The gypsy insulator can act as a promoter-specific transcriptional stimulator

Insulators define chromosomal domains such that an enhancer in one domain c annot activate a promoter in a different domain. We show that the Drosophil a gypsy insulator behaves as a cis-stimulatory element in the larval fat bo dy. Transcriptional stimulation by the insulator is distance dependent, as expected for a promoter element as opposed to an enhancer. Stimulation of a test alcohol dehydrogenase promoter requires a binding site for a GATA tra nscription factor, suggesting that the insulator may be facilitating access of this DNA binding protein to the promoter. Short-range stimulation requi res both the Suppressor of Hairy-wing protein and the Mod(mdg4)-62.7 protei n encoded by the trithorax group gene mod(mdg4). In the absence of interact ion with Mod(mdg4)-62.7, the insulator is converted into a short-range tran scriptional repressor but retains some cis-stimulatory activity over longer distances. These results indicate that insulator and promoter sequences sh are important characteristics and are not entirely distinct. We propose tha t the gypsy insulator can function as a promoter element and may be analogo us to promoter-proximal regulatory modules that integrate input from multip le distal enhancer sequences.