Fluorescent Probes for Imaging Endogenous β-Actin mRNA in Living Cells Using Fluorescent Protein-Tagged Pumilio

Subcellular localization and dynamics of mRNAs control various physiological functions in living cells. A novel technique for visualizing endogenous mRNAs in living cells is necessary for investigation of the spatiotemporal movement of mRNAs. A pumilio homology domain of human pumilio 1 (PUM-HD) is a useful RNA binding protein as a tool for mRNA. recognition because the domain can be modified to bind a specific 8-base sequence of target mRNA. In this study, we designed PUM-HD to match the sequence of beta-actin mRNA and developed an mRNA probe consisting of two PUM-HD mutants flanking full-length enhanced green fluorescent protein (EGFP). Fluorescence microscopy with the probe in living cells revealed that the probe was labeled precisely with the beta-actin mRNA in cytosol. Fluorescent spots from the probe were colocalized with microtubules and moved directionally in living cells. The PUM-HD mutants conjugated with full-length EGFP can enable visualization of beta-actin mRNA localization and dynamics in living cells.