Biochemistry, molecular genetics, and biology glossary terms for Companion Sites.


An enhancer is a short DNA sequence that increases the level of expression of another gene. Specific trans-acting, transcription factors bind to the enhancer to bring about the increase in transcription rate – recruiting the preinitiation complex proteins, or stabilizing the preinitiation complex.

The enhancer segment may be situated upstream or downstream of the enhanced gene and, due to looping of the DNA strands, there may be a separation of several thousand base pairs between the enhancer and initiator gene (start site). However, the enhancer and its regulated gene are located on the same chromosome (cis). The orientation of enhancers is not fixed – that is, the enhancer’s sequence may be reversed without altering its function.

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