title: CTCF tethers an insulator to subnuclear sites, suggesting shared insulator mechanisms across species.
abstract: Insulators can block an enhancer of one gene from activating a promoter on another nearby gene. Almost all described vertebrate insulators require binding of the regulatory protein CTCF for their activity. We show that CTCF copurifies with the nucleolar protein nucleophosmin and both are present at insulator sites in vivo. Furthermore, exogenous insulator sequences are tethered to the nucleolus in a CTCF-dependent manner. These interactions, quite different from those of the gypsy insulator element in Drosophila, may generate similar loop structures, suggesting a common theme and model for enhancer-blocking insulator action.
authors.affiliation: Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Timur M
authors.initials: TM
authors.lastname: Yusufzai
authors.forename: Hideaki
authors.initials: H
authors.lastname: Tagami
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Nakatani
authors.forename: Gary
authors.initials: G
authors.lastname: Felsenfeld
mesh_terms: D000818:Animals; D001665:Binding Sites; D000076246:CCCTC-Binding Factor; D002467:Cell Nucleus / Q000378:metabolism*; D002645:Chickens; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D019281:Dimerization; D006367:HeLa Cells; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D020014:K562 Cells; D013058:Mass Spectrometry; D008954:Models, Biological; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism; D000090243:Nucleophosmin; D011233:Precipitin Tests; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism / Q000502:physiology*; D016622:Silver Staining; D013045:Species Specificity
chemical_list: D000076246:CCCTC-Binding Factor; C000619697:CTCF protein, human; D002843:Chromatin; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C000716967:NPM1 protein, human; D009687:Nuclear Proteins; D012097:Repressor Proteins; D000090243:Nucleophosmin