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∆TBP binds and rearranges the promoter DNA topology independent of TBP. TFIID∆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∆TBP and conclude that the complete TFIID complex may represent an auto-inhibited state. Furthermore, we show that the DNA binding activities of TFIID∆TBP are required for assembly of a PIC poised to select the correct transcription start site (TSS).
- DNA topology
- Housekeeping gene transcription
- Ribosomal protein 5
- TAF complex
- TBP-associated factor