Nuclease-resistant composite 2',5'-oligoadenylate-3', 5'-oligonucleotides for the targeted destruction of RNA: 2-5A-iso-antisense.

A new modification of 2-5A-antisense, 2-5A-iso-antisense, has been developed based on a reversal of the direction of the polarity of the antisense domain of a 2-5A-antisense composite nucleic acid. This modification was able to anneal with its target RNA as well as the parental 2-5A-antisense chimera. The 2-5A-iso-antisense oligonucleotide displayed enhanced resistance to degradation by 3'-exonuclease enzyme activity such as that represented by snake venom phosphodiesterase and by that found in human serum. 2-5A-Iso-antisense was able to effect the degradation of a synthetic nontargeted substrate, [5'-32P]pC11U2C7, and two targeted RNAs, PKR and BCR mRNAs, in a cell-free system containing purified recombinant human 2-5A-dependent RNase L. These results demonstrated that the novel structural modification represented by 2-5A-iso-antisense provided a stabilized biologically active formulation of the 2-5A-antisense strategy.