- A 50-150bp DNA sequence that increases the rate of transcription of coding sequences. It may be located at various distances and in either orientation upstream from, downstream from or within a structural gene. When bound by a specific transcription factor it increases the levels of expression of the gene, but is not sufficient alone to cause expression. Distinguished from a promoter, that is alone sufficient to cause expression of the gene when bound.
Definition from: NCI Thesaurus via Unified Medical Language System at the National Library of Medicine
See also Understanding Medical Terminology.