In vitro selection of a ligase ribozyme carrying alkylamino groups in the side chains

A novel ligase ribozyme was in vitro selected from a random-sequence RNA li brary including N-6-aminohexyl-modified adenine residues in place of natura l adenine residues. This ribozyme mediated the formation of a phosphodieste r bond with a DNA oligonucleotide through condensation with a 5'-triphospha te moiety on the ribozyme. Among the clones isolated from this selection, o ne was shown to accelerate ligation about 250-fold compared to the original random-sequence RNA library. Almost no rate acceleration was observed when the N-6-aminohexyl-groups on adenine residues were omitted. Furthermore, l igation was dependent on the presence of a template DNA oligonucleotide tha t bridged the two strands.