Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Irofulven (6-hydroxymethylacylfulvene, HMAF, MGI 114) is one of a new class of anticancer agents that are semisynthetic derivatives of the mushroom toxin illudin S. Preclinical studies and clinical trials have demonstrated that irofulven is effective against several tumor types. Mechanisms of action studies indicate that irofulven induces DNA damage, MAPK activation, and apoptosis. In this study we found that in ovarian cancer cells, CHK2 kinase is activated by irofulven while CHK1 kinase is not activated even when treated at higher concentrations of the drug. By using GM00847 human fibroblast expressing tetracycline-controlled, FLAG-tagged kinase-dead ATR (ATR.kd), it was demonstrated that ATR kinase does not play a major role in irofulven-induced CHK2 activation. Results from human fibroblasts proficient or deficient in ATM function (GM00637 and GM05849) indicated that CHK2 activation by irofulven is mediated by the upstream ATM kinase. Phosphorylation of ATM on Ser(1981), which is critical for kinase activation, was observed in ovarian cancer cell lines treated with irofulven. RNA interference results confirmed that CHK2 activation was inhibited after introducing siRNA for ATM. Finally, experiments done with human colon cancer cell line HCT116 and its isogenic CHK2 knockout derivative; and experiments done by expressing kinase-dead CHK2 in an ovarian cancer cell line demonstrated that CHK2 activation contributes to irofulven-induced S phase arrest. In addition, it was shown that NBS1, SMC1, and p53 were phosphorylated in an ATM-dependent manner, and p53 phosphorylation on serine 20 is dependent on CHK2 after irofulven treatment. In summary, we found that the anticancer agent, irofulven, activates the ATM-CHK2 DNA damage-signaling pathway, and CHK2 activation contributes to S phase cell cycle arrest induced by irofulven.
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PMID:ATM-dependent CHK2 activation induced by anticancer agent, irofulven. 1526 3

The requirement for the serine/threonine protein kinase ATM in coordinating the cellular response to DNA damage induced by ionizing radiation has been studied extensively. Many of the anti-tumor chemotherapeutics in clinical use today cause DNA double strand breaks; however, few have been evaluated for their ability to modulate ATM-mediated pathways. We have investigated the requirement for ATM in the cellular response to doxorubicin, a topoisomerase II-stabilizing drug. Using several ATM-proficient and ATM-deficient cell lines, we have observed ATM-dependent nuclear accumulation of p53 and ATM-dependent phosphorylation of p53 on seven serine residues. This was accompanied by an increased binding of p53 to its cognate binding site, suggesting transcriptional competency of p53 to activate its downstream effectors. Treatment of cells with doxorubicin led to the phosphorylation of histone H2AX on serine 139 with dependence on ATM for the initial response. Doxorubicin treatment also stimulated ATM autophosphorylation on serine 1981 and the ATM-dependent phosphorylation of numerous effectors in the ATM-signaling pathway, including Nbs1 (Ser(343)), SMC1 (Ser(957)), Chk1 (Ser(317) and Ser(345)), and Chk2 (Ser(33/35) and Thr(68)). Although generally classified as a topoisomerase II-stabilizing drug that induces DNA double strand breaks, doxorubicin can intercalate DNA and generate reactive oxygen species. Pretreatment of cells with the superoxide scavenger ascorbic acid had no effect on the doxorubicin-induced phosphorylation and accumulation of p53. In contrast, preincubation of cells with the hydroxyl radical scavenger, N-acetylcysteine, significantly attenuated the doxorubicin-mediated phosphorylation and accumulation of p53, p53-DNA binding, and the phosphorylation of H2AX, Nbs1, SMC1, Chk1, and Chk2, suggesting that hydroxyl radicals contribute to the doxorubicin-induced activation of ATM-dependent pathways.
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PMID:Doxorubicin activates ATM-dependent phosphorylation of multiple downstream targets in part through the generation of reactive oxygen species. 1548 21

The serine/threonine protein kinase ATM signals to cell cycle and DNA repair components by phosphorylating downstream targets such as p53, CHK2, NBS1, and BRCA1. Mutation of ATM occurs in the human autosomal recessive disorder ataxia-telangiectasia, which is characterized by hypersensitivity to ionizing radiation and a failure of cells to arrest the cell cycle after the induction of DNA double-strand breaks. It has thus been proposed that ATM inhibition would cause cellular radio- and chemosensitization. Through screening a small molecule compound library developed for the phosphatidylinositol 3'-kinase-like kinase family, we identified an ATP-competitive inhibitor, 2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one (KU-55933), that inhibits ATM with an IC(50) of 13 nmol/L and a Ki of 2.2 nmol/L. KU-55933 shows specificity with respect to inhibition of other phosphatidylinositol 3'-kinase-like kinases. Cellular inhibition of ATM by KU-55933 was demonstrated by the ablation of ionizing radiation-dependent phosphorylation of a range of ATM targets, including p53, gammaH2AX, NBS1, and SMC1. KU-55933 did not show inhibition of UV light DNA damage induced cellular phosphorylation events. Exposure of cells to KU-55933 resulted in a significant sensitization to the cytotoxic effects of ionizing radiation and to the DNA double-strand break-inducing chemotherapeutic agents, etoposide, doxorubicin, and camptothecin. Inhibition of ATM by KU-55933 also caused a loss of ionizing radiation-induced cell cycle arrest. By contrast, KU-55933 did not potentiate the cytotoxic effects of ionizing radiation on ataxia-telangiectasia cells, nor did it affect their cell cycle profile after DNA damage. We conclude that KU-55933 is a novel, specific, and potent inhibitor of the ATM kinase.
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PMID:Identification and characterization of a novel and specific inhibitor of the ataxia-telangiectasia mutated kinase ATM. 1560 86

Progression from G(1) to S is essential for polyomavirus DNA replication and depends on the interaction of large T with the retinoblastoma gene product pRb. This virus-induced replication pathway is accompanied by p53 activation resembling a DNA damage response (12). We sought to determine whether this pathway depends in part on activation of the ATM (ataxia telangiectasia mutated) kinase and whether the virus gains advantages from this pathway beyond that of entry into S. We show that polyomavirus infection activates the S- and G(2)-phase checkpoints in primary as well as established mouse cells. Infected cells undergo a prolonged S phase compared to uninfected serum-stimulated cells and show no evidence of a G(2)-->M transition before lytic death ensues. Infection is accompanied by increases in ATM activity in vitro and in the level of ATM-S1981-P in vivo. The incubation of infected cells with caffeine, a known ATM inhibitor, did not block entry into S but reduced the rate of viral compared to cellular DNA synthesis. Importantly, caffeine lowered the yields of viral DNA an average of 3- to 6-fold and those of infectious virus by as much as 10-fold. Virus yields were 10-fold lower in ATM (-/-) p53(-/-) than in ATM(+/+) p53(-/-) mouse embryo fibroblasts, indicating a p53-independent role of ATM in productive infection. Replacement of the normal SMC1 (structural maintenance of chromosomes, or cohesin) protein, a critical ATM substrate in the DNA repair pathway, with its phosphorylation mutant SMC1(S957AS966A) also lowered virus yields by roughly 90%. We suggest that polyomavirus activates and utilizes a component(s) of an ATM pathway of DNA repair to prolong S phase and aid its own replication.
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PMID:Induction and utilization of an ATM signaling pathway by polyomavirus. 1618 3

Double strand DNA breaks in the genome lead to the activation of the ataxia-telangiectasia mutated (ATM) kinase in a process that requires ATM autophosphorylation at serine-1981. ATM autophosphorylation only occurs if ATM is previously acetylated by Tip60. The activated ATM kinase phosphorylates proteins involved in arresting the cell cycle, including p53, and in repairing the DNA breaks. Chloroquine treatment and other manipulations that produce chromatin defects in the absence of detectable double strand breaks also trigger ATM phosphorylation and the phosphorylation of p53 in primary human fibroblasts, while other downstream substrates of ATM that are involved in the repair of DNA double strand breaks remain unphosphorylated. This raises the issue of whether ATM is constitutively activated in patients with genetic diseases that display chromatin defects. We examined lymphoblastoid cell lines (LCLs) generated from patients with different types of chromatin disorders: Immunodeficiency, Centromeric instability, Facial anomalies (ICF) syndrome, Coffin Lowry syndrome, Rubinstein Taybi syndrome and Fascioscapulohumeral Muscular Dystrophy. We show that ATM is phosphorylated on serine-1981 in LCLs derived from ICF patients but not from the other syndromes. The phosphorylated ATM in ICF cells did not phosphorylate the downstream targets NBS1, SMC1 and H2AX, all of which require the presence of double strand breaks. We demonstrate that ICF cells respond normally to ionizing radiation, ruling out the possibility that genetic deficiency in ICF cells renders activated ATM incapable of phosphorylating its downstream substrates. Surprisingly, p53 was also not phosphorylated in ICF cells or in chloroquine-treated wild type LCLs. In this regard the response to chromatin-altering agents differs between primary fibroblasts and LCLs. Our findings indicate that although phosphorylation at serine-1981 is essential in the activation of the ATM kinase, serine-1981 phosphorylation is insufficient to render ATM an active kinase towards downstream substrates, including p53.
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PMID:Constitutive phosphorylation of ATM in lymphoblastoid cell lines from patients with ICF syndrome without downstream kinase activity. 1642 3

Overexpression of the c-myc oncogene contributes to the development of a significant number of human cancers. In response to deregulated Myc activity, the p53 tumor suppressor is activated to promote apoptosis and inhibit tumor formation. Here we demonstrate that p53 induction in response to Myc overexpression requires the ataxia-telangiectasia mutated (ATM) kinase, a major regulator of the cellular response to DNA double-strand breaks. In a transgenic mouse model overexpressing Myc in squamous epithelial tissues, inactivation of Atm suppresses apoptosis and accelerates tumorigenesis. Deregulated Myc expression induces DNA damage in primary transgenic keratinocytes and the formation of gammaH2AX and phospho-SMC1 foci in transgenic tissue. These findings suggest that Myc overexpression causes DNA damage in vivo and that the ATM-dependent response to this damage is critical for p53 activation, apoptosis, and the suppression of tumor development.
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PMID:ATM promotes apoptosis and suppresses tumorigenesis in response to Myc. 1643 27

The Fanconi anemia-BRCA pathway of genes are frequently mutated or epigenetically repressed in human cancer. The proteins of this pathway play pivotal roles in DNA damage signaling and repair. Irofulven is one of a new class of anticancer agents that are analogues of mushroom-derived illudin toxins. Preclinical studies and clinical trials have shown that irofulven is effective against several tumor cell types. The exact nature of irofulven-induced DNA damage is not completely understood. Previously, we have shown that irofulven activates ATM and its targets, NBS1, SMC1, CHK2, and p53. In this study, we hypothesize that irofulven induces DNA double-strand breaks and FANCD2 may play an important role in modulating cellular responses and chemosensitivity in response to irofulven treatment. By using cells that are proficient or deficient for FANCD2, ATR, or ATM, we showed that irofulven induces FANCD2 monoubiquitination and nuclear foci formation. ATR is important in mediating irofulven-induced FANCD2 monoubiquitination. Furthermore, we showed that FANCD2 plays a critical role in maintaining chromosome integrity and modulating chemosensitivity in response to irofulven-induced DNA damage. Therefore, this study suggests that it might be clinically significant to target irofulven therapy to cancers defective for proteins of the Fanconi anemia-BRCA pathway.
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PMID:Fanconi anemia D2 protein confers chemoresistance in response to the anticancer agent, irofulven. 1717 19

Tumor suppressor gene BRCA1 is frequently mutated in familial breast and ovarian cancer. BRCA1 plays pivotal roles in maintaining genomic stability by interacting with numerous proteins in cell cycle control and DNA repair. Irofulven (6-hydroxymethylacylfulvene, HMAF, MGI 114, NSC 683863) is one of a new class of anticancer agents that are analogs of mushroom-derived illudin toxins. Preclinical studies and clinical trials have demonstrated that irofulven is effective against several tumor cell types. The exact nature of irofulven-induced DNA damage is not completely understood. We demonstrated previously that irofulven activates ATM and its targets, NBS1, SMC1, CHK2, and p53. In this study, we hypothesize that irofulven induces DNA double-strand breaks and that BRCA1 may affect chemosensitivity by controlling cell cycle checkpoints, DNA repair, and genomic stability in response to irofulven treatment. We observed that irofulven induces the formation of chromosome breaks and radials and the activation and foci formation of gamma-H2AX, BRCA1, and RAD51. We also provided evidence that irofulven induces the generation of DNA double-strand breaks. By using BRCA1-deficient or -proficient cells, we demonstrated that in response to irofulven, BRCA1 contributes to the control of S and G(2)/M cell cycle arrest and is critical for repairing DNA double-strand breaks and for RAD51-dependent homologous recombination. Furthermore, we found that BRCA1 deficiency results in increased chromosome damage and chemosensitivity after irofulven treatment.
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PMID:BRCA1 contributes to cell cycle arrest and chemoresistance in response to the anticancer agent irofulven. 1722 70

Poly(ADP-ribosyl)ation is a post-translational modification that is instantly stimulated by DNA strand breaks creating a unique signal for the modulation of protein functions in DNA repair and cell cycle checkpoint pathways. Here we report that lack of poly(ADP-ribose) synthesis leads to a compromised response to DNA damage. Deficiency in poly(ADP-ribosyl)ation metabolism induces profound cellular sensitivity to DNA-damaging agents, particularly in cells deficient for the protein kinase ataxia telangiectasia mutated (ATM). At the biochemical level, we examined the significance of poly(ADP-ribose) synthesis on the regulation of early DNA damage-induced signaling cascade initiated by ATM. Using potent PARP inhibitors and PARP-1 knock-out cells, we demonstrate a functional interplay between ATM and poly(ADP-ribose) that is important for the phosphorylation of p53, SMC1, and H2AX. For the first time, we demonstrate a functional and physical interaction between the major DSB signaling kinase, ATM and poly(ADP-ribosyl)ation by PARP-1, a key enzyme of chromatin remodeling. This study suggests that poly(ADP-ribose) might serve as a DNA damage sensory molecule that is critical for early DNA damage signaling.
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PMID:Ataxia telangiectasia mutated (ATM) signaling network is modulated by a novel poly(ADP-ribose)-dependent pathway in the early response to DNA-damaging agents. 1742 92

The MRE11 complex (MRE11, RAD50 and NBS1) and the ataxia-telangiectasia mutated (ATM) kinase function in the same DNA damage response pathway to effect cell cycle checkpoint activation and apoptosis. The functional interaction between the MRE11 complex and ATM has been proposed to require a conserved C-terminal domain of NBS1 for recruitment of ATM to sites of DNA damage. Human Nijmegen breakage syndrome (NBS) cells and those derived from multiple mouse models of NBS express a hypomorphic NBS1 allele that exhibits impaired ATM activity despite having an intact C-terminal domain. This indicates that the NBS1 C terminus is not sufficient for ATM function. We derived Nbs1(DeltaC/DeltaC) mice in which the C-terminal ATM interaction domain is deleted. Nbs1(DeltaC/DeltaC) cells exhibit intra-S-phase checkpoint defects, but are otherwise indistinguishable from wild-type cells with respect to other checkpoint functions, ionizing radiation sensitivity and chromosome stability. However, multiple tissues of Nbs1(DeltaC/DeltaC) mice showed a severe apoptotic defect, comparable to that of ATM- or CHK2-deficient animals. Analysis of p53 transcriptional targets and ATM substrates showed that, in contrast to the phenotype of Chk2(-/-) mice, NBS1(DeltaC) does not impair the induction of proapoptotic genes. Instead, the defects observed in Nbs1(DeltaC/DeltaC) result from impaired phosphorylation of ATM targets including SMC1 and the proapoptotic factor, BID.
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PMID:The carboxy terminus of NBS1 is required for induction of apoptosis by the MRE11 complex. 1742 52


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