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. Author manuscript; available in PMC: 2012 Oct 22.
Published in final edited form as: Nat Rev Genet. 2010 May 5;11(6):439–446. doi: 10.1038/nrg2765

Figure 1. Chromatin domains and regulatory elements.

Figure 1

The relationships among silencers, enhancers, promoters and insulators are shown. Light blue circles represent nucleosomes and yellow ovals represent silencing proteins, such as heterochromatin protein 1 (HP1) and Sir3. Silencer elements (S) are sites of initiation of heterochromatin, which spreads and encompasses promoters (P2 in the diagram), silencing transcription. The I1 insulator functions to restrict the spread of heterochromatin. An enhancer (E1) that is present in an active chromatin domain flanked by insulators (I1 and I2) and that is bound by a transcription factor (TF) is able to communicate with a promoter (P1) in the same domain, whereas another enhancer (E2) is unable to communicate with promoter P1 because of an intervening insulator (I2).