What is a promoter-proximal element?

• A. An element that signals RNA processing.
• B. The transcription start site itself.
• C. Regulatory sequences near the promoter that modulate transcription efficiency and rate.
• D. A sequence that terminates transcription.

Answer: (C)

Promoter-proximal elements are regulatory DNA sequences located near the promoter that help control how strongly a gene is transcribed. They sit just upstream of the transcription start site, usually within a few hundred base pairs, and bind transcription factors that boost RNA polymerase II recruitment and promoter clearance. By influencing how efficiently transcription is initiated, they modulate the overall transcription rate and gene expression level. They’re distinct from the transcription start site itself, RNA processing signals, or termination signals, which explains why the description of regulatory sequences near the promoter that modulate transcription efficiency and rate is the best fit.