Transcription factor TFIID induces DNA bending upon binding to

The TATA box-binding factor TFIID plays a primary role in the process of transcription initiation by RNA polymerase II and its regulation by various gene-specific fac- tors. Here we employ a permuted binding site/gel retardation assay with recombinant yeast and human TFIID to show that this factor induces DNA bending around the TATA element. These results are consistent with the presence of G+C-rich sequence elements flanking the consensus TATA element and led to the recently confirmed suggestion that TFIID interacts with the TATA element via the minor groove. They also raise the possibility that TFIID-induced bending might facilitate promoter interactions of other general factors in the preiniti- ation complex or interactions between general transcription factors and regulatory factors bound at upstream sites. The general transcription initiation factor TFIID plays a key role in the activation and regulation of eukaryotic promoters. Binding of TFIID to the common TATA element initiates the assembly of a preinitiation complex involving RNA polymer- ase II and the other general initiation factors (1-3). Although any of the general factors are potential targets for the positive or negative action of regulatory factors, some of these factors have been found to interact directly with TFIID (4-8) or to facilitate TFIID interactions in functional assays (9-13). A unique role for TFIID in promoter activation and regulation was further suggested by the presence of novel structural motifs in the DNA-binding domain (14-18) and by the un- usual binding properties of TFIID, requiring high tempera- ture and characterized by slow on and off rates (4, 6, 19-21). This raises the possibility of coupled conformational changes in TFIID and the promoter. Prompted by these observations, we further investigated the TFIID-promoter interactions and report experiments showing that TFIID bends the promoter DNA around the TATA box.