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Multiple interacting elements delineate an ecdysone-dependent regulatory region with secondary responsive character
1Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Ohio 45267-0524, USA.
Journal of Molecular Biology
|June 2, 1995
Summary
Regulatory sequences in Drosophila respond to the steroid hormone ecdysone indirectly. Multiple DNA segments cooperate for hormonal responsiveness, requiring secondary factors, not direct ecdysone receptor binding.
Area of Science:
- Molecular Biology
- Genetics
- Developmental Biology
Background:
- The small heat shock gene locus 67B1 in Drosophila melanogaster exhibits ecdysone-induced chromatin perturbation.
- Understanding gene regulation by steroid hormones is crucial in developmental biology.
Purpose of the Study:
- To identify and characterize ecdysone-dependent regulatory sequences within the hsp23-gene 1 intergenic region.
- To elucidate the mechanism of hormonal responsiveness in this specific genomic locus.
Main Methods:
- Transient expression assays using hsp70-lacZ reporter constructs in Drosophila tissue culture cells.
- Delimitation of functional DNA segments within the intergenic region.
Main Results:
- Five functional segments were identified, with three core regions within the chromatin perturbation zone.
- Maximal transcription required cooperative interactions among multiple DNA segments.
- Ecdysone receptor binding was not detected in the delineated regions, suggesting involvement of secondary factors.
- Hormonal activation exhibited a time lag and sensitivity to cycloheximide.
Conclusions:
- The identified cis-acting elements respond to ecdysone indirectly, likely through products of primary responsive genes.
- Cooperative interactions between multiple regulatory elements are essential for full ecdysone-induced gene expression.