Ecdysone regulation of the Drosophila Sgs-4 gene is mediated by the synergistic action of ecdysone receptor and SEBP 3.
The steroid hormone 20-hydroxyecdysone controls both induction and repression of the Drosophila 'intermolt gene' Sgs-4. We show here that the ecdysone receptor binds to two sites, element I and element II, in the regulatory region of Sgs-4. A functional analysis revealed that element II appears to be of no importance for Sgs-4 expression, while element I proved to be an ecdysone response element that is necessary, but not sufficient, for induction of Sgs-4 expression. Our results provide no evidence that repression of Sgs-4 expression is mediated by one of the two receptor binding sites. In the close vicinity of elements I and II, we detected two binding sites of secretion enhancer binding protein 3 (SEBP 3). Like receptor element I, one of these sites also proved to be necessary, but not sufficient, for expression of Sgs-4. Therefore, induction of Sgs-4 requires binding of both ecdysone receptor and SEBP 3 to a complex hormone response unit, which also contains binding sites for a third factor, SEBP 2. The SEBP 2 sites coincide with binding sites of products of the Broad-Complex locus, which has been implicated recently with transduction of the hormonal signal. Thus, the available data suggest that induction of Sgs-4, and possibly other 'intermolt genes', is a combination of a primary and a secondary response to the hormone.
Lehmann
M
M
Institut für Genetik, Freien Universität Berlin, Germany.
Korge
G
G
D000818:Animals; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000502:physiology*; D004331:Drosophila melanogaster / Q000235:genetics*; D004440:Ecdysone / Q000494:pharmacology*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D017344:Genes, Insect; D005967:Glue Proteins, Drosophila / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000235:genetics*; D007814:Larva; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015345:Oligonucleotide Probes; D012333:RNA, Messenger / Q000235:genetics; D011987:Receptors, Steroid / Q000502:physiology*; D012045:Regulatory Sequences, Nucleic Acid; D012469:Salivary Glands; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000502:physiology*
D004268:DNA-Binding Proteins; D005967:Glue Proteins, Drosophila; D006360:Heat-Shock Proteins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D011987:Receptors, Steroid; D014157:Transcription Factors; C055469:ecdysone receptor; D004440:Ecdysone