Final answer:
TFIID contains TBP as a subunit, with TBP being essential for the binding to the TATA box, leading to the recruitment of other transcription factors and RNA polymerase II for forming the initiation complex.
Step-by-step explanation:
The complex that contains TBP as a subunit is TFIID. TBP stands for TATA-binding protein, which is a crucial component of the TFIID complex. The function of TBP within TFIID is to bind to the TATA box within the core promoter region of genes that are transcribed by RNA polymerase II. This binding is essential for the recruitment of other transcription factors and the RNA polymerase II itself to form the transcription initiation complex. These transcription factors include TFIIB, TFIIE, TFIIF, and TFIIH, all of which play a key role in the stabilization of the pre-initiation complex and the initiation of transcription.