RNA-CATALYZED RNA POLYMERIZATION USING NUCLEOSIDE TRIPHOSPHATES

THE hypothesis that certain RNA molecules may be able to catalyse RNA replication is central to current theories of the early evolution of l ife(1-6). In support of this idea, we describe here an RNA that synthe sizes RNA using the same reaction as that employed by protein enzymes that catalyse RNA polymerization. In the presence of the appropriate t emplate RNA and nucleoside triphosphates, the ribozyme extends an RNA primer by successive addition of up to six mononucleotides. The added nucleotides are joined to the growing RNA chain by 3',5'-phosphodieste r linkages. The ribozyme shows marked template fidelity: extension by nucleotides complementary to the template is up to 1,000 times more ef ficient than is extension by mismatched nucleotides.