Fig. 6: Model of progressive Rev binding on RRE SLII.

The closed and open RRE SLII exist in an equilibrium. The conformational changes between the closed and open SLII depict the first step in Rev oligomerization: recognition and binding of the high-affinity Rev-binding site. A single Rev molecule binds the open SLII conformer at the high-affinity binding site and induces a conformation change in the nearby major groove at stem-loop IIC. This allows a second Rev monomer to dimerize on the bound Rev molecule via interaction with stem IIC. The binding of additional Rev molecules continues to induce conformational changes at nearby sites on RRE until all Rev-binding sites are occupied.