Figure 1.

Tat sequences representative of the five main HIV-1 subtypes. The sequence length of Tat is variable and ranges from 86 to 101 residues as a function of the second exon. A viable strain having only the first exon of Tat (72 residues) has never been observed in vivo. Subtype variability follows the geographical diversity of HIV-1 with subtype B Tat sequences being the most divergent compared to subtypes A, C, D and CRF_AE. These Tat variants have been synthesized using solid phase synthesis and have been shown to be able to cross membranes and trans-activate the HIV-1 LTR except for Tat Oyi [10,14-16,41,52].