title: Genome-wide reorganization of histone H2AX toward particular fragile sites on cell activation.
abstract: γH2AX formation by phosphorylation of the histone variant H2AX is the key process in the repair of DNA lesions including those arising at fragile sites under replication stress. Here we demonstrate that H2AX is dynamically reorganized to preoccupy γH2AX hotspots on increased replication stress by activated cell proliferation and that H2AX is enriched in aphidicolin-induced replisome stalling sites in cycling cells. Interestingly, H2AX enrichment was particularly found in genomic regions that replicate in early S phase. High transcription activity, a hallmark of early replicating fragile sites, was a determinant of H2AX localization. Subtelomeric H2AX enrichment was also attributable to early replication and high gene density. In contrast, late replicating and infrequently transcribed regions, including common fragile sites and heterochromatin, lacked H2AX enrichment. In particular, heterochromatin was inaccessible to H2AX incorporation, maybe partly explaining the cause of mutation accumulation in cancer heterochromatin. Meanwhile, H2AX in actively dividing cells was intimately colocalized with INO80. INO80 silencing reduced H2AX levels, particularly at the INO80-enriched sites. Our findings suggest that active DNA replication is accompanied with the specific localization of H2AX and INO80 for efficient damage repair or replication-fork stabilization in actively transcribed regions.
authors.affiliation: Research Institute of Bioinformatics, Omicsis, Inc., Daejeon 305-333, Korea, Department of Bio and Brain Engineering, KAIST, Daejeon 305-701, Korea, Graduate School of Medical Science and Engineering, KAIST, Daejeon 305-701, Korea, Medical Genomics Research Center, KRIBB, Daejeon 305-333, Korea and Department of Life Science, Ewha Womans University, Seoul 120-750, Korea.
authors.forename: Jungmin
authors.initials: J
authors.lastname: Seo
authors.forename: Kwoneel
authors.initials: K
authors.lastname: Kim
authors.forename: Dong-Yeop
authors.initials: DY
authors.lastname: Chang
authors.forename: Ho-Bum
authors.initials: HB
authors.lastname: Kang
authors.forename: Eui-Cheol
authors.initials: EC
authors.lastname: Shin
authors.forename: Jongbum
authors.initials: J
authors.lastname: Kwon
authors.forename: Jung Kyoon
authors.initials: JK
authors.lastname: Choi
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D049109:Cell Proliferation; D043283:Chromosome Fragile Sites; D004265:DNA Helicases / Q000032:analysis; D004261:DNA Replication; D042522:DNA Replication Timing; D004268:DNA-Binding Proteins; D015894:Genome, Human; D006367:HeLa Cells; D006657:Histones / Q000032:analysis*; D006801:Humans; D009707:Nucleosomes / Q000737:chemistry
chemical_list: D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D009707:Nucleosomes; D000074183:ATPases Associated with Diverse Cellular Activities; D004265:DNA Helicases; C524421:INO80 protein, human