title: Disclosure of a structural milieu for the proximity ligation reveals the elusive nature of an active chromatin hub.
abstract: The current progress in the study of the spatial organization of interphase chromosomes became possible owing to the development of the chromosome conformation capture (3C) protocol. The crucial step of this protocol is the proximity ligation-preferential ligation of DNA fragments assumed to be joined within nuclei by protein bridges and solubilized as a common complex after formaldehyde cross-linking and DNA cleavage. Here, we show that a substantial, and in some cases the major, part of DNA is not solubilized from cross-linked nuclei treated with restriction endonuclease(s) and sodium dodecyl sulphate and that this treatment neither causes lysis of the nucleus nor drastically affects its internal organization. Analysis of the ligation frequencies of the mouse β-globin gene domain DNA fragments demonstrated that the previously reported 3C signals were generated predominantly, if not exclusively, in the insoluble portion of the 3C material. The proximity ligation thus occurs within the cross-linked chromatin cage in non-lysed nuclei. The finding does not compromise the 3C protocol but allows the consideration of an active chromatin hub as a folded chromatin domain or a nuclear compartment rather than a rigid complex of regulatory elements.
authors: Institute of Gene Biology of the Russian Academy of Sciences, 119334 Moscow, Russia, University of Oslo, Center for Medical Studies in Russia, 119334 Moscow, Russia.
authors: Alexey A
authors: AA
authors: Gavrilov
authors: Ekaterina S
authors: ES
authors: Gushchanskaya
authors: Olga
authors: O
authors: Strelkova
authors: Oksana
authors: O
authors: Zhironkina
authors: Igor I
authors: II
authors: Kireev
authors: Olga V
authors: OV
authors: Iarovaia
authors: Sergey V
authors: SV
authors: Razin
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000737:chemistry; D002843:Chromatin / Q000737:chemistry*; D004247:DNA / Q000032:analysis; D004262:DNA Restriction Enzymes; D006657:Histones / Q000032:analysis; D008099:Liver / Q000648:ultrastructure; D051379:Mice; D012967:Sodium Dodecyl Sulfate; D012995:Solubility; D055544:beta-Globins / Q000235:genetics
chemical_list: D002843:Chromatin; D006657:Histones; D055544:beta-Globins; D012967:Sodium Dodecyl Sulfate; D004247:DNA; D004262:DNA Restriction Enzymes
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