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Sgs-3 chromatin structure and trans-activators: developmental and ecdysone induction of a glue enhancer-binding
P Georgel1, P Ramain, A Giangrande
1Laboratoire de Génétique Moléculaire des Eucaryotes du Centre National de la Recherche Scientifique, Unité 184 de Biologie Moléculaire, Strasbourg, France.
Abstract:
The transcription of the Drosophila melanogaster 68C salivary gland glue gene Sgs-3 involves the interaction of a distal and a proximal regulatory region. These are marked in vivo by a specific chromatin structure which is established sequentially during development, starting early in embryogenesis. The distal region is characterized by a stage- and tissue-specific DNase I hypersensitive site. A stage- and tissue-specific factor, GEBF-I, binds in this region and is missing in 2B5 mutant larvae which lack Sgs-3 transcripts. This binding involves the simultaneous interaction with two distinct DNA sequences which induces conformational changes in the protein. Salivary glands acquire competence to respond to ecdysone in the mid-third larval instar, whereafter the hormone rapidly induces both the GEBF-I protein and Sgs-3 transcription.