FIG. 3.

Activation by the Tat fusion proteins requires RNA-protein interactions at the BPS, PPT, and AG dinucleotide. (A) Activation of the BPS reporter and mutants by Tat-fused SF1/mBBP (gray bars) and Tat-fused SF1/mBBPΔN (white bars). Tat-expressing (5 ng) and BPS reporter (100 ng) plasmids were cotransfected into HeLa cells, and CAT activities were measured after 44 h. Percent activation was calculated by normalizing to the activation level of the Tat-fused SF1/mBBP-BPS reporter interaction, and standard deviations (bars) were calculated as described in Materials and Methods. (B) Activation of the BPS reporter and mutants by Tat-fused U2AF65 (gray bars) and Tat-fused U2AF65Δ95-138 (white bars). Activities were normalized to the activation level of the Tat-fused U2AF65-BPS reporter interaction.