Engrailed and polyhomeotic maintain posterior cell identity through cubitus-interruptus regulation

Abstract

In Drosophila, the subdivision into compartments requires the expression of engrailed (en) and hedgehog (hh) in the posterior cells and of cubitus-interruptus (ci) in the anterior cells. Whereas posterior cells express hh, only anterior cells are competent to respond to the hh signal, because of the presence of ci expression in these cells. We show here that engrailed and polyhomeotic (ph), a member of the Polycomb Group (PcG) genes, act concomitantly to maintain the repression of ci in posterior compartments during development. Using chromatin immunoprecipitation (ChIP), we identified a 1 kb genomic fragment located 4 kb upstream of the ci coding region that is responsible for the regulation of ci. This genomic fragment is bound in vivo by both Polyhomeotic and Engrailed. In particular, we show that Engrailed is responsible for the establishment of ci repression early during embryonic development and is also required, along with Polyhomeotic, to maintain the repression of ci throughout development.

Combgap contributes to recruitment of Polycomb group proteins in Drosophila

“…These groups also identified lethal alleles of cg and identified cg as a genetic repressor of the GLIfamily protein Cubitus interruptus (Ci) in the posterior compartment of the wing imaginal disc. Further, other studies had shown that the PcG protein Ph directly represses ci, suggesting that ci is a PcG target (35). These data suggested to us that Cg was a good candidate for a PRE DNA-binding protein.…”

“…Note that the level of H3K27me3 is insignificant throughout the ci region; therefore, ci does not appear to be a target for PRC2 in larvae. Interestingly, the upstream Ph peaks were partially contained within a reporter construct that has been shown to recruit Ph to a ci-reporter transgene (35). These data suggest that Cg may participate in the recruitment of Ph in the absence of PRC2.…”

“…cg behaves as a genetic repressor of ci (32,33,35,36); therefore we examined Cg binding at the ci locus. Cg binds near the ci promoter, colocalizing with weak Ph and Pho peaks, and also with three additional Ph peaks located further upstream, where there are no Pho peaks (see Fig.…”

Transcription of the 1.688 Satellite DNA Family Is Under the Control of RNA Interference Machinery inDrosophila melanogasterOvaries

“…Chromatin immunoprecipitation: Chromatin immunoprecipitation (ChIP) was performed according to described procedure (Chanas et al 2004). The analysis of DNA obtained in ChIP was done by semiquantative radioactive PCR as described above.…”

Engrailed homeoprotein acts as a signaling molecule in the developing fly

“…The larval wing imaginal disc, which gives rise to the adult wing, is subdivided into nonintermingling anterior (A) and posterior (P) compartments. En is present in the P compartment, where it acts as a transcription factor to establish and maintain P cell identity (Lawrence and Morata, 1976;Hidalgo, 1994;Zecca et al, 1995;Chanas et al, 2004). En is also known to be expressed (Blair, 1992) and to function in a few cell rows in the A compartment that abut the A/P boundary (Hidalgo, 1994).…”