Chapter 14: Eukaryotic Protein-coding Genes have a Core Promoter and Regulatory Elements

there are three features in most promoters on protein-coding genes; regulatory elements, a TATA box, and a transcriptional start site

common sequence patterns found within promoters are;

• core promoter is a short DNA sequence necessary to start transcription. It contains the a TATAAA sequence (TATA box) and the start site where transcription begins

• The TATA box is 25bp above the start site and determines the exact starting spot for transcription. If undefined, transcription can start at a variety of locations.

• the core promoter produces low levels of transcription called basal transcription

regulatory elements (DNA sequences) are recognized by transcription factors (proteins) to influence the rate of transcription

• activating sequences (enhancers) stimulate transcription. Without them there are low levels of basal transcription

• silencers inhibit transcription

• regulatory elements are typically to the left of the core promoter but vary across different genes. Distance doesn’t necessarily equate to affect on RNA polymerase efficacy.

DNA sequences that only act on a specific gene, like the TATA box or regulatory elements, are cis-acting elements because they are always at least on the same chromosome as the gene the effect (cis=next to)

The transcription factors that bind to these sequences are trans-acting factors (trans=across from) because the genes that encode for these proteins might be far from the core promoter and regulatory elements.