Which of the following best describes the relationship between activators and enhancers?

• A. Enhancers transcribe mRNA
• B. Promoters bind activators to start transcription
• C. Activators bind enhancers to increase transcription
• D. Repressors bind silencers to increase transcription

Answer: (C)

Activators are transcription factors that boost gene expression by binding to enhancer DNA sequences. Enhancers are regulatory elements that can be located far from the promoter; when an activator attaches to an enhancer, it helps recruit coactivators and the transcriptional machinery, often by looping the DNA so the enhancer–activator complex can interact with the promoter and increase transcription initiation. Enhancers themselves don’t transcribe mRNA. The promoter’s job is to recruit RNA polymerase and general transcription factors to start transcription, not to bind activators directly in the way described here. Repressors bind silencers to decrease transcription, not increase it. So the described relationship—activators binding enhancers to increase transcription—is the accurate one.