title: Heterochromatin is refractory to gamma-H2AX modification in yeast and mammals.
abstract: Double-strand break (DSB) damage in yeast and mammalian cells induces the rapid ATM (ataxia telangiectasia mutated)/ATR (ataxia telangiectasia and Rad3 related)-dependent phosphorylation of histone H2AX (gamma-H2AX). In budding yeast, a single endonuclease-induced DSB triggers gamma-H2AX modification of 50 kb on either side of the DSB. The extent of gamma-H2AX spreading does not depend on the chromosomal sequences. DNA resection after DSB formation causes the slow, progressive loss of gamma-H2AX from single-stranded DNA and, after several hours, the Mec1 (ATR)-dependent spreading of gamma-H2AX to more distant regions. Heterochromatic sequences are only weakly modified upon insertion of a 3-kb silent HMR locus into a gamma-H2AX-covered region. The presence of heterochromatin does not stop the phosphorylation of chromatin more distant from the DSB. In mouse embryo fibroblasts, gamma-H2AX distribution shows that gamma-H2AX foci increase in size as chromatin becomes more accessible. In yeast, we see a high level of constitutive gamma-H2AX in telomere regions in the absence of any exogenous DNA damage, suggesting that yeast chromosome ends are transiently detected as DSBs.
authors.affiliation: Rosenstiel Center and Department of Biology, Brandeis University, Waltham, MA 02454, USA.
authors.forename: Jung-Ae
authors.initials: JA
authors.lastname: Kim
authors.forename: Michael
authors.initials: M
authors.lastname: Kruhlak
authors.forename: Farokh
authors.initials: F
authors.lastname: Dotiwala
authors.forename: André
authors.initials: A
authors.lastname: Nussenzweig
authors.forename: James E
authors.initials: JE
authors.lastname: Haber
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D033481:Chromosomes, Mammalian; D004249:DNA Damage; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D006570:Heterochromatin / Q000378:metabolism*; D006657:Histones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008322:Mammals / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*
chemical_list: D006570:Heterochromatin; D006657:Histones; C475961:gamma-H2AX protein, mouse