title: A Polycomb and GAGA dependent silencer adjoins the Fab-7 boundary in the Drosophila bithorax complex.
abstract: The homeotic genes of the Drosophila bithorax complex are controlled by a large cis-regulatory region that ensures their segmentally restricted pattern of expression. A deletion that removes the Frontabdominal-7 cis-regulatory region (Fab-7') dominantly transforms parasegment 11 into parasegment 12. Previous studies suggested that removal of a domain boundary element on the proximal side of Fab-7' is responsible for this gain-of-function phenotype. In this article we demonstrate that the Fab-7' deletion also removes a silencer element, the iab-7 PRE, which maps to a different DNA segment and plays a different role in regulating parasegment-specific expression patterns of the Abd-B gene. The iab-7 PRE mediates pairing-sensitive silencing of mini-white, and can maintain the segmentally restricted expression pattern of a BXD, Ubx/lacZ reporter transgene. Both silencing activities depend upon Polycomb Group proteins. Pairing-sensitive silencing is relieved by removing the transvection protein Zeste, but is enhanced in a novel pairing-independent manner by the zeste' allele. The iab-7 PRE silencer is contained within a 0.8-kb fragment that spans a nuclease hypersensitive site, and silencing appears to depend on the chromatin remodeling protein, the GAGA factor.
authors.affiliation: Department of Molecular Biology, Princeton University, New Jersey 08544, USA. khagstrom@watson.princeton.edu
authors.forename: K
authors.initials: K
authors.lastname: Hagstrom
authors.forename: M
authors.initials: M
authors.lastname: Muller
authors.forename: P
authors.initials: P
authors.lastname: Schedl
mesh_terms: D000483:Alleles; D000818:Animals; D002843:Chromatin / Q000235:genetics; D003433:Crosses, Genetic; D004247:DNA / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D004330:Drosophila / Q000196:embryology / Q000235:genetics* / Q000254:growth & development*; D029721:Drosophila Proteins; D005127:Eye Color / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D017344:Genes, Insect; D005816:Genetic Complementation Test; D006579:Heterozygote; D018398:Homeodomain Proteins / Q000235:genetics; D006720:Homozygote; D019476:Insect Proteins / Q000235:genetics; D008297:Male; D009154:Mutation; D063150:Polycomb Repressive Complex 1; D014157:Transcription Factors / Q000235:genetics
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D019476:Insect Proteins; C066770:Pc protein, Drosophila; D014157:Transcription Factors; C063460:Trl protein, Drosophila; C060849:z protein, Drosophila; D004247:DNA; D063150:Polycomb Repressive Complex 1