A fast-acting reagent for accurate analysis of RNA secondary and tertiary structure by SHAPE chemistry.

Selective 2‘-hydroxyl acylation analyzed by primer extension (SHAPE) chemistry allows local nucleotide flexibility to be quantitatively assessed at single nucleotide resolution in any RNA. SHAPE chemistry exploits structure-based gating of the nucleophilic reactivity of the ribose 2‘-hydroxyl group by the extent to which a nucleotide is constrained or flexible. SHAPE chemistry was developed using N-methylisatoic anhydride (NMIA), which is only moderately electrophilic and requires tens of minutes to form ribose 2‘-O-adducts. Here, we design and evaluate a significantly more useful, fast-acting, reagent for SHAPE chemistry. Introduction of a nitro group para to the reactive carbonyl to form 1-methyl-7-nitroisatoic anhydride (1M7) yields a reagent that both reacts significantly more rapidly with RNA to form 2‘-O-adducts and is also more labile toward advantageous, self-limiting, hydrolysis. With 1M7, the single nucleotide resolution interrogation of the RNA structure is complete in 70 s. SHAPE analysis perf...