Control Elements

Control elements are non-coding DNA regions that regular transcription by RNA polymerase II. They come in two forms: enhancers and silencers.
Enhancers are a short region of DNA that can bind to proteins called activators. When such binding happens, transcription of a gene will be initiated. The gene can be some distance away from the enhancer, or even on a different chromosome. The increase in transcription is due to activators recruiting transcription factors, which enhances the binding of RNA polymerase.
A silencer is a DNA sequence capable of binding transcription regulation factors termed repressors. Upon binding, RNA polymerase is prevented from initiating transcription thus decreasing or fully suppressing RNA synthesis.