Improved Aptazyme Design and In Vivo Screening Enable Riboswitching in Bacteria

Switch-hitter: A new strategy to control gene expression relies on a ligand-dependent, ribozyme-based RNA switch. The key feature of this setup is that the ribozyme liberates the ribosome binding site upon cleavage of the message. The design made it possible to screen in vivo for an inducible aptazyme by attaching an aptamer to stem III of the ribozyme, thus preserving naturally occurring stem I/stem II contacts.