In vitro selection of adenine-dependent hairpin ribozymes |
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Authors: | Meli Marc Vergne Jacques Maurel Marie-Christine |
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Institution: | 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. |
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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. |
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