Figure 6.

PKR kinase activity inhibition assays with wild-type, AA4 and AU4 VA RNA_Is. Levels of PKR autophosphorylation were quantified after preincubation with various concentrations of each inhibitor VA RNA (0–10 μg/ml) and subsequent activation with poly(I)–poly(C) dsRNA. The partial mutant AA4, that lacks an unfolding transition (Figure 5C) that may correspond to Central Domain tertiary structure, shows reduced inhibitory activity while the compensatory mutant AU4 is as active as wild-type VA RNA_I.