Ligase-mediated synthesis of Cu II -responsive allosteric DNAzyme with bifacial 5-carboxyuracil nucleobases.

A Cu II -responsive allosteric DNAzyme has been developed by introducing bifacial 5-carboxyuracil (caU) nucleobases, which form both hydrogen-bonded caU-A and metal-mediated caU-Cu II -caU base pairs. The base sequence was logically designed based on a known RNA-cleaving DNAzyme so that the caU-modified DNAzyme (caU-DNAzyme) can form a catalytically inactive structure containing three caU-A base pairs and an active form with three caU-Cu II -caU pairs. The caU-DNAzyme was synthesized by joining short caU-containing fragments with a standard DNA ligase. The activity of caU-DNAzyme was suppressed without Cu II , but enhanced 21-fold with the addition of Cu II . Furthermore, the DNAzyme activity was turned on and off during the reaction by the addition and removal of Cu II ions. Both ligase-mediated synthesis and Cu II -dependent allosteric regulation were achieved by the bifacial base pairing properties of caU. This study provides a new strategy for designing stimuli-responsive DNA molecular systems.