title: Functional Requirements for Fab-7 Boundary Activity in the Bithorax Complex.
abstract: Chromatin boundaries are architectural elements that determine the three-dimensional folding of the chromatin fiber and organize the chromosome into independent units of genetic activity. The Fab-7 boundary from the Drosophila bithorax complex (BX-C) is required for the parasegment-specific expression of the Abd-B gene. We have used a replacement strategy to identify sequences that are necessary and sufficient for Fab-7 boundary function in the BX-C. Fab-7 boundary activity is known to depend on factors that are stage specific, and we describe a novel ∼700-kDa complex, the late boundary complex (LBC), that binds to Fab-7 sequences that have insulator functions in late embryos and adults. We show that the LBC is enriched in nuclear extracts from late, but not early, embryos and that it contains three insulator proteins, GAF, Mod(mdg4), and E(y)2. Its DNA binding properties are unusual in that it requires a minimal sequence of >65 bp; however, other than a GAGA motif, the three Fab-7 LBC recognition elements display few sequence similarities. Finally, we show that mutations which abrogate LBC binding in vitro inactivate the Fab-7 boundary in the BX-C.
authors: Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA.
authors: Daniel
authors: D
authors: Wolle
authors: Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland.
authors: Fabienne
authors: F
authors: Cleard
authors: Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA.
authors: Tsutomu
authors: T
authors: Aoki
authors: Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA.
authors: Girish
authors: G
authors: Deshpande
authors: Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA Laboratory of Gene Expression Regulation in Development, Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia pschedl@princeton.edu.
authors: Paul
authors: P
authors: Schedl
authors: Department of Genetics and Evolution, University of Geneva, Geneva, Switzerland.
authors: Francois
authors: F
authors: Karch
mesh_terms: D000818:Animals; D002843:Chromatin / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004330:Drosophila / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: C062393:Abd-B proteins, Drosophila; D002843:Chromatin; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; C063460:Trl protein, Drosophila; C066177:Ubx protein, Drosophila; C066591:abd-A protein, Drosophila