A new water soluble copper N-heterocyclic carbene complex delivers mild O6G-selective RNA alkylation

We show here that copper carbenes generated from diazo acetamides alkylate single RNAs, mRNAs, or pools of total transcriptome RNA, delivering exclusively alkylation at the O 6 position in guanine (O 6 G). Although the reaction is effective with free copper some RNA fragmentation occurs, a problem we resolve by developing a novel water-stable copper N-heterocyclic carbene complex. Carboxymethyl adducts at O 6 G are known mutagenic lesions in DNA but their relevance in RNA biochemistry is unknown. As a case-in-point we re-examine an old controversy regarding whether O 6 G damage in RNA is susceptible to direct RNA repair.