Enhancer (genetics)

An enhancer is a short region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur. These proteins are usually referred to as transcription factors. Enhancers can be located upstream, downstream, within an intron, or even thousands of base pairs away from the gene they regulate.

Function

Enhancers do not act on the promoter region itself, but are brought into proximity with the promoter by DNA looping. Once the enhancer is bound to its activator, the activator interacts with the mediator, a large protein complex that interacts with the RNA polymerase.

Identification

Enhancers can be identified by their histone modifications, such as H3K27ac and H3K4me1, and by the presence of the protein p300. They can also be identified by their sensitivity to DNase.

Role in disease

Mutations in enhancers have been linked to a variety of diseases, including cancer, autoimmune diseases, and neurodevelopmental disorders. For example, a mutation in an enhancer of the Sonic hedgehog gene has been linked to polydactyly, a condition characterized by extra fingers or toes.

See also

• Silencer (genetics)
• Regulatory sequence
• Transcription (genetics)

References

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  Diagram of a gene enhancer
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  Enhancer nucleotide sequence
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  Regulation of transcription in mammals