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For example, researchers have found a translocation between chromosomes 8 and 22 (in the region containing the p300 gene) in several people with a cancer of blood cells called acute myeloid leukemia (AML). Another translocation, involving chromosomes 11 and 22, has been found in a small number of people who have undergone cancer treatment.
An enhancer localized in a DNA region distant from the promoter of a gene can have a very large effect on gene expression, with some genes undergoing up to 100-fold increased expression due to an activated enhancer. [32] Enhancers are regions of the genome that are major gene-regulatory elements. Enhancers control cell-type-specific gene ...
MyoD, also known as myoblast determination protein 1, [5] is a protein in animals that plays a major role in regulating muscle differentiation.MyoD, which was discovered in the laboratory of Harold M. Weintraub, [6] belongs to a family of proteins known as myogenic regulatory factors (MRFs). [7]
Enhancers are bound by transcription activator proteins and transcriptional regulation is typically controlled by more than one activator. Enhanceosomes are formed in special cases when these activators cooperatively bind together along the enhancer sequence to create a distinct three-dimensional structure.
This region is known as the enhancer region. Studies have suggested that thyroid hormone (T3) controls Sox2 expression via the enhancer region. The expression of TRα1 (thyroid hormone receptor) is increased in proliferating and migrating neural stem cells.
Enhancer regions, as described above, are several hundred nucleotides long. To be activated, the enhancer region must have the nucleosomes evicted from the DNA so that the multiple transcription factors that bind to that enhancer DNA would have access to their binding sites (see bottom panel in Figure "Chromatin").
H3K4me1 is a chromatin signature of enhancers, H3K4me2 is highest toward the 5′ end of transcribing genes and H3K4me3 is highly enriched at promoters and in poised genes. H3K27me3 , H4K20me1 and H3K4me1 silence transcription in embryonic fibroblasts, macrophages, and human embryonic stem cells (ESCs).
Enhancers function as a "turn on" switch in gene expression and will activate the promoter region of a particular gene while silencers act as the "turn off" switch. Though these two regulatory elements work against each other, both sequence types affect the promoter region in very similar ways. [ 4 ]