2′,5′-Oligoadenylate-peptide nucleic acids (2–5A-PNAs) activate RNase L

Abstract To potentiate the 2–5A (2′,5′-oligoadenylate)-antisense and peptide nucleic acid (PNA) approaches to regulation of gene expression, composite molecules were generated containing both 2–5A and PNA moieties. 2–5A-PNA adducts were synthesized using solid-phase techniques. Highly cross-linked polystyrene beads were functionalized with glycine tethered through a p -hydroxymethylbenzoic acid linker and the PNA domain of the chimeric oligonucleotide analogue was added by sequential elongation of the amino terminus with the monomethoxytrityl protected N -(2-aminoethyl)- N -(adenin-1-ylacetyl)glycinate. Transition to the 2–5A domain was accomplished by coupling of the PNA chain to dimethoxytrityl protected N -(2-hydroxyethyl)- N -(adenin-1-ylacetyl)glycinate. Finally, (2-cyanoethyl)- N,N -diisopropyl-4- O -(4,4-dimethoxytrityl)butylphosphoramidite and the corresponding (2-cyanoethyl)- N,N -diisopropylphosphoramidite of 5- O -(4,4′-dimethoxytrityl)-3- O -( tert -butyldimethylsilyl)- N 6 -benzoyladenosine were the synthons employed to add the 2 butanediol phosphate linkers and the four 2′,5′-linked riboadenylates. The 5′-phosphate moiety was introduced with 2-[[2-(4,4′-dimethoxytrityloxy)ethyl]sulfonyl]ethyl-(2-cyanoethyl)- N,N -diisopropylphosphoramidite. Deprotection with methanolic NH 3 and tetraethylammonium fluoride afforded the desired products, 2–5A-pnaA 4 , 2–5A-pnaA 8 and 2–5A-pnaA 12 . When evaluated for their ability to cause the degradation of two different RNA substrates by the 2–5A-dependent RNase L, these new 2–5A-PNA conjugates were found to be potent RNase L activators. The union of 2–5A and PNA presents fresh opportunities to explore the biological and therapeutic implications of these unique approaches to antisense.