FIG. 2.

Activation of the BPS reporter by Tat-fused SF1/mBBP and Tat-fused U2AF65. (A) Titration of the Tat-fused SF1/mBBP expressor plasmid (filled circles) and unfused Tat (open circles) on the BPS reporter. Tat-expressing and BPS reporter plasmids were cotransfected into HeLa cells, and CAT activities were measured after 44 h. (Insets) CAT assays, with expressor plasmid amounts (nanograms) indicated. Fold activation was determined relative to the activity of the reporter alone. (B) Titration of the Tat-fused U2AF65 expressor plasmid (filled squares) and unfused Tat (open circles) on the BPS reporter. (C) Titration of the Tat-fused SF1/mBBP (filled circles), Tat-fused U2AF65 (filled squares), and unfused Tat (open circles) expressor plasmids on the HIV-1 TAR reporter. All fusions contain the RNA-binding domain of Tat and thus are able to activate transcription via the TAR element. Relative activities of the fusion proteins on the TAR reporter were used to normalize for fusion protein expression levels.