TAF(II)170 interacts with the concave surface of TATA-Binding protein to inhibit its DNA binding activity

The human RNA polymerase II transcription factor B-TFIID consists of TATA-b inding protein (TBP) and the TBP-associated factor (TAF) TAF(II)170 and can rapidly redistribute over promoter DNA. Here we report the identification of human TBP-binding regions in human TAF(II)170. We have defined the TBP i nteraction domain of TAF(II)170 within three amino-terminal regions: residu es 2 to 137, 290 to 381, and 380 to 460. Each region contains a pair of Hun tington-elongation-A subunit-Tor repeats and exhibits species-specific inte ractions with TBP family members. Remarkably, the altered-specificity TBP m utant (TBPAS) containing a triple mutation in the concave surface is defect ive for binding the TAF(II)170 amino-terminal region of residues 1 to 504. Furthermore, within this region the TAF(II)170 residues 290 to 381 can inhi bit the interaction between Drosophila TAF(II)230 (residues 2 to 81) and TB P through competition for the concave surface of TBP. Biochemical analyses of TBP binding to the TATA box indicated that TAF(II)170 region 290-381 inh ibits TBP-DNA complex formation. Importantly, the TBPAS mutant is less sens itive to TAF(II)170 inhibition. Collectively, our results support a mechani sm in which TAF(II)170 induces high-mobility DNA binding by TBP through rev ersible interactions with its concave DNA binding surface.