Interactions of thePolycomb group of genes with homeotic loci ofDrosophila

Abstract

Members of thePolycomb (Pc) group of genes are required for the correct determination of segment identity, and are thought to be negative regulators of thebithorax andAntennapedia complexes. This hypothesis has been tested molecularly for only some members of thePc group. Here, we examine the distribution ofUltrabithorax (Ubx),Antennapedia (Antp), andSex combs reduced (Scr) proteins in the epidermis, central nervous system, and midgut of embryos homozygous for mutations in tenPc group genes. We show that zygotic loss of mostPc group genes causes ectopic expression ofUbx andAntp, but that there are differences in time and tissue-specificity. FivePc group mutations lack midgut constrictions and also exhibit ectopic or suppressedUbx expression and suppression ofAntp expression. Distribution ofAntp is upset earlier than distribution ofUbx in the central nervous system of everyPc group mutant affecting both genes. Loss of the zygotic products ofPolycomb, extra sex combs, andAdditional sex combs cause ectopic expression ofScr in epidermis, and allPc group genes exceptPsc have suppressedScr expression in the nervous system. These results are discussed with respect to the function of thePc group.

Noncoding RNAs of the Ultrabithorax Domain of the Drosophila Bithorax Complex

“…But in the Bender and Fitzgerald (2002) example, it was clear that the loss of repression was gradual. There was almost no effect of persistent transcription in late embryos (Bender and Fitzgerald 2002), although Polycomb repression is established by the early germ-band elongation stage of embryogenesis (stage 10, 5 hr), as judged by the time of initial misexpression of the homeotic genes in Polycomb group mutants (Struhl and Akam 1985;McKeon and Brock 1991;Simon et al 1992). Breaking through Polycomb group repression apparently requires strong and persistent transcription, but neither quality applies to the BX-C ncRNAs at blastoderm.…”

Drosophila O -GlcNAc transferase (OGT) is encoded by the Polycomb group (PcG) gene, super sex combs ( sxc )

“…Mutations in sxc cause homeotic phenotypes (9) because of derepression of homeotic loci (21,22) and enhance the phenotypes of some PcG mutations (14). Together with the existing genetic and molecular data, our polytene and ChIP binding data show that OGT acts directly at PcG targets in chromatin but does not have a direct role in recruiting PcG protein to chromatin: O-GlcNAc modification, but not Pc/Ph binding, is abolished at PcG target sites in sxc/sxc mutants.…”

Drosophila castor is regulated negatively by the Ubx and abdA genes, but positively by the AbdB gene

“…This expression pattern is maintained by the negative regulation of Polycomb group (PcG) genes (Dellino et al, 2002). Mutations of PcG genes lead to homeotic transformations of segments into a more posterior identity (Jürgens, 1985;McKeon and Brock, 1991;Simon et al, 1992).…”