title: Group I aptazymes as genetic regulatory switches.
abstract: BACKGROUND
  Allosteric ribozymes (aptazymes) that have extraordinary activation parameters have been generated in vitro by design and selection. For example, hammerhead and ligase ribozymes that are activated by small organic effectors and protein effectors have been selected from random sequence pools appended to extant ribozymes. Many ribozymes, especially self-splicing introns, are known control gene regulation or viral replication in vivo. We attempted to generate Group I self-splicing introns that were activated by a small organic effector, theophylline, and to show that such Group I aptazymes could mediate theophylline-dependent splicing in vivo.
  
  
  RESULTS
  By appending aptamers to the Group I self-splicing intron, we have generated a Group I aptazyme whose in vivo splicing is controlled by exogenously added small molecules. Substantial differences in gene regulation could be observed with compounds that differed by as little as a single methyl group. The effector-specificity of the Group I aptazyme could be rationally engineered for new effector molecules.
  
  
  CONCLUSIONS
  Group I aptazymes may find applications as genetic regulatory switches for generating conditional knockouts at the level of mRNA or for developing economically viable gene therapies.
authors.affiliation: Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA. kthompson@archemix.com
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Thompson
authors.forename: Heather A
authors.initials: HA
authors.lastname: Syrett
authors.forename: Scott M
authors.initials: SM
authors.lastname: Knudsen
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Ellington
mesh_terms: D000494:Allosteric Regulation / Q000235:genetics; D017122:Bacteriophage T4 / Q000201:enzymology / Q000235:genetics; D001483:Base Sequence / Q000235:genetics; D004789:Enzyme Activation / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics*; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012326:RNA Splicing / Q000235:genetics; D016337:RNA, Catalytic / Q000737:chemistry / Q000235:genetics*; D044563:RNA, Ribosomal, Self-Splicing / Q000737:chemistry / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D013379:Substrate Specificity / Q000235:genetics; D013940:Thymidylate Synthase / Q000235:genetics; D014764:Viral Proteins / Q000235:genetics
chemical_list: D016337:RNA, Catalytic; D044563:RNA, Ribosomal, Self-Splicing; D012367:RNA, Viral; D014764:Viral Proteins; D013940:Thymidylate Synthase