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I have been confused as to the difference between a response element and an enhancer.

Wikipedia has the definition of response element as the following:

Response elements are short sequences of DNA within a gene promoter region that are able to bind specific transcription factors and regulate transcription of genes.

Wikipedia's definition of enhancers:

In genetics, an enhancer is a short (50-1500 bp) region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur.[1][2] These proteins are usually referred to as transcription factors.

They seem almost the same. What are the main differences?

The only difference I can see is that response elements can both halt transcription or allow for it. While enhancers only promote transcription if the transcription factor is present.

Is this the difference between the two, or is there something else that differentiates them?

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Enhancers specifically bind transcription factors in an effort to obtain robust rates of transcription, in a very general fashion and may be upstream or downstream of a promoter. Remember that you don't need to receive a signal to produce housekeeping genes, regulated by general transcription factors, because they're always needed (in part). A response element can enhance or repress transcription depending on the stimulus.

Vitamin D response element (VDRE) is a fair example: In response to your extracellular calcitriol or 1,25(OH)2D, the vitamin D receptor will complex with a number of proteins that bind at the VDRE, controlling transcription of various vitamin D-controlled gene targets.

Vitamin D activity is mediated through binding of 1,25(OH)2D3 to the vitamin D receptor (VDR), which can regulate transcription of other genes involved in cell regulation, growth, and immunity. VDR modulates the expression of genes by forming a heterodimer complex with retinoid-X-receptors (RXR).

Source: http://www.wikipathways.org/index.php/Pathway:WP1531

And just as well, other promoters such as that for pro-parathyroid hormone contain VDRE sequences that suppress it's transcription (ref).

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  • $\begingroup$ I had the notion that transcription factors binding to enhancers can also have a ligand binding domain. Which would mean that it would be activating depending on a stimulus. If my notion is correct, what then differentiates them? $\endgroup$ – Hawkeye Aug 8 '17 at 20:53
  • $\begingroup$ Essentially your RE is always in the promoter, and the action can be bidirectional, either activating or silencing, based on the same stimulus across genes that contain that RE. You enhancer can be anywhere and always up-regulates in response to any number of variables that site reacts to. $\endgroup$ – CKM Aug 8 '17 at 21:09
  • $\begingroup$ You know it just cant be miles away from the TSS because it still needs to interact, so when I say anywhere I mean not just in the promoter. $\endgroup$ – CKM Aug 8 '17 at 21:13

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