Topology and reorganization of a human TFIID–promoter complex

Abstract

TRANSCRIPTION factor TFIID is a multiprotein complex composed of a TATA-box-binding subunit, TBP, and several tightly associated factors (TAFs)1,2. Human TFIID–promoter interactions are restricted to the TATA-box region on most core promoters3,4 but extend over a large promoter region downstream of the TATA box and the transcription start site on the Ad2ML promoter3–6. TFIID downstream interactions are thought to be functionally relevant because they can be induced by transcriptional activators7–10, which in some cases requires TFIIA9,10, result in stabilization of the TFIID–promoter complex9,10, and correlate with increased recruitment of the remaining general transcription factors8,10. Here we examine the topological organization of human TFIID complexes bound to the Ad2ML promoter. Our data provide insight into the relative disposition of DNA and several TFIID subunits, as well as evidence for DNA wrapping by TFIID, and suggest a direct role of TFIIA in the stable positioning of promoter DNA relative to TAFs.