Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P16104 (H2AX)
 3,930 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Chk1 kinase is highly conserved from yeast to humans and is well known to function in the cell cycle checkpoint induced by genotoxic or replication stress. The activation of Chk1 is achieved by ATR-dependent phosphorylation with the aid of additional factors. Robust genotoxic insults induce apoptosis instead of the cell cycle checkpoint, and some of the components in the ATR-Chk1 pathway are cleaved by active caspases, although it has been unclear whether the attenuation of the ATR-Chk1 pathway has some role in apoptosis induction. Here we show that Chk1 is activated by caspase-dependent cleavage when the cells undergo apoptosis. Treatment of chicken DT40 cells with various genotoxic agents, UV light, etoposide, or camptothecin induced Chk1 cleavage, which was inhibited by a pan-caspase inhibitor, benzyloxycarbonyl-VAD-fluoromethyl ketone. The cleavage of Chk1 was similarly observed in human Jurkat cells treated with a non-genotoxic apoptosis inducer, staurosporine. We have determined the cleavage site(s), Asp-299 in chicken and Asp-299 and Asp-351 in human cells. We further show that a truncated form of human Chk1 mimicking the N-terminal cleavage fragment (residues 1-299) possesses strikingly elevated kinase activity. Moreover, the ectopic expression of Chk1-(1-299) in human U2OS cells induces abnormal nuclear morphology with localized chromatin condensation and phosphorylation of histone H2AX. These results suggest that Chk1 is activated by caspase-mediated cleavage during apoptosis and might be implicated in enhancing apoptotic reactions rather than attenuating the ATR-Chk1 pathway.
J Biol Chem 2008 Sep 12
PMID:Cleavage-mediated activation of Chk1 during apoptosis. 1855 May 33

It is well known that the positively charged polyamines have a DNA-stabilizing function and that polyamine depletion alters chromatin function. We have previously shown that polyamine depletion causes an S phase prolongation, and others have shown that there is an accumulation of Okazaki-like fragments in polyamine-depleted cells. In the present study, we have used the comet assay to investigate polyamine depletion-induced DNA strand breaks. Three breast cancer cell lines and one normal-like breast cell line were treated with the polyamine analogue N(1),N(11)-diethylnorspermine or with the polyamine biosynthesis inhibitor 4-amidinoindan-1-one 2'-amidinohydrazone (CGP 48664). The comet assay showed that polyamine depletion resulted in DNA strand breaks. We also show that these DNA strand breaks occurred in cells where there was no expression of gamma-H2AX, which is a marker of DNA double-strand breaks. Thus, our conclusion is that polyamine depletion causes DNA single-strand breaks, which may be the cause for the observed delay in S phase progression.
DNA Cell Biol 2008 Sep
PMID:Polyamine depletion with two different polyamine analogues causes DNA damage in human breast cancer cell lines. 1855 80

Werner syndrome (WS) is a human genetic disorder characterized by extensive clinical features of premature aging. Ataxia-telengiectasia (A-T) is a multisystem human genomic instability syndrome that includes premature aging in some of the patients. WRN and ATM, the proteins defective in WS and A-T, respectively, play significant roles in the maintenance of genomic stability and are involved in several DNA metabolic pathways. A role for WRN in DNA repair has been proposed; however, this study provides evidence that WRN is also involved in ATM pathway activation and in a S-phase checkpoint in cells exposed to DNA interstrand cross-link-induced double-strand breaks. Depletion of WRN in such cells by RNA interference results in an intra-S checkpoint defect, and interferes with activation of ATM as well as downstream phosphorylation of ATM target proteins. Treatment of cells under replication stress with the ATM kinase inhibitor KU 55933 results in a S-phase checkpoint defect similar to that observed in WRN shRNA cells. Moreover, gamma H2AX levels are higher in WRN shRNA cells than in control cells 6 and 16 h after exposure to psoralen DNA cross-links. These results suggest that WRN and ATM participate in a replication checkpoint response, in which WRN facilitates ATM activation in cells with psoralen DNA cross-link-induced collapsed replication forks.
Mol Biol Cell 2008 Sep
PMID:WRN is required for ATM activation and the S-phase checkpoint in response to interstrand cross-link-induced DNA double-strand breaks. 1859 39

Mouse embryonic stem (mES) cells will give rise to all of the cells of the adult mouse, but they failed to rejoin half of the DNA double-strand breaks (dsb) produced by high doses of ionizing radiation. A deficiency in DNA-PK(cs) appears to be responsible since mES cells expressed <10% of the level of mouse embryo fibroblasts (MEFs) although Ku70/80 protein levels were higher than MEFs. However, the low level of DNA-PK(cs) found in wild-type cells appeared sufficient to allow rejoining of dsb after doses <20Gy even in G1 phase cells. Inhibition of DNA-PK(cs) with wortmannin and NU7026 still sensitized mES cells to radiation confirming the importance of the residual DNA-PK(cs) at low doses. In contrast to wild-type cells, mES cells lacking H2AX, a histone protein involved in the DNA damage response, were radiosensitive but they rejoined double-strand breaks more rapidly. Consistent with more rapid dsb rejoining, H2AX(-/-) mES cells also expressed 6 times more DNA-PK(cs) than wild-type mES cells. Similar results were obtained for ATM(-/-) mES cells. Differentiation of mES cells led to an increase in DNA-PK(cs), an increase in dsb rejoining rate, and a decrease in Ku70/80. Unlike mouse ES, human ES cells were proficient in rejoining of dsb and expressed high levels of DNA-PK(cs). These results confirm the importance of homologous recombination in the accurate repair of double-strand breaks in mES cells, they help explain the chromosome abnormalities associated with deficiencies in H2AX and ATM, and they add to the growing list of differences in the way rodent and human cells deal with DNA damage.
DNA Repair (Amst) 2008 Sep 01
PMID:Mouse but not human embryonic stem cells are deficient in rejoining of ionizing radiation-induced DNA double-strand breaks. 1860 49

The cellular activity of Yondelis (trabectedin, Ecteinascidin 743, Et743) is known to depend on transcription-coupled nucleotide excision repair (TCR). However, the subsequent cellular effects of Et743 are not fully understood. Here we show that Et743 induces both transcription- and replication-coupled DNA double-strand breaks (DSBs) that are detectible by neutral COMET assay and as gamma-H2AX foci that colocalize with 53BP1, Mre11, Ser(1981)-pATM, and Thr(68)-pChk2. The transcription coupled-DSBs (TC-DSBs) induced by Et743 depended both on TCR and Mre11-Rad50-Nbs1 (MRN) and were associated with DNA-PK-dependent gamma-H2AX foci. In contrast to DNA-PK, ATM phosphorylated H2AX both in NER-proficient and -deficient cells, but its full activation was dependent on H2AX as well as DNA-PK, suggesting a positive feedback loop: DNA-PK-gamma-H2AX-ATM. Knocking-out H2AX or inactivating DNA-PK reduced Et743's antiproliferative activity, whereas ATM and MRN tended to act as survival factors. Our results highlight the interplays between ATM and DNA-PK and their impacts on H2AX phosphorylation and cell survival. They also suggest that gamma-H2AX may serve as a biomarker in patients treated with Et743 and that molecular profiling of tumors for TCR, MRN, ATM, and DNA-PK might be useful to anticipate tumor response to Et743 treatment.
Mol Biol Cell 2008 Sep
PMID:Transcription-coupled DNA double-strand breaks are mediated via the nucleotide excision repair and the Mre11-Rad50-Nbs1 complex. 1863 84

Radiation-induced bystander effects (RIBE) have been demonstrated to occur widely in various cell lines. However, very little data is available on the genotoxic effects of RIBE combined with other factor(s). We reported previously that with a low dose of alpha-particle irradiation, the fraction of gamma-H2AX foci-positive cells in non-irradiated bystander cells was significantly increased under elevated NaCl culture conditions. In this study, we further investigated the functional role of NaCl in the enhancement of RIBE using a specially designed co-culture system and micronucleus (MN) test. It was shown that the MN frequency was not increased significantly by elevated NaCl (9.0 g/L) alone or by medium exposure. However, with 1.0 cGy alpha-particle irradiation, the induced MN frequency increased significantly in both irradiated and non-irradiated bystander regions. Additional studies showed that elevated NaCl made the non-irradiated bystander cells more vulnerable to bystander factors. Furthermore, it was found that the induced MN frequency in cells both in irradiated and non-irradiated bystander regions was weakened when the hypertonic medium was changed to normotonic medium for 2h before irradiation. Such observations were quite similar to the co-effect of NaCl and hydrogen peroxide (H(2)O(2)), indicating that elevated NaCl might sensitize non-irradiated cells to bystander factors-induced oxidative stress.
Mutat Res 2008 Sep 26
PMID:Radiation-induced bystander effects enhanced by elevated sodium chloride through sensitizing cells to bystander factors. 1864 Jan 33

Physical and chemical agents that induce DNA double-strand breaks (DSBs) are among the most potent mutagens. The mammalian cell response to DSB comprises a highly co-ordinated, yet complex network of proteins that have been categorized as sensors, signal transducers, mediators and effectors of damage and repair. While this provides an accessible classification system, review of the literature indicates that many proteins satisfy the criteria of more than one category, pointing towards a series of highly co-operative pathways with overlapping function. In summary, the MRE11-NBS1-RAD50 complex is necessary for achieving optimal activation of ataxia-telangiectasia-mutated (ATM) kinase, which catalyses a phosphorylation-mediated signal transduction cascade. Among the subset of proteins phosphorylated by ATM are histone H2AX (H2AX), mediator of damage checkpoint protein 1, nibrin (NBS1), P53-binding protein 1 and breast cancer protein 1, all of which subsequently redistribute into DSB-containing sub-nuclear compartments. Post-translational modification of DSB responding proteins achieves a rapid and reversible change in protein behaviour and mediates damage-specific interactions, hence imparting a high degree of vigilance to the cell. This review highlights events fundamental in maintaining genetic integrity with emphasis on early stages of the DSB response.
Mutagenesis 2008 Sep
PMID:Early events in the mammalian response to DNA double-strand breaks. 1864 34

In mammalian cells, the H2AX histone is rapidly phosphorylated upon the induction of DNA double strand breaks and promotes their repair, which is required for preserving genomic integrity. Etoposide is an inhibitor of DNA topoisomerase II, which causes DNA breaks and induces H2AX phosphorylation. To elucidate whether H2AX may affect cellular sensitivity to etoposide, we studied the response to this agent in immortalized embryonic fibroblasts derived from H2AX knockout mice. Clonogenic assays in cells treated with the drug revealed a greater sensitivity of H2AX null cells compared to wild-type cells, possibly due to the persistence of a higher number of DNA breaks, as detected with the comet assay. In both cell lines, etoposide induced micronuclei formation and nuclear fragmentation; however, in H2AX deficient cells nuclear fragmentation was observed at a lower drug concentration. Flow cytometric analysis showed that etoposide induced a G2/M cell cycle arrest in both cell lines, which occurred at lower drug concentrations in H2AX deficient cells. G2/M arrest was paralleled by an accumulation of cyclin A and cyclin B1, suggesting that treated cells are not able to complete cell cycle correctly and undergo cell death. Taken together, our observations suggest that H2AX takes part to the cellular response to etoposide and confirm its role in the maintenance of genome stability.
Int J Oncol 2008 Sep
PMID:Loss of histone H2AX increases sensitivity of immortalized mouse fibroblasts to the topoisomerase II inhibitor etoposide. 1869 93

Although the hydroxymethylglutaryl-coenzyme A reductase inhibitors (statins) are widely used in atherosclerosis to reduce serum cholesterol, statins have multiple other effects, including direct effects on cells of the vessel wall. Recently, DNA damage, including telomere shortening, has been identified in vascular smooth muscle cells (VSMCs) in human atherosclerosis. Although statins reduce DNA damage in vitro, the mechanisms by which they might protect DNA integrity in VSMCs are unknown. We show that human atherosclerotic plaque VSMCs exhibit increased levels of double-stranded DNA breaks and basal activation of DNA repair pathways involving ataxia telangiectasia-mutated (ATM) and the histone H2AX in vivo and in vitro. Oxidant stress induced DNA damage and activated DNA repair pathways in VSMCs. Statin treatment did not reduce oxidant stress or DNA damage but markedly accelerated DNA repair. Accelerated DNA repair required both the Nijmegen breakage syndrome (NBS)-1 protein and the human double minute protein Hdm2, accompanied by phosphorylation of Hdm2, dissociation of NBS-1 and Hdm2, inhibition of NBS-1 degradation, and accelerated phosphorylation of ATM. Statin treatment reduced VSMC senescence and telomere attrition in culture, accelerated DNA repair and reduced apoptosis in vivo after irradiation, and reduced ATM/ATR (ATM and Rad3-related) activity in atherosclerosis. We conclude that statins activate a novel mechanism of accelerating DNA repair, dependent on NBS-1 stabilization and Hdm2. Statin treatment may delay cell senescence and promote DNA repair in atherosclerosis.
Circ Res 2008 Sep 26
PMID:Statins use a novel Nijmegen breakage syndrome-1-dependent pathway to accelerate DNA repair in vascular smooth muscle cells. 1872 44

Bisphenol A (BPA) and chlorinated bisphenol A (ClBPAs) were detected in wastewater from waste paper recycling plants. Previously, we showed that exposure to UV augmented the toxicity of ClBPAs [Mutou (2006) Environ. Toxicol. Pharmacol. 21, 283- 289 and Mutou (2008) Toxicol. in Vitro 22, 864- 872]. BPA and ClBPAs are exposed to sunlight in the environment; however, research concerning the change of toxicity during their photodegradation is scarce, especially for ClBPAs. In this study using human keratinocytes and skin fibroblasts, we found that 3,3'-dichlorobisphenol A (3,3'-diClBPA) exposed to UVB induces phosphorylation of histone H2AX, the event considered to be a marker of formation of DNA double strand breaks. The cells treated with the UVB-exposed 3,3'-diClBPA formed clear foci of phosphorylated histone H2AX in the nucleus. Unchlorinated BPA caused no phosphorylation of histone H2AX even when exposed to high doses of UVB (approximately 200 J/cm(2)). HPLC analysis clarified that several compounds with increased hydrophilicity were produced from 3,3'-diClBPA by UVB irradiation, not from BPA, suggesting the chlorinated chemical structure to be important for the degradation and generation of products related to the phosphorylation of histone H2AX. In separated peaks of 3,3'-diClBPA exposed to UVB, peak fluctuation of 3-hydroxybisphenol A (3-OHBPA) was consistent with the UVB dose-dependent appearance of phosphorylated histone H2AX. We suspected that some oxidized BPA involving 3-OHBPA produced by UVB irradiation contributed to the phosphorylation. Considering that the phosphorylation of histone H2AX is required for maintaining the genome's stability and the repair of DNA, attention to photoproducts from chlorinated compounds is important for the risk evaluation of chemicals.
Chem Res Toxicol 2008 Sep
PMID:UVB-exposed chlorinated bisphenol A generates phosphorylated histone H2AX in human skin cells. 1872 29


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