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. 2011 Jan 5;100(1):126–134. doi: 10.1016/j.bpj.2010.11.016

Figure 1.

Figure 1

Schemes of DNA looping. (a) Looping in a plasmid ring through the interaction between tandemly arranged insulatorlike elements, lacO, which confines enhancer E and promoter P in the same loop. (b) Looping in a linear DNA chain through the interaction between tandemly arranged insulatorlike elements, I, which does not confine either enhancer or promoter. (c) Looping in a plasmid ring. (d) Looping in a linear DNA chain. In a and b, the enhancer action is not blocked by looping (11–14), but in c and d, the enhancer is looped out and its activity can be blocked (14–17).