5'-Phosphonate modified oligoadenylates as potent activators of human RNase L

The oligoadenylate synthetase-ribonuclease L pathway is a major player in the interferon-induced antiviral defense mechanism of cells. Upon sensing viral dsRNA, 5'-phosphorylated 2',5'-oligoadenylates are synthesized, and subsequently activate latent RNase L. To determine the influence of 5'-phosphate end on the activation of human RNase L, four sets of 5'-phosphonate modified oligoadenylates were prepared on solid-phase. The ability of these 5'-modified oligoadenylates bearing shortened, isosteric and prolonged phosphonate linkages to activate RNase L was explored. We found that isosteric linkages and linkages prolonged by one atom were in general well tolerated by the enzyme with the EC₅₀ values comparable to that of the natural activator. In contrast, linkages shortened by one atom or prolonged by two atoms exhibited decrease in the activity.