistry & Pharmacology, Center for RNA Biology, The Ohio State University), Daniel H. Goldman (Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine), Aaron C. Goldstrohm (Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota), Peter K. Todd (Department of Neurology, University of Michigan), Rachel Green (Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine), Jeremy E. Wilusz (Department of Biochemistry and Biophysics, University of Pennsylvania Perelman School of Medicine)

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: translation, ribosome, inhibitor