Communication over a large distance: enhancers and insulators.

Enhancers are regulatory DNA sequences that can work over a large distance. Efficient enhancer action over a distance clearly requires special mechanisms for facilitating communication between the enhancer and its target. While the chromatin looping model can explain the majority of the observations, some recent experimental findings suggest that a chromatin scanning mechanism is used to establish the loop. These new findings help to understand the mechanism of action of the elements that can prevent enhancer-promoter communication (insulators).