title: Changes in chromatin structure and mobility in living cells at sites of DNA double-strand breaks.
abstract: The repair of DNA double-strand breaks (DSBs) is facilitated by the phosphorylation of H2AX, which organizes DNA damage signaling and chromatin remodeling complexes in the vicinity of the lesion. The disruption of DNA integrity induces an alteration of chromatin architecture that has been proposed to activate the DNA damage transducing kinase ataxia telangiectasia mutated. However, little is known about the physical properties of damaged chromatin. In this study, we use a photoactivatable version of GFP-tagged histone H2B to examine the mobility and structure of chromatin containing DSBs in living cells. We find that chromatin containing DSBs exhibits limited mobility but undergoes an energy-dependent local expansion immediately after DNA damage. The localized expansion observed in real time corresponds to a 30-40% reduction in the density of chromatin fibers in the vicinity of DSBs, as measured by energy-filtering transmission electron microscopy. The observed opening of chromatin occurs independently of H2AX and ATM. We propose that localized adenosine triphosphate-dependent decondensation of chromatin at DSBs establishes an accessible subnuclear environment that facilitates DNA damage signaling and repair.
authors.affiliation: Experimental Immunology Branch and 2Laboratory for Receptor Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA. kruhlakm@mail.nih.gov
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kruhlak
authors.forename: Arkady
authors.initials: A
authors.lastname: Celeste
authors.forename: Graham
authors.initials: G
authors.lastname: Dellaire
authors.forename: Oscar
authors.initials: O
authors.lastname: Fernandez-Capetillo
authors.forename: Waltraud G
authors.initials: WG
authors.lastname: Müller
authors.forename: James G
authors.initials: JG
authors.lastname: McNally
authors.forename: David P
authors.initials: DP
authors.lastname: Bazett-Jones
authors.forename: André
authors.initials: A
authors.lastname: Nussenzweig
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D002843:Chromatin / Q000737:chemistry / Q000235:genetics* / Q000648:ultrastructure; D045584:Chromosome Positioning / Q000235:genetics; D004247:DNA / Q000235:genetics* / Q000648:ultrastructure; D004249:DNA Damage / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics*; D004734:Energy Metabolism / Q000235:genetics; D005260:Female; D005347:Fibroblasts; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission; D015398:Signal Transduction / Q000235:genetics
chemical_list: D002843:Chromatin; D006657:Histones; D049452:Green Fluorescent Proteins; D000255:Adenosine Triphosphate; D004247:DNA