Photoswitch nucleic acid catalytic activity by regulating topological structure with a universal supraphotoswitch

We demonstrated the generality of a strategy for photoswitching the activity of functional oligonucleotides by modulating their topological structure. Our strategy was proved to be versatile because it can be used to photoregulate functional oligonucleotides, e.g., ribozymes and DNAzymes, which have two binding arms and a catalytic loop. Repeated reversible photoregulation of RNA cleavage by a ribozyme or a DNAzyme was achieved by attaching two photoresponsive strands, artificial oligomers involving azobenzene moieties and nucleobases capable of forming a duplex as the supraphotoswitch. Individual strands were attached to the 3' and 5' ends of a RNA-cleavage oligonucleotide. Thus, the topological structure of the ribozyme or DNAzyme was constrained, and RNA cleavage was greatly suppressed when the supraphotoswitch duplex formed (OFF state). In contrast, RNA cleavage resumed when the supraphotoswitch duplex dissociated (ON state). Light irradiation was used to repeatedly switch the supraphotoswitch between the ON and OFF states so that RNA cleavage activity could be efficiently photoregulated. Analysis of the regulatory mechanism showed that topological constraints suppressed the RNA cleavage by causing both structural changes at the catalytic site and lower binding affinity between the RNA substrates and the functional oligonucleotides.