Question

Name a commonly used promoter.

Answer 1

Hint: The region of DNA where transcription is initiated is called a promoter. Promoters control the binding of RNA polymerase to DNA thus, they are a vital component of expression vectors. Promoter region controls when and where in the organism our gene of interest is expressed. Eukaryotic promoters are much more complex than eukaryotic promoters.

Complete answer:
Promoters are about 100-1000 bp long and are typically adjacent and upstream (5’) of the coding strand of the transcribed gene. Response elements (DNA sequence) located within the promoter region, provide a stable binding site for RNA polymerase and transcription factors.
Promoter binding site is different in bacteria and eukaryotes. For promoter recognition and binding, the core RNA polymerase in bacteria required an associated Sigma factor. In eukaryotes the process is much more complex. In eukaryotes RNA polymerase II binding to a promoter requires a minimum of seven transcription factors. Promoters are controlled by various DNA regulatory sequences including enhancer, insulator ,silencer and binding elements.
Commonly used eukaryotic promoter:
EF1 a : expression -constitutive, description-strong mammalian promoter from human elongation factor 1 alpha.
CMV: expression- constitutive, description- strong mammalian promoter from human cytomegalovirus.
Commonly used bacterial promoter:
Lac: expression- constitutive in the absence of a lac repressor (lacl or laclq). Can be induced by IPTG or lactose, description- promoter from lac operon.
trp: expression- repressible by tryptophan, description- promoter from E.coli tryptophan operon.

Note:
There are three main regions in a promoter. Core promoter: located most proximal start codon and contains RNA polymerase binding site, TATA box and transcription start site. General transcription factor protein and histone can bind to the Tata box. Proximal promoter: contain many primary e regulatory elements and located further upstream from core promoter. General transcription factors bind to this region. Distal promoter: located upstream of the proximal promoter. It mostly contains regulatory elements.