title: CTCF genomic binding sites in Drosophila and the organisation of the bithorax complex.
abstract: Insulator or enhancer-blocking elements are proposed to play an important role in the regulation of transcription by preventing inappropriate enhancer/promoter interaction. The zinc-finger protein CTCF is well studied in vertebrates as an enhancer blocking factor, but Drosophila CTCF has only been characterised recently. To date only one endogenous binding location for CTCF has been identified in the Drosophila genome, the Fab-8 insulator in the Abdominal-B locus in the Bithorax complex (BX-C). We carried out chromatin immunopurification coupled with genomic microarray analysis to identify CTCF binding sites within representative regions of the Drosophila genome, including the 3-Mb Adh region, the BX-C, and the Antennapedia complex. Location of in vivo CTCF binding within these regions enabled us to construct a robust CTCF binding-site consensus sequence. CTCF binding sites identified in the BX-C map precisely to the known insulator elements Mcp, Fab-6, and Fab-8. Other CTCF binding sites correlate with boundaries of regulatory domains allowing us to locate three additional presumptive insulator elements; "Fab-2," "Fab-3," and "Fab-4." With the exception of Fab-7, our data indicate that CTCF is directly associated with all known or predicted insulators in the BX-C, suggesting that the functioning of these insulators involves a common CTCF-dependent mechanism. Comparison of the locations of the CTCF sites with characterised Polycomb target sites and histone modification provides support for the domain model of BX-C regulation.
authors.affiliation: Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Eimear E
authors.initials: EE
authors.lastname: Holohan
authors.forename: Camilla
authors.initials: C
authors.lastname: Kwong
authors.forename: Boris
authors.initials: B
authors.lastname: Adryan
authors.forename: Marek
authors.initials: M
authors.lastname: Bartkuhn
authors.forename: Martin
authors.initials: M
authors.lastname: Herold
authors.forename: Rainer
authors.initials: R
authors.lastname: Renkawitz
authors.forename: Steven
authors.initials: S
authors.lastname: Russell
authors.forename: Robert
authors.initials: R
authors.lastname: White
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D000076246:CCCTC-Binding Factor; D047369:Chromatin Immunoprecipitation; D016384:Consensus Sequence; D004247:DNA / Q000235:genetics / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D017344:Genes, Insect; D049750:Genome, Insect; D038101:Insulator Elements; D008957:Models, Genetic; D020411:Oligonucleotide Array Sequence Analysis; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000076246:CCCTC-Binding Factor; C524946:CTCF protein, Drosophila; D017931:DNA Primers; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D012097:Repressor Proteins; D004247:DNA