HOLO TFIID SUPPORTS TRANSCRIPTIONAL STIMULATION BY DIVERSE ACTIVATORS AND FROM A TATA-LESS PROMOTER

Transcription factor IID (TFIID) binds to TATA boxes, nucleating the assembly of initiation complexes containing several general transcription factors and RNA polymerase II. Recently, TFIID was shown to be a multisubunit complex containing a TATA box-binding polypeptide (TBP) and several tightly associated polypeptides (TAFs), which are required for transcriptional stimulation by activator proteins. Here, we report the development of a human cell line expressing an epitope-tagged TBP and the immunopurification of a native, high-molecular-weight form of TFIID that supports transcriptional stimulation by several different classes of activation domains. Recovery of basal and activated TFIID transcriptional specific activity was close to approximately 100%. Electrophoretic mobility-shift analysis demonstrated a single major DNA-protein complex. This holo-TFIID contains TAFs of approximately 250, 125, 95, 78, and 50 kD and sediments at 17S. Holo-TFIID produced an extended footprint over the adenovirus major late promoter TATA box and initiator sequence and supported transcriptional activation from a promoter lacking a TATA box. These results lead us to hypothesize that a single multisubunit TFIID protein supports transcriptional stimulation by diverse activation domains and from a TATA-less promoter.