Which statement best describes how promoter elements interact with transcription factors in eukaryotes?

• A. Promoter elements alone recruit RNA Pol II without transcription factors.
• B. Promoter elements are recognized by RNA polymerase II directly, bypassing transcription factors.
• C. RNA polymerase II assembly is facilitated by general transcription factors and mediator that recognize promoter elements like the TATA box and initiator.
• D. Only bacterial sigma factors interact with promoter elements.

Answer: (C)

In eukaryotes, promoter elements act as docking sites for transcription factors, and those factors then recruit RNA polymerase II to form the transcription machinery. The best description is that RNA polymerase II assembly is facilitated by general transcription factors and the mediator complex, which recognize promoter elements like the TATA box and initiator.

Here's how it fits together: a promoter element such as the TATA box is bound by a general transcription factor complex (for example, TBP within TFIID binds the TATA box). Other general transcription factors (TFIIB, TFIIE, TFIIF, TFIIH) join to form the preinitiation complex, positioning RNA Pol II at the start site and preparing for RNA synthesis. The mediator acts as a bridge linking gene-specific transcription factors (which respond to cellular signals) to the core transcription machinery, helping to recruit Pol II and regulate initiation.

This is why the statement about direct recognition by RNA polymerase II without transcription factors isn’t correct—Pol II relies on those transcription factors and mediator to identify promoter elements and assemble the initiation complex. It’s also not correct to think bacterial sigma factors are involved in eukaryotic promoter recognition.