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.
Zhang
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Zoological Institute, University of Zürich, Switzerland.
Bienz
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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