A molecular mechanism for the stage specificity of the Drosophila prepupal genetic response to ecdysone.
Two successive pulses of ecdysone signal the ends of larval and prepupal development in Drosophila, inducing early and late puffs in the salivary gland polytene chromosomes. Early puff induction in prepupae is dependent on a preceding period of protein synthesis and low ecdysone concentration. We demonstrate here that the competence acquired during this interval can be provided by beta FTZ-F1, a nuclear hormone receptor superfamily member derived from the 75CD mid-prepupal puff. We show that beta FTZ-F1 represses its own transcription and is repressed by ecdysone, explaining its brief expression in mid-prepupae. We further show that ectopic beta FTZ-F1 expression leads to enhanced levels of ecdysone-induced BR-C, E74, and E75 early gene transcription and premature induction of the stage-specific 93F early puff and E93 transcription. These findings indicate that beta FTZ-F1 plays a central role in the prepupal genetic response to ecdysone and provide a molecular mechanism for stage-specific responses to steroid hormones.
Howard Hughes Medical Institute, Department of Human Genetics, Eccles Institute of Human Genetics, University of Utah, Salt Lake City 84112.
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Woodard
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Baehrecke
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Thummel
D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000502:physiology*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000187:drug effects / Q000196:embryology* / Q000235:genetics; D004440:Ecdysone / Q000494:pharmacology*; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000502:physiology; D005314:Embryonic and Fetal Development / Q000187:drug effects; D051717:Fushi Tarazu Transcription Factors; D015870:Gene Expression / Q000187:drug effects*; D018398:Homeodomain Proteins; D019476:Insect Proteins; D007814:Larva; D008969:Molecular Sequence Data; D011679:Pupa; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid / Q000096:biosynthesis / Q000502:physiology*; D012469:Salivary Glands / Q000502:physiology; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000096:biosynthesis / Q000502:physiology*; D014158:Transcription, Genetic / Q000187:drug effects
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; D019476:Insect Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C497169:ftz protein, Drosophila; C499712:nuclear hormone receptor FTZ-F1, Drosophila; D004440:Ecdysone; D003513:Cycloheximide