Segmental determination in Drosophila conferred by hunchback (hb), a repressor of the homeotic gene Ultrabithorax (Ubx).
The activity of homeotic genes in Drosophila cells determines segment-specific morphogenesis. Here, we provide evidence that the product of hunchback (hb), a segmentation gene, acts as a direct repressor or "silencer" of the homeotic gene Ultrabithorax (Ubx) and thus prevents ectopic activity of this gene: we show, by stable integration of reporter gene constructs, that hb protein binding sites are capable of repressing at a distance the activity of an embryonic Ubx enhancer outside the Ubx expression domain. This silencing activity is observed at advanced embryonic stages, at a time when the hb gene product is no longer detectable or required, and is dependent on the function of Polycomb (Pc). We propose a working hypothesis as to how hb protein in a "hit-and-run" fashion may effect stable and heritable silencing of the Ubx gene throughout advanced stages of development, thus mediating repression of this homeotic gene outside its realm of function.
Zoological Institute, University of Zürich, Switzerland.
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Zhang
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Bienz
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004330:Drosophila / Q000196:embryology / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000502:physiology*; D005801:Genes, Homeobox; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D009024:Morphogenesis; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping
D009838:Oligodeoxyribonucleotides