The TAFs of TFIID Bind and Rearrange the Topology of the TATA-Less RPS5 Promoter.

The general transcription factor TFIID is a core promoter selectivity factor that recognizes DNA sequence elements and nucleates the assembly of a pre-initiation complex (PIC). The mechanism by which TFIID recognizes the promoter is poorly understood. The TATA-box binding protein (TBP) is a subunit of the multi-protein TFIID complex believed to be key in this process. We reconstituted transcription from highly purified components on a ribosomal protein gene (RPS5) and discovered that TFIID Delta TBP binds and rearranges the promoter DNA topology independent of TBP. TFIID Delta TBP binds 200 bp of the promoter and changes the DNA topology to a larger extent than the nucleosome core particle. We show that TBP inhibits the DNA binding activities of TFIID Delta TBP and conclude that the complete TFIID complex may represent an auto-inhibited state. Furthermore, we show that the DNA binding activities of TFIID Delta TBP are required for assembly of a PIC poised to select the correct transcription start site (TSS).