The E75 ecdysone-inducible gene responsible for the 75B early puff in Drosophila encodes two new members of the steroid receptor superfamily.

Abstract

A pulse of the steroid hormone ecdysone at the end of Drosophila larval development triggers coordinate changes in both larval and imaginal tissues that result in metamorphosis to the adult fly. In larval salivary glands, this pulse activates a genetic regulatory hierarchy manifested by the induction of two kinds of transcription puffs in the polytene chromosomes: a small set of "early" puffs representing a primary response to the hormone, and a complex set of "late" puffs whose delayed appearance is dependent on proteins synthesized during the primary response. We isolated a 50-kb ecdysone-inducible gene, E75, that occupies the early puff locus at 75B.

Nitric oxide directly regulates gene expression during Drosophila development: need some gas to drive into metamorphosis?: Figure 1.

“…Indeed, E75, DHR3, and bFTZ-F1 are all transcriptionally regulated by 20E and show distinct expression profiles in concert with the hemolymph 20E titer fluctuation during development . Both E75 and DHR3 are directly induced by the 20E receptor complex EcR/USP, although DHR3 also requires indirect induction for its maximal expression (Segraves and Hogness 1990;Horner et al 1995). On the other hand, expression of bFTZ-F1 is repressed when the 20E titer is high and is only induced after the hemolymph 20E titer declines (Woodard et al 1994;Broadus et al 1999;Yamada et al 2000;Rewitz et al 2010).…”

Locus-specific variation in phosphorylation state of RNA polymerase II in vivo: correlations with gene activity and transcript processing.

“…Some of the most dramatic ecdysone-induced puffs are the so-called Chinese lanterns at 74EF and 75B, which are induced by the ecdysone titer increase that initiates molting (Ashburner and Richards 1976;Burtis et al 1990;Segraves and Hogness 1990). Part of a chromosome 3L displaying these large puffs is shown in Figure 4.…”

“…Chromosomal proteins can be covalently cross-linked in situ to these chromosomes and observed in the light microscope by immunofluorescence or immunochemical techniques (Greenleaf et al 1976;Silver and Elgin 1976;Zink et al 1991; for review, see Clark et al 1991). The patterns of transcriptional activity for many loci of the polytene chromosomes have been documented extensively, originally as manifested by cytologically visible puff formation (e.g., Ritossa 1962;Ashburner and Richards 1976) and more recently by molecular techniques (e.g., Ashburner and Bonner 1979;Burtis et al 1990;Segraves and Hogness 1990;Rabindran et al 1993). This information base seemed to provide the potential for correlating the activity state of certain loci with the form of Pol II found there.…”

“…Because puffing at these loci is a consequence of transcription (e.g., Burtis et al 1990;Segraves and Hogness 1990), it seems reasonable to conclude that the transcription at these sites is carried out by Pol II0. (It should be pointed out here that we have not yet presented direct evidence that any particular locus was actually transcriptionally active at the moment the chromosome preparation was made).…”

The promoter of DNA puff gene II/9-1 of Sciara coprophila is inducible by ecdysone in late prepupal salivary glands of Drosophila melanogaster.

“…The Ashburner model regained publicity (Ashburner, 1990) in recent reports describing the molecular cloning of DNA derived from three early-responding RNA puffs: 2B5, 74EF, and 75B (Chao and Guild, 1986;Burtis et al, 1990 andThummel et al, 1990;Segraves and Hogness 1990;respectively). The genes located at these loci have a complex structure with multiple transcription units encoding different proteins, some of which appear to be DNA binding proteins with nuclear localization and the ability to bind to ecdysone-inducible puffs.…”