ALTERED PROMOTER-BINDING OF THE TATA BOX-BINDING FACTOR-INDUCED BY THE TRANSCRIPTIONAL ACTIVATION DOMAIN OF VP16 AND SUPPRESSED BY TFIIA

The acidic transcriptional activation domain of the Herpes simplex vir us protein VP16 has been shown to bind directly to both the TATA box-b inding factor TBP and the general initiation factor TFIIB. Using DNase I footprinting assays, we have shown here that the VP16 activation do main qualitatively alters binding of Saccharomyces cerevisiae TBP to a TATA sequence in DNA. The effect of VP16 on promoter binding by TBP w as reduced by mutations in VP16 known to reduce transactivation and co uld not be overcome by increasing the amount of TBP used in the footpr inting assays. However, the association of yeast TFIIA with TBP on the promoter reversed the VP16-mediated effect and restored normal bindin g of TBP to the promoter. We suggest that VP16 induces a conformationa l change in TBP which alters its binding to promoter DNA, and that thi s effect of VP16 is suppressed by TFIIA.