Extended Data Fig. 5: The base of the double-helical stem is positioned above an RNB trihelix-linker.

a, The trihelix-linker forms the final barrier to the dsRNA before the tunnel to the active site. b, R616 on the junction of the trihelix stacks under C1 and points towards the first base of the 3′overhang (U17). c, Density for the RNB trihelix and linker.