How do enhancers differ from proximal promoters in regulating transcription?

• A. Enhancers are distal regulatory elements that loop to promoters to boost transcription; proximal promoters are close to transcription start sites and recruit core transcription machinery.
• B. Enhancers recruit RNA polymerase directly; proximal promoters recruit DNA polymerase.
• C. Proximal promoters are distal; enhancers are near TSS.
• D. Enhancers replace promoters.

Answer: (A)

Enhancers enable regulation from a distance. They are distal regulatory elements that can lie far away from a gene and bind transcription factors that, through looping of the DNA, interact with the promoter to boost transcription. This looping brings the enhancer-bound activators into contact with the promoter-bound machinery, helping recruit or stabilize the transcriptional complex and increase gene expression. Proximal promoters, by contrast, sit close to the transcription start site and contain core promoter elements that recruit the general transcription factors and RNA polymerase II to assemble the preinitiation complex and start transcription. So enhancers modulate how much transcription occurs from a distance, while proximal promoters provide the site and machinery for initiating transcription. They don’t recruit RNA polymerase directly from afar, and they don’t replace promoters; they work through interactions with the promoter region to enhance transcription.