Talk abstracts
Talk on Friday 01:30-01:45pm submitted by Rachel Niederer
Direct analysis of ribosome targeting illuminates thousand-fold regulation of translation initiation by 5′ UTR elements
Rachel O. Niederer (Molecular Biophysics and Biochemistry, Yale University), Maria F. Rojas-Duran (Molecular Biophysics and Biochemistry, Yale University), Boris Zinshteyn (Panorama Medicine), Wendy V. Gilbert (Molecular Biophysics and Biochemistry, Yale University)
Abstract:
Translational control of gene expression plays an essential role in a wide range of cellular processes, ranging from stress responses to immune regulation. The protein output per mRNA is ultimately governed by a combination of cis elements and trans factors. However, the key mRNA features that distinguish efficiently translated from poorly translated mRNAs remain largely unknown. To elucidate the varied mechanisms by which translational control is achieved, we developed direct analysis of ribosome targeting (DART) and used it to dissect regulatory elements within 5′ untranslated regions (5′ UTRs). We find that 5′ UTRs confer thousand-fold differences in ribosome recruitment in vitro. Using DART, we identified novel translational enhancers and silencers and determined a functional role for most alternative 5′ UTR isoforms expressed in yeast. Our analysis revealed both anticipated and novel trends in the data. For example, engineered stems are generally inhibitory to recruitment at levels proportional to their folding strength. However, the effects are highly context-dependent with some strong stems apparently promoting recruitment in specific positions. Strikingly, we observed a strong global anticorrelation between %C and ribosome recruitment (Spearman R = -0.544) and found C-rich motifs over-represented among poorly recruiting TLs. The identified C-rich motifs are necessary and sufficient to repress translation both in vitro and in vivo. We also observe differential expression of 5′ UTR isoforms containing C-rich motifs in response to glucose starvation. This suggests these novel elements could be used to regulate translation of specific messages under different growth conditions. DART enables both the discovery of novel elements as well as systematic assessment of the translational regulatory potential of 5′ UTR variants, whether native or disease-associated, and will facilitate engineering of mRNAs for optimized protein production in various systems.
Keywords: Translational control, RNA structure, Translation initiation