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enhancer element
Function:
- a short region of DNA that can bind transcription factors to enhance transcription of genes within in a gene cluster
- enhancers are usually cis-acting
- an enhancer need not be close to the genes it activates, (it may be several thousand base pairs distant) but must be at least 100 bp from the transcription start site
- enhancers need not be located on the same chromosome
- enhancers may be found within introns
- an enhancer may be located upstream or downstream of the gene that it regulates
- orientation of enhancers is often unimportant
- this is so because chromatin is folded in a way that may allow the enhancer to be geometrically close to the promoter element & transcription start site despite its distance on the DNA strand
- goemetric proximity allows the enhancer element to interact with general transcription factors & RNA polymerase 2
- enhancers do not act on the promoter region itself, but are bound by activator proteins that interact with the mediator complex, which recruits polymerase 2 and general transcription factors
- many enhancer elements is that they contain several transcription factor binding sites clustered within 100 nucleotides
Specific
c-myb site
EkB site
estrogen response element (ERE)
far upstream sequence element (FUSE)
FSE2 site
heat shock element
HOX 1.3 site
Ig Eu enhancer
kappa-B motif
maf recognition element (MARE)
myb recognition element (MRE)
nuclear matrix attachment region
nuclear matrix protein-binding element
retinoid response element (RXRE)
rRNA upstream element
SP1-binding site
sterol regulatory element (SRE)
T alpha-1 enhancer
T alpha-2 enhancer
tumor necrosis factor [TNF] response element
xenobiotic response element (XRE)
General
transcription factor binding site
Properties
NAME: enhancer element
References
- Molecular Cell Biology (2nd ed) Darnell J; Lodish H
& Baltimore D (eds),Scientific American Books,
WH Freeman, NY 1990, pg 296
- Wikipedia: Enhancer (genetics)
http://en.wikipedia.org/wiki/Enhancer_(genetics)