Programming ADAR-recruiting hairpin RNA sensor to detect endogenous molecules.

RNA editing leveraging ADARs (adenosine deaminases acting on RNA) shows promising potential for in vivo biosensing beyond gene therapy. However, current ADAR sensors sense only a single target of RNA transcripts, thus limiting their use in different biosensing scenarios. Here, we report a hairpin RNA sensor that exploits new mechanisms to generate intramolecular duplex substrates for efficient ADAR recruitment and editing and apply it to detection of various intracellular molecules, including messenger RNA, small molecules and proteins. We utilize the base pairing interactions between neighbouring bases for enhanced stability, as well as the reverse effects to sense RNA transcripts and single-nucleotide variants with high sensitivity and specificity, irrespective of sequence requirement for complementarity to an UAG stop codon. In addition, we integrate RNA aptamers into the hairpin RNA sensor to realize the detection of the primary energy-supplying molecule, ATP, and a transcription factor, nuclear factor-kappa B (NF-κB), in live cells via a simple conformational change for programming the activation of hairpin RNA. This sensor not only broadens the detection of applicable molecules, but also offers potential for diverse cell manipulation.