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)

p53 binding protein 1 (53BP1), a protein proposed to function as a transcriptional coactivator of the p53 tumor suppressor, has BRCT domains with high homology to the Saccharomyces cerevisiae Rad9p DNA damage checkpoint protein. To examine whether 53BP1 has a role in the cellular response to DNA damage, we probed its intracellular localization by immunofluorescence. In untreated primary cells and U2OS osteosarcoma cells, 53BP1 exhibited diffuse nuclear staining; whereas, within 5-15 min after exposure to ionizing radiation (IR), 53BP1 localized at discreet nuclear foci. We propose that these foci represent sites of processing of DNA double-strand breaks (DSBs), because they were induced by IR and chemicals that cause DSBs, but not by ultraviolet light; their peak number approximated the number of DSBs induced by IR and decreased over time with kinetics that parallel the rate of DNA repair; and they colocalized with IR-induced Mre11/NBS and gamma-H2AX foci, which have been previously shown to localize at sites of DSBs. Formation of 53BP1 foci after irradiation was not dependent on ataxia-telangiectasia mutated (ATM), Nijmegen breakage syndrome (NBS1), or wild-type p53. Thus, the fast kinetics of 53BP1 focus formation after irradiation and the lack of dependency on ATM and NBS1 suggest that 53BP1 functions early in the cellular response to DNA DSBs.
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PMID:p53 binding protein 1 (53BP1) is an early participant in the cellular response to DNA double-strand breaks. 1113 68

Telomeres cap the ends of eukaryotic chromosomes and prevent them from being recognized as DNA breaks. We have shown that certain DNA damage responses induced during senescence and, at times of telomere uncapping, also can be induced by treatment of cells with small DNA oligonucleotides homologous to the telomere 3' single-strand overhang (T-oligos), implicating this overhang in generation of these telomere-based damage responses. Here, we show that T-oligo-treated fibroblasts contain gammaH2AX foci and that these foci colocalize with telomeres. T-oligos with nuclease-resistant 3' ends are inactive, suggesting that a nuclease initiates T-oligo responses. We therefore examined WRN, a 3'-->5' exonuclease and helicase mutated in Werner syndrome, a disorder characterized by aberrant telomere maintenance, premature aging, chromosomal rearrangements, and predisposition to malignancy. Normal fibroblasts and U20S osteosarcoma cells rendered deficient in WRN showed reduced phosphorylation of p53 and histone H2AX in response to T-oligo treatment. Together, these data demonstrate a role for WRN in processing of telomeric DNA and subsequent activation of DNA damage responses. The T-oligo model helps define the role of WRN in telomere maintenance and initiation of DNA damage responses after telomere disruption.
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PMID:A role for WRN in telomere-based DNA damage responses. 1701 33

Checkpoint adaptation was originally defined in yeast as the ability to divide despite the presence of damaged DNA. An important unanswered question is whether checkpoint adaptation also occurs in human cells. Here, we show that following the ionizing radiation-induced G(2) checkpoint, human osteosarcoma cells entered mitosis with gamma-H2AX foci, a marker for unrepaired DNA double-strand breaks. Exit from the G(2) checkpoint was accelerated by inhibiting the checkpoint kinase 1 (Chk1) and delayed by overexpressing wild-type Chk1 or depleting the Polo-like kinase 1 (Plk1). Chk1 and Plk1 controlled this process, at least partly, via independent signaling pathways. Our results suggest that human cells are able to exit the checkpoint arrest and divide before the damage has been fully repaired. Such cell division in the presence of damaged DNA may be detrimental for genetic stability and could potentially contribute to cancer development.
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PMID:Adaptation to the ionizing radiation-induced G2 checkpoint occurs in human cells and depends on checkpoint kinase 1 and Polo-like kinase 1 kinases. 1707 42

The forkhead box M1 (FoxM1) transcription factor regulates expression of cell cycle genes essential for DNA replication and mitosis during organ repair and cancer progression. Here, we demonstrate that FoxM1-deficient (-/-) mouse embryonic fibroblasts and osteosarcoma U2OS cells depleted in FoxM1 levels by small interfering RNA transfection display increased DNA breaks, as evidenced by immunofluorescence focus staining for phosphospecific histone H2AX. FoxM1-deficient cells also exhibit stimulation of p53 transcriptional activity, as evidenced by increased expression of the p21(cip1) gene. FoxM1-deficient cells display reduced expression of the base excision repair factor X-ray cross-complementing group 1 (XRCC1) and breast cancer-associated gene 2 (BRCA2), the latter of which is involved in homologous recombination repair of DNA double-strand breaks. Furthermore, FoxM1 protein is phosphorylated by checkpoint kinase 2 (Chk2) in response to DNA damage. This phosphorylation of FoxM1 on serine residue 361 caused increased stability of the FoxM1 protein with corresponding increased transcription of XRCC1 and BRCA2 genes, both of which are required for repair of DNA damage. These results identify a novel role for FoxM1 in the transcriptional response during DNA damage/checkpoint signaling and show a novel mechanism by which Chk2 protein regulates expression of DNA repair enzymes.
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PMID:Chk2 mediates stabilization of the FoxM1 transcription factor to stimulate expression of DNA repair genes. 1710 82

We have recently shown that thymoquinone (TQ) is an antineoplastic drug that induces p53-dependent apoptosis in human colon cancer cells. This study evaluated the antiproliferative and pro-apoptotic effects of TQ in two human osteosarcoma cell lines with different p53 mutation status. TQ decreased cell survival dose-dependently and, more significantly, in p53-null MG63 cells (IC(50) = 17 muM) than in p53-mutant MNNG/HOS cells (IC(50) = 38 muM). Cell viability was reduced more selectively in MG63 tumor cells than in normal human osteoblasts. Flow cytometric analysis showed that TQ induced a much greater increase in the PreG(1) (apoptotic) cell population, but no cell cycle arrest in MG63. G(2)/M arrest in MNNG/HOS cells was associated with p21(WAF1) upregulation. Using three DNA damage assays, TQ was confirmed to result in a significantly greater extent of apoptosis in p53 null MG63 cells. Although the Bax/Bcl-2 ratios were not differentially modulated in both cell lines, the mitochondrial pathway appeared to be involved in TQ-induced apoptosis in MG63 by showing the cleavage of caspases-9 and -3. Oxidative stress and mitochondrial O(2)(*-) generation in isolated rat mitochondria were enhanced by TQ as measured by the dose-dependent reduction in aconitase enzyme activity and Amplex Red oxidation respectively. TQ-induced oxidative damage, reflected by an increase in gamma-H2AX foci and increased protein expression levels of gamma-H2AX and the DNA repair enzyme, NBS1, was more pronounced in MNNG/HOS than in MG63. We suggest that the resistance of MNNG/HOS cells to drug-induced apoptosis is caused by the up-regulation of p21(WAF1) by the mutant p53 (transcriptional activity was shown by p53 siRNA treatment) which induces cell cycle arrest and allows to repair DNA damage. Collectively, these findings show that TQ induces p53-independent apoptosis in human osteosarcoma cells. As the loss of p53 function is frequently observed in osteosarcoma patients, our data suggest the potential clinical usefulness of TQ for the treatment of these malignancies.
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PMID:Lack of p53 augments thymoquinone-induced apoptosis and caspase activation in human osteosarcoma cells. 1721 78

The forkhead associated (FHA) domain-containing protein Smad nuclear interacting protein 1 (SNIP1) has multiple cellular functions, including the ability to interact with DNA-binding transcription factors and transcriptional coactivators. Moreover, we have demonstrated previously that SNIP1 regulates cyclin D1 expression and promoter activity. Here, we identify a new function for SNIP1 as a regulator of ATR checkpoint kinase-dependent pathways in human U-2 OS osteosarcoma cells: SNIP1 is required for p53 induction in response to ultraviolet light treatment and selectively regulates the phosphorylation of known ATR target proteins, including p53, Chk1 and the histone variant H2AX. These activities are independent of its ability to regulate cyclin D1 expression. Significantly, SNIP1 is also required for ATR-dependent functions of the human p14(ARF) tumour suppressor, including its ability to modulate the activity of the RelA(p65) NF-kappaB subunit. This, together with its other described functions, suggests that SNIP1 could have an important role during tumorigenesis and cancer therapy.
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PMID:Regulation of ATR-dependent pathways by the FHA domain containing protein SNIP1. 1726 16

Osteosarcoma is one of the most common primary malignant tumors of the bone in children and adolescents. Some patients continue to have a poor prognosis, as they have metastatic disease and frequent occurrence of drug resistance. Zoledronate is a nitrogen-containing bisphosphonate that has been used for the treatment of hypercalcemia and bone metastasis, because it induces apoptosis in osteoclasts and tumor cells by inhibiting the isoprenylation of intracellular small G proteins. Besides inhibiting isoprenylation, little is known about the manner by which bisphosphonates inhibit cellular proliferation and induce apoptosis. This prompted us to investigate the inhibitory effects of zoledronate in human osteosarcoma cell lines, HOS and MG63. HOS cells accumulated in S phase around 6 h after treatment with 10 microM zoledronate, followed by apoptosis. When HOS cells were treated with zoledronate, ATM kinase and its substrate, check-point kinase (Chk)1, were phosphorylated. Zoledronate also induced phosphorylation of cdc25a (Thr506) in HOS cells, which is a substrate of Chk1, and its phosphorylation is known to be critical for S phase arrest. Following treatment with zoledronate, phosphorylated histone H2AX (gamma-H2AX) displayed patterns of nuclear foci in HOS cells. As gamma-H2AX accumulates at dsDNA breaks, these results demonstrate that zoledronate induced DNA damage and S phase arrest, accompanied by activation of the ATM/Chk1/cdc25 pathway in a human osteosarcoma cell line.
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PMID:Zoledronate-induced S phase arrest and apoptosis accompanied by DNA damage and activation of the ATM/Chk1/cdc25 pathway in human osteosarcoma cells. 1761 84

Alkaloid berberine is widely used for the treatment of diarrhea and other diseases. Many laboratory studies showed that it exhibits anti-proliferative activity against a wide spectrum of cancer cells in culture. In this report we studied the mechanisms underlying the inhibitory effects of berberine on human osteosarcoma cells and on normal osteoblasts. The inhibition was largely attributed to cell cycle arrest at G1 and G2/M, and to a less extent, to apoptosis. The G1 arrest was dependent on p53, as G1 arrest was abolished in p53-deficient osteosarcoma cells. The induction of G1 arrest and apoptosis was accompanied by a p53-dependent up-regulation of p21 and pro-apoptotic genes. However, the G2/M arrest could be induced by berberine regardless of the status of p53. Interestingly, DNA double-strand breaks, as measured by the phosphorylation of H2AX, were remarkably accumulated in berberine-treated cells in a dose-dependent manner. Thus, one major mechanism by which berberine exerts its growth-inhibitory effect is to inflict genomic lesions on cells, which in turn trigger the activation of p53 and the p53-dependent cellular responses including cell cycle arrest and apoptosis.
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PMID:Berberine induces p53-dependent cell cycle arrest and apoptosis of human osteosarcoma cells by inflicting DNA damage. 1915 33

Altered centrosome numbers are seen in tumor cells in response to DNA damaging treatments and are hypothesised to contribute to cancer development. The mechanism by which the centrosome and chromosome cycles become disconnected after DNA damage is not yet clear. Here, we show that centrosome amplification occurs after ionising radiation (IR) in chicken DT40 cells that lack DNA-PK, Ku70, H2AX, Xpa, and Scc1, demonstrating that these activities are not required for centrosome amplification. We show that inhibition of topoisomerase II induces Chk1-dependent centrosome amplification, a similar response to that seen after IR. In the immortalised, nontransformed hTERT-RPE1 line, we observed centriole splitting, followed by dose-dependent centrosome amplification, after IR. We found that IR results in the formation of single, not multiple, daughter centrioles during centrosome amplification in U2OS osteosarcoma cells. Analysis of BRCA1 and BRCA2 mutant tumor cells showed high levels of centriole splitting in the absence of any treatment. IR caused pronounced levels of centrosome amplification in BRCA1 mutant breast cancer cells. These data show that centrosome amplification occurs after different forms of DNA damage in chicken cells, in nontransformed human cells and in human tumor cell lines, indicating that this is a general response to DNA damaging treatments. Together, our data suggest that centriole splitting is a key step in potentiation of the centrosome amplification that is a general response to DNA damage.
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PMID:Centriole separation in DNA damage-induced centrosome amplification. 1927 69

Resveratrol decreases cancer risk and improves health of laboratory animals. However, it can also promote genomic instability. Part of the beneficial activity of resveratrol may result from the activation of SIRT1 deacetylase. We examined how resveratrol influenced the growth of human cancer cell lines of different origin: osteosarcoma (U-2 OS) and lung adenocarcinoma (A549) and how it modulated the expression as well as the localization of key proteins, involved in DNA repair and cell cycle regulation. Resveratrol-induced growth arrest was associated with signs of stress-induced senescence. Differential expression of BRCA1, cyclin B1, pRb and p21 in U-2 OS and A549 cells indicates that resveratrol can engage various molecular mechanisms to arrest cell cycle progression. In subset of U-2 OS cells, the upregulated BRCA1 formed foci closely associated with WRN and the telomeric protein (TRF1). Moreover, resveratrol induced telomeric instability in U-2 OS cells and the activation of DNA damage signaling in both cell lines, manifested as the phosphorylation of histone H2AX at serine 139 and of p53 at serines 15 and 37. Our data are consistent with the hypothesis that resveratrol inhibits cell growth and induces senescence by altering DNA metabolism.
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PMID:Resveratrol induces senescence-like growth inhibition of U-2 OS cells associated with the instability of telomeric DNA and upregulation of BRCA1. 1955 22


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