Sequence-Selective 2′-<i>O</i>-Acetyl Modification of RNA Mediated by Duplex Formation with a Reactive Oligonucleotide Probe Incorporating 4-Thio-dT

We designed and synthesized an oligonucleotide acetylating reagent (Ac-probe) that selectively acetylates the 2'-OH groups of RNA upon forming a duplex with the target RNA. The Ac-probe can be readily prepared via a post-synthetic modification method using an oligodeoxynucleotide probe containing 4-thio-dT. During the acetylation reaction, 4-thio-dT is regenerated as the reaction proceeds. Notably, an efficient modification was observed when the complementary base of RNA to 4-thio-dT was cytosine or uracil, indicating the selectivity for the pyrimidine base.