REGULATION OF DROSOPHILA ADH PROMOTER SWITCHING BY AN INITIATOR-TARGETED REPRESSION MECHANISM

The stage-specific expression of the Drosophila alcohol dehydrogenase (Adh) gene is achieved through the alternate activation of two tandem promoters. The proximal promoter is active primarily during late embry onic development and early larval stages, while the distal promoter is active in late third instar larvae and adults. Here we provide eviden ce that this Adh promoter switch is regulated by a zinc finger repress or protein (AEF-1) that is expressed predominantly in adult flies and targets the initiator region of the proximal promoter. We propose that AEF-1 plays a critical role in Adh promoter switching by blocking int eractions between a component of the general transcription machinery a nd the initiator region of the proximal promoter.