Halting on Transcripts: Analysis of Post-Initiation Translational Regulation by Ribosome Profiling

Abstract

The ability to regulate gene expression is a necessary function of the cell. There has been an increased focus in understanding translational control as research continues to show its importance in regulating protein levels. Regulation of translation primarily occurs during the initiation phase, as this step requires the most coordination of factors that can be targeted for regulation. There are, however, situations that necessitate the ability to quickly switch between translation and repression, which would be conferred once ribosomes are already in elongation. Early Drosophila development presents a good model system for studying such regulation, as mRNAs dumped from the nurse cells into the oocyte require immediate translational repression. Using ribosome profiling, we show that post-initiation translational regulation may be mediated by the halting of elongating ribosomes. Further, we identify a set of transcripts with putative ribosome halting for future study. Finally, we provide evidence for two molecular mechanisms for mediating the observed halting. Understanding ribosome halting will help shed light on the role of post-initiation translational regulation in the overall landscape of gene expression regulation.