(2'-5')-OLIGO-3'-DEOXYNUCLEOTIDES - SELECTIVE BINDING TO SINGLE-STRANDED RNA BUT NOT DNA

Oligodeoxynucleotides with (2'-5') internucleotide linkages have been synthesized on a solid support via standard cyanoethyl phosphoramidite chemistry, This simple change in the oligonucleotide bond connectivit y led to unique properties. UV melting temperature experiments indicat e that the (2'-5')-oligo-3'-deoxyadenylates, (2'-5')-3'-dA(8) and (2'- 5')-3'-dA(8)(s) phosphorothioate, hybridize selectively to single-stra nded RNA but not DNA, The complex (2'-5')-3'-dA(8):poly (U) (T-m = 32 degrees C) was nearly as stable as the natural (3'-5')-2'-dA(8) and po ly (U) (T-m = 33 degrees C) in 130 mM NaCl, and 10 mM phosphate buffer (pH 7.5), However, no association was observed upon mixing (2'-5')-3' -dA(8) and poly (dT). The (2'-5') linkages also confer greater resista nce to exo- and endonucleolytic degradation compared with (3'-5')-link ed oligomers. The rate of degradation of (2'-5')-3'-dA(8) was almost f our times less than that of (3'-5')-2'-dA(8) in cell culture medium co ntaining 10% heat-inactivated fetal calf serum. An increase in stabili ty for (2'-5')-3'-dA(8) against endonuclease activity was observed in both cytoplasmic and nuclear extracts. The nucleic acid selectivity of (2'-5')-oligo-3'-deoxynucleotides may represent an important design f eature to improve the efficacy of antisense oligonucleotides.