Explain how transcription factors and enhancers influence gene expression.

• A. Promoters alone recruit RNA polymerase with no other factors.
• B. Enhancers repress transcription.
• C. Transcription factors bind promoter/enhancer elements; enhancers can loop to promoters to increase transcription, whereas promoters alone recruit RNA polymerase with help of factors.
• D. Transcription factors do not influence promoter activity.

Answer: (C)

Transcription factors are proteins that recognize and bind specific DNA sequences at promoter and enhancer regions to regulate where, when, and how much a gene is transcribed. When activator transcription factors bind to an enhancer, they recruit coactivators and chromatin remodelers and help bring the enhancer into close physical contact with the promoter through DNA looping. This looping allows the activator-bound enhancer to interact with the transcription machinery at the promoter, boosting the assembly of RNA polymerase II and the general transcription factors, which increases transcription.

The promoter is the site where RNA polymerase II starts, but it does not work in isolation. It requires transcription factors and coactivators to recruit RNA polymerase II and form the initiation complex. Enhancers add another layer of control by increasing transcription levels in response to cellular signals or developmental cues, often from locations far away on the DNA.

This explanation aligns with the idea that transcription factors bind promoter/enhancer elements, enhancers can loop to promoters to increase transcription, and promoters depend on factors to recruit RNA polymerase, rather than working alone.