How do enhancers regulate transcription at a distance?

• A. Enhancers degrade RNA to reduce transcription.
• B. Enhancers are promoters.
• C. Enhancers only affect RNA stability, not transcription.
• D. Enhancers bind transcription factors and loop to promoters via mediator and coactivators to increase transcription.

Answer: (D)

Enhancers regulate transcription at a distance by serving as docking sites for transcription factors that, when bound, recruit mediator and other coactivators. These factors help form a loop in the DNA so the enhancer can come into contact with the promoter. This looping brings the enhancer-bound complex into proximity with the RNA polymerase II machinery at the promoter, boosting transcription. The mediator complex acts like a bridge, while coactivators can modify chromatin to a more open state, making transcription easier. Because looping can bring far-away elements into contact and the orientation of the enhancer isn’t fixed, enhancers can work from kilobases away and in various positions relative to the gene.

Other statements don’t fit because enhancers don’t degrade RNA, they aren’t promoters themselves, and their role is to enhance transcription—not to affect RNA stability directly.