Single-molecule visualization of mRNA circularization during translation

Abstract

Protein synthesis: Seeing single mRNA moleculesSingle-molecule fluorescence imaging is revealing the formation of circular mRNA and the complex interplay of messenger RNA (mRNA) and ribosomal proteins during translation, the decoding of mRNA to form proteins. Various translation factors encourage the circularization of mRNA, which might help control mRNA expression, but detailed insights have been limited. Jong-Bong Lee at Pohang University of Science & Technology, South Korea, and co-workers reviewed recent progress in single-molecule imaging of mRNA circularization. Various fluorescence imaging methods have revealed the changing shapes, structures, locations and binding kinetics of mRNA molecules, as well as the quantities of important target proteins. The researchers highlight future challenges, such as simultaneously tracking multiple translation regulators, and improving protein purification and labeling. Such detailed single-molecule visualization could eventually enable scientists to directly manipulate interactions within mRNA-protein complexes. Translation is mediated by precisely orchestrated sequential interactions among translation initiation components, mRNA, and ribosomes. Biochemical, structural, and genetic techniques have revealed the fundamental mechanism that determines what occurs and when, where and in what order. Most mRNAs are circularized via the eIF4E-eIF4G-PABP interaction, which stabilizes mRNAs and enhances translation by recycling ribosomes. However, studies using single-molecule fluorescence imaging have allowed for the visualization of complex data that opposes the traditional "functional circularization" theory. Here, we briefly introduce single-molecule techniques applied to studies on mRNA circularization and describe the results of in vitro and live-cell imaging. Finally, we discuss relevant insights and questions gained from single-molecule research related to translation.