[RNA with polynucleotide kinase properties, isolated by in vitro selection]

Data on isolation from a large pool of RNAs of a fragment characterized by high-affinity ATP binding are reviewed. This ATP-binding domain flanking the regions of randomly sequenced nucleotide residues was used for preparation of an RNA pool, from which ribozymes displaying a polynucleotide kinase activity were isolated. The isolated ribozymes catalyzed the transfer of gamma-thiophosphate from ATP-gamma S to the 5' hydroxyl or to internal 2'-hydroxyls of their own chains. ATP was also used as a donor of phosphate; however, in this case the reaction rate was 55-300 times lower. Similarly to a true enzyme, one of these ribozymes shortened by 40 nucleotide residues at the 5' end repeatedly catalyzed the transfer of thiophosphate or phosphate to the 5' hydroxyl of an exogenous oligonucleotide.