title: Insulator speckles associated with long-distance chromatin contacts.
abstract: Nuclear foci of chromatin binding factors are, in many cases, discussed as sites of long-range chromatin interaction in the three-dimensional nuclear space. Insulator binding proteins have been shown to aggregate into insulator bodies, which are large structures not involved in insulation; however, the more diffusely distributed insulator speckles have not been analysed in this respect. Furthermore, insulator binding proteins have been shown to drive binding sites for Polycomb group proteins into Polycomb bodies. Here we find that insulator speckles, marked by the insulator binding protein dCTCF, and Polycomb bodies show differential association with the insulator protein CP190. They differ in number and three-dimensional location with only 26% of the Polycomb bodies overlapping with CP190. By using fluorescence in situ hybridization (FISH) probes to identify long-range interaction (kissing) of the Hox gene clusters Antennapedia complex (ANT-C) and Bithorax complex (BX-C), we found the frequency of interaction to be very low. However, these rare kissing events were associated with insulator speckles at a significantly shorter distance and an increased speckle number. This suggests that insulator speckles are associated with long-distance interaction.
authors.affiliation: Institute for Genetics, Justus-Liebig-University, Heinrich-Buff-Ring 58, Giessen D35392, Germany.
authors.forename: Melanie K
authors.initials: MK
authors.lastname: Buxa
authors.affiliation: Department of Pathology, Josephine Nefkens Institute, Erasmus Optical Imaging Centre, Erasmus MC, Postbus 2040, Rotterdam 3000 CA, The Netherlands.
authors.forename: Johan A
authors.initials: JA
authors.lastname: Slotman
authors.affiliation: Department of Pathology, Josephine Nefkens Institute, Erasmus Optical Imaging Centre, Erasmus MC, Postbus 2040, Rotterdam 3000 CA, The Netherlands.
authors.forename: Martin E
authors.initials: ME
authors.lastname: van Royen
authors.affiliation: Department of Pathology, Josephine Nefkens Institute, Erasmus Optical Imaging Centre, Erasmus MC, Postbus 2040, Rotterdam 3000 CA, The Netherlands.
authors.forename: Maarten W
authors.initials: MW
authors.lastname: Paul
authors.affiliation: Department of Pathology, Josephine Nefkens Institute, Erasmus Optical Imaging Centre, Erasmus MC, Postbus 2040, Rotterdam 3000 CA, The Netherlands.
authors.forename: Adriaan B
authors.initials: AB
authors.lastname: Houtsmuller
authors.affiliation: Institute for Genetics, Justus-Liebig-University, Heinrich-Buff-Ring 58, Giessen D35392, Germany rainer.renkawitz@gen.bio.uni-giessen.de.
authors.forename: Rainer
authors.identifier: http://orcid.org/0000-0002-2591-1332
authors.initials: R
authors.lastname: Renkawitz
keywords: CP190; Insulator; Polycomb bodies; Speckle; dCTCF