5’ stem-loop is unique regulatory element of type I collagen mRNAs which regulates their translation by binding protein LARP6. Drugs that can directly interact with the 5’ stem-loop RNA sequence and interfere with LARP6 recognition can be regarded as truly specific antifibrotic drugs. This invention is to enable screening for such drugs by designing two sensor 5’ stem-loop RNAs which can report drug or protein binding. The sensors are modified by incorporation of a fluorescent nucleotide analog at the critical position in the active site to report the change in fluorescence intensity upon protein or drug binding. Each sensor RNA has only one nucleotide replaced by a fluorescent analog, but they are at different positions in the two sensors so that the sensor RNAs can detect a change in molecular environment at the two positions within the LARP6 recognition site. By measuring the fluorescence intensity of sensors, protein or drug binding to the active site can be detected and quantified. The main application of the sensors is for high throughput screening of compounds that directly interact with 5’ stem-loop RNA, as hits for developing truly specific antifibrotic drugs.
