Toehold-Mediated Strand Displacement in a Triplex Forming Nucleic Acid Clamp for Reversible Regulation of Polymerase Activity and Protein Expression.

Triplex forming oligonucleotides are used as a tool for gene regulation and in DNA nanotechnology. By incorporating artificial nucleic acids, target affinity and biological stability superior to that of natural DNA may be obtained. This work demonstrates how a chimeric clamp consisting of acyclic (L)-threoninol nucleic acid (aTNA) and DNA can bind DNA and RNA by the formation of a highly stable triplex structure. The (L)-aTNA clamp is released from the target again by the addition of a releasing strand in a strand displacement type of reaction. It is shown that the clamp efficiently inhibits Bsu and T7 RNA polymerase activity and that polymerase activity is reactivated by displacing the clamp. The clamp was successfully applied to the regulation of luciferase expression by reversible binding to the mRNA. When targeting a sequence in the double stranded plasmid, 40 % downregulation of protein expression is achieved.