Fig. 5: The base of the double-helical stem is positioned above an RNB trihelix linker.
a,b, Comparison of RNA conformations near the trihelix linker in the hairpinA–GCU14 (a) and hairpinD–U7 structures (b). The seventh base from the 3′ end (U28 in hairpinA–GCU14 and U17 in hairpin–U7; yellow arrow) swings from interacting with the side chain of N663 (hairpinA–GCU14) to pointing towards R616 (hairpinD–U7), which stacks under C1. The trihelix linker forms the final barrier to the dsRNA before the tunnel to the active site. c, Overlay of the cryo-EM map of the HsDis3L2–hairpinD–U7 structure at the hairpin basal junction. d, Nucleotides U19–U23 are buried in the tunnel of the RNB.
