Feng, C. et al. Nat. Chem. Biol. https://doi.org/10.1038/nchembio.2548 (2018).
Hydroxyl radical probing remains the gold-standard approach for measuring RNA-nucleobase solvent accessibility, but it requires synchrotron radiation, and thus is challenging to apply in cells. Feng et al. now present light-activated structural examination of RNA, or LASER, a synchrotron-free alternative method for probing the solvent accessibility of purine nucleobases. The approach uses nicotinoyl azide, which, when hit with light, undergoes a rapid chemical reaction to form adducts with solvent-exposed guanosines and adenosines on a folded RNA. Such tagged sites are detected by reverse transcription of the modified RNA followed by denaturing gel electrophoresis. The method detects rapid changes in RNA structure after ligand binding and yields results very similar to those obtained by hydroxyl radical probing, but it works both outside and inside cells.