Synthetic RNA circuits.

Natural and engineered RNA 'parts' can perform a variety of functions, including hybridizing to targets, binding ligands and undergoing programmed conformational changes, and catalyzing reactions. These RNA parts can in turn be assembled into synthetic genetic circuits that regulate gene expression by acting either in cis or in trans on mRNAs. As more parts are discovered and engineered, it should be increasingly possible to create synthetic RNA circuits that are able to carry out complex logical operations in cells, either superimposed on or autonomous to extant gene regulation.