title: Histone H2AX phosphorylation is dispensable for the initial recognition of DNA breaks.
abstract: Histone H2AX is rapidly phosphorylated in the chromatin micro-environment surrounding a DNA double-strand break (DSB). Although H2AX deficiency is not detrimental to life, H2AX is required for the accumulation of numerous essential proteins into irradiation induced foci (IRIF). However, the relationship between IRIF formation, H2AX phosphorylation (gamma-H2AX) and the detection of DNA damage is unclear. Here, we show that the migration of repair and signalling proteins to DSBs is not abrogated in H2AX(-/-) cells, or in H2AX-deficient cells that have been reconstituted with H2AX mutants that eliminate phosphorylation. Despite their initial recruitment to DSBs, numerous factors, including Nbs1, 53BP1 and Brca1, subsequently fail to form IRIF. We propose that gamma-H2AX does not constitute the primary signal required for the redistribution of repair complexes to damaged chromatin, but may function to concentrate proteins in the vicinity of DNA lesions. The differential requirements for factor recruitment to DSBs and sequestration into IRIF may explain why essential regulatory pathways controlling the ability of cells to respond to DNA damage are not abolished in the absence of H2AX.
authors.affiliation: Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Arkady
authors.initials: A
authors.lastname: Celeste
authors.forename: Oscar
authors.initials: O
authors.lastname: Fernandez-Capetillo
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kruhlak
authors.forename: Duane R
authors.initials: DR
authors.lastname: Pilch
authors.forename: David W
authors.initials: DW
authors.lastname: Staudt
authors.forename: Alicia
authors.initials: A
authors.lastname: Lee
authors.forename: Robert F
authors.initials: RF
authors.lastname: Bonner
authors.forename: William M
authors.initials: WM
authors.lastname: Bonner
authors.forename: André
authors.initials: A
authors.lastname: Nussenzweig
mesh_terms: D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000235:genetics*; D002843:Chromatin / Q000235:genetics*; D004249:DNA Damage / Q000235:genetics* / Q000528:radiation effects; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D005057:Eukaryotic Cells / Q000378:metabolism*; D006657:Histones / Q000172:deficiency* / Q000235:genetics; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics; D010766:Phosphorylation; D015398:Signal Transduction / Q000235:genetics
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D009687:Nuclear Proteins