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Promoters are located near the transcription start sites of genes, upstream on the DNA (towards the 5' region of the sense strand). Promoters can be about 100–1000 base pairs long, the sequence of which is highly dependent on the gene and product of transcription, type or class of RNA polymerase recruited to the site, and species of organism ...
Regulatory sequences are located at the extremities of genes. These sequence regions can either be next to the transcribed region (the promoter) or separated by many kilobases (enhancers and silencers). [8] The promoter is located at the 5' end of the gene and is composed of a core promoter sequence and a proximal promoter sequence.
Intergenic regions may contain a number of functional DNA sequences such as promoters and regulatory elements, enhancers, spacers, and (in eukaryotes) centromeres. [2] They may also contain origins of replication, scaffold attachment regions, and transposons and viruses.
In eukaryotes, the 5′ flanking region has a complex set of regulatory elements such as enhancers, silencers, and promoters. The primary promoter element in eukaryotes is the TATA box. Other promoter elements found in eukaryotic 5′ flanking regions include initiator elements, downstream core promoter element, CAAT box, and the GC box. [1]
In eukaryotes, promoters usually have the following four components: the TATA box, a TFIIB recognition site, an initiator, and the downstream core promoter element. [5] It has been found that a single gene can contain multiple promoter sites. [6]
The TATA box is usually located 25-35 base pairs upstream of the transcription start site. Genes containing the TATA box usually require additional promoter elements, including an initiator site located just upstream of the transcription start site and a downstream core element (DCE). [3]
A third study found more than 2,000 genes differentially methylated between colon cancers and adjacent mucosa. Using gene set enrichment analysis, 569 out of 938 gene sets were hypermethylated and 369 were hypomethylated in cancers. [28] Hypomethylation of CpG islands in promoters results in overexpression of the genes or gene sets affected.
The promoters are usually located 15 to 19 bases apart and are most commonly found upstream of the genes they control. [ 2 ] [ 1 ] RNA polymerase is made up of 4 subunits, which include two alphas, a beta, and a beta prime (α, α, β, and β').