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Gene expression in mammals is regulated by many cis-regulatory elements, including core promoters and promoter-proximal elements that are located near the transcription start sites of genes. Core promoters are sufficient to direct transcription initiation, but generally have low basal activity. [29]
Distal promoter – the distal sequence upstream of the gene that may contain additional regulatory elements, often with a weaker influence than the proximal promoter Anything further upstream (but not an enhancer or other regulatory region whose influence is positional/orientation independent)
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. [2]
The proximal promoter region binds transcription factors that modify the affinity of the core promoter for RNA polymerase. [9] [10] Genes may be regulated by multiple enhancer and silencer sequences that further modify the activity of promoters by binding activator or repressor proteins.
An active enhancer regulatory sequence of DNA is enabled to interact with the promoter DNA regulatory sequence of its target gene by formation of a chromosome loop. This can initiate messenger RNA (mRNA) synthesis by RNA polymerase II (RNAP II) bound to the promoter at the transcription start site of the gene. The loop is stabilized by one ...
Even though infrequent, transcriptional regulation can involve elements located in a chromosome different from one where the promoter resides. Proximal enhancers or promoters of neighboring genes can serve as platforms to recruit more distal elements. [35]
Insulators situated between enhancers and promoters help define the genes that an enhancer can or cannot influence. Eukaryotic transcriptional activators have separate DNA-binding and activating functions. [1] Upon binding to its cis-element, an activator can recruit polymerase directly or recruit other factors needed by the transcriptional ...
A transcriptional activator is a protein (transcription factor) that increases transcription of a gene or set of genes. [1] Activators are considered to have positive control over gene expression, as they function to promote gene transcription and, in some cases, are required for the transcription of genes to occur.