Multiple roles of enhancers.

Enhancers (E) work in groups. They recruit PIC and TFs and interact with each other (1), which is associated with increased PolII concentration and production of eRNA. Enhancers subsequently deliver the PIC to a target promoter (P) through a looped structure (2). They control transcription elongation of some genes (e.g., by delivering an important kinase such as cdk9) by increasing the phosphorylation of PolII (3). They remove PcG repressive complexes from CpG islands of developmentally regulated genes through a histone demethylase (e.g., JMJD3) removing H3K27me3 (4).