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Enhancers are regions of the genome that are major gene-regulatory elements. Enhancers control cell-type-specific gene expression programs, most often by looping through long distances to come in physical proximity with the promoters of their target genes. [33] While there are hundreds of thousands of enhancer DNA regions, [2] for a particular ...
Several cell function specific transcription factors (there are about 1,600 transcription factors in a human cell [31]) generally bind to specific motifs on an enhancer [32] and a small combination of these enhancer-bound transcription factors, when brought close to a promoter by a DNA loop, govern the level of transcription of the target gene.
T-cell development and activation is controlled by complementary placement of proximal and distal lck promoters. The generated environment of a Lck-PROX mice when approached with proximal promoter demonstrates maximal lck protein and normal thymic development, while distal promoters lead to deficient lck protein and unnormal thymic levels.
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.
CREs function to control transcription by acting nearby or within a gene. The most well characterized types of CREs are enhancers and promoters. Both of these sequence elements are structural regions of DNA that serve as transcriptional regulators. [citation needed] Cis-regulatory modules are one of several types of functional regulatory elements.
When they are located farther away from the promoter, insulator elements would compete with the enhancer and interfere with activation of transcription. [3] Loop formation is common in eukaryotes to bring distal elements (enhancers, promoters, locus control regions) into closer proximity for interaction during transcription. [4]
Promoter activity is a term that encompasses several meanings around the process of gene expression from regulatory sequences —promoters [2] and enhancers. [3] Gene expression has been commonly characterized as a measure of how much, how fast, when and where this process happens. [ 4 ]
Since the discovery of DHSs 30 years ago, they have been used as markers of regulatory DNA regions. These regions have been shown to map many types of cis-regulatory elements including promoters, enhancers, insulators, silencers and locus control regions. A high-throughput measure of these regions is available through DNase-Seq. [2]