title: In vitro selection of adenine-dependent hairpin ribozymes.
abstract: Adenine-dependent hairpin ribozymes were isolated by in vitro selection from a degenerated hairpin ribozyme population. Two new adenine-dependent ribozymes catalyze their own reversible cleavage in the presence of free adenine. Both aptamers have Mg(2+) requirements for adenine-assisted cleavage similar to the wild-type hairpin ribozyme. Cleavage kinetics studies in the presence of various other small molecules were compared. The data suggest that adenine does not induce RNA self-cleavage in the same manner for both aptamers. In addition, investigations of pH effects on catalytic rates show that both adenine-dependent aptamers are more active in basic conditions, suggesting that they use new acid/base catalytic strategies in which adenine could be involved directly. The discovery of hairpin ribozymes dependent on adenine for their reversible self-cleavage presents considerable biochemical and evolutionary interests because we show that RNA is able to use exogenous reactive molecules to enhance its own catalytic activity. Such a mechanism may have been a means by which the ribozymes of the RNA world enlarged their chemical repertoire.
authors.affiliation: Institut Jacques-Monod, Laboratoire de Biochimie de l'Evolution et Adaptabilité Moléculaire, Université Paris VI, Tour 43, 2 place Jussieu, 75251 Paris Cedex 05, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Meli
authors.forename: Jacques
authors.initials: J
authors.lastname: Vergne
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Maurel
mesh_terms: D000225:Adenine / Q000737:chemistry / Q000494:pharmacology*; D001483:Base Sequence; D002384:Catalysis; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D008274:Magnesium / Q000737:chemistry / Q000494:pharmacology; D008956:Models, Chemical; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D012313:RNA / Q000378:metabolism; D016337:RNA, Catalytic / Q000737:chemistry*; D013997:Time Factors
chemical_list: D008024:Ligands; D016337:RNA, Catalytic; D012313:RNA; D008274:Magnesium; D000225:Adenine