How do enhancers and silencers differ from promoter proximal elements, and how do chromatin structure and histone modifications influence access?

• A. Enhancers are always located immediately adjacent to promoters.
• B. Promoters recruit basal transcription machinery; enhancers and silencers act at a distance to up- or down-regulate transcription; chromatin state and histone modifications regulate access.
• C. Promoters are far away and do not recruit transcription factors.
• D. Chromatin structure has no effect on transcription.

Answer: (B)