Universal initiator nucleotides for the enzymatic synthesis of 5′-amino- and 5′-thiol-modified RNA

We report the chemical synthesis of 5′-amino- and 5′-thiol-hexaethylene glycol guanosine nucleotides and their enzymatic incorporation into RNA, followed by chemical modifications at their nucleophilic ends. By using two similar routes, the conjugates of guanosine-5′-monophosphate and hexaethylene glycol with attached reactive groups (SH or NH2) were synthesized using phosphoramidite chemistry, and characterized by MALDI TOF mass spectrometry. These initiator molecules were efficiently incorporated into RNA at the 5′-end by run-off transcription using T7 RNA polymerase. The potential of these RNA conjugates for a broad reaction range with electrophiles is shown here, thereby enabling their use for diverse biochemical applications.