Promoters and enhancers
Promoters and enhancers are control elements.
- The promoter region is the site of the start of transcription.
Transcription factors bind to the promoter sequence and form a transcription initiation complex.
It is normally only possible for RNA polymerase to bind to the promoter sequence if transcription factors are already present.
- Enhancer regions are another common type of control element.
In eukaryotes, these regions may be hundreds of bases away from the gene, but they are physically close to the gene due to the coiled structure of DNA. They work by bending the DNA sequence in order to enhance the rate of transcription.