Enhanceosome

The enhanceosome is a higher-order protein complex assembled at the enhancer and regulates expression of a target gene. The binding and assembly of the activating proteins is cooperative due to energetically favorable protein-protein interactions formed in the complex.
The best known example of the enhanceosome acts on the human interferon-beta gene, which is upregulated in cells that are infected by viruses. Three activator proteins—NF-κB, an interferon activator protein such as IRF-3, and the ATF-2/c-Jun complex—cooperatively bind to the upstream enhancer region upon viral infection. The interaction is mediated by a fourth protein HMG-I, which assists in stabilizing the complex by promoting inter-protein interactions. The assembled enhanceosome recruits transcriptional machinery such as RNA polymerase to the promoter region to initiate gene expression.