Genetically Encoded Sensor Enables Endogenous RNA Imaging with Conformation-Switching Induced Fluorogenic Proteins.

Genetically encoded molecular tools are crucial for live cell RNA imaging, and few are available for endogenous RNA imaging. We develop a new genetically encoded sensor using conformation switching RNA induced fluorogenic proteins that enable multicolor and signal-amplified imaging of endogenous RNAs. The sensor system is designed with an RNA sensing module and a degron-fused fluorescent protein reporter. Target RNA induces conformation switching of the RNA sensing module to form RNA aptamers that stabilize the degron-fused protein for fluorogenic imaging. This sensor is demonstrated for high-contrast imaging of survivin mRNA abundance and dynamics in live cells. Moreover, the sensor system is extended to a multicolor palette by screening fluorogenic proteins of distinct colors, and engineered into a signal amplifier using the split fluorescent protein design. The sensor is further exploited for imaging lncRNA MALAT-1 and its translocation dynamics during mitosis. Our sensor system can afford a valuable platform for RNA imaging in biomedical research and clinical theranostics.