20.1Introduction Enhancer element is a cis-acting sequence that increases the utilization of (some)eukaryotic promoters, and can function in either orientation and in any location (upstream or downstream relative to the promoter 消当Enhancer element is a cis-acting sequence that increases the utilization of (some) eukaryotic promoters, and can function in either orientation and in any location (upstream or downstream) relative to the promoter. 20.1 Introduction