Figure 4.

Tat–SF1 is required for transcription activity by Tat. Affinity chromatography was performed as described in Fig. 1. (A) The nuclear extract input and the FT fractions from the Tat protein-affinity column and the control column were tested in a Tat-transactivation assay as shown schematically. (B) The 0.5 m eluate from the Tat protein-affinity column (0, 5, or 10 μl) was tested for complementation of the Tat protein-affinity column FT for activation by Tat. (C) The same as B except that TFIIF (2 μl) and Tat–SF1 (2, 4 μl) from the Mono S column were added.