Figure 3: Model of transcriptional looping. The cohesion complex can loop either insulator, defined by CCCTC-binding factor (CTCF) binding, or enhancer elements bound by transcription factors. As can be seen, the intervening DNA sequence is “looped-out” to allow the enhancer/insulator and promoters to be brought into close physical proximity. In addition, the ability of an insulator to “block” the enhancer from interacting with its target promoter is illustrated. How the choice between which type of element, enhancer versus insulator, is utilized remains unknown.