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.