title: DNA double-strand breaks in heterochromatin elicit fast repair protein recruitment, histone H2AX phosphorylation and relocation to euchromatin.
abstract: DNA double-strand breaks (DSBs) can induce chromosomal aberrations and carcinogenesis and their correct repair is crucial for genetic stability. The cellular response to DSBs depends on damage signaling including the phosphorylation of the histone H2AX (γH2AX). However, a lack of γH2AX formation in heterochromatin (HC) is generally observed after DNA damage induction. Here, we examine γH2AX and repair protein foci along linear ion tracks traversing heterochromatic regions in human or murine cells and find the DSBs and damage signal streaks bending around highly compacted DNA. Given the linear particle path, such bending indicates a relocation of damage from the initial induction site to the periphery of HC. Real-time imaging of the repair protein GFP-XRCC1 confirms fast recruitment to heterochromatic lesions inside murine chromocenters. Using single-ion microirradiation to induce localized DSBs directly within chromocenters, we demonstrate that H2AX is early phosphorylated within HC, but the damage site is subsequently expelled from the center to the periphery of chromocenters within ∼ 20 min. While this process can occur in the absence of ATM kinase, the repair of DSBs bordering HC requires the protein. Finally, we describe a local decondensation of HC at the sites of ion hits, potentially allowing for DSB movement via physical forces.
authors.affiliation: Department of Biophysics, GSI Helmholtz Center for Heavy Ion Research, Planckstrasse 1, 64291 Darmstadt, Germany.
authors.forename: Burkhard
authors.initials: B
authors.lastname: Jakob
authors.forename: Jörn
authors.initials: J
authors.lastname: Splinter
authors.forename: Sandro
authors.initials: S
authors.lastname: Conrad
authors.forename: Kay-Obbe
authors.initials: KO
authors.lastname: Voss
authors.forename: Daniele
authors.initials: D
authors.lastname: Zink
authors.forename: Marco
authors.initials: M
authors.lastname: Durante
authors.forename: Markus
authors.initials: M
authors.lastname: Löbrich
authors.forename: Gisela
authors.initials: G
authors.lastname: Taucher-Scholz
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D002478:Cells, Cultured; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism; D022041:Euchromatin / Q000378:metabolism*; D006367:HeLa Cells; D006570:Heterochromatin / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D051379:Mice; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D000076105:X-ray Repair Cross Complementing Protein 1
chemical_list: D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D022041:Euchromatin; C468783:H2AX protein, human; D006570:Heterochromatin; D006657:Histones; D025521:Tumor Suppressor Proteins; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; C000619352:Xrcc1 protein, mouse; C475961:gamma-H2AX protein, mouse; D000090266:Chromobox Protein Homolog 5; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases