We previously solved the solution structure of the pseudoknot present in the overlapping region of gag and pol genes of Simian retrovirus type-1 (SRV-1) by NMR (26) . The structure has a classical H-type fold and is further characterized by interactions between the minor groove of stem 1 and loop 2, which forms a triple helix by various tertiary interactions and extensive stacking ( Figure 1A) .