TFIID is a multimeric protein complex that plays a central role in mediating promoter responses to various activators and repressors. May play a role in helping to anchor Taf4 within the TFIID complex. May be involved in transducing signals from various transcriptional regulators to the RNA polymerase II transcription machinery. Belongs to the TFIID complex which is composed of TATA binding protein (Tbp) and a number of TBP-associated factors (Tafs). Interacts with Tbp and Taf4. Belongs to the WD repeat TAF5 family.