Final answer:
A complex of transcription factors, including TFIID, TFIIB, TFIIE, TFIIF, and TFIIH, must be assembled before RNA polymerase can bind and begin transcription.
Step-by-step explanation:
Before RNA polymerase can bind and begin transcription, a complex of transcription factors must be assembled. These transcription factors first bind to the promoter region of the DNA, particularly the TATA box. The assembly of these transcription factors, including TFIID, TFIIB, TFIIE, TFIIF, and TFIIH, recruits RNA polymerase to the promoter and creates the initiation complex.
Once this complex is formed, RNA polymerase can bind to its upstream sequence and initiate transcription.