Towards light‐induced control of gene expression using RNA

Abstract

The potential utility of catalytic RNAs and DNAs (ribozymes and deoxyribozymes, respectively) as reagents in molecular biology as well as therapeutic agents for a variety of human diseases, has long been recognized. Although naturally occurring RNA‐cleaving ribozymes are typically not subject to feedback control, rational methodologies for the creation of allosteric ribozymes, by functional combination of ribozyme and ligand‐responsive aptamer RNA elements, have existed for some years. I will describe the in vitro selection of RNA aptamers specific for binding one but not the other of two light‐induced isomers of a dihydrobenzo[e]pyrene “photochromic switch” compound, and the utilization of such an aptamer for the construction of the UG‐dihydropyrene ribozyme, an allosteric hammerhead ribozyme whose catalysis is controllable by irradiation with visible versus ultraviolet light. In the presence of micromolar concentrations of the photo‐switch compound, the ribozyme behaves as a two‐state switch, exhibiting a > 900‐fold difference in catalytic rates between the two irradiation regimes. I will then describe our efforts to use this RNA‐based system to control gene expression within yeast cells.