Bursting Translation on Single mRNAs in Live Cells

Abstract

SummaryStochasticity has emerged as a mechanism to control gene expression. Much of this so-called “noise” has been attributed to bursting transcription. However, the stochasticity of translation has not similarly been investigated due to a lack of enabling imaging technologies. We developed techniques to track single mRNAs and their translation in live cells for hours, allowing measurement of previously uncharacterized translation dynamics. We applied genetic and pharmacological perturbations to control translation kinetics. Like transcription, translation is not a constitutive process but instead cycles between inactive and active states or “bursts”. But unlike transcription, which is largely frequency modulated, complex structure in the 5’-untranslated region alters burst amplitude. Bursting frequency can be controlled through cap-proximal sequences andtrans-acting factors such as eIF4F. We coupled single molecule imaging with stochastic modeling to deduce the fundamental kinetic parameters of translational bursting, a new dimension of translational control.HighlightsLong-term tracking of single mRNAs reveals multi-state, bursting translationStructure in the 5’-untranslated region modulates translational burst amplitude5’-cap proximal sequences modulate translational burst frequencymTOR signaling adjusts translation bursting to respond to environmental cues