Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Integration of a DNA copy of the viral RNA genome is a crucial step in the life cycle of human immunodeficiency virus type 1 (HIV-1) and other retroviruses. While the virally encoded integrase is key to this process, cellular factors yet to be characterized are suspected to participate in its completion. DNA damage sensors such as ATM (ataxia-telangiectasia mutated), ATR (ATM- and Rad3-related), DNA-PK (DNA-dependent protein kinase), and PARP-1 [poly(ADP-ribose) polymerase 1] play central roles in responses to various forms of DNA injury and as such could facilitate HIV integration. To test this hypothesis, we examined the susceptibility to infection with wild-type HIV-1 and to transduction with a vesicular stomatitis virus G protein (VSV-G)-pseudotyped HIV-1-derived lentiviral vector of human cells stably expressing small interfering RNAs against ATM, ATR, and PARP-1. We found that integration normally occurred in these knockdown cells. Similarly, the VSV-G-pseudotyped HIV-1-based vector could effectively transduce ATM and PARP-1 knockout mouse cells as well as human cells deficient for DNA-PK. Finally, treatment of target cells with the ATM and ATR inhibitors caffeine and wortmannin was without effect in these infectivity assays. We conclude that the DNA repair enzymes ATM, ATR, DNA-PKcs, and PARP-1 are not essential for HIV-1 integration.
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PMID:DNA damage sensors ATM, ATR, DNA-PKcs, and PARP-1 are dispensable for human immunodeficiency virus type 1 integration. 1570 17

Cell cycle arrest in response to DNA damage is important for the maintenance of genomic integrity in higher eukaryotes. We have previously reported the novel p53-dependent S-phase checkpoint operating in mouse zygotes fertilized with irradiated sperm. In the present study, we analysed the detail of the p53 function required for this S-phase checkpoint in mouse zygotes. The results indicate that ATM kinase is likely to be indispensable for the p53-dependent S-phase checkpoint since the suppression was abrogated by inhibitors such as caffeine and wortmannin. However, ATM phosphorylation site mutant proteins were still capable of suppressing DNA synthesis when microinjected into sperm-irradiated zygotes lacking the functional p53, suggesting that the target of the phosphorylation is not p53. In addition, the suppression was not affected by alpha-amanitin, and p53 protein mutated at the transcriptional activation domain was also functional in the suppression of DNA synthesis. However, p53 proteins mutated at the DNA-binding domain were devoid of the suppressing activity. Taken together, the transcription-independent function of p53 associated with the DNA-binding domain is involved in the S-phase checkpoint in collaboration with yet another unidentified target protein(s).
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PMID:Transcription-independent suppression of DNA synthesis by p53 in sperm-irradiated mouse zygotes. 1573 81

We evaluate here whether RAD51 and its paralogues XRCC2 and XRCC3 act via a common pathway for sensitivity to genotoxic stress, centrosome fragmentation and chromosome stability. We expressed the RAD51 dominant-negative SMRAD51 in irs1 and irs1SF cells, defective for XRCC2 and XRCC3, respectively, and in their corresponding wild-type cells (V79 and AA8, respectively). V79-SMRAD51 cells are sensitive to mitomycin C (MMC), but SMRAD51 did not further sensitize irs1 cells to MMC, showing that SMRAD51 and XRCC2 act on the same pathway for resistance to MMC. However, in contrast to irs1 and irs1SF cells, SMRAD51-V79 and SMRAD51-AA8 cells are not sensitive to gamma-rays or UV-C. Despite these differences in sensitivity, SMRAD51-expressing cells and xrcc2- or xrcc3-defective cells show similar increased levels of centrosome fragmentation. This spontaneous centrosome fragmentation is resistant to caffeine, suggesting that ATM and ATR are not involved. Consistent with centrosome fragmentation, increased aneuploidy was measured in irs1 and SMRAD51-expressing cells. Expression of SMRAD51 in irs1 or irs1SF cells did not increase further the frequency of multipolar cells. Thus, RAD51, XRCC2 and XRCC3 act in the same pathway for centrosome fragmentation, independently of the sensitivity to exogenous genotoxic stresses and of the ATM/ATR pathway.
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PMID:Genetic interactions between RAD51 and its paralogues for centrosome fragmentation and ploidy control, independently of the sensitivity to genotoxic stresses. 1578 36

In the present study, we employed a well established JB6 mouse epithelial cell model to define the molecular mechanism of efficacy of a naturally occurring flavonoid silibinin against ultraviolet B (UVB)-induced skin tumorigenesis. UVB exposure of cells caused a moderate phosphorylation of ERK1/2 and Akt and a stronger phosphorylation of p53 at Ser(15), which was enhanced markedly by silibinin pretreatment. Kinase activity of ERK1/2 for Elk-1 and Akt for glycogen synthase kinase-3beta was also potently enhanced by silibinin pretreatment. Furthermore, silibinin increased the UVB-induced level of cleaved caspase 3 as well as apoptotic cells. Based on these observations, next we investigated the role of upstream kinases, ATM/ATR and DNA-PK, which act as sensors for UVB-induced DNA damage and transduce signals leading to DNA repair or apoptosis. Whereas UVB strongly activated ATM as observed by Ser(1981) phosphorylation, it was not affected by silibinin pretreatment. However, pretreatment of cells with the DNA-protein kinase (PK) inhibitor LY294002 strongly reversed silibinin-enhanced Akt-Ser(473) and p53-Ser(15) as well as ERK1/2 phosphorylation together with a dose-dependent decrease in cleaved caspase 3 and apoptosis (p < 0.05). In addition, silibinin pretreatment strongly enhanced H2A.X-Ser(139) phosphorylation and DNA-PK-associated kinase activity as well as the physical interaction of p53 with DNA-PK; pretreatment of cells with LY294002 but not caffeine abolished the silibinin-caused increase in both DNA-PK activation and p53-Ser(15) phosphorylations. Together, these findings suggest that silibinin preferentially activates the DNA-PK-p53 pathway for apoptosis in response to UVB-induced DNA damage, and that this could be a predominant mechanism of silibinin efficacy against UVB-induced skin cancer.
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PMID:Silibinin up-regulates DNA-protein kinase-dependent p53 activation to enhance UVB-induced apoptosis in mouse epithelial JB6 cells. 1579 56

Human checkpoint kinase 1 (Chk1) is an essential kinase required to preserve genome stability. Here, we show that Chk1 inhibition by two distinct drugs, UCN-01 and CEP-3891, or by Chk1 small interfering RNA (siRNA) leads to phosphorylation of ATR targets. Chk1-inhibition triggered rapid, pan-nuclear phosphorylation of histone H2AX, p53, Smc1, replication protein A, and Chk1 itself in human S-phase cells. These phosphorylations were inhibited by ATR siRNA and caffeine, but they occurred independently of ATM. Chk1 inhibition also caused an increased initiation of DNA replication, which was accompanied by increased amounts of nonextractable RPA protein, formation of single-stranded DNA, and induction of DNA strand breaks. Moreover, these responses were prevented by siRNA-mediated downregulation of Cdk2 or the replication initiation protein Cdc45, or by addition of the CDK inhibitor roscovitine. We propose that Chk1 is required during normal S phase to avoid aberrantly increased initiation of DNA replication, thereby protecting against DNA breakage. These results may help explain why Chk1 is an essential kinase and should be taken into account when drugs to inhibit this kinase are considered for use in cancer treatment.
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PMID:Inhibition of human Chk1 causes increased initiation of DNA replication, phosphorylation of ATR targets, and DNA breakage. 1583 61

Human immunodeficiency virus type I (HIV-1) DNA integration is an essential step of viral replication. We have suggested recently that this stage of HIV-1 life-cycle triggers a cellular DNA damage response and requires cellular DNA repair proteins for its completion. These include DNA-PK (DNA-dependent protein kinase), ATR (ataxia telangiectasia and Rad3-related), and, at least in some circumstances, ATM (ataxia telangiectasia mutated). Host cell proteins may constitute an attractive target for anti-HIV-1 therapeutics, since development of drug resistance against compounds targeting these cellular cofactor proteins is unlikely. In this study, we show that an inhibitor of ATR and ATM kinases, caffeine, can suppress replication of infectious HIV-1 strains, and provide evidence that caffeine exerts its inhibitory effect at the integration step of the HIV-1 life-cycle. We also demonstrate that caffeine-related methylxanthines including the clinically used compound, theophylline, act at the same step of the HIV-1 life-cycle as caffeine and efficiently inhibit HIV-1 replication in primary human cells. These data reveal the feasibility of therapeutic approaches targeting host cell proteins and further support the hypothesis that ATR and ATM proteins are involved in retroviral DNA integration.
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PMID:Inhibition of HIV-1 replication by caffeine and caffeine-related methylxanthines. 1584 May 17

Resveratrol is one of the most extensively studied cancer chemopreventive agents; however, its mechanisms of action are not completely understood. Here, we observed that resveratrol induces S phase arrest via Tyr15 phosphorylation of Cdc2 in human ovarian carcinoma Ovcar-3 cells. Overexpression of Cdc2AF, a mutant resistant to Thr14 and Tyr15 phosphorylation, ablated resveratrol-induced S phase arrest. Further upstream, we observed that resveratrol causes phosphorylation of cell division cycle 25C (Cdc25C) tyrosine phosphatase via the activation of checkpoint kinases Chk1 and Chk2, which in turn were activated via ATM (ataxia telangiectasia mutated)/ATR (ataxia telangiectasia-Rad3-related) kinase in response to DNA damage, as resveratrol also increased phospho-H2A.X (Ser139), which is known to be phosphorylated by ATM/ATR in response to DNA damage. The involvement of these molecules in resveratrol-induced S phase was also supported by the studies showing that addition of ATM/ATR inhibitor caffeine reverses resveratrol-caused activation of ATM/ATR-Chk1/2 as well as phosphorylation of Cdc25C, Cdc2 and H2A.X, and S phase arrest. In additional studies assessing whether observed effects of resveratrol are specific to Ovcar-3 cells, we observed that it also induces S phase arrest and H2A.X (Ser139) phosphorylation in other ovarian cancer cell lines PA-1 and SKOV-3, albeit at different levels; whereas, resveratrol showed only marginal S phase arrest in normal human foreskin fibroblasts with undetectable level of phospho-H2A.X (Ser139). These findings for the first time identify that resveratrol causes Cdc2-tyr15 phosphorylation via ATM/ATR-Chk1/2-Cdc25C pathway as a central mechanism for DNA damage and S phase arrest selectively in ovarian cancer cells, and provide a rationale for the potential efficacy of ATM/ATR agonists in the prevention and intervention of cancer.
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PMID:Resveratrol causes Cdc2-tyr15 phosphorylation via ATM/ATR-Chk1/2-Cdc25C pathway as a central mechanism for S phase arrest in human ovarian carcinoma Ovcar-3 cells. 1597 56

S(N)1-alkylating agents, such as the mutagenic and cytotoxic drug N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), robustly activate the DNA damage-responsive G(2) checkpoint. Establishment of this checkpoint is dependent on a functional mismatch repair (MMR) system; however, exposure to high doses of MNNG overrides the requirement for MMR to trigger G(2) arrest. In addition, unlike moderate-dose exposure, in which the G(2) checkpoint is attenuated in ataxia-telangiectasia, mutated (ATM)-deficient cells, high-dose MNNG treatment activates G(2) arrest through an ATM-independent mechanism. We document that this arrest is sensitive to the pharmacological agents caffeine and 7-hydroxystaurosporine (UCN-01) that inhibit the checkpoint kinases ATM/ATM and Rad-3-related (ATR) and Chk1/Chk2, respectively. Furthermore, these agents block inactivation of the cell-cycle regulatory molecules Cdc25C and Cdc2, establishing the downstream mechanism through which high-dose MNNG establishes G(2) arrest. Activation of both Chk2 and Chk1 was independent of ATM and MMR in response to high-dose MNNG, unlike the response to moderate doses of this drug. Chk2 was found to be dispensable for cell-cycle arrest in response to high-dose MNNG treatment; however, ATR deficiency and decreased Chk1 expression forced by RNA interference resulted in diminished checkpoint response. These results indicate that MNNG activates the G(2) checkpoint through different mechanisms activated in a dose-dependent fashion.
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PMID:N-methyl-N'-nitro-N-nitrosoguanidine activates cell-cycle arrest through distinct mechanisms activated in a dose-dependent manner. 1599 68

Iron is critical for cell growth and proliferation. Iron chelators are being explored for a number of clinical applications, including the treatment of neurodegenerative disorders, heart disease, and cancer. To uncover mechanisms of action of tachpyridine, a chelator currently undergoing preclinical evaluation as an anticancer agent, cell-cycle analysis was performed. Tachpyridine arrested cells at G2, a radiosensitive phase of the cell cycle, and enhanced the sensitivity of cancer cells but not nontransformed cells to ionizing radiation. G2 arrest was p53 independent and was accompanied by activation of the checkpoint kinases CHK1 and CHK2. G2 arrest was blocked by UCN-01, a CHK1 inhibitor, but proceeded in CHK2 knock-out cells, indicating a critical role for CHK1 in G2 arrest. Tachpyridine-induced cell-cycle arrest was abrogated in cells treated with caffeine, an inhibitor of the ataxia-telangiectasia mutated/ataxia-telangiectasia-mutated and Rad3-related (ATM/ATR) kinases. Further, G2 arrest proceeded in ATM-deficient cells but was blocked in ATR-deficient cells, implicating ATR as the proximal kinase in tachpyridine-mediated G2 arrest. Collectively, our results suggest that iron chelators may function as antitumor and radioenhancing agents and uncover a previously unexplored activity of iron chelators in activation of ATR and checkpoint kinases.
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PMID:Tachpyridine, a metal chelator, induces G2 cell-cycle arrest, activates checkpoint kinases, and sensitizes cells to ionizing radiation. 1601 67

Ataxia-telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR) kinases, family members of the PI-3 kinase related proteins, play a key role in checkpoint activation and maintenance of genomic stability following DNA damage. We have used wild type (WT) and p38alpha-deficient mouse embryonic stem (ES) cells to investigate the role of ATR and ATM kinases during embryonic cell cycle. We have found that inhibition of ATR and ATM kinases with caffeine or Chk1 with UCN-01, results in activation of a p38-dependent intra-S-phase checkpoint and activation of apoptosis in ES cells. However, wortmannin at a concentration, that inhibits ATM kinase but not ATR kinase, did not affect cell cycle progression. Furthermore, the presence of caffeine results in activation of p38 kinase, accumulation of p21/Waf1 in a complex with Cdk2 and decrease of Cdk2 kinase activity. In contrast, caffeine-treated p38alpha-/- ES cells show less apoptosis, and fail to trigger an effective S-phase checkpoint and accumulation of p21/Waf1. We conclude that ATR kinase activity is essential for normal cell cycle progression of exponentially proliferating mouse ES cells even in the absence of exogenous DNA damage, and ATR deregulation triggers p38alpha-dependent cell-cycle checkpoint and apoptotic responses.
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PMID:Inhibition of the ATR/Chk1 pathway induces a p38-dependent S-phase delay in mouse embryonic stem cells. 1613 10


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