THE REACTION WITH POLYTENE CHROMOSOMES OF ANTIBODIES RAISED AGAINST DROSOPHILA E75A PROTEIN

The steroid insect molting hormone ecdysone rapidly induces a small nu mber of polytene chromosome puffs in Drosophila. The Ashburner model p roposes that the corresponding early genes encode proteins involved in both the induction of the late genes and the repression of the early genes. The Drosophila E75 early gene has been isolated and two of its products, E75A and E75B, have been shown to be members of the steroid receptor superfamily. We have now prepared antisera directed against A - and B-specific regions of the E75 proteins. Antisera and a monoclona l antibody raised against E75A, the major larval protein product of th e E75 gene, bind to discrete sites in native salivary gland chromosome s. These sites are closely correlated with early and late ecdysone res ponsive loci.