ACTIVATION OF 2'-5'-OLIGOADENYLATE SYNTHETASE BY SINGLE-STRANDED AND DOUBLE-STRANDED-RNA APTAMERS

A number of small RNA molecules that are high affinity ligands for the 46-kDa form of human 2'-5' oligoadenylate synthetase have been identi fied by the SELEX method, Surface plasmon resonance analysis indicates that these RNAs bind to the enzyme with dissociation constants in the nanomolar range, Competition experiments indicate that the binding si te for the small RNAs on the 2'-5' oligoadenylate synthetase molecule at least partially overlaps that for the synthetic double-stranded RNA , poly(I). poly(C). Several of the RNAs function as potent activators of 2'-5' oligoadenylate synthetase in vitro, although there is no corr elation between binding affinity and ability to activate, The RNA apta mers having the strongest activation potential appear to have few base -paired regions. This suggests that 2'-5' oligoadenylate synthetase, w hich has previously been believed to be activated only by double-stran ded RNA, can also be activated by RNA ligands with little secondary st ructure, Since 2'-5' oligoadenylate synthetase possesses no homology t o other known RNA-binding proteins, the development of small specific ligands by SELEX should facilitate studies of RNA-protein interactions and may reveal novel features of the structure-function relationships involving this enzyme.