Site-specific labeling of RNA at internal ribose hydroxyl groups: Terbium-assisted deoxyribozymes at work

Abstract

A general and efficient single-step method was established for site-specific post-transcriptional labeling of RNA. Using Tb3+ as accelerating cofactor for deoxyribozymes, various labeled guanosines were site-specifically attached to 2′-OH groups of internal adenosines in in vitro transcribed RNA. The DNA-catalyzed 2′,5′-phosphodiester bond formation proceeded efficiently with fluorescent, spin-labeled, biotinylated, or cross-linker-modified guanosine triphosphates. The sequence context of the labeling site was systematically analyzed by mutating the nucleotides flanking the targeted adenosine. Labeling of adenosines in a purine-rich environment showed the fastest reactions and highest yields. Overall, practically useful yields >70% were obtained for 13 out of 16 possible nucleotide (nt) combinations. Using this approach, we demonstrate preparative labeling under mild conditions for up to ∼160-nt-long RNAs, including spliceosomal U6 small nuclear RNA and a cyclic-di-AMP binding riboswitch RNA. © 2014 American Chemical Society.