Underwinding of DNA on binding of yeast TFIID to the TATA element.

The TATA box-binding factor TFIID is an essential component for the initiation of transcription by eukaryotic RNA polymerase II. We investigated the effect of DNA supercoiling on TFIID: promoter interactions using recombinant yeast (ry) TFIID. DNase I footprinting analysis showed that ryTFIID has a higher affinity for the adenovirus major late promoter in the negatively supercoiled state than that in the relaxed state. On the contrary, its affinity for the Drosophila hsp70 promoter is constant irrespective of DNA topology. Binding of ryTFIID to these promoters induced underwinding of duplex DNA. The functional TATA box and active ryTFIID are essential for the underwinding. The step was facilitated by negative supercoiling of DNA on the adenovirus major late promoter but not on the Drosophila hsp70 promoter.