3-9

Transcriptional Promoters

    A promoter is a short DNA sequence that signals the RNAPol where to begin transcription. Comparison of many E. coli DNA gene sequences shows two common promoter motifs [yellow boxes] with similar sequences, which are located approximately -10 [the TATA Box] & -35  [the CAT Box] bases 5' ('upstream') from the startpoint of RNA transcription [blue box]. Similar promoter regions occur in other prokaryotic and eukaryotic genes.

    It is important to remember
that the promoter is a DNA signal  for the downstream startpoint of transcription at position +1. The startpoint of translation is recognizable in the DNA still further downstream, but is actually on the transcribed RNA molecule, at the AUG start codon of the gene. [Note that the start codon does not appear in the diagram].


Figure © 2004 by Griffiths et al. ; text © 2011 by Steven M. Carr