Retroelements and their impact on genome evolution and functioning
239 Insulators are regulatory DNA elements blocking the interaction between enhancer and promoter when interposed between them . Insulators do not inactivate enhancer and promoter directly. It was shown that the enhancer that is separated from one promoter by an insulator is still able to activate another, unseparated promoter . The Drosophila melanogaster insulator found in the 5'-regulatory region of the MDG4 retrotransposon ( gypsy ) has been studied most comprehensively . This insulator is a 430-bp DNA fragment comprising 12 copies of the consensus sequence 5'-PyPuTTGCATACCPy-3', to which the protein coded by the su(Hw) gene binds . Inactivation of this gene results in the loss of insulation and restoration of enhancer–promoter interactions.