Labelling and detecting 5‐formylpyrimidine is essential to understand its biological function. Herein, we describe a visible‐light triggered and catalyst‐free reaction in which 5‐formylcytidine RNA can be selectively labelled with 2‐thioaniline under the irradiation of a commercial blue LED light to generate fluorogenic 5‐(benzothiazol‐2‐yl) cytidine.magnified image

N 6 -Methyladenosine (m 6 A) represents ac ommon and highly dynamic modification in eukaryotic RNAt hat affects various cellular pathways. Natural dioxygenases such as FTOa nd ALKBH5 are enzymes that demethylate m 6 A residues in mRNA. Herein, the first identification of as mallmolecule modulator that functions as an artificial m 6 A demethylase is reported. Flavin mononucleotide (FMN), the metabolite produced by riboflavin kinase,mediates substantial photochemical demethylation of m 6 Ar esidues of RNAinl ive cells.T his study provides an ew perspective to the understanding of demethylation of m 6 Aresidues in mRNAand sheds light on the development of powerful small molecules as RNA demethylases and new probes for use in RNAb iology.