A regulatory sequence (also called a regulatory region or a regulatory area) is a segment of DNA where regulatory proteins such as transcription factors bind preferentially. These regulatory proteins bind to short stretches of DNA called regulatory regions, which are appropriately positioned in the genome, usually a short distance 'upstream' of the gene being regulated. By doing so, these regulatory proteins can either recruit another protein complex, called the RNA polymerase. In this way, they controlgene expression and thus protein expression.