A researcher has identified a gene of unknown function by linkage analysis in an extended family showing early onset Alzheimer dementia. While characterising the regulation of this gene in a transgenic cell-culture system the researcher has focussed on a 860 bp sequence located 2,412 bp before the start of transcription. When it is removed, expression of the gene decreases 30-fold. When it is put back in either orientation, the expression is restored. Which of the following best defines this sequence?