I have come across the terms Upstream regulatory Element, Downstream regulatory Element and Enhancer. I have referred to wikipedia articles but I apparently don't find any difference in them. Are URE upstream enhancers and DRE downstream enhancers?
If you could link any book/article it would be of great help.
In general, URE is a regulatory sequence (stimulatory on inhibitory) that is located before (in other words, to the 3’-side) the point of the transcription initiation. DRE, on contrary, is located after (to the 5’ side) the point of initiation. Enhancer is a regulatory sequence that stimulates the transcription after the binding with a complementary transcription factor. Enhancers are generally located upstream, but they can also be located downstream or even on the other chromosome.