Gene expression

3. Transcription

3.3 Initiation of transcription

The Promoter

The promoter is the DNA region bound by RNA polymerase, prior to the start of RNA synthesis. It is made up of one or several conserved sequences marking the beginning of a gene and regulating the level of transcription.

A conserved sequence is a sequence that is found to be nearly identical in all the genes of a particular organism.

Promoter characteristics:

• Part of the gene located upstream from the initiation site of transcription.
• Contains conserved sequence(s) recognized by proteins responsible for the initiation of transcription.
• Allows for the recruitment of RNA polymerase.
• Has a direction (orientation of transcription and thus selection of the transcribed strand).