Core modified 8–17 DNAzymes with 2′-deoxy-2′-C-methylpyrimidine nucleosides

Abstract

The catalytic core of an 8–17 DNAzyme directed against STAT 3 was modified using (2′R) and (2′S) 2′-deoxy-2′-C-methyluridine and cytidine. While 2′-deoxy-2′-C-methyluridine significantly diminished the catalytic activity, 2′-deoxy-2′-C-methylcytidine replacement was better accepted, being the kact of modified DNAzymes at 8- and 11-positions comparable to the non-modified one. When 2′-O-methyl and phosphorothioate nucleotides were tested in the binding arms together with core modified DNAzymes the kcat was affected in a non predictable way, emphasizing the fact that both chemical substitutions should be considered globally. Finally, 2′-deoxy-2′-C-methyl modified DNAzymes stability was assayed finding that the double 2′-C-methyl modification in the catalytic core enhanced 70% the stability against a T47D cell lysate compared to a non-modified control.