Abstract
We demonstrate the site-specific incorporation of nucleobase derivatives bearing fluorophores or affinity labels into a short RNA stem loop recognition motif by exchange of a guanine residue. The RNA-TAG (transglycosylation at guanosine) is carried out by a bacterial (E.coli) tRNA guanine transglycosylase (TGT), whose natural substrate is the nitrogenous base PreQ1. Remarkably, we have successfully incorporated large functional groups including biotin, BODIPY, thiazole orange, and Cy7 through a polyethylene glycol linker attached to the exocyclic amine of PreQ1. Larger RNAs, such as mRNA transcripts, can be site-specifically labeled if they possess the 17-nucleotide hairpin recognition motif. The RNA-TAG methodology could facilitate the detection and manipulation of RNA molecules by enabling the direct incorporation of functional artificial nucleobases using a simple hairpin recognition element