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.

Areca nut exposure increases secretion of tumor‐promoting cytokines in gingival fibroblasts that trigger DNA damage in oral keratinocytes

“…Further, the 8‐oxoG‐positive cells were reduced when cytokines in the CM were neutralized, suggesting that DNA damage has been triggered by cytokines released from AN‐exposed fibroblasts. As DNA DSB is one of the most deleterious forms of DNA damage and is accumulated in premalignant lesions as well as in OSCC,22, 37 the continuous formation of DNA DSB may contribute to genomic instability and consequently to carcinogenesis 34. In our study, the DNA DSB‐positive cells increased in cytokine‐treated IHOK compared to the nontreated controls.…”

“…To detect DNA damage caused by cytokines, the phospho‐Histone H2A.X rabbit monoclonal antibody (Cell Signaling Technology) was utilized22 and described in Table 3, Supporting Information. IHOK cells (1 × 10 4 ) were seeded in chamber slides and were treated with cytokines for 72 hr.…”

Isolation and cytogenetic characterization of zebrafish meiotic prophase I mutants

“…There is general agreement that the phosphorylation of H2A histones is dispensable for the initial recognition of DNA breaks and that its function is associated with the recruitment of repair factors to damaged DNA to facilitate repair efficiency (Celeste et al, 2003). Phosphorylated histone H2AX (g-H2AX) is a marker of DSBs in normal leptotene and zygotene spermatocytes, in the sex body, and in autosomal asynaptic chromatin in pachytene spermatocytes in mice (Mahadevaiah et al, 2001;Celeste et al, 2003).…”

“…Phosphorylated histone H2AX (g-H2AX) is a marker of DSBs in normal leptotene and zygotene spermatocytes, in the sex body, and in autosomal asynaptic chromatin in pachytene spermatocytes in mice (Mahadevaiah et al, 2001;Celeste et al, 2003). To better understand meiotic failure in the isa and imo zebrafish mutants, we examined the expression and localization patterns of g-H2AX in spermatocytes.…”

The role of histone acetylation versus DNA damage in drug-induced senescence and apoptosis

“…With the recent discovery that phosphorylation of the histone H2AX (g-H2AX) is associated with drug and irradiation-induced DNA double-strand breaks (DSBs), this molecule has been proposed as a mediator of DNA-damage-induced proliferation arrest. [6][7][8][9][10] Although this association has been observed in various cases, it does not exclude the possibility that proliferation arrest can occur independently of DNA damage. Since non-DNA targeting drugs can also inhibit proliferation, [11][12][13] it is plausible that cellular processes other than DNA damage may activate signaling pathways leading to proliferation arrest.…”