An ecdysone response element in the Drosophila hsp27 promoter.

It has previously been shown that a region of 100 bp in the Drosophila hsp27 promoter is sufficient to confer ecdysone inducibility on a heterologous gene. We now show, using binding and DNase I footprinting assays, that a 23-bp hyphenated dyad within this sequence forms a protein-binding site, and that this is sufficient for inducibility. The sequence shows partial homology with mammalian steroid receptor binding sites. UV crosslinking identifies an 80- to 90-kd protein that binds specifically to this sequence and is thus a candidate for the ecdysone receptor.