Establishing MS2-MCP-based single-molecule RNA visualization in Schizosaccharomyces pombe

Single-molecule RNA imaging using the MS2-MCP system has transformed the study of RNA biology across model organisms. However, this technology has remained unavailable for fission yeast (Schizosaccharomyces pombe), even though fission yeast is a central model for eukaryotic gene expression. Achieving single-molecule sensitivity requires identifying a narrow optimum where RNA labels are sufficiently bright while background fluorescence remains minimal. We have now accomplished this for S. pombe by systematically optimizing MCP expression and localization-screening a panel of constitutive S. pombe promoters and evaluating combinations of nuclear localization and export signals (NLSs and NESs). The resulting, successful constructs use tandem StayGold as the MCP fluorescent tag, taking advantage of its superior photostability. Together with optimized vectors for MS2 stem-loop tagging of endogenous transcripts, these tools enable single-molecule RNA imaging in fission yeast, opening the door to quantitative analyses of RNA dynamics in this core genetic model.