FIGURE 8.

Comparison with TAR RNA from HIV-1 and HIV-2. Sequences and secondary structures of HPI, HIV-1 TAR, and HIV-2 TAR. The Tat consensus binding motif is encircled. Bold nucleotides indicate the Tat binding motif. For HPI: Black arrows indicate that the nucleotide is involved in a stacking interaction; white arrows indicate that the residue is looped outside the helix and lines indicate that U41 and C75 are positioned into the major groove. Schematic representations of the Tat and Hexim binding site are shown. Solid and dotted horizontal lines indicate stable and weak base-pairings, respectively. Representations of HIV-1 TAR and HIV-2 TAR in the free form are based on structures from previous works (Aboul-ela et al. 1996; Long and Crothers 1999; Franck et al. 2009).