What binds the TATA box in the transcription initiation process?

In the transcription initiation process, the TATA box, which is a conserved DNA sequence found in the promoter region of many genes, is specifically recognized and bound by TBP (TATA-binding protein), a subunit of the transcription factor complex TFIID. The role of TBP is crucial as it assists in the formation of the transcription pre-initiation complex by positioning the RNA polymerase and other transcription factors at the correct site on the DNA template.

The binding of TBP to the TATA box leads to the unwinding of the DNA, allowing access for other transcription factors and RNA polymerase to assemble at the promoter. This step is essential for the accurate initiation of transcription, making the interaction between TBP and the TATA box a key event in regulating gene expression.

Other options, while involved in the transcription process, do not directly bind the TATA box. For instance, the mediator complex functions as a bridge between various transcription factors and RNA polymerase II but does not have a direct role in interacting with the TATA box. TFIIB is a transcription factor that aids in the recognition of the transcription start site and recruitment of RNA polymerase II, but it acts after the TATA box has been bound by TBP.