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In bacteria, the promoter contains two short sequence elements approximately 10 (Pribnow Box) and 35 nucleotides upstream from the transcription start site. [2] The sequence at -10 (the -10 element) has the consensus sequence TATAAT. The sequence at -35 (the -35 element) has the consensus sequence TTGACA.
The Pribnow box has a function similar to the TATA box that occurs in promoters in eukaryotes and archaea: it is recognized and bound by a subunit of RNA polymerase during initiation of transcription. [3] This region of the DNA is also the first place where base pairs separate during prokaryotic transcription to allow access to the template strand.
Figure 1. TATA box structural elements. The TATA box consensus sequence is TATAWAW, where W is either A or T. In molecular biology, the TATA box (also called the Goldberg–Hogness box) [1] is a sequence of DNA found in the core promoter region of genes in archaea and eukaryotes. [2]
The promoter region is a prime regulator of transcription. Promoter regions regulate transcription of all genes within bacteria. As a result of their involvement, the sequence of base pairs within the promoter region is significant; the more similar the promoter region is to the consensus sequence, the tighter RNA polymerase will be able to bind.
The tac promoter consists of the '–35' region of the trp promoter and the '–10' region of the lac promoter (and differs from a related trc promoter by 1 bp [3]). The tac promoter is, therefore, inducible by IPTG (Isopropyl β- D -1-thiogalactopyranoside), whilst also allowing higher maximum gene expression than either the lac or trp promoters.
Any mutation allowing a mutated nucleotide in the core promoter sequence to look more like the consensus sequence is known as an up mutation. This kind of mutation will generally make the promoter stronger, and thus the RNA polymerase forms a tighter bind to the DNA it wishes to transcribe and transcription is up-regulated.
Promoter activity of the P-RM and P-R promoters vs RNA polymerase concentration in the enterobacteriophage lambda [1]. Promoter activity is a term that encompasses several meanings around the process of gene expression from regulatory sequences —promoters [2] and enhancers. [3]
Example of a T-REx system controlling the expression of shRNA. Tetracycline-controlled transcriptional activation is a method of inducible gene expression where transcription is reversibly turned on or off in the presence of the antibiotic tetracycline or one of its derivatives (e.g. doxycycline).