A model for gene activation at a distance in eukaryotes. In this example, the general transcription factors
and RNA polymerase do not assemble efficiently at the promoter on their own, and a gene regulatory protein bound at an enhancer is necessary to stimulate the assembly process. Looping of the DNA permits contact between the regulatory protein bound to the enhancer and the transcription complex bound to the promoter. The broken stretch of DNA signifies that the length of DNA between the enhancer and the start of transcription can be up to tens of thousands of nucleotide pairs