Fluorescent RNA Tags for In Situ RNA Imaging in Living Cells

RNA imaging paves the way to investigate RNA function and regulation from the aspect of RNA subcellular localization and expression level. In the past decades, various highly precise and genetic coding fluorescent RNA, which can bind and light up the fluorophore by their specific sequence/structure, has been developed for RNA imaging, including Broccoli, Mango, SRB-2, RhoBAST, and Pepper et al. In this Review, we summarize the RNA imaging approaches and the progress made in the development of fluorescent RNA. Next, we emphasize the application of fluorescent RNA for in situ RNA imaging in living cells. Of particular note, besides the artificially selected fluorescent RNAs, a new kind of fluorophore that can bind and light up intrinsic RNA structure is described together for the first time. Finally, a summary of current strategies for designing fluorescent RNA and future perspectives are also presented. We hope this expanding topic will inspire the study of the architecture and functions of these fascinating molecular machinery in biological systems.