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Sample records for checkpoint kinase chk1

  1. A phospho-proteomic screen identifies substrates of the checkpoint kinase Chk1

    DEFF Research Database (Denmark)

    Blasius, Melanie; Forment, Josep V; Thakkar, Neha;

    2011-01-01

    BACKGROUND: The cell-cycle checkpoint kinase Chk1 is essential in mammalian cells due to its roles in controlling processes such as DNA replication, mitosis and DNA-damage responses. Despite its paramount importance, how Chk1 controls these functions remains unclear, mainly because very few Chk1...

  2. The cell-cycle checkpoint kinase Chk1 is required for mammalian homologous recombination repair

    DEFF Research Database (Denmark)

    Sørensen, Claus Storgaard; Hansen, Lasse Tengbjerg; Dziegielewski, Jaroslaw;

    2005-01-01

    The essential checkpoint kinase Chk1 is required for cell-cycle delays after DNA damage or blocked DNA replication. However, it is unclear whether Chk1 is involved in the repair of damaged DNA. Here we establish that Chk1 is a key regulator of genome maintenance by the homologous recombination......, the essential recombination repair protein RAD51 is recruited to DNA repair foci performing a vital role in correct HRR. We demonstrate that Chk1 interacts with RAD51, and that RAD51 is phosphorylated on Thr 309 in a Chk1-dependent manner. Consistent with a functional interplay between Chk1 and RAD51...

  3. Modulation of human checkpoint kinase Chk1 by the regulatory beta-subunit of protein kinase CK2

    DEFF Research Database (Denmark)

    Guerra, Barbara; Issinger, Olaf-Georg; Wang, Jean Y J

    2003-01-01

    Protein kinase CK2 is a serine/threonine protein kinase involved in various aspects of cellular regulation. The regulatory beta-subunit of CK2 exerts a central role not only in mediating formation of tetrameric CK2 complexes but also as a docking partner for several protein kinases. In this study......, CK2beta is found to interact with the human cell cycle checkpoint kinase Chk1. The Chk1-interacting region of CK2beta is localized at the C-terminus and the complex between CK2beta and Chk1 is devoid of the catalytic CK2alpha-subunit. The interaction between CK2beta and Chk1 leads to an increase in...... the Cdc25C phosphorylation activity of Chk1. The screening of several cell lines has revealed that the association between CK2beta and Chk1 also occurs in vivo at a different degree. Collectively, these studies confirm the implication of the regulatory beta-subunit of protein kinase CK2 in cell cycle...

  4. Phosphorylation of the regulatory beta-subunit of protein kinase CK2 by checkpoint kinase Chk1: identification of the in vitro CK2beta phosphorylation site

    DEFF Research Database (Denmark)

    Kristensen, Lars P; Larsen, Martin Røssel; Højrup, Peter; Issinger, Olaf-Georg; Guerra, Barbara

    The regulatory beta-subunit of protein kinase CK2 mediates the formation of the CK2 tetrameric form and it has functions independent of CK2 catalytic subunit through interaction with several intracellular proteins. Recently, we have shown that CK2beta associates with the human checkpoint kinase Chk......1. In this study, we show that Chk1 specifically phosphorylates in vitro the regulatory beta-subunit of CK2. Chymotryptic peptides and mutational analyses have revealed that CK2beta is phosphorylated at Thr213. Formation of a stable complex between CK2beta and Chk1 is not affected by the...

  5. The regulatory beta-subunit of protein kinase CK2 accelerates the degradation of CDC25A phosphatase through the checkpoint kinase Chk1

    DEFF Research Database (Denmark)

    Kreutzer, Jan Nicolas; Guerra, Barbara

    2007-01-01

    Human CDC25 phosphatases play an important role in cell cycle regulation by removing inhibitory phosphate groups on cyclin-CDKs. Chk1 has been shown to phosphorylate CDC25 family members down-regulating their phosphatase activity through distinct mechanisms. The kinase activity of Chk1 is evident...... cell cycle progression is shown to enhance CDC25A degradation, and this occurs in a manner similar to that by which CDC25A is down-regulated upon activation of cellular checkpoint responses. By using RNA interference to specifically deplete cells of Chk1, we demonstrate that Chk1 mediates the down-regulation...... cell cycle regulation and indicate the mechanism by which CDC25A turnover might be regulated by Chk1 in the absence of DNA damage....

  6. Poly(ADP-ribose) binding to Chk1 at stalled replication forks is required for S-phase checkpoint activation

    Science.gov (United States)

    Min, Wookee; Bruhn, Christopher; Grigaravicius, Paulius; Zhou, Zhong-Wei; Li, Fu; Krüger, Anja; Siddeek, Bénazir; Greulich, Karl-Otto; Popp, Oliver; Meisezahl, Chris; Calkhoven, Cornelis F.; Bürkle, Alexander; Xu, Xingzhi; Wang, Zhao-Qi

    2013-12-01

    Damaged replication forks activate poly(ADP-ribose) polymerase 1 (PARP1), which catalyses poly(ADP-ribose) (PAR) formation; however, how PARP1 or poly(ADP-ribosyl)ation is involved in the S-phase checkpoint is unknown. Here we show that PAR, supplied by PARP1, interacts with Chk1 via a novel PAR-binding regulatory (PbR) motif in Chk1, independent of ATR and its activity. iPOND studies reveal that Chk1 associates readily with the unperturbed replication fork and that PAR is required for efficient retention of Chk1 and phosphorylated Chk1 at the fork. A PbR mutation, which disrupts PAR binding, but not the interaction with its partners Claspin or BRCA1, impairs Chk1 and the S-phase checkpoint activation, and mirrors Chk1 knockdown-induced hypersensitivity to fork poisoning. We find that long chains, but not short chains, of PAR stimulate Chk1 kinase activity. Collectively, we disclose a previously unrecognized mechanism of the S-phase checkpoint by PAR metabolism that modulates Chk1 activity at the replication fork.

  7. Chk1 regulates the S phase checkpoint by coupling the physiological turnover and ionizing radiation-induced accelerated proteolysis of Cdc25A

    DEFF Research Database (Denmark)

    Sørensen, Claus Storgaard; Syljuåsen, Randi G; Falck, Jacob;

    2003-01-01

    Chk1 kinase coordinates cell cycle progression and preserves genome integrity. Here, we show that chemical or genetic ablation of human Chk1 triggered supraphysiological accumulation of the S phase-promoting Cdc25A phosphatase, prevented ionizing radiation (IR)-induced degradation of Cdc25A, and...... by a combined action of Chk1 and Chk2 kinases. Finally, phosphorylation of Chk1 by ATM was required to fully accelerate the IR-induced degradation of Cdc25A. Our results provide evidence that the mammalian S phase checkpoint functions via amplification of physiologically operating, Chk1-dependent...

  8. NEK11: linking CHK1 and CDC25A in DNA damage checkpoint signaling

    DEFF Research Database (Denmark)

    Sørensen, Claus Storgaard; Melixetian, Marina; Klein, Ditte Kjaersgaard;

    2010-01-01

    The DNA damage induced G(2)/M checkpoint is an important guardian of the genome that prevents cell division when DNA lesions are present. The checkpoint prevents cells from entering mitosis by degrading CDC25A, a key CDK activator. CDC25A proteolysis is controlled by direct phosphorylation events...... required for beta-TrCP mediated CDC25A polyubiquitylation and degradation. The activity of NEK11 is in turn controlled by CHK1 that activates NEK11 via phosphorylation on serine 273. Since inhibition of NEK11 activity forces checkpoint-arrested cells into mitosis and cell death, NEK11 is, like CHK1, a...

  9. Checkpoint kinase 1 negatively regulates somatic hypermutation.

    Science.gov (United States)

    Frankenberger, Samantha; Davari, Kathrin; Fischer-Burkart, Sabine; Böttcher, Katrin; Tomi, Nils-Sebastian; Zimber-Strobl, Ursula; Jungnickel, Berit

    2014-04-01

    Immunoglobulin (Ig) diversification by somatic hypermutation in germinal center B cells is instrumental for maturation of the humoral immune response, but also bears the risk of excessive or aberrant genetic changes. Thus, introduction of DNA damage by activation-induced cytidine deaminase as well as DNA repair by multiple pathways need to be tightly regulated during the germinal center response to prevent lymphomagenesis. In the present study, we show that DNA damage checkpoint signaling via checkpoint kinase 1 (Chk1) negatively regulates somatic hypermutation. Chk1 inhibition in human B cell lymphoma lines as well as inactivation of Chk1 alleles by gene targeting in DT40 B cells leads to increased somatic hypermutation. This is apparently due to changes in DNA repair pathways regulated by Chk1, such as a decreased homologous recombination efficiency that also leads to decreased Ig gene conversion in DT40. Our data show that Chk1 signaling plays a crucial role in regulation of Ig diversification and sheds unexpected light on potential origins of aberrant somatic hypermutation in B cell lymphomagenesis. PMID:24423870

  10. Cancer-Specific Synthetic Lethality between ATR and CHK1 Kinase Activities

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    Kumar Sanjiv

    2016-01-01

    Full Text Available ATR and CHK1 maintain cancer cell survival under replication stress and inhibitors of both kinases are currently undergoing clinical trials. As ATR activity is increased after CHK1 inhibition, we hypothesized that this may indicate an increased reliance on ATR for survival. Indeed, we observe that replication stress induced by the CHK1 inhibitor AZD7762 results in replication catastrophe and apoptosis, when combined with the ATR inhibitor VE-821 specifically in cancer cells. Combined treatment with ATR and CHK1 inhibitors leads to replication fork arrest, ssDNA accumulation, replication collapse, and synergistic cell death in cancer cells in vitro and in vivo. Inhibition of CDK reversed replication stress and synthetic lethality, demonstrating that regulation of origin firing by ATR and CHK1 explains the synthetic lethality. In conclusion, this study exemplifies cancer-specific synthetic lethality between two proteins in the same pathway and raises the prospect of combining ATR and CHK1 inhibitors as promising cancer therapy.

  11. Defective DNA repair increases susceptibility to senescence through extension of Chk1-mediated G2 checkpoint activation.

    Science.gov (United States)

    Johmura, Yoshikazu; Yamashita, Emiri; Shimada, Midori; Nakanishi, Keiko; Nakanishi, Makoto

    2016-01-01

    Susceptibility to senescence caused by defective DNA repair is a major hallmark of progeroid syndrome patients, but molecular mechanisms of how defective DNA repair predisposes to senescence are largely unknown. We demonstrate here that suppression of DNA repair pathways extends the duration of Chk1-dependent G2 checkpoint activation and sensitizes cells to senescence through enhancement of mitosis skipping. Extension of G2 checkpoint activation by introduction of the TopBP1 activation domain and the nondegradable mutant of Claspin sensitizes cells to senescence. In contrast, a shortening of G2 checkpoint activation by expression of SIRT6 or depletion of OTUB2 reduces susceptibility to senescence. Fibroblasts from progeroid syndromes tested shows a correlation between an extension of G2 checkpoint activation and an increase in the susceptibility to senescence. These results suggest that extension of G2 checkpoint activation caused by defective DNA repair is critical for senescence predisposition in progeroid syndrome patients. PMID:27507734

  12. Blocking CHK1 Expression Induces Apoptosis and Abrogates the G2 Checkpoint Mechanism

    Directory of Open Access Journals (Sweden)

    Yan Luo

    2001-01-01

    Full Text Available Checkpoint kinase 1 (Chki is a checkpoint gene that is activated after DNA damage. It phosphorylates and inactivates the Cdc2 activating phosphatase Cdc25C. This in turn inactivates Cdc2, which leads to G2/M arrest. We report that blocking Chki expression by antisense or ribozymes in mammalian cells induces apoptosis and interferes with the G2/M arrest induced by adriamycin. The Chki inhibitor UCN-01 also blocks the G2 arrest after DNA damage and renders cells more susceptible to adriamycin. These results indicate that Chki is an essential gene for the checkpoint mechanism during normal cell proliferation as well as in the DNA damage response.

  13. Targeting lung cancer through inhibition of checkpoint kinases

    OpenAIRE

    Syljuåsen, Randi G; Hasvold, Grete; Hauge, Sissel; Helland, Åslaug

    2015-01-01

    Inhibitors of checkpoint kinases ATR, Chk1, and Wee1 are currently being tested in preclinical and clinical trials. Here, we review the basic principles behind the use of such inhibitors as anticancer agents, and particularly discuss their potential for treatment of lung cancer. As lung cancer is one of the most deadly cancers, new treatment strategies are highly needed. We discuss how checkpoint kinase inhibition in principle can lead to selective killing of lung cancer cells while sparing t...

  14. Toxic effect of silica nanoparticles on endothelial cells through DNA damage response via Chk1-dependent G2/M checkpoint.

    Directory of Open Access Journals (Sweden)

    Junchao Duan

    Full Text Available Silica nanoparticles have become promising carriers for drug delivery or gene therapy. Endothelial cells could be directly exposed to silica nanoparticles by intravenous administration. However, the underlying toxic effect mechanisms of silica nanoparticles on endothelial cells are still poorly understood. In order to clarify the cytotoxicity of endothelial cells induced by silica nanoparticles and its mechanisms, cellular morphology, cell viability and lactate dehydrogenase (LDH release were observed in human umbilical vein endothelial cells (HUVECs as assessing cytotoxicity, resulted in a dose- and time- dependent manner. Silica nanoparticles-induced reactive oxygen species (ROS generation caused oxidative damage followed by the production of malondialdehyde (MDA as well as the inhibition of superoxide dismutase (SOD and glutathione peroxidase (GSH-Px. Both necrosis and apoptosis were increased significantly after 24 h exposure. The mitochondrial membrane potential (MMP decreased obviously in a dose-dependent manner. The degree of DNA damage including the percentage of tail DNA, tail length and Olive tail moment (OTM were markedly aggravated. Silica nanoparticles also induced G2/M arrest through the upregulation of Chk1 and the downregulation of Cdc25C, cyclin B1/Cdc2. In summary, our data indicated that the toxic effect mechanisms of silica nanoparticles on endothelial cells was through DNA damage response (DDR via Chk1-dependent G2/M checkpoint signaling pathway, suggesting that exposure to silica nanoparticles could be a potential hazards for the development of cardiovascular diseases.

  15. Identification of inhibitors of checkpoint kinase 1 through template screening.

    Science.gov (United States)

    Matthews, Thomas P; Klair, Suki; Burns, Samantha; Boxall, Kathy; Cherry, Michael; Fisher, Martin; Westwood, Isaac M; Walton, Michael I; McHardy, Tatiana; Cheung, Kwai-Ming J; Van Montfort, Rob; Williams, David; Aherne, G Wynne; Garrett, Michelle D; Reader, John; Collins, Ian

    2009-08-13

    Checkpoint kinase 1 (CHK1) is an oncology target of significant current interest. Inhibition of CHK1 abrogates DNA damage-induced cell cycle checkpoints and sensitizes p53 deficient cancer cells to genotoxic therapies. Using template screening, a fragment-based approach to small molecule hit generation, we have identified multiple CHK1 inhibitor scaffolds suitable for further optimization. The sequential combination of in silico low molecular weight template selection, a high concentration biochemical assay and hit validation through protein-ligand X-ray crystallography provided 13 template hits from an initial in silico screening library of ca. 15000 compounds. The use of appropriate counter-screening to rule out nonspecific aggregation by test compounds was essential for optimum performance of the high concentration bioassay. One low molecular weight, weakly active purine template hit was progressed by iterative structure-based design to give submicromolar pyrazolopyridines with good ligand efficiency and appropriate CHK1-mediated cellular activity in HT29 colon cancer cells. PMID:19572549

  16. Rad4 mainly functions in Chk1-mediated DNA damage checkpoint pathway as a scaffold protein in the fission yeast Schizosaccharomyces pombe.

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    Ming Yue

    Full Text Available Rad4/Cut5 is a scaffold protein in the Chk1-mediated DNA damage checkpoint in S. pombe. However, whether it contains a robust ATR-activation domain (AAD required for checkpoint signaling like its orthologs TopBP1 in humans and Dpb11 in budding yeast has been incompletely clear. To identify the putative AAD in Rad4, we carried out an extensive genetic screen looking for novel mutants with an enhanced sensitivity to replication stress or DNA damage in which the function of the AAD can be eliminated by the mutations. Two new mutations near the N-terminus were identified that caused significantly higher sensitivities to DNA damage or chronic replication stress than all previously reported mutants, suggesting that most of the checkpoint function of the protein is eliminated. However, these mutations did not affect the activation of Rad3 (ATR in humans yet eliminated the scaffolding function of the protein required for the activation of Chk1. Several mutations were also identified in or near the recently reported AAD in the C-terminus of Rad4. However, all mutations in the C-terminus only slightly sensitized the cells to DNA damage. Interestingly, a mutant lacking the whole C-terminus was found resistant to DNA damage and replication stress almost like the wild type cells. Consistent with the resistance, all known Rad3 dependent phosphorylations of checkpoint proteins remained intact in the C-terminal deletion mutant, indicating that unlike that in Dpb11, the C-terminus of Rad4 does not contain a robust AAD. These results, together with those from the biochemical studies, show that Rad4 mainly functions as a scaffold protein in the Chk1, not the Cds1(CHK2 in humans, checkpoint pathway. It plays a minor role or is functionally redundant with an unknown factor in Rad3 activation.

  17. Inhibition of Chk1 by CEP-3891 accelerates mitotic nuclear fragmentation in response to ionizing Radiation

    DEFF Research Database (Denmark)

    Syljuåsen, Randi G; Sørensen, Claus Storgaard; Nylandsted, Jesper;

    2004-01-01

    The human checkpoint kinase Chk1 has been suggested as a target for cancer treatment. Here, we show that a new inhibitor of Chk1 kinase, CEP-3891, efficiently abrogates both the ionizing radiation (IR)-induced S and G(2) checkpoints. When the checkpoints were abrogated by CEP-3891, the majority (64......%) of cells showed fragmented nuclei at 24 hours after IR (6 Gy). The formation of nuclear fragmentation in IR-treated human cancer cells was directly visualized by time-lapse video microscopy of U2-OS cells expressing a green fluorescent protein-tagged histone H2B protein. Nuclear fragmentation...

  18. Chk1 prevents abnormal mitosis of S-phase HeLa cells containing DNA damage

    Institute of Scientific and Technical Information of China (English)

    LI XiaoFang; WARD Tarsha; YAO XueBiao; WU JiaRui

    2009-01-01

    To explore effects of DNA damage on cell-cycle progression in p53-deficient tumor cells,synchronized HeLa cells at G1,S and G2/M phases were treated with methyl methanesulfnate (MMS).The results showed that the MMS treatment resulted in the cell-cycle arrest or delay in all 3 phases,while the S-phase cells were the most sensitive to MMS.Further studies demonstrated that ATM-Chk2 and p38 MAPK signaling pathways were activated in all 3 phases when the cells were treated with MMS;whereas Chk1 was activated only in S phase under the drug treatment,indicating that Chk1 specifically participated in S-phase checkpoints.To analyze the role of Chk1 in S-phase checkpoints,we administered a specific Chk1 inhibitor,UCN-01,to the S-phase cells.The results showed that the S-phase cells treated with MMS+UCN-01 could enter aberrant mitosis without finishing DNA replication,indicating that Chk1 mainly functions in the DNA damage checkpoint rather than in the replication checkpoint.In addition,MMS treatment alone inhibited the accumulation of cyclin B1,a key component of M-phase CDK-cyclin complex,in the S-phase cells,whereas the inhibition of Chk1 activation resulted in the accumulation of cyclin B1 in the MMS-treated S-phase cells.This observation further supports the view that DNA-damaged S-phase cells enter abnormal mitosis when Chk1 activation is inhibited.Our results demonstrate that Chk1 is a specific kinase that plays an important role in the MMS-induced S-phase DNA damage checkpoint.As p53 is not involved in this process,Chk1 may be a potential target for p53-deficient tumor therapy.

  19. RHINO forms a stoichiometric complex with the 9-1-1 checkpoint clamp and mediates ATR-Chk1 signaling

    OpenAIRE

    Lindsey-Boltz, Laura A.; Kemp, Michael G.; Capp, Christopher; Sancar, Aziz

    2015-01-01

    The ATR-Chk1 signaling pathway mediates cellular responses to DNA damage and replication stress and is composed of a number of core factors that are conserved throughout eukaryotic organisms. However, humans and other higher eukaryotic species possess additional factors that are implicated in the regulation of this signaling network but that have not been extensively studied. Here we show that RHINO (for Rad9, Rad1, Hus1 interacting nuclear orphan) forms complexes with both the 9-1-1 checkpoi...

  20. In Silico Exploration of 1,7-Diazacarbazole Analogs as Checkpoint Kinase 1 Inhibitors by Using 3D QSAR, Molecular Docking Study, and Molecular Dynamics Simulations

    OpenAIRE

    Xiaodong Gao; Liping Han; Yujie Ren

    2016-01-01

    Checkpoint kinase 1 (Chk1) is an important serine/threonine kinase with a self-protection function. The combination of Chk1 inhibitors and anti-cancer drugs can enhance the selectivity of tumor therapy. In this work, a set of 1,7-diazacarbazole analogs were identified as potent Chk1 inhibitors through a series of computer-aided drug design processes, including three-dimensional quantitative structure–activity relationship (3D-QSAR) modeling, molecular docking, and molecular dynamics simulatio...

  1. Tumor suppressor protein C53 antagonizes checkpoint kinases to promote cyclin-dependent kinase 1 activation

    Institute of Scientific and Technical Information of China (English)

    Hai Jiang; Jianchun Wu; Chen He; Wending Yang; Honglin Li

    2009-01-01

    Cyclin-dependent kinase 1 (Cdk1)/cyclin B1 complex is the driving force for mitotic entry, and its activation is tightly regulated by the G2/M checkpoint. We originally reported that a novel protein C53 (also known as Cdk5rap3 and LZAP) potentiates DNA damage-induced cell death by modulating the G2/M checkpoint. More recently, Wang et al. (2007) found that C53/LZAP may function as a tumor suppressor by way of inhibiting NF-kB signaling. We report here the identification of C53 protein as a novel regulator of Cdk1 activation. We found that knockdown of C53 protein causes delayed Cdkl activation and mitotic entry. During DNA damage response, activation of checkpoint kinase 1 and 2 (Chk1 and Chk2) is partially inhibited by C53 overexpression. Intriguingly, we found that C53 interacts with Chkl and antagonizes its function. Moreover, a portion of C53 protein is localized at the centrosome, and centrosome-targeting C53 potently promotes local Cdk1 activation. Taken together, our results strongly suggest that C53 is a novel negative regulator of checkpoint response. By counteracting Chk1, C53 promotes Cdk1 activation and mitotic entry in both unperturbed cell-cycle progression and DNA damage response.

  2. Ataxia-telangiectasia-mutated (ATM) and NBS1-dependent phosphorylation of Chk1 on Ser-317 in response to ionizing radiation

    DEFF Research Database (Denmark)

    Gatei, Magtouf; Sloper, Katie; Sørensen, Claus Storgaard;

    2003-01-01

    In mammals, the ATM (ataxia-telangiectasia-mutated) and ATR (ATM and Rad3-related) protein kinases function as critical regulators of the cellular DNA damage response. The checkpoint functions of ATR and ATM are mediated, in part, by a pair of checkpoint effector kinases termed Chk1 and Chk2. In...

  3. Abrogation of Chk1-mediated S/G2 checkpoint by UCN-01 enhances ara-C-induced cytotoxicity in human colon cancer cells

    Institute of Scientific and Technical Information of China (English)

    Rong-guang SHAO; Chun-Xia CAO; Yves POMMIER

    2004-01-01

    AIM: To investigate whether 7-hydroxystaurosporine (UCN-01) affects cell cycle progression in arabinosylcytosine (ara-C) treated human colon carcinoma HT-29 cells. METHODS: Cytotoxicity, DNA synthesis, cell cycle distribution,protein level, and kinase activity were determined by clonogenic assay, flow cytometry, DNA synthesis assay,immunoblotting, and kinase assays, respectively. RESULTS: UCN-01 abrogated an S/G2-phase checkpoint in HT29 cells treated with ara-C. When UCN-01 was added after treatment with ara-C, the rate of recovery of DNA synthesis was enhanced and colony-forming ability diminished. Thus, premature recovery of DNA synthesis was associated with increased cytotoxicity. Measurements of cyclin A and B protein levels, Cdk2 and Cdc2 kinase activities, Cdc25C phosphorylation, and Chkl kinase activity were consistent with UCN-01-induced abrogation of the S/G2-phase checkpoint in ara-C treated cells. CONCLUSION: The abrogation of the S/G2 checkpoint may be due to inhibition of Chkl kinase by UCN-01. The enhanced cytotoxicity produced when UCN-01 was combined with ara-C suggested a rationale for the use of this drug combination for tumors that might be susceptible to cell cycle checkpoint abrogation.

  4. CHK1 ensures the preservation of DNA integrity during meiosis I but it is not a component of spindle assembly checkpoint

    Czech Academy of Sciences Publication Activity Database

    Mayer, Alexandra; Baran, V.; Kitajima, T.; Brzáková, Adéla; Ellenberg, J.; Motlík, Jan; Šolc, Petr

    Heidelberg : EMBL, 2012. 107-107. [EMBO/EMBL Symposium Germline Immortality through Totipotency. 13.10.2012-16.10.2012, Heidelberg] Institutional support: RVO:67985904 Keywords : CHK1 Subject RIV: EB - Genetics ; Molecular Biology

  5. Checkpoint Kinases Regulate a Global Network of Transcription Factors in Response to DNA Damage

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    Eric J. Jaehnig

    2013-07-01

    Full Text Available DNA damage activates checkpoint kinases that induce several downstream events, including widespread changes in transcription. However, the specific connections between the checkpoint kinases and downstream transcription factors (TFs are not well understood. Here, we integrate kinase mutant expression profiles, transcriptional regulatory interactions, and phosphoproteomics to map kinases and downstream TFs to transcriptional regulatory networks. Specifically, we investigate the role of the Saccharomyces cerevisiae checkpoint kinases (Mec1, Tel1, Chk1, Rad53, and Dun1 in the transcriptional response to DNA damage caused by methyl methanesulfonate. The result is a global kinase-TF regulatory network in which Mec1 and Tel1 signal through Rad53 to synergistically regulate the expression of more than 600 genes. This network involves at least nine TFs, many of which have Rad53-dependent phosphorylation sites, as regulators of checkpoint-kinase-dependent genes. We also identify a major DNA damage-induced transcriptional network that regulates stress response genes independently of the checkpoint kinases.

  6. Kinase signaling in the spindle checkpoint.

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    Kang, Jungseog; Yu, Hongtao

    2009-06-01

    The spindle checkpoint is a cell cycle surveillance system that ensures the fidelity of chromosome segregation. In mitosis, it elicits the "wait anaphase" signal to inhibit the anaphase-promoting complex or cyclosome until all chromosomes achieve bipolar microtubule attachment and align at the metaphase plate. Because a single kinetochore unattached to microtubules activates the checkpoint, the wait anaphase signal is thought to be generated by this kinetochore and is then amplified and distributed throughout the cell to inhibit the anaphase-promoting complex/cyclosome. Several spindle checkpoint kinases participate in the generation and amplification of this signal. Recent studies have begun to reveal the activation mechanisms of these checkpoint kinases. Increasing evidence also indicates that the checkpoint kinases not only help to generate the wait anaphase signal but also actively correct kinetochore-microtubule attachment defects. PMID:19228686

  7. Knockdown of checkpoint kinase 1 is associated with the increased radiosensitivity of glioblastoma stem-like cells

    International Nuclear Information System (INIS)

    Glioblastoma multiforme is an aggressive brain tumor with a poor prognosis. The glioblastoma stem-like cells (GSCs) represent a rare fraction of human glioblastoma cells with the capacity for multi-lineage differentiation, self-renewal and exact recapitulation of the original tumor. Interestingly, GSCs are more radioresistant compared with other tumor cells. In addition, the remarkable radioresistance of GSCs has been known to promote radiotherapy failure and therefore is associated with a significantly higher risk of a local tumor recurrence. Moreover, the hyperactive cell cycle checkpoint kinase (Chk) 1 and 2 play a pivotal role in the DNA damage response including radiation and chemical therapy. Based on aforementioned, we hypothesized that knockdown of Chk1 or Chk2 might confer radiosensitivity on GSCs and thereby increases the efficiency of radiotherapy. In this study, we knocked down the expression of Chk1 or Chk2 in human GSCs using lentivirus-delivered short hairpin RNA (shRNA) to examine its effect on the radiosensitivity. After radiation, the apoptosis rate and the cell cycle of GSCs were measured with Flow Cytometry. Compared with control GSCs (apoptosis, 7.82±0.38%; G2/M arrest, 60.20±1.28%), Chk1 knockdown in GSCs increased the apoptosis rate (37.87±0.32%) and decreased the degree of the G2/M arrest (22.37±2.01%). In contrast, the radiosensitivity was not enhanced by Chk2 knockdown in GSCs. These results suggest that depletion of Chk1 may improve the radio-sensitivity of GSCs via inducing cell apoptosis. In summary, the therapy targeting Chk1 gene in the GSCs may be a novel way to treat glioblastoma. (author)

  8. X-ray structures of checkpoint kinase 2 in complex with inhibitors that target its gatekeeper-dependent hydrophobic pocket

    Energy Technology Data Exchange (ETDEWEB)

    Lountos, George T.; Jobson, Andrew G.; Tropea, Joseph E.; Self, Christopher R.; Zhang, Guangtao; Pommier, Yves; Shoemaker, Robert H.; Waugh, David S. (Provid); (NIH); (SAIC); (NCI)

    2012-09-17

    The serine/threonine checkpoint kinase 2 (Chk2) is an attractive molecular target for the development of small molecule inhibitors to treat cancer. Here, we report the rational design of Chk2 inhibitors that target the gatekeeper-dependent hydrophobic pocket located behind the adenine-binding region of the ATP-binding site. These compounds exhibit IC{sub 50} values in the low nanomolar range and are highly selective for Chk2 over Chk1. X-ray crystallography was used to determine the structures of the inhibitors in complex with the catalytic kinase domain of Chk2 to verify their modes of binding.

  9. Chk1 suppressed cell death

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    Meuth Mark

    2010-09-01

    Full Text Available Abstract The role of Chk1 in the cellular response to DNA replication stress is well established. However recent work indicates a novel role for Chk1 in the suppression of apoptosis following the disruption of DNA replication or DNA damage. This review will consider these findings in the context of known pathways of Chk1 signalling and potential applications of therapies that target Chk1.

  10. Opposing effects of pericentrin and microcephalin on the pericentriolar material regulate CHK1 activation in the DNA damage response.

    Science.gov (United States)

    Antonczak, A K; Mullee, L I; Wang, Y; Comartin, D; Inoue, T; Pelletier, L; Morrison, C G

    2016-04-14

    Genotoxic stresses lead to centrosome amplification, a frequently-observed feature in cancer that may contribute to genome instability and to tumour cell invasion. Here we have explored how the centrosome controls DNA damage responses. For most of the cell cycle, centrosomes consist of two centrioles embedded in the proteinaceous pericentriolar material (PCM). Recent data indicate that the PCM is not an amorphous assembly of proteins, but actually a highly organised scaffold around the centrioles. The large coiled-coil protein, pericentrin, participates in PCM assembly and has been implicated in the control of DNA damage responses (DDRs) through its interactions with checkpoint kinase 1 (CHK1) and microcephalin (MCPH1). CHK1 is required for DNA damage-induced centrosome amplification, whereas MCPH1 deficiency greatly increases the amplification seen after DNA damage. We found that the PCM showed a marked expansion in volume and a noticeable change in higher-order organisation after ionising radiation treatment. PCM expansion was dependent on CHK1 kinase activity and was potentiated by MCPH1 deficiency. Furthermore, pericentrin deficiency or mutation of a separase cleavage site blocked DNA damage-induced PCM expansion. The extent of nuclear CHK1 activation after DNA damage reflected the level of PCM expansion, with a reduction in pericentrin-deficient or separase cleavage site mutant-expressing cells, and an increase in MCPH1-deficient cells that was suppressed by the loss of pericentrin. Deletion of the nuclear export signal of CHK1 led to its hyperphosphorylation after irradiation and reduced centrosome amplification. Deletion of the nuclear localisation signal led to low CHK1 activation and low centrosome amplification. From these data, we propose a feedback loop from the PCM to the nuclear DDR in which CHK1 regulates pericentrin-dependent PCM expansion to control its own activation. PMID:26165835

  11. Piperine causes G1 phase cell cycle arrest and apoptosis in melanoma cells through checkpoint kinase-1 activation.

    Directory of Open Access Journals (Sweden)

    Neel M Fofaria

    Full Text Available In this study, we determined the cytotoxic effects of piperine, a major constituent of black and long pepper in melanoma cells. Piperine treatment inhibited the growth of SK MEL 28 and B16 F0 cells in a dose and time-dependent manner. The growth inhibitory effects of piperine were mediated by cell cycle arrest of both the cell lines in G1 phase. The G1 arrest by piperine correlated with the down-regulation of cyclin D1 and induction of p21. Furthermore, this growth arrest by piperine treatment was associated with DNA damage as indicated by phosphorylation of H2AX at Ser139, activation of ataxia telangiectasia and rad3-related protein (ATR and checkpoint kinase 1 (Chk1. Pretreatment with AZD 7762, a Chk1 inhibitor not only abrogated the activation of Chk1 but also piperine mediated G1 arrest. Similarly, transfection of cells with Chk1 siRNA completely protected the cells from G1 arrest induced by piperine. Piperine treatment caused down-regulation of E2F1 and phosphorylation of retinoblastoma protein (Rb. Apoptosis induced by piperine was associated with down-regulation of XIAP, Bid (full length and cleavage of Caspase-3 and PARP. Furthermore, our results showed that piperine treatment generated ROS in melanoma cells. Blocking ROS by tiron protected the cells from piperine mediated cell cycle arrest and apoptosis. These results suggest that piperine mediated ROS played a critical role in inducing DNA damage and activation of Chk1 leading to G1 cell cycle arrest and apoptosis.

  12. Discovery of checkpoint kinase inhibitor (S)-5-(3-fluorophenyl)-N-(piperidin-3-yl)-3-ureidothiophene-2-carboxamide (AZD7762) by structure-based design and optimization of thiophenecarboxamide ureas.

    Science.gov (United States)

    Oza, Vibha; Ashwell, Susan; Almeida, Lynsie; Brassil, Patrick; Breed, Jason; Deng, Chun; Gero, Thomas; Grondine, Michael; Horn, Candice; Ioannidis, Stephanos; Liu, Dongfang; Lyne, Paul; Newcombe, Nicholas; Pass, Martin; Read, Jon; Ready, Shannon; Rowsell, Siân; Su, Mei; Toader, Dorin; Vasbinder, Melissa; Yu, Dingwei; Yu, Yan; Xue, Yafeng; Zabludoff, Sonya; Janetka, James

    2012-06-14

    Checkpoint kinases CHK1 and CHK2 are activated in response to DNA damage that results in cell cycle arrest, allowing sufficient time for DNA repair. Agents that lead to abrogation of such checkpoints have potential to increase the efficacy of such compounds as chemo- and radiotherapies. Thiophenecarboxamide ureas (TCUs) were identified as inhibitors of CHK1 by high throughput screening. A structure-based approach is described using crystal structures of JNK1 and CHK1 in complex with 1 and 2 and of the CHK1-3b complex. The ribose binding pocket of CHK1 was targeted to generate inhibitors with excellent cellular potency and selectivity over CDK1and IKKβ, key features lacking from the initial compounds. Optimization of 3b resulted in the identification of a regioisomeric 3-TCU lead 12a. Optimization of 12a led to the discovery of the clinical candidate 4 (AZD7762), which strongly potentiates the efficacy of a variety of DNA-damaging agents in preclinical models. PMID:22551018

  13. In Silico Exploration of 1,7-Diazacarbazole Analogs as Checkpoint Kinase 1 Inhibitors by Using 3D QSAR, Molecular Docking Study, and Molecular Dynamics Simulations.

    Science.gov (United States)

    Gao, Xiaodong; Han, Liping; Ren, Yujie

    2016-01-01

    Checkpoint kinase 1 (Chk1) is an important serine/threonine kinase with a self-protection function. The combination of Chk1 inhibitors and anti-cancer drugs can enhance the selectivity of tumor therapy. In this work, a set of 1,7-diazacarbazole analogs were identified as potent Chk1 inhibitors through a series of computer-aided drug design processes, including three-dimensional quantitative structure-activity relationship (3D-QSAR) modeling, molecular docking, and molecular dynamics simulations. The optimal QSAR models showed significant cross-validated correlation q² values (0.531, 0.726), fitted correlation r² coefficients (higher than 0.90), and standard error of prediction (less than 0.250). These results suggested that the developed models possess good predictive ability. Moreover, molecular docking and molecular dynamics simulations were applied to highlight the important interactions between the ligand and the Chk1 receptor protein. This study shows that hydrogen bonding and electrostatic forces are key interactions that confer bioactivity. PMID:27164065

  14. In Silico Exploration of 1,7-Diazacarbazole Analogs as Checkpoint Kinase 1 Inhibitors by Using 3D QSAR, Molecular Docking Study, and Molecular Dynamics Simulations

    Directory of Open Access Journals (Sweden)

    Xiaodong Gao

    2016-05-01

    Full Text Available Checkpoint kinase 1 (Chk1 is an important serine/threonine kinase with a self-protection function. The combination of Chk1 inhibitors and anti-cancer drugs can enhance the selectivity of tumor therapy. In this work, a set of 1,7-diazacarbazole analogs were identified as potent Chk1 inhibitors through a series of computer-aided drug design processes, including three-dimensional quantitative structure–activity relationship (3D-QSAR modeling, molecular docking, and molecular dynamics simulations. The optimal QSAR models showed significant cross-validated correlation q2 values (0.531, 0.726, fitted correlation r2 coefficients (higher than 0.90, and standard error of prediction (less than 0.250. These results suggested that the developed models possess good predictive ability. Moreover, molecular docking and molecular dynamics simulations were applied to highlight the important interactions between the ligand and the Chk1 receptor protein. This study shows that hydrogen bonding and electrostatic forces are key interactions that confer bioactivity.

  15. Optimising measles virus-guided radiovirotherapy with external beam radiotherapy and specific checkpoint kinase 1 inhibition

    International Nuclear Information System (INIS)

    Background and purpose: We previously reported a therapeutic strategy comprising replication-defective NIS-expressing adenovirus combined with radioiodide, external beam radiotherapy (EBRT) and DNA repair inhibition. We have now evaluated NIS-expressing oncolytic measles virus (MV-NIS) combined with NIS-guided radioiodide, EBRT and specific checkpoint kinase 1 (Chk1) inhibition in head and neck and colorectal models. Materials and methods: Anti-proliferative/cytotoxic effects of individual agents and their combinations were measured by MTS, clonogenic and Western analysis. Viral gene expression was measured by radioisotope uptake and replication by one-step growth curves. Potential synergistic interactions were tested in vitro by Bliss independence analysis and in in vivo therapeutic studies. Results: EBRT and MV-NIS were synergistic in vitro. Furthermore, EBRT increased NIS expression in infected cells. SAR-020106 was synergistic with EBRT, but also with MV-NIS in HN5 cells. MV-NIS mediated 131I-induced cytotoxicity in HN5 and HCT116 cells and, in the latter, this was enhanced by SAR-020106. In vivo studies confirmed that MV-NIS, EBRT and Chk1 inhibition were effective in HCT116 xenografts. The quadruplet regimen of MV-NIS, virally-directed 131I, EBRT and SAR-020106 had significant anti-tumour activity in HCT116 xenografts. Conclusion: This study strongly supports translational and clinical research on MV-NIS combined with radiation therapy and radiosensitising agents

  16. Inhibition of checkpoint kinase 1 sensitizes lung cancer brain metastases to radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Heekyoung [Department of Neurosurgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Gangnam-Gu, Seoul 135-710 (Korea, Republic of); Samsung Biomedical Research Institute, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Gangnam-Gu, Seoul 135-710 (Korea, Republic of); Cancer Stem Cell Research Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Gangnam-Gu, Seoul 135-710 (Korea, Republic of); Yoon, Su Jin [Samsung Biomedical Research Institute, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Gangnam-Gu, Seoul 135-710 (Korea, Republic of); Jin, Juyoun [Department of Neurosurgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Gangnam-Gu, Seoul 135-710 (Korea, Republic of); Samsung Biomedical Research Institute, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Gangnam-Gu, Seoul 135-710 (Korea, Republic of); Cancer Stem Cell Research Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Gangnam-Gu, Seoul 135-710 (Korea, Republic of); Choi, Seung Ho [Samsung Biomedical Research Institute, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Gangnam-Gu, Seoul 135-710 (Korea, Republic of); Seol, Ho Jun; Lee, Jung-Il [Department of Neurosurgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Gangnam-Gu, Seoul 135-710 (Korea, Republic of); and others

    2011-03-04

    Research highlights: {yields} The most important therapeutic tool in brain metastasis is radiation therapy. {yields} Radiosensitivity of cancer cells was enhanced with treatment of Chk1 inhibitor. {yields} Depletion of Chk1 in cancer cells showed an enhancement of sensitivity to radiation. {yields} Chk1 can be a good target for enhancement of radiosensitivity. -- Abstract: The most important therapeutic tool in brain metastasis is radiation therapy. However, resistance to radiation is a possible cause of recurrence or treatment failure. Recently, signal pathways about DNA damage checkpoints after irradiation have been noticed. We investigated the radiosensitivity can be enhanced with treatment of Chk1 inhibitor, AZD7762 in lung cancer cell lines and xenograft models of lung cancer brain metastasis. Clonogenic survival assays showed enhancement of radiosensitivity with AZD7762 after irradiation of various doses. AZD7762 increased ATR/ATM-mediated Chk1 phosphorylation and stabilized Cdc25A, suppressed cyclin A expression in lung cancer cell lines. In xenograft models of lung cancer (PC14PE6) brain metastasis, AZD7762 significantly prolonged the median survival time in response to radiation. Depletion of Chk1 using shRNA also showed an enhancement of sensitivity to radiation in PC14PE6 cells. The results of this study support that Chk1 can be a good target for enhancement of radiosensitivity.

  17. Inhibition of checkpoint kinase 1 sensitizes lung cancer brain metastases to radiotherapy

    International Nuclear Information System (INIS)

    Research highlights: → The most important therapeutic tool in brain metastasis is radiation therapy. → Radiosensitivity of cancer cells was enhanced with treatment of Chk1 inhibitor. → Depletion of Chk1 in cancer cells showed an enhancement of sensitivity to radiation. → Chk1 can be a good target for enhancement of radiosensitivity. -- Abstract: The most important therapeutic tool in brain metastasis is radiation therapy. However, resistance to radiation is a possible cause of recurrence or treatment failure. Recently, signal pathways about DNA damage checkpoints after irradiation have been noticed. We investigated the radiosensitivity can be enhanced with treatment of Chk1 inhibitor, AZD7762 in lung cancer cell lines and xenograft models of lung cancer brain metastasis. Clonogenic survival assays showed enhancement of radiosensitivity with AZD7762 after irradiation of various doses. AZD7762 increased ATR/ATM-mediated Chk1 phosphorylation and stabilized Cdc25A, suppressed cyclin A expression in lung cancer cell lines. In xenograft models of lung cancer (PC14PE6) brain metastasis, AZD7762 significantly prolonged the median survival time in response to radiation. Depletion of Chk1 using shRNA also showed an enhancement of sensitivity to radiation in PC14PE6 cells. The results of this study support that Chk1 can be a good target for enhancement of radiosensitivity.

  18. DNA damage activates a spatially distinct late cytoplasmic cell-cycle checkpoint network controlled by MK2-mediated RNA stabilization

    DEFF Research Database (Denmark)

    Reinhardt, H Christian; Hasskamp, Pia; Schmedding, Ingolf;

    2010-01-01

    Following genotoxic stress, cells activate a complex kinase-based signaling network to arrest the cell cycle and initiate DNA repair. p53-defective tumor cells rewire their checkpoint response and become dependent on the p38/MK2 pathway for survival after DNA damage, despite a functional ATR-Chk1...... pathway. We used functional genetics to dissect the contributions of Chk1 and MK2 to checkpoint control. We show that nuclear Chk1 activity is essential to establish a G(2)/M checkpoint, while cytoplasmic MK2 activity is critical for prolonged checkpoint maintenance through a process of...... posttranscriptional mRNA stabilization. Following DNA damage, the p38/MK2 complex relocalizes from nucleus to cytoplasm where MK2 phosphorylates hnRNPA0, to stabilize Gadd45α mRNA, while p38 phosphorylates and releases the translational inhibitor TIAR. In addition, MK2 phosphorylates PARN, blocking Gadd45α m...

  19. Cyclin-dependent kinase CDK1/CDC28 and checkpoints

    International Nuclear Information System (INIS)

    The genetic instability induced by defects in the cell cycle progression contributes to different human diseases, particularly neoplastic transformation. The control mechanisms of correct cell cycle progression are the most studied in the yeast Saccharomyces cerevisiae, in which checkpoint was first discovered. Many components of these processes have been identified by now. Here, the role of the central kinase of cell cycle CDK1/CDC28 is considered in checkpoint in different phases.

  20. Nuclear Chk1 prevents premature mitotic entry.

    Science.gov (United States)

    Matsuyama, Makoto; Goto, Hidemasa; Kasahara, Kousuke; Kawakami, Yoshitaka; Nakanishi, Makoto; Kiyono, Tohru; Goshima, Naoki; Inagaki, Masaki

    2011-07-01

    Chk1 inhibits the premature activation of the cyclin-B1-Cdk1. However, it remains controversial whether Chk1 inhibits Cdk1 in the centrosome or in the nucleus before the G2-M transition. In this study, we examined the specificity of the mouse monoclonal anti-Chk1 antibody DCS-310, with which the centrosome was stained. Conditional Chk1 knockout in mouse embryonic fibroblasts reduced nuclear but not centrosomal staining with DCS-310. In Chk1(+/myc) human colon adenocarcinoma (DLD-1) cells, Chk1 was detected in the nucleus but not in the centrosome using an anti-Myc antibody. Through the combination of protein array and RNAi technologies, we identified Ccdc-151 as a protein that crossreacted with DCS-310 on the centrosome. Mitotic entry was delayed by expression of the Chk1 mutant that localized in the nucleus, although forced immobilization of Chk1 to the centrosome had little impact on the timing of mitotic entry. These results suggest that nuclear but not centrosomal Chk1 contributes to correct timing of mitotic entry. PMID:21628425

  1. Targeting the DNA replication checkpoint by pharmacologic inhibition of Chk1 kinase: a strategy to sensitize APC mutant colon cancer cells to 5-fluorouracil chemotherapy

    OpenAIRE

    Martino-Echarri, Estefania; Henderson, Beric R.; Brocardo, Mariana G.

    2014-01-01

    5-fluorouracil (5-FU) is the first line component used in colorectal cancer (CRC) therapy however even in combination with other chemotherapeutic drugs recurrence is common. Mutations of the adenomatous polyposis coli (APC) gene are considered as the initiating step of transformation in familial and sporadic CRCs. We have previously shown that APC regulates the cellular response to DNA replication stress and recently hypothesized that APC mutations might therefore influence 5-FU resistance. T...

  2. CHK It Out! Blocking WEE Kinase Routs TP53 Mutant Cancer

    Science.gov (United States)

    Bauman, Julie E.; Chung, Christine H.

    2016-01-01

    Mutations in TP53, encoding the master tumor suppressor p53, have posed a developmental therapeutic dilemma due to inability to target loss of function. Inhibition of WEE1 or CHK1 kinase, negative regulators of the G2–M checkpoint, selectively sensitizes p53-deficient cells to exogenous DNA damage, abrogating G2 arrest and precipitating mitotic catastrophe. PMID:25125257

  3. Inhibition of human Chk1 causes increased initiation of DNA replication, phosphorylation of ATR targets, and DNA breakage

    DEFF Research Database (Denmark)

    Syljuåsen, Randi G; Sørensen, Claus Storgaard; Hansen, Lasse Tengbjerg;

    2005-01-01

    -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...

  4. CHK1 Inhibition Synergizes with Gemcitabine Initially by Destabilizing the DNA Replication Apparatus.

    Science.gov (United States)

    Koh, Siang-Boon; Courtin, Aurélie; Boyce, Richard J; Boyle, Robert G; Richards, Frances M; Jodrell, Duncan I

    2015-09-01

    Combining cell-cycle checkpoint kinase inhibitors with the DNA-damaging chemotherapeutic agent gemcitabine offers clinical appeal, with a mechanistic rationale based chiefly on abrogation of gemcitabine-induced G2-M checkpoint activation. However, evidence supporting this mechanistic rationale from chemosensitization studies has not been consistent. Here we report a systematic definition of how pancreatic cancer cells harboring mutant p53 respond to this combination therapy, by combining mathematical models with large-scale quantitative biologic analyses of single cells and cell populations. Notably, we uncovered a dynamic range of mechanistic effects at different ratios of gemcitabine and CHK1 inhibitors. Remarkably, effective synergy was attained even where cells exhibited an apparently functional G2-M surveillance mechanism, as exemplified by a lack of both overt premature CDK1 activation and S-phase mitotic entry. Consistent with these findings, S-G2 duration was extended in treated cells, leading to a definable set of lineage-dependent catastrophic fates. At synergistic drug concentrations, global replication stress was a distinct indicator of chemosensitization as characterized molecularly by an accumulation of S-phase cells with high levels of hyperphosphorylated RPA-loaded single-stranded DNA. In a fraction of these cells, persistent genomic damage was observed, including chromosomal fragmentation with a loss of centromeric regions that prevented proper kinetochore-microtubule attachment. Together, our results suggested a "foot-in-the-door" mechanism for drug synergy where cells were destroyed not by frank G2-M phase abrogation but rather by initiating a cumulative genotoxicity that deregulated DNA synthesis. PMID:26141863

  5. The budding yeast protein kinase Ipl1/Aurora allows the absence of tension to activate the spindle checkpoint

    OpenAIRE

    Biggins, Sue; Murray, Andrew W.

    2001-01-01

    The spindle checkpoint prevents cell cycle progression in cells that have mitotic spindle defects. Although several spindle defects activate the spindle checkpoint, the exact nature of the primary signal is unknown. We have found that the budding yeast member of the Aurora protein kinase family, Ipl1p, is required to maintain a subset of spindle checkpoint arrests. Ipl1p is required to maintain the spindle checkpoint that is induced by overexpression of the protein kinase Mps1. Inactivating I...

  6. A ruthenium polypyridyl intercalator stalls DNA replication forks, radiosensitizes human cancer cells and is enhanced by Chk1 inhibition.

    Science.gov (United States)

    Gill, Martin R; Harun, Siti Norain; Halder, Swagata; Boghozian, Ramon A; Ramadan, Kristijan; Ahmad, Haslina; Vallis, Katherine A

    2016-01-01

    Ruthenium(II) polypyridyl complexes can intercalate DNA with high affinity and prevent cell proliferation; however, the direct impact of ruthenium-based intercalation on cellular DNA replication remains unknown. Here we show the multi-intercalator [Ru(dppz)2(PIP)](2+) (dppz = dipyridophenazine, PIP = 2-(phenyl)imidazo[4,5-f][1,10]phenanthroline) immediately stalls replication fork progression in HeLa human cervical cancer cells. In response to this replication blockade, the DNA damage response (DDR) cell signalling network is activated, with checkpoint kinase 1 (Chk1) activation indicating prolonged replication-associated DNA damage, and cell proliferation is inhibited by G1-S cell-cycle arrest. Co-incubation with a Chk1 inhibitor achieves synergistic apoptosis in cancer cells, with a significant increase in phospho(Ser139) histone H2AX (γ-H2AX) levels and foci indicating increased conversion of stalled replication forks to double-strand breaks (DSBs). Normal human epithelial cells remain unaffected by this concurrent treatment. Furthermore, pre-treatment of HeLa cells with [Ru(dppz)2(PIP)](2+) before external beam ionising radiation results in a supra-additive decrease in cell survival accompanied by increased γ-H2AX expression, indicating the compound functions as a radiosensitizer. Together, these results indicate ruthenium-based intercalation can block replication fork progression and demonstrate how these DNA-binding agents may be combined with DDR inhibitors or ionising radiation to achieve more efficient cancer cell killing. PMID:27558808

  7. Jaridonin-induced G2/M phase arrest in human esophageal cancer cells is caused by reactive oxygen species-dependent Cdc2-tyr15 phosphorylation via ATM–Chk1/2–Cdc25C pathway

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yong-Cheng [Clinical Pharmacology Laboratory, Henan Province People' s Hospital, No. 7, Wei Wu Road, Zhengzhou, Henan (China); Su, Nan [Department of Quality Detection and Management, Henan University of Animal Husbandry and Economy, Zhengzhou, Henan (China); Shi, Xiao-Jing; Zhao, Wen; Ke, Yu [School of Pharmaceutical Sciences, Zhengzhou University, No. 100, Science Avenue, Zhengzhou, Henan (China); Zi, Xiaolin [Department of Urology, University of California, Irvine, Orange, CA (United States); Department of Pharmacology, University of California, Irvine, Orange, CA (United States); Department of Pharmaceutical Sciences, University of California, Irvine, Orange, CA (United States); Zhao, Ning-Min; Qin, Yu-Hua; Zhao, Hong-Wei [Clinical Pharmacology Laboratory, Henan Province People' s Hospital, No. 7, Wei Wu Road, Zhengzhou, Henan (China); Liu, Hong-Min, E-mail: liuhm@zzu.edu.cn [School of Pharmaceutical Sciences, Zhengzhou University, No. 100, Science Avenue, Zhengzhou, Henan (China)

    2015-01-15

    Jaridonin, a novel diterpenoid from Isodon rubescens, has been shown previously to inhibit proliferation of esophageal squamous cancer cells (ESCC) through G2/M phase cell cycle arrest. However, the involved mechanism is not fully understood. In this study, we found that the cell cycle arrest by Jaridonin was associated with the increased expression of phosphorylation of ATM at Ser1981 and Cdc2 at Tyr15. Jaridonin also resulted in enhanced phosphorylation of Cdc25C via the activation of checkpoint kinases Chk1 and Chk2, as well as in increased phospho-H2A.X (Ser139), which is known to be phosphorylated by ATM in response to DNA damage. Furthermore, Jaridonin-mediated alterations in cell cycle arrest were significantly attenuated in the presence of NAC, implicating the involvement of ROS in Jaridonin's effects. On the other hand, addition of ATM inhibitors reversed Jaridonin-related activation of ATM and Chk1/2 as well as phosphorylation of Cdc25C, Cdc2 and H2A.X and G2/M phase arrest. In conclusion, these findings identified that Jaridonin-induced cell cycle arrest in human esophageal cancer cells is associated with ROS-mediated activation of ATM–Chk1/2–Cdc25C pathway. - Highlights: • Jaridonin induced G2/M phase arrest through induction of redox imbalance. • Jaridonin increased the level of ROS through depleting glutathione in cell. • ATM–Chk1/2–Cdc25C were involved in Jaridonin-induced cell cycle arrest. • Jaridonin selectively inhibited cancer cell viability and cell cycle progression.

  8. Jaridonin-induced G2/M phase arrest in human esophageal cancer cells is caused by reactive oxygen species-dependent Cdc2-tyr15 phosphorylation via ATM–Chk1/2–Cdc25C pathway

    International Nuclear Information System (INIS)

    Jaridonin, a novel diterpenoid from Isodon rubescens, has been shown previously to inhibit proliferation of esophageal squamous cancer cells (ESCC) through G2/M phase cell cycle arrest. However, the involved mechanism is not fully understood. In this study, we found that the cell cycle arrest by Jaridonin was associated with the increased expression of phosphorylation of ATM at Ser1981 and Cdc2 at Tyr15. Jaridonin also resulted in enhanced phosphorylation of Cdc25C via the activation of checkpoint kinases Chk1 and Chk2, as well as in increased phospho-H2A.X (Ser139), which is known to be phosphorylated by ATM in response to DNA damage. Furthermore, Jaridonin-mediated alterations in cell cycle arrest were significantly attenuated in the presence of NAC, implicating the involvement of ROS in Jaridonin's effects. On the other hand, addition of ATM inhibitors reversed Jaridonin-related activation of ATM and Chk1/2 as well as phosphorylation of Cdc25C, Cdc2 and H2A.X and G2/M phase arrest. In conclusion, these findings identified that Jaridonin-induced cell cycle arrest in human esophageal cancer cells is associated with ROS-mediated activation of ATM–Chk1/2–Cdc25C pathway. - Highlights: • Jaridonin induced G2/M phase arrest through induction of redox imbalance. • Jaridonin increased the level of ROS through depleting glutathione in cell. • ATM–Chk1/2–Cdc25C were involved in Jaridonin-induced cell cycle arrest. • Jaridonin selectively inhibited cancer cell viability and cell cycle progression

  9. Mismatch repair-dependent G2 checkpoint induced by low doses of SN1 type methylating agents requires the ATR kinase.

    Science.gov (United States)

    Stojic, Lovorka; Mojas, Nina; Cejka, Petr; Di Pietro, Massimiliano; Ferrari, Stefano; Marra, Giancarlo; Jiricny, Josef

    2004-06-01

    S(N)1-type alkylating agents represent an important class of chemotherapeutics, but the molecular mechanisms underlying their cytotoxicity are unknown. Thus, although these substances modify predominantly purine nitrogen atoms, their toxicity appears to result from the processing of O(6)-methylguanine ((6Me)G)-containing mispairs by the mismatch repair (MMR) system, because cells with defective MMR are highly resistant to killing by these agents. In an attempt to understand the role of the MMR system in the molecular transactions underlying the toxicity of alkylating agents, we studied the response of human MMR-proficient and MMR-deficient cells to low concentrations of the prototypic methylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). We now show that MNNG treatment induced a cell cycle arrest that was absolutely dependent on functional MMR. Unusually, the cells arrested only in the second G(2) phase after treatment. Downstream targets of both ATM (Ataxia telangiectasia mutated) and ATR (ATM and Rad3-related) kinases were modified, but only the ablation of ATR, or the inhibition of CHK1, attenuated the arrest. The checkpoint activation was accompanied by the formation of nuclear foci containing the signaling and repair proteins ATR, the S(*)/T(*)Q substrate, gamma-H2AX, and replication protein A (RPA). The persistence of these foci implied that they may represent sites of irreparable damage. PMID:15175264

  10. Chemogenetic profiling identifies RAD17 as synthetically lethal with checkpoint kinase inhibition.

    Science.gov (United States)

    Shen, John Paul; Srivas, Rohith; Gross, Andrew; Li, Jianfeng; Jaehnig, Eric J; Sun, Su Ming; Bojorquez-Gomez, Ana; Licon, Katherine; Sivaganesh, Vignesh; Xu, Jia L; Klepper, Kristin; Yeerna, Huwate; Pekin, Daniel; Qiu, Chu Ping; van Attikum, Haico; Sobol, Robert W; Ideker, Trey

    2015-11-01

    Chemical inhibitors of the checkpoint kinases have shown promise in the treatment of cancer, yet their clinical utility may be limited by a lack of molecular biomarkers to identify specific patients most likely to respond to therapy. To this end, we screened 112 known tumor suppressor genes for synthetic lethal interactions with inhibitors of the CHEK1 and CHEK2 checkpoint kinases. We identified eight interactions, including the Replication Factor C (RFC)-related protein RAD17. Clonogenic assays in RAD17 knockdown cell lines identified a substantial shift in sensitivity to checkpoint kinase inhibition (3.5-fold) as compared to RAD17 wild-type. Additional evidence for this interaction was found in a large-scale functional shRNA screen of over 100 genotyped cancer cell lines, in which CHEK1/2 mutant cell lines were unexpectedly sensitive to RAD17 knockdown. This interaction was widely conserved, as we found that RAD17 interacts strongly with checkpoint kinases in the budding yeast Saccharomyces cerevisiae. In the setting of RAD17 knockdown, CHEK1/2 inhibition was found to be synergistic with inhibition of WEE1, another pharmacologically relevant checkpoint kinase. Accumulation of the DNA damage marker γH2AX following chemical inhibition or transient knockdown of CHEK1, CHEK2 or WEE1 was magnified by knockdown of RAD17. Taken together, our data suggest that CHEK1 or WEE1 inhibitors are likely to have greater clinical efficacy in tumors with RAD17 loss-of-function. PMID:26437225

  11. Role of Intrinsic and Extrinsic Factors in the Regulation of the Mitotic Checkpoint Kinase Bub1

    Science.gov (United States)

    Breit, Claudia; Bange, Tanja; Petrovic, Arsen; Weir, John R.; Müller, Franziska; Vogt, Doro; Musacchio, Andrea

    2015-01-01

    The spindle assembly checkpoint (SAC) monitors microtubule attachment to kinetochores to ensure accurate sister chromatid segregation during mitosis. The SAC members Bub1 and BubR1 are paralogs that underwent significant functional specializations during evolution. We report an in-depth characterization of the kinase domains of Bub1 and BubR1. BubR1 kinase domain binds nucleotides but is unable to deliver catalytic activity in vitro. Conversely, Bub1 is an active kinase regulated by intra-molecular phosphorylation at the P+1 loop. The crystal structure of the phosphorylated Bub1 kinase domain illustrates a hitherto unknown conformation of the P+1 loop docked into the active site of the Bub1 kinase. Both Bub1 and BubR1 bind Bub3 constitutively. A hydrodynamic characterization of Bub1:Bub3 and BubR1:Bub3 demonstrates both complexes to have 1:1 stoichiometry, with no additional oligomerization. Conversely, Bub1:Bub3 and BubR1:Bub3 combine to form a heterotetramer. Neither BubR1:Bub3 nor Knl1, the kinetochore receptor of Bub1:Bub3, modulate the kinase activity of Bub1 in vitro, suggesting autonomous regulation of the Bub1 kinase domain. We complement our study with an analysis of the Bub1 substrates. Our results contribute to the mechanistic characterization of a crucial cell cycle checkpoint. PMID:26658523

  12. In vivo role of checkpoint kinase 2 in signaling telomere dysfunction

    OpenAIRE

    García-Beccaria, María; Martínez, Paula; Flores, Juana M.; Blasco, Maria A.

    2014-01-01

    Checkpoint kinase 2 (CHK2) is a downstream effector of the DNA damage response (DDR). Dysfunctional telomeres, either owing to critical shortening or disruption of the shelterin complex, activate a DDR, which eventually results in cell cycle arrest, senescence and/or apoptosis. Successive generations of telomerase-deficient (Terc) mice show accelerated aging and shorter lifespan due to tissue atrophy and impaired organ regeneration associated to progressive telomere shortening. In contrast, m...

  13. HPV-positive HNSCC cell lines but not primary human fibroblasts are radiosensitized by the inhibition of Chk1

    International Nuclear Information System (INIS)

    Purpose: Despite the comparably high cure rates observed for HPV-positive HNSCC, there is still a great need for specific tumor radiosensitization due to the often severe side effects resulting from intense radiochemotherapy. We recently demonstrated that HPV-positive HNSCC cell lines are characterized by a defect in DNA double-strand break repair associated with a pronounced G2-arrest. Here we tested whether abrogation of this radiation-induced G2-arrest by the inhibition of Chk1 results in specific radiosensitization of HPV-positive HNSCC cells. Materials and methods: Experiments were performed with five HPV and p16-positive (93-VU-147T, UM-SCC-47, UT-SCC-45, UD-SCC-2, UPCI-SCC-154) and two HPV and p16-negative HNSCC cell lines, as well as two normal human fibroblast strains. Chk1 was inhibited by the selective inhibitor PF-00477736. Cell cycle distribution was determined by flow cytometry, Chk1-activity via Western blot and cell survival by colony formation assay. Results: With the exception of UPCI-SCC-154, the inhibition of Chk1 was found to abolish the pronounced radiation-induced G2-arrest in all HPV-positive cells utilized. All tumor cell lines that demonstrated the abrogation of G2-arrest also demonstrated radiosensitization. Notably, in G1-arrest-proficient normal human fibroblasts no radiosensitization was induced. Conclusion: Abrogation of the G2 checkpoint through the inhibition of Chk1 may be used to selectively increase the cellular radiosensitivity of HPV-positive HNSCC without affecting the surrounding normal tissue

  14. Regulation of Sphingolipid Biosynthesis by the Morphogenesis Checkpoint Kinase Swe1.

    Science.gov (United States)

    Chauhan, Neha; Han, Gongshe; Somashekarappa, Niranjanakumari; Gable, Kenneth; Dunn, Teresa; Kohlwein, Sepp D

    2016-01-29

    Sphingolipid (SL) biosynthesis is negatively regulated by the highly conserved endoplasmic reticulum-localized Orm family proteins. Defective SL synthesis in Saccharomyces cerevisiae leads to increased phosphorylation and inhibition of Orm proteins by the kinase Ypk1. Here we present evidence that the yeast morphogenesis checkpoint kinase, Swe1, regulates SL biosynthesis independent of the Ypk1 pathway. Deletion of the Swe1 kinase renders mutant cells sensitive to serine palmitoyltransferase inhibition due to impaired sphingoid long-chain base synthesis. Based on these data and previous results, we suggest that Swe1 kinase perceives alterations in SL homeostasis, activates SL synthesis, and may thus represent the missing regulatory link that controls the SL rheostat during the cell cycle. PMID:26634277

  15. Regulation of Sphingolipid Biosynthesis by the Morphogenesis Checkpoint Kinase Swe1*

    Science.gov (United States)

    Chauhan, Neha; Han, Gongshe; Somashekarappa, Niranjanakumari; Gable, Kenneth; Dunn, Teresa; Kohlwein, Sepp D.

    2016-01-01

    Sphingolipid (SL) biosynthesis is negatively regulated by the highly conserved endoplasmic reticulum-localized Orm family proteins. Defective SL synthesis in Saccharomyces cerevisiae leads to increased phosphorylation and inhibition of Orm proteins by the kinase Ypk1. Here we present evidence that the yeast morphogenesis checkpoint kinase, Swe1, regulates SL biosynthesis independent of the Ypk1 pathway. Deletion of the Swe1 kinase renders mutant cells sensitive to serine palmitoyltransferase inhibition due to impaired sphingoid long-chain base synthesis. Based on these data and previous results, we suggest that Swe1 kinase perceives alterations in SL homeostasis, activates SL synthesis, and may thus represent the missing regulatory link that controls the SL rheostat during the cell cycle. PMID:26634277

  16. Lyn tyrosine kinase promotes silencing of ATM-dependent checkpoint signaling during recovery from DNA double-strand breaks

    International Nuclear Information System (INIS)

    Highlights: • Inhibition of Src family kinases decreased γ-H2AX signal. • Inhibition of Src family increased ATM-dependent phosphorylation of Chk2 and Kap1. • shRNA-mediated knockdown of Lyn increased phosphorylation of Kap1 by ATM. • Ectopic expression of Src family kinase suppressed ATM-mediated Kap1 phosphorylation. • Src is involved in upstream signaling for inactivation of ATM signaling. - Abstract: DNA damage activates the DNA damage checkpoint and the DNA repair machinery. After initial activation of DNA damage responses, cells recover to their original states through completion of DNA repair and termination of checkpoint signaling. Currently, little is known about the process by which cells recover from the DNA damage checkpoint, a process called checkpoint recovery. Here, we show that Src family kinases promote inactivation of ataxia telangiectasia mutated (ATM)-dependent checkpoint signaling during recovery from DNA double-strand breaks. Inhibition of Src activity increased ATM-dependent phosphorylation of Chk2 and Kap1. Src inhibition increased ATM signaling both in G2 phase and during asynchronous growth. shRNA knockdown of Lyn increased ATM signaling. Src-dependent nuclear tyrosine phosphorylation suppressed ATM-mediated Kap1 phosphorylation. These results suggest that Src family kinases are involved in upstream signaling that leads to inactivation of the ATM-dependent DNA damage checkpoint

  17. Lyn tyrosine kinase promotes silencing of ATM-dependent checkpoint signaling during recovery from DNA double-strand breaks

    Energy Technology Data Exchange (ETDEWEB)

    Fukumoto, Yasunori, E-mail: fukumoto@faculty.chiba-u.jp; Kuki, Kazumasa; Morii, Mariko; Miura, Takahito; Honda, Takuya; Ishibashi, Kenichi; Hasegawa, Hitomi; Kubota, Sho; Ide, Yudai; Yamaguchi, Noritaka; Nakayama, Yuji; Yamaguchi, Naoto, E-mail: nyama@faculty.chiba-u.jp

    2014-09-26

    Highlights: • Inhibition of Src family kinases decreased γ-H2AX signal. • Inhibition of Src family increased ATM-dependent phosphorylation of Chk2 and Kap1. • shRNA-mediated knockdown of Lyn increased phosphorylation of Kap1 by ATM. • Ectopic expression of Src family kinase suppressed ATM-mediated Kap1 phosphorylation. • Src is involved in upstream signaling for inactivation of ATM signaling. - Abstract: DNA damage activates the DNA damage checkpoint and the DNA repair machinery. After initial activation of DNA damage responses, cells recover to their original states through completion of DNA repair and termination of checkpoint signaling. Currently, little is known about the process by which cells recover from the DNA damage checkpoint, a process called checkpoint recovery. Here, we show that Src family kinases promote inactivation of ataxia telangiectasia mutated (ATM)-dependent checkpoint signaling during recovery from DNA double-strand breaks. Inhibition of Src activity increased ATM-dependent phosphorylation of Chk2 and Kap1. Src inhibition increased ATM signaling both in G2 phase and during asynchronous growth. shRNA knockdown of Lyn increased ATM signaling. Src-dependent nuclear tyrosine phosphorylation suppressed ATM-mediated Kap1 phosphorylation. These results suggest that Src family kinases are involved in upstream signaling that leads to inactivation of the ATM-dependent DNA damage checkpoint.

  18. RPA mediates recombination repair during replication stress and is displaced from DNA by checkpoint signalling in human cells

    DEFF Research Database (Denmark)

    Sleeth, Kate M; Sørensen, Claus Storgaard; Issaeva, Natalia;

    2007-01-01

    The replication protein A (RPA) is involved in most, if not all, nuclear metabolism involving single-stranded DNA. Here, we show that RPA is involved in genome maintenance at stalled replication forks by the homologous recombination repair system in humans. Depletion of the RPA protein inhibited...... the formation of RAD51 nuclear foci after hydroxyurea-induced replication stalling leading to persistent unrepaired DNA double-strand breaks (DSBs). We demonstrate a direct role of RPA in homology directed recombination repair. We find that RPA is dispensable for checkpoint kinase 1 (Chk1) activation...... and that RPA directly binds RAD52 upon replication stress, suggesting a direct role in recombination repair. In addition we show that inhibition of Chk1 with UCN-01 decreases dissociation of RPA from the chromatin and inhibits association of RAD51 and RAD52 with DNA. Altogether, our data suggest a...

  19. The meiotic recombination checkpoint suppresses NHK-1 kinase to prevent reorganisation of the oocyte nucleus in Drosophila.

    Directory of Open Access Journals (Sweden)

    Oscar M Lancaster

    2010-10-01

    Full Text Available The meiotic recombination checkpoint is a signalling pathway that blocks meiotic progression when the repair of DNA breaks formed during recombination is delayed. In comparison to the signalling pathway itself, however, the molecular targets of the checkpoint that control meiotic progression are not well understood in metazoans. In Drosophila, activation of the meiotic checkpoint is known to prevent formation of the karyosome, a meiosis-specific organisation of chromosomes, but the molecular pathway by which this occurs remains to be identified. Here we show that the conserved kinase NHK-1 (Drosophila Vrk-1 is a crucial meiotic regulator controlled by the meiotic checkpoint. An nhk-1 mutation, whilst resulting in karyosome defects, does so independent of meiotic checkpoint activation. Rather, we find unrepaired DNA breaks formed during recombination suppress NHK-1 activity (inferred from the phosphorylation level of one of its substrates through the meiotic checkpoint. Additionally DNA breaks induced by X-rays in cultured cells also suppress NHK-1 kinase activity. Unrepaired DNA breaks in oocytes also delay other NHK-1 dependent nuclear events, such as synaptonemal complex disassembly and condensin loading onto chromosomes. Therefore we propose that NHK-1 is a crucial regulator of meiosis and that the meiotic checkpoint suppresses NHK-1 activity to prevent oocyte nuclear reorganisation until DNA breaks are repaired.

  20. Xenopus Cds1 Is Regulated by DNA-Dependent Protein Kinase and ATR during the Cell Cycle Checkpoint Response to Double-Stranded DNA Ends

    OpenAIRE

    McSherry, Troy D.; Mueller, Paul R.

    2004-01-01

    The checkpoint kinase Cds1 (Chk2) plays a key role in cell cycle checkpoint responses with functions in cell cycle arrest, DNA repair, and induction of apoptosis. Proper regulation of Cds1 is essential for appropriate cellular responses to checkpoint-inducing insults. While the kinase ATM has been shown to be important in the regulation of human Cds1 (hCds1), here we report that the kinases ATR and DNA-dependent protein kinase (DNA-PK) play more significant roles in the regulation of Xenopus ...

  1. The Aurora B kinase in chromosome biorientation and spindle checkpoint signalling

    Directory of Open Access Journals (Sweden)

    Veronica eKrenn

    2015-10-01

    Full Text Available Aurora B, a member of the Aurora family of serine/threonine protein kinases, is a key player in chromosome segregation. As part of a macromolecular complex known as the chromosome passenger complex, Aurora B concentrates early during mitosis in the proximity of centromeres and kinetochores, the sites of attachment of chromosomes to spindle microtubules. There, it contributes to a number of processes that impart fidelity to cell division, including kinetochore stabilization, kinetochore-microtubule attachment, and the regulation of a surveillance mechanism named the spindle assembly checkpoint. In the regulation of these processes, Aurora B is the fulcrum of a remarkably complex network of interactions that feed back on its localization and activation state. In this review we discuss the multiple roles of Aurora B during mitosis, focusing in particular on its role at centromeres and kinetochores. Many details of the network of interactions at these locations remain poorly understood, and we focus here on several crucial outstanding questions.

  2. Morphogenesis checkpoint kinase Swe1 is the executor of lipolysis-dependent cell-cycle progression.

    Science.gov (United States)

    Chauhan, Neha; Visram, Myriam; Cristobal-Sarramian, Alvaro; Sarkleti, Florian; Kohlwein, Sepp D

    2015-03-10

    Cell growth and division requires the precise duplication of cellular DNA content but also of membranes and organelles. Knowledge about the cell-cycle-dependent regulation of membrane and storage lipid homeostasis is only rudimentary. Previous work from our laboratory has shown that the breakdown of triacylglycerols (TGs) is regulated in a cell-cycle-dependent manner, by activation of the Tgl4 lipase by the major cyclin-dependent kinase Cdc28. The lipases Tgl3 and Tgl4 are required for efficient cell-cycle progression during the G1/S (Gap1/replication phase) transition, at the onset of bud formation, and their absence leads to a cell-cycle delay. We now show that defective lipolysis activates the Swe1 morphogenesis checkpoint kinase that halts cell-cycle progression by phosphorylation of Cdc28 at tyrosine residue 19. Saturated long-chain fatty acids and phytosphingosine supplementation rescue the cell-cycle delay in the Tgl3/Tgl4 lipase-deficient strain, suggesting that Swe1 activity responds to imbalanced sphingolipid metabolism, in the absence of TG degradation. We propose a model by which TG-derived sphingolipids are required to activate the protein phosphatase 2A (PP2A(Cdc55)) to attenuate Swe1 phosphorylation and its inhibitory effect on Cdc28 at the G1/S transition of the cell cycle. PMID:25713391

  3. Targeted Radiosensitization by the Chk1 Inhibitor SAR-020106

    Energy Technology Data Exchange (ETDEWEB)

    Borst, Gerben R., E-mail: g.borst@nki.nl [The Institute of Cancer Research, London (United Kingdom); Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam (Netherlands); McLaughlin, Martin; Kyula, Joan N.; Neijenhuis, Sari; Khan, Aadil; Good, James; Zaidi, Shane [The Institute of Cancer Research, London (United Kingdom); Powell, Ned G. [HPV Research Group, School of Medicine, Cardiff University, Cardiff (United Kingdom); Meier, Pascal; Collins, Ian; Garrett, Michelle D. [The Institute of Cancer Research, London (United Kingdom); Verheij, Marcel [Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam (Netherlands); Harrington, Kevin J. [The Institute of Cancer Research, London (United Kingdom)

    2013-03-15

    Purpose: To explore the activity of a potent Chk1 inhibitor (SAR-020106) in combination with radiation. Methods and Materials: Colony and mechanistic in vitro assays and a xenograft in vivo model. Results: SAR-020106 suppressed-radiation-induced G{sub 2}/M arrest and reduced clonogenic survival only in p53-deficient tumor cells. SAR-020106 promoted mitotic entry following irradiation in all cell lines, but p53-deficient cells were likely to undergo apoptosis or become aneuploid, while p53 wild-type cells underwent a postmitotic G{sub 1} arrest followed by subsequent normal cell cycle re-entry. Following combined treatment with SAR-020106 and radiation, homologous-recombination-mediated DNA damage repair was inhibited in all cell lines. A significant increase in the number of pan-γH2AX-staining apoptotic cells was observed only in p53-deficient cell lines. Efficacy was confirmed in vivo in a clinically relevant human head-and-neck cell carcinoma xenograft model. Conclusion: The Chk1 inhibitor SAR-020106 is a potent radiosensitizer in tumor cell lines defective in p53 signaling.

  4. DNA damage checkpoint kinase ATM regulates germination and maintains genome stability in seeds.

    Science.gov (United States)

    Waterworth, Wanda M; Footitt, Steven; Bray, Clifford M; Finch-Savage, William E; West, Christopher E

    2016-08-23

    Genome integrity is crucial for cellular survival and the faithful transmission of genetic information. The eukaryotic cellular response to DNA damage is orchestrated by the DNA damage checkpoint kinases ATAXIA TELANGIECTASIA MUTATED (ATM) and ATM AND RAD3-RELATED (ATR). Here we identify important physiological roles for these sensor kinases in control of seed germination. We demonstrate that double-strand breaks (DSBs) are rate-limiting for germination. We identify that desiccation tolerant seeds exhibit a striking transcriptional DSB damage response during germination, indicative of high levels of genotoxic stress, which is induced following maturation drying and quiescence. Mutant atr and atm seeds are highly resistant to aging, establishing ATM and ATR as determinants of seed viability. In response to aging, ATM delays germination, whereas atm mutant seeds germinate with extensive chromosomal abnormalities. This identifies ATM as a major factor that controls germination in aged seeds, integrating progression through germination with surveillance of genome integrity. Mechanistically, ATM functions through control of DNA replication in imbibing seeds. ATM signaling is mediated by transcriptional control of the cell cycle inhibitor SIAMESE-RELATED 5, an essential factor required for the aging-induced delay to germination. In the soil seed bank, seeds exhibit increased transcript levels of ATM and ATR, with changes in dormancy and germination potential modulated by environmental signals, including temperature and soil moisture. Collectively, our findings reveal physiological functions for these sensor kinases in linking genome integrity to germination, thereby influencing seed quality, crucial for plant survival in the natural environment and sustainable crop production. PMID:27503884

  5. Differential impact of diverse anticancer chemotherapeutics on the Cdc25A-degradation checkpoint pathway

    International Nuclear Information System (INIS)

    When exposed to DNA-damaging insults such as ionizing radiation (IR) or ultraviolet light (UV), mammalian cells activate checkpoint pathways to halt cell cycle progression or induce cell death. Here we examined the ability of five commonly used anticancer drugs with different mechanisms of action to activate the Chk1/Chk2-Cdc25A-CDK2/cyclin E cell cycle checkpoint pathway, previously shown to be induced by IR or UV. Whereas exposure of human cells to topoisomerase inhibitors camptothecin, etoposide, or adriamycin resulted in rapid (within 1 h) activation of the pathway including degradation of the Cdc25A phosphatase and inhibition of cyclin E/CDK2 kinase activity, taxol failed to activate this checkpoint even after a prolonged treatment. Unexpectedly, although the alkylating agent cisplatin also induced degradation of Cdc25A (albeit delayed, after 8-12 h), cyclin E/CDK2 activity was elevated and DNA synthesis continued, a phenomena that correlated with increased E2F1 protein levels and consequently enhanced expression of cyclin E. These results reveal a differential impact of various classes of anticancer chemotherapeutics on the Cdc25A-degradation pathway, and indicate that the kinetics of checkpoint induction, and the relative balance of key components within the DNA damage response network may dictate whether the treated cells arrest their cell cycle progression

  6. The DNA damage and the DNA replication checkpoints converge at the MBF transcription factor

    Science.gov (United States)

    Ivanova, Tsvetomira; Alves-Rodrigues, Isabel; Gómez-Escoda, Blanca; Dutta, Chaitali; DeCaprio, James A.; Rhind, Nick; Hidalgo, Elena; Ayté, José

    2013-01-01

    In fission yeast cells, Cds1 is the effector kinase of the DNA replication checkpoint. We previously showed that when the DNA replication checkpoint is activated, the repressor Yox1 is phosphorylated and inactivated by Cds1, resulting in activation of MluI-binding factor (MBF)–dependent transcription. This is essential to reinitiate DNA synthesis and for correct G1-to-S transition. Here we show that Cdc10, which is an essential part of the MBF core, is the target of the DNA damage checkpoint. When fission yeast cells are treated with DNA-damaging agents, Chk1 is activated and phosphorylates Cdc10 at its carboxy-terminal domain. This modification is responsible for the repression of MBF-dependent transcription through induced release of MBF from chromatin. This inactivation of MBF is important for survival of cells challenged with DNA-damaging agents. Thus Yox1 and Cdc10 couple normal cell cycle regulation in unperturbed conditions and the DNA replication and DNA damage checkpoints into a single transcriptional complex. PMID:24006488

  7. The DNA damage and the DNA replication checkpoints converge at the MBF transcription factor.

    Science.gov (United States)

    Ivanova, Tsvetomira; Alves-Rodrigues, Isabel; Gómez-Escoda, Blanca; Dutta, Chaitali; DeCaprio, James A; Rhind, Nick; Hidalgo, Elena; Ayté, José

    2013-11-01

    In fission yeast cells, Cds1 is the effector kinase of the DNA replication checkpoint. We previously showed that when the DNA replication checkpoint is activated, the repressor Yox1 is phosphorylated and inactivated by Cds1, resulting in activation of MluI-binding factor (MBF)-dependent transcription. This is essential to reinitiate DNA synthesis and for correct G1-to-S transition. Here we show that Cdc10, which is an essential part of the MBF core, is the target of the DNA damage checkpoint. When fission yeast cells are treated with DNA-damaging agents, Chk1 is activated and phosphorylates Cdc10 at its carboxy-terminal domain. This modification is responsible for the repression of MBF-dependent transcription through induced release of MBF from chromatin. This inactivation of MBF is important for survival of cells challenged with DNA-damaging agents. Thus Yox1 and Cdc10 couple normal cell cycle regulation in unperturbed conditions and the DNA replication and DNA damage checkpoints into a single transcriptional complex. PMID:24006488

  8. Xenopus Cds1 Is Regulated by DNA-Dependent Protein Kinase and ATR during the Cell Cycle Checkpoint Response to Double-Stranded DNA Ends

    Science.gov (United States)

    McSherry, Troy D.; Mueller, Paul R.

    2004-01-01

    The checkpoint kinase Cds1 (Chk2) plays a key role in cell cycle checkpoint responses with functions in cell cycle arrest, DNA repair, and induction of apoptosis. Proper regulation of Cds1 is essential for appropriate cellular responses to checkpoint-inducing insults. While the kinase ATM has been shown to be important in the regulation of human Cds1 (hCds1), here we report that the kinases ATR and DNA-dependent protein kinase (DNA-PK) play more significant roles in the regulation of Xenopus Cds1 (XCds1). Under normal cell cycle conditions, nonactivated XCds1 constitutively associates with a Xenopus ATR complex. The association of XCds1 with this complex does not require a functional forkhead activation domain but does require a putative SH3 binding region that is found in XCds1. In response to double-stranded DNA ends, the amino terminus of XCds1 is rapidly phosphorylated in a sequential pattern. First DNA-PK phosphorylates serine 39, a site not previously recognized as important in Cds1 regulation. Xenopus ATM, ATR, and/or DNA-PK then phosphorylate three consensus serine/glutamine sites. Together, these phosphorylations have the dual function of inducing dissociation from the ATR complex and independently promoting the full activation of XCds1. Thus, the checkpoint-mediated activation of XCds1 requires phosphorylation by multiple phosphoinositide 3-kinase-related kinases, protein-protein dissociation, and autophosphorylation. PMID:15509799

  9. Study on the interaction between a new radioresistance-related protein AA12 and CHK1

    International Nuclear Information System (INIS)

    Objective: To study the interaction between AA12 and CHK1 proteins. Methods: Polyclonal antibody was made using expressed and purified AA12 (LG21) protein in E. coli. The specificity of antibody was identified by Western blot and the immunoprecipitations in Al-5 and B4 cells were done by AA12 antibody and CHK1 antibody. Meanwhile, AA12 and Chk1 genes were subcloned into the vectors of two-hybrid system, and the recombinant plasmids were transformed into yeast cell AH109. The expression of reporter genes were tested. Results: Western blot result showed that this antibody could bind with AA12 protein specifically; then in order to identify the interaction between two proteins in mammalian cells, the interaction between AA12 and CHK1 was identified in vivo by immunoprecipitation. On the other hand, the interaction between two proteins was identified in yeast by using two-hybrid system. The results of both α- and β-galactosidase assays were positive. Conclusion: The results showed that AA12 and CHK1 proteins could interact with each other, this would be important for studying a new function of AA12 gene

  10. Cdk2 is required for p53-independent G2/M checkpoint control.

    Directory of Open Access Journals (Sweden)

    Jon H Chung

    2010-02-01

    Full Text Available The activation of phase-specific cyclin-dependent kinases (Cdks is associated with ordered cell cycle transitions. Among the mammalian Cdks, only Cdk1 is essential for somatic cell proliferation. Cdk1 can apparently substitute for Cdk2, Cdk4, and Cdk6, which are individually dispensable in mice. It is unclear if all functions of non-essential Cdks are fully redundant with Cdk1. Using a genetic approach, we show that Cdk2, the S-phase Cdk, uniquely controls the G(2/M checkpoint that prevents cells with damaged DNA from initiating mitosis. CDK2-nullizygous human cells exposed to ionizing radiation failed to exclude Cdk1 from the nucleus and exhibited a marked defect in G(2/M arrest that was unmasked by the disruption of P53. The DNA replication licensing protein Cdc6, which is normally stabilized by Cdk2, was physically associated with the checkpoint regulator ATR and was required for efficient ATR-Chk1-Cdc25A signaling. These findings demonstrate that Cdk2 maintains a balance of S-phase regulatory proteins and thereby coordinates subsequent p53-independent G(2/M checkpoint activation.

  11. Checkpoint kinase inhibitors: SAR and radioprotective properties of a series of 2-arylbenzimidazoles.

    Science.gov (United States)

    Arienti, Kristen L; Brunmark, Anders; Axe, Frank U; McClure, Kelly; Lee, Alice; Blevitt, Jon; Neff, Danielle K; Huang, Liming; Crawford, Shelby; Pandit, Chennagiri R; Karlsson, Lars; Breitenbucher, J Guy

    2005-03-24

    The discovery of a series of novel, potent, and highly selective inhibitors of the DNA damage control kinase chk2 is disclosed. Here we report the first SAR study around inhibitors of this kinase. High-throughput screening of purified human chk2 led to the identification of a novel series of 2-arylbenzimidazole inhibitors of the kinase. Optimization was facilitated using homology models of chk2 and docking of inhibitors, leading to the highly potent 2-arylbenzimidazole 2h (IC(50) 15 nM). Compound 2h is an ATP-competitive inhibitor of chk2 that dose dependently protects human CD4(+) and CD8(+) T-cells from apoptosis due to ionizing radiation. This work suggests that a selective small molecule inhibitor of chk2 could be a useful adjuvant to radiotherapy, increasing the therapeutic window of such treatment. PMID:15771432

  12. The Meiotic Recombination Checkpoint Suppresses NHK-1 Kinase to Prevent Reorganisation of the Oocyte Nucleus in Drosophila

    OpenAIRE

    Lancaster, Oscar M.; Breuer, Manuel; Cullen, C. Fiona; Ito, Takashi; Ohkura, Hiroyuki

    2010-01-01

    The meiotic recombination checkpoint is a signalling pathway that blocks meiotic progression when the repair of DNA breaks formed during recombination is delayed. In comparison to the signalling pathway itself, however, the molecular targets of the checkpoint that control meiotic progression are not well understood in metazoans. In Drosophila, activation of the meiotic checkpoint is known to prevent formation of the karyosome, a meiosis-specific organisation of chromosomes, but the molecular ...

  13. Chk1 phosphorylated at serine345 is a predictor of early local recurrence and radio-resistance in breast cancer.

    Science.gov (United States)

    Alsubhi, Nouf; Middleton, Fiona; Abdel-Fatah, Tarek M A; Stephens, Peter; Doherty, Rachel; Arora, Arvind; Moseley, Paul M; Chan, Stephen Y T; Aleskandarany, Mohammed A; Green, Andrew R; Rakha, Emad A; Ellis, Ian O; Martin, Stewart G; Curtin, Nicola J; Madhusudan, Srinivasan

    2016-02-01

    Radiation-induced DNA damage activates the DNA damage response (DDR). DDR up-regulation may predict radio-resistance and increase the risk of early local recurrence despite radiotherapy in early stage breast cancers. In 1755 early stage breast cancers, DDR signalling [ATM, ATR, total Ckh1, Chk1 phosphorylated at serine(345) (pChk1), Chk2, p53], base excision repair [PARP1, POLβ, XRCC1, FEN1, SMUG1], non-homologous end joining (Ku70/Ku80, DNA-PKcs) and homologous recombination [RAD51, BRCA1, γH2AX, BLM, WRN, RECQL5, PTEN] protein expression was correlated to time to early local recurrence. Pre-clinically, radio-sensitization by inhibition of Chk1 activation by ATR inhibitor (VE-821) and inhibition of Chk1 (V158411) were investigated in MDA-MB-231 (p53 mutant) and MCF-7 (p53 wild-type) breast cancer cells. In the whole cohort, 208/1755 patients (11.9%) developed local recurrence of which 126 (61%) developed local recurrence within 5 years of initiation of primary therapy. Of the 20 markers tested, only pChk1 and p53 significantly associated with early local recurrence (p value = 0.015 and 0.010, respectively). When analysed together, high cytoplasmic pChk1-nuclear pChk1 (p = 0.039), high cytoplasmic pChk1-p53 (p = 0.004) and high nuclear pChk1-p53 (p = 0.029) co-expression remain significantly linked to early local recurrence. In multivariate analysis, cytoplasmic pChk1 level independently predicted early local recurrence (p = 0.025). In patients who received adjuvant local radiotherapy (n = 949), p53 (p = 0.014) and high cytoplasmic pChk1-p53 (p = 0.017) remain associated with early local recurrence. Pre-clinically, radio-sensitisation by VE-821 or V158411 was observed in both MCF-7 and MDA-MB-231 cells and was more pronounced in MCF-7 cells. We conclude that pChk1 is a predictive biomarker of radiotherapy resistance and early local recurrence. PMID:26459098

  14. THE ROLE OF CHK1 IN MEIOTIC MATURATION OF MOUSE OOCYTES

    Czech Academy of Sciences Publication Activity Database

    Mayer, Alexandra; Šolc, Petr; Baran, V.; Böhmová, Tereza; Motlík, Jan

    Montpellier : EMBO, 2011. s. 171-171. [15th European Cell Cycle Conference and EMBO Workshop. 02.09.2011-05.09.2011, Montpellier] R&D Projects: GA ČR(CZ) GC301/09/J036 Institutional research plan: CEZ:AV0Z50450515 Keywords : mouse oocytes * CHK1 * meiotic maturation Subject RIV: EB - Genetics ; Molecular Biology http://events.embo.org/11-cell-cycle/

  15. Centromere-tethered Mps1 pombe homolog (Mph1) kinase is a sufficient marker for recruitment of the spindle checkpoint protein Bub1, but not Mad1.

    Science.gov (United States)

    Ito, Daisuke; Saito, Yu; Matsumoto, Tomohiro

    2012-01-01

    The spindle checkpoint delays the onset of anaphase until all of the chromosomes properly achieve bipolar attachment to the spindle. It has been shown that unattached kinetochores are the site that emits a signal for activation of the checkpoint. Although the components of the checkpoint such as Bub1, Mad1 and Mad2 selectively accumulate at unattached kinetochores, the answer to how they recognize unattached kinetochores has remained elusive. Mps1 pombe homolog (Mph1) kinase has been shown to function upstream of most of the components of the checkpoint and thus it is thought to recognize unattached kinetochores by itself and recruit other components. In this study we have expressed a fusion protein of Mph1 and Ndc80 (a kinetochore protein of the outer plate) and shown that the fusion protein arrests cell cycle progression in a spindle-checkpoint\\x{2013}dependent manner in fission yeast. When expression of Mad2 is turned off, the cells grow normally with Mph1 constitutively localized at centromeres/kinetochores. Under this condition, Bub1 can be found with Mph1 throughout the cell cycle, indicating that localization of Mph1 at centromeres/kinetochores is sufficient to recruit Bub1. In contrast, Mad1 is found to transiently localize at kinetochores, which are presumably unattached to the spindle, but soon it dissociates from kinetochores. We propose that Mph1 is a sufficient marker for recruitment of Bub1. Mad1, in contrast, requires an additional condition/component for stable association with kinetochores. PMID:22184248

  16. Inhibition of autophagy enhances DNA damage-induced apoptosis by disrupting CHK1-dependent S phase arrest

    International Nuclear Information System (INIS)

    DNA damage has been shown to induce autophagy, but the role of autophagy in the DNA damage response and cell fate is not fully understood. BO-1012, a bifunctional alkylating derivative of 3a-aza-cyclopenta[a]indene, is a potent DNA interstrand cross-linking agent with anticancer activity. In this study, BO-1012 was found to reduce DNA synthesis, inhibit S phase progression, and induce phosphorylation of histone H2AX on serine 139 (γH2AX) exclusively in S phase cells. Both CHK1 and CHK2 were phosphorylated in response to BO-1012 treatment, but only depletion of CHK1, but not CHK2, impaired BO-1012-induced S phase arrest and facilitated the entry of γH2AX-positive cells into G2 phase. CHK1 depletion also significantly enhanced BO-1012-induced cell death and apoptosis. These results indicate that BO-1012-induced S phase arrest is a CHK1-dependent pro-survival response. BO-1012 also resulted in marked induction of acidic vesicular organelle (AVO) formation and microtubule-associated protein 1 light chain 3 (LC3) processing and redistribution, features characteristic of autophagy. Depletion of ATG7 or co-treatment of cells with BO-1012 and either 3-methyladenine or bafilomycin A1, two inhibitors of autophagy, not only reduced CHK1 phosphorylation and disrupted S phase arrest, but also increased cleavage of caspase-9 and PARP, and cell death. These results suggest that cells initiate S phase arrest and autophagy as pro-survival responses to BO-1012-induced DNA damage, and that suppression of autophagy enhances BO-1012-induced apoptosis via disruption of CHK1-dependent S phase arrest. - Highlights: • Autophagy inhibitors enhanced the cytotoxicity of a DNA alkylating agent, BO-1012. • BO-1012-induced S phase arrest was a CHK1-dependent pro-survival response. • Autophagy inhibition enhanced BO-1012 cytotoxicity via disrupting the S phase arrest

  17. Inhibition of autophagy enhances DNA damage-induced apoptosis by disrupting CHK1-dependent S phase arrest

    Energy Technology Data Exchange (ETDEWEB)

    Liou, Jong-Shian; Wu, Yi-Chen; Yen, Wen-Yen; Tang, Yu-Shuan [Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan, ROC (China); Kakadiya, Rajesh B.; Su, Tsann-Long [Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan, ROC (China); Yih, Ling-Huei, E-mail: lhyih@gate.sinica.edu.tw [Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan, ROC (China)

    2014-08-01

    DNA damage has been shown to induce autophagy, but the role of autophagy in the DNA damage response and cell fate is not fully understood. BO-1012, a bifunctional alkylating derivative of 3a-aza-cyclopenta[a]indene, is a potent DNA interstrand cross-linking agent with anticancer activity. In this study, BO-1012 was found to reduce DNA synthesis, inhibit S phase progression, and induce phosphorylation of histone H2AX on serine 139 (γH2AX) exclusively in S phase cells. Both CHK1 and CHK2 were phosphorylated in response to BO-1012 treatment, but only depletion of CHK1, but not CHK2, impaired BO-1012-induced S phase arrest and facilitated the entry of γH2AX-positive cells into G2 phase. CHK1 depletion also significantly enhanced BO-1012-induced cell death and apoptosis. These results indicate that BO-1012-induced S phase arrest is a CHK1-dependent pro-survival response. BO-1012 also resulted in marked induction of acidic vesicular organelle (AVO) formation and microtubule-associated protein 1 light chain 3 (LC3) processing and redistribution, features characteristic of autophagy. Depletion of ATG7 or co-treatment of cells with BO-1012 and either 3-methyladenine or bafilomycin A1, two inhibitors of autophagy, not only reduced CHK1 phosphorylation and disrupted S phase arrest, but also increased cleavage of caspase-9 and PARP, and cell death. These results suggest that cells initiate S phase arrest and autophagy as pro-survival responses to BO-1012-induced DNA damage, and that suppression of autophagy enhances BO-1012-induced apoptosis via disruption of CHK1-dependent S phase arrest. - Highlights: • Autophagy inhibitors enhanced the cytotoxicity of a DNA alkylating agent, BO-1012. • BO-1012-induced S phase arrest was a CHK1-dependent pro-survival response. • Autophagy inhibition enhanced BO-1012 cytotoxicity via disrupting the S phase arrest.

  18. NDR1 modulates the UV-induced DNA-damage checkpoint and nucleotide excision repair

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jeong-Min; Choi, Ji Ye [Department of Biological Science, Dong-A University, Busan (Korea, Republic of); Yi, Joo Mi [Research Center, Dongnam Institute of Radiological & Medical Sciences, Busan (Korea, Republic of); Chung, Jin Woong; Leem, Sun-Hee; Koh, Sang Seok [Department of Biological Science, Dong-A University, Busan (Korea, Republic of); Kang, Tae-Hong, E-mail: thkang@dau.ac.kr [Department of Biological Science, Dong-A University, Busan (Korea, Republic of)

    2015-06-05

    Nucleotide excision repair (NER) is the sole mechanism of UV-induced DNA lesion repair in mammals. A single round of NER requires multiple components including seven core NER factors, xeroderma pigmentosum A–G (XPA–XPG), and many auxiliary effector proteins including ATR serine/threonine kinase. The XPA protein helps to verify DNA damage and thus plays a rate-limiting role in NER. Hence, the regulation of XPA is important for the entire NER kinetic. We found that NDR1, a novel XPA-interacting protein, modulates NER by modulating the UV-induced DNA-damage checkpoint. In quiescent cells, NDR1 localized mainly in the cytoplasm. After UV irradiation, NDR1 accumulated in the nucleus. The siRNA knockdown of NDR1 delayed the repair of UV-induced cyclobutane pyrimidine dimers in both normal cells and cancer cells. It did not, however, alter the expression levels or the chromatin association levels of the core NER factors following UV irradiation. Instead, the NDR1-depleted cells displayed reduced activity of ATR for some set of its substrates including CHK1 and p53, suggesting that NDR1 modulates NER indirectly via the ATR pathway. - Highlights: • NDR1 is a novel XPA-interacting protein. • NDR1 accumulates in the nucleus in response to UV irradiation. • NDR1 modulates NER (nucleotide excision repair) by modulating the UV-induced DNA-damage checkpoint response.

  19. NDR1 modulates the UV-induced DNA-damage checkpoint and nucleotide excision repair

    International Nuclear Information System (INIS)

    Nucleotide excision repair (NER) is the sole mechanism of UV-induced DNA lesion repair in mammals. A single round of NER requires multiple components including seven core NER factors, xeroderma pigmentosum A–G (XPA–XPG), and many auxiliary effector proteins including ATR serine/threonine kinase. The XPA protein helps to verify DNA damage and thus plays a rate-limiting role in NER. Hence, the regulation of XPA is important for the entire NER kinetic. We found that NDR1, a novel XPA-interacting protein, modulates NER by modulating the UV-induced DNA-damage checkpoint. In quiescent cells, NDR1 localized mainly in the cytoplasm. After UV irradiation, NDR1 accumulated in the nucleus. The siRNA knockdown of NDR1 delayed the repair of UV-induced cyclobutane pyrimidine dimers in both normal cells and cancer cells. It did not, however, alter the expression levels or the chromatin association levels of the core NER factors following UV irradiation. Instead, the NDR1-depleted cells displayed reduced activity of ATR for some set of its substrates including CHK1 and p53, suggesting that NDR1 modulates NER indirectly via the ATR pathway. - Highlights: • NDR1 is a novel XPA-interacting protein. • NDR1 accumulates in the nucleus in response to UV irradiation. • NDR1 modulates NER (nucleotide excision repair) by modulating the UV-induced DNA-damage checkpoint response

  20. Sequence Classification: 889584 [

    Lifescience Database Archive (English)

    Full Text Available by checkpoint signal transducer kinase Mec1p; homolog of S. pombe and mammalian Chk1 checkpoint kinase; Chk1p || http://www.ncbi.nlm.nih.gov/protein/6319751 ... ... checkpoint effector kinase, mediates mitotic cell cycle arrest via phosphorylation of Pds1p; phosphorylated

  1. Differential genetic interactions between Sgs1, DNA-damage checkpoint components and DNA repair factors in the maintenance of chromosome stability

    Directory of Open Access Journals (Sweden)

    Doerfler Lillian

    2011-10-01

    Full Text Available Abstract Background Genome instability is associated with human cancers and chromosome breakage syndromes, including Bloom's syndrome, caused by inactivation of BLM helicase. Numerous mutations that lead to genome instability are known, yet how they interact genetically is poorly understood. Results We show that spontaneous translocations that arise by nonallelic homologous recombination in DNA-damage-checkpoint-defective yeast lacking the BLM-related Sgs1 helicase (sgs1Δ mec3Δ are inhibited if cells lack Mec1/ATR kinase. Tel1/ATM, in contrast, acts as a suppressor independently of Mec3 and Sgs1. Translocations are also inhibited in cells lacking Dun1 kinase, but not in cells defective in a parallel checkpoint branch defined by Chk1 kinase. While we had previously shown that RAD51 deletion did not inhibit translocation formation, RAD59 deletion led to inhibition comparable to the rad52Δ mutation. A candidate screen of other DNA metabolic factors identified Exo1 as a strong suppressor of chromosomal rearrangements in the sgs1Δ mutant, becoming even more important for chromosomal stability upon MEC3 deletion. We determined that the C-terminal third of Exo1, harboring mismatch repair protein binding sites and phosphorylation sites, is dispensable for Exo1's roles in chromosomal rearrangement suppression, mutation avoidance and resistance to DNA-damaging agents. Conclusions Our findings suggest that translocations between related genes can form by Rad59-dependent, Rad51-independent homologous recombination, which is independently suppressed by Sgs1, Tel1, Mec3 and Exo1 but promoted by Dun1 and the telomerase-inhibitor Mec1. We propose a model for the functional interaction between mitotic recombination and the DNA-damage checkpoint in the suppression of chromosomal rearrangements in sgs1Δ cells.

  2. In silico analysis of deleterious single nucleotide polymorphisms in human BUB1 mitotic checkpoint serine/threonine kinase B gene.

    Science.gov (United States)

    Akhoundi, Fatemeh; Parvaneh, Nikpour; Modjtaba, Emadi-Baygi

    2016-09-01

    One of the major challenges in the analysis of human genetic variation is to distinguish mutations that are functionally neutral from those that contribute to disease. BubR1 is a key protein mediating spindle-checkpoint activation that plays a role in the inhibition of the anaphase-promoting complex/cyclosome (APC/C), delaying the onset of anaphase and ensuring proper chromosome segregation. Owing to the importance of BUB1B gene in mitotic checkpoint a functional analysis using different in silico approaches was undertaken to explore the possible associations between genetic mutations and phenotypic variation. In this work we found that 3 nsSNPs I82N, P334L and R814H have a functional effect on protein function and stability. A literature search revealed that R814H was already implicated in human diseases. Additionally, 2 SNPs in the 5' UTR region was predicted to exhibit a pattern change in the internal ribosome entry site (IRES), and eight MicroRNA binding sites were found to be highly affected due to 3' UTR SNPs. These in silico predictions will provide useful information in selecting the target SNPs that are likely to have functional impact on the BUB1B gene. PMID:27331020

  3. Role for Rif1 in the checkpoint response to damaged DNA in Xenopus egg extracts

    OpenAIRE

    Kumar, Sanjay; Yoo, Hae Yong; Kumagai, Akiko; Shevchenko, Anna; Shevchenko, Andrej; Dunphy, William G.

    2012-01-01

    TopBP1 is critical for both DNA replication and checkpoint regulation in vertebrate cells. In this study, we have identified Rif1 as a binding partner of TopBP1 in Xenopus egg extracts. In addition, Rif1 also interacts with both ATM and the Mre11-Rad50-Nbs1 (MRN) complex, which are key regulators of checkpoint responses to double-stranded DNA breaks (DSBs). Depletion of Rif1 from egg extracts compromises the activation of Chk1 in response to DSBs but not stalled replication forks. Removal of ...

  4. Inactivating the spindle checkpoint kinase Bub1 during embryonic development results in a global shutdown of proliferation

    Directory of Open Access Journals (Sweden)

    Taylor Stephen S

    2009-09-01

    Full Text Available Abstract Background Bub1 is a component of the spindle assembly checkpoint, a surveillance mechanism that maintains chromosome stability during M-phase. Bub1 is essential during the early stages of embryogenesis, with homozygous BUB1-null mice dying shortly after day E3.5. Bub1 is also required later during embryogenesis; inactivation of BUB1 on day E10.5 appears to rapidly block all further development. However, the mechanism(s responsible for this phenotype remain unclear. Findings Here we show that inactivating BUB1 on day E10.5 stalls embryogenesis within 48 hours. This is accompanied by a global shutdown of proliferation, widespread apoptosis and haemorrhaging. Conclusion Our results suggest that Bub1 is required throughout the developing embryo for cellular proliferation. Therefore, Bub1 has been shown to be essential in all scenarios analyzed thus far in mice: proliferation of cultured fibroblasts, spermatogenesis, oogenesis and both early and late embryonic development. This likely reflects the fact that Bub1 has dual functions during mitosis, being required for both SAC function and chromosome alignment.

  5. Berberine, a genotoxic alkaloid, induces ATM-Chk1 mediated G2 arrest in prostate cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yu; Liu Qiao; Liu Zhaojian; Li Boxuan; Sun Zhaoliang; Zhou Haibin; Zhang Xiyu; Gong Yaoqin [Ministry of Education Key Laboratory of Experimental Teratology and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan (China); Shao Changshun, E-mail: changshun.shao@gmail.com [Ministry of Education Key Laboratory of Experimental Teratology and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan (China)

    2012-06-01

    Berberine has been shown to possess anti-tumor activity against a wide spectrum of cancer cells. It inhibits cancer cell proliferation by inducing cell cycle arrest, at G1 and/or G2/M, and apoptosis. While it has been documented that berberine induces G1 arrest by activating the p53-p21 cascade, it remains unclear what mechanism underlies the berberine-induced G2/M arrest, which is p53-independent. In this study, we tested the anti-proliferative effect of berberine on murine prostate cancer cell line RM-1 and characterized the underlying mechanisms. Berberine dose-dependently induced DNA double-strand breaks and apoptosis. At low concentrations, berberine was observed to induce G1 arrest, concomitant with the activation of p53-p21 cascade. Upon exposure to berberine at a higher concentration (50 {mu}M) for 24 h, cells exhibited G2/M arrest. Pharmacological inhibition of ATM by KU55933, or Chk1 by UCN-01, could efficiently abrogate the G2/M arrest in berberine-treated cells. Downregulation of Chk1 by RNA interference also abolished the G2/M arrest caused by berberine, confirming the role of Chk1 in the pathway leading to G2/M arrest. Abrogation of G2/M arrest by ATM inhibition forced more cells to undergo apoptosis in response to berberine treatment. Chk1 inhibition by UCN-01, on the other hand, rendered cells more sensitive to berberine only when p53 was inhibited. Our results suggest that combined administration of berberine and caffeine, or other ATM inhibitor, may accelerate the killing of cancer cells.

  6. Immune checkpoints

    OpenAIRE

    Chawla, Akhil; Philips, Anne V; Alatrash, Gheath; Mittendorf, Elizabeth,

    2014-01-01

    Early clinical trials investigating monoclonal antibodies targeting the T-cell inhibitory receptor programmed cell death 1 (PD-1) and its ligand PD-L1 have shown efficacy in melanoma, non-small cell lung cancer and renal cell carcinoma. We recently demonstrated PD-L1 expression in 20% of triple negative breast cancers suggesting that targeting the PD-1/PD-L1 immune checkpoint may be an effective treatment modality in patients with this disease.

  7. The effect of heavy ion on DNA damage checkpoint, and the discovery of its sensitizing compounds

    International Nuclear Information System (INIS)

    In the present study, we demonstrated that a persimmon leaf extract (PLE) promoted cytotoxic effect of cancer cells by chemotherapeutic agents inhibiting the DNA checkpoint activity. Therefore, PLE is a strong possibility of sensitizing agents for heavy ion cancer therapy. Herein, we investigate the mechanism of cellular responses to DNA damage induced by heavy ion radiation with PLE. Human adenocarcinoma A549 cells were pre-incubated with PLE (0, 1, 10, 30 μg/mL) at one hour. After pre-incubation, the cells were irradiated with carbon-ion beams [135C (linear energy transfer (LET) 70 Kev/um)]. The phosphorylation of p53, Chk1 and SMC1 was increased by 2.5 Gy heavy ion exposure. PLE decreased the phosphorylation of p53, Chk1 and SMC1 in cells damaged by heavy ion with PLE dose-dependent manner. G2/M checkpoint was investigated in percentage of mitotic cell. The percentage of mitotic cell decreased in heavy ion beam treatment. Interestingly, heavy ion with PLE treatment was significantly increased. The result indicated that PLE treatment disrupted the G2/M checkpoint activated by heavy ion. These results indicated that DNA damage checkpoint system in heavy ion exposed cells were abrogated by PLE treatment through the inhibition of ataxia telangiectasia mutated (ATM) and/or AT and Rad3 related (ATR)-dependent signaling pathway. (author)

  8. The effect of ataxia-telangiectasia mutated kinase-dependent hyperphosphorylation of checkpoint kinase-2 on oligodeoxynucleotide 7909 containing CpG motifs-enhanced sensitivity to X-rays in human lung adenocarcinoma A549 cells

    Directory of Open Access Journals (Sweden)

    Liu XQ

    2015-06-01

    Full Text Available Xiaoqun Liu,1,* Xiangdong Liu,2,* Tiankui Qiao,1 Wei Chen,1 Sujuan Yuan1 1Department of Oncology, 2Department of Ophthalmology, Affiliated Jinshan Hospital, Fudan University, Shanghai, People’s Republic of China *These authors contributed equally to this work Objective: The aim of the study reported here was to further investigate the potential effect of ataxia-telangiectasia mutated (ATM kinase-dependent hyperphosphorylation of checkpoint kinase-2 (Chk2 on radiosensitivity enhanced by oligodeoxynucleotide 7909 containing CpG motifs (CpG ODN7909 in human lung adenocarcinoma A549 cells. Methods: In vitro A549 cells were randomly separated into control, CpG, X-ray, CpG+X-ray, ATM kinase-small interfering RNA (siRNA+CpG+X-ray (ATM-siRNA, and Chk2-siRNA+CpG+X-ray (Chk2-siRNA groups. siRNAs were adopted to silence the ATM and Chk2 genes. Expression and phosphorylation of ATM kinase and Chk2 were detected by Western blot assay. Cell colonies were observed under inverted phase-contrast microscopy. Cellular survival curves were fitted using a multi-target single-hitting model. Cell cycle and apoptosis were analyzed by flow cytometry. Results: Expression of ATM kinase and Chk2 was similar among the control, CpG, X-ray, and CpG+X-ray groups. Phosphorylated ATM kinase and Chk2 were significantly increased in the CpG+X-ray group compared with in the X-ray group (t=6.00, P<0.01 and t=3.13, P<0.05, respectively, though these were hardly detected in the control and CpG groups. However, expression of ATM kinase and Chk2 was clearly downregulated in the ATM-siRNA and Chk2-siRNA groups, respectively. Similarly, their phosphorylation levels were also significantly decreased in the ATM-siRNA group (t=14.35, P<0.01 and t=8.46, P<0.01, respectively and a significant decrease in phosphorylated Chk2 was observed in the Chk2-siRNA group (t=7.28, P<0.01 when compared with the CpG+X-ray group. Further, the number of A549 cells at Gap 2/mitotic phase and the apoptosis

  9. ‘The octet’: eight protein kinases that control mammalian DNA replication

    Directory of Open Access Journals (Sweden)

    Melvin L. Depamphilis

    2012-09-01

    Full Text Available Development of a fertilized human egg into an average sized adult requires about 29 trillion cell divisions, thereby producing enough DNA to stretch to the Sun and back 200 times (DePamphilis and Bell, 2011! Even more amazing is the fact that throughout these mitotic cell cycles, the human genome is duplicated once and only once each time a cell divides. If a cell accidentally begins to re-replicate its nuclear DNA prior to cell division, checkpoint pathways trigger apoptosis. And yet, some cells are developmentally programmed to respond to environmental cues by switching from mitotic cell cycles to endocycles, a process in which multiple S phases occur in the absence of either mitosis or cytokinesis. Endocycles allow production of viable, differentiated, polyploid cells that no longer proliferate. What is surprising is that among the 516 (Manning et al., 2002 to 557 (BioMart web site protein kinases encoded by the human genome, only eight regulate nuclear DNA replication directly. These are Cdk1, Cdk2, Cdk4, Cdk6, Cdk7, Cdc7, Chk1 and Chk2. Even more remarkable is the fact that only four of these enzymes (Cdk1, Cdk7, Cdc7 and Chk1 are essential for mammalian development. Here we describe how these protein kinases determine when DNA replication occurs during mitotic cell cycles, how mammalian cells switch from mitotic cell cycles to endocycles, and how cancer cells can be selectively targeted for destruction by inducing them to begin a second S phase before mitosis is complete.

  10. Phosphopeptide binding by Sld3 links Dbf4-dependent kinase to MCM replicative helicase activation.

    Science.gov (United States)

    Deegan, Tom D; Yeeles, Joseph Tp; Diffley, John Fx

    2016-05-01

    The initiation of eukaryotic DNA replication requires the assembly of active CMG (Cdc45-MCM-GINS) helicases at replication origins by a set of conserved and essential firing factors. This process is controlled during the cell cycle by cyclin-dependent kinase (CDK) and Dbf4-dependent kinase (DDK), and in response to DNA damage by the checkpoint kinase Rad53/Chk1. Here we show that Sld3, previously shown to be an essential CDK and Rad53 substrate, is recruited to the inactive MCM double hexamer in a DDK-dependent manner. Sld3 binds specifically to DDK-phosphorylated peptides from two MCM subunits (Mcm4, 6) and then recruits Cdc45. MCM mutants that cannot bind Sld3 or Sld3 mutants that cannot bind phospho-MCM or Cdc45 do not support replication. Moreover, phosphomimicking mutants in Mcm4 and Mcm6 bind Sld3 without DDK and facilitate DDK-independent replication. Thus, Sld3 is an essential "reader" of DDK phosphorylation, integrating signals from three distinct protein kinase pathways to coordinate DNA replication during S phase. PMID:26912723

  11. DNA damage response and spindle assembly checkpoint function throughout the cell cycle to ensure genomic integrity.

    Directory of Open Access Journals (Sweden)

    Katherine S Lawrence

    2015-04-01

    Full Text Available Errors in replication or segregation lead to DNA damage, mutations, and aneuploidies. Consequently, cells monitor these events and delay progression through the cell cycle so repair precedes division. The DNA damage response (DDR, which monitors DNA integrity, and the spindle assembly checkpoint (SAC, which responds to defects in spindle attachment/tension during metaphase of mitosis and meiosis, are critical for preventing genome instability. Here we show that the DDR and SAC function together throughout the cell cycle to ensure genome integrity in C. elegans germ cells. Metaphase defects result in enrichment of SAC and DDR components to chromatin, and both SAC and DDR are required for metaphase delays. During persistent metaphase arrest following establishment of bi-oriented chromosomes, stability of the metaphase plate is compromised in the absence of DDR kinases ATR or CHK1 or SAC components, MAD1/MAD2, suggesting SAC functions in metaphase beyond its interactions with APC activator CDC20. In response to DNA damage, MAD2 and the histone variant CENPA become enriched at the nuclear periphery in a DDR-dependent manner. Further, depletion of either MAD1 or CENPA results in loss of peripherally associated damaged DNA. In contrast to a SAC-insensitive CDC20 mutant, germ cells deficient for SAC or CENPA cannot efficiently repair DNA damage, suggesting that SAC mediates DNA repair through CENPA interactions with the nuclear periphery. We also show that replication perturbations result in relocalization of MAD1/MAD2 in human cells, suggesting that the role of SAC in DNA repair is conserved.

  12. A Monitor for Bud Emergence in the Yeast Morphogenesis Checkpoint

    OpenAIRE

    Theesfeld, Chandra L.; Zyla, Trevin R.; Bardes, Elaine G.S.; Lew, Daniel J.

    2003-01-01

    Cell cycle transitions are subject to regulation by both external signals and internal checkpoints that monitor satisfactory progression of key cell cycle events. In budding yeast, the morphogenesis checkpoint arrests the cell cycle in response to perturbations that affect the actin cytoskeleton and bud formation. Herein, we identify a step in this checkpoint pathway that seems to be directly responsive to bud emergence. Activation of the kinase Hsl1p is dependent upon...

  13. Signaling from Mus81-Eme2-Dependent DNA Damage Elicited by Chk1 Deficiency Modulates Replication Fork Speed and Origin Usage

    Directory of Open Access Journals (Sweden)

    Hervé Técher

    2016-02-01

    Full Text Available Mammalian cells deficient in ATR or Chk1 display moderate replication fork slowing and increased initiation density, but the underlying mechanisms have remained unclear. We show that exogenous deoxyribonucleosides suppress both replication phenotypes in Chk1-deficient, but not ATR-deficient, cells. Thus, in the absence of exogenous stress, depletion of either protein impacts the replication dynamics through different mechanisms. In addition, Chk1 deficiency, but not ATR deficiency, triggers nuclease-dependent DNA damage. Avoiding damage formation through invalidation of Mus81-Eme2 and Mre11, or preventing damage signaling by turning off the ATM pathway, suppresses the replication phenotypes of Chk1-deficient cells. Damage and resulting DDR activation are therefore the cause, not the consequence, of replication dynamics modulation in these cells. Together, we identify moderate reduction of precursors available for replication as an additional outcome of DDR activation. We propose that resulting fork slowing, and subsequent firing of backup origins, helps replication to proceed along damaged templates.

  14. Activation of repair and checkpoints by double-strand breaks of DNA. Activational cascade of protein phosphorylation

    International Nuclear Information System (INIS)

    Molecular mechanisms of double-strand breaks repair and checkpoints include phosphorylations of repair and checkpoint-proteins by protein kinases. Chemical modification of proteins has different consequences including activation, changing of affinity to proteins and localization

  15. Differential activation of intra-S-phase checkpoint in response to tripchlorolide and its effects on DNA replication

    Institute of Scientific and Technical Information of China (English)

    Yan REN; Jia Rui WU

    2004-01-01

    DNA replication is tightly regulated during the S phase of the cell cycle, and the activation of the intra-S-phase checkpoint due to DNA damage usually results in arrest of DNA synthesis. However, the molecular details about the correlation between the checkpoint and regulation of DNA replication are still unclear. To investigate the connections between DNA replication and DNA damage checkpoint, a DNA-damage reagent, tripchlorolide, was applied to CHO (Chinese ovary hamster) cells at early- or middle-stages of the S phase. The early-S-phase treatment with TC significantly delayed the progression of the S phase and caused the phosphorylation of the Chk1 checkpoint protein, whereas the middle-S-phase treatment only slightly slowed down the progression of the S phase. Furthermore, the analysis of DNA replication patterns revealed that replication pattern Ⅱ was greatly prolonged in the cells treated with the drug during the early-S phase, whereas the late-replication patterns of these cells were hardly detected, suggesting that the activation of the intra-S-phase checkpoint inhibits the late-origin firing of DNA replication. We conclude that cells at different stages of the S phase are differentially sensitive to the DNA-damage reagent, and the activation of the intra-Sphase checkpoint blocks the DNA replication progression in the late stage of S phase.

  16. Sensitization of human cancer cells to gemcitabine by the Chk1 inhibitor MK-8776: cell cycle perturbation and impact of administration schedule in vitro and in vivo

    International Nuclear Information System (INIS)

    Chk1 inhibitors have emerged as promising anticancer therapeutic agents particularly when combined with antimetabolites such as gemcitabine, cytarabine or hydroxyurea. Here, we address the importance of appropriate drug scheduling when gemcitabine is combined with the Chk1 inhibitor MK-8776, and the mechanisms involved in the schedule dependence. Growth inhibition induced by gemcitabine plus MK-8776 was assessed across multiple cancer cell lines. Experiments used clinically relevant “bolus” administration of both drugs rather than continuous drug exposures. We assessed the effect of different treatment schedules on cell cycle perturbation and tumor cell growth in vitro and in xenograft tumor models. MK-8776 induced an average 7-fold sensitization to gemcitabine in 16 cancer cell lines. The time of MK-8776 administration significantly affected the response of tumor cells to gemcitabine. Although gemcitabine induced rapid cell cycle arrest, the stalled replication forks were not initially dependent on Chk1 for stability. By 18 h, RAD51 was loaded onto DNA indicative of homologous recombination. Inhibition of Chk1 at 18 h rapidly dissociated RAD51 leading to the collapse of replication forks and cell death. Addition of MK-8776 from 18–24 h after a 6-h incubation with gemcitabine induced much greater sensitization than if the two drugs were incubated concurrently for 6 h. The ability of this short incubation with MK-8776 to sensitize cells is critical because of the short half-life of MK-8776 in patients’ plasma. Cell cycle perturbation was also assessed in human pancreas tumor xenografts in mice. There was a dramatic accumulation of cells in S/G2 phase 18 h after gemcitabine administration, but cells had started to recover by 42 h. Administration of MK-8776 18 h after gemcitabine caused significantly delayed tumor growth compared to either drug alone, or when the two drugs were administered with only a 30 min interval. There are two reasons why delayed

  17. Activation of the nimA protein kinase plays a unique role during mitosis that cannot be bypassed by absence of the bimE checkpoint.

    OpenAIRE

    Osmani, A H; O'Donnell, K; Pu, R T; Osmani, S A

    1991-01-01

    Mutation of nimA reversibly arrests cells in late G2 and nimA overexpression promotes premature mitosis. Here we demonstrate that the product of nimA (designated NIMA) has protein kinase activity that can phosphorylate beta-casein but not histone proteins. NIMA kinase activity is cell cycle regulated being 20-fold higher at mitosis when compared to S-phase arrested cells. NIMA activation is normally required in G2 to initiate chromosome condensation, to nucleate spindle pole body microtubules...

  18. Cellular Inhibition of Checkpoint Kinase 2 (Chk2) and Potentiation of Camptothecins and Radiation by the Novel Chk2 Inhibitor PV1019 [7-Nitro-1H-indole-2-carboxylic acid {4-[1-(guanidinohydrazone)-ethyl]-phenyl}-amide

    Energy Technology Data Exchange (ETDEWEB)

    Jobson, Andrew G.; Lountos, George T.; Lorenzi, Philip L.; Llamas, Jenny; Connelly, John; Cerna, David; Tropea, Joseph E.; Onda, Akikazu; Zoppoli, Gabriele; Kondapaka, Sudhir; Zhang, Guangtao; Caplen, Natasha J.; Cardellina, II, John H.; Yoo, Stephen S.; Monks, Anne; Self, Christopher; Waugh, David S.; Shoemaker, Robert H.; Pommier, Yves; (NIH)

    2010-04-05

    Chk2 is a checkpoint kinase involved in the ataxia telangiectasia mutated pathway, which is activated by genomic instability and DNA damage, leading to either cell death (apoptosis) or cell cycle arrest. Chk2 provides an unexplored therapeutic target against cancer cells. We recently reported 4,4'-diacetyldiphenylurea-bis(guanylhydrazone) (NSC 109555) as a novel chemotype Chk2 inhibitor. We have now synthesized a derivative of NSC 109555, PV1019 (NSC 744039) [7-nitro-1H-indole-2-carboxylic acid {l_brace}4-[1-(guanidinohydrazone)-ethyl]-phenyl{r_brace}-amide], which is a selective submicromolar inhibitor of Chk2 in vitro. The cocrystal structure of PV1019 bound in the ATP binding pocket of Chk2 confirmed enzymatic/biochemical observations that PV1019 acts as a competitive inhibitor of Chk2 with respect to ATP. PV1019 was found to inhibit Chk2 in cells. It inhibits Chk2 autophosphorylation (which represents the cellular kinase activation of Chk2), Cdc25C phosphorylation, and HDMX degradation in response to DNA damage. PV1019 also protects normal mouse thymocytes against ionizing radiation-induced apoptosis, and it shows synergistic antiproliferative activity with topotecan, camptothecin, and radiation in human tumor cell lines. We also show that PV1019 and Chk2 small interfering RNAs can exert antiproliferative activity themselves in the cancer cells with high Chk2 expression in the NCI-60 screen. These data indicate that PV1019 is a potent and selective inhibitor of Chk2 with chemotherapeutic and radiosensitization potential.

  19. Circumvention of Mcl-1-dependent drug resistance by simultaneous Chk1 and MEK1/2 inhibition in human multiple myeloma cells.

    Directory of Open Access Journals (Sweden)

    Xin-Yan Pei

    Full Text Available The anti-apoptotic protein Mcl-1 plays a major role in multiple myeloma (MM cell survival as well as bortezomib- and microenvironmental forms of drug resistance in this disease. Consequently, there is a critical need for strategies capable of targeting Mcl-1-dependent drug resistance in MM. The present results indicate that a regimen combining Chk1 with MEK1/2 inhibitors effectively kills cells displaying multiple forms of drug resistance stemming from Mcl-1 up-regulation in association with direct transcriptional Mcl-1 down-regulation and indirect disabling of Mcl-1 anti-apoptotic function through Bim up-regulation and increased Bim/Mcl-1 binding. These actions release Bak from Mcl-1, accompanied by Bak/Bax activation. Analogous events were observed in both drug-naïve and acquired bortezomib-resistant MM cells displaying increased Mcl-1 but diminished Bim expression, or cells ectopically expressing Mcl-1. Moreover, concomitant Chk1 and MEK1/2 inhibition blocked Mcl-1 up-regulation induced by IL-6/IGF-1 or co-culture with stromal cells, effectively overcoming microenvironment-related drug resistance. Finally, this regimen down-regulated Mcl-1 and robustly killed primary CD138+ MM cells, but not normal hematopoietic cells. Together, these findings provide novel evidence that this targeted combination strategy could be effective in the setting of multiple forms of Mcl-1-related drug resistance in MM.

  20. The Dynamics of the Unreplicated DNA Checkpoint in Xenopus laevis Embryos and Extracts.

    OpenAIRE

    Adjerid, Nassiba

    2008-01-01

    When unreplicated or damaged DNA is present, cell cycle checkpoint pathways cause cell cycle arrest by inhibiting cyclin-dependent kinases (Cdks). In Xenopus laevis, early embryonic development consists of twelve rapid cleavage cycles between DNA replication (S) and mitosis (M) without checkpoints or gap phases. However, checkpoints are engaged in Xenopus once the embryo reaches the midblastula transition (MBT). At this point, the embryo initiates transcription, acquires gap phases between S...

  1. Checkpoint control and cancer

    Czech Academy of Sciences Publication Activity Database

    Medema, R.H.; Macůrek, Libor

    2012-01-01

    Roč. 31, č. 21 (2012), s. 2601-2613. ISSN 0950-9232 R&D Projects: GA ČR GAP301/10/1525; GA ČR GPP305/10/P420 Institutional support: RVO:68378050 Keywords : DNA damage * checkpoint control * anticancer strategies Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 7.357, year: 2012

  2. Proteasome activity is important for replication recovery, CHK1 phosphorylation and prevention of G2 arrest after low-dose formaldehyde

    International Nuclear Information System (INIS)

    Formaldehyde (FA) is a human carcinogen with numerous sources of environmental and occupational exposures. This reactive aldehyde is also produced endogenously during metabolism of drugs and other processes. DNA–protein crosslinks (DPCs) are considered to be the main genotoxic lesions for FA. Accumulating evidence suggests that DPC repair in high eukaryotes involves proteolysis of crosslinked proteins. Here, we examined a role of the main cellular proteolytic machinery proteasomes in toxic responses of human lung cells to low FA doses. We found that transient inhibition of proteasome activity increased cytotoxicity and diminished clonogenic viability of FA-treated cells. Proteasome inactivation exacerbated suppressive effects of FA on DNA replication and increased the levels of the genotoxic stress marker γ-H2AX in normal human cells. A transient loss of proteasome activity in FA-exposed cells also caused delayed perturbations of cell cycle, which included G2 arrest and a depletion of S-phase populations at FA doses that had no effects in control cells. Proteasome activity diminished p53-Ser15 phosphorylation but was important for FA-induced CHK1 phosphorylation, which is a biochemical marker of DPC proteolysis in replicating cells. Unlike FA, proteasome inhibition had no effect on cell survival and CHK1 phosphorylation by the non-DPC replication stressor hydroxyurea. Overall, we obtained evidence for the importance of proteasomes in protection of human cells against biologically relevant doses of FA. Biochemically, our findings indicate the involvement of proteasomes in proteolytic repair of DPC, which removes replication blockage by these highly bulky lesions. - Highlights: • Proteasome inhibition enhances cytotoxicity of low-dose FA in human lung cells. • Active proteasomes diminish replication-inhibiting effects of FA. • Proteasome activity prevents delayed G2 arrest in FA-treated cells. • Proteasome inhibition exacerbates replication stress by FA in

  3. Proteasome activity is important for replication recovery, CHK1 phosphorylation and prevention of G2 arrest after low-dose formaldehyde

    Energy Technology Data Exchange (ETDEWEB)

    Ortega-Atienza, Sara; Green, Samantha E.; Zhitkovich, Anatoly, E-mail: anatoly_zhitkovich@brown.edu

    2015-07-15

    Formaldehyde (FA) is a human carcinogen with numerous sources of environmental and occupational exposures. This reactive aldehyde is also produced endogenously during metabolism of drugs and other processes. DNA–protein crosslinks (DPCs) are considered to be the main genotoxic lesions for FA. Accumulating evidence suggests that DPC repair in high eukaryotes involves proteolysis of crosslinked proteins. Here, we examined a role of the main cellular proteolytic machinery proteasomes in toxic responses of human lung cells to low FA doses. We found that transient inhibition of proteasome activity increased cytotoxicity and diminished clonogenic viability of FA-treated cells. Proteasome inactivation exacerbated suppressive effects of FA on DNA replication and increased the levels of the genotoxic stress marker γ-H2AX in normal human cells. A transient loss of proteasome activity in FA-exposed cells also caused delayed perturbations of cell cycle, which included G2 arrest and a depletion of S-phase populations at FA doses that had no effects in control cells. Proteasome activity diminished p53-Ser15 phosphorylation but was important for FA-induced CHK1 phosphorylation, which is a biochemical marker of DPC proteolysis in replicating cells. Unlike FA, proteasome inhibition had no effect on cell survival and CHK1 phosphorylation by the non-DPC replication stressor hydroxyurea. Overall, we obtained evidence for the importance of proteasomes in protection of human cells against biologically relevant doses of FA. Biochemically, our findings indicate the involvement of proteasomes in proteolytic repair of DPC, which removes replication blockage by these highly bulky lesions. - Highlights: • Proteasome inhibition enhances cytotoxicity of low-dose FA in human lung cells. • Active proteasomes diminish replication-inhibiting effects of FA. • Proteasome activity prevents delayed G2 arrest in FA-treated cells. • Proteasome inhibition exacerbates replication stress by FA in

  4. Cellular response to low dose radiation: Role of phosphatidylinositol-3 kinase like kinases

    Energy Technology Data Exchange (ETDEWEB)

    Balajee, A.S.; Meador, J.A.; Su, Y.

    2011-03-24

    It is increasingly realized that human exposure either to an acute low dose or multiple chronic low doses of low LET radiation has the potential to cause different types of cancer. Therefore, the central theme of research for DOE and NASA is focused on understanding the molecular mechanisms and pathways responsible for the cellular response to low dose radiation which would not only improve the accuracy of estimating health risks but also help in the development of predictive assays for low dose radiation risks associated with tissue degeneration and cancer. The working hypothesis for this proposal is that the cellular mechanisms in terms of DNA damage signaling, repair and cell cycle checkpoint regulation are different for low and high doses of low LET radiation and that the mode of action of phosphatidylinositol-3 kinase like kinases (PIKK: ATM, ATR and DNA-PK) determines the dose dependent cellular responses. The hypothesis will be tested at two levels: (I) Evaluation of the role of ATM, ATR and DNA-PK in cellular response to low and high doses of low LET radiation in simple in vitro human cell systems and (II) Determination of radiation responses in complex cell microenvironments such as human EpiDerm tissue constructs. Cellular responses to low and high doses of low LET radiation will be assessed from the view points of DNA damage signaling, DNA double strand break repair and cell cycle checkpoint regulation by analyzing the activities (i.e. post-translational modifications and kinetics of protein-protein interactions) of the key target proteins for PI-3 kinase like kinases both at the intra-cellular and molecular levels. The proteins chosen for this proposal are placed under three categories: (I) sensors/initiators include ATM ser1981, ATR, 53BP1, gamma-H2AX, MDC1, MRE11, Rad50 and Nbs1; (II) signal transducers include Chk1, Chk2, FANCD2 and SMC1; and (III) effectors include p53, CDC25A and CDC25C. The primary goal of this proposal is to elucidate the

  5. Targeting sphingosine kinase 1 in carcinoma cells decreases proliferation and survival by compromising PKC activity and cytokinesis.

    Directory of Open Access Journals (Sweden)

    Nataliya Kotelevets

    Full Text Available Sphingosine kinases (SK catalyze the phosphorylation of proapoptotic sphingosine to the prosurvival factor sphingosine 1-phosphate (S1P, thereby promoting oncogenic processes. Breast (MDA-MB-231, lung (NCI-H358, and colon (HCT 116 carcinoma cells were transduced with shRNA to downregulate SK-1 expression or treated with a pharmacologic SK-1 inhibitor. The effects of SK-1 targeting were investigated by measuring the level of intracellular sphingosine, the activity of protein kinase C (PKC and cell cycle regulators, and the mitotic index. Functional assays included measurement of cell proliferation, colony formation, apoptosis, and cell cycle analysis. Downregulation of SK-1 or its pharmacologic inhibition increased intracellular sphingosine and decreased PKC activity as shown by reduced phosphorylation of PKC substrates. In MDA-MB-231 cells this effect was most pronounced and reduced cell proliferation and colony formation, which could be mimicked using exogenous sphingosine or the PKC inhibitor RO 31-8220. SK-1 downregulation in MDA-MB-231 cells increased the number of cells with 4N and 8N DNA content, and similar effects were observed upon treatment with sphingosine or inhibitors of SK-1 or PKC. Examination of cell cycle regulators unveiled decreased cdc2 activity and expression of Chk1, which may compromise spindle checkpoint function and cytokinesis. Indeed, SK-1 kd cells entered mitosis but failed to divide, and in the presence of taxol also failed to sustain mitotic arrest, resulting in further increased endoreduplication and apoptosis. Our findings delineate an intriguing link between SK-1, PKC and components of the cell cycle machinery, which underlines the significance of SK-1 as a target for cancer therapy.

  6. Mangrove dolabrane-type of diterpenes tagalsins suppresses tumor growth via ROS-mediated apoptosis and ATM/ATR-Chk1/Chk2-regulated cell cycle arrest.

    Science.gov (United States)

    Neumann, Jennifer; Yang, Yi; Köhler, Rebecca; Giaisi, Marco; Witzens-Harig, Mathias; Liu, Dong; Krammer, Peter H; Lin, Wenhan; Li-Weber, Min

    2015-12-01

    Natural compounds are an important source for drug development. With an increasing cancer rate worldwide there is an urgent quest for new anti-cancer drugs. In this study, we show that a group of dolabrane-type of diterpenes, collectively named tagalsins, isolated from the Chinese mangrove genus Ceriops has potent cytotoxicity on a panel of hematologic cancer cells. Investigation of the molecular mechanisms by which tagalsins kill malignant cells revealed that it induces a ROS-mediated damage of DNA. This event leads to apoptosis induction and blockage of cell cycle progression at S-G2 phase via activation of the ATM/ATR-Chk1/Chk2 check point pathway. We further show that tagalsins suppress growth of human T-cell leukemia xenografts in vivo. Tagalsins show only minor toxicity on healthy cells and are well tolerated by mice. Our study shows a therapeutic potential of tagalsins for the treatment of hematologic malignancies and a new source of anticancer drugs. PMID:26061604

  7. Checkpoint inhibition in meningiomas.

    Science.gov (United States)

    Bi, Wenya Linda; Wu, Winona W; Santagata, Sandro; Reardon, David A; Dunn, Ian F

    2016-06-01

    Meningiomas are increasingly appreciated to share similar features with other intra-axial central nervous system neoplasms as well as systemic cancers. Immune checkpoint inhibition has emerged as a promising therapy in a number of cancers, with durable responses of years in a subset of patients. Several lines of evidence support a role for immune-based therapeutic strategies in the management of meningiomas, especially high-grade subtypes. Meningiomas frequently originate juxtaposed to venous sinuses, where an anatomic conduit for lymphatic drainage resides. Multiple populations of immune cells have been observed in meningiomas. PD-1/PD-L1 mediated immunosuppression has been implicated in high-grade meningiomas, with association between PD-L1 expression with negative prognostic outcome. These data point to the promise of future combinatorial therapeutic strategies in meningioma. PMID:27197540

  8. The checkpoint Saccharomyces cerevisiae Rad9 protein contains a tandem tudor domain that recognizes DNA.

    OpenAIRE

    Lancelot, Nathalie; Charier, Gaëlle; Couprie, Joël; Duband-Goulet, Isabelle; Alpha-Bazin, Béatrice; Quémeneur, Eric; Ma, Emilie; Marsolier-Kergoat, Marie-Claude; Ropars, Virginie; Charbonnier, Jean-Baptiste; Miron, Simona; Craescu, Constantin,; Callebaut, Isabelle; Gilquin, Bernard; Zinn-Justin, Sophie

    2007-01-01

    DNA damage checkpoints are signal transduction pathways that are activated after genotoxic insults to protect genomic integrity. At the site of DNA damage, 'mediator' proteins are in charge of recruiting 'signal transducers' to molecules 'sensing' the damage. Budding yeast Rad9, fission yeast Crb2 and metazoan 53BP1 are presented as mediators involved in the activation of checkpoint kinases. Here we show that, despite low sequence conservation, Rad9 exhibits a tandem tudor domain structurally...

  9. The DNA damage and the DNA replication checkpoints converge at the MBF transcription factor

    OpenAIRE

    Ivanova, Tsvetomira Georgieva, 1978-; Alves-Rodrigues, Isabel; G??mez Escoda, Blanca; Dutta, Chaitali; DeCaprio, James A.; Rhind, Nick; Hidalgo Hernando, Elena; Ayt?? del Olmo, Jos??

    2013-01-01

    In fission yeast cells, Cds1 is the effector kinase of the DNA replication checkpoint. We previously showed that when the DNA replication checkpoint is activated, the repressor Yox1 is phosphorylated and inactivated by Cds1, resulting in activation of MluI-binding factor (MBF)-dependent transcription. This is essential to reinitiate DNA synthesis and for correct G1-to-S transition. Here we show that Cdc10, which is an essential part of the MBF core, is the target of the DNA damage checkpoint....

  10. Toward an Optimal Online Checkpoint Solution under a Two-Level HPC Checkpoint Model

    OpenAIRE

    Di, Sheng; Robert, Yves; Vivien, Frédéric; Cappello, Franck

    2016-01-01

    The traditional single-level checkpointing method suffers from significantoverhead on large-scale platforms. Hence, multilevel checkpointing protocols have been studied extensively in recent years. The multilevel checkpoint approach allows different levels of checkpoints to be set (each with different checkpoint overheads and recovery abilities), in order to further improve the fault tolerance performance of extreme-scale HPC applications. How to optimize the checkpoint intervals for each lev...

  11. HCLK2 is required for activity of the DNA damage response kinase ATR

    DEFF Research Database (Denmark)

    Rendtlew Danielsen, Jannie M; Larsen, Dorthe Helena; Schou, Kenneth Bødtker;

    2008-01-01

    ATR is a protein kinase that orchestrates the cellular response to replication problems and DNA damage. HCLK2 has previously been reported to stabilize ATR and Chk1. Here we provide evidence that human HCLK2 acts at an early step in the ATR signaling pathway and contributes to full-scale activation...... of ATR kinase activity. We show that HCLK2 forms a complex with ATR-ATRIP and the ATR activator TopBP1. We demonstrate that HCLK2-induced ATR kinase activity toward substrates requires TopBP1 and vice versa and provides evidence that HCLK2 facilitates efficient ATR-TopBP1 association. Consistent with...

  12. Efficient Incremental Checkpointing of Java Programs

    DEFF Research Database (Denmark)

    Lawall, Julia Laetitia; Muller, Gilles

    2000-01-01

    This paper investigates the optimization of language-level checkpointing of Java programs. First, we describe how to systematically associate incremental checkpoints with Java classes. While being safe, the genericness of this solution induces substantial execution overhead. Second, to solve...

  13. Msc1 Acts Through Histone H2A.Z to Promote Chromosome Stability in Schizosaccharomyces pombe

    OpenAIRE

    Ahmed, Shakil; Dul, Barbara; Qiu, Xinxing; Walworth, Nancy C.

    2007-01-01

    As a central component of the DNA damage checkpoint pathway, the conserved protein kinase Chk1 mediates cell cycle progression when DNA damage is generated. Msc1 was identified as a multicopy suppressor capable of facilitating survival in response to DNA damage of cells mutant for chk1. We demonstrate that loss of msc1 function results in an increased rate of chromosome loss and that an msc1 null allele exhibits genetic interactions with mutants in key kinetochore components. Multicopy expres...

  14. Human cytomegalovirus inhibits a DNA damage response by mislocalizing checkpoint proteins

    Science.gov (United States)

    Gaspar, Miguel; Shenk, Thomas

    2006-02-01

    The DNA damage checkpoint pathway responds to DNA damage and induces a cell cycle arrest to allow time for DNA repair. Several viruses are known to activate or modulate this cellular response. Here we show that the ataxia-telangiectasia mutated checkpoint pathway, which responds to double-strand breaks in DNA, is activated in response to human cytomegalovirus DNA replication. However, this activation does not propagate through the pathway; it is blocked at the level of the effector kinase, checkpoint kinase 2 (Chk2). Late after infection, several checkpoint proteins, including ataxia-telangiectasia mutated and Chk2, are mislocalized to a cytoplasmic virus assembly zone, where they are colocalized with virion structural proteins. This colocalization was confirmed by immunoprecipitation of virion proteins with an antibody that recognizes Chk2. Virus replication was resistant to ionizing radiation, which causes double-strand breaks in DNA. We propose that human CMV DNA replication activates the checkpoint response to DNA double-strand breaks, and the virus responds by altering the localization of checkpoint proteins to the cytoplasm and thereby inhibiting the signaling pathway. ionizing radiation | ataxia-telangiectasia mutated pathway

  15. Cambridge checkpoint English workbook 1

    CERN Document Server

    Reynolds, John

    2013-01-01

    This Workbook supports our bestselling Checkpoint English series, with exercises specifically matched to the Cambridge Progression tests and the Checkpoint English tests. - Offers plenty of additional questions for use in class or as homework. - Includes clearly identified questions on grammar and punctuation, comprehension, use of language and essay planning. - Follows the structure of the relevant textbook to ensure a thorough understanding of all aspects of the course. - Provides a space for Students to write their answers. This Workbook is matched to the Cambridge Secondary 1 Curriculum Fr

  16. Network support for system initiated checkpoints

    Science.gov (United States)

    Chen, Dong; Heidelberger, Philip

    2013-01-29

    A system, method and computer program product for supporting system initiated checkpoints in parallel computing systems. The system and method generates selective control signals to perform checkpointing of system related data in presence of messaging activity associated with a user application running at the node. The checkpointing is initiated by the system such that checkpoint data of a plurality of network nodes may be obtained even in the presence of user applications running on highly parallel computers that include ongoing user messaging activity.

  17. Synthetic Physical Interactions Map Kinetochore-Checkpoint Activation Regions.

    Science.gov (United States)

    Ólafsson, Guðjón; Thorpe, Peter H

    2016-01-01

    The spindle assembly checkpoint (SAC) is a key mechanism to regulate the timing of mitosis and ensure that chromosomes are correctly segregated to daughter cells. The recruitment of the Mad1 and Mad2 proteins to the kinetochore is normally necessary for SAC activation. This recruitment is coordinated by the SAC kinase Mps1, which phosphorylates residues at the kinetochore to facilitate binding of Bub1, Bub3, Mad1, and Mad2. There is evidence that the essential function of Mps1 is to direct recruitment of Mad1/2. To test this model, we have systematically recruited Mad1, Mad2, and Mps1 to most proteins in the yeast kinetochore, and find that, while Mps1 is sufficient for checkpoint activation, recruitment of either Mad1 or Mad2 is not. These data indicate an important role for Mps1 phosphorylation in SAC activation, beyond the direct recruitment of Mad1 and Mad2. PMID:27280788

  18. Checkpointing for a hybrid computing node

    Science.gov (United States)

    Cher, Chen-Yong

    2016-03-08

    According to an aspect, a method for checkpointing in a hybrid computing node includes executing a task in a processing accelerator of the hybrid computing node. A checkpoint is created in a local memory of the processing accelerator. The checkpoint includes state data to restart execution of the task in the processing accelerator upon a restart operation. Execution of the task is resumed in the processing accelerator after creating the checkpoint. The state data of the checkpoint are transferred from the processing accelerator to a main processor of the hybrid computing node while the processing accelerator is executing the task.

  19. DNA damage checkpoint recovery and cancer development

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Haiyong [First affiliated hospital, Zhejiang University, School of medicine, Cancer Center, 79 Qingchun Road, Hangzhou 310003 (China); Zhang, Xiaoshan [Department of Genetics, University of Texas M.D. Anderson Cancer Center, Department of Genetics Unit 1010, 1515 Holcombe Blvd. Houston, TX 77030 (United States); Teng, Lisong, E-mail: lsteng@zju.edu.cn [First affiliated hospital, Zhejiang University, School of medicine, Cancer Center, 79 Qingchun Road, Hangzhou 310003 (China); Legerski, Randy J., E-mail: rlegersk@mdanderson.org [Department of Genetics, University of Texas M.D. Anderson Cancer Center, Department of Genetics Unit 1010, 1515 Holcombe Blvd. Houston, TX 77030 (United States)

    2015-06-10

    Cell cycle checkpoints were initially presumed to function as a regulator of cell cycle machinery in response to different genotoxic stresses, and later found to play an important role in the process of tumorigenesis by acting as a guard against DNA over-replication. As a counterpart of checkpoint activation, the checkpoint recovery machinery is working in opposition, aiming to reverse the checkpoint activation and resume the normal cell cycle. The DNA damage response (DDR) and oncogene induced senescence (OIS) are frequently found in precancerous lesions, and believed to constitute a barrier to tumorigenesis, however, the DDR and OIS have been observed to be diminished in advanced cancers of most tissue origins. These findings suggest that when progressing from pre-neoplastic lesions to cancer, DNA damage checkpoint barriers are overridden. How the DDR checkpoint is bypassed in this process remains largely unknown. Activated cytokine and growth factor-signaling pathways were very recently shown to suppress the DDR and to promote uncontrolled cell proliferation in the context of oncovirus infection. In recent decades, data from cell line and tumor models showed that a group of checkpoint recovery proteins function in promoting tumor progression; data from patient samples also showed overexpression of checkpoint recovery proteins in human cancer tissues and a correlation with patients' poor prognosis. In this review, the known cell cycle checkpoint recovery proteins and their roles in DNA damage checkpoint recovery are reviewed, as well as their implications in cancer development. This review also provides insight into the mechanism by which the DDR suppresses oncogene-driven tumorigenesis and tumor progression. - Highlights: • DNA damage checkpoint works as a barrier to cancer initiation. • DDR machinary response to genotoxic and oncogenic stress in similar way. • Checkpoint recovery pathways provide active signaling in cell cycle control. • Checkpoint

  20. DNA damage checkpoint recovery and cancer development

    International Nuclear Information System (INIS)

    Cell cycle checkpoints were initially presumed to function as a regulator of cell cycle machinery in response to different genotoxic stresses, and later found to play an important role in the process of tumorigenesis by acting as a guard against DNA over-replication. As a counterpart of checkpoint activation, the checkpoint recovery machinery is working in opposition, aiming to reverse the checkpoint activation and resume the normal cell cycle. The DNA damage response (DDR) and oncogene induced senescence (OIS) are frequently found in precancerous lesions, and believed to constitute a barrier to tumorigenesis, however, the DDR and OIS have been observed to be diminished in advanced cancers of most tissue origins. These findings suggest that when progressing from pre-neoplastic lesions to cancer, DNA damage checkpoint barriers are overridden. How the DDR checkpoint is bypassed in this process remains largely unknown. Activated cytokine and growth factor-signaling pathways were very recently shown to suppress the DDR and to promote uncontrolled cell proliferation in the context of oncovirus infection. In recent decades, data from cell line and tumor models showed that a group of checkpoint recovery proteins function in promoting tumor progression; data from patient samples also showed overexpression of checkpoint recovery proteins in human cancer tissues and a correlation with patients' poor prognosis. In this review, the known cell cycle checkpoint recovery proteins and their roles in DNA damage checkpoint recovery are reviewed, as well as their implications in cancer development. This review also provides insight into the mechanism by which the DDR suppresses oncogene-driven tumorigenesis and tumor progression. - Highlights: • DNA damage checkpoint works as a barrier to cancer initiation. • DDR machinary response to genotoxic and oncogenic stress in similar way. • Checkpoint recovery pathways provide active signaling in cell cycle control. • Checkpoint

  1. A Monitor for Bud Emergence in the Yeast Morphogenesis Checkpoint

    Science.gov (United States)

    Theesfeld, Chandra L.; Zyla, Trevin R.; Bardes, Elaine G.S.; Lew, Daniel J.

    2003-01-01

    Cell cycle transitions are subject to regulation by both external signals and internal checkpoints that monitor satisfactory progression of key cell cycle events. In budding yeast, the morphogenesis checkpoint arrests the cell cycle in response to perturbations that affect the actin cytoskeleton and bud formation. Herein, we identify a step in this checkpoint pathway that seems to be directly responsive to bud emergence. Activation of the kinase Hsl1p is dependent upon its recruitment to a cortical domain organized by the septins, a family of conserved filament-forming proteins. Under conditions that delayed or blocked bud emergence, Hsl1p recruitment to the septin cortex still took place, but hyperphosphorylation of Hsl1p and recruitment of the Hsl1p-binding protein Hsl7p to the septin cortex only occurred after bud emergence. At this time, the septin cortex spread to form a collar between mother and bud, and Hsl1p and Hsl7p were restricted to the bud side of the septin collar. We discuss models for translating cellular geometry (in this case, the emergence of a bud) into biochemical signals regulating cell proliferation. PMID:12925763

  2. Visualizing the spindle checkpoint in Drosophila spermatocytes

    OpenAIRE

    Rebollo, Elena; González, Cayetano

    2000-01-01

    The spindle assembly checkpoint detects defects in spindle structure or in the alignment of the chromosomes on the metaphase plate and delays the onset of anaphase until defects are corrected. Thus far, the evidence regarding the presence of a spindle checkpoint during meiosis in male Drosophila has been indirect and contradictory. On the one hand, chromosomes without pairing partners do not prevent meiosis progression. On the other hand, some conserved components of the spindle checkpoint ma...

  3. Simulated Microgravity Promotes Cell Apoptosis Through Suppressing Uev1A/TICAM/TRAF/NF-κB-Regulated Anti-Apoptosis and p53/PCNA- and ATM/ATR-Chk1/2-Controlled DNA-Damage Response Pathways.

    Science.gov (United States)

    Zhao, Tuo; Tang, Xin; Umeshappa, Channakeshava Sokke; Ma, Hong; Gao, Haijun; Deng, Yulin; Freywald, Andrew; Xiang, Jim

    2016-09-01

    Microgravity has been known to induce cell death. However, its underlying mechanism is less studied. In this study, BL6-10 melanoma cells were cultured in flasks under simulated microgravity (SMG). We examined cell apoptosis, and assessed expression of genes associated with apoptosis and genes regulating apoptosis in cells under SMG. We demonstrate that SMG induces cell morphological changes and microtubule alterations by confocal microscopy, and enhances apoptosis by flow cytometry, which was associated with up- and down-regulation of pro-apoptotic and anti-apoptotic genes, respectively. Moreover, up- and down-regulation of pro-apoptotic (Caspases 3, 7, 8) and anti-apoptotic (Bcl2 and Bnip3) molecules was confirmed by Western blotting analysis. Western blot analysis also indicates that SMG causes inhibition of an apoptosis suppressor, pNF-κB-p65, which is complemented by the predominant localization of NF-κB-p65 in the cytoplasm. SMG also reduces expression of molecules regulating the NF-κB pathway including Uev1A, TICAM, TRAF2, and TRAF6. Interestingly, 10 DNA repair genes are down-regulated in cells exposed to SMG, among which down-regulation of Parp, Ercc8, Rad23, Rad51, and Ku70 was confirmed by Western blotting analysis. In addition, we demonstrate a significant inhibition of molecules involved in the DNA-damage response, such as p53, PCNA, ATM/ATR, and Chk1/2. Taken together, our work reveals that SMG promotes the apoptotic response through a combined modulation of the Uev1A/TICAM/TRAF/NF-κB-regulated apoptosis and the p53/PCNA- and ATM/ATR-Chk1/2-controlled DNA-damage response pathways. Thus, our investigation provides novel information, which may help us to determine the cause of negative alterations in human physiology occurring at spaceflight environment. J. Cell. Biochem. 117: 2138-2148, 2016. © 2016 Wiley Periodicals, Inc. PMID:26887372

  4. GRID COMPUTING AND CHECKPOINT APPROACH

    Directory of Open Access Journals (Sweden)

    Pankaj gupta

    2011-05-01

    Full Text Available Grid computing is a means of allocating the computational power of alarge number of computers to complex difficult computation or problem. Grid computing is a distributed computing paradigm thatdiffers from traditional distributed computing in that it is aimed toward large scale systems that even span organizational boundaries. In this paper we investigate the different techniques of fault tolerance which are used in many real time distributed systems. The main focus is on types of fault occurring in the system, fault detection techniques and the recovery techniques used. A fault can occur due to link failure, resource failure or by any other reason is to be tolerated for working the system smoothly and accurately. These faults can be detected and recovered by many techniques used accordingly. An appropriate fault detector can avoid loss due to system crash and reliable fault tolerance technique can save from system failure. This paper provides how these methods are applied to detect and tolerate faults from various Real Time Distributed Systems. The advantages of utilizing the check pointing functionality are obvious; however so far the Grid community has notdeveloped a widely accepted standard that would allow the Gridenvironment to consciously utilize low level check pointing packages.Therefore, such a standard named Grid Check pointing Architecture isbeing designed. The fault tolerance mechanism used here sets the jobcheckpoints based on the resource failure rate. If resource failureoccurs, the job is restarted from its last successful state using acheckpoint file from another grid resource. A critical aspect for anautomatic recovery is the availability of checkpoint files. A strategy to increase the availability of checkpoints is replication. Grid is a form distributed computing mainly to virtualizes and utilize geographically distributed idle resources. A grid is a distributed computational and storage environment often composed of

  5. The Rho-GAP Bem2p plays a GAP-independent role in the morphogenesis checkpoint

    OpenAIRE

    Marquitz, Aron R.; Harrison, Jacob C.; Bose, Indrani; Zyla, Trevin R.; McMillan, John N.; Lew, Daniel J.

    2002-01-01

    The Saccharomyces cerevisiae morphogenesis checkpoint delays mitosis in response to insults that impair actin organization and/or bud formation. The delay is due to accumulation of the inhibitory kinase Swe1p, which phosphorylates the cyclin-dependent kinase Cdc28p. Having screened through a panel of yeast mutants with defects in cell morphogenesis, we report here that the polarity establishment protein Bem2p is required for the checkpoint response. Bem2p is a Rho-GTPase activating protein (G...

  6. Overlapped checkpointing with hardware assist

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, Christopher J [Los Alamos National Laboratory; Nunez, James A [Los Alamos National Laboratory; Wang, Jun [U. OF CENTRAL FLORIDA (UCF)

    2009-01-01

    We present a new approach to handling the demanding I/O workload incurred during checkpoint writes encountered in High Performance Computing. Prior efforts to improve performance have been primarily bound by mechanical limitations of the hard drive. Our research surpasses this limitation by providing a method to: (1) write checkpoint data to a high-speed, non-volatile buffer, and (2) asynchronously write this data to permanent storage while resuming computation. This removes the hard drive from the critical data path because our I/O node based buffers isolate the compute nodes from the storage servers. This solution is feasible because of industry declines in cost for high-capacity, non-volatile storage technologies. Testing was conducted on a small-scale cluster to prove the design, and then scaled at Los Alamos National Laboratory. Results show a definitive speedup factor for select workloads over writing directly to a typical global parallel file system; the Panasas ActiveScale File System.

  7. Visualizing the spindle checkpoint in Drosophila spermatocytes

    Science.gov (United States)

    Rebollo, Elena; González, Cayetano

    2000-01-01

    The spindle assembly checkpoint detects defects in spindle structure or in the alignment of the chromosomes on the metaphase plate and delays the onset of anaphase until defects are corrected. Thus far, the evidence regarding the presence of a spindle checkpoint during meiosis in male Drosophila has been indirect and contradictory. On the one hand, chromosomes without pairing partners do not prevent meiosis progression. On the other hand, some conserved components of the spindle checkpoint machinery are expressed in these cells and behave as their homologue proteins do in systems with an active spindle checkpoint. To establish whether the spindle checkpoint is active in Drosophila spermatocytes we have followed meiosis progression by time-lapse microscopy under conditions where the checkpoint is likely to be activated. We have found that the presence of a relatively high number of misaligned chromosomes or a severe disruption of the meiotic spindle results in a significant delay in the time of entry into anaphase. These observations provide the first direct evidence substantiating the activity of a meiotic spindle checkpoint in male Drosophila. PMID:11256627

  8. Ipl1p-dependent phosphorylation of Mad3p is required for the spindle checkpoint response to lack of tension at kinetochores

    OpenAIRE

    King, Emma M J; Rachidi, Najma; Morrice, Nick; Hardwick, Kevin G.; Stark, Michael J. R.

    2007-01-01

    The spindle checkpoint delays anaphase onset until all chromosomes are correctly attached to microtubules. Ipl1 protein kinase (Aurora B) is required to correct inappropriate kinetochore-microtubule attachments and for the response to lack of tension between sister kinetochores. Here we identify residues in the checkpoint protein Mad3p that are phosphorylated by Ipl1p. When phosphorylation of Mad3p at two sites is prevented, the cell's response to reduced kinetochore tension is dramatically c...

  9. Ipl1p-dependent phosphorylation of Mad3p is required for the spindle checkpoint response to lack of tension at kinetochores

    OpenAIRE

    King, Emma M J; Rachidi, Najma; Morrice, Nick; Hardwick, Kevin G.; Stark, Michael J. R.

    2007-01-01

    The spindle checkpoint delays anaphase onset until all chromosomes are correctly attached to microtubules. Ipl1 protein kinase (Aurora B) is required to correct inappropriate kinetochore–microtubule attachments and for the response to lack of tension between sister kinetochores. Here we identify residues in the checkpoint protein Mad3p that are phosphorylated by Ipl1p. When phosphorylation of Mad3p at two sites is prevented, the cell’s response to reduced kinetochore tension is dramatically c...

  10. REVIEW OF CHECKPOINTING ALGORITHMS IN DISTRIBUTED SYSTEMS

    Directory of Open Access Journals (Sweden)

    Poonam Gahlan

    2010-06-01

    Full Text Available Checkpointing is the process of saving the status information. Checkpoint is defined as a designated place in a program at which normal processing is interrupted specifically to preserve the status information necessary to allow resumption of processing at a later time. Mobile computing raises many new issues such as lack of stablestorage, low bandwidth of wireless channel, high mobility, and limited battery life. Coordinated checkpointing is an attractive approach for transparently adding fault tolerance to distributed applications since it avoids domino effects and minimizes the stable storage requirement. This paper presents the review of the algorithms,which have been reported in the literature for checkpointing. This paper also covers backward error recovery techniques for distributed systems specially the distributed mobile systems.

  11. Damage-induced DNA replication stalling relies on MAPK-activated protein kinase 2 activity

    DEFF Research Database (Denmark)

    Kopper, F.; Bierwirth, C.; Schon, M.;

    2013-01-01

    DNA damage can obstruct replication forks, resulting in replicative stress. By siRNA screening, we identified kinases involved in the accumulation of phosphohistone 2AX (gamma H2AX) upon UV irradiation-induced replication stress. Surprisingly, the strongest reduction of phosphohistone 2AX followed...... replication impaired by gemcitabine or by Chk1 inhibition. This rescue strictly depended on transiesion DNA polymerases. In conclusion, instead of being an unavoidable consequence of DNA damage, alterations of replication speed and origin firing depend on MK2-mediated signaling....... knockdown of the MAP kinase-activated protein kinase 2 (MK2), a kinase currently implicated in p38 stress signaling and G2 arrest. Depletion or inhibition of MK2 also protected cells from DNA damage-induced cell death, and mice deficient for MK2 displayed decreased apoptosis in the skin upon UV irradiation...

  12. A Nonblocking Coordinated Checkpointing Algorithm for Mobile Computing Systems

    Directory of Open Access Journals (Sweden)

    Rachit Garg

    2010-05-01

    Full Text Available A checkpoint algorithm for mobile computing systems needs to handle many new issues like: mobility, low bandwidth of wireless channels, lack of stable storage on mobile nodes, disconnections, limited battery power and high failure rate of mobile nodes. These issues make traditional checkpointing techniques unsuitable for such environments. Minimum-process coordinated checkpointing is an attractive approach to introduce fault tolerance in mobile distributed systems transparently. This approach is domino-free, requires at most two checkpoints of a process on stable storage, and forces only a minimum number of processes to checkpoint. But, it requires extra synchronization messages, blocking of the underlying computation or taking some useless checkpoints. In this paper, we propose a nonblocking coordinated checkpointing algorithm for mobile computing systems, which requires only a minimum number of processes to take permanent checkpoints. We reduce the message complexity as compared to the Cao-Singhal algorithm [4], while keeping the number of useless checkpoints unchanged. We also address the related issues like: failures during checkpointing, disconnections, concurrent initiations of the algorithm and maintaining exact dependencies among processes. Finally, the paper presents an optimization technique, which significantly reduces the number of useless checkpoints at the cost of minor increase in the message complexity. In coordinated checkpointing, if a single process fails to take its tentative checkpoint; all the checkpoint effort is aborted. We try to reduce this effort by taking soft checkpoints in the first phase at Mobile Hosts.

  13. The Rho-GAP Bem2p plays a GAP-independent role in the morphogenesis checkpoint

    Science.gov (United States)

    Marquitz, Aron R.; Harrison, Jacob C.; Bose, Indrani; Zyla, Trevin R.; McMillan, John N.; Lew, Daniel J.

    2002-01-01

    The Saccharomyces cerevisiae morphogenesis checkpoint delays mitosis in response to insults that impair actin organization and/or bud formation. The delay is due to accumulation of the inhibitory kinase Swe1p, which phosphorylates the cyclin-dependent kinase Cdc28p. Having screened through a panel of yeast mutants with defects in cell morphogenesis, we report here that the polarity establishment protein Bem2p is required for the checkpoint response. Bem2p is a Rho-GTPase activating protein (GAP) previously shown to act on Rho1p, and we now show that it also acts on Cdc42p, the GTPase primarily responsible for establishment of cell polarity in yeast. Whereas the morphogenesis role of Bem2p required GAP activity, the checkpoint role of Bem2p did not. Instead, this function required an N-terminal Bem2p domain. Thus, this single protein has a GAP-dependent role in promoting cell polarity and a GAP-independent role in responding to defects in cell polarity by enacting the checkpoint. Surprisingly, Swe1p accumulation occurred normally in bem2 cells, but they were nevertheless unable to promote Cdc28p phosphorylation. Therefore, Bem2p defines a novel pathway in the morphogenesis checkpoint. PMID:12145202

  14. Asynchronous Checkpoint Migration with MRNet in the Scalable Checkpoint / Restart Library

    Energy Technology Data Exchange (ETDEWEB)

    Mohror, K; Moody, A; de Supinski, B R

    2012-03-20

    Applications running on today's supercomputers tolerate failures by periodically saving their state in checkpoint files on stable storage, such as a parallel file system. Although this approach is simple, the overhead of writing the checkpoints can be prohibitive, especially for large-scale jobs. In this paper, we present initial results of an enhancement to our Scalable Checkpoint/Restart Library (SCR). We employ MRNet, a tree-based overlay network library, to transfer checkpoints from the compute nodes to the parallel file system asynchronously. This enhancement increases application efficiency by removing the need for an application to block while checkpoints are transferred to the parallel file system. We show that the integration of SCR with MRNet can reduce the time spent in I/O operations by as much as 15x. However, our experiments exposed new scalability issues with our initial implementation. We discuss the sources of the scalability problems and our plans to address them.

  15. Checkpoint triggering in a computer system

    Energy Technology Data Exchange (ETDEWEB)

    Cher, Chen-Yong

    2016-09-06

    According to an aspect, a method for triggering creation of a checkpoint in a computer system includes executing a task in a processing node of the computer system and determining whether it is time to read a monitor associated with a metric of the task. The monitor is read to determine a value of the metric based on determining that it is time to read the monitor. A threshold for triggering creation of the checkpoint is determined based on the value of the metric. Based on determining that the value of the metric has crossed the threshold, the checkpoint including state data of the task is created to enable restarting execution of the task upon a restart operation.

  16. Garbage Collection in Uncoordinated Checkpointing Algorithms

    Institute of Scientific and Technical Information of China (English)

    LIU Yunlong; CHEN Junliang

    1999-01-01

    In this paper, the hard problem of thethorough garbage collection in uncoordinated checkpointing algorithms isstudied. After introduction of the traditional garbage collectingscheme, with which only obsolete checkpoints can be discarded, it isshown that this kind of traditional method may fail to discard anycheckpoint in some special cases, and it is necessary and urgent to finda thorough garbage collecting method, with which all the checkpointsuseless for any future rollback-recovery including the obsolete ones canbe discarded. Then, the Thorough Garbage Collection Theorem is proposedand proved, which ensures the feasibility of the thorough garbagecollection, and gives the method to calculate the set of the usefulcheckpoints as well.

  17. Eavesdropping on the cytoskeleton: progress and controversy in the yeast morphogenesis checkpoint.

    Science.gov (United States)

    Keaton, Mignon A; Lew, Daniel J

    2006-12-01

    The morphogenesis checkpoint provides a link between bud formation and mitosis in yeast. In this pathway, insults affecting the actin or septin cytoskeleton trigger a cell cycle arrest, mediated by the Wee1 homolog Swe1p, which catalyzes the inhibitory phosphorylation of the mitosis-promoting cyclin-dependent kinase (CDK) on a conserved tyrosine residue. Analyses of Swe1p phosphorylation have mapped 61 sites targeted by CDKs and Polo-related kinases, which control both Swe1p activity and Swe1p degradation. Although the sites themselves are not evolutionarily conserved, the control of Swe1p degradation exhibits many conserved features, and is linked to DNA-responsive checkpoints in vertebrate cells. At the 'sensing' end of the checkpoint, recent work has begun to shed light on how septins are organized and how they impact Swe1p regulators. However, the means by which Swe1p responds to actin perturbations once a bud has formed remains controversial. PMID:17055334

  18. Checkpointing and Recovery in Distributed and Database Systems

    Science.gov (United States)

    Wu, Jiang

    2011-01-01

    A transaction-consistent global checkpoint of a database records a state of the database which reflects the effect of only completed transactions and not the results of any partially executed transactions. This thesis establishes the necessary and sufficient conditions for a checkpoint of a data item (or the checkpoints of a set of data items) to…

  19. A chemical tool box defines mitotic and interphase roles for Mps1 kinase

    OpenAIRE

    Lan, Weijie; Don W Cleveland

    2010-01-01

    In this issue, three groups (Hewitt et al. 2010. J. Cell Biol. doi:10.1083/jcb.201002133; Maciejowski et al. 2010. J. Cell Biol. doi:10.1083/jcb.201001050; Santaguida et al. 2010. J. Cell Biol. doi:10.1083/jcb.201001036) use chemical inhibitors to analyze the function of the mitotic checkpoint kinase Mps1. These studies demonstrate that Mps1 kinase activity ensures accurate chromosome segregation through its recruitment to kinetochores of mitotic checkpoint proteins, formation of interphase a...

  20. Oxidative stress-induced DNA damage of mouse zygotes triggers G2/M checkpoint and phosphorylates Cdc25 and Cdc2.

    Science.gov (United States)

    Zhang, Yuting; Qian, Diting; Li, Zhiling; Huang, Yue; Wu, Que; Ru, Gaizhen; Chen, Man; Wang, Bin

    2016-07-01

    In vitro fertilized (IVF) embryos show both cell cycle and developmental arrest. We previously showed oxidative damage activates the ATM → Chk1 → Cdc25B/Cdc25C cascade to mediate G2/M cell cycle arrest for repair of hydrogen peroxide (H2O2)-induced oxidative damage in sperm. However, the mechanisms underlying the developmental delay of zygotes are unknown. To develop a model of oxidative-damaged zygotes, we treated mouse zygotes with different concentrations of H2O2 (0, 0.01, 0.02, 0.03, 0.04, 0.05 mM), and evaluated in vitro zygote development, BrdU incorporation to detect the duration of S phase. We also examined reactive oxygen species level and used immunofluorescence to detect activation of γH2AX, Cdc2, and Cdc25. Oxidatively damaged zygotes showed a delay in G2/M phase and produced a higher level of ROS. At the same time, γH2AX was detected in oxidatively damaged zygotes as well as phospho-Cdc25B (Ser323), phospho-Cdc25C (Ser216), and phospho-Cdc2 (Tyr15). Our study indicates that oxidative stress-induced DNA damage of mouse zygotes triggers the cell cycle checkpoint, which results in G2/M cell cycle arrest, and that phospho-Cdc25B (Ser323), phospho-Cdc25C (Ser216), and phospho-Cdc2 (Tyr15) participate in activating the G2/M checkpoint. PMID:27117522

  1. Ataxia telangiectasia-mutated-Rad3-related DNA damage checkpoint signaling pathway triggered by hepatitis B virus infection

    Institute of Scientific and Technical Information of China (English)

    Fan Zhao; Qing-Jun Ma; Hui Zhong; Ning-Bo Hou; Xiao-Li Yang; Xiang He; Yu Liu; Yan-Hong Zhang; Cong-Wen Wei; Ting Song; Li Li

    2008-01-01

    AIM: To explore whether acute cellular DNA damage response is induced upon hepatitis B virus (HBV) infection and the effects of the HBV infection. METHODS: We incubated HL7702 hepatocytes with HBV-positive serum, mimicking a natural HBV infection process. We used immunoblotting to evaluate protein expression levels in HBV-infected cells or in non-infected cells; immunofluorescence to show ATR foci ands Chk1 phosphorylation loci formation; flow cytometry to analyze the cell cycle and apoptosis; ultraviolet (UV) radiation and ionizing radiation (IR)-treated cells to mimic DNA damage; and Trypan blue staining to count the viable cells.RESULTS: We found that HBV infection induced an increased steady state of ATR protein and increased phosphorylation of multiple downstream targets including Chkl, p53 and H2AX. In contrast to ATR and its target, the phosphorylated form of ATM at Ser-1981 and its downstream substrate Chk2 phosphorylation at Thr-68 did not visibly increase upon infection. However, the level of Mre11 and p21 were reduced beginning at 0.5 h after HBV-positive serum addition. Also, HBV infection led to transient cell cycle arrest in the S and the G2 phases without accompanying increased apoptosis. Research on cell survival changes upon radiation following HBV infection showed that survival of UV-treated host cells was greatly increased by HBV infection, owing to the reduced apoptosis. Meanwhile, survival of IR-treated host cells was reduced by HBV infection. CONCLUSION: HBV infection activates ATR DNA damage response to replication stress and abrogates the checkpoint signaling controlled by DNA damage response.

  2. Multiple Defects of Cell Cycle Checkpoints in U937-ASPI3K, an U937 Cell Mutant Stably Expressing Anti-Sense ATM Gene cDNA

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    (Ataxia-telangiectasia mutated gene (ATM) functions in control of cell cycle checkpoints in responding to DNA damage and protects cells from undergoing apoptosis. Knock-out within tumor cells of endogenous ATM will achieve therapeutic benefits and nable a better understanding of the decisive mechanisms of cell death or survival in response to DNA damaging agents. ) In present paper, we sought to characterize the cell cycle checkpoint profiles in U937-ASPI3K, a U937 cell mutant that was previously established with endogenous ATM knock-out phenotype. Synchronized U937-ASPI3K was exposed to 137Cs irradiation, G1, S, G2/M cell cycle checkpoint profiles were evaluated by determining cell cycle kinetics, p53/p21 protein, cyclin dependent kinase 2 (CDK2) and p34CDC2 kinase activity in response to irradiation. U937-ASPI3K exhibited multiple defects in cell cycle checkpoints as defined by failing to arrest cells upon irradiation. The accumulation of cellular p53/p21 protein and inhibition of CDK kinase was also abolished in U937-ASPI3K. It was concluded that the stable expression of anti-sense PI3K cDNA fragment completely abolished multiple cell cycle checkpoints in U937-ASPI3K, and hence U937-ASPI3K with an AT-like phenotype could serves as a valuable model system for investigating the signal transduction pathway in responding to DNA damaging-based cancer therapy.

  3. Targeting the Checkpoint to Kill Cancer Cells

    Czech Academy of Sciences Publication Activity Database

    Benada, Jan; Macůrek, Libor

    2015-01-01

    Roč. 6, č. 3 (2015), s. 1912-1937. ISSN 2218-273X R&D Projects: GA ČR(CZ) GA14-34264S Institutional support: RVO:68378050 Keywords : checkpoint * DNA damage response * cancer Subject RIV: EB - Genetics ; Molecular Biology

  4. Dpb11/TopBP1 plays distinct roles in DNA replication, checkpoint response and homologous recombination

    DEFF Research Database (Denmark)

    Germann, Susanne Manuela; Østergaard, Vibe Hallundbæk; Haas, Caroline;

    2011-01-01

    DPB11/TopBP1 is an essential evolutionarily conserved gene involved in initiation of DNA replication and checkpoint signaling. Here, we show that Saccharomyces cerevisiae Dpb11 forms nuclear foci that localize to sites of DNA damage in G1, S and G2 phase, a recruitment that is conserved for its...... and Tel1, and of the checkpoint mediator Rad9. In a site-directed mutagenesis screen, we identify a separation-of-function mutant, dpb11-PF, that is sensitive to DSB-inducing agents yet remains proficient for DNA replication and the S-phase checkpoint at the permissive temperature. The dpb11-PF mutant...... homologue TopBP1 in Gallus gallus. Damage-induced Dpb11 foci are distinct from Sld3 replication initiation foci. Further, Dpb11 foci are dependent on the checkpoint proteins Mec3 (9-1-1 complex) and Rad24, and require the C-terminal domain of Dpb11. Dpb11 foci are independent of the checkpoint kinases Mec1...

  5. Structure of a Blinkin-BUBR1 complex reveals an interaction crucial for kinetochore-mitotic checkpoint regulation via an unanticipated binding Site

    DEFF Research Database (Denmark)

    Bolanos-Garcia, Victor M; Lischetti, Tiziana; Matak-Vinković, Dijana;

    2011-01-01

    The maintenance of genomic stability relies on the spindle assembly checkpoint (SAC), which ensures accurate chromosome segregation by delaying the onset of anaphase until all chromosomes are properly bioriented and attached to the mitotic spindle. BUB1 and BUBR1 kinases are central for this proc...

  6. Replication licensing and the DNA damage checkpoint

    OpenAIRE

    Cook, Jeanette Gowen

    2009-01-01

    Accurate and timely duplication of chromosomal DNA requires that replication be coordinated with processes that ensure genome integrity. Significant advances in determining how the earliest steps in DNA replication are affected by DNA damage have highlighted some of the mechanisms to establish that coordination. Recent insights have expanded the relationship between the ATM and ATR-dependent checkpoint pathways and the proteins that bind and function at replication origins. These findings sug...

  7. Immune Checkpoint Inhibitors in Older Adults.

    Science.gov (United States)

    Elias, Rawad; Morales, Joshua; Rehman, Yasser; Khurshid, Humera

    2016-08-01

    Cancer is primarily a disease of older adults. The treatment of advanced stage tumors usually involves the use of systemic agents that may be associated with significant risk of toxicity, especially in older patients. Immune checkpoint inhibitors are newcomers to the oncology world with improved efficacy and better safety profiles when compared to traditional cytotoxic drugs. This makes them an attractive treatment option. While there are no elderly specific trials, this review attempts to look at the current available data from a geriatric oncology perspective. We reviewed data from phase III studies that led to newly approved indications of checkpoint inhibitors in non-small cell lung cancer, melanoma, and renal cell cancer. Data were reviewed with respect to response, survival, and toxicity according to three groups: 75 years. Current literature does not allow one to draw definitive conclusions regarding the role of immune checkpoint inhibitors in older adults. However, they may offer a potentially less toxic but equally efficacious treatment option for the senior adult oncology patient. PMID:27287329

  8. Biological significance of the focus on DNA damage checkpoint factors remained after irradiation of ionizing radiation

    International Nuclear Information System (INIS)

    This paper reviews recent reports on the focus formation and participation to checkpoint of (such phosphorylated (P-d) as below) ATM and H2AX, MDC1, 53BP1 and NBS1, and discusses their role in DNA damage checkpoint induction mainly around authors' studies. When the cell is irradiated by ionizing radiation, the subtype histone like H2AX is P-d and the formed focus', seen in the nucleus on immuno-fluorographic observation, represents the P-d H2AX at the damaged site of DNA. The role of P-d ATM (the product of causative gene of ataxia-telangiectasia mutation, a protein kinase) has been first shown by laser beam irradiation. Described are discussions on the roles and functions after irradiation in focus formation and DNA damage checkpoint of P-d H2AX (a specific histone product by the radiation like γ-ray as above), P-d ATM, MDC1 (a mediator of DNA damage check point protein 1), 53BP1, (a p53 binding protein) and NBS1 (the product of the causative gene of Nijmegen Breakage Syndrome). Authors have come to point out the remained focal size increase as implications of the efficient repair of damaged DNA, and the second cycled p53 accumulation, of tumor suppression. Thus evaluation of biological significance of these aspects, scarcely noted hitherto, is concluded important. (S.I.)

  9. An Anti-Checkpoint Activity for Rif1

    OpenAIRE

    Xue, Yuan; Rushton, Michael D.; Maringele, Laura

    2011-01-01

    Cells accumulate single-stranded DNA (ssDNA) when telomere capping, DNA replication, or DNA repair is impeded. This accumulation leads to cell cycle arrest through activating the DNA–damage checkpoints involved in cancer protection. Hence, ssDNA accumulation could be an anti-cancer mechanism. However, ssDNA has to accumulate above a certain threshold to activate checkpoints. What determines this checkpoint-activation threshold is an important, yet unanswered question. Here we identify Rif1 (R...

  10. Checkpoint Activation of an Unconventional DNA Replication Program in Tetrahymena.

    Science.gov (United States)

    Sandoval, Pamela Y; Lee, Po-Hsuen; Meng, Xiangzhou; Kapler, Geoffrey M

    2015-07-01

    The intra-S phase checkpoint kinase of metazoa and yeast, ATR/MEC1, protects chromosomes from DNA damage and replication stress by phosphorylating subunits of the replicative helicase, MCM2-7. Here we describe an unprecedented ATR-dependent pathway in Tetrahymena thermophila in which the essential pre-replicative complex proteins, Orc1p, Orc2p and Mcm6p are degraded in hydroxyurea-treated S phase cells. Chromosomes undergo global changes during HU-arrest, including phosphorylation of histone H2A.X, deacetylation of histone H3, and an apparent diminution in DNA content that can be blocked by the deacetylase inhibitor sodium butyrate. Most remarkably, the cell cycle rapidly resumes upon hydroxyurea removal, and the entire genome is replicated prior to replenishment of ORC and MCMs. While stalled replication forks are elongated under these conditions, DNA fiber imaging revealed that most replicating molecules are produced by new initiation events. Furthermore, the sole origin in the ribosomal DNA minichromosome is inactive and replication appears to initiate near the rRNA promoter. The collective data raise the possibility that replication initiation occurs by an ORC-independent mechanism during the recovery from HU-induced replication stress. PMID:26218270

  11. The E3 ubiquitin ligase EDD regulates S-phase and G(2)/M DNA damage checkpoints.

    Science.gov (United States)

    Munoz, Marcia A; Saunders, Darren N; Henderson, Michelle J; Clancy, Jennifer L; Russell, Amanda J; Lehrbach, Gillian; Musgrove, Elizabeth A; Watts, Colin K W; Sutherland, Robert L

    2007-12-15

    The cellular response to DNA damage is critical for maintenance of genomic integrity and inhibition of tumorigenesis. Mutations or aberrant expression of the E3 ubiquitin ligase EDD have been observed in a number of carcinomas and we recently reported that EDD modulates activity of the DNA damage checkpoint kinase, CHK2. Here, we demonstrate that EDD is necessary for G(1)/S and intra S phase DNA damage checkpoint activation and for the maintenance of G(2)/M arrest after double strand DNA breaks. Defective checkpoint activation in EDD-depleted cells led to radio-resistant DNA synthesis, premature entry into mitosis, accumulation of polyploid cells, and cell death via mitotic catastrophe. In addition to decreased CHK2 activation in EDD-depleted cells, the expression of several key cell cycle mediators including Cdc25A/C and E2F1 was altered, suggesting that these checkpoint defects may be both CHK2-dependent and -independent. These data support a role for EDD in the maintenance of genomic stability, emphasising the potential importance of dysregulated EDD expression and/or function in the evolution of cancer. PMID:18073532

  12. Anaphase onset before complete DNA replication with intact checkpoint responses

    DEFF Research Database (Denmark)

    Torres-Rosell, Jordi; De Piccoli, Giacomo; Cordon-Preciado, Violeta;

    2007-01-01

    Cellular checkpoints prevent mitosis in the presence of stalled replication forks. Whether checkpoints also ensure the completion of DNA replication before mitosis is unknown. Here, we show that in yeast smc5-smc6 mutants, which are related to cohesin and condensin, replication is delayed, most...

  13. Immune checkpoint inhibition in lymphoid disease.

    Science.gov (United States)

    Eyre, Toby A; Collins, Graham P

    2015-08-01

    It has long been understood that the immune system has intrinsic anti-tumour activity in humans, and that a key mechanism of tumour progression is the ability of a tumour to escape this immune surveillance. A number of attempts have been made to harness this anti-tumour immunity in both solid tumour oncology and haematological malignancies with variable success. Examples include the use of allogeneic stem cell transplantation and donor lymphocyte infusion in haematological cancer and vaccine studies in solid tumours. Enhanced signalling of the Programmed cell death-1 (PDCD1, PD-1)/cytotoxic T-lymphocyte-associated protein 4 (CTLA4) 'immune checkpoint' pathway has emerged recently as a critical mechanism by which tumours can escape the natural anti-tumour immune response. As such, novel therapies have been developed to help enhance this natural immunity by switching off the PDCD1/CTLA4 immune checkpoint pathway. The following review will discuss the pathobiology of these pathways and the exciting new data now available in lymphoid malignancies. PMID:25824455

  14. Developmental checkpoints guarded by regulated necrosis.

    Science.gov (United States)

    Dillon, Christopher P; Tummers, Bart; Baran, Katherine; Green, Douglas R

    2016-06-01

    The process of embryonic development is highly regulated through the symbiotic control of differentiation and programmed cell death pathways, which together sculpt tissues and organs. The importance of programmed necrotic (RIPK-dependent necroptosis) cell death during development has recently been recognized as important and has largely been characterized using genetically engineered animals. Suppression of necroptosis appears to be essential for murine development and occurs at three distinct checkpoints, E10.5, E16.5, and P1. These distinct time points have helped delineate the molecular pathways and regulation of necroptosis. The embryonic lethality at E10.5 seen in knockouts of caspase-8, FADD, or FLIP (cflar), components of the extrinsic apoptosis pathway, resulted in pallid embryos that did not exhibit the expected cellular expansions. This was the first suggestion that these factors play an important role in the inhibition of necroptotic cell death. The embryonic lethality at E16.5 highlighted the importance of TNF engaging necroptosis in vivo, since elimination of TNFR1 from casp8 (-/-), fadd (-/-), or cflar (-/-), ripk3 (-/-) embryos delayed embryonic lethality from E10.5 until E16.5. The P1 checkpoint demonstrates the dual role of RIPK1 in both the induction and inhibition of necroptosis, depending on the upstream signal. This review summarizes the role of necroptosis in development and the genetic evidence that helped detail the molecular mechanisms of this novel pathway of programmed cell death. PMID:27056574

  15. Immune checkpoints in cancer clinical trials

    Institute of Scientific and Technical Information of China (English)

    Elad Sharon; Howard Streicher; Priscila Goncalves; Helen XChen

    2014-01-01

    Immunology-based therapy is rapidly developing into an effective treatment option for a surprising range of cancers. We have learned over the last decade that powerful immunologic effector cells may be blocked by inhibitory regulatory pathways controlled by specific molecules often called“immune checkpoints.” These checkpoints serve to control or turn off the immune response when it is no longer needed to prevent tissue injury and autoimmunity. Cancer cells have learned or evolved to use these mechanisms to evade immune control and elimination. The development of a new therapeutic class of drugs that inhibit these inhibitory pathways has recently emerged as a potent strategy in oncology. Three sets of agents have emerged in clinical trials exploiting this strategy. These agents are antibody-based therapies targeting cytotoxic T-lymphocyte antigen4 (CTLA4), programmed cell death1 (PD-1), and programmed cell death ligand 1 (PD-L1). These inhibitors of immune inhibition have demonstrated extensive activity as single agents and in combinations. Clinical responses have been seen in melanoma, renal cellcarcinoma, non-smal celllung cancer, and several other tumor types. Despite the autoimmune or inflammatory immune-mediated adverse effects which have been seen, the responses and overall survival benefits exhibited thus far warrant further clinical development.

  16. DMTCP: Scalable User-Level Transparent Checkpointing for Cluster Computations

    CERN Document Server

    Ansel, Jason; Arya, Kapil

    2008-01-01

    As the size of clusters increases, failures are becoming increasingly frequent. Applications must become fault tolerant if they are to run for extended periods of time. We present DMTCP (Distributed MultiThreaded CheckPointing), the first user-level distributed checkpointing package not dependent on a specific message passing library. This contrasts with existing approaches either specific to libraries such as MPI or requiring kernel modification. DMTCP provides fault tolerance through checkpointing. DMTCP transparently checkpoints general cluster computations consisting of many nodes, processes, and threads. DMTCP automatically accounts for TCP/IP sockets, UNIX domain sockets, pipes, ptys (pseudo-terminals), signal handlers, ordinary file descriptors, shared file descriptors, and other operating system artifacts. We demonstrate checkpointing and restart of applications communicating through MPICH2, OpenMPI, and sockets directly. These applications were written with a variety of languages including Fortran, C...

  17. FORMAL VERIFICATION OF DISTRIBUTED CHECKPOINTING USING EVENT-B

    Directory of Open Access Journals (Sweden)

    Girish Chandra

    2015-10-01

    Full Text Available The development of complex system makes challenging task for correct software development. Due to faulty specification, software may involve errors. The traditional testing methods are not sufficient to verify the correctness of such complex system. In order to capture correct system requirements and rigorous reasoning about the problems, formal methods are required. Formal methods are mathematical techniques that provide precise specification of problems with their solutions and proof of correctness. In this paper, we have done formal verification of check pointing process in a distributed database system using Event B. Event-B is an event driven formal method which is used to develop formal models of distributed database systems. In a distributed database system, the database is stored at different sites that are connected together through the network. Checkpoint is a recovery point which contains the state information about the site. In order to do recovery of a distributed transaction a global checkpoint number (GCPN is required. A global checkpoint number decides which transaction will be included for recovery purpose. All transactions whose timestamp are less than global checkpoint number will be marked as before checkpoint transaction (BCPT and will be considered for recovery purpose. The transactions whose timestamp are greater than GCPN will be marked as after checkpoint transaction (ACPT and will be part of next global checkpoint number.

  18. Keeping checkpoint/restart viable for exascale systems.

    Energy Technology Data Exchange (ETDEWEB)

    Riesen, Rolf E.; Bridges, Patrick G. (IBM Research, Ireland, Mulhuddart, Dublin); Stearley, Jon R.; Laros, James H., III; Oldfield, Ron A.; Arnold, Dorian (University of New Mexico, Albuquerque, NM); Pedretti, Kevin Thomas Tauke; Ferreira, Kurt Brian; Brightwell, Ronald Brian

    2011-09-01

    Next-generation exascale systems, those capable of performing a quintillion (10{sup 18}) operations per second, are expected to be delivered in the next 8-10 years. These systems, which will be 1,000 times faster than current systems, will be of unprecedented scale. As these systems continue to grow in size, faults will become increasingly common, even over the course of small calculations. Therefore, issues such as fault tolerance and reliability will limit application scalability. Current techniques to ensure progress across faults like checkpoint/restart, the dominant fault tolerance mechanism for the last 25 years, are increasingly problematic at the scales of future systems due to their excessive overheads. In this work, we evaluate a number of techniques to decrease the overhead of checkpoint/restart and keep this method viable for future exascale systems. More specifically, this work evaluates state-machine replication to dramatically increase the checkpoint interval (the time between successive checkpoint) and hash-based, probabilistic incremental checkpointing using graphics processing units to decrease the checkpoint commit time (the time to save one checkpoint). Using a combination of empirical analysis, modeling, and simulation, we study the costs and benefits of these approaches on a wide range of parameters. These results, which cover of number of high-performance computing capability workloads, different failure distributions, hardware mean time to failures, and I/O bandwidths, show the potential benefits of these techniques for meeting the reliability demands of future exascale platforms.

  19. Protein phosphatases acting on the replication checkpoint

    OpenAIRE

    Conde, Rui Miguel Esteves Antunes Seabra

    2010-01-01

    A génese de um cancro está dependente da acumulação de mutações genéticas que dão origem a instabilidade genómica, que por sua vez resulta na proliferação descontrolada. Para prevenir a acumulação destas mutações, as células têm mecanismos de controlo (checkpoints) que suspendem o ciclo celular e accionam as vias de reparação do ADN. Estes eventos são muitas vezes regulados por dinâmicas de (des)fosforilação de proteínas. As proteínas fosfatases (PPs), enzimas responsáveis p...

  20. Managing Adverse Events With Immune Checkpoint Agents.

    Science.gov (United States)

    Dadu, Ramona; Zobniw, Chrystia; Diab, Adi

    2016-01-01

    Immune checkpoint inhibitors (anti-cytotoxic T-lymphocyte antigen 4 and anti programmed cell death 1/programmed cell death 1 ligand antibodies) have shown impressive clinical activity in multiple cancer types. Despite achieving great clinical success, challenges and limitations of these drugs as monotherapy or various combinational strategies include the development of a unique set of immune-related adverse events (irAEs) that can be severe and even fatal. Therefore, identification of patients at risk, prevention, consistent communication between patients and medical team, rapid recognition, and treatment of irAEs are critical in optimizing treatment outcomes. This review focuses on the description of more common irAEs and provides a suggested approach for management of specific irAEs. PMID:27111908

  1. Chk2-dependent phosphorylation of XRCC1 in the DNA damage response promotes base excision repair

    OpenAIRE

    Chou, Wen-Cheng; Wang, Hui-Chun; Wong, Fen-Hwa; Ding, Shian-ling; Wu, Pei-Ei; Shieh, Sheau-Yann; Shen, Chen-Yang

    2008-01-01

    The DNA damage response (DDR) has an essential function in maintaining genomic stability. Ataxia telangiectasia-mutated (ATM)-checkpoint kinase 2 (Chk2) and ATM- and Rad3-related (ATR)-Chk1, triggered, respectively, by DNA double-strand breaks and blocked replication forks, are two major DDRs processing structurally complicated DNA damage. In contrast, damage repaired by base excision repair (BER) is structurally simple, but whether, and how, the DDR is involved in repairing this damage is un...

  2. Drosophila MOF controls Checkpoint protein2 and regulates genomic stability during early embryogenesis

    Directory of Open Access Journals (Sweden)

    Pushpavalli Sreerangam NCVL

    2013-01-01

    Full Text Available Abstract Background In Drosophila embryos, checkpoints maintain genome stability by delaying cell cycle progression that allows time for damage repair or to complete DNA synthesis. Drosophila MOF, a member of MYST histone acetyl transferase is an essential component of male X hyperactivation process. Until recently its involvement in G2/M cell cycle arrest and defects in ionizing radiation induced DNA damage pathways was not well established. Results Drosophila MOF is highly expressed during early embryogenesis. In the present study we show that haplo-insufficiency of maternal MOF leads to spontaneous mitotic defects like mitotic asynchrony, mitotic catastrophe and chromatid bridges in the syncytial embryos. Such abnormal nuclei are eliminated and digested in the yolk tissues by nuclear fall out mechanism. MOF negatively regulates Drosophila checkpoint kinase 2 tumor suppressor homologue. In response to DNA damage the checkpoint gene Chk2 (Drosophila mnk is activated in the mof mutants, there by causing centrosomal inactivation suggesting its role in response to genotoxic stress. A drastic decrease in the fall out nuclei in the syncytial embryos derived from mof1/+; mnkp6/+ females further confirms the role of DNA damage response gene Chk2 to ensure the removal of abnormal nuclei from the embryonic precursor pool and maintain genome stability. The fact that mof mutants undergo DNA damage has been further elucidated by the increased number of single and double stranded DNA breaks. Conclusion mof mutants exhibited genomic instability as evidenced by the occurance of frequent mitotic bridges in anaphase, asynchronous nuclear divisions, disruption of cytoskeleton, inactivation of centrosomes finally leading to DNA damage. Our findings are consistent to what has been reported earlier in mammals that; reduced levels of MOF resulted in increased genomic instability while total loss resulted in lethality. The study can be further extended using

  3. A New Adaptive Checkpointing Strategy for Mobile Computing

    Institute of Scientific and Technical Information of China (English)

    MENChaoguang; ZUODecheng; YANGXiaozong

    2005-01-01

    Adaptive checkpointing strategy is an efficient recovery scheme, which is suitable for mobile computing system. However, all existing adaptive checkpointing schemes are not correct to recover system when failure occurs in some special period. In this paper, the issues that will lead to system inconsistency are first discussed and then a new adaptive strategy that can recover system to correct consistent state is proposed. Our algorithm improves system recovery performance because only failure process needs rollback through logging.

  4. A Hierarchical Checkpointing Protocol for Parallel Applications in Cluster Federations

    OpenAIRE

    Monnet, Sébastien; Morin, Christine; Badrinath, Ramamurthy

    2004-01-01

    Code coupling applications can be divided into communicating modules, that may be executed on different clusters in a cluster federation. As a cluster federation comprises of a large number of nodes, there is a high probability of a node failure. We propose a hierarchical checkpointing protocol that combines a synchronized checkpointing technique inside clusters and a communication-induced technique between clusters. This protocol fits to the characteristics of a cluster federation (large num...

  5. Mek1 stabilizes Hop1-Thr318 phosphorylation to promote interhomolog recombination and checkpoint responses during yeast meiosis.

    Science.gov (United States)

    Chuang, Chi-Ning; Cheng, Yun-Hsin; Wang, Ting-Fang

    2012-12-01

    Red1, Hop1 and Mek1 are three yeast meiosis-specific chromosomal proteins that uphold the interhomolog (IH) bias of meiotic recombination. Mek1 is also an effector protein kinase in a checkpoint that responds to aberrant DNA and/or axis structure. The activation of Mek1 requires Red1-dependent Hop1-Thr(T)318 phosphorylation, which is mediated by Mec1 and Tel1, the yeast homologs of the mammalian DNA damage sensor kinases ATR and ATM. As the ectopic expression of Mek1-glutathione S-transferase (GST) was shown to promote IH recombination in the absence of Mec1/Tel1-dependent checkpoint function, it was proposed that Mek1 might play dual roles during meiosis by directly phosphorylating targets that are involved in the recombination checkpoint. Here, we report that Mek1 has a positive feedback activity in the stabilization of Mec1/Tel1-mediated Hop1-T318 phosphorylation against the dephosphorylation mediated by protein phosphatase 4. Our results also reveal that GST-Mek1 or Mek1-GST further increases Hop1-T318 phosphorylation. This positive feedback function of Mek1 is independent of Mek1's kinase activity, but dependent on Mek1's forkhead-associated (FHA) domain and its arginine 51 residue. Arginine 51 directly mediates the interaction of Mek1-FHA and phosphorylated Hop1-T318. We suggest that the Hop1-Mek1 interaction is similar to the Rad53-Dun1 signaling pathway, which is mediated through the interaction of phosphorylated Rad53 and Dun1-FHA. PMID:23047948

  6. DMTCP: bringing interactive checkpoint-restart to Python

    Science.gov (United States)

    Arya, Kapil; Cooperman, Gene

    2015-01-01

    DMTCP (Distributed MultiThreaded CheckPointing) is a mature checkpoint-restart package. It operates in user space without kernel privilege, and adapts to application-specific requirements through plugins. While DMTCP has been able to checkpoint Python and IPython ‘from the outside’ for many years, a Python module has recently been created to support DMTCP. IPython support is included through a new DMTCP plugin. A checkpoint can be requested interactively within a Python session or under the control of a specific Python program. Further, the Python program can execute specific Python code prior to checkpoint, upon resuming (within the original process) and upon restarting (from a checkpoint image). Applications of DMTCP are demonstrated for: (i) Python-based graphics using virtual network client, (ii) a fast/slow technique to use multiple hosts or cores to check one (Cython Behnel S et al 2011 Comput. Sci. Eng. 13 31-39) computation in parallel, and (iii) a reversible debugger, FReD, with a novel reverse-expression watchpoint feature for locating the cause of a bug.

  7. A survey of checkpointing algorithms for parallel and distributed computers

    Indian Academy of Sciences (India)

    S Kalaiselvi; V Rajaraman

    2000-10-01

    Checkpoint is defined as a designated place in a program at which normal processing is interrupted specifically to preserve the status information necessary to allow resumption of processing at a later time. Checkpointing is the process of saving the status information. This paper surveysthe algorithms which have been reported in the literature for checkpointing parallel/distributed systems. It has been observed that most of the algorithms published for checkpointing in message passing systems are based on the seminal article by Chandy and Lamport. A large number of articles have been published in this area by relaxing the assumptions made in this paper and by extending it to minimise the overheads of coordination and context saving. Checkpointing for sharedmemory systems primarily extend cache coherence protocolstomaintain a consistent memory. All of them assume that the main memory is safe for storing the context. Recently algorithms have been published for distributed shared memory systems, which extend the cache coherence protocols used in shared memory systems. They however also include methods for storing the status of distributed memory in stable storage. Most of the algorithms assume that there is no knowledge about the programs being executed.It is howeverfelt that in development of parallel programs the user has to do a fair amount of work in distributing tasks and this information can be effectively used to simplify checkpointing and rollback recovery.

  8. An Analysis of Checkpointing Algorithms for Distributed Mobile Systems

    Directory of Open Access Journals (Sweden)

    Ajay Khunteta

    2010-07-01

    Full Text Available Distributed snapshots are an important building block for distributed systems, and are useful for constructing efficient checkpointing protocols, among other uses. Direct application of these algorithms to mobile systems is not easible, however, due to differences in the environment in which mobile systems operate, relative to general distributed systems. The mobile computing environment introduces newchallenges in the area of fault-tolerant computing. Compared to traditional distributed environments, wireless networks are typically slower, providing lower throughput and latency, comparing to wireline networks. In addition, the mobile hosts have limited computation esources, are often exposed to harsh operating environment that makes them more likely to fail, and can roam while operating. Over the past two decades, intensive research work has been carried out on providing efficient checkpointing protocols in traditional distributed computing. Recently, more attention has been paid to providing checkpointing protocols for mobile systems. Some of these protocols have been adapted from the traditional distributed environment; others have been created from scratch for mobile systems. Checkpoint is defined as a designated place in a program at which normal processing is interrupted specifically to preserve the status information necessary to allow resumption of processing at alater time. Checkpointing is the process of saving the status information. This paper surveys the algorithms which have been reported in the literature for checkpointing in Mobile Distributed systems.

  9. A Tunable Checkpointing Algorithm for Distributed Mobile Applications

    Directory of Open Access Journals (Sweden)

    Sungchae Lim

    2011-11-01

    Full Text Available The aim of a distributed checkpointing algorithm is to efficiently restore the execution state of distributed applications in face of hardware or software failures. Originally, such algorithms were devised for fixed networking systems, of which computing components communicate with each other via wired networks. Therefore, those algorithms usually suffer from heavy networking costs coming from frequent data transits over wireless networks, if they are used in the wireless computing environment. In this paper, to reduce usage of wireless communications, our checkpointing algorithm allows the distributed mobile application to tune the level of its checkpointing strictness. The strictness is defined by the maximum rollback distance (MRD that says how many recent local checkpoints can be rolled back in the worst case. Since our algorithm have more flexibility in checkpointing schedule due to the use of MRD, it is possible to reduce the number of enforced local checkpointing. In particular, the amount of data transited on wirelesses networks becomes smaller than in earlier methods; thus, our algorithm provides less communication cost and shortened blocking time.

  10. Structural insights into recognition of MDC1 by TopBP1 in DNA replication checkpoint control

    OpenAIRE

    Leung, Charles Chung Yun; Sun, Luxin; Gong, Zihua; Burkat, Michael; Edwards, Ross; Assmus, Mark; Chen, Junjie; Glover, J N Mark

    2013-01-01

    Activation of the DNA replication checkpoint by the ATR kinase requires protein interactions mediated by the ATR activating protein, TopBP1. Accumulation of TopBP1 at stalled replication forks requires the interaction of TopBP1 BRCT5 with the phosphorylated SDT repeats of the adaptor protein MDC1. Here we present the X-ray crystal structures of the tandem BRCT4/5 domains of TopBP1 free and in complex with a MDC1 consensus pSDpT phospho-peptide. TopBP1 BRCT4/5 adopts a variant BRCT-BRCT packin...

  11. Review of Some Checkpointing Schemes for Distributed and Mobile Computing Environments

    Directory of Open Access Journals (Sweden)

    Mr Raman Kumar

    2015-05-01

    Full Text Available Fault Tolerance Techniques facilitate systems to carry out tasks in the incidence of faults. A checkpoint is a local state of a process saved on stable storage. In a distributed system, since the processes in the system do not share memory; a global state of the system is defined as a combination of local states, one from each process. In case of a fault in distributed systems, checkpointing enables the execution of a program to be resumed from a previous consistent global state rather than resuming the execution from the commencement. In this way, the sum of constructive processing vanished because of the fault is appreciably reduced. In this paper, we talk about various issues related to the checkpointing for distributed systems and mobile computing environments. We also confer various types of checkpointing: coordinated checkpointing, asynchronous checkpointing, communication induced checkpointing and message logging based checkpointing. We also present a survey of some checkpointing algorithms for distributed systems.

  12. Targeting of Carbon Ion-Induced G2 Checkpoint Activation in Lung Cancer Cells Using Wee-1 Inhibitor MK-1775.

    Science.gov (United States)

    Ma, Hongyu; Takahashi, Akihisa; Sejimo, Yukihiko; Adachi, Akiko; Kubo, Nobuteru; Isono, Mayu; Yoshida, Yukari; Kanai, Tatsuaki; Ohno, Tatsuya; Nakano, Takashi

    2015-12-01

    The potent inhibitor of the cell cycle checkpoint regulatory factor Wee-1, MK-1775, has been reported to enhance non-small cell lung cancer (NSCLC) cell sensitivity to photon radiation by abrogating radiation-induced G2 arrest. However, little is known about the effects of this sensitizer after exposure to carbon (C)-ion radiation. The purpose of this study was therefore to investigate the effects of C ions in combination with MK-1775 on the killing of NSCLC cells. Human NSCLC H1299 cells were exposed to X rays or C ions (290 MeV/n, 50 keV/μm at the center of a 6 cm spread-out Bragg peak) in the presence of MK-1775. The cell cycle was analyzed using flow cytometry and Western blotting. Radiosensitivity was determined using clonogenic survival assays. The mechanisms underlying MK-1775 radiosensitization were studied by observing H2AX phosphorylation and mitotic catastrophe. G2 checkpoint arrest was enhanced 2.3-fold by C-ion exposure compared with X-ray exposure. Radiation-induced G2 checkpoint arrest was abrogated by MK-1775. Exposure to radiation resulted in a significant reduction in the mitotic ratio and increased phosphorylation of cyclin-dependent kinase 1 (Cdk1), the primary downstream mediator of Wee-1-induced G2 arrest. The Wee-1 inhibitor, MK-1775 restored the mitotic ratio and suppressed Cdk1 phosphorylation. In addition, MK-1775 increased H1299 cell sensitivity to C ions and X rays independent of TP53 status. MK-1775 also significantly increased H2AX phosphorylation and mitotic catastrophe in irradiated cells. These results suggest that the G2 checkpoint inhibitor MK-1775 can enhance the sensitivity of human NSCLC cells to C ions as well as X rays. PMID:26645158

  13. Berkeley lab checkpoint/restart (BLCR) for Linux clusters

    Science.gov (United States)

    Hargrove, Paul H.; Duell, Jason C.

    2006-09-01

    This article describes the motivation, design and implementation of Berkeley Lab Checkpoint/Restart (BLCR), a system-level checkpoint/restart implementation for Linux clusters that targets the space of typical High Performance Computing applications, including MPI. Application-level solutions, including both checkpointing and fault-tolerant algorithms, are recognized as more time and space efficient than system-level checkpoints, which cannot make use of any application-specific knowledge. However, system-level checkpointing allows for preemption, making it suitable for responding to ''fault precursors'' (for instance, elevated error rates from ECC memory or network CRCs, or elevated temperature from sensors). Preemption can also increase the efficiency of batch scheduling; for instance reducing idle cycles (by allowing for shutdown without any queue draining period or reallocation of resources to eliminate idle nodes when better fitting jobs are queued), and reducing the average queued time (by limiting large jobs to running during off-peak hours, without the need to limit the length of such jobs). Each of these potential uses makes BLCR a valuable tool for efficient resource management in Linux clusters.

  14. Message Efficient Checkpointing and Rollback Recovery in Heterogeneous Mobile Networks

    Science.gov (United States)

    Jaggi, Parmeet Kaur; Singh, Awadhesh Kumar

    2016-06-01

    Heterogeneous networks provide an appealing way of expanding the computing capability of mobile networks by combining infrastructure-less mobile ad-hoc networks with the infrastructure-based cellular mobile networks. The nodes in such a network range from low-power nodes to macro base stations and thus, vary greatly in their capabilities such as computation power and battery power. The nodes are susceptible to different types of transient and permanent failures and therefore, the algorithms designed for such networks need to be fault-tolerant. The article presents a checkpointing algorithm for the rollback recovery of mobile hosts in a heterogeneous mobile network. Checkpointing is a well established approach to provide fault tolerance in static and cellular mobile distributed systems. However, the use of checkpointing for fault tolerance in a heterogeneous environment remains to be explored. The proposed protocol is based on the results of zigzag paths and zigzag cycles by Netzer-Xu. Considering the heterogeneity prevalent in the network, an uncoordinated checkpointing technique is employed. Yet, useless checkpoints are avoided without causing a high message overhead.

  15. Berkeley lab checkpoint/restart (BLCR) for Linux clusters

    International Nuclear Information System (INIS)

    This article describes the motivation, design and implementation of Berkeley Lab Checkpoint/Restart (BLCR), a system-level checkpoint/restart implementation for Linux clusters that targets the space of typical High Performance Computing applications, including MPI. Application-level solutions, including both checkpointing and fault-tolerant algorithms, are recognized as more time and space efficient than system-level checkpoints, which cannot make use of any application-specific knowledge. However, system-level checkpointing allows for preemption, making it suitable for responding to ''fault precursors'' (for instance, elevated error rates from ECC memory or network CRCs, or elevated temperature from sensors). Preemption can also increase the efficiency of batch scheduling; for instance reducing idle cycles (by allowing for shutdown without any queue draining period or reallocation of resources to eliminate idle nodes when better fitting jobs are queued), and reducing the average queued time (by limiting large jobs to running during off-peak hours, without the need to limit the length of such jobs). Each of these potential uses makes BLCR a valuable tool for efficient resource management in Linux clusters

  16. The blockade of immune checkpoints in cancer immunotherapy

    Science.gov (United States)

    Pardoll, Drew M.

    2016-01-01

    Among the most promising approaches to activating therapeutic antitumour immunity is the blockade of immune checkpoints. Immune checkpoints refer to a plethora of inhibitory pathways hardwired into the immune system that are crucial for maintaining self-tolerance and modulating the duration and amplitude of physiological immune responses in peripheral tissues in order to minimize collateral tissue damage. It is now clear that tumours co-opt certain immune-checkpoint pathways as a major mechanism of immune resistance, particularly against T cells that are specific for tumour antigens. Because many of the immune checkpoints are initiated by ligand–receptor interactions, they can be readily blocked by antibodies or modulated by recombinant forms of ligands or receptors. Cytotoxic T-lymphocyte-associated antigen 4 (CTLA4) antibodies were the first of this class of immunotherapeutics to achieve US Food and Drug Administration (FDA) approval. Preliminary clinical findings with blockers of additional immune-checkpoint proteins, such as programmed cell death protein 1 (PD1), indicate broad and diverse opportunities to enhance antitumour immunity with the potential to produce durable clinical responses. PMID:22437870

  17. Checkpoint Inhibitors for the Treatment of Hodgkin Lymphoma.

    Science.gov (United States)

    Bennani-Baiti, Nabila; Thanarajasingam, Gita; Ansell, Stephen

    2016-06-01

    Hodgkin lymphoma's (HL) tumor composition is characterized by a paucity of malignant cells and a preponderance of immune and stromal cells. Despite the rich immune milieu within the tumor microenvironment, malignant cells are able to effectively evade the immune system and use immune support to promote lymphoma cell growth and proliferation. Recognizing this has led to the identification of checkpoint inhibitory signals that enable immune evasion and to opening the door to therapeutic strategies on how to exploit the immune system in targeting tumor cells. We discuss herein some of the tumor evasion mechanisms in HL with a particular focus on the immune checkpoint pathways and focus on recent clinical data of checkpoint blockade in HL treatment. PMID:26818843

  18. Immune checkpoint blockade therapy for bladder cancer treatment.

    Science.gov (United States)

    Kim, Jayoung

    2016-06-01

    Bladder cancer remains the most immunogenic and expensive malignant tumor in the United States today. As the 4th leading cause of death from cancer in United States, Immunotherapy blocking immune checkpoints have been recently been applied to many aggressive cancers and changed interventions of urological cancers including advanced bladder cancer. The applied inhibition of PD-1-PD-L1 interactions can restore antitumor T-cell activity and enhance the cellular immune attack on antigens. The overall goals of this short review article are to introduce current cancer immunotherapy and immune checkpoint inhibitors, and to provide new insight into the underlying mechanisms that block immune checkpoints in tumor microenvironment. Furthermore, this review will address the preclinical and clinical trials to determine whether bladder cancer patients could benefit from this new cancer therapy in near future. PMID:27326412

  19. Low-Overhead Non-Blocking Checkpointing Scheme for Mobile Computing Systems

    Institute of Scientific and Technical Information of China (English)

    MEN Chaoguang; CAO Liujuan; WANG Liwen; XU Zhenpeng

    2007-01-01

    When applied to mobile computing systems, checkpoint protocols for distributed computing systems would face many new challenges, such as low wireless bandwidth, frequent disconnections, and lack of stable storage at mobile hosts. This paper proposes a novel checkpoint protocol to effectively reduce the coordinating overhead. By using a communication vector, only a few processes participate in the checkpointing event. During checkpointing, the scheme can save the time used to trace the dependency tree by sending checkpoint requests to dependent processes at once. In addition, processes are non-blocking in this scheme, since the inconsistency is resolved by the piggyback technique. Hence the unnecessary and orphan messages can be avoided. Compared with the traditional coordinated checkpoint approach, the proposed non-blocking algorithm obtains a minimal number of processes to take checkpoints. It also reduces the checkpoint latency, which brings less overhead to mobile host with limited resources.

  20. Keeping it together in times of stress: checkpoint function at stalled replication forks

    OpenAIRE

    Berens, Theresa J.; David P Toczyski

    2012-01-01

    In this issue, De Piccoli et al. (2012) show that, contrary to current models of DNA replication checkpoint function, replication proteins remain associated with each other and with replicating DNA when replication is stressed in checkpoint-deficient cells.

  1. Loss of ATM kinase activity leads to embryonic lethality in mice

    DEFF Research Database (Denmark)

    Daniel, J.A.; Pellegrini, M.; Filsuf, D.;

    2012-01-01

    Ataxia telangiectasia (A-T) mutated (ATM) is a key deoxyribonucleic acid (DNA) damage signaling kinase that regulates DNA repair, cell cycle checkpoints, and apoptosis. The majority of patients with A-T, a cancer-prone neurodegenerative disease, present with null mutations in Atm. To determine...

  2. BRCA1 and its phosphorylation involved in caffeine-inhibitable event upstream of G2 checkpoint

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Caffeine,which specifically inhibits ATM/ATR kinases,efficiently abrogates the ionizing radiation(IR)-induced G2 arrest and increases the sensitivity of various tumor cells to IR.Mechanisms for the effect of caffeine remain to be elucidated.As a target of ATM/ATR kinases,BRCA1 becomes activated and phosphorylated in response to IR.Thus,in this work,we investigated the possible role of BRCA1 in the effect of caffeine on G2 checkpoint and observed how BRCA1 phosphorylation was regulated in this process.For these purposes,the BRCA1 protein level and the phosphorylation states were analyzed by Western blotting by using an antibody against BRCA1 and phospho-specific antibodies against Ser-1423 and Ser-1524 residues in cells exposed to a combination of IR and caffeine.The results showed that caffeine down-regulated IR-induced BRCA1 expression and specifically abolished BRCA1 phosphorylation of Ser-1524,which was followed by an override of G2 arrest by caffeine.In addition,the ability of BRCA1 to transactivate p21 may be required for MCF-7 but not necessary for Hela response to caffeine.These data suggest that BRCA1 may be a potential target of caffeine.BRCA1 and its phosphorylation are most likely to be involved in the caffeine-inhibitable event upstream of G2 arrest.

  3. BRCA1 and its phosphorylation involved in caffeine-inhibitable event upstream of G2 checkpoint

    Science.gov (United States)

    Li, Ning; Zhang, Hong; Wang, Yanling; Hao, Jifang

    2010-07-01

    Caffeine, which specifically inhibits ATM/ATR kinases, efficiently abrogates the ionizing radiation (IR)-induced G2 arrest and increases the sensitivity of various tumor cells to IR. Mechanisms for the effect of caffeine remain to be elucidated. As a target of ATM/ATR kinases, BRCA1 becomes activated and phosphorylated in response to IR. Thus, in this work, we investigated the possible role of BRCA1 in the effect of caffeine on G2 checkpoint and observed how BRCA1 phosphorylation was regulated in this process. For these purposes, the BRCA1 protein level and the phosphorylation states were analyzed by Western blotting by using an antibody against BRCA1 and phospho-specific antibodies against Ser-1423 and Ser-1524 residues in cells exposed to a combination of IR and caffeine. The results showed that caffeine down-regulated IR-induced BRCA1 expression and specifically abolished BRCA1 phosphorylation of Ser-1524, which was followed by an override of G2 arrest by caffeine. In addition, the ability of BRCA1 to transactivate p21 may be required for MCF-7 but not necessary for Hela response to caffeine. These data suggest that BRCA1 may be a potential target of caffeine. BRCA1 and its phosphorylation are most likely to be involved in the caffeine-inhibitable event upstream of G2 arrest.

  4. Immune-Checkpoint Blockade and Active Immunotherapy for Glioma

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Brian J. [Department of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213 (United States); Brain Tumor Program, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213 (United States); Pollack, Ian F. [Brain Tumor Program, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213 (United States); Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213 (United States); Okada, Hideho, E-mail: okadah@upmc.edu [Department of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213 (United States); Brain Tumor Program, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213 (United States); Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213 (United States); Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213 (United States)

    2013-11-01

    Cancer immunotherapy has made tremendous progress, including promising results in patients with malignant gliomas. Nonetheless, the immunological microenvironment of the brain and tumors arising therein is still believed to be suboptimal for sufficient antitumor immune responses for a variety of reasons, including the operation of “immune-checkpoint” mechanisms. While these mechanisms prevent autoimmunity in physiological conditions, malignant tumors, including brain tumors, actively employ these mechanisms to evade from immunological attacks. Development of agents designed to unblock these checkpoint steps is currently one of the most active areas of cancer research. In this review, we summarize recent progresses in the field of brain tumor immunology with particular foci in the area of immune-checkpoint mechanisms and development of active immunotherapy strategies. In the last decade, a number of specific monoclonal antibodies designed to block immune-checkpoint mechanisms have been developed and show efficacy in other cancers, such as melanoma. On the other hand, active immunotherapy approaches, such as vaccines, have shown encouraging outcomes. We believe that development of effective immunotherapy approaches should ultimately integrate those checkpoint-blockade agents to enhance the efficacy of therapeutic approaches. With these agents available, it is going to be quite an exciting time in the field. The eventual success of immunotherapies for brain tumors will be dependent upon not only an in-depth understanding of immunology behind the brain and brain tumors, but also collaboration and teamwork for the development of novel trials that address multiple layers of immunological challenges in gliomas.

  5. The absence of a DNA replication checkpoint in porcine zygotes

    Czech Academy of Sciences Publication Activity Database

    Vacková, I.; Křen, Radomír; Loi, P.; Krylov, V.; Fulka Jr., J.

    2006-01-01

    Roč. 14, 1 (2006), s. 33-37. ISSN 0967-1994 Institutional research plan: CEZ:AV0Z50450515 Keywords : checkpoint * DNA replication * fertilization Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 0.782, year: 2006

  6. Immune-Checkpoint Blockade and Active Immunotherapy for Glioma

    Directory of Open Access Journals (Sweden)

    Brian J. Ahn

    2013-11-01

    Full Text Available Cancer immunotherapy has made tremendous progress, including promising results in patients with malignant gliomas. Nonetheless, the immunological microenvironment of the brain and tumors arising therein is still believed to be suboptimal for sufficient antitumor immune responses for a variety of reasons, including the operation of “immune-checkpoint” mechanisms. While these mechanisms prevent autoimmunity in physiological conditions, malignant tumors, including brain tumors, actively employ these mechanisms to evade from immunological attacks. Development of agents designed to unblock these checkpoint steps is currently one of the most active areas of cancer research. In this review, we summarize recent progresses in the field of brain tumor immunology with particular foci in the area of immune-checkpoint mechanisms and development of active immunotherapy strategies. In the last decade, a number of specific monoclonal antibodies designed to block immune-checkpoint mechanisms have been developed and show efficacy in other cancers, such as melanoma. On the other hand, active immunotherapy approaches, such as vaccines, have shown encouraging outcomes. We believe that development of effective immunotherapy approaches should ultimately integrate those checkpoint-blockade agents to enhance the efficacy of therapeutic approaches. With these agents available, it is going to be quite an exciting time in the field. The eventual success of immunotherapies for brain tumors will be dependent upon not only an in-depth understanding of immunology behind the brain and brain tumors, but also collaboration and teamwork for the development of novel trials that address multiple layers of immunological challenges in gliomas.

  7. Attachment issues : kinetochore transformations and spindle checkpoint silencing

    NARCIS (Netherlands)

    Etemad, Banafsheh; Kops, Geert Jpl

    2016-01-01

    Cell division culminates in the segregation of duplicated chromosomes in opposite directions prior to cellular fission. This process is guarded by the spindle assembly checkpoint (SAC), which prevents the anaphase of cell division until stable connections between spindle microtubules and the kinetoc

  8. Immune-Checkpoint Blockade and Active Immunotherapy for Glioma

    International Nuclear Information System (INIS)

    Cancer immunotherapy has made tremendous progress, including promising results in patients with malignant gliomas. Nonetheless, the immunological microenvironment of the brain and tumors arising therein is still believed to be suboptimal for sufficient antitumor immune responses for a variety of reasons, including the operation of “immune-checkpoint” mechanisms. While these mechanisms prevent autoimmunity in physiological conditions, malignant tumors, including brain tumors, actively employ these mechanisms to evade from immunological attacks. Development of agents designed to unblock these checkpoint steps is currently one of the most active areas of cancer research. In this review, we summarize recent progresses in the field of brain tumor immunology with particular foci in the area of immune-checkpoint mechanisms and development of active immunotherapy strategies. In the last decade, a number of specific monoclonal antibodies designed to block immune-checkpoint mechanisms have been developed and show efficacy in other cancers, such as melanoma. On the other hand, active immunotherapy approaches, such as vaccines, have shown encouraging outcomes. We believe that development of effective immunotherapy approaches should ultimately integrate those checkpoint-blockade agents to enhance the efficacy of therapeutic approaches. With these agents available, it is going to be quite an exciting time in the field. The eventual success of immunotherapies for brain tumors will be dependent upon not only an in-depth understanding of immunology behind the brain and brain tumors, but also collaboration and teamwork for the development of novel trials that address multiple layers of immunological challenges in gliomas

  9. Checkpointing for graceful degradation in distributed embedded systems

    Science.gov (United States)

    Sababha, Belal Hussein

    Graceful degradation is an approach to developing dependable safety-critical embedded applications, where redundant active or standby resources are used to cope with faults through a system reconfiguration at run-time. Compared to traditional hardware and software redundancy, it is a promising technique that may achieve dependability with a significant reduction in cost, size, weight, and power requirements. Reconfiguration at run-time necessitates using proper checkpointing protocols to support state reservation to ensure correct task restarts after a system reconfiguration. One of the most common checkpointing protocols are communication induced checkpointing (CIC) protocols, which are well developed and understood for large parallel and information systems, but not much has been done for resource limited embedded systems. This work implements and evaluates some of the most common CIC protocols in a periodic resource constrained distributed embedded system for graceful degradation purposes. A test-bed has been developed and used for the evaluation of the various protocols. The implemented protocols are thoroughly studied and performances are contrasted. Specifically the periodicity property and how it benefits checkpointing in embedded systems is investigated. This work introduces a unique effort of CIC protocol implementation and evaluation in the field of distributed embedded systems. Other than providing a test-bed for graceful degradation support, this work shows that some checkpointing protocols that are not efficient in large information systems and supercomputers perform well in embedded systems. We show that a simple index-based CIC protocol, such as the BCS protocol, is more appropriate in embedded system applications compared to other protocols that piggyback a significant amount of information to reduce the number of forced checkpoints. Finally, this work proposes a whole graceful degradation approach to achieve fault tolerance in resource constrained

  10. Cyclin-dependent kinase suppression by WEE1 kinase protects the genome through control of replication initiation and nucleotide consumption

    DEFF Research Database (Denmark)

    Beck, Halfdan; Nähse-Kumpf, Viola; Larsen, Marie Sofie Yoo;

    2012-01-01

    . Furthermore, addition of nucleosides counteracts the effects of unscheduled CDK activity on fork speed and DNA DSB formation. Finally, we show that WEE1 regulates the IR-induced S phase checkpoint, consistent with its role in control of replication initiation. In conclusion, these results suggest that...... deregulated CDK activity, such as that occurring following inhibition of WEE1 kinase or activation of oncogenes, induces replication stress and loss of genomic integrity through increased firing of replication origins and subsequent nucleotide shortage....

  11. Cell size checkpoint control by the retinoblastoma tumor suppressor pathway.

    Directory of Open Access Journals (Sweden)

    Su-Chiung Fang

    2006-10-01

    Full Text Available Size control is essential for all proliferating cells, and is thought to be regulated by checkpoints that couple cell size to cell cycle progression. The aberrant cell-size phenotypes caused by mutations in the retinoblastoma (RB tumor suppressor pathway are consistent with a role in size checkpoint control, but indirect effects on size caused by altered cell cycle kinetics are difficult to rule out. The multiple fission cell cycle of the unicellular alga Chlamydomonas reinhardtii uncouples growth from division, allowing direct assessment of the relationship between size phenotypes and checkpoint function. Mutations in the C. reinhardtii RB homolog encoded by MAT3 cause supernumerous cell divisions and small cells, suggesting a role for MAT3 in size control. We identified suppressors of an mat3 null allele that had recessive mutations in DP1 or dominant mutations in E2F1, loci encoding homologs of a heterodimeric transcription factor that is targeted by RB-related proteins. Significantly, we determined that the dp1 and e2f1 phenotypes were caused by defects in size checkpoint control and were not due to a lengthened cell cycle. Despite their cell division defects, mat3, dp1, and e2f1 mutants showed almost no changes in periodic transcription of genes induced during S phase and mitosis, many of which are conserved targets of the RB pathway. Conversely, we found that regulation of cell size was unaffected when S phase and mitotic transcription were inhibited. Our data provide direct evidence that the RB pathway mediates cell size checkpoint control and suggest that such control is not directly coupled to the magnitude of periodic cell cycle transcription.

  12. Pch2 acts through Xrs2 and Tel1/ATM to modulate interhomolog bias and checkpoint function during meiosis.

    Directory of Open Access Journals (Sweden)

    Hsuan-Chung Ho

    2011-11-01

    Full Text Available Proper segregation of chromosomes during meiosis requires the formation and repair of double-strand breaks (DSBs to form crossovers. Repair is biased toward using the homolog as a substrate rather than the sister chromatid. Pch2 is a conserved member of the AAA(+-ATPase family of proteins and is implicated in a wide range of meiosis-specific processes including the recombination checkpoint, maturation of the chromosome axis, crossover control, and synapsis. We demonstrate a role for Pch2 in promoting and regulating interhomolog bias and the meiotic recombination checkpoint in response to unprocessed DSBs through the activation of axial proteins Hop1 and Mek1 in budding yeast. We show that Pch2 physically interacts with the putative BRCT repeats in the N-terminal region of Xrs2, a member of the MRX complex that acts at sites of unprocessed DSBs. Pch2, Xrs2, and the ATM ortholog Tel1 function in the same pathway leading to the phosphorylation of Hop1, independent of Rad17 and the ATR ortholog Mec1, which respond to the presence of single-stranded DNA. An N-terminal deletion of Xrs2 recapitulates the pch2Δ phenotypes for signaling unresected breaks. We propose that interaction with Xrs2 may enable Pch2 to remodel chromosome structure adjacent to the site of a DSB and thereby promote accessibility of Hop1 to the Tel1 kinase. In addition, Xrs2, like Pch2, is required for checkpoint-mediated delay conferred by the failure to synapse chromosomes.

  13. DNA-damage response network at the crossroads of cell-cycle checkpoints,cellular senescence and apoptosis

    Institute of Scientific and Technical Information of China (English)

    SCHMITT Estelle; PAQUET Claudie; BEAUCHEMIN Myriam; BERTRAND Richard

    2007-01-01

    Tissue homeostasis requires a carefully-orchestrated balance between cell proliferation,cellular senescence and cell death.Cells proliferate through a cell cycle that is tightly regulated by cyclin-dependent kinase activities.Cellular senescence is a safeguard program limiting the proliferative competence of cells in living organisms.Apoptosis eliminates unwanted cells by the coordinated activity of gene products that regulate and effect cell death.The intimate link between the cell cycle,cellular senescence,apoptosis regulation,cancer development and tumor responses to cancer treatment has become eminently apparent.Extensive research on tumor suppressor genes,oncogenes,the cell cycle and apoptosis regulatory genes has revealed how the DNA damage-sensing and -signaling pathways,referred to as the DNA-damage response network,are tied to cell proliferation,cell-cycle arrest,cellular senescence and apoptosis.DNA-damage responses are complex,involving "sensor" proteins that sense the damage,and transmit signals to "transducer" proteins,which,in turn,convey the signals to numerous "effector" proteins implicated in specific cellular pathways,including DNA repair mechanisms,cell-cycle checkpoints,cellular senescence and apoptosis.The Bcl-2 family of proteins stands among the most crucial regulators of apoptosis and performs vital functions in deciding whether a cell will live or die after cancer chemotherapy and irradiation.In addition,several studies have now revealed that members of the Bcl-2 family also interface with the cell cycle,DNA repair/recombination and cellular senescence,effects that are generally distinct from their function in apoptosis.In this review,we report progress in understanding the molecular networks that regulate cell-cycle checkpoints,cellular senescence and apoptosis after DNA damage,and discuss the influence of some Bcl-2 family members on cell-cycle checkpoint regulation.

  14. Review of some Minimum-Process Synchronous Checkpointing Schemes for Mobile Distributed Systems

    Directory of Open Access Journals (Sweden)

    Preeti Gupta,

    2010-07-01

    Full Text Available The term Distributed Systems is used to describe a system with the following characteristics: i it consists of several computers that do not share memory or a clock, ii the computers communicate with each other by exchanging messages over a communication network, iii each computer has its own memory and runs its own operating system. A mobile computing system is a distributed system where some of processes are running on mobile hosts (MHs, whose location in the network changes with time. The number of processes that take checkpoints is minimized to 1 avoid awakening of MHs in doze mode of operation, 2 minimize thrashing of MHs with checkpointing activity, 3 save limited battery life of MHs and low bandwidth of wireless channels. In minimum-process checkpointing protocols, some useless checkpoints are taken or blocking of processes takes place. To take a checkpoint, an MH has to transfer a large amount of checkpoint data to its local MSS over the wireless network. Since the wireless network has low bandwidth and MHs have low computation power, all-process checkpointing will waste the scarce resources of the mobile system on every checkpoint.Minimum-process coordinated checkpointing is a preferred approach for mobile distributed systems. In this paper, we discuss various existing minimum-process checkpointing protocols for mobile distributed systems.

  15. Epigenetic modifiers in immunotherapy: a focus on checkpoint inhibitors.

    Science.gov (United States)

    Terranova-Barberio, Manuela; Thomas, Scott; Munster, Pamela N

    2016-06-01

    Immune surveillance should be directed to suppress tumor development and progression, involving a balance of coinhibitory and costimulatory signals that amplify immune response without overwhelming the host. Immunotherapy confers durable clinical benefit in 'immunogenic tumors', whereas in other tumors the responses are modest. Thus, immune checkpoint inhibitors may need to be combined with strategies to boost immune response or increase the tumor immune profile. Epigenetic aberrations contribute significantly to carcinogenesis. Recent findings suggest that epigenetic drugs prime the immune response by increasing expression of tumor-associated antigens and immune-related genes, as well as modulating chemokines and cytokines involved in immune system activation. This review describes our current understanding regarding epigenetic and immunotherapy combination, focusing on immune response priming to checkpoint blockade. PMID:27197539

  16. Checkpoint signaling from a single DNA interstrand crosslink

    OpenAIRE

    Ben-Yehoyada, Merav; Wang, Lily C; Kozekov, Ivan D.; Rizzo, Carmelo J.; Gottesman, Max E.; Gautier, Jean

    2009-01-01

    DNA interstrand crosslinks (ICLs) are the most toxic lesions induced by chemotherapeutic agents such as Mitomycin C and Cisplatin. By covalently linking both DNA strands, ICLs prevent DNA melting, transcription, and replication. Studies on ICL signaling and repair have been limited because these drugs generate additional DNA lesions that trigger checkpoint signaling. Here, we monitor sensing, signaling from and repairing of a single, site-specific ICL in cell-free extract derived from Xenopus...

  17. Checkpointing for the RESTART problem in Markov networks

    OpenAIRE

    Lipsky, Lester; Doran, Derek; Gokhale, Swapna

    2011-01-01

    We apply the known formulae of the RESTART problem to Markov models of software (and many other) systems, and derive new equations. We show how checkpoints might be included, with their resultant performance under RESTART. The result is a complete procedure for finding the mean, variance, and tail behavior of the job completion time as a function of the failure rate. We also provide a detailed example.

  18. Protein kinase TTK interacts and co-localizes with CENP-E to the kinetochore of human cells

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Spindle checkpoint is an important biochemical signaling cascade during mitosis which monitors the fidelity of chromosome segregation, and is mediated by protein kinases Mps1 and Bub1/BubR1. Our recent studies show that kinesin-related motor protein CENP-E interacts with BubR1 and participates in spindle checkpoint signaling. To elucidate the molecular mechanisms underlying spindle checkpoint signaling, we carried out proteomic dissection of human cell kinetochore and revealed protein kinase TTK, human homologue of yeast Mps1. Our studies show that TTK is localized to the kinetochore of human cells, and interacts with CENP-E, suggesting that TTK may play an important role in chromosome segregation during mitosis.

  19. Potential biomarker for checkpoint blockade immunotherapy and treatment strategy.

    Science.gov (United States)

    Dong, Zhong-Yi; Wu, Si-Pei; Liao, Ri-Qiang; Huang, Shu-Mei; Wu, Yi-Long

    2016-04-01

    Programmed cell death protein-1 (PD-1) and ligand (PD-L1) provide an important escape mechanism from immune attack, and blockade therapy of these proteins show promising clinical benefits in many types of cancer. PD-L1 can be induced by interferon-gamma (IFN-γ), hypoxia, or toll-like receptor (TLR)-mediated pathways that confer adaptive immune resistance, or upregulated by oncogenic signals leading to constitutive expression and resulting in intrinsic immune resistance. The PD-1/PD-L1 checkpoint blockade, which targets regulatory pathways in T cells to overcome immune resistance, is correlated to PD-L1 expression pattern and the presence of tumor-infiltrating lymphocytes (TILs). Meanwhile, immunogenic mutation loads show significant response to checkpoint blockade, which is probably due to PD-1/L1 status and TIL content. Finally, the clinical strategies to design effective checkpoint-targeting immunotherapies are based on the classification of inducible/constitutive expression of PD-L1 and the presence of TILs. PMID:26779629

  20. Complex Commingling: Nucleoporins and the Spindle Assembly Checkpoint

    Directory of Open Access Journals (Sweden)

    Ikram Mossaid

    2015-11-01

    Full Text Available The segregation of the chromosomes during mitosis is an important process, in which the replicated DNA content is properly allocated into two daughter cells. To ensure their genomic integrity, cells present an essential surveillance mechanism known as the spindle assembly checkpoint (SAC, which monitors the bipolar attachment of the mitotic spindle to chromosomes to prevent errors that would result in chromosome mis-segregation and aneuploidy. Multiple components of the nuclear pore complex (NPC, a gigantic protein complex that forms a channel through the nuclear envelope to allow nucleocytoplasmic exchange of macromolecules, were shown to be critical for faithful cell division and implicated in the regulation of different steps of the mitotic process, including kinetochore and spindle assembly as well as the SAC. In this review, we will describe current knowledge about the interconnection between the NPC and the SAC in an evolutional perspective, which primarily relies on the two mitotic checkpoint regulators, Mad1 and Mad2. We will further discuss the role of NPC constituents, the nucleoporins, in kinetochore and spindle assembly and the formation of the mitotic checkpoint complex during mitosis and interphase.

  1. Learning common lessons and checkpoints form human error incidents. Maintenance

    International Nuclear Information System (INIS)

    CRIEPI has been conducting detailed and structured analyses of all human error incidents collected from Japanese Licensee Event Reports using J-HPES (Japanese version of HPES) as an analysis method. Results obtained by the analyses have been stored in J-HPES database. This paper described the process to analyze J-HPES data concerning maintenance systematically to extract problems identified in the process of error action and checkpoints for preventing errors. Human error actions of these J-HPES data are classified by viewpoints of error mode and work type. As to each of these error categories, problems are extracted based on J-HPES causal relation charts in following three viewpoints: acts at workplace, activities, and preconditions of job. Moreover, checkpoints for preventing errors are developed referring proposed countermeasures in J-HPES database. In order to share these results, we started to issue 4-pages booklets 'Catch the Point' periodically. In future, based on these results, we will publish a teaching material. We also have a plan to store the contents of Catch the Point in a database, which facilitate users to find necessary checkpoints and hazards before they start their activities. (author)

  2. Two S-phase checkpoint systems, one involving the function of both BIME and Tyr15 phosphorylation of p34cdc2, inhibit NIMA and prevent premature mitosis.

    OpenAIRE

    Ye, X S; Fincher, R R; Tang, A.; O'Donnell, K; Osmani, S A

    1996-01-01

    We demonstrate that there are at least two S-phase checkpoint mechanisms controlling mitosis in Aspergillus. The first responds to the rate of DNA replication and inhibits mitosis via tyrosine phosphorylation of p34cdc2. Cells unable to tyrosine phosphorylate p34cdc2 are therefore viable but are unable to tolerate low levels of hydroxyurea and prematurely enter lethal mitosis when S-phase is slowed. However, if the NIMA mitosis-promoting kinase is inactivated then non-tyrosine-phosphorylated ...

  3. ATM/ATR-related checkpoint signals mediate arsenite-induced G{sub 2}/M arrest in primary aortic endothelial cells

    Energy Technology Data Exchange (ETDEWEB)

    Tsou, Tsui-Chun; Tsai, Feng-Yuan; Yeh, Szu-Ching; Chang, Louis W. [National Health Research Institutes, Division of Environmental Health and Occupational Medicine, Miaoli County (Taiwan)

    2006-12-15

    Epidemiological studies have demonstrated a high association of inorganic arsenic exposure with vascular disease. Our recent in vitro studies have linked this vascular damage to vascular endothelial dysfunction induced by arsenic exposure. However, cell-cycle arrest induced by arsenic and its involvement in vascular dysfunction remain to be clarified. In this study, we employed primary porcine aortic endothelial cells to investigate regulatory mechanisms of G{sub 2}/M phase arrest induced by arsenite. Our study revealed that lower concentrations of arsenite (1 and 3 {mu}M) increased cell proliferation, whereas higher concentrations of arsenite (10, 20, and 30 {mu}M) inhibited cell proliferation together with correlated increases in G{sub 2}/M phase arrest. We found that this arsenite-induced G{sub 2}/M phase arrest was accompanied by accumulation and/or phosphorylation of checkpoint-related molecules, including p53, Cdc25B, Cdc25C, and securin. Inhibition of activations of these checkpoint-related molecules by caffeine significantly attenuated the 30-{mu}M arsenite-induced G{sub 2}/M phase arrest by 93%. Our data suggest that the DNA damage responsive kinases ATM (ataxia-telangiectasia mutated) and ATR (ATM and Rad3-related) play critical roles in arsenite-induced G{sub 2}/M phase arrest in aortic endothelial cells possibly via regulation of checkpoint-related signaling molecules including p53, Cdc25B, Cdc25C, and securin. (orig.)

  4. Cisplatin-Induced DNA Damage Activates Replication Checkpoint Signaling Components that Differentially Affect Tumor Cell SurvivalS⃞

    OpenAIRE

    Wagner, Jill M.; Karnitz, Larry M.

    2009-01-01

    Cisplatin and other platinating agents are some of the most widely used chemotherapy agents. These drugs exert their antiproliferative effects by creating intrastrand and interstrand DNA cross-links, which block DNA replication. The cross-links mobilize signaling and repair pathways, including the Rad9-Hus1-Rad1-ATR-Chk1 pathway, a pathway that helps tumor cells survive the DNA damage inflicted by many chemotherapy agents. Here we show that Rad9 and ATR play critical r...

  5. Emodnet Med Sea Check-Point - Indicators for decision- maker

    Science.gov (United States)

    Besnard, Sophie; Claverie, Vincent; Blanc, Frédérique

    2015-04-01

    The Emodnet Checkpoint projects aim is to assess the cost-effectiveness, reliability and utility of the existing monitoring at the sea basin level. This involves the development of monitoring system indicators and a GIS Platform to perform the assessment and make it available. Assessment or production of Check-Point information is made by developing targeted products based on the monitoring data and determining whether the products are meeting the needs of industry and public authorities. Check-point users are the research community, the 'institutional' policy makers for IMP and MSFD implementation, the 'intermediate users', i.e., users capable to understand basic raw data but that benefit from seeing the Checkpoint targeted products and the assessment of the fitness for purpose. We define assessment criteria aimed to characterize/depict the input datasets in terms of 3 territories capable to show performance and gaps of the present monitoring system, appropriateness, availability and fitness for purpose. • Appropriateness: What is made available to users? What motivate/decide them to select this observation rather than this one. • Availability: How this is made available to the user? Place to understand the readiness and service performance of the EU infrastructure • Fitness for use / fitness for purpose: Ability for non-expert user to appreciate the data exploitability (feedback on efficiency & reliability of marine data) For each territory (appropriateness, Availability and Fitness for purpose / for use), we define several indicators. For example, for Availability we define Visibility, Accessibility and Performance. And Visibility is itself defined by "Easily found" and "EU service". So these indicators can be classified according to their territory and sub-territory as seen above, but also according to the complexity to build them. Indicators are built from raw descriptors in 3 stages:  Stage 1: to give a neutral and basic status directly computed from

  6. Checkpoint Defects Leading to Premature Mitosis Also Cause Endoreplication of DNA in Aspergillus nidulans

    OpenAIRE

    De Souza, Colin P. C.; Ye, Xiang S.; Osmani, Stephen A.

    1999-01-01

    The G2 DNA damage and slowing of S-phase checkpoints over mitosis function through tyrosine phosphorylation of NIMXcdc2 in Aspergillus nidulans. We demonstrate that breaking these checkpoints leads to a defective premature mitosis followed by dramatic rereplication of genomic DNA. Two additional checkpoint functions, uvsB and uvsD, also cause the rereplication phenotype after their mutation allows premature mitosis in the presence of low concentrations of hydroxyurea. uvsB is shown to encode ...

  7. Assays Used to Study the DNA Replication Checkpoint in Fission Yeast

    OpenAIRE

    Noguchi, Eishi; Ansbach, Alison B.; Noguchi, Chiaki; Russell, Paul

    2009-01-01

    The DNA replication checkpoint, also known as the intra-S or S-phase checkpoint, plays a central role in ensuring the accuracy of DNA replication. When replication is impeded by DNA damage or other conditions, this checkpoint delays cell cycle progression and coordinates resumption of replication with DNA repair pathways. One of its critical functions is to stabilize stalled replication forks in a replication-competent state, presumably by maintaining proper assembly of replisome components a...

  8. Action-oriented use of ergonomic checkpoints for healthy work design in different settings.

    Science.gov (United States)

    Kogi, Kazutaka

    2007-12-01

    Recent experiences in the action-oriented use of ergonomic checkpoints in different work settings are reviewed. The purpose is to know what features are useful for healthy work design adjusted to each local situation. Based on the review results, common features of ergonomic checkpoints used in participatory training programs for improving workplace conditions in small enterprises, construction sites, home work and agriculture in industrially developing countries in Asia are discussed. These checkpoints generally compile practical improvement options in a broad range of technical areas, such as materials handling, workstation design, physical environment and work organization. Usually, "action checklists" comprising the tiles of the checkpoints are used together. A clear focus is placed on readily applicable low-cost options. Three common features of these various checkpoints appear to be important. First, the checkpoints represent typical good practices in multiple areas. Second, each how-to section of these checkpoints presents simple improvements reflecting basic ergonomic principles. Examples of these principles include easy reach, fewer and faster transport, elbow-level work, coded displays, isolated or screened hazards and shared teamwork. Third, the illustrated checkpoints accompanied by corresponding checklists are used as group work tools in short-term training courses. Many practical improvements achieved are displayed in websites for inter-country work improvement networks. It is suggested to promote the use of locally adjusted checkpoints in various forms of participatory action-oriented training in small-scale workplaces and in agriculture particularly in industrially developing countries. PMID:18572793

  9. The flavonoid eupatorin inactivates the mitotic checkpoint leading to polyploidy and apoptosis

    Energy Technology Data Exchange (ETDEWEB)

    Salmela, Anna-Leena [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Turku Graduate School of Biomedical Sciences, Turku (Finland); Turku Centre for Biotechnology, P.O. Box 123, University of Turku (Finland); Pouwels, Jeroen; Kukkonen-Macchi, Anu [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Waris, Sinikka; Toivonen, Pauliina [Turku Centre for Biotechnology, P.O. Box 123, University of Turku (Finland); Jaakkola, Kimmo [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Maeki-Jouppila, Jenni [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Turku Centre for Biotechnology, P.O. Box 123, University of Turku (Finland); Drug Discovery Graduate School, University of Turku (Finland); Kallio, Lila, E-mail: lila.kallio@vtt.fi [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Kallio, Marko J. [VTT Technical Research Centre of Finland, Medical Biotechnology, P.O. Box 106, Turku (Finland); Turku Centre for Biotechnology, P.O. Box 123, University of Turku (Finland); Centre of Excellence for Translational Genome-Scale Biology, P.O. Box 106, Academy of Finland (Finland)

    2012-03-10

    The spindle assembly checkpoint (SAC) is a conserved mechanism that ensures the fidelity of chromosome distribution in mitosis by preventing anaphase onset until the correct bipolar microtubule-kinetochore attachments are formed. Errors in SAC function may contribute to tumorigenesis by inducing numerical chromosome anomalies (aneuploidy). On the other hand, total disruption of SAC can lead to massive genomic imbalance followed by cell death, a phenomena that has therapeutic potency. We performed a cell-based high-throughput screen with a compound library of 2000 bioactives for novel SAC inhibitors and discovered a plant-derived phenolic compound eupatorin (3 Prime ,5-dihydroxy-4 Prime ,6,7-trimethoxyflavone) as an anti-mitotic flavonoid. The premature override of the microtubule drug-imposed mitotic arrest by eupatorin is dependent on microtubule-kinetochore attachments but not interkinetochore tension. Aurora B kinase activity, which is essential for maintenance of normal SAC signaling, is diminished by eupatorin in cells and in vitro providing a mechanistic explanation for the observed forced mitotic exit. Eupatorin likely has additional targets since eupatorin treatment of pre-mitotic cells causes spindle anomalies triggering a transient M phase delay followed by impaired cytokinesis and polyploidy. Finally, eupatorin potently induces apoptosis in multiple cancer cell lines and suppresses cancer cell proliferation in organotypic 3D cell culture model.

  10. The flavonoid eupatorin inactivates the mitotic checkpoint leading to polyploidy and apoptosis

    International Nuclear Information System (INIS)

    The spindle assembly checkpoint (SAC) is a conserved mechanism that ensures the fidelity of chromosome distribution in mitosis by preventing anaphase onset until the correct bipolar microtubule–kinetochore attachments are formed. Errors in SAC function may contribute to tumorigenesis by inducing numerical chromosome anomalies (aneuploidy). On the other hand, total disruption of SAC can lead to massive genomic imbalance followed by cell death, a phenomena that has therapeutic potency. We performed a cell-based high-throughput screen with a compound library of 2000 bioactives for novel SAC inhibitors and discovered a plant-derived phenolic compound eupatorin (3′,5-dihydroxy-4′,6,7-trimethoxyflavone) as an anti-mitotic flavonoid. The premature override of the microtubule drug-imposed mitotic arrest by eupatorin is dependent on microtubule–kinetochore attachments but not interkinetochore tension. Aurora B kinase activity, which is essential for maintenance of normal SAC signaling, is diminished by eupatorin in cells and in vitro providing a mechanistic explanation for the observed forced mitotic exit. Eupatorin likely has additional targets since eupatorin treatment of pre-mitotic cells causes spindle anomalies triggering a transient M phase delay followed by impaired cytokinesis and polyploidy. Finally, eupatorin potently induces apoptosis in multiple cancer cell lines and suppresses cancer cell proliferation in organotypic 3D cell culture model.

  11. The Spindle Assembly Checkpoint Safeguards Genomic Integrity of Skeletal Muscle Satellite Cells

    Directory of Open Access Journals (Sweden)

    Swapna Kollu

    2015-06-01

    Full Text Available To ensure accurate genomic segregation, cells evolved the spindle assembly checkpoint (SAC, whose role in adult stem cells remains unknown. Inducible perturbation of a SAC kinase, Mps1, and its downstream effector, Mad2, in skeletal muscle stem cells shows the SAC to be critical for normal muscle growth, repair, and self-renewal of the stem cell pool. SAC-deficient muscle stem cells arrest in G1 phase of the cell cycle with elevated aneuploidy, resisting differentiation even under inductive conditions. p21CIP1 is responsible for these SAC-deficient phenotypes. Despite aneuploidy’s correlation with aging, we find that aged proliferating muscle stem cells display robust SAC activity without elevated aneuploidy. Thus, muscle stem cells have a two-step mechanism to safeguard their genomic integrity. The SAC prevents chromosome missegregation and, if it fails, p21CIP1-dependent G1 arrest limits cellular propagation and tissue integration. These mechanisms ensure that muscle stem cells with compromised genomes do not contribute to tissue homeostasis.

  12. Casein kinases

    DEFF Research Database (Denmark)

    Issinger, O G

    1993-01-01

    subunits are highly conserved during evolution. The relationship between CK-2 alpha from humans and plants is still 73%. Similar relationships are reported for the beta-subunit. Chromosomal assignment of CK-2 alpha shows two gene loci, one of which is a pseudogene. They are located on different chromosomes...... genetic changes are necessarily involved; the observed changes may be entirely due to a signal transduction pathway where CK-2 could be phosphorylated by another kinase(s). CK-2 cDNAs from various organisms have been isolated and characterized. From the deduced amino acid sequence it turns out that CK-2...

  13. Centrosome-associated regulators of the G2/M checkpoint as targets for cancer therapy

    Directory of Open Access Journals (Sweden)

    Broaddus Russell R

    2009-02-01

    Full Text Available Abstract In eukaryotic cells, control mechanisms have developed that restrain cell-cycle transitions in response to stress. These regulatory pathways are termed cell-cycle checkpoints. The G2/M checkpoint prevents cells from entering mitosis when DNA is damaged in order to afford these cells an opportunity to repair the damaged DNA before propagating genetic defects to the daughter cells. If the damage is irreparable, checkpoint signaling might activate pathways that lead to apoptosis. Since alteration of cell-cycle control is a hallmark of tumorigenesis, cell-cycle regulators represent potential targets for therapy. The centrosome has recently come into focus as a critical cellular organelle that integrates G2/M checkpoint control and repairs signals in response to DNA damage. A growing number of G2/M checkpoint regulators have been found in the centrosome, suggesting that centrosome has an important role in G2/M checkpoint function. In this review, we discuss centrosome-associated regulators of the G2/M checkpoint, the dysregulation of this checkpoint in cancer, and potential candidate targets for cancer therapy.

  14. Twitter as a Tool to Warn Others about Sobriety Checkpoints: A Pilot Observational Study

    Science.gov (United States)

    Seitz, Christopher M.; Orsini, Muhsin Michael; Fearnow-Kenney, Melodie; Hatzudis, Kiki; Wyrick, David L.

    2012-01-01

    Anecdotal evidence suggests that young people use the website Twitter as a tool to warn drivers about the locations of sobriety checkpoints. Researchers investigated this claim by independently analyzing the website's content regarding a sample of 10 sobriety checkpoints that were conducted in cities throughout the United States during the weekend…

  15. Cdc20 and Cks direct the spindle checkpoint-independent destruction of cyclin A

    NARCIS (Netherlands)

    Wolthuis, Rob; Clay-Farrace, Lori; van Zon, Wouter; Yekezare, Mona; Koop, Lars; Ogink, Janneke; Medema, Rene; Pines, Jonathon

    2008-01-01

    Successful mitosis requires the right protein be degraded at the right time. Central to this is the spindle checkpoint that prevents the destruction of securin and cyclin 131 when there are improperly attached chromosomes. The principal target of the checkpoint is Cdc20, which activates the anaphase

  16. Space Reclamation for Uncoordinated Checkpointing in Message-Passing Systems. Ph.D. Thesis

    Science.gov (United States)

    Wang, Yi-Min

    1993-01-01

    Checkpointing and rollback recovery are techniques that can provide efficient recovery from transient process failures. In a message-passing system, the rollback of a message sender may cause the rollback of the corresponding receiver, and the system needs to roll back to a consistent set of checkpoints called recovery line. If the processes are allowed to take uncoordinated checkpoints, the above rollback propagation may result in the domino effect which prevents recovery line progression. Traditionally, only obsolete checkpoints before the global recovery line can be discarded, and the necessary and sufficient condition for identifying all garbage checkpoints has remained an open problem. A necessary and sufficient condition for achieving optimal garbage collection is derived and it is proved that the number of useful checkpoints is bounded by N(N+1)/2, where N is the number of processes. The approach is based on the maximum-sized antichain model of consistent global checkpoints and the technique of recovery line transformation and decomposition. It is also shown that, for systems requiring message logging to record in-transit messages, the same approach can be used to achieve optimal message log reclamation. As a final topic, a unifying framework is described by considering checkpoint coordination and exploiting piecewise determinism as mechanisms for bounding rollback propagation, and the applicability of the optimal garbage collection algorithm to domino-free recovery protocols is demonstrated.

  17. Cyclin F suppresses B-Myb activity to promote cell cycle checkpoint control

    DEFF Research Database (Denmark)

    Klein, Ditte Kjærsgaard; Hoffmann, Saskia; Ahlskog, Johanna K;

    2015-01-01

    an important role in checkpoint control following ionizing radiation. Cyclin F-depleted cells initiate checkpoint signalling after ionizing radiation, but fail to maintain G2 phase arrest and progress into mitosis prematurely. Importantly, cyclin F suppresses the B-Myb-driven transcriptional programme...

  18. Priming the pancreatic cancer tumor microenvironment for checkpoint-inhibitor immunotherapy

    OpenAIRE

    Lutz, Eric R.; Kinkead, Heather; Jaffee, Elizabeth M.; Zheng, Lei

    2014-01-01

    Single agent immunotherapy is effective against several cancers, but has failed against poorly immunogenic cancers, including pancreatic cancer. Evaluation of pancreatic tumors following treatment with an experimental vaccine (Lutz et al. Cancer Immunology Research 2014) suggests that vaccination primes the tumor microenvironment (TME) for checkpoint-inhibitor immunotherapy, and supports a new platform for evaluating checkpoint-inhibitors in poorly immunogenic cancers.

  19. Cenp-meta is required for sustained spindle checkpoint

    Directory of Open Access Journals (Sweden)

    Thomas Rubin

    2014-05-01

    Full Text Available Cenp-E is a kinesin-like motor protein required for efficient end-on attachment of kinetochores to the spindle microtubules. Cenp-E immunodepletion in Xenopus mitotic extracts results in the loss of mitotic arrest and massive chromosome missegregation, whereas its depletion in mammalian cells leads to chromosome segregation defects despite the presence of a functional spindle assembly checkpoint (SAC. Cenp-meta has previously been reported to be the Drosophila homolog of vertebrate Cenp-E. In this study, we show that cenp-metaΔ mutant neuroblasts arrest in mitosis when treated with colchicine. cenp-metaΔ mutant cells display a mitotic delay. Yet, despite the persistence of the two checkpoint proteins Mad2 and BubR1 on unattached kinetochores, these cells eventually enter anaphase and give rise to highly aneuploid daughter cells. Indeed, we find that cenp-metaΔ mutant cells display a slow but continuous degradation of cyclin B, which eventually triggers the mitotic exit observed. Thus, our data provide evidence for a role of Cenp-meta in sustaining the SAC response.

  20. Detailed Modeling, Design, and Evaluation of a Scalable Multi-level Checkpointing System

    Energy Technology Data Exchange (ETDEWEB)

    Moody, A T; Bronevetsky, G; Mohror, K M; de Supinski, B R

    2010-04-09

    High-performance computing (HPC) systems are growing more powerful by utilizing more hardware components. As the system mean-time-before-failure correspondingly drops, applications must checkpoint more frequently to make progress. However, as the system memory sizes grow faster than the bandwidth to the parallel file system, the cost of checkpointing begins to dominate application run times. A potential solution to this problem is to use multi-level checkpointing, which employs multiple types of checkpoints with different costs and different levels of resiliency in a single run. The goal is to design light-weight checkpoints to handle the most common failure modes and rely on more expensive checkpoints for less common, but more severe failures. While this approach is theoretically promising, it has not been fully evaluated in a large-scale, production system context. To this end we have designed a system, called the Scalable Checkpoint/Restart (SCR) library, that writes checkpoints to storage on the compute nodes utilizing RAM, Flash, or disk, in addition to the parallel file system. We present the performance and reliability properties of SCR as well as a probabilistic Markov model that predicts its performance on current and future systems. We show that multi-level checkpointing improves efficiency on existing large-scale systems and that this benefit increases as the system size grows. In particular, we developed low-cost checkpoint schemes that are 100x-1000x faster than the parallel file system and effective against 85% of our system failures. This leads to a gain in machine efficiency of up to 35%, and it reduces the the load on the parallel file system by a factor of two on current and future systems.

  1. Parallelization and checkpointing of GPU applications through program transformation

    Energy Technology Data Exchange (ETDEWEB)

    Solano-Quinde, Lizandro Damian [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    GPUs have emerged as a powerful tool for accelerating general-purpose applications. The availability of programming languages that makes writing general-purpose applications for running on GPUs tractable have consolidated GPUs as an alternative for accelerating general purpose applications. Among the areas that have benefited from GPU acceleration are: signal and image processing, computational fluid dynamics, quantum chemistry, and, in general, the High Performance Computing (HPC) Industry. In order to continue to exploit higher levels of parallelism with GPUs, multi-GPU systems are gaining popularity. In this context, single-GPU applications are parallelized for running in multi-GPU systems. Furthermore, multi-GPU systems help to solve the GPU memory limitation for applications with large application memory footprint. Parallelizing single-GPU applications has been approached by libraries that distribute the workload at runtime, however, they impose execution overhead and are not portable. On the other hand, on traditional CPU systems, parallelization has been approached through application transformation at pre-compile time, which enhances the application to distribute the workload at application level and does not have the issues of library-based approaches. Hence, a parallelization scheme for GPU systems based on application transformation is needed. Like any computing engine of today, reliability is also a concern in GPUs. GPUs are vulnerable to transient and permanent failures. Current checkpoint/restart techniques are not suitable for systems with GPUs. Checkpointing for GPU systems present new and interesting challenges, primarily due to the natural differences imposed by the hardware design, the memory subsystem architecture, the massive number of threads, and the limited amount of synchronization among threads. Therefore, a checkpoint/restart technique suitable for GPU systems is needed. The goal of this work is to exploit higher levels of parallelism and

  2. Activation of a DNA damage checkpoint response in a TAF1-defective cell line.

    Science.gov (United States)

    Buchmann, Ann M; Skaar, Jeffrey R; DeCaprio, James A

    2004-06-01

    Although the link between transcription and DNA repair is well established, defects in the core transcriptional complex itself have not been shown to elicit a DNA damage response. Here we show that a cell line with a temperature-sensitive defect in TBP-associated factor 1 (TAF1), a component of the TFIID general transcription complex, exhibits hallmarks of an ATR-mediated DNA damage response. Upon inactivation of TAF1, ATR rapidly localized to subnuclear foci and contributed to the phosphorylation of several downstream targets, including p53 and Chk1, resulting in cell cycle arrest. The increase in p53 expression and the G(1) phase arrest could be blocked by caffeine, an inhibitor of ATR. In addition, dominant negative forms of ATR but not ATM were able to override the arrest in G(1). These results suggest that a defect in TAF1 can elicit a DNA damage response. PMID:15169897

  3. Mechanism-based screen for G1/S checkpoint activators identifies a selective activator of EIF2AK3/PERK signalling.

    Directory of Open Access Journals (Sweden)

    Simon R Stockwell

    Full Text Available Human cancers often contain genetic alterations that disable G1/S checkpoint control and loss of this checkpoint is thought to critically contribute to cancer generation by permitting inappropriate proliferation and distorting fate-driven cell cycle exit. The identification of cell permeable small molecules that activate the G1/S checkpoint may therefore represent a broadly applicable and clinically effective strategy for the treatment of cancer. Here we describe the identification of several novel small molecules that trigger G1/S checkpoint activation and characterise the mechanism of action for one, CCT020312, in detail. Transcriptional profiling by cDNA microarray combined with reverse genetics revealed phosphorylation of the eukaryotic initiation factor 2-alpha (EIF2A through the eukaryotic translation initiation factor 2-alpha kinase 3 (EIF2AK3/PERK as the mechanism of action of this compound. While EIF2AK3/PERK activation classically follows endoplasmic reticulum (ER stress signalling that sets off a range of different cellular responses, CCT020312 does not trigger these other cellular responses but instead selectively elicits EIF2AK3/PERK signalling. Phosphorylation of EIF2A by EIF2A kinases is a known means to block protein translation and hence restriction point transit in G1, but further supports apoptosis in specific contexts. Significantly, EIF2AK3/PERK signalling has previously been linked to the resistance of cancer cells to multiple anticancer chemotherapeutic agents, including drugs that target the ubiquitin/proteasome pathway and taxanes. Consistent with such findings CCT020312 sensitizes cancer cells with defective taxane-induced EIF2A phosphorylation to paclitaxel treatment. Our work therefore identifies CCT020312 as a novel small molecule chemical tool for the selective activation of EIF2A-mediated translation control with utility for proof-of-concept applications in EIF2A-centered therapeutic approaches, and as a chemical

  4. The budding yeast Ipl1/Aurora protein kinase regulates mitotic spindle disassembly

    OpenAIRE

    Buvelot, Stéphanie; Tatsutani, Sean Y.; Vermaak, Danielle; Biggins, Sue

    2003-01-01

    Ipl1p is the budding yeast member of the Aurora family of protein kinases, critical regulators of genomic stability that are required for chromosome segregation, the spindle checkpoint, and cytokinesis. Using time-lapse microscopy, we found that Ipl1p also has a function in mitotic spindle disassembly that is separable from its previously identified roles. Ipl1–GFP localizes to kinetochores from G1 to metaphase, transfers to the spindle after metaphase, and accumulates at the spindle midzone ...

  5. Fueling the engine and releasing the break:combinational therapy of cancer vaccines and immune checkpoint inhibitors

    Institute of Scientific and Technical Information of China (English)

    Jennifer Kleponis; Richard Skelton; Lei Zheng

    2015-01-01

    Immune checkpoint inhibitors are increasingly drawing much attention in the therapeutic development for cancer treatment. However, many cancer patients do not respond to treatments with immune checkpoint inhibitors, partly because of the lack of tumor-inifltrating effector T cells. Cancer vaccines may prime patients for treatments with immune checkpoint inhibitors by inducing effector T-cell infiltration into the tumors and immune checkpoint signals. The combination of cancer vaccine and an immune checkpoint inhibitor may function synergistically to induce more effective antitumor immune responses, and clinical trials to test the combination are currently ongoing.

  6. Optimization of luminescent assay for screening of cyclin-dependent kinase 2 inhibitors

    Directory of Open Access Journals (Sweden)

    Suthar M

    2010-01-01

    Full Text Available Cyclin-dependent kinases are most extensively studied targets for cancer chemotherapy since the tumor cells exhibit false checkpoints and can proliferate even if the genome is compromised. Cyclin-dependent kinases ensure the tight regulation of the cell cycle execution by mediating phosphorylation of cellular proteins. Deregulation of the cyclin-dependent kinase 2 activity by cellular and external factors leads to many diseases like cancers. Different methods like radiolabeled, fluorescence and luminescence are available for screening of library of compounds against kinases. However, bioluminescent methods offer several advantages like low background and no effect of fluorescent compound interference. Present study is focused on development, optimization and validation of cyclin-dependent kinase 2 assay which is suitable for identification potent and selective, ATP competitive and non-competitive inhibitors of cyclin-dependent kinase 2. The aim of present investigation was to optimize the assay for cyclin-dependent kinase 2/cylin A and cyclin-dependent kinase 2/cyclin E with use of bioluminescence based biochemical reaction. Both cyclin-dependent kinase 2 which are cyclin-dependent kinase 2/cyclin A and cyclin-dependent kinase 2/cyclin E complexes, have different affinity for ATP. Therefore, both isoform analogs of cyclin-dependent kinase 2 were optimized separately. Optimum cyclin-dependent kinase 2/cyclin A and cyclin-dependent kinase 2/cyclin E concentration were found to be 250 ng/well and 200 ng/well, respectively. Optimum substrate (histone H1 concentration was found to be 2.5 mg/ml for both cyclin-dependent kinase 2 analogs. Optimum reaction time was found to be 20 min for both cyclin-dependent kinase 2/cyclin complexes.

  7. Spindle assembly checkpoint protein expression correlates with cellular proliferation and shorter time to recurrence in ovarian cancer.

    LENUS (Irish Health Repository)

    McGrogan, Barbara

    2014-07-01

    Ovarian carcinoma (OC) is the most lethal of the gynecological malignancies, often presenting at an advanced stage. Treatment is hampered by high levels of drug resistance. The taxanes are microtubule stabilizing agents, used as first-line agents in the treatment of OC that exert their apoptotic effects through the spindle assembly checkpoint. BUB1-related protein kinase (BUBR1) and mitotic arrest deficient 2 (MAD2), essential spindle assembly checkpoint components, play a key role in response to taxanes. BUBR1, MAD2, and Ki-67 were assessed on an OC tissue microarray platform representing 72 OC tumors of varying histologic subtypes. Sixty-one of these patients received paclitaxel and platinum agents combined; 11 received platinum alone. Overall survival was available for all 72 patients, whereas recurrence-free survival (RFS) was available for 66 patients. Increased BUBR1 expression was seen in serous carcinomas, compared with other histologies (P = .03). Increased BUBR1 was significantly associated with tumors of advanced stage (P = .05). Increased MAD2 and BUBR1 expression also correlated with increased cellular proliferation (P < .0002 and P = .02, respectively). Reduced MAD2 nuclear intensity was associated with a shorter RFS (P = .03), in ovarian tumors of differing histologic subtype (n = 66). In this subgroup, for those women who received paclitaxel and platinum agents combined (n = 57), reduced MAD2 intensity also identified women with a shorter RFS (P < .007). For the entire cohort of patients, irrespective of histologic subtype or treatment, MAD2 nuclear intensity retained independent significance in a multivariate model, with tumors showing reduced nuclear MAD2 intensity identifying patients with a poorer RFS (P = .05).

  8. A novel role for the GTPase-activating protein Bud2 in the spindle position checkpoint.

    Directory of Open Access Journals (Sweden)

    Scott A Nelson

    Full Text Available The spindle position checkpoint (SPC ensures correct mitotic spindle position before allowing mitotic exit in the budding yeast Saccharomyces cerevisiae. In a candidate screen for checkpoint genes, we identified bud2Δ as deficient for the SPC. Bud2 is a GTPase activating protein (GAP, and the only known substrate of Bud2 was Rsr1/Bud1, a Ras-like GTPase and a central component of the bud-site-selection pathway. Mutants lacking Rsr1/Bud1 had no checkpoint defect, as did strains lacking and overexpressing Bud5, a guanine-nucleotide exchange factor (GEF for Rsr1/Bud1. Thus, the checkpoint function of Bud2 is distinct from its role in bud site selection. The catalytic activity of the Bud2 GAP domain was required for the checkpoint, based on the failure of the known catalytic point mutant Bud2(R682A to function in the checkpoint. Based on assays of heterozygous diploids, bud2(R682A, was dominant for loss of checkpoint but recessive for bud-site-selection failure, further indicating a separation of function. Tem1 is a Ras-like protein and is the critical regulator of mitotic exit, sitting atop the mitotic exit network (MEN. Tem1 is a likely target for Bud2, supported by genetic analyses that exclude other Ras-like proteins.

  9. Probabilistic Checkpointing Protocol to Sensor Network Fault-Tolerant

    Directory of Open Access Journals (Sweden)

    Titouna Faiza

    2012-09-01

    Full Text Available A wireless sensor network WSN is a collection of autonomous sensors nodes organized into a cooperative network. A sensor node transmits the data quantity to the sink. Indeed, a failed sink may abort the overall mission of the network. Due to their crucial functions, sinks must be designed and maintained to be robust enough in order to face trouble coming from the harsh environment. Thus, as a keystone of a WSN, a sink has to be provided with ability to recover from failures. In this paper, we propose a new protocol avoiding to the sink to be a central point of failure. First, we model a sensor node failure estimation problem through a causal network. Then, we show how the checkpointing process ensures the recovery of the network. This approach reduces both energy consumption and communication bandwidth requirements, and prolongs the lifetime of WSN. Interesting results are given by simulation

  10. EMODnet MedSea Checkpoint for sustainable Blue Growth

    Science.gov (United States)

    Moussat, Eric; Pinardi, Nadia; Manzella, Giuseppe; Blanc, Frederique

    2016-04-01

    The EMODNET checkpoint is a wide monitoring system assessment activity aiming to support the sustainable Blue Growth at the scale of the European Sea Basins by: 1) Clarifying the observation landscape of all compartments of the marine environment including Air, Water, Seabed, Biota and Human activities, pointing out to the existing programs, national, European and international 2) Evaluating fitness for use indicators that will show the accessibility and usability of observation and modeling data sets and their roles and synergies based upon selected applications by the European Marine Environment Strategy 3) Prioritizing the needs to optimize the overall monitoring Infrastructure (in situ and satellite data collection and assembling, data management and networking, modeling and forecasting, geo-infrastructure) and release recommendations for evolutions to better meet the application requirements in view of sustainable Blue Growth The assessment is designed for : - Institutional stakeholders for decision making on observation and monitoring systems - Data providers and producers to know how their data collected once for a given purpose could fit other user needs - End-users interested in a regional status and possible uses of existing monitoring data Selected end-user applications are of paramount importance for: (i) the blue economy sector (offshore industries, fisheries); (ii) marine environment variability and change (eutrophication, river inputs and ocean climate change impacts); (iii) emergency management (oil spills); and (iv) preservation of natural resources and biodiversity (Marine Protected Areas). End-user applications generate innovative products based on the existing observation landscape. The fitness for use assessment is made thanks to the comparison of the expected product specifications with the quality of the product derived from the selected data. This involves the development of checkpoint information and indicators based on Data quality and

  11. Attachment issues: kinetochore transformations and spindle checkpoint silencing.

    Science.gov (United States)

    Etemad, Banafsheh; Kops, Geert J P L

    2016-04-01

    Cell division culminates in the segregation of duplicated chromosomes in opposite directions prior to cellular fission. This process is guarded by the spindle assembly checkpoint (SAC), which prevents the anaphase of cell division until stable connections between spindle microtubules and the kinetochores of all chromosomes are established. The anaphase inhibitor is generated at unattached kinetochores and inhibitor production is prevented when microtubules are captured. Understanding the molecular changes in the kinetochore that are evoked by microtubule attachments is crucial for understanding the mechanisms of SAC signaling and silencing. Here, we highlight the most recent findings on these events, pinpoint some remaining mysteries, and argue for incorporating holistic views of kinetochore dynamics in order to understand SAC silencing. PMID:26947988

  12. Checkpoint inhibition for colorectal cancer: progress and possibilities.

    Science.gov (United States)

    Paul, Barry; O'Neil, Bert H; McRee, Autumn J

    2016-06-01

    Colorectal cancer (CRC) remains the third most common cause of cancer death in the USA. Despite an increase in the repertoire of treatment options available for CRC, median overall survival has plateaued at approximately 2.5 years. Strategies that engage the patient's native immune system to overcome checkpoint inhibition have proven to be promising in subsets of CRCs, specifically those with mismatch repair deficiency. Further studies are required to determine combinations of standard therapies with immunotherapy drugs and to discover the best biomarkers to predict response. This review provides insight into the progress made in treating patients with advanced CRC with immunotherapeutics and the areas that demand further research to make these drugs more effective in this patient population. PMID:27197538

  13. Checkpoint Blockade in Cancer Immunotherapy: Squaring the Circle

    Directory of Open Access Journals (Sweden)

    Maria A.V. Marzolini

    2015-03-01

    Full Text Available Manipulating the complex interaction between the immune system and tumour cells has been the focus of cancer research for many years, but it is only in the past decade that significant progress has been made in the field of cancer immunotherapy resulting in clinically effective treatments. The blockade of co-inhibitory immune checkpoints, essential for maintaining lymphocyte homeostasis and self-tolerance, by immunomodulatory monoclonal antibodies has resulted in the augmentation of anti-tumour responses. The greatest successes so far have been seen with the blockade of cytotoxic T lymphocyte associated antigen-4, which has resulted in the first Phase III clinical trial showing an overall survival benefit in metastatic melanoma, and in the blockade of the programmed cell death protein-1 axis. This concise review will focus on the clinical advances made by the blockade of these two pathways and their role in current cancer treatment strategies.

  14. A mitotic phosphorylation feedback network connects Cdk1, Plk1, 53BP1, and Chk2 to inactivate the G(2)/M DNA damage checkpoint

    DEFF Research Database (Denmark)

    van Vugt, Marcel A T M; Gardino, Alexandra K; Linding, Rune; Ostheimer, Gerard J; Reinhardt, H Christian; Ong, Shao-En; Tan, Chris S; Miao, Hua; Keezer, Susan M; Li, Jeijin; Pawson, Tony; Lewis, Timothy A; Carr, Steven A; Smerdon, Stephen J; Brummelkamp, Thijn R; Yaffe, Michael B

    2010-01-01

    DNA damage checkpoints arrest cell cycle progression to facilitate DNA repair. The ability to survive genotoxic insults depends not only on the initiation of cell cycle checkpoints but also on checkpoint maintenance. While activation of DNA damage checkpoints has been studied extensively, molecular...

  15. Defining the optimal murine models to investigate immune checkpoint blockers and their combination with other immunotherapies.

    Science.gov (United States)

    Sanmamed, M F; Chester, C; Melero, I; Kohrt, H

    2016-07-01

    The recent success of checkpoint blockers to treat cancer has demonstrated that the immune system is a critical player in the war against cancer. Historically, anticancer therapeutics have been tested in syngeneic mouse models (with a fully murine immune system) or in immunodeficient mice that allow the engraftment of human xenografts. Animal models with functioning human immune systems are critically needed to more accurately recapitulate the complexity of the human tumor microenvironment. Such models are integral to better predict tumor responses to both immunomodulatory agents and directly antineoplastic therapies. In this regard, the development of humanized models is a promising, novel strategy that offers the possibility of testing checkpoint blockers' capacity and their combination with other antitumor drugs. In this review, we discuss the strengths and weaknesses of the available animal models regarding their capacity to evaluate checkpoint blockers and checkpoint blocker-based combination immunotherapy. PMID:26912558

  16. Coupling end resection with the checkpoint response at DNA double-strand breaks.

    Science.gov (United States)

    Villa, Matteo; Cassani, Corinne; Gobbini, Elisa; Bonetti, Diego; Longhese, Maria Pia

    2016-10-01

    DNA double-strand breaks (DSBs) are a nasty form of damage that needs to be repaired to ensure genome stability. The DSB ends can undergo a strand-biased nucleolytic processing (resection) to generate 3'-ended single-stranded DNA (ssDNA) that channels DSB repair into homologous recombination. Generation of ssDNA also triggers the activation of the DNA damage checkpoint, which couples cell cycle progression with DSB repair. The checkpoint response is intimately linked to DSB resection, as some checkpoint proteins regulate the resection process. The present review will highlight recent works on the mechanism and regulation of DSB resection and its interplays with checkpoint activation/inactivation in budding yeast. PMID:27141941

  17. Cambridge checkpoint English revision guide for the Cambridge secondary 1 test

    CERN Document Server

    Reynolds, John

    2013-01-01

    With Checkpoint English Revision Guide for the Cambridge Secondary 1 test you can aim for the best grade with the help of relevant and accessible notes, examiner advice plus questions and answers on each key topic. - Clear explanations of every topic covered in the Cambridge Secondary 1 Checkpoint English syllabus. - Builds revision skills you need for success in the test. - Exam tips wirtten by test setters and examiners giving you their expert advice. This text has not been through the Cambridge endorsement process.

  18. Cambridge checkpoint maths revision guide for the Cambridge secondary 1 test

    CERN Document Server

    Smith, Alan

    2013-01-01

    With Checkpoint Maths Revision Guide for the Cambridge Secondary 1 test you can aim for the best grade with the help of relevant and accessible notes, examiner advice plus questions and answers on each key topic. - Clear explanations of every topic covered in the Cambridge Secondary 1 Checkpoint Maths syllabus. - Builds revision skills you need for success in the test. - Exam tips wirtten by test setters and examiners giving you their expert advice. This text has not been through the Cambridge endorsement process.

  19. The pachytene checkpoint prevents accumulation and phosphorylation of the meiosis-specific transcription factor Ndt80

    OpenAIRE

    Tung, Kuei-Shu; Hong, Eun-Jin Erica; Roeder, G. Shirleen

    2000-01-01

    In budding yeast, many mutants defective in meiotic recombination and chromosome synapsis undergo checkpoint-mediated arrest at the pachytene stage of meiotic prophase. We recovered the NDT80 gene in a screen for genes whose overexpression bypasses the pachytene checkpoint. Ndt80 is a meiosis-specific transcription factor that promotes expression of genes required for exit from pachytene and entry into meiosis I. Herein, we show that the Ndt80 protein accumulates a...

  20. A role for Ddc1 in signaling meiotic double-strand breaks at the pachytene checkpoint

    OpenAIRE

    Hong, Eun-Jin Erica; Roeder, G. Shirleen

    2002-01-01

    The pachytene checkpoint prevents meiotic cell cycle progression in response to unrepaired recombination intermediates. We show that Ddc1 is required for the pachytene checkpoint in Saccharomyces cerevisiae. During meiotic prophase, Ddc1 localizes to chromosomes and becomes phosphorylated; these events depend on the formation and processing of double-strand breaks (DSBs). Ddc1 colocalizes with Rad51, a DSB-repair protein, indicating that Ddc1 associates with sites of DSB repair. The Rad24 che...

  1. A Minimum-Process Coordinated Checkpointing Protocol For Mobile Distributed System

    Directory of Open Access Journals (Sweden)

    Praveen Kumar

    2010-05-01

    Full Text Available While dealing with Mobile Distributed systems, we come across some issues like: mobility, low bandwidth of wireless channels and lack of stable storage on mobile nodes, disconnections, limited battery power and high failure rate of mobile nodes. These issues make traditional checkpointing techniques designed for Distributed systems unsuitable for Mobile environments. In this paper, we design a minimum process algorithm for Mobile Distributed systems, where no useless checkpoints are taken and an effort has been made to optimize the blocking of processes. We propose to delay the processing of selective messages at the receiver end only during the checkpointing period. A Process is allowed to perform its normal computations and send messages during its blocking period. In this way, we try to keep blocking of processes to bare minimum. We captured the transitive dependencies during the normal execution by piggybacking dependency vectors onto computational messages. In this way, we try to reduce the Checkpointing time by avoiding formation of Checkpointing tree. The Z-dependencies are well taken care of. The proposed scheme forces zero useless checkpoints at the cost of very small blocking.

  2. RAG-mediated DNA double-strand breaks activate a cell type-specific checkpoint to inhibit pre-B cell receptor signals.

    Science.gov (United States)

    Bednarski, Jeffrey J; Pandey, Ruchi; Schulte, Emily; White, Lynn S; Chen, Bo-Ruei; Sandoval, Gabriel J; Kohyama, Masako; Haldar, Malay; Nickless, Andrew; Trott, Amanda; Cheng, Genhong; Murphy, Kenneth M; Bassing, Craig H; Payton, Jacqueline E; Sleckman, Barry P

    2016-02-01

    DNA double-strand breaks (DSBs) activate a canonical DNA damage response, including highly conserved cell cycle checkpoint pathways that prevent cells with DSBs from progressing through the cell cycle. In developing B cells, pre-B cell receptor (pre-BCR) signals initiate immunoglobulin light (Igl) chain gene assembly, leading to RAG-mediated DNA DSBs. The pre-BCR also promotes cell cycle entry, which could cause aberrant DSB repair and genome instability in pre-B cells. Here, we show that RAG DSBs inhibit pre-BCR signals through the ATM- and NF-κB2-dependent induction of SPIC, a hematopoietic-specific transcriptional repressor. SPIC inhibits expression of the SYK tyrosine kinase and BLNK adaptor, resulting in suppression of pre-BCR signaling. This regulatory circuit prevents the pre-BCR from inducing additional Igl chain gene rearrangements and driving pre-B cells with RAG DSBs into cycle. We propose that pre-B cells toggle between pre-BCR signals and a RAG DSB-dependent checkpoint to maintain genome stability while iteratively assembling Igl chain genes. PMID:26834154

  3. Molecular Imaging of the ATM Kinase Activity

    International Nuclear Information System (INIS)

    Purpose: Ataxia telangiectasia mutated (ATM) is a serine/threonine kinase critical to the cellular DNA-damage response, including from DNA double-strand breaks. ATM activation results in the initiation of a complex cascade of events including DNA damage repair, cell cycle checkpoint control, and survival. We sought to create a bioluminescent reporter that dynamically and noninvasively measures ATM kinase activity in living cells and subjects. Methods and Materials: Using the split luciferase technology, we constructed a hybrid cDNA, ATM-reporter (ATMR), coding for a protein that quantitatively reports on changes in ATM kinase activity through changes in bioluminescence. Results: Treatment of ATMR-expressing cells with ATM inhibitors resulted in a dose-dependent increase in bioluminescence activity. In contrast, induction of ATM kinase activity upon irradiation resulted in a decrease in reporter activity that correlated with ATM and Chk2 activation by immunoblotting in a time-dependent fashion. Nuclear targeting improved ATMR sensitivity to both ATM inhibitors and radiation, whereas a mutant ATMR (lacking the target phosphorylation site) displayed a muted response. Treatment with ATM inhibitors and small interfering (si)RNA-targeted knockdown of ATM confirm the specificity of the reporter. Using reporter expressing xenografted tumors demonstrated the ability of ATMR to report in ATM activity in mouse models that correlated in a time-dependent fashion with changes in Chk2 activity. Conclusions: We describe the development and validation of a novel, specific, noninvasive bioluminescent reporter that enables monitoring of ATM activity in real time, in vitro and in vivo. Potential applications of this reporter include the identification and development of novel ATM inhibitors or ATM-interacting partners through high-throughput screens and in vivo pharmacokinetic/pharmacodynamic studies of ATM inhibitors in preclinical models

  4. Molecular Imaging of the ATM Kinase Activity

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Terence M. [Department of Radiation Oncology, Ohio State University, Columbus, Ohio (United States); Nyati, Shyam [Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Center for Molecular Imaging, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Ross, Brian D. [Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Department of Radiology, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Rehemtulla, Alnawaz, E-mail: alnawaz@umich.edu [Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Center for Molecular Imaging, University of Michigan Medical Center, Ann Arbor, Michigan (United States); Department of Radiology, University of Michigan Medical Center, Ann Arbor, Michigan (United States)

    2013-08-01

    Purpose: Ataxia telangiectasia mutated (ATM) is a serine/threonine kinase critical to the cellular DNA-damage response, including from DNA double-strand breaks. ATM activation results in the initiation of a complex cascade of events including DNA damage repair, cell cycle checkpoint control, and survival. We sought to create a bioluminescent reporter that dynamically and noninvasively measures ATM kinase activity in living cells and subjects. Methods and Materials: Using the split luciferase technology, we constructed a hybrid cDNA, ATM-reporter (ATMR), coding for a protein that quantitatively reports on changes in ATM kinase activity through changes in bioluminescence. Results: Treatment of ATMR-expressing cells with ATM inhibitors resulted in a dose-dependent increase in bioluminescence activity. In contrast, induction of ATM kinase activity upon irradiation resulted in a decrease in reporter activity that correlated with ATM and Chk2 activation by immunoblotting in a time-dependent fashion. Nuclear targeting improved ATMR sensitivity to both ATM inhibitors and radiation, whereas a mutant ATMR (lacking the target phosphorylation site) displayed a muted response. Treatment with ATM inhibitors and small interfering (si)RNA-targeted knockdown of ATM confirm the specificity of the reporter. Using reporter expressing xenografted tumors demonstrated the ability of ATMR to report in ATM activity in mouse models that correlated in a time-dependent fashion with changes in Chk2 activity. Conclusions: We describe the development and validation of a novel, specific, noninvasive bioluminescent reporter that enables monitoring of ATM activity in real time, in vitro and in vivo. Potential applications of this reporter include the identification and development of novel ATM inhibitors or ATM-interacting partners through high-throughput screens and in vivo pharmacokinetic/pharmacodynamic studies of ATM inhibitors in preclinical models.

  5. A Cdc2 dependent checkpoint maintains diploidy in Drosophila.

    Science.gov (United States)

    Hayashi, S

    1996-04-01

    DNA replication in G2 does not normally occur due to the checkpoint control. To elucidate its mechanism, the functions of the escargot and Dmcdc2 genes of Drosophila were studied. When escargot function was eliminated, diploid imaginal cells that were arrested in G2 lost Cyclin A, a regulatory subunit of G2/M cdk, and entered an endocycle. escargot genetically interacted with Dmcdc2 which encodes a catalytic subunit of G2/M cdk. The mutant phenotypes of Dmcdc2 itself was similar to those of escargot: many diploid cells in imaginal discs, salivary glands and the central nervous system entered an endocycle and sometimes formed polytene chromosomes. Since mitotically quiescent abdominal histoblasts still required Dmcdc2 to remain diploid, the inhibitory activity of G2/M cdk on DNA replication appeared to be separable from its activity as the mitosis promoting factor. These results suggest that in G2, escargot is required to maintain a high level of G2/M cdk that actively inhibits the entry into S phase. PMID:8620832

  6. The complement of protein kinases of the microsporidium Encephalitozoon cuniculi in relation to those of Saccharomyces cerevisiae and Schizosaccharomyces pombe

    Directory of Open Access Journals (Sweden)

    Vivares Christian P

    2007-09-01

    . The difficulty in assigning clear homology relationships for nine out of the twenty-nine microsporidian conventional protein kinases despite its compact genome reflects the phylogenetic distance between microsporidia and other eukaryotes. Indeed, the E. cuniculi genome presents a high proportion of genes in which evolution has been accelerated by up to four-fold. There are no orthologues of the protein kinases that constitute MAP kinase pathways and many other protein kinases with roles in nutrient signalling are absent from the E. cuniculi kinome. However, orthologous kinases can nonetheless be identified that correspond to members of the yeast kinomes with roles in some of the most fundamental cellular processes. For example, E. cuniculi has clear orthologues of virtually all the major conserved protein kinases that regulate the core cell cycle machinery (Aurora, Polo, DDK, CDK and Chk1. A comprehensive comparison of the homology relationships between the budding and fission yeast kinomes indicates that, despite an estimated 800 million years of independent evolution, the two model fungi share ~85% of their protein kinases. This will facilitate the annotation of many of the as yet uncharacterised fission yeast kinases, and also those of novel fungal genomes.

  7. Inhibition of clathrin by pitstop 2 activates the spindle assembly checkpoint and induces cell death in dividing HeLa cancer cells

    Directory of Open Access Journals (Sweden)

    Smith Charlotte M

    2013-01-01

    Full Text Available Abstract Background During metaphase clathrin stabilises the mitotic spindle kinetochore(K-fibres. Many anti-mitotic compounds target microtubule dynamics. Pitstop 2™ is the first small molecule inhibitor of clathrin terminal domain and inhibits clathrin-mediated endocytosis. We investigated its effects on a second function for clathrin in mitosis. Results Pitstop 2 did not impair clathrin recruitment to the spindle but disrupted its function once stationed there. Pitstop 2 trapped HeLa cells in metaphase through loss of mitotic spindle integrity and activation of the spindle assembly checkpoint, phenocopying clathrin depletion and aurora A kinase inhibition. Conclusions Pitstop 2 is therefore a new tool for investigating clathrin spindle dynamics. Pitstop 2 reduced viability in dividing HeLa cells, without affecting dividing non-cancerous NIH3T3 cells, suggesting that clathrin is a possible novel anti-mitotic drug target.

  8. Smurf2 as a novel mitotic regulator: From the spindle assembly checkpoint to tumorigenesis

    Directory of Open Access Journals (Sweden)

    Moore Finola E

    2009-07-01

    Full Text Available Abstract The execution of the mitotic program with high fidelity is dependent upon precise spatiotemporal regulation of posttranslational protein modifications. For example, the timely polyubiquitination of critical mitotic regulators by Anaphase Promoting Complex/Cyclosome (APC/C is essential for the metaphase to anaphase transition and mitotic exit. The spindle assembly checkpoint prevents unscheduled activity of APC/C-Cdc20 in early mitosis, allowing bipolar attachment of kinetochores to mitotic spindle and facilitating equal segregation of sister chromatids. The critical effector of the spindle checkpoint, Mitotic arrest deficient 2 (Mad2, is recruited to unattached kinetochores forming a complex with other regulatory proteins to efficiently and cooperatively inhibit APC/C-Cdc20. A weakened and/or dysfunctional spindle checkpoint has been linked to the development of genomic instability in both cell culture and animal models, and evidence suggests that aberrant regulation of the spindle checkpoint plays a critical role in human carcinogenesis. Recent studies have illuminated a network of both degradative and non-degradative ubiquitination events that regulate the metaphase to anaphase transition and mitotic exit. Within this context, our recent work showed that the HECT (Homologous to E6-AP C-terminus-family E3 ligase Smurf2 (Smad specific ubiquitin regulatory factor 2, known as a negative regulator of transforming growth factor-beta (TGF-β signaling, is required for a functional spindle checkpoint by promoting the functional localization and stability of Mad2. Here we discuss putative models explaining the role of Smurf2 as a new regulator in the spindle checkpoint. The dynamic mitotic localization of Smurf2 to the centrosome and other critical mitotic structures provides implications about mitotic checkpoint control dependent on various ubiquitination events. Finally, deregulated Smurf2 activity may contribute to carcinogenesis by

  9. In-silico modeling of the mitotic spindle assembly checkpoint.

    Directory of Open Access Journals (Sweden)

    Bashar Ibrahim

    Full Text Available BACKGROUND: The Mitotic Spindle Assembly Checkpoint ((MSAC is an evolutionary conserved mechanism that ensures the correct segregation of chromosomes by restraining cell cycle progression from entering anaphase until all chromosomes have made proper bipolar attachments to the mitotic spindle. Its malfunction can lead to cancer. PRINCIPLE FINDINGS: We have constructed and validated for the human (MSAC mechanism an in silico dynamical model, integrating 11 proteins and complexes. The model incorporates the perspectives of three central control pathways, namely Mad1/Mad2 induced Cdc20 sequestering based on the Template Model, MCC formation, and APC inhibition. Originating from the biochemical reactions for the underlying molecular processes, non-linear ordinary differential equations for the concentrations of 11 proteins and complexes of the (MSAC are derived. Most of the kinetic constants are taken from literature, the remaining four unknown parameters are derived by an evolutionary optimization procedure for an objective function describing the dynamics of the APC:Cdc20 complex. MCC:APC dissociation is described by two alternatives, namely the "Dissociation" and the "Convey" model variants. The attachment of the kinetochore to microtubuli is simulated by a switching parameter silencing those reactions which are stopped by the attachment. For both, the Dissociation and the Convey variants, we compare two different scenarios concerning the microtubule attachment dependent control of the dissociation reaction. Our model is validated by simulation of ten perturbation experiments. CONCLUSION: Only in the controlled case, our models show (MSAC behaviour at meta- to anaphase transition in agreement with experimental observations. Our simulations revealed that for (MSAC activation, Cdc20 is not fully sequestered; instead APC is inhibited by MCC binding.

  10. Msc1 acts through histone H2A.Z to promote chromosome stability in Schizosaccharomyces pombe.

    Science.gov (United States)

    Ahmed, Shakil; Dul, Barbara; Qiu, Xinxing; Walworth, Nancy C

    2007-11-01

    As a central component of the DNA damage checkpoint pathway, the conserved protein kinase Chk1 mediates cell cycle progression when DNA damage is generated. Msc1 was identified as a multicopy suppressor capable of facilitating survival in response to DNA damage of cells mutant for chk1. We demonstrate that loss of msc1 function results in an increased rate of chromosome loss and that an msc1 null allele exhibits genetic interactions with mutants in key kinetochore components. Multicopy expression of msc1 robustly suppresses a temperature-sensitive mutant (cnp1-1) in the centromere-specific histone H3 variant CENP-A, and localization of CENP-A to the centromere is compromised in msc1 null cells. We present several lines of evidence to suggest that Msc1 carries out its function through the histone H2A variant H2A.Z, encoded by pht1 in fission yeast. Like an msc1 mutant, a pht1 mutant also exhibits chromosome instability and genetic interactions with kinetochore mutants. Suppression of cnp1-1 by multicopy msc1 requires pht1. Likewise, suppression of the DNA damage sensitivity of a chk1 mutant by multicopy msc1 also requires pht1. We present the first genetic evidence that histone H2A.Z may participate in centromere function in fission yeast and propose that Msc1 acts through H2A.Z to promote chromosome stability and cell survival following DNA damage. PMID:17947424

  11. Preserving Yeast Genetic Heritage through DNA Damage Checkpoint Regulation and Telomere Maintenance

    Directory of Open Access Journals (Sweden)

    Huilin Zhou

    2012-10-01

    Full Text Available In order to preserve genome integrity, extrinsic or intrinsic DNA damages must be repaired before they accumulate in cells and trigger other mutations and genome rearrangements. Eukaryotic cells are able to respond to different genotoxic stresses as well as to single DNA double strand breaks (DSBs, suggesting highly sensitive and robust mechanisms to detect lesions that trigger a signal transduction cascade which, in turn, controls the DNA damage response (DDR. Furthermore, cells must be able to distinguish natural chromosomal ends from DNA DSBs in order to prevent inappropriate checkpoint activation, DDR and chromosomal rearrangements. Since the original discovery of RAD9, the first DNA damage checkpoint gene identified in Saccharomyces cerevisiae, many genes that have a role in this pathway have been identified, including MRC1, MEC3, RAD24, RAD53, DUN1, MEC1 and TEL1. Extensive studies have established most of the genetic basis of the DNA damage checkpoint and uncovered its different functions in cell cycle regulation, DNA replication and repair, and telomere maintenance. However, major questions concerning the regulation and functions of the DNA damage checkpoint remain to be answered. First, how is the checkpoint activity coupled to DNA replication and repair? Second, how do cells distinguish natural chromosome ends from deleterious DNA DSBs? In this review we will examine primarily studies performed using Saccharomyces cerevisiae as a model system.

  12. CK (Creatine Kinase) Test

    Science.gov (United States)

    ... be limited. Home Visit Global Sites Search Help? Creatine Kinase Share this page: Was this page helpful? Also known as: CK; Total CK; Creatine Phosphokinase; CPK Formal name: Creatine Kinase Related tests: ...

  13. Immune checkpoints aberrations and gastric cancer; assessment of prognostic value and evaluation of therapeutic potentials.

    Science.gov (United States)

    Abdel-Rahman, Omar

    2016-01-01

    Till now, the prognosis of advanced gastric cancer looked dreadful; thus the search for newer better approaches for this lethal disease has been a strategic target for cancer researchers. In recent years, important immunobiological aspects of the tumor have been revealed with the subsequent proposal of immune check point inhibitors to target these pathways. Clinically, unselected use of immune checkpoint inhibitors in gastric cancer has been deemed with failure; in contrast to the clear success of more recent studies reporting on the use of pembrolizumab in molecularly selected patients. This may illustrate that any future use of immune checkpoint inhibitors in gastric cancer has to be molecularly supported. This review provides a delicate dissection of the clinical and immunobiological considerations underlying the use of these agents in addition to a thorough review of the published clinical data of immune checkpoint inhibitors in gastric cancer. PMID:26321371

  14. The Replication Checkpoint Prevents Two Types of Fork Collapse without Regulating Replisome Stability.

    Science.gov (United States)

    Dungrawala, Huzefa; Rose, Kristie L; Bhat, Kamakoti P; Mohni, Kareem N; Glick, Gloria G; Couch, Frank B; Cortez, David

    2015-09-17

    The ATR replication checkpoint ensures that stalled forks remain stable when replisome movement is impeded. Using an improved iPOND protocol combined with SILAC mass spectrometry, we characterized human replisome dynamics in response to fork stalling. Our data provide a quantitative picture of the replisome and replication stress response proteomes in 32 experimental conditions. Importantly, rather than stabilize the replisome, the checkpoint prevents two distinct types of fork collapse. Unsupervised hierarchical clustering of protein abundance on nascent DNA is sufficient to identify protein complexes and place newly identified replisome-associated proteins into functional pathways. As an example, we demonstrate that ZNF644 complexes with the G9a/GLP methyltransferase at replication forks and is needed to prevent replication-associated DNA damage. Our data reveal how the replication checkpoint preserves genome integrity, provide insights into the mechanism of action of ATR inhibitors, and will be a useful resource for replication, DNA repair, and chromatin investigators. PMID:26365379

  15. Hierarchical Non-blocking Coordinated Checkpointing Algorithms for Mobile Distributed Computing

    Directory of Open Access Journals (Sweden)

    Parveen Kumar

    2010-01-01

    Full Text Available Mobile system typically uses wireless communication which is based on electromagnetic waves and utilizes a shared broadcast medium. This has made possible creating a mobile distributed computing environment and has brought us several new challenges in distributed protocol design. So many issues such as range of transmission, limited power supply due to battery capacity and mobility of processes. These new issue makes traditional recovery algorithm unsuitable. In this paper, we propose hierarchical non blocking coordinated checkpointing algorithms suitable for mobile distributed computing. The algorithm is non-blocking, requires minimum message logging, has minimum stable storage requirement and produce a consistent set of checkpoints. This algorithm requires minimum number of processes to take checkpoint.

  16. Combining targeted therapy and immune checkpoint inhibitors in the treatment of metastatic melanoma

    Institute of Scientific and Technical Information of China (English)

    Teresa Kim; Rodabe N Amaria; Christine Spencer; Alexandre Reuben; Zachary A Cooper; Jennifer A Wargo

    2014-01-01

    Melanoma is the deadliest form of skin cancer and has an incidence that is rising faster than any other solid tumor. Metastatic melanoma treatment has considerably progressed in the past ifve years with the introduction of targeted therapy (BARF and MEK inhibitors) and immune checkpoint blockade (anti-CTLA4, anti-PD-1, and anti-PD-L1). However, each treatment modality has limitations. Treatment with targeted therapy has been associated with a high response rate, but with short-term responses. Conversely, treatment with immune checkpoint blockade has a lower response rate, but with long-term responses. Targeted therapy affects antitumor immunity, and synergy may exist when targeted therapy is combined with immunotherapy. hTis article presents a brief review of the rationale and evidence for the potential synergy between targeted therapy and immune checkpoint blockade. Challenges and directions for future studies are also proposed.

  17. Use of checkpoint-restart for complex HEP software on traditional architectures and Intel MIC

    International Nuclear Information System (INIS)

    Process checkpoint-restart is a technology with great potential for use in HEP workflows. Use cases include debugging, reducing the startup time of applications both in offline batch jobs and the High Level Trigger, permitting job preemption in environments where spare CPU cycles are being used opportunistically and efficient scheduling of a mix of multicore and single-threaded jobs. We report on tests of checkpoint-restart technology using CMS software, Geant4-MT (multi-threaded Geant4), and the DMTCP (Distributed Multithreaded Checkpointing) package. We analyze both single- and multi-threaded applications and test on both standard Intel x86 architectures and on Intel MIC. The tests with multi-threaded applications on Intel MIC are used to consider scalability and performance. These are considered an indicator of what the future may hold for many-core computing

  18. RNA interference regulates the cell cycle checkpoint through the RNA export factor, Ptr1, in fission yeast

    International Nuclear Information System (INIS)

    Highlights: ► RNAi is linked to the cell cycle checkpoint in fission yeast. ► Ptr1 co-purifies with Ago1. ► The ptr1-1 mutation impairs the checkpoint but does not affect gene silencing. ► ago1+ and ptr1+ regulate the cell cycle checkpoint via the same pathway. ► Mutations in ago1+ and ptr1+ lead to the nuclear accumulation of poly(A)+ RNAs. -- Abstract: Ago1, an effector protein of RNA interference (RNAi), regulates heterochromatin silencing and cell cycle arrest in fission yeast. However, the mechanism by which Ago1 controls cell cycle checkpoint following hydroxyurea (HU) treatment has not been elucidated. In this study, we show that Ago1 and other RNAi factors control cell cycle checkpoint following HU treatment via a mechanism independent of silencing. While silencing requires dcr1+, the overexpression of ago1+ alleviated the cell cycle defect in dcr1Δ. Ago1 interacted with the mRNA export factor, Ptr1. The ptr1-1 mutation impaired cell cycle checkpoint but gene silencing was unaffected. Genetic analysis revealed that the regulation of cell cycle checkpoint by ago1+ is dependent on ptr1+. Nuclear accumulation of poly(A)+ RNAs was detected in mutants of ago1+ and ptr1+, suggesting there is a functional link between the cell cycle checkpoint and RNAi-mediated RNA quality control.

  19. The anaphase inhibitor of Saccharomyces cerevisiae Pds1p is a target of the DNA damage checkpoint pathway

    International Nuclear Information System (INIS)

    Inhibition of DNA replication and physical DNA damage induce checkpoint responses that arrest cell cycle progression at two different stages. In Saccharomyces cerevisiae, the execution of both checkpoint responses requires the Mec1 and Rad53 proteins. This observation led to the suggestion that these checkpoint responses are mediated through a common signal transduction pathway. However, because the checkpoint-induced arrests occur at different cell cycle stages, the downstream effectors mediating these arrests are likely to be distinct. We have previously shown that the S. cerevisiae protein Pds1p is an anaphase inhibitor and is essential for cell cycle arrest in mitosis in the presence DNA damage. Herein we show that DNA damage, but not inhibition of DNA replication, induces the phosphorylation of Pds1p. Analyses of Pds1p phosphorylation in different checkpoint mutants reveal that in the presence of DNA damage, Pds1p is phosphorylated in a Mec1p- and Rad9p-dependent hut Rad53p-independent manner. Our data place Pds1p and Rad53p on parallel branches of the DNA damage checkpoint pathway. We suggest that Pds1p is a downstream target of the DNA damage checkpoint pathway and that it is involved in implementing the DNA damage checkpoint arrest specifically in mitosis

  20. Functions of spindle check-point and its relationship to chromosome instability

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    It is generally believed that the equal distribution of genetic materials to two daughter cells during mitosis is the key to cell health and development. During the dynamic process, spindle checkpoint plays a very important role in chromosome movements and final sister chromatid separation. The equal and precise segregation of chromosomes contributes to the genomic stability while aberrant separations result in chromosome instability that causes pathogenesis of certain diseases such as Down's syndrome and cancers. Kinetochore and its regulatory proteins consist of the spindle checkpoint and determine the spatial and temporal orders of chromosome segregation.

  1. Constitutive Cdk2 activity promotes aneuploidy while altering the spindle assembly and tetraploidy checkpoints

    DEFF Research Database (Denmark)

    Jahn, Stephan C; Corsino, Patrick E; Davis, Bradley J;

    2013-01-01

    The cell has many mechanisms for protecting the integrity of its genome. These mechanisms are often weakened or absent in many cancers, leading to high rates of chromosomal instability in tumors. Control of the cell cycle is crucial for the function of these checkpoints, and is frequently lost in...... instability. Expression of these complexes in the MCF10A cell line leads to retinoblastoma protein (Rb) hyperphosphorylation, a subsequent increase in proliferation rate, and increased expression of the spindle assembly checkpoint protein Mad2. This results in a strengthening of the spindle assembly...

  2. Cross talk of tyrosine kinases with the DNA damage signaling pathways.

    Science.gov (United States)

    Mahajan, Kiran; Mahajan, Nupam P

    2015-12-15

    Tyrosine kinases respond to extracellular and intracellular cues by activating specific cellular signaling cascades to regulate cell cycle, growth, proliferation, differentiation and survival. Likewise, DNA damage response proteins (DDR) activated by DNA lesions or chromatin alterations recruit the DNA repair and cell cycle checkpoint machinery to restore genome integrity and cellular homeostasis. Several new examples have been uncovered in recent studies which reveal novel epigenetic and non-epigenetic mechanisms by which tyrosine kinases interact with DDR proteins to dictate cell fate, i.e. survival or apoptosis, following DNA damage. These studies reveal the ability of tyrosine kinases to directly regulate the activity of DNA repair and cell cycle check point proteins by tyrosine phosphorylation. In addition, tyrosine kinases epigenetically regulate DNA damage signaling pathways by modifying the core histones as well as chromatin modifiers at critical tyrosine residues. Thus, deregulated tyrosine kinase driven epigenomic alterations have profound implications in cancer, aging and genetic disorders. Consequently, targeting oncogenic tyrosine kinase induced epigenetic alterations has gained significant traction in overcoming cancer cell resistance to various therapies. This review discusses mechanisms by which tyrosine kinases interact with DDR pathways to regulate processes critical for maintaining genome integrity as well as clinical strategies for targeted cancer therapies. PMID:26546517

  3. Naphthalimides Induce G2 Arrest Through the ATM-Activated Chk2-Executed Pathway in HCT116 Cells

    Directory of Open Access Journals (Sweden)

    Hong Zhu

    2009-11-01

    Full Text Available Naphthalimides, particularly amonafide and 2-(2-dimethylamino-6-thia-2-aza-benzo[def]chrysene-1,3-diones (R16, have been identified to possess anticancer activities and to induce G2-M arrest through inhibiting topoisomerase II accompanied by Chk1 degradation. The current study was designed to precisely dissect the signaling pathway(s responsible for the naphthalimide-induced cell cycle arrest in human colon carcinoma HCT116 cells. Using phosphorylated histone H3 and mitotic protein monoclonal 2 as mitosis markers, we first specified the G2 arrest elicited by the R16 and amonafide. Then, R16 and amonafide were revealed to induce phosphorylation of the DNA damage sensor ataxia telangiectasia-mutated (ATM responding to DNA double-strand breaks (DSBs. Inhibition of ATM by both the pharmacological inhibitor caffeine and the specific small interference RNA (siRNA rescued the G2 arrest elicited by R16, indicating its ATM-dependent characteristic. Furthermore, depletion of Chk2, but not Chk1 with their corresponding siRNA, statistically significantly reversed the R16- and amonafide-triggered G2 arrest. Moreover, the naphthalimides phosphorylated Chk2 in an ATM-dependent manner but induced Chk1 degradation. These data indicate that R16 and amonafide preferentially used Chk2 as evidenced by the differential ATM-executed phosphorylation of Chk1 and Chk2. Thus, a clear signaling pathway can be established, in which ATM relays the DNA DSBs signaling triggered by the naphthalimides to the checkpoint kinases, predominantly to Chk2,which finally elicits G2 arrest. The mechanistic elucidation not only favors the development of the naphthalimides as anticancer agents but also provides an alternative strategy of Chk2 inhibition to potentiate the anticancer activities of these agents.

  4. Cells bearing chromosome aberrations lacking one telomere are selectively blocked at the G2/M checkpoint

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, Pilar [Unitat de Biologia Cel.lular, Departament de Biologia Cel.lular, Fisiologia i Immunologia, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Barquinero, Joan Francesc [Unitat d' Antropologia Biologica, Departament de Biologia Animal, Biologia Vegetal i Ecologia, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Duran, Assumpta [Unitat de Biologia Cel.lular, Departament de Biologia Cel.lular, Fisiologia i Immunologia, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Caballin, Maria Rosa [Unitat d' Antropologia Biologica, Departament de Biologia Animal, Biologia Vegetal i Ecologia, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Ribas, Montserrat [Servei de Radiofisica i Radioproteccio de l' Hospital de la Santa Creu i Sant Pau, 08025 Barcelona (Spain); Barrios, Leonardo, E-mail: Lleonard.Barrios@uab.cat [Unitat de Biologia Cel.lular, Departament de Biologia Cel.lular, Fisiologia i Immunologia, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain)

    2009-11-02

    Cell cycle checkpoints are part of the cellular mechanisms to maintain genomic integrity. After ionizing radiation exposure, the cells can show delay or arrest in their progression through the cell cycle, as well as an activation of the DNA repair machinery in order to reduce the damage. The G2/M checkpoint prevents G2 cells entering mitosis until the DNA damage has been reduced. The present study evaluates which G0 radiation-induced chromosome aberrations are negatively selected in the G2/M checkpoint. For this purpose, peripheral blood samples were irradiated at 1 and 3 Gy of {gamma}-rays, and lymphocytes were cultured for 48 h. Calyculin-A and Colcemid were used to analyze, in the same slide, cells in G2 and M. Chromosome spreads were consecutively analyzed by solid stain, pancentromeric and pantelomeric FISH and mFISH. The results show that the frequency of incomplete chromosome elements, those lacking a telomeric signal at one end, decreases abruptly from G2 to M. This indicates that cells with incomplete chromosome elements can progress from G0 to G2, but at the G2/M checkpoint suffer a strong negative selection.

  5. Clonal neoantigens elicit T cell immunoreactivity and sensitivity to immune checkpoint blockade

    DEFF Research Database (Denmark)

    McGranahan, Nicholas; Furness, Andrew J S; Rosenthal, Rachel;

    2016-01-01

    As tumors grow, they acquire mutations, some of which create neoantigens that influence the response of patients to immune checkpoint inhibitors. We explored the impact of neoantigen intratumor heterogeneity (ITH) on antitumor immunity. Through integrated analysis of ITH and neoantigen burden, we...

  6. Synthesis of Fault-Tolerant Embedded Systems with Checkpointing and Replication

    DEFF Research Database (Denmark)

    Izosimov, Viacheslav; Pop, Paul; Eles, Petru; Peng, Zebo

    We present an approach to the synthesis of fault-tolerant hard real-time systems for safety-critical applications. We use checkpointing with rollback recovery and active replication for tolerating transient faults. Processes are statically scheduled and communications are performed using the time...

  7. Cells bearing chromosome aberrations lacking one telomere are selectively blocked at the G2/M checkpoint

    International Nuclear Information System (INIS)

    Cell cycle checkpoints are part of the cellular mechanisms to maintain genomic integrity. After ionizing radiation exposure, the cells can show delay or arrest in their progression through the cell cycle, as well as an activation of the DNA repair machinery in order to reduce the damage. The G2/M checkpoint prevents G2 cells entering mitosis until the DNA damage has been reduced. The present study evaluates which G0 radiation-induced chromosome aberrations are negatively selected in the G2/M checkpoint. For this purpose, peripheral blood samples were irradiated at 1 and 3 Gy of γ-rays, and lymphocytes were cultured for 48 h. Calyculin-A and Colcemid were used to analyze, in the same slide, cells in G2 and M. Chromosome spreads were consecutively analyzed by solid stain, pancentromeric and pantelomeric FISH and mFISH. The results show that the frequency of incomplete chromosome elements, those lacking a telomeric signal at one end, decreases abruptly from G2 to M. This indicates that cells with incomplete chromosome elements can progress from G0 to G2, but at the G2/M checkpoint suffer a strong negative selection.

  8. Importance of immunopharmacogenomics in cancer treatment: Patient selection and monitoring for immune checkpoint antibodies.

    Science.gov (United States)

    Choudhury, Noura; Nakamura, Yusuke

    2016-02-01

    In the last 5 years, immune checkpoint antibodies have become established as anticancer agents for various types of cancer. These antibody drugs, namely cytotoxic T-lymphocyte-associated antigen, programmed death-1, and programmed death ligand-1 antibodies, have revealed relatively high response rates, the ability to induce durable responses, and clinical efficacy in malignancies not previously thought to be susceptible to immune-based strategies. However, because of its unique mechanisms of activating the host immune system against cancer as well as expensive cost, immune checkpoint blockade faces novel challenges in selecting appropriate patient populations, monitoring clinical responses, and predicting immune adverse events. The development of objective criteria for selecting patient populations that are likely to have benefit from these therapies has been vigorously investigated but still remains unclear. In this review, we describe immune checkpoint inhibition-specific challenges with patient selection and monitoring, and focus on approaches to remedy these challenges. We also discuss applications of the emerging field of immunopharmacogenomics for guiding selection and monitoring for anti-immune checkpoint treatment. PMID:26678880

  9. Preserved DNA Damage Checkpoint Pathway Protects against Complications in Long-Standing Type 1 Diabetes

    Energy Technology Data Exchange (ETDEWEB)

    Bhatt, Shweta; Gupta, Manoj; Khamaisi, Mogher; Martinez, Rachael; Gritsenko, Marina A.; Wagner, Bridget; Guye, Patrick; Busskamp, Volker; Shirakawa, Jun; Wu, Gongxiong; Liew, Chong Wee; Clauss, Therese RW; Valdez, Ivan; EL Ouaaman, Abdelfattah; Dirice, Ercument; Takatani, Tomozumi; Keenan, Hillary; Smith, Richard D.; Church, George; Weiss, Ron; Wagers, Amy J.; Qian, Weijun; King, George L.; Kulkami, Rohit N.

    2015-08-04

    Themechanisms underlying the development of complications in type 1 diabetes (T1D) are poorly understood. Disease modeling of induced pluripotent stem cells (iPSCs) from patients with longstanding T1D(disease durationR50 years) with severe (Medalist +C) or absent to mild complications (Medalist *C) revealed impaired growth, reprogramming, and differentiation in Medalist +C. Genomics and proteomics analyses suggested differential regulation of DNA damage checkpoint proteins favoring protection from cellular apoptosis in Medalist *C. In silico analyses showed altered expression patterns of DNA damage checkpoint factors among the Medalist groups to be targets of miR200, whose expression was significantly elevated in Medalist +C serum. Notably, neurons differentiated from Medalist +C iPSCs exhibited enhanced susceptibility to genotoxic stress that worsened upon miR200 overexpression. Furthermore, knockdown of miR200 in Medalist +C fibroblasts and iPSCs rescued checkpoint protein expression and reduced DNA damage.WeproposemiR200-regulated DNA damage checkpoint pathway as a potential therapeutic target for treating complications of diabetes.

  10. Complex Haploinsufficiency-Based Genetic Analysis of the NDR/Lats Kinase Cbk1 Provides Insight into Its Multiple Functions in Candida albicans.

    Science.gov (United States)

    Saputo, Sarah; Norman, Kaitlyn L; Murante, Thomas; Horton, Brooke N; Diaz, Jacinto De La Cruz; DiDone, Louis; Colquhoun, Jennifer; Schroeder, Jeremy W; Simmons, Lyle A; Kumar, Anuj; Krysan, Damian J

    2016-07-01

    Although the analysis of genetic interactions and networks is a powerful approach to understanding biology, it has not been applied widely to the pathogenic yeast Candida albicans Here, we describe the use of both screening and directed genetic interaction studies based on complex haploinsufficiency to probe the function of the R: egulation of A: ce2 and M: orphogenesis (RAM) pathway in C. albicans A library of 5200 Tn7-mutagenized derivatives of a parental strain heterozygous at CBK1, the key kinase in the RAM pathway, was screened for alterations in serum-induced filamentation. Following confirmation of phenotypes and identification of insertion sites by sequencing, a set of 36 unique double heterozygous strains showing complex haploinsufficiency was obtained. In addition to a large set of genes regulated by the RAM transcription factor Ace2, genes related to cell wall biosynthesis, cell cycle, polarity, oxidative stress, and nitrogen utilization were identified. Follow-up analysis led to the first demonstration that the RAM pathway is required for oxidative stress tolerance in a manner related to the two-component-regulated kinase Chk1 and revealed a potential direct connection between the RAM pathway and the essential Mps1 spindle pole-related kinase. In addition, genetic interactions with CDC42-related genes MSB1, a putative scaffold protein, and RGD3, a putative Rho GTPase-activating protein (GAP) were identified. We also provide evidence that Rgd3 is a GAP for Cdc42 and show that its localization and phosphorylation are dependent on Cbk1. PMID:27206715

  11. Temporal Gradient in the Clock Gene and Cell-Cycle Checkpoint Kinase Wee1 Expression along the Gut

    Czech Academy of Sciences Publication Activity Database

    Polidarová, Lenka; Soták, Matúš; Sládek, Martin; Pácha, Jiří; Sumová, Alena

    2009-01-01

    Roč. 26, č. 4 (2009), s. 607-620. ISSN 0742-0528 R&D Projects: GA AV ČR(CZ) IAA500110605; GA ČR(CZ) GA305/09/0321; GA MŠk(CZ) LC554 EU Projects: European Commission(XE) 18741 - EUCLOCK Institutional research plan: CEZ:AV0Z50110509 Keywords : intestine epithelium * circadian clock gene * cell cycle Subject RIV: ED - Physiology Impact factor: 3.987, year: 2009

  12. Integrated genomic analysis identifies the mitotic checkpoint kinase WEE1 as a novel therapeutic target in medulloblastoma

    OpenAIRE

    Harris, Peter S; Venkataraman, Sujatha; Alimova, Irina; Birks, Diane K; Balakrishnan, Ilango; Cristiano, Brian; Donson, Andrew M; Dubuc, Adrian M.; Taylor, Michael D.; Foreman, Nicholas K.; Reigan, Philip; Vibhakar, Rajeev

    2014-01-01

    Background Medulloblastoma is the most common type of malignant brain tumor that afflicts children. Although recent advances in chemotherapy and radiation have improved outcomes, high-risk patients do poorly with significant morbidity. Methods To identify new molecular targets, we performed an integrated genomic analysis using structural and functional methods. Gene expression profiling in 16 medulloblastoma patient samples and subsequent gene set enrichment analysis indicated that cell cycle...

  13. Mutation of serine 1333 in the ATR HEAT repeats creates a hyperactive kinase.

    Directory of Open Access Journals (Sweden)

    Jessica W Luzwick

    Full Text Available Subcellular localization, protein interactions, and post-translational modifications regulate the DNA damage response kinases ATR, ATM, and DNA-PK. During an analysis of putative ATR phosphorylation sites, we found that a single mutation at S1333 creates a hyperactive kinase. In vitro and in cells, mutation of S1333 to alanine (S1333A-ATR causes elevated levels of kinase activity with and without the addition of the protein activator TOPBP1. S1333 mutations to glycine, arginine, or lysine also create a hyperactive kinase, while mutation to aspartic acid decreases ATR activity. S1333A-ATR maintains the G2 checkpoint and promotes completion of DNA replication after transient exposure to replication stress but the less active kinase, S1333D-ATR, has modest defects in both of these functions. While we find no evidence that S1333 is phosphorylated in cultured cells, our data indicate that small changes in the HEAT repeats can have large effects on kinase activity. These mutants may serve as useful tools for future studies of the ATR pathway.

  14. Cyclin E Is Stabilized in Response to Replication Fork Barriers Leading to Prolonged S Phase Arrest*

    Science.gov (United States)

    Lu, Xiaoyan; Liu, Jia; Legerski, Randy J.

    2009-01-01

    Cyclin E is a regulator of cyclin-dependent protein kinases (Cdks) and is involved in mediating the cell cycle transition from G1 to S phase. Here, we describe a novel function for cyclin E in the long term maintenance of checkpoint arrest in response to replication barriers. Exposure of cells to mitomycin C or UV irradiation, but not ionizing radiation, induces stabilization of cyclin E. Stabilization of cyclin E reduces the activity of Cdk2-cyclin A, resulting in a slowing of S phase progression and arrest. In addition, cyclin E is shown to be required for stabilization of Cdc6, which is required for activation of Chk1 and the replication checkpoint pathway. Furthermore, the stabilization of cyclin E in response to replication fork barriers depends on ATR, but not Nbs1 or Chk1. These results indicate that in addition to its well studied role in promoting cell cycle progression, cyclin E also has a role in regulating cell cycle arrest in response to DNA damage. PMID:19812034

  15. Nuclear respiratory factor 1 overexpression attenuates anti-benzopyrene‑7,8-diol-9,10-epoxide-induced S-phase arrest of bronchial epithelial cells.

    Science.gov (United States)

    Wu, Jing; Wang, Yaning; Wo, Da; Zhang, Lijuan; Li, Jue

    2016-05-01

    Nuclear respiratory factor 1 (NRF-1) has important roles in the regulation of several key metabolic genes required for cellular growth and respiration. A previous study by our group indicated that NRF‑1 is involved in mitochondrial dysfunction induced by the environmental pollutant benzo[a]pyrene in the 16HBE human bronchial epithelial cell line. In the present study, it was observed that its genotoxic metabolite, anti‑benzopyrene‑7,8‑diol‑9,10‑epoxide (BPDE), triggered cell cycle arrest in S‑phase in 16HBE cells by activating ataxia-telangiectasia (ATM)/checkpoint kinase (Chk)2 and ATM and Rad3 related (ATR)/Chk1 signaling pathways. NRF‑1 expression was suppressed by BPDE after treatment for 6 h. Flow cytometric analysis revealed that NRF‑1 overexpression attenuated cell cycle arrest in S‑phase induced by BPDE. In line with this result, DNA‑damage checkpoints were activated following NRF‑1 overexpression, as demonstrated by increased phosphorylation of ATM, Chk2 and γH2AX, but not ATR and Chk1, according to western blot analysis. It was therefore indicated that NRF‑1 overexpression attenuated BPDE‑induced S‑phase arrest via the ATM/Chk2 signaling pathway. PMID:27035420

  16. Muscle phosphorylase kinase deficiency

    DEFF Research Database (Denmark)

    Preisler, N; Orngreen, M C; Echaniz-Laguna, A; Laforet, P; Lonsdorfer-Wolf, E; Doutreleau, S; Geny, B; Akman, H O; Dimauro, S; Vissing, J

    2012-01-01

    To examine metabolism during exercise in 2 patients with muscle phosphorylase kinase (PHK) deficiency and to further define the phenotype of this rare glycogen storage disease (GSD).......To examine metabolism during exercise in 2 patients with muscle phosphorylase kinase (PHK) deficiency and to further define the phenotype of this rare glycogen storage disease (GSD)....

  17. Phosphoproteomic Profiling Reveals Epstein-Barr Virus Protein Kinase Integration of DNA Damage Response and Mitotic Signaling.

    Science.gov (United States)

    Li, Renfeng; Liao, Gangling; Nirujogi, Raja Sekhar; Pinto, Sneha M; Shaw, Patrick G; Huang, Tai-Chung; Wan, Jun; Qian, Jiang; Gowda, Harsha; Wu, Xinyan; Lv, Dong-Wen; Zhang, Kun; Manda, Srikanth S; Pandey, Akhilesh; Hayward, S Diane

    2015-12-01

    Epstein-Barr virus (EBV) is etiologically linked to infectious mononucleosis and several human cancers. EBV encodes a conserved protein kinase BGLF4 that plays a key role in the viral life cycle. To provide new insight into the host proteins regulated by BGLF4, we utilized stable isotope labeling by amino acids in cell culture (SILAC)-based quantitative proteomics to compare site-specific phosphorylation in BGLF4-expressing Akata B cells. Our analysis revealed BGLF4-mediated hyperphosphorylation of 3,046 unique sites corresponding to 1,328 proteins. Frequency analysis of these phosphosites revealed a proline-rich motif signature downstream of BGLF4, indicating a broader substrate recognition for BGLF4 than its cellular ortholog cyclin-dependent kinase 1 (CDK1). Further, motif analysis of the hyperphosphorylated sites revealed enrichment in ATM, ATR and Aurora kinase substrates while functional analyses revealed significant enrichment of pathways related to the DNA damage response (DDR), mitosis and cell cycle. Phosphorylation of proteins associated with the mitotic spindle assembly checkpoint (SAC) indicated checkpoint activation, an event that inactivates the anaphase promoting complex/cyclosome, APC/C. Furthermore, we demonstrated that BGLF4 binds to and directly phosphorylates the key cellular proteins PP1, MPS1 and CDC20 that lie upstream of SAC activation and APC/C inhibition. Consistent with APC/C inactivation, we found that BGLF4 stabilizes the expression of many known APC/C substrates. We also noted hyperphosphorylation of 22 proteins associated the nuclear pore complex, which may contribute to nuclear pore disassembly and SAC activation. A drug that inhibits mitotic checkpoint activation also suppressed the accumulation of extracellular EBV virus. Taken together, our data reveal that, in addition to the DDR, manipulation of mitotic kinase signaling and SAC activation are mechanisms associated with lytic EBV replication. All MS data have been deposited in

  18. Ghost Process: a Sound Basis to Implement Process Duplication, Migration and Checkpoint-Restart in Linux Clusters

    OpenAIRE

    Vallée, Geoffroy; Lottiaux, Renaud; Margery, David; Morin, Christine; Berthou, Jean-Yves

    2005-01-01

    Process management mechanisms (process duplication, migration and checkpoint-restart) are very useful for high performance and high availability in clustering systems. The single system image approach aims at providing a global process management service with mechanisms for process checkpoint, process migration and process duplication. In this context, a common mechanism for process virtualization is highly desirable but traditional operating systems do not provide such a mechanism. This pape...

  19. DNA damage-induced metaphase I arrest is mediated by the spindle assembly checkpoint and maternal age

    OpenAIRE

    Marangos, P; Stevense, M.; Niaka, K.; Lagoudaki, M.; Nabti, I.; Jessberger, R.; Carroll, J.

    2015-01-01

    In mammalian oocytes DNA damage can cause chromosomal abnormalities that potentially lead to infertility and developmental disorders. However, there is little known about the response of oocytes to DNA damage. Here we find that oocytes with DNA damage arrest at metaphase of the first meiosis (MI). The MI arrest is induced by the spindle assembly checkpoint (SAC) because inhibiting the SAC overrides the DNA damage-induced MI arrest. Furthermore, this MI checkpoint is compromised in oocytes fro...

  20. Telomerase expression is sufficient for chromosomal integrity in cells lacking p53 dependent G1 checkpoint function

    Directory of Open Access Journals (Sweden)

    Simpson Dennis

    2005-01-01

    Full Text Available Abstract Background Secondary cultures of human fibroblasts display a finite lifespan ending at senescence. Loss of p53 function by mutation or viral oncogene expression bypasses senescence, allowing cell division to continue for an additional 10 – 20 doublings. During this time chromosomal aberrations seen in mitotic cells increase while DNA damage and decatenation checkpoint functions in G2 cells decrease. Methods To explore this complex interplay between chromosomal instability and checkpoint dysfunction, human fibroblast lines were derived that expressed HPV16E6 oncoprotein or dominant-negative alleles of p53 (A143V and H179Q with or without the catalytic subunit of telomerase. Results Cells with normal p53 function displayed 86 – 93% G1 arrest after exposure to 1.5 Gy ionizing radiation (IR. Expression of HPV16E6 or p53-H179Q severely attenuated G1 checkpoint function (3 – 20% arrest while p53-A143V expression induced intermediate attenuation (55 – 57% arrest irrespective of telomerase expression. All cell lines, regardless of telomerase expression or p53 status, exhibited a normal DNA damage G2 checkpoint response following exposure to 1.5 Gy IR prior to the senescence checkpoint. As telomerase-negative cells bypassed senescence, the frequencies of chromosomal aberrations increased generally congruent with attenuation of G2 checkpoint function. Telomerase expression allowed cells with defective p53 function to grow >175 doublings without chromosomal aberrations or attenuation of G2 checkpoint function. Conclusion Thus, chromosomal instability in cells with defective p53 function appears to depend upon telomere erosion not loss of the DNA damage induced G1 checkpoint.

  1. RNA interference regulates the cell cycle checkpoint through the RNA export factor, Ptr1, in fission yeast

    Energy Technology Data Exchange (ETDEWEB)

    Iida, Tetsushi, E-mail: tiida@nig.ac.jp [Division of Cytogenetics, National Institute of Genetics, Mishima, 1111 Yata, Mishima 411-8540 (Japan); The Graduate University for Advanced Studies, Sokendai, Mishima, 1111 Yata, Mishima 411-8540 (Japan); Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), 4-1-8, Honcho, Kawaguchi-shi, Saitama 332-0012 (Japan); Iida, Naoko [Division of Mutagenesis, National Institute of Genetics, Mishima, 1111 Yata, Mishima 411-8540 (Japan); Tsutsui, Yasuhiro [Department of Life Science, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuda-cho, Midori-ku, Yokohama 226-8501 (Japan); Yamao, Fumiaki [Division of Mutagenesis, National Institute of Genetics, Mishima, 1111 Yata, Mishima 411-8540 (Japan); The Graduate University for Advanced Studies, Sokendai, Mishima, 1111 Yata, Mishima 411-8540 (Japan); Kobayashi, Takehiko [Division of Cytogenetics, National Institute of Genetics, Mishima, 1111 Yata, Mishima 411-8540 (Japan); The Graduate University for Advanced Studies, Sokendai, Mishima, 1111 Yata, Mishima 411-8540 (Japan)

    2012-10-12

    Highlights: Black-Right-Pointing-Pointer RNAi is linked to the cell cycle checkpoint in fission yeast. Black-Right-Pointing-Pointer Ptr1 co-purifies with Ago1. Black-Right-Pointing-Pointer The ptr1-1 mutation impairs the checkpoint but does not affect gene silencing. Black-Right-Pointing-Pointer ago1{sup +} and ptr1{sup +} regulate the cell cycle checkpoint via the same pathway. Black-Right-Pointing-Pointer Mutations in ago1{sup +} and ptr1{sup +} lead to the nuclear accumulation of poly(A){sup +} RNAs. -- Abstract: Ago1, an effector protein of RNA interference (RNAi), regulates heterochromatin silencing and cell cycle arrest in fission yeast. However, the mechanism by which Ago1 controls cell cycle checkpoint following hydroxyurea (HU) treatment has not been elucidated. In this study, we show that Ago1 and other RNAi factors control cell cycle checkpoint following HU treatment via a mechanism independent of silencing. While silencing requires dcr1{sup +}, the overexpression of ago1{sup +} alleviated the cell cycle defect in dcr1{Delta}. Ago1 interacted with the mRNA export factor, Ptr1. The ptr1-1 mutation impaired cell cycle checkpoint but gene silencing was unaffected. Genetic analysis revealed that the regulation of cell cycle checkpoint by ago1{sup +} is dependent on ptr1{sup +}. Nuclear accumulation of poly(A){sup +} RNAs was detected in mutants of ago1{sup +} and ptr1{sup +}, suggesting there is a functional link between the cell cycle checkpoint and RNAi-mediated RNA quality control.

  2. Intestinal microbiome analyses identify melanoma patients at risk for checkpoint-blockade-induced colitis.

    Science.gov (United States)

    Dubin, Krista; Callahan, Margaret K; Ren, Boyu; Khanin, Raya; Viale, Agnes; Ling, Lilan; No, Daniel; Gobourne, Asia; Littmann, Eric; Huttenhower, Curtis; Pamer, Eric G; Wolchok, Jedd D

    2016-01-01

    The composition of the intestinal microbiota influences the development of inflammatory disorders. However, associating inflammatory diseases with specific microbial members of the microbiota is challenging, because clinically detectable inflammation and its treatment can alter the microbiota's composition. Immunologic checkpoint blockade with ipilimumab, a monoclonal antibody that blocks cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) signalling, is associated with new-onset, immune-mediated colitis. Here we conduct a prospective study of patients with metastatic melanoma undergoing ipilimumab treatment and correlate the pre-inflammation faecal microbiota and microbiome composition with subsequent colitis development. We demonstrate that increased representation of bacteria belonging to the Bacteroidetes phylum is correlated with resistance to the development of checkpoint-blockade-induced colitis. Furthermore, a paucity of genetic pathways involved in polyamine transport and B vitamin biosynthesis is associated with an increased risk of colitis. Identification of these biomarkers may enable interventions to reduce the risk of inflammatory complications following cancer immunotherapy. PMID:26837003

  3. Social and ethical checkpoints for bottom-up synthetic biology, or protocells.

    Science.gov (United States)

    Bedau, Mark A; Parke, Emily C; Tangen, Uwe; Hantsche-Tangen, Brigitte

    2009-12-01

    An alternative to creating novel organisms through the traditional "top-down" approach to synthetic biology involves creating them from the "bottom up" by assembling them from non-living components; the products of this approach are called "protocells." In this paper we describe how bottom-up and top-down synthetic biology differ, review the current state of protocell research and development, and examine the unique ethical, social, and regulatory issues raised by bottom-up synthetic biology. Protocells have not yet been developed, but many expect this to happen within the next five to ten years. Accordingly, we identify six key checkpoints in protocell development at which particular attention should be given to specific ethical, social and regulatory issues concerning bottom-up synthetic biology, and make ten recommendations for responsible protocell science that are tied to the achievement of these checkpoints. PMID:19816801

  4. An Overview of the Spindle Assembly Checkpoint Status in Oral Cancer

    Science.gov (United States)

    Teixeira, José Henrique; Silva, Patrícia Manuela; Reis, Rita Margarida; Moura, Inês Moranguinho; Marques, Sandra; Fonseca, Joana; Monteiro, Luís Silva; Bousbaa, Hassan

    2014-01-01

    Abnormal chromosome number, or aneuploidy, is a common feature of human solid tumors, including oral cancer. Deregulated spindle assembly checkpoint (SAC) is thought as one of the mechanisms that drive aneuploidy. In normal cells, SAC prevents anaphase onset until all chromosomes are correctly aligned at the metaphase plate thereby ensuring genomic stability. Significantly, the activity of this checkpoint is compromised in many cancers. While mutations are rather rare, many tumors show altered expression levels of SAC components. Genomic alterations such as aneuploidy indicate a high risk of oral cancer and cancer-related mortality, and the molecular basis of these alterations is largely unknown. Yet, our knowledge on the status of SAC components in oral cancer remains sparse. In this review, we address the state of our knowledge regarding the SAC defects and the underlying molecular mechanisms in oral cancer, and discuss their therapeutic relevance, focusing our analysis on the core components of SAC and its target Cdc20. PMID:24995269

  5. Cloud object store for checkpoints of high performance computing applications using decoupling middleware

    Energy Technology Data Exchange (ETDEWEB)

    Bent, John M.; Faibish, Sorin; Grider, Gary

    2016-04-19

    Cloud object storage is enabled for checkpoints of high performance computing applications using a middleware process. A plurality of files, such as checkpoint files, generated by a plurality of processes in a parallel computing system are stored by obtaining said plurality of files from said parallel computing system; converting said plurality of files to objects using a log structured file system middleware process; and providing said objects for storage in a cloud object storage system. The plurality of processes may run, for example, on a plurality of compute nodes. The log structured file system middleware process may be embodied, for example, as a Parallel Log-Structured File System (PLFS). The log structured file system middleware process optionally executes on a burst buffer node.

  6. Dynein Light Intermediate Chain 2 Facilitates the Metaphase to Anaphase Transition by Inactivating the Spindle Assembly Checkpoint.

    Directory of Open Access Journals (Sweden)

    Sagar P Mahale

    Full Text Available The multi-functional molecular motor cytoplasmic dynein performs diverse essential roles during mitosis. The mechanistic importance of the dynein Light Intermediate Chain homologs, LIC1 and LIC2 is unappreciated, especially in the context of mitosis. LIC1 and LIC2 are believed to exist in distinct cytoplasmic dynein complexes as obligate subunits. LIC1 had earlier been reported to be required for metaphase to anaphase progression by inactivating the kinetochore-microtubule attachment-sensing arm of the spindle assembly checkpoint (SAC. However, the functional importance of LIC2 during mitosis remains elusive. Here we report prominent novel roles for the LIC2 subunit of cytoplasmic dynein in regulating the spindle assembly checkpoint. LIC2 depletion in mammalian cells led to prolonged metaphase arrest in the presence of an active SAC and also to stretched kinetochores, thus implicating it in SAC inactivation. Quantitative fluorescence microscopy of SAC components revealed accumulation of both attachment- and tension-sensing checkpoint proteins at metaphase kinetochores upon LIC2 depletion. These observations support a stronger and more diverse role in checkpoint inactivation for LIC2 in comparison to its close homolog LIC1. Our study uncovers a novel functional hierarchy during mitotic checkpoint inactivation between the closely related but homologous LIC subunits of cytoplasmic dynein. These subtle functional distinctions between dynein subpopulations could be exploited to study specific aspects of the spindle assembly checkpoint, which is a key mediator of fidelity in eukaryotic cell division.

  7. Dynein Light Intermediate Chain 2 Facilitates the Metaphase to Anaphase Transition by Inactivating the Spindle Assembly Checkpoint

    Science.gov (United States)

    Mahale, Sagar P.; Sharma, Amit; Mylavarapu, Sivaram V. S.

    2016-01-01

    The multi-functional molecular motor cytoplasmic dynein performs diverse essential roles during mitosis. The mechanistic importance of the dynein Light Intermediate Chain homologs, LIC1 and LIC2 is unappreciated, especially in the context of mitosis. LIC1 and LIC2 are believed to exist in distinct cytoplasmic dynein complexes as obligate subunits. LIC1 had earlier been reported to be required for metaphase to anaphase progression by inactivating the kinetochore-microtubule attachment-sensing arm of the spindle assembly checkpoint (SAC). However, the functional importance of LIC2 during mitosis remains elusive. Here we report prominent novel roles for the LIC2 subunit of cytoplasmic dynein in regulating the spindle assembly checkpoint. LIC2 depletion in mammalian cells led to prolonged metaphase arrest in the presence of an active SAC and also to stretched kinetochores, thus implicating it in SAC inactivation. Quantitative fluorescence microscopy of SAC components revealed accumulation of both attachment- and tension-sensing checkpoint proteins at metaphase kinetochores upon LIC2 depletion. These observations support a stronger and more diverse role in checkpoint inactivation for LIC2 in comparison to its close homolog LIC1. Our study uncovers a novel functional hierarchy during mitotic checkpoint inactivation between the closely related but homologous LIC subunits of cytoplasmic dynein. These subtle functional distinctions between dynein subpopulations could be exploited to study specific aspects of the spindle assembly checkpoint, which is a key mediator of fidelity in eukaryotic cell division. PMID:27441562

  8. Intestinal microbiome analyses identify melanoma patients at risk for checkpoint-blockade-induced colitis

    OpenAIRE

    Dubin, Krista; Callahan, Margaret K.; Ren, Boyu; Khanin, Raya; Viale, Agnes; Ling, Lilan; No, Daniel; Gobourne, Asia; Littmann, Eric; Huttenhower, Curtis; Pamer, Eric G.; Wolchok, Jedd D.

    2016-01-01

    The composition of the intestinal microbiota influences the development of inflammatory disorders. However, associating inflammatory diseases with specific microbial members of the microbiota is challenging, because clinically detectable inflammation and its treatment can alter the microbiota's composition. Immunologic checkpoint blockade with ipilimumab, a monoclonal antibody that blocks cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) signalling, is associated with new-onset, immune-med...

  9. CDC28, NETI, and HFII are required for checkpoints in Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    The involvement of SRM genes selected as genes affecting genetic stability and radiosensitivity in a cell cycle arrest under the action of damaging agents was studied. It was shown that the srm5/cdc28-srm, srm8/netI-srm, and srmI2/hfiI-srm mutations prevent checkpoint activation by DNA damage, particularly the G0/S (srm5, srm8), G1/S (srm5, srm8, srm12), S (srm8, srm12) and S/G2 (srm5) checkpoints. It seems that in budding yeast the CDC28, HFII/ADAI, and NETI genes mediate cellular response induced by DNA damage with checkpoint control. The well-known checkpoint-genes RAD9, RAD17, RAD24, and RAD53, and the genes CDC28, and NETI have been found to belong to one epistasis group named RAD9-group as regards cell sensitivity to γ radiation. An analysis of the radiosensitivity of double mutants has revealed that the mutation cdc-28-srm is hypostatic to each of mutations rad9Δ, and rad24Δ, and additive to rad17Δ. The mutation netI-srm is hypostatic to the mutations rad9Δ but additive to rad17Δ, rad24Δ, and rad53. The mutation hfiI-srm has an additive effect in compound with the mutations rad24Δ and rad9Δ. So, investigations of epistatic interactions have demonstrated a branched RAD9-dependent pathway. The analyzed genes can also participate in a minor mechanism involved in determining cell radiation sensitivity independently of the mentioned RAD9-dependent pathway

  10. Handoff Based Secure Checkpointing and Log Based Rollback Recovery for Mobile Hosts

    Directory of Open Access Journals (Sweden)

    Priyanka Dey and Suparna Biswas

    2012-10-01

    Full Text Available An efficient fault tolerant algorithm based on movement-based secure checkpointing and logging formobile computing system is proposed here. The recovery scheme proposed here combines independentcheckpointing and message logging. Here we consider mobility rate of the user in checkpointing so thatmobile host can manage recovery information such as checkpoints and logs properly so that a mobilehost takes less recovery time after failure. Mobile hosts save checkpoints when number of hand-offexceeds a predefined hand-off threshold value. Current approaches save logs in base station. But thisapproach maximizes recovery time if message passing frequency is large. If a mobile host saves log in itsown memory, recovery cost will be less because log retrieval time will be small after failure. But there isa probability of memory crash of a mobile host. In that case logs can not be retrieved if it is saved only inmobile node. If the failure is transient then logs can be retrieved from the memory of mobile node.Hence in this algorithm mobile hosts also save log in own memory and base station. In case of crashrecovery, log will be retrieved from base station and in case of transient failure recovery logs will beretrieved from mobile host. In this algorithm recovery probability is optimized and total recovery time isreduced in comparison to existing works. Logs are very small in size. Hence saving logs in mobile hostsdoes not cause much memory overhead. Hand-off threshold is a function of mobility rate, messagepassing frequency and failure rate of mobile hosts. This algorithm describes a secure check pointingtechnique as a method for providing fault tolerance while preventing information leakage through thecheckpoint data.

  11. Sudden Telomere Lengthening Triggers a Rad53-dependent Checkpoint in Saccharomyces cerevisiae

    OpenAIRE

    Viscardi, Valeria; Baroni, Enrico; Romano, Michele; Lucchini, Giovanna; Longhese, Maria Pia

    2003-01-01

    Telomeres are specialized functional complexes that ensure chromosome stability by protecting chromosome ends from fusions and degradation and avoiding chromosomal termini from being sensed as DNA breaks. Budding yeast Tel1 is required both for telomere metabolism and for a Rad53-dependent checkpoint responding to unprocessed double-strand breaks. We show that overexpression of a GAL1-TEL1 fusion causes transient telomere lengthening and activation of a Rad53-dependent...

  12. Efficient checkpointing schemes for depletion perturbation solutions on memory-limited architectures

    International Nuclear Information System (INIS)

    We describe a methodology for decreasing the memory footprint and machine I/O load associated with the need to access a forward solution during an adjoint solve. Specifically, we are interested in the depletion perturbation equations, where terms in the adjoint Bateman and transport equations depend on the forward flux solution. Checkpointing is the procedure of storing snapshots of the forward solution to disk and using these snapshots to recompute the parts of the forward solution that are necessary for the adjoint solve. For large problems, however, the storage cost of just a few copies of an angular flux vector can exceed the available RAM on the host machine. We propose a methodology that does not checkpoint the angular flux vector; instead, we write and store converged source moments, which are typically of a much lower dimension than the angular flux solution. This reduces the memory footprint and I/O load of the problem, but requires that we perform single sweeps to reconstruct flux vectors on demand. We argue that this trade-off is exactly the kind of algorithm that will scale on advanced, memory-limited architectures. We analyze the cost, in terms of FLOPS and memory footprint, of five checkpointing schemes. We also provide computational results that support the analysis and show that the memory-for-work trade off does improve time to solution. (authors)

  13. Efficient checkpointing schemes for depletion perturbation solutions on memory-limited architectures

    Energy Technology Data Exchange (ETDEWEB)

    Stripling, H. F.; Adams, M. L.; Hawkins, W. D. [Texas A and M University, Department of Nuclear Engineering, 3133 TAMU, College Station, TX 77843-3133 (United States)

    2013-07-01

    We describe a methodology for decreasing the memory footprint and machine I/O load associated with the need to access a forward solution during an adjoint solve. Specifically, we are interested in the depletion perturbation equations, where terms in the adjoint Bateman and transport equations depend on the forward flux solution. Checkpointing is the procedure of storing snapshots of the forward solution to disk and using these snapshots to recompute the parts of the forward solution that are necessary for the adjoint solve. For large problems, however, the storage cost of just a few copies of an angular flux vector can exceed the available RAM on the host machine. We propose a methodology that does not checkpoint the angular flux vector; instead, we write and store converged source moments, which are typically of a much lower dimension than the angular flux solution. This reduces the memory footprint and I/O load of the problem, but requires that we perform single sweeps to reconstruct flux vectors on demand. We argue that this trade-off is exactly the kind of algorithm that will scale on advanced, memory-limited architectures. We analyze the cost, in terms of FLOPS and memory footprint, of five checkpointing schemes. We also provide computational results that support the analysis and show that the memory-for-work trade off does improve time to solution. (authors)

  14. Immune checkpoint blockade therapy: The 2014 Tang prize in biopharmaceutical science

    Directory of Open Access Journals (Sweden)

    Ya-Shan Chen

    2015-02-01

    Full Text Available The first Tang Prize for Biopharmaceutical Science has been awarded to Prof. James P. Allison and Prof. Tasuku Honjo for their contributions leading to an entirely new way to treat cancer by blocking the molecules cytotoxic T lymphocyte-associated antigen 4 (CTLA-4 and programmed cell death protein 1 (PD-1 that turn off immune response. The treatment, called "immune checkpoint blockade therapy," has opened a new therapeutic era. Here the discoveries of the immune checkpoints and how they contribute to the maintenance of self-tolerance, as well as how to protect tissues from the excess immune responses causing damage are reviewed. The efforts made by Prof. Allison and Prof. Honjo for developing the most promising approaches to activate therapeutic antitumor immunity are also summarized. Since these certain immune checkpoint pathways appear to be one of the major mechanisms resulting in immune escape of tumors, the presence of anti-CTLA-4 and/or anti-PD-1 should contribute to removal of the inhibition signals for T cell activation. Subsequently, it will enhance specific T cell activation and, therefore, strengthen antitumor immunity.

  15. Immunologic checkpoints in cancer therapy: focus on the programmed death-1 (PD-1 receptor pathway

    Directory of Open Access Journals (Sweden)

    Momtaz P

    2014-11-01

    Full Text Available Parisa Momtaz,1,2 Michael A Postow1,2 1Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, USA; 2Weill Cornell Medical College, New York, NY, USA Abstract: T-lymphocytes have the potential to recognize cancer antigens as foreign and therefore eliminate them. However, immune checkpoints such as cytotoxic T-lymphocyte-associated antigen (CTLA-4 and programmed cell death (PD-1 receptor and its ligands (PD-L1, PD-L2 suppress the activity of T-lymphocytes. Advances in the understanding of immunology and its role in cancer have led to the development of immune checkpoint inhibitors that block CTLA-4 and PD-1 and result in durable responses in patients with a wide range of cancers. PD-1 and PD-L1 inhibitors are currently in many stages of clinical investigation, and the anti-PD-1 antibody, pembrolizumab, was recently approved by the US Food and Drug Administration. Many questions remain to be answered, such as the optimal administration schedule, biomarkers that associate with benefit, and potential for use of PD-1 agents in combination approaches. Nonetheless, immunotherapy with PD-1 blocking antibodies is now becoming an integral part in the management of cancer. Keyword: immune checkpoints, immunotherapy, programmed cell death protein-1, cytotoxic T-lymphocyte antigen 4

  16. Multicellular tumor spheroid models to explore cell cycle checkpoints in 3D

    International Nuclear Information System (INIS)

    MultiCellular Tumor Spheroid (MCTS) mimics the organization of a tumor and is considered as an invaluable model to study cancer cell biology and to evaluate new antiproliferative drugs. Here we report how the characteristics of MCTS in association with new technological developments can be used to explore the regionalization and the activation of cell cycle checkpoints in 3D. Cell cycle and proliferation parameters were investigated in Capan-2 spheroids by immunofluorescence staining, EdU incorporation and using cells engineered to express Fucci-red and -green reporters. We describe in details the changes in proliferation and cell cycle parameters during spheroid growth and regionalization. We report the kinetics and regionalized aspects of cell cycle arrest in response to checkpoint activation induced by EGF starvation, lovastatin treatment and etoposide-induced DNA damage. Our data present the power and the limitation of spheroids made of genetically modified cells to explore cell cycle checkpoints. This study paves the way for the investigation of molecular aspects and dynamic studies of the response to novel antiproliferative agents in 3D models

  17. RNF8 Transduces the DNA-Damage Signal Via Histone Ubiquitylation And Checkpoint Protein Assembly

    Energy Technology Data Exchange (ETDEWEB)

    Huen, M.S.Y.; Grant, R.; Manke, I.; Minn, K.; Yu, X.; Yaffe, M.B.; Chen, J.

    2009-06-01

    DNA-damage signaling utilizes a multitude of posttranslational modifiers as molecular switches to regulate cell-cycle checkpoints, DNA repair, cellular senescence, and apoptosis. Here we show that RNF8, a FHA/RING domain-containing protein, plays a critical role in the early DNA-damage response. We have solved the X-ray crystal structure of the FHA domain structure at 1.35 {angstrom}. We have shown that RNF8 facilitates the accumulation of checkpoint mediator proteins BRCA1 and 53BP1 to the damaged chromatin, on one hand through the phospho-dependent FHA domain-mediated binding of RNF8 to MDC1, on the other hand via its role in ubiquitylating H2AX and possibly other substrates at damage sites. Moreover, RNF8-depleted cells displayed a defective G2/M checkpoint and increased IR sensitivity. Together, our study implicates RNF8 as a novel DNA-damage-responsive protein that integrates protein phosphorylation and ubiquitylation signaling and plays a critical role in the cellular response to genotoxic stress.

  18. Quantitative mass spectrometry analysis reveals similar substrate consensus motif for human Mps1 kinase and Plk1.

    Directory of Open Access Journals (Sweden)

    Zhen Dou

    Full Text Available BACKGROUND: Members of the Mps1 kinase family play an essential and evolutionarily conserved role in the spindle assembly checkpoint (SAC, a surveillance mechanism that ensures accurate chromosome segregation during mitosis. Human Mps1 (hMps1 is highly phosphorylated during mitosis and many phosphorylation sites have been identified. However, the upstream kinases responsible for these phosphorylations are not presently known. METHODOLOGY/PRINCIPAL FINDINGS: Here, we identify 29 in vivo phosphorylation sites in hMps1. While in vivo analyses indicate that Aurora B and hMps1 activity are required for mitotic hyper-phosphorylation of hMps1, in vitro kinase assays show that Cdk1, MAPK, Plk1 and hMps1 itself can directly phosphorylate hMps1. Although Aurora B poorly phosphorylates hMps1 in vitro, it positively regulates the localization of Mps1 to kinetochores in vivo. Most importantly, quantitative mass spectrometry analysis demonstrates that at least 12 sites within hMps1 can be attributed to autophosphorylation. Remarkably, these hMps1 autophosphorylation sites closely resemble the consensus motif of Plk1, demonstrating that these two mitotic kinases share a similar substrate consensus. CONCLUSIONS/SIGNIFICANCE: hMps1 kinase is regulated by Aurora B kinase and its autophosphorylation. Analysis on hMps1 autophosphorylation sites demonstrates that hMps1 has a substrate preference similar to Plk1 kinase.

  19. Pyruvate kinase blood test

    Science.gov (United States)

    ... break down faster than normal, a condition called hemolytic anemia . This test helps diagnose pyruvate kinase deficiency (PKD) . ... Pa: Elsevier Saunders; 2011:chap 32. Gallagher PG. Hemolytic anemias: red cell membrane and metabolic defects In: Goldman ...

  20. The effect of heavy ion on DNA damage checkpoint, and the discovery of its sensitizing compounds

    International Nuclear Information System (INIS)

    We demonstrated that Schisandrin B (SchB) and persimmon leaf extract (PLE) inhibited activation of checkpoint signaling molecule of cancer cells by heavy ion radiation. Therefore, SchB and PLE raise the possibility of sensitizing agents for heavy ion cancer therapy. In the present study, we examined whether SchB and PLE can sensitize the effect of heavy ion on tumor growth by using xenograft study. The oral administration of SchB and PLE for 31 days did not clearly reduce a volume of tumor in Scid mice transplanted A549 human adenocarcinoma cells. Tumor growth was obviously inhibited by the irradiation of heavy ion (C290 MeV/u, spread-out Bragg peak (SOBP)). SchB and PLE reduced the tumor volume in 3 Gy heavy ion exposed mice, respectively. Similarly, we examined whether SchB and PLE can sensitize the effect of X-ray also. SchB did not sensitize the effect of X-ray. However, PLE reduced the tumor volume in 6 Gy X-ray exposed mice. These results indicated that tumor volume in heavy ion exposed mice was inhibited by SchB and PLE treatment through the inhibition of DNA damage checkpoint signaling pathway. On the other hand, SchB could not sensitize the effect of X-ray on tumor growth. These results suggest that the modulating effects of SchB and PLE on DNA damage checkpoint are targeting independent molecules. These mechanisms should be clarified in further study. (author)

  1. Acute renal allograft rejection after immune checkpoint inhibitor therapy for metastatic melanoma.

    Science.gov (United States)

    Spain, L; Higgins, R; Gopalakrishnan, K; Turajlic, S; Gore, M; Larkin, J

    2016-06-01

    Immune checkpoint inhibitors such as ipilimumab and nivolumab improve survival in patients with advanced melanoma and are increasingly available to clinicians for use in the clinic. Their safety in organ transplant recipients is not well defined but published case reports describing treatment with ipilimumab have not been complicated by graft rejection. No cases of anti-programmed cell death protein 1 administration are reported in this group. We describe a case of acute graft rejection in a kidney transplant recipient after treatment with nivolumab, after progression on ipilimumab. Potential factors increasing the risk of graft rejection in this case are discussed, in particular the contribution of nivolumab. PMID:26951628

  2. Human Embryonic Stem Cells Are Capable of Executing G1/S Checkpoint Activation

    Czech Academy of Sciences Publication Activity Database

    Bárta, Tomáš; Vinarský, Vladimír; Holubcová, Z.; Doležalová, Dáša; Verner, J.; Pospíšilová, Š.; Dvořák, Petr; Hampl, Aleš

    2010-01-01

    Roč. 28, č. 7 (2010), s. 1143-1152. ISSN 1066-5099 Grant ostatní: GA MŠk(CZ) MSM0021622430; GA MŠk(CZ) 1M0538; GA MZd(CZ) NS10439; GA MŠk(CZ) MUNIE/E/0118/2009; EC FP6(XE) LSHG-CT-2006-018739 Institutional research plan: CEZ:AV0Z50390512; CEZ:AV0Z50390703 Keywords : human embryonic stem cells * DNA damage * checkpoint activation Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 7.871, year: 2010

  3. Transparent Checkpoint-Restart for Hardware-Accelerated 3D Graphics

    OpenAIRE

    Nafchi, Samaneh Kazemi; Garg, Rohan; Cooperman, Gene

    2013-01-01

    Providing fault-tolerance for long-running GPU-intensive jobs requires application-specific solutions, and often involves saving the state of complex data structures spread among many graphics libraries. This work describes a mechanism for transparent GPU-independent checkpoint-restart of 3D graphics. The approach is based on a record-prune-replay paradigm: all OpenGL calls relevant to the graphics driver state are recorded; calls not relevant to the internal driver state as of the last graph...

  4. From Phosphosites to Kinases

    DEFF Research Database (Denmark)

    Munk, Stephanie; Refsgaard, Jan C; Olsen, Jesper V;

    2016-01-01

    Kinases play a pivotal role in propagating the phosphorylation-mediated signaling networks in living cells. With the overwhelming quantities of phosphoproteomics data being generated, the number of identified phosphorylation sites (phosphosites) is ever increasing. Often, proteomics investigations...... sequence motifs, mostly based on large scale in vivo and in vitro experiments. The context of the kinase and the phosphorylated proteins in a biological system is equally important for predicting association between the enzymes and substrates, an aspect that is also being tackled with available...

  5. DNA damage-induced metaphase I arrest is mediated by the spindle assembly checkpoint and maternal age.

    Science.gov (United States)

    Marangos, Petros; Stevense, Michelle; Niaka, Konstantina; Lagoudaki, Michaela; Nabti, Ibtissem; Jessberger, Rolf; Carroll, John

    2015-01-01

    In mammalian oocytes DNA damage can cause chromosomal abnormalities that potentially lead to infertility and developmental disorders. However, there is little known about the response of oocytes to DNA damage. Here we find that oocytes with DNA damage arrest at metaphase of the first meiosis (MI). The MI arrest is induced by the spindle assembly checkpoint (SAC) because inhibiting the SAC overrides the DNA damage-induced MI arrest. Furthermore, this MI checkpoint is compromised in oocytes from aged mice. These data lead us to propose that the SAC is a major gatekeeper preventing the progression of oocytes harbouring DNA damage. The SAC therefore acts to integrate protection against both aneuploidy and DNA damage by preventing production of abnormal mature oocytes and subsequent embryos. Finally, we suggest escaping this DNA damage checkpoint in maternal ageing may be one of the causes of increased chromosome anomalies in oocytes and embryos from older mothers. PMID:26522734

  6. Phosphatidylinositol kinase from rabbit reticulocytes

    International Nuclear Information System (INIS)

    Phosphatidylinositol (PI) kinase was isolated from the postribosomal supernatant of rabbit reticulocytes. This activity was identified by the formation of a product that comigrated with phosphatidylinositol-4-phosphate (PIP) when purified PI was phosphorylated in the presence of [32P]ATP and Mg2+. Three major peaks of PI kinase activity were resolved by chromatography on DEAE-cellulose. The first peak eluted at 50-100 mM NaCl together with several serine protein kinases, casein kinase (CK) I and protease activated kinase (PAK) I and II. The PI kinase was subsequently separated from the protein kinases by chromatography on phosphocellulose. The second peak eluted at 125-160 mM NaCl and contained another lipid kinase activity that produced a product which comigrated with phosphatidic acid on thin layer chromatography. The third peak, which eluted at 165-200 mM NaCl, partly comigrated with casein kinase (CK) II and an active protein kinase(s) which phosphorylated mixed histone and histone I. CK II and the histone kinase activities were also separated by chromatography on phosphocelluslose. The different forms of PI kinase were characterized and compared with respect to substrate and salt requirements

  7. 有丝分裂关键激酶抑制剂的研究进展%Progress on the research of key kinase inhibitors in mitosis

    Institute of Scientific and Technical Information of China (English)

    陈葆峰; 解鸿波; 沙宇; 程卯生

    2012-01-01

    目的 综述有丝分裂关键激酶抑制剂近年来的研究进展.方法 根据已报道的有丝分裂中关键激酶抑制剂的文献,将对有丝分裂过程中与肿瘤发生联系密切的激酶抑制剂,如Aurora激酶抑制剂、CDK(cyclin-dependent kinase)激酶抑制剂、PLK(Polo-like kinase)激酶抑制剂、CHK(check-point kinase)激酶抑制剂等目前的研究进展进行综述.结果 有丝分裂关键激酶抑制剂已在临床前研究及临床研究中显示出很好的抗肿瘤活性.结论 随着研究的不断深入,有丝分裂关键激酶抑制剂将在肿瘤治疗中发挥更大的作用.%Objective To review the recent progress on the research of key kinase inhibitors in mitosis. Methods According to the references to the key kinase inhibitors in mitosis reported, the kinase inhibitors were introduced closely related to the occurrence of the cancer in the progress of mitosis, such as Aurora kinase in- . hibitors, CDK (cyclin-dependent kinase) inhibitors, PLK (Polo-like kinase) inhibitors and CHK (checkpoint kinase)inhibitors. Results The potent anti-tumor activity of key kinase inhibitors in mitosis had been revealed in the preclinical and clinical research. Conclusions With the further research,key kinase inhibitors in mitosis shows more significant roles in the therapy of cancer.

  8. The Geography of Deterrence: Exploring the Small Area Effects of Sobriety Checkpoints on Alcohol-Impaired Collision Rates within a City

    Science.gov (United States)

    Nunn, Samuel; Newby, William

    2011-01-01

    This article examines alcohol-impaired collision metrics around nine sobriety checkpoint locations in Indianapolis, Indiana, before and after implementation of 22 checkpoints, using a pre/post examination, a pre/post nonequivalent comparison group analysis, and an interrupted time series approach. Traffic safety officials used geographical…

  9. Tumor-suppressor genes, cell cycle regulatory checkpoints, and the skin

    Directory of Open Access Journals (Sweden)

    Ana Maria Abreu Velez

    2015-01-01

    Full Text Available The cell cycle (or cell-division cycle is a series of events that take place in a cell, leading to its division and duplication. Cell division requires cell cycle checkpoints (CPs that are used by the cell to both monitor and regulate the progress of the cell cycle. Tumor-suppressor genes (TSGs or antioncogenes are genes that protect the cell from a single event or multiple events leading to cancer. When these genes mutate, the cell can progress to a cancerous state. We aimed to perform a narrative review, based on evaluation of the manuscripts published in MEDLINE-indexed journals using the Medical Subject Headings (MeSH terms "tumor suppressor′s genes," "skin," and "cell cycle regulatory checkpoints." We aimed to review the current concepts regarding TSGs, CPs, and their association with selected cutaneous diseases. It is important to take into account that in some cell cycle disorders, multiple genetic abnormalities may occur simultaneously. These abnormalities may include intrachromosomal insertions, unbalanced division products, recombinations, reciprocal deletions, and/or duplication of the inserted segments or genes; thus, these presentations usually involve several genes. Due to their complexity, these disorders require specialized expertise for proper diagnosis, counseling, personal and family support, and genetic studies. Alterations in the TSGs or CP regulators may occur in many benign skin proliferative disorders, neoplastic processes, and genodermatoses.

  10. Anti-TNF-refractory colitis after checkpoint inhibitor therapy: Possible role of CMV-mediated immunopathogenesis.

    Science.gov (United States)

    Lankes, Katharina; Hundorfean, Gheorghe; Harrer, Thomas; Pommer, Ansgar J; Agaimy, Abbas; Angelovska, Irena; Tajmir-Riahi, Azadeh; Göhl, Jonas; Schuler, Gerold; Neurath, Markus F; Hohenberger, Werner; Heinzerling, Lucie

    2016-06-01

    Immune-related adverse events (irAEs) induced by checkpoint inhibitors are well known. Since fatal outcomes have been reported early detection and adequate management are crucial. In particular, colitis is frequently observed and can result in intestinal perforation. This is the first report of an autoimmune colitis that was treated according to algorithms but became resistant due to a CMV reactivation. The 32-y-old male patient with metastatic melanoma treated within an anti-PD-1/ipilimumab combination study developed severe immune-mediated colitis (CTCAE grade 3) with up to 18 watery stools per day starting 2 weeks after treatment initiation. After improving upon therapy with immunosuppressive treatment (high dose steroids and infliximab) combined with parenteral nutrition diarrhea again exacerbated. Additionally, the patient had asymptomatic grade 3 CTCAE amylase and lipase elevation. Colitis was monitored by weekly endoscopies and colon biopsies were analyzed histologically with CMV staining, multi-epitope ligand cartography (MELC) and qRT-PCR for inflammatory genes. In the course, CMV reactivation was detected in the colon and treated with antiviral medication in parallel to a reduction of corticosteroids. Subsequently, symptoms improved. The patient showed a complete response for 2 y now including regression of bone metastases. CMV reactivation under checkpoint inhibitor therapy in combination with immunosuppressive treatment for autoimmune side effects has to be considered in these patients and if present treated. Potentially, CMV reactivation is underdiagnosed. Treatment algorithms should include CMV diagnostics. PMID:27471608

  11. A2aR antagonists: Next generation checkpoint blockade for cancer immunotherapy

    Directory of Open Access Journals (Sweden)

    Robert D. Leone

    2015-01-01

    Full Text Available The last several years have witnessed exciting progress in the development of immunotherapy for the treatment of cancer. This has been due in great part to the development of so-called checkpoint blockade. That is, antibodies that block inhibitory receptors such as CTLA-4 and PD-1 and thus unleash antigen-specific immune responses against tumors. It is clear that tumors evade the immune response by usurping pathways that play a role in negatively regulating normal immune responses. In this regard, adenosine in the immune microenvironment leading to the activation of the A2a receptor has been shown to represent one such negative feedback loop. Indeed, the tumor microenvironment has relatively high concentrations of adenosine. To this end, blocking A2a receptor activation has the potential to markedly enhance anti-tumor immunity in mouse models. This review will present data demonstrating the ability of A2a receptor blockade to enhance tumor vaccines, checkpoint blockade and adoptive T cell therapy. Also, as several recent studies have demonstrated that under certain conditions A2a receptor blockade can enhance tumor progression, we will also explore the complexities of adenosine signaling in the immune response. Despite important nuances to the A2a receptor pathway that require further elucidation, studies to date strongly support the development of A2a receptor antagonists (some of which have already been tested in phase III clinical trials for Parkinson Disease as novel modalities in the immunotherapy armamentarium.

  12. Estimated Interval-Based Checkpointing (EIC on Spot Instances in Cloud Computing

    Directory of Open Access Journals (Sweden)

    Daeyong Jung

    2014-01-01

    Full Text Available In cloud computing, users can rent computing resources from service providers according to their demand. Spot instances are unreliable resources provided by cloud computing services at low monetary cost. When users perform tasks on spot instances, there is an inevitable risk of failures that causes the delay of task execution time, resulting in a serious deterioration of quality of service (QoS. To deal with the problem on spot instances, we propose an estimated interval-based checkpointing (EIC using weighted moving average. Our scheme sets the thresholds of price and execution time based on history. Whenever the actual price and the execution time cross over the thresholds, the system saves the state of spot instances. The Bollinger Bands is adopted to inform the ranges of estimated cost and execution time for user's discretion. The simulation results reveal that, compared to the HBC and REC, the EIC reduces the number of checkpoints and the rollback time. Consequently, the task execution time is decreased with EIC by HBC and REC. The EIC also provides the benefit of the cost reduction by HBC and REC, on average. We also found that the actual cost and execution time fall within the estimated ranges suggested by the Bollinger Bands.

  13. The impact of aviation checkpoint queues on optimizing security screening effectiveness

    International Nuclear Information System (INIS)

    Passenger screening at aviation security checkpoints is a critical component in protecting airports and aircraft from terrorist threats. Recent developments in screening device technology have increased the ability to detect these threats; however, the average amount of time it takes to screen a passenger still remains a concern. This paper models the queueing process for a multi-level airport checkpoint security system, where multiple security classes are formed through subsets of specialized screening devices. An optimal static assignment policy is obtained which minimizes the steady-state expected amount of time a passenger spends in the security system. Then, an optimal dynamic assignment policy is obtained through a transient analysis that balances the expected number of true alarms with the expected amount of time a passenger spends in the security system. Performance of a two-class system is compared to that of a selective security system containing primary and secondary levels of screening. The key contribution is that the resulting optimal assignment policies increase security and passenger throughput by efficiently and effectively utilizing available screening resources.

  14. Kinase Inhibitors from Marine Sponges

    Directory of Open Access Journals (Sweden)

    Ana Zivanovic

    2011-10-01

    Full Text Available Protein kinases play a critical role in cell regulation and their deregulation is a contributing factor in an increasing list of diseases including cancer. Marine sponges have yielded over 70 novel compounds to date that exhibit significant inhibitory activity towards a range of protein kinases. These compounds, which belong to diverse structural classes, are reviewed herein, and ordered based upon the kinase that they inhibit. Relevant synthetic studies on the marine natural product kinase inhibitors have also been included.

  15. Microcephalin and pericentrin regulate mitotic entry via centrosome-associated Chk1

    DEFF Research Database (Denmark)

    Tibelius, Alexandra; Marhold, Joachim; Zentgraf, Hanswalter;

    2009-01-01

    Primary microcephaly, Seckel syndrome, and microcephalic osteodysplastic primordial dwarfism type II (MOPD II) are disorders exhibiting marked microcephaly, with small brain sizes reflecting reduced neuron production during fetal life. Although primary microcephaly can be caused by mutations...

  16. RNA-dependent protein kinase (PKR) depletes nutrients, inducing phosphorylation of AMP-activated kinase in lung cancer.

    Science.gov (United States)

    Guo, Chengcheng; Hao, Chuncheng; Shao, RuPing; Fang, Bingliang; Correa, Arlene M; Hofstetter, Wayne L; Roth, Jack A; Behrens, Carmen; Kalhor, Neda; Wistuba, Ignacio I; Swisher, Stephen G; Pataer, Apar

    2015-05-10

    We have demonstrated that RNA-dependent protein kinase (PKR) and its downstream protein p-eIF2α are independent prognostic markers for overall survival in lung cancer. In the current study, we further investigate the interaction between PKR and AMPK in lung tumor tissue and cancer cell lines. We examined PKR protein expression in 55 frozen primary lung tumor tissues by Western blotting and analyzed the association between PKR expression and expression of 139 proteins on tissue samples examined previously by Reverse Phase Protein Array (RPPA) from the same 55 patients. We observed that biomarkers were either positively (phosphorylated AMP-activated kinase(T172) [p-AMPK]) or negatively (insulin receptor substrate 1, meiotic recombination 11, ATR interacting protein, telomerase, checkpoint kinase 1, and cyclin E1) correlated with PKR. We further confirmed that induction of PKR with expression vectors in lung cancer cells causes activation of the AMPK protein independent of the LKB1, TAK1, and CaMKKβ pathway. We found that PKR causes nutrient depletion, which increases AMP levels and decreases ATP levels, causing AMPK phosphorylation. We further demonstrated that inhibiting AMPK expression with compound C or siRNA enhanced PKR-mediated cell death. We next explored the combination of PKR and p-AMPK expression in NSCLC patients and observed that expression of p-AMPK predicted a poor outcome for adenocarcinoma patients with high PKR expression and a better prognosis for those with low PKR expression. These findings were consistent with our in vitro results. AMPK might rescue cells facing metabolic stresses, such as ATP depletion caused by PKR. Our data indicate that PKR causes nutrient depletion, which induces the phosphorylation of AMPK. AMPK might act as a protective response to metabolic stresses, such as nutrient deprivation. PMID:25798539

  17. Tyrosine kinases in rheumatoid arthritis

    Directory of Open Access Journals (Sweden)

    Kobayashi Akiko

    2011-08-01

    Full Text Available Abstract Rheumatoid arthritis (RA is an inflammatory, polyarticular joint disease. A number of cellular responses are involved in the pathogenesis of rheumatoid arthritis, including activation of inflammatory cells and cytokine expression. The cellular responses involved in each of these processes depends on the specific signaling pathways that are activated; many of which include protein tyrosine kinases. These pathways include the mitogen-activated protein kinase pathway, Janus kinases/signal transducers and activators transcription pathway, spleen tyrosine kinase signaling, and the nuclear factor κ-light-chain-enhancer of activated B cells pathway. Many drugs are in development to target tyrosine kinases for the treatment of RA. Based on the number of recently published studies, this manuscript reviews the role of tyrosine kinases in the pathogenesis of RA and the potential role of kinase inhibitors as new therapeutic strategies of RA.

  18. Mad2 binding to Mad1 and Cdc20, rather than oligomerization, is required for the spindle checkpoint

    DEFF Research Database (Denmark)

    Sironi, L; Melixetian, M; Faretta, M;

    2001-01-01

    Mad2 is a key component of the spindle checkpoint, a device that controls the fidelity of chromosome segregation in mitosis. The ability of Mad2 to form oligomers in vitro has been correlated with its ability to block the cell cycle upon injection into Xenopus embryos. Here we show that Mad2 forms...

  19. Wip1 phosphatase is associated with chromatin and dephosphorylates gammaH2AX to promote checkpoint inhibition

    Czech Academy of Sciences Publication Activity Database

    Macůrek, Libor; Lindqvist, A.; Voets, O.; Kool, J.; Vos, H.R.; Medema, R.H.

    2010-01-01

    Roč. 29, č. 15 (2010), s. 2281-2291. ISSN 0950-9232 R&D Projects: GA ČR GPP305/10/P420 Institutional research plan: CEZ:AV0Z50520514 Keywords : DNA damage * checkpoint * phosphatase Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 7.414, year: 2010

  20. Killing the umpire: cooperative defects in mitotic checkpoint and BRCA2 genes on the road to transformation

    International Nuclear Information System (INIS)

    Recent findings from mouse models of BRCA2 genetic lesions have provided intriguing insights and important questions concerning modes of tumor development in familial breast and ovarian cancers. Fibroblasts from mice homozygous for the BRCA2Tr allele grow poorly and display an array of chromosomal abnormalities that are consistent with a role for BRCA2 in DNA repair. This growth defect can be overcome and cellular transformation promoted by the expression of defective, dominant negative alleles of p53 and of the mitotic checkpoint gene Bub1, both of which are known to induce chromosome instability. These findings are mirrored in the genetic lesions sustained in tumors found in the rare BRCA2Tr/Trmice that survive to adulthood, which include defects in p53 as well as the mitotic checkpoint proteins Bub1 and Mad3L. Together, these data hint that tumors in these mice evolve from an unusually intense selective pressure to remove DNA damage checkpoints, which in turn might be facilitated by chromosomal abolition of mitotic checkpoints and the consequent increase in shuffling of genetic information. How these genetic lesions co-operate to yield transformed cells and how these data relate to BRCA1 and BRCA2 defects in the human population are important questions raised by this work

  1. Oncoprotein protein kinase

    Energy Technology Data Exchange (ETDEWEB)

    Karin, Michael (San Diego, CA); Hibi, Masahiko (San Diego, CA); Lin, Anning (La Jolla, CA); Davis, Roger (Princeton, MA); Derijard, Benoit (Shrewsbury, MA)

    2003-02-04

    An isolated polypeptide (JNK) characterized by having a molecular weight of 46kD as determined by reducing SDS-PAGE, having serine and threonine kinase activity, phosphorylating the c-Jun N-terminal activation domain and polynucleotide sequences and method of detection of JNK are provided herein. JNK phosphorylates c-Jun N-terminal activation domain which affects gene expression from AP-1 sites.

  2. Kinase-Catalyzed Biotinylation

    OpenAIRE

    Senevirathne, Chamara; Green, Keith D.; Pflum, Mary Kay H.

    2012-01-01

    Kinase-catalyzed protein phosphorylation plays an essential role in a variety of biological processes. Methods to detect phosphoproteins and phosphopeptides in cellular mixtures will aid in cell biological and signaling research. Our laboratory recently discovered the utility of γ-modified ATP analogues as tools for studying phosphorylation. Specifically, ATP-biotin can be used for labeling and visualizing phosphoproteins from cell lysates. Because the biotin tag is suitable for protein detec...

  3. Persistent activation of DNA damage signaling in response to complex mixtures of PAHs in air particulate matter

    International Nuclear Information System (INIS)

    Complex mixtures of polycyclic aromatic hydrocarbons (PAHs) are present in air particulate matter (PM) and have been associated with many adverse human health effects including cancer and respiratory disease. However, due to their complexity, the risk of exposure to mixtures is difficult to estimate. In the present study the effects of binary mixtures of benzo[a]pyrene (BP) and dibenzo[a,l]pyrene (DBP) and complex mixtures of PAHs in urban air PM extracts on DNA damage signaling was investigated. Applying a statistical model to the data we observed a more than additive response for binary mixtures of BP and DBP on activation of DNA damage signaling. Persistent activation of checkpoint kinase 1 (Chk1) was observed at significantly lower BP equivalent concentrations in air PM extracts than BP alone. Activation of DNA damage signaling was also more persistent in air PM fractions containing PAHs with more than four aromatic rings suggesting larger PAHs contribute a greater risk to human health. Altogether our data suggests that human health risk assessment based on additivity such as toxicity equivalency factor scales may significantly underestimate the risk of exposure to complex mixtures of PAHs. The data confirms our previous findings with PAH-contaminated soil (Niziolek-Kierecka et al., 2012) and suggests a possible role for Chk1 Ser317 phosphorylation as a biological marker for future analyses of complex mixtures of PAHs. -- Highlights: ► Benzo[a]pyrene (BP), dibenzo[a,l]pyrene (DBP) and air PM PAH extracts were compared. ► Binary mixture of BP and DBP induced a more than additive DNA damage response. ► Air PM PAH extracts were more potent than toxicity equivalency factor estimates. ► Larger PAHs (> 4 rings) contribute more to the genotoxicity of PAHs in air PM. ► Chk1 is a sensitive marker for persistent activation of DNA damage signaling from PAH mixtures.

  4. Application of a new dual localization-affinity purification tag reveals novel aspects of protein kinase biology in Aspergillus nidulans.

    Directory of Open Access Journals (Sweden)

    Colin P De Souza

    Full Text Available Filamentous fungi occupy critical environmental niches and have numerous beneficial industrial applications but devastating effects as pathogens and agents of food spoilage. As regulators of essentially all biological processes protein kinases have been intensively studied but how they regulate the often unique biology of filamentous fungi is not completely understood. Significant understanding of filamentous fungal biology has come from the study of the model organism Aspergillus nidulans using a combination of molecular genetics, biochemistry, cell biology and genomic approaches. Here we describe dual localization-affinity purification (DLAP tags enabling endogenous N or C-terminal protein tagging for localization and biochemical studies in A. nidulans. To establish DLAP tag utility we endogenously tagged 17 protein kinases for analysis by live cell imaging and affinity purification. Proteomic analysis of purifications by mass spectrometry confirmed association of the CotA and NimXCdk1 kinases with known binding partners and verified a predicted interaction of the SldABub1/R1 spindle assembly checkpoint kinase with SldBBub3. We demonstrate that the single TOR kinase of A. nidulans locates to vacuoles and vesicles, suggesting that the function of endomembranes as major TOR cellular hubs is conserved in filamentous fungi. Comparative analysis revealed 7 kinases with mitotic specific locations including An-Cdc7 which unexpectedly located to mitotic spindle pole bodies (SPBs, the first such localization described for this family of DNA replication kinases. We show that the SepH septation kinase locates to SPBs specifically in the basal region of apical cells in a biphasic manner during mitosis and again during septation. This results in gradients of SepH between G1 SPBs which shift along hyphae as each septum forms. We propose that SepH regulates the septation initiation network (SIN specifically at SPBs in the basal region of G1 cells and that

  5. The role of vitamin D in asthma.

    Science.gov (United States)

    Luong, Khanh vinh quoc; Nguyen, Lan Thi Hoàng

    2012-04-01

    Vitamin D metabolites are important immune-modulatory hormones and are able to suppress Th2-mediated allergic airway disease. Some genetic factors that may contribute to asthma are regulated by vitamin D, such as vitamin D receptor (VDR), human leukocyte antigen genes (HLA), human Toll-like receptors (TLR), matrix metalloproteinases (MMPs), a disintegrin and metalloprotein-33 (ADAM-33), and poly(ADP-ribosyl) polymerase- 1 (PARP-1). Vitamin D has also been implicated in asthma through its effects on the obesity, bacillus Calmettee Guérin (BCG) vaccination and high vitamin D level, vitamin D supplement, checkpoint protein kinase 1 (Chk1), plasminogen activator inhibitor-1 (PAI-1) and gamma delta T cells (gdT). Vitamin D plays a role in asthma and exerts its action through either genomic and/or non-genomic ways. PMID:22532985

  6. Toxicities of the anti-PD-1 and anti-PD-L1 immune checkpoint antibodies.

    Science.gov (United States)

    Naidoo, J; Page, D B; Li, B T; Connell, L C; Schindler, K; Lacouture, M E; Postow, M A; Wolchok, J D

    2015-12-01

    Immune checkpoint antibodies that augment the programmed cell death protein 1 (PD-1)/PD-L1 pathway have demonstrated antitumor activity across multiple malignancies, and gained recent regulatory approval as single-agent therapy for the treatment of metastatic malignant melanoma and nonsmall-cell lung cancer. Knowledge of toxicities associated with PD-1/PD-L1 blockade, as well as effective management algorithms for these toxicities, is pivotal in order to optimize clinical efficacy and safety. In this article, we review selected published and presented clinical studies investigating single-agent anti-PD-1/PD-L1 therapy and trials of combination approaches with other standard anticancer therapies, in multiple tumor types. We summarize the key adverse events reported in these studies and their management algorithms. PMID:26371282

  7. Clonal neoantigens elicit T cell immunoreactivity and sensitivity to immune checkpoint blockade.

    Science.gov (United States)

    McGranahan, Nicholas; Furness, Andrew J S; Rosenthal, Rachel; Ramskov, Sofie; Lyngaa, Rikke; Saini, Sunil Kumar; Jamal-Hanjani, Mariam; Wilson, Gareth A; Birkbak, Nicolai J; Hiley, Crispin T; Watkins, Thomas B K; Shafi, Seema; Murugaesu, Nirupa; Mitter, Richard; Akarca, Ayse U; Linares, Joseph; Marafioti, Teresa; Henry, Jake Y; Van Allen, Eliezer M; Miao, Diana; Schilling, Bastian; Schadendorf, Dirk; Garraway, Levi A; Makarov, Vladimir; Rizvi, Naiyer A; Snyder, Alexandra; Hellmann, Matthew D; Merghoub, Taha; Wolchok, Jedd D; Shukla, Sachet A; Wu, Catherine J; Peggs, Karl S; Chan, Timothy A; Hadrup, Sine R; Quezada, Sergio A; Swanton, Charles

    2016-03-25

    As tumors grow, they acquire mutations, some of which create neoantigens that influence the response of patients to immune checkpoint inhibitors. We explored the impact of neoantigen intratumor heterogeneity (ITH) on antitumor immunity. Through integrated analysis of ITH and neoantigen burden, we demonstrate a relationship between clonal neoantigen burden and overall survival in primary lung adenocarcinomas. CD8(+)tumor-infiltrating lymphocytes reactive to clonal neoantigens were identified in early-stage non-small cell lung cancer and expressed high levels of PD-1. Sensitivity to PD-1 and CTLA-4 blockade in patients with advanced NSCLC and melanoma was enhanced in tumors enriched for clonal neoantigens. T cells recognizing clonal neoantigens were detectable in patients with durable clinical benefit. Cytotoxic chemotherapy-induced subclonal neoantigens, contributing to an increased mutational load, were enriched in certain poor responders. These data suggest that neoantigen heterogeneity may influence immune surveillance and support therapeutic developments targeting clonal neoantigens. PMID:26940869

  8. Meiosis I in Xenopus oocytes is not error-prone despite lacking spindle assembly checkpoint.

    Science.gov (United States)

    Liu, Dandan; Shao, Hua; Wang, Hongmei; Liu, X Johné

    2014-01-01

    The spindle assembly checkpoint, SAC, is a surveillance mechanism to control the onset of anaphase during cell division. SAC prevents anaphase initiation until all chromosome pairs have achieved bipolar attachment and aligned at the metaphase plate of the spindle. In doing so, SAC is thought to be the key mechanism to prevent chromosome nondisjunction in mitosis and meiosis. We have recently demonstrated that Xenopus oocyte meiosis lacks SAC control. This prompted the question of whether Xenopus oocyte meiosis is particularly error-prone. In this study, we have karyotyped a total of 313 Xenopus eggs following in vitro oocyte maturation. We found no hyperploid egg, out of 204 metaphase II eggs with countable chromosome spreads. Therefore, chromosome nondisjunction is very rare during Xenopus oocyte meiosis I, despite the lack of SAC. PMID:24646611

  9. Clonal neoantigens elicit T cell immunoreactivity and sensitivity to immune checkpoint blockade

    Science.gov (United States)

    McGranahan, Nicholas; Furness, Andrew J. S.; Rosenthal, Rachel; Ramskov, Sofie; Lyngaa, Rikke; Saini, Sunil Kumar; Jamal-Hanjani, Mariam; Wilson, Gareth A.; Birkbak, Nicolai J.; Hiley, Crispin T.; Watkins, Thomas B. K.; Shafi, Seema; Murugaesu, Nirupa; Mitter, Richard; Akarca, Ayse U.; Linares, Joseph; Marafioti, Teresa; Henry, Jake Y.; Van Allen, Eliezer M.; Miao, Diana; Schilling, Bastian; Schadendorf, Dirk; Garraway, Levi A.; Makarov, Vladimir; Rizvi, Naiyer A.; Snyder, Alexandra; Hellmann, Matthew D.; Merghoub, Taha; Wolchok, Jedd D.; Shukla, Sachet A.; Wu, Catherine J.; Peggs, Karl S.; Chan, Timothy A.; Hadrup, Sine R.; Quezada, Sergio A.; Swanton, Charles

    2016-01-01

    As tumors grow, they acquire mutations, some of which create neoantigens that influence the response of patients to immune checkpoint inhibitors. We explored the impact of neoantigen intratumor heterogeneity (ITH) on antitumor immunity. Through integrated analysis of ITH and neoantigen burden, we demonstrate a relationship between clonal neoantigen burden and overall survival in primary lung adenocarcinomas. CD8+ tumor-infiltrating lymphocytes reactive to clonal neoantigens were identified in early-stage non–small cell lung cancer and expressed high levels of PD-1. Sensitivity to PD-1 and CTLA-4 blockade in patients with advanced NSCLC and melanoma was enhanced in tumors enriched for clonal neoantigens. T cells recognizing clonal neoantigens were detectable in patients with durable clinical benefit. Cytotoxic chemotherapy–induced subclonal neoantigens, contributing to an increased mutational load, were enriched in certain poor responders. These data suggest that neoantigen heterogeneity may influence immune surveillance and support therapeutic developments targeting clonal neoantigens. PMID:26940869

  10. Checkpoint and Replication Oriented Fault Tolerant Mechanism for MapReduce Framework

    Directory of Open Access Journals (Sweden)

    Yang Liu

    2013-09-01

    Full Text Available MapReduce is an emerging programming paradigm and an associated implementation for processing and generating big data which has been widely applied in data-intensive systems. In cloud environment, node and task failure is no longer accidental but a common feature of large-scale systems. In MapReduce framework, although the rescheduling based fault-tolerant method is simple to implement, it failed to fully consider the location of distributed data, the computation and storage overhead. Thus, a single node failure will increase the completion time dramatically. In this paper, a Checkpoint and Replication Oriented Fault Tolerant scheduling algorithm (CROFT is proposed, which takes both task and node failure into consideration. Preliminary experiments show that with less storage and network overhead. CROFT will significantly reduce the completion time at failure time, and the overall performance of MapReduce can be improved at least over 30% than original mechanism in Hadoop.  

  11. Chromosome 17p deletion in human medulloblastoma: a missing checkpoint in the Hedgehog pathway.

    Science.gov (United States)

    De Smaele, Enrico; Di Marcotullio, Lucia; Ferretti, Elisabetta; Screpanti, Isabella; Alesse, Edoardo; Gulino, Alberto

    2004-10-01

    Although deregulation of Hedgehog signalling is considered to play a crucial oncogenic role and commonly occurrs in medulloblastoma, genetic lesions in components of this pathway are observed in a minority of cases. The recent identification of a novel putative tumor suppressor (REN(KCTD11)) on chromosome 17p13.2, a region most frequently lost in human medulloblastoma, highlights the role of allelic deletion of the gene in this brain malignancy, leading to the loss of growth inhibitory activity via suppression of Gli-dependent activation of Hedgehog target genes. The presence on 17p13 of another tumor suppressor gene (p53) whose inactivation cooperates with Hedgehog pathway for medulloblastoma formation, suggests that 17p deletion unveils haploinsufficiency conditions leading to abrogation of either direct and indirect checkpoints of Hedgehog signalling in cancer. PMID:15467454

  12. Regulation of Autophagy by Kinases

    International Nuclear Information System (INIS)

    Autophagy is a process of self-degradation that maintains cellular viability during periods of metabolic stress. Although autophagy is considered a survival mechanism when faced with cellular stress, extensive autophagy can also lead to cell death. Aberrations in autophagy are associated with several diseases, including cancer. Therapeutic exploitation of this process requires a clear understanding of its regulation. Although the core molecular components involved in the execution of autophagy are well studied there is limited information on how cellular signaling pathways, particularly kinases, regulate this complex process. Protein kinases are integral to the autophagy process. Atg1, the first autophagy-related protein identified, is a serine/threonine kinase and it is regulated by another serine/threonine kinase mTOR. Emerging studies suggest the participation of many different kinases in regulating various components/steps of this catabolic process. This review focuses on the regulation of autophagy by several kinases with particular emphasis on serine/threonine protein kinases such as mTOR, AMP-activated protein kinase, Akt, mitogen-activated protein kinase (ERK, p38 and JNK) and protein kinase C that are often deregulated in cancer and are important therapeutic targets

  13. Immune checkpoint inhibitors enhance cytotoxicity of cytokine-induced killer cells against human myeloid leukaemic blasts.

    Science.gov (United States)

    Poh, Su Li; Linn, Yeh Ching

    2016-05-01

    We studied whether blockade of inhibitory receptors on cytokine-induced killer (CIK) cells by immune checkpoint inhibitors could increase its anti-tumour potency against haematological malignancies. CIK cultures were generated from seven normal donors and nine patients with acute myeloid leukaemia (AML), acute lymphoblastic leukaemia (ALL) or multiple myeloma (MM). The inhibitory receptors B and T lymphocyte attenuator, CD200 receptor, lymphocyte activation gene-3 (LAG-3) and T cell immunoglobulin and mucin-domain-containing-3 (TIM-3) were present at variable percentages in most CIK cultures, while cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed death-1 (PD-1) and killer cell immunoglobulin-like receptors (KIR2DL1/2/3) were expressed at low level in most cultures. Without blockade, myeloid leukaemia cells were susceptible to autologous and allogeneic CIK-mediated cytotoxicity. Blockade of KIR, LAG-3, PD-1 and TIM-3 but not CTLA-4 resulted in remarkable increase in killing against these targets, even in those with poor baseline cytotoxicity. ALL and MM targets were resistant to CIK-mediated cytotoxicity, and blockade of receptors did not increase cytotoxicity to a meaningful extent. Combination of inhibitors against two receptors did not further increase cytotoxicity. Interestingly, potentiation of CIK killing by blocking antibodies was not predicted by expression of receptors on CIK and their respective ligands on the targets. Compared to un-activated T and NK cells, blockade potentiated the cytotoxicity of CIK cells to a greater degree and at a lower E:T ratio, but without significant increase in cytotoxicity against normal white cell. Our findings provide the basis for clinical trial combining autologous CIK cells with checkpoint inhibitors for patients with AML. PMID:26961084

  14. AcEST: BP919044 [AcEST

    Lifescience Database Archive (English)

    Full Text Available |Q28EK6|Q28EK6_XENTR CHK1 checkpoint homolog (S. pombe) OS=Xenopus tropicalis GN=chek1 PE=2 SV=1 Length = 23...oxidase OS=Pongo abe... 30 5.4 sp|Q06J40|PSAB_BIGNA Photosystem I P700 chlorophyll a apoprotein... 30 7.1 >s...R 169 >sp|Q06J40|PSAB_BIGNA Photosystem I P700 chlorophyll a apoprotein A2 OS=Big...P6U5_BRUMA Putative uncharacterized protein (Fragmen... 89 1e-16 tr|B6A8G9|B6A8G9_HELAM CHK1 checkpoint-like...r|Q28EK6|Q28EK6_XENTR CHK1 checkpoint homolog (S. pombe) OS=Xen... 68 2e-10 tr|B5M6G9|B5M6G9_ORNHU Tumor dif

  15. Genetic Control of the Trigger for the G2/M Checkpoint

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Eric J. [Columbia University; Smilenov, Lubomir B. [Columbia University; Young, Erik F. [Columbia University

    2013-10-01

    The work undertaken in this project addressed two seminal areas of low dose radiation biology that are poorly understood and controversial. These areas are the challenge to the linear-no-threshold (LNT) paradigm at low doses of radiation and, the fundamental elements of radiation bystander effect biology Genetic contributions to low dose checkpoint engagement: The LNT paradigm is an extrapolation of known, measured cancer induction endpoints. Importantly, data for lower doses is often not available. Debatably, radiation protection standards have been introduced which are prudently contingent on the adherence of cancer risk to the established trend seen at higher doses. Intriguing findings from other labs have hinted at separate DNA damage response programs that engage at low or high levels of radiation. Individual radiation sensitivity commensurate with hemizygosity for a radiation sensitivity gene has been estimated at 1-2% in the U.S.. Careful interrogation of the DNA damage response at low doses of radiation became important and served as the basis for this grant. Several genes were tested in combinations to determine if combined haploinsufficiency for multiple radiosensitizing genes could render a cell more sensitive to lower levels of acute radiation exposure. We measured a classical radiation response endpoint, cell cycle arrest prior to mitosis. Mouse embryo fibroblasts were used and provided a uniform, rapidly dividing and genetically manipulable population of study. Our system did not report checkpoint engagement at acute doses of gamma rays below 100 mGy. The system did report checkpoint engagement reproducibly at 500 mGy establishing a threshold for activation between 100 and 500 mGy. Engagement of the checkpoint was ablated in cells nullizygous for ATM but was otherwise unperturbed in cells combinatorially haploinsufficient for ATM and Rad9, ATM and PTEN or PTEN and Rad9. Taken together, these experiments tell us that, in a sensitive fibroblast culture

  16. Design, synthesis and evaluation of molecularly targeted hypoxia-activated prodrugs.

    Science.gov (United States)

    O'Connor, Liam J; Cazares-Körner, Cindy; Saha, Jaideep; Evans, Charles N G; Stratford, Michael R L; Hammond, Ester M; Conway, Stuart J

    2016-04-01

    Regions of insufficient oxygen supply-hypoxia-occur in diverse contexts across biology in both healthy and diseased organisms. The difference in the chemical environment between a hypoxic biological system and one with normal oxygen levels provides an opportunity for targeting compound delivery to hypoxic regions by using bioreductive prodrugs. Here we detail a protocol for the efficient synthesis of (1-methyl-2-nitro-1H-imidazol-5-yl)methanol, which is a key intermediate that can be converted into a range of 1-methyl-2-nitro-1H-imidazole-based precursors of bioreductive prodrugs. We outline methods for attaching the bioreductive group to a range of functionalities, and we discuss the strategy for positioning of the group on the biologically active parent compound. We have used two parent checkpoint kinase 1 (Chk1) inhibitors to exemplify the protocol. The PROCEDURE also describes a suite of reduction assays, of increasing biological relevance, to validate the bioreductive prodrug. These assays are applied to an exemplar compound, CH-01, which is a bioreductive Chk1 inhibitor. This protocol has broad applications to the development of hypoxia-targeted compounds. PMID:27010756

  17. Bacterial Protein-Tyrosine Kinases

    DEFF Research Database (Denmark)

    Shi, Lei; Kobir, Ahasanul; Jers, Carsten;

    2010-01-01

    Bacteria and Eukarya share essentially the same family of protein-serine/threonine kinases, also known as the Hanks-type kinases. However, when it comes to protein-tyrosine phosphorylation, bacteria seem to have gone their own way. Bacterial protein-tyrosine kinases (BY-kinases) are bacterial...... enzymes that are unique in exploiting the ATP/GTP-binding Walker motif to catalyze phosphorylation of protein tyrosine residues. Characterized for the first time only a decade ago, BY-kinases have now come to the fore. Important regulatory roles have been linked with these enzymes, via their involvement...... in exopolysaccharide production, virulence, DNA metabolism, stress response and other key functions of the bacterial cell. BY-kinases act through autophosphorylation (mainly in exopolysaccharide production) and phosphorylation of other proteins, which have in most cases been shown to be activated by...

  18. MOLECULAR DOCKING, SINTESIS dan UJI AKTIVITAS SITOTOKSIK

    Directory of Open Access Journals (Sweden)

    Dian Agung Pangaribowo

    2014-06-01

    Full Text Available ABSTRAK: Senyawa 1-benzoil-1,3-dimetilurea telah dirancang, disintesis, diidentifikasi struktur, dan diuji aktivitas sitotoksik secara in vitro. Simulasi docking dilakukan dengan memposisikan senyawa ke dalam sisi aktif reseptor Checkpoint kinase 1 (Chk1 untuk menentukan model pengikatan ligan reseptor. Sintesis 1-benzoil-1,3-dimetilurea dilakukan lewat reaksi asilasi antara 1,3-dimetilurea dan benzoil klorida. Kemurnian produk hasil sintesis ditentukan dengan metode Kromatografi Lapis Tipis (KLT. Identifikasi struktur dilakukan dengan spektrofotometer UV, FT-IR dan spektrometer NMR. Hasil uji antiproliferatif menunjukkan bahwa senyawa 1-benzoil-1,3-dimetilurea memiliki aktivitas sitotoksik terhadap sel HeLa yang lebih baik dibandingkan dengan kontrol positif. Senyawa 1-benzoil-1,3-dimetilurea dengan aktivitas sitotoksik dapat menjadi agen antikanker yang potensial. Kata kunci: 1-benzoil-1,3-dimetilurea, molecular docking, aktivitas sitotoksik ABSTRACT: A novel 1-benzoyl-1,3-dimethylurea has been designed, synthesized, structurally determined, and the in vitro cytotoxic activity was evaluated. Docking simulation was performed to position this compound into the Checkpoint kinase 1 (Chk1 active site to determine the probable binding model. Synthesis of 1-benzoyl-1,3-dimethylurea was completed by acylation reaction between 1,3-dimethylurea and benzoyl chloride. The purity of synthesized product was determined by Thin Layer Chromatography. Structure identification was performed by UV spectrophotometer, FT-IR and NMR spectrometer. Antiproliferative assay result demonstrated that this compound possessed good cytotoxic activity against HeLa cells, which is comparable to the positive control. This compound with potent cytotoxic activity might be a potential anticancer agent. Keywords: 1-benzoyl-1,3-dimethylurea, molecular docking, cytotoxic activity

  19. Therapeutic targeting of Janus kinases

    OpenAIRE

    Pesu, Marko; Laurence, Arian; Kishore, Nandini; Zwillich, Sam; Chan, Gary; O’Shea, John J.

    2008-01-01

    Cytokines play pivotal roles in immunity and inflammation, and targeting cytokines and their receptors is an effective means of treating such disorders. Type I and II cytokine receptors associate with Janus family kinases (JAKs) to effect intracellular signaling. These structurally unique protein kinases play essential and specific roles in immune cell development and function. One JAK, JAK3, has particularly selective functions. Mutations of this kinase underlie severe combined immunodeficie...

  20. Visualizing autophosphorylation in histidine kinases

    OpenAIRE

    Casino, Patricia; Miguel-Romero, Laura; Marina, Alberto

    2014-01-01

    Reversible protein phosphorylation is the most widespread regulatory mechanism in signal transduction. Autophosphorylation in a dimeric sensor histidine kinase is the first step in two-component signalling, the predominant signal-transduction device in bacteria. Despite being the most abundant sensor kinases in nature, the molecular bases of the histidine kinase autophosphorylation mechanism are still unknown. Furthermore, it has been demonstrated that autophosphorylation can occur in two dir...

  1. Mode of ATM-dependent suppression of chromosome translocation

    Energy Technology Data Exchange (ETDEWEB)

    Yamauchi, Motohiro, E-mail: motoyama@nagasaki-u.ac.jp [Graduate School of Biomedical Sciences, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523 (Japan); Suzuki, Keiji; Oka, Yasuyoshi; Suzuki, Masatoshi; Kondo, Hisayoshi; Yamashita, Shunichi [Graduate School of Biomedical Sciences, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523 (Japan)

    2011-12-09

    Highlights: Black-Right-Pointing-Pointer We addressed how ATM suppresses frequency of chromosome translocation. Black-Right-Pointing-Pointer We found ATM/p53-dependent G1 checkpoint suppresses translocation frequency. Black-Right-Pointing-Pointer We found ATM and DNA-PKcs function in a common pathway to suppress translocation. -- Abstract: It is well documented that deficiency in ataxia telangiectasia mutated (ATM) protein leads to elevated frequency of chromosome translocation, however, it remains poorly understood how ATM suppresses translocation frequency. In the present study, we addressed the mechanism of ATM-dependent suppression of translocation frequency. To know frequency of translocation events in a whole genome at once, we performed centromere/telomere FISH and scored dicentric chromosomes, because dicentric and translocation occur with equal frequency and by identical mechanism. By centromere/telomere FISH analysis, we confirmed that chemical inhibition or RNAi-mediated knockdown of ATM causes 2 to 2.5-fold increase in dicentric frequency at first mitosis after 2 Gy of gamma-irradiation in G0/G1. The FISH analysis revealed that ATM/p53-dependent G1 checkpoint suppresses dicentric frequency, since RNAi-mediated knockdown of p53 elevated dicentric frequency by 1.5-fold. We found ATM also suppresses dicentric occurrence independently of its checkpoint role, as ATM inhibitor showed additional effect on dicentric frequency in the context of p53 depletion and Chk1/2 inactivation. Epistasis analysis using chemical inhibitors revealed that ATM kinase functions in the same pathway that requires kinase activity of DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to suppress dicentric frequency. From the results in the present study, we conclude that ATM minimizes translocation frequency through its commitment to G1 checkpoint and DNA double-strand break repair pathway that requires kinase activity of DNA-PKcs.

  2. Tau-tubulin kinase

    Directory of Open Access Journals (Sweden)

    Seiko Ikezu

    2014-04-01

    Full Text Available Tau-tubulin kinase (TTBK belongs to casein kinase superfamily and can phosphorylate microtubule-associated protein tau and tubulin. TTBK has two isoforms, TTBK1 and TTBK2, which contain highly homologous catalytic domains but their non-catalytic domains are distinctly different. TTBK1 is expressed specifically in the central nervous system and is involved in phosphorylation and aggregation of tau. TTBK2 is ubiquitously expressed in multiple tissues and genetically linked to spinocerebellar ataxia type 11. TTBK1 directly phosphorylates tau protein, especially at Ser422, and also activates cycline-dependent kinase 5 in a unique mechanism. TTBK1 protein expression is significantly elevated in Alzheimer’s disease brains, and genetic variations of the TTBK1 gene are associated with late-onset Alzheimer’s disease in two cohorts of Chinese and Spanish populations. TTBK1 transgenic mice harboring the entire 55-kilobase genomic sequence of human TTBK1 show progression of tau accumulation, neuroinflammation, and neurodegeneration when crossed with tau mutant mice. Our recent study shows that there is a striking switch in mononuclear phagocyte and activation phenotypes in the anterior horn of the spinal cord from alternatively activated (M2-skewed microglia to pro-inflammatory (M1-skewed infiltrating peripheral monocytes in P301L tau mutant mice by crossing with TTBK1 transgenic mice. TTBK1 is responsible for mediating M1-activated microglia-induced neurotoxicity, and its overexpression induces axonal degeneration in vitro. These studies suggest that TTBK1 is an important molecule for the inflammatory axonal degeneration, which may be relevant to the pathobiology of tauopathy including Alzheimer’s disease.

  3. [p53 activation by PI-3K family kinases after DNA double-strand breaks].

    Science.gov (United States)

    Pernin, D; Uhrhammer, N; Verrelle, P; Bignon, Y J; Bay, J O

    2000-09-01

    p53 plays a central role in the cellular response to DNA double-strand breaks (DSBs), and to DNA damage in general. The protein kinases ATM, ATR and DNA-PK detect DSBs and transmit this information to p53 by phosphorylation. This phosphorylation dissociates p53 from its negative regulator, mdm2. p53 then undergoes further modification and activates transcription of the genes responsible for cell cycle arrest. In certain circumstances, p53 also activates transcription of the genes responsible for apoptosis. The dysfunction of this cascade of events is oncogenic, with P53 itself being the most commonly mutated gene in malignant cells, although mutations in both the DNA damage sensors and cell cycle checkpoint and apoptosis effectors are frequent. A more complete understanding of p53 and the proteins it interacts with may allow the development of new cancer treatments. PMID:11038413

  4. Polo-like kinase 1 as target for cancer therapy

    Directory of Open Access Journals (Sweden)

    Weiß Lily

    2012-12-01

    Full Text Available Abstract Polo-like kinase 1 (Plk1 is an interesting molecule both as a biomarker and as a target for highly specific cancer therapy for several reasons. Firstly, it is over-expressed in many cancers and can serve as a biomarker to monitor treatment efficacy of Plk1 inhibitors. Furthermore, the Plk1 enzyme is expressed only in dividing cells and is a major regulator of the cell cycle. It controls entry into mitosis and regulates the spindle checkpoint. The expression of Plk1 in normal cells is not nearly as strong as that in cancer cells, which makes Plk1 a discriminating tartget for the development of cancer-specific small molecule drugs. RNA interference experiments in vitro and in vivo have indicated that downregulation of Plk1 expression represents an attractive concept for cancer therapy. Over the years, a number of Plk1 inhibitors have been discovered. Many of these inhibitors are substances that compete with ATP for the substrate binding site. The ATP-competitive inhibitor BI 6727 is currently being clinically tested in cancer patients. Another drug in development, poloxin, is the first Polo-box domain inhibitor of Plk1. This compound is a derivative of the natural product, thymoquinone, derived from Nigella sativa. A novel and promising strategy is to synthesize bifunctional inhibitors that combine the high binding affinity of ATP inhibitors with the specificity of competitive inhibitors.

  5. The dawn of Aurora kinase research: from fly genetics to the clinic.

    Directory of Open Access Journals (Sweden)

    Mar eCarmena

    2015-11-01

    Full Text Available Aurora kinases comprise a family of highly conserved serine-threonine protein kinases that play a pivotal role in the regulation of cell cycle. Aurora kinases are not only involved in the control of multiple processes during cell division but also coordinate chromosomal and cytoskeletal events, contributing to the regulation of checkpoints and ensuring the smooth progression of the cell cycle.Because of their fundamental contribution to cell cycle regulation, Aurora kinases were originally identified in independent genetic screens designed to find genes involved in the regulation of cell division. The first aurora mutant was part of a collection of mutants isolated in C. Nusslein-Volhard’s laboratory. This collection was screened in D. M. Glover’s laboratory in search for mutations disrupting the centrosome cycle in embryos derived from homozygous mutant mothers. The mutants identified were given names related to the polar regions, and included not only aurora but also the equally famous polo. Ipl1, the only Aurora in yeast, was identified in a genetic screen looking for mutations that caused chromosome segregation defects. The discovery of a second Aurora-like kinase in mammals opened a new chapter in the research of Aurora kinases. The rat kinase AIM was found to be highly homologous to the fly and yeast proteins, but localised at the midzone and midbody and was proposed to have a role in cytokinesis. Homologs of the equatorial Aurora (Aurora B were identified in metazoans ranging from flies to humans. Xenopus Aurora B was found to be in a complex with the chromosomal passenger INCENP, and both proteins were shown to be essential in flies for chromosome structure, segregation, central spindle formation and cytokinesis. Fifteen years on, Aurora kinase research is an active field of research. After the successful introduction of the first anti-mitotic agents in cancer therapy, both Auroras have become the focus of attention as targets for

  6. Phosphatidylinositol 3-kinase in myogenesis.

    Science.gov (United States)

    Kaliman, P; Zorzano, A

    1997-08-01

    Phosphatidylinositol 3-kinase (PI 3-kinase) has been cloned and characterized in a wide range of organisms. PI 3-kinases are activated by a diversity of extracellular stimuli and are involved in multiple cell processes such as cell proliferation, protein trafficking, cell motility, differentiation, regulation of cytoskeletal structure, and apoptosis. It has recently been shown that PI 3-kinase is a crucial second messenger in the signaling of myogenesis. Two structurally unrelated highly specific inhibitors of PI 3-kinase-wortmannin and LY294002-block the morphological and biochemical differentiation program of different skeletal-muscle cell models. Moreover, L6E9 myoblasts overexpressing a dominant-negative mutant of PI 3-kinase p85 regulatory subunit (Δp85) are unable to differentiate. Furthermore, PI 3-kinase is specifically involved in the insulinlike growth factor (IGF)-dependent myogenic pathway. Indeed, the ability of IGF-I, des-1,3-IGF-I, and IGF-II to promote cell fusion and muscle-specific protein expression is impaired after treatment with PI 3-kinase inhibitors or in cells overexpressing Δp85. The identification of additional key downstream elements of the IGF/PI 3-kinase myogenic cascade is crucial to a detailed understanding of the process of muscle differentiation and may generate new tools for skeletal and cardiac muscle regeneration therapies. (Trends Cardiovasc Med 1997;7:198-202). © 1997, Elsevier Science Inc. PMID:21235885

  7. The functions of the cdk-cyclin kinase inhibitor p21WAF1

    International Nuclear Information System (INIS)

    p21WAF1 plays a critical role in regulating cell growth and the cell response to DNA damage. The primary targets of p21WAF1 (hereafter referred to as p21) are the cdk-cyclins which regulate the progression of cukayotic cells through the cell cycle, and proliferating cell nuclear antigen (PCNA), an accessory protein of DNA polymerase δ. p21 forms complexes with a class of cdk-cyclins to inhibit their kinase activity and with PCNA to inhibit synthesis. These distinct properties map to the N- terminal and the C- terminal regions of p21, respectively. Cell cycle arrest in G-1 (G-1 checkpoint) following DNA damage is mediated by p53 and is deficient in p21 null cells. p53 thus up-regulates p21 expression in response to DNA damage, which in turn inhibits cdk2-associated kinase activity. Retinoblastoma protein is regulated by cdk-cyclin kinases, and acts as a downstream target of p21 in DNA damage-induced G-1 arrest. Furthermore, accumulating evidence indicates that p21 may play a role in maintaining G-2 arrest after DNA damage. Transcriptional control of p21 by factors other than p53 is critical for growth arrest and for cell differentiation in many instances. (authors)

  8. The yeast mitogen-activated protein kinase Slt2 is involved in the cellular response to genotoxic stress

    Directory of Open Access Journals (Sweden)

    Soriano-Carot María

    2012-02-01

    Full Text Available Abstract Background The maintenance of genomic integrity is essential for cell viability. Complex signalling pathways (DNA integrity checkpoints mediate the response to genotoxic stresses. Identifying new functions involved in the cellular response to DNA-damage is crucial. The Saccharomyces cerevisiae SLT2 gene encodes a member of the mitogen-activated protein kinase (MAPK cascade whose main function is the maintenance of the cell wall integrity. However, different observations suggest that SLT2 may also have a role related to DNA metabolism. Results This work consisted in a comprehensive study to connect the Slt2 protein to genome integrity maintenance in response to genotoxic stresses. The slt2 mutant strain was hypersensitive to a variety of genotoxic treatments, including incubation with hydroxyurea (HU, methylmetanosulfonate (MMS, phleomycin or UV irradiation. Furthermore, Slt2 was activated by all these treatments, which suggests that Slt2 plays a central role in the cellular response to genotoxic stresses. Activation of Slt2 was not dependent on the DNA integrity checkpoint. For MMS and UV, Slt2 activation required progression through the cell cycle. In contrast, HU also activated Slt2 in nocodazol-arrested cells, which suggests that Slt2 may respond to dNTP pools alterations. However, neither the protein level of the distinct ribonucleotide reductase subunits nor the dNTP pools were affected in a slt2 mutant strain. An analysis of the checkpoint function revealed that Slt2 was not required for either cell cycle arrest or the activation of the Rad53 checkpoint kinase in response to DNA damage. However, slt2 mutant cells showed an elongated bud and partially impaired Swe1 degradation after replicative stress, indicating that Slt2 could contribute, in parallel with Rad53, to bud morphogenesis control after genotoxic stresses. Conclusions Slt2 is activated by several genotoxic treatments and is required to properly cope with DNA damage. Slt

  9. Garcinol, a Histone Acetyltransferase Inhibitor, Radiosensitizes Cancer Cells by Inhibiting Non-Homologous End Joining

    International Nuclear Information System (INIS)

    Purpose: Non-homologous end joining (NHEJ), a major pathway used to repair DNA double-strand breaks (DSBs) generated by ionizing radiation (IR), requires chromatin remodeling at DSB sites through the acetylation of histones by histone acetyltransferases (HATs). However, the effect of compounds with HAT inhibitory activities on the DNA damage response (DDR), including the NHEJ and cell cycle checkpoint, as well as on the radiosensitivity of cancer cells, remains largely unclear. Here, we investigated whether garcinol, a HAT inhibitor found in the rinds of Garcinia indica fruit (called mangosteens), has effects on DDR, and whether it can be used for radiosensitization. Methods and Materials: The following assays were used to examine the effect of garcinol on the inhibition of DSB repair, including the following: a conventional neutral comet assay; a cell-based assay recently developed by us, in which NHEJ repair of DSBs on chromosomal DNA was evaluated; the micrococcal nuclease sensitivity assay; and immunoblotting for autophosphorylation of DNA-dependent protein kinase catalytic subunit (DNA-PKcs). We assessed the effect of garcinol on the cell cycle checkpoint after IR treatment by analyzing the phosphorylation levels of checkpoint kinases CHK1 and CHK2 and histone H3, and by cell cycle profile analysis using flow cytometry. The radiosensitizing effect of garcinol was assessed by a clonogenic survival assay, whereas its effects on apoptosis and senescence were examined by annexin V and senescence-associated β-galactosidase (SA-β-Gal) staining, respectively. Results: We found that garcinol inhibits DSB repair, including NHEJ, without affecting cell cycle checkpoint. Garcinol radiosensitized A549 lung and HeLa cervical carcinoma cells with dose enhancement ratios (at 10% surviving fraction) of 1.6 and 1.5, respectively. Cellular senescence induced by IR was enhanced by garcinol. Conclusion: These results suggest that garcinol is a radiosensitizer that inhibits NHEJ

  10. Garcinol, a Histone Acetyltransferase Inhibitor, Radiosensitizes Cancer Cells by Inhibiting Non-Homologous End Joining

    Energy Technology Data Exchange (ETDEWEB)

    Oike, Takahiro [Division of Multistep Carcinogenesis, National Cancer Center Research Institute, Chuo-ku, Tokyo (Japan); Division of Genome Biology, National Cancer Center Research Institute, Chuo-ku, Tokyo (Japan); Department of Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi, Gunma (Japan); Ogiwara, Hideaki [Division of Genome Biology, National Cancer Center Research Institute, Chuo-ku, Tokyo (Japan); Torikai, Kohta [Gunma University Heavy Ion Medical Center, Maebashi, Gunma (Japan); Nakano, Takashi [Department of Radiation Oncology, Gunma University Graduate School of Medicine, Maebashi, Gunma (Japan); Yokota, Jun [Division of Multistep Carcinogenesis, National Cancer Center Research Institute, Chuo-ku, Tokyo (Japan); Kohno, Takashi, E-mail: tkkohno@ncc.go.jp [Division of Genome Biology, National Cancer Center Research Institute, Chuo-ku, Tokyo (Japan)

    2012-11-01

    Purpose: Non-homologous end joining (NHEJ), a major pathway used to repair DNA double-strand breaks (DSBs) generated by ionizing radiation (IR), requires chromatin remodeling at DSB sites through the acetylation of histones by histone acetyltransferases (HATs). However, the effect of compounds with HAT inhibitory activities on the DNA damage response (DDR), including the NHEJ and cell cycle checkpoint, as well as on the radiosensitivity of cancer cells, remains largely unclear. Here, we investigated whether garcinol, a HAT inhibitor found in the rinds of Garcinia indica fruit (called mangosteens), has effects on DDR, and whether it can be used for radiosensitization. Methods and Materials: The following assays were used to examine the effect of garcinol on the inhibition of DSB repair, including the following: a conventional neutral comet assay; a cell-based assay recently developed by us, in which NHEJ repair of DSBs on chromosomal DNA was evaluated; the micrococcal nuclease sensitivity assay; and immunoblotting for autophosphorylation of DNA-dependent protein kinase catalytic subunit (DNA-PKcs). We assessed the effect of garcinol on the cell cycle checkpoint after IR treatment by analyzing the phosphorylation levels of checkpoint kinases CHK1 and CHK2 and histone H3, and by cell cycle profile analysis using flow cytometry. The radiosensitizing effect of garcinol was assessed by a clonogenic survival assay, whereas its effects on apoptosis and senescence were examined by annexin V and senescence-associated {beta}-galactosidase (SA-{beta}-Gal) staining, respectively. Results: We found that garcinol inhibits DSB repair, including NHEJ, without affecting cell cycle checkpoint. Garcinol radiosensitized A549 lung and HeLa cervical carcinoma cells with dose enhancement ratios (at 10% surviving fraction) of 1.6 and 1.5, respectively. Cellular senescence induced by IR was enhanced by garcinol. Conclusion: These results suggest that garcinol is a radiosensitizer that

  11. The wip1 phosphatase (PPM1D) antagonizes activation of the CHK2 tumor suppressor kinase

    International Nuclear Information System (INIS)

    The DNA checkpoints are signal transduction pathways that sense DNA damage and coordinate various responses such as cell cycle arrests, DNA repair or cell death. These pathways are particularly well conserved in eukaryotes and the family of the 'Checkpoint Kinases 2' genes (or CHK2) plays a major role in them. This family includes the Rad53 protein of the yeast Saccharomyces cerevisiae and its Chk2 human homologue. Rad53 plays a central part in DNA checkpoint: rad53d mutants (whose RAD53 gene has been deleted) are hypersensitive to all genotoxic stresses. Mice Chk2-1- cells are defective in the G1, the intra-S, and the G2/M checkpoints. Mutations in CHK2 have been associated to many forms o f cancer, either sporadic or hereditary which demonstrates Chk2 tumor suppressor function. Chk2 proteins are characterized by several conserved elements: (i) an N-terminal domain with a series of SQ/TQ motifs, preferential phosphorylation sites for the ATM/ATR kinases, (ii) an FHA domain (ForkHead Associated) that binds specifically to phosphorylated residues within TXXY motifs (with the Y residue depending on the FHA domain and conferring an extra specificity) and (iii) a kinase domain including an activation loop. The Chk2 protein is activated by phosphorylation of its threonine T68, mainly by ATM, upon DNA double-strand breaks. This phosphorylation allows for the homo-dimerization of Chk2 through the binding of phospho-T68 from one molecule to the FHA domain of another molecule. It results in trans auto-phosphorylations, especially at threonines T383 and T387 in the activation T-loop. Fully active Chk2 becomes monomeric and, diffusing through the whole nucleus, phosphorylates its targets (CDC25 A and CDC25C/cell cycle arrest; p53, E2F, PML/apoptosis; BRCA2/DNA repair). Chk2/Rad53 inactivation occurs in two cases: once the DNA lesions have been repaired (it is called recovery) or, under certain conditions, in the presence of unrepaired DNA damage (it is then called adaptation

  12. Biological and molecular mechanisms of sulfur mustard analogue-induced toxicity in JB6 and HaCaT cells: possible role of ataxia telangiectasia-mutated/ataxia telangiectasia-Rad3-related cell cycle checkpoint pathway.

    Science.gov (United States)

    Tewari-Singh, Neera; Gu, Mallikarjuna; Agarwal, Chapla; White, Carl W; Agarwal, Rajesh

    2010-06-21

    Effective medical treatment and preventive measures for chemical warfare agent sulfur mustard (HD)-caused incapacitating skin toxicity are lacking, because of limited knowledge of its mechanism of action. The proliferating basal epidermal cells are primary major sites of attack during HD-caused skin injury. Therefore, employing mouse JB6 and human HaCaT epidermal cells, here, we investigated the molecular mechanism of HD analogue 2-chloroethyl ethyl sulfide (CEES)-induced skin cytotoxicity. As compared to the control, up to 1 mM CEES treatment of these cells for 2, 4, and 24 h caused dose-dependent decreases in cell viability and proliferation as measured by DNA synthesis, together with S and G2-M phase arrest in cell cycle progression. Mechanistic studies showed phosphorylation of DNA damage sensors and checkpoint kinases, ataxia telangiectasia-mutated (ATM) at ser1981 and ataxia telangiectasia-Rad3-related (ATR) at ser428 within 30 min of CEES exposure, and modulation of S and G2-M phase-associated cell cycle regulatory proteins, which are downstream targets of ATM and ATR kinases. Hoechst-propidium iodide staining demonstrated that CEES-induced cell death was both necrotic and apoptotic in nature, and the latter was induced at 4 and 24 h of CEES treatment in HaCaT and JB6 cells, respectively. An increase in caspase-3 activity and both caspase-3 and poly(ADP-ribose)polymerase (PARP) cleavage coinciding with CEES-caused apoptosis in both cell lines suggested the involvement of the caspase pathway. Together, our findings suggest a DNA-damaging effect of CEES that activates ATM/ATR cell cycle checkpoint signaling as well as caspase-PARP pathways, leading to cell cycle arrest and apoptosis/necrosis in both JB6 and HaCaT cells. The identified molecular targets, quantitative biomarkers, and epidermal cell models in this study have the potential and usefulness in rapid development of effective prophylactic and therapeutic interventions against HD-induced skin toxicity

  13. In vitro expression levels of cell-cycle checkpoint proteins are associated with cellular DNA repair capacity in peripheral blood lymphocytes: a multivariate analysis

    OpenAIRE

    Fan, You-Hong; Hu, Zhibin; Li, Chunying; Wang, Li-E; Guo, Zhaozheng; Qiao, Yawei; Zhang, Li; Zhang, Wei; Mao, Li; Wei, Qingyi

    2007-01-01

    DNA repair should occur after cells sense DNA damage signals and undergo cell-cycle arrest to provide sufficient time for DNA repair, and suboptimal DNA repair capacity (DRC) in peripheral lymphocytes has been suggested as a cancer susceptibility marker. Numerous studies showed a functional link between DNA damage sensing, cell-cycle checkpoint and DNA repair. We hypothesized that in vitro cell-cycle checkpoint-related protein expression levels in stimulated lymphocytes predict DRC levels. To...

  14. Direct and indirect control of the initiation of meiotic recombination by DNA damage checkpoint mechanisms in budding yeast.

    Directory of Open Access Journals (Sweden)

    Bilge Argunhan

    Full Text Available Meiotic recombination plays an essential role in the proper segregation of chromosomes at meiosis I in many sexually reproducing organisms. Meiotic recombination is initiated by the scheduled formation of genome-wide DNA double-strand breaks (DSBs. The timing of DSB formation is strictly controlled because unscheduled DSB formation is detrimental to genome integrity. Here, we investigated the role of DNA damage checkpoint mechanisms in the control of meiotic DSB formation using budding yeast. By using recombination defective mutants in which meiotic DSBs are not repaired, the effect of DNA damage checkpoint mutations on DSB formation was evaluated. The Tel1 (ATM pathway mainly responds to unresected DSB ends, thus the sae2 mutant background in which DSB ends remain intact was employed. On the other hand, the Mec1 (ATR pathway is primarily used when DSB ends are resected, thus the rad51 dmc1 double mutant background was employed in which highly resected DSBs accumulate. In order to separate the effect caused by unscheduled cell cycle progression, which is often associated with DNA damage checkpoint defects, we also employed the ndt80 mutation which permanently arrests the meiotic cell cycle at prophase I. In the absence of Tel1, DSB formation was reduced in larger chromosomes (IV, VII, II and XI whereas no significant reduction was found in smaller chromosomes (III and VI. On the other hand, the absence of Rad17 (a critical component of the ATR pathway lead to an increase in DSB formation (chromosomes VII and II were tested. We propose that, within prophase I, the Tel1 pathway facilitates DSB formation, especially in bigger chromosomes, while the Mec1 pathway negatively regulates DSB formation. We also identified prophase I exit, which is under the control of the DNA damage checkpoint machinery, to be a critical event associated with down-regulating meiotic DSB formation.

  15. Spindle checkpoint activation at meiosis I advances anaphase II onset via meiosis-specific APC/C regulation

    OpenAIRE

    Yamamoto, Ayumu; Kitamura, Kenji; Hihara, Daisuke; Hirose, Yukinobu; Katsuyama, Satoshi; Hiraoka, Yasushi

    2008-01-01

    During mitosis, the spindle assembly checkpoint (SAC) inhibits the Cdc20-activated anaphase-promoting complex/cyclosome (APC/CCdc20), which promotes protein degradation, and delays anaphase onset to ensure accurate chromosome segregation. However, the SAC function in meiotic anaphase regulation is poorly understood. Here, we examined the SAC function in fission yeast meiosis. As in mitosis, a SAC factor, Mad2, delayed anaphase onset via Slp1 (fission yeast Cdc20) when chromosomes attach to th...

  16. Current status and perspectives in translational biomarker research for PD-1/PD-L1 immune checkpoint blockade therapy.

    Science.gov (United States)

    Ma, Weijie; Gilligan, Barbara M; Yuan, Jianda; Li, Tianhong

    2016-01-01

    Modulating immune inhibitory pathways has been a major recent breakthrough in cancer treatment. Checkpoint blockade antibodies targeting cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programed cell-death protein 1 (PD-1) have demonstrated acceptable toxicity, promising clinical responses, durable disease control, and improved survival in some patients with advanced melanoma, non-small cell lung cancer (NSCLC), and other tumor types. About 20 % of advanced NSCLC patients and 30 % of advanced melanoma patients experience tumor responses from checkpoint blockade monotherapy, with better clinical responses seen with the combination of anti-PD-1 and anti-CTLA-4 antibodies. Given the power of these new therapies, it is important to understand the complex and dynamic nature of host immune responses and the regulation of additional molecules in the tumor microenvironment and normal organs in response to the checkpoint blockade therapies. In this era of precision oncology, there remains a largely unmet need to identify the patients who are most likely to benefit from immunotherapy, to optimize the monitoring assays for tumor-specific immune responses, to develop strategies to improve clinical efficacy, and to identify biomarkers so that immune-related adverse events can be avoided. At this time, PD-L1 immunohistochemistry (IHC) staining using 22C3 antibody is the only FDA-approved companion diagnostic for patients with NSCLC-treated pembrolizumab, but more are expected to come to market. We here summarize the current knowledge, clinical efficacy, potential immune biomarkers, and associated assays for immune checkpoint blockade therapies in advanced solid tumors. PMID:27234522

  17. The tumor suppressor homolog in fission yeast, myh1+, displays a strong interaction with the checkpoint gene rad1+

    International Nuclear Information System (INIS)

    The DNA glycosylase MutY is strongly conserved in evolution, and homologs are found in most eukaryotes and prokaryotes examined. This protein is implicated in repair of oxidative DNA damage, in particular adenine mispaired opposite 7,8-dihydro-8-oxoguanine. Previous investigations in Escherichia coli, fission yeast, and mammalian cells show an association of mutations in MutY homologs with a mutator phenotype and carcinogenesis. Eukaryotic MutY homologs physically associate with several proteins with a role in replication, DNA repair, and checkpoint signaling, specifically the trimeric 9-1-1 complex. In a genetic investigation of the fission yeast MutY homolog, myh1+, we show that the myh1 mutation confers a moderately increased UV sensitivity alone and in combination with mutations in several DNA repair genes. The myh1 rad1, and to a lesser degree myh1 rad9, double mutants display a synthetic interaction resulting in enhanced sensitivity to DNA damaging agents and hydroxyurea. UV irradiation of myh1 rad1 double mutants results in severe chromosome segregation defects and visible DNA fragmentation, and a failure to activate the checkpoint. Additionally, myh1 rad1 double mutants exhibit morphological defects in the absence of DNA damaging agents. We also found a moderate suppression of the slow growth and UV sensitivity of rhp51 mutants by the myh1 mutation. Our results implicate fission yeast Myh1 in repair of a wider range of DNA damage than previously thought, and functionally link it to the checkpoint pathway

  18. Variations in genes involved in immune response checkpoints and association with outcomes in patients with resected colorectal liver metastases.

    Science.gov (United States)

    Stremitzer, S; Sunakawa, Y; Zhang, W; Yang, D; Ning, Y; Stintzing, S; Sebio, A; Yamauchi, S; Matsusaka, S; El-Khoueiry, R; Stift, J; Wrba, F; Gruenberger, T; Lenz, H-J

    2015-12-01

    In patients with colorectal liver metastases (CLM), liver resection offers the possibility of cure and long-term survival. The liver is a highly immunogenic organ harboring ~80% of the body's tissue macrophages. Emerging data demonstrate a critical role of the immune response for cancer treatment. We investigated variations within genes involved in immune response checkpoints and their association with outcomes in patients with CLM who underwent neoadjuvant chemotherapy including bevacizumab and liver resection. Single-nucleotide polymorphisms (SNPs) in nine genes (CCL2, CCR2, LAG3, NT5E, PDCD1, CD274, IDO1, CTLA4 and CD24) were analyzed in genomic DNA from 149 patients with resected bevacizumab-pretreated CLM by direct Sanger DNA sequencing, and correlated with response, recurrence-free survival (RFS), overall survival (OS), probability of cure and recurrence patterns. IDO1 (indoleamine 2, 3-dioxygenase) rs3739319 G>A and CD24 rs8734 G>A showed a significant difference in 3-year OS rates. In addition, IDO1 rs3739319 G>A was significantly associated with extrahepatic recurrence. Recursive partitioning analyses revealed that IDO1 rs3739319 G>A was the dominant SNP predicting RFS and OS. Our data suggest that variants within genes involved in immune response checkpoints are associated with outcomes in patients with resected CLM and might lead to improved treatment strategies modulating anti-tumor immune response by targeting novel immune checkpoints. PMID:25752522

  19. Immune checkpoint blockade in cancer treatment: a double-edged sword cross-targeting the host as an "innocent bystander".

    Science.gov (United States)

    Gelao, Lucia; Criscitiello, Carmen; Esposito, Angela; Goldhirsch, Aron; Curigliano, Giuseppe

    2014-03-01

    Targeted immune checkpoint blockade augments anti-tumor immunity and induces durable responses in patients with melanoma and other solid tumors. It also induces specific "immune-related adverse events" (irAEs). IrAEs mainly include gastrointestinal, dermatological, hepatic and endocrinological toxicities. Off-target effects that arise appear to account for much of the toxicity of the immune checkpoint blockade. These unique "innocent bystander" effects are likely a direct result of breaking immune tolerance upon immune check point blockade and require specific treatment guidelines that include symptomatic therapies or systemic corticosteroids. What do we need going forward to limit immune checkpoint blockade-induced toxicity? Most importantly, we need a better understanding of the roles played by these agents in normal tissues, so that we can begin to predict potentially problematic side effects on the basis of their selectivity profile. Second, we need to focus on the predictive factors of the response and toxicity of the host rather than serially focusing on individual agents. Third, rigorous biomarker-driven clinical trials are needed to further elucidate the mechanisms of both the benefit and toxicity. We will summarize the double-edged sword effect of immunotherapeutics in cancer treatment. PMID:24594636

  20. Silencing of poly(ADP-ribose) glycohydrolase sensitizes lung cancer cells to radiation through the abrogation of DNA damage checkpoint

    Energy Technology Data Exchange (ETDEWEB)

    Nakadate, Yusuke [Shien-Lab, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045 (Japan); Department of Bioengineering, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Kodera, Yasuo; Kitamura, Yuka [Shien-Lab, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045 (Japan); Tachibana, Taro [Department of Bioengineering, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Tamura, Tomohide [Division of Thoracic Oncology, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045 (Japan); Koizumi, Fumiaki, E-mail: fkoizumi@ncc.go.jp [Division of Thoracic Oncology, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045 (Japan)

    2013-11-29

    Highlights: •Radiosensitization by PARG silencing was observed in multiple lung cancer cells. •PAR accumulation was enhanced by PARG silencing after DNA damage. •Radiation-induced G2/M arrest and checkpoint activation were impaired by PARG siRNA. -- Abstract: Poly(ADP-ribose) glycohydrolase (PARG) is a major enzyme that plays a role in the degradation of poly(ADP-ribose) (PAR). PARG deficiency reportedly sensitizes cells to the effects of radiation. In lung cancer, however, it has not been fully elucidated. Here, we investigated whether PARG siRNA contributes to an increased radiosensitivity using 8 lung cancer cell lines. Among them, the silencing of PARG induced a radiosensitizing effect in 5 cell lines. Radiation-induced G2/M arrest was largely suppressed by PARG siRNA in PC-14 and A427 cells, which exhibited significantly enhanced radiosensitivity in response to PARG knockdown. On the other hand, a similar effect was not observed in H520 cells, which did not exhibit a radiosensitizing effect. Consistent with a cell cycle analysis, radiation-induced checkpoint signals were not well activated in the PC-14 and A427 cells when treated with PARG siRNA. These results suggest that the increased sensitivity to radiation induced by PARG knockdown occurs through the abrogation of radiation-induced G2/M arrest and checkpoint activation in lung cancer cells. Our findings indicate that PARG could be a potential target for lung cancer treatments when used in combination with radiotherapy.

  1. Cryo-EM of Mitotic Checkpoint Complex-Bound APC/C Reveals Reciprocal and Conformational Regulation of Ubiquitin Ligation.

    Science.gov (United States)

    Yamaguchi, Masaya; VanderLinden, Ryan; Weissmann, Florian; Qiao, Renping; Dube, Prakash; Brown, Nicholas G; Haselbach, David; Zhang, Wei; Sidhu, Sachdev S; Peters, Jan-Michael; Stark, Holger; Schulman, Brenda A

    2016-08-18

    The mitotic checkpoint complex (MCC) coordinates proper chromosome biorientation on the spindle with ubiquitination activities of CDC20-activated anaphase-promoting complex/cyclosome (APC/C(CDC20)). APC/C(CDC20) and two E2s, UBE2C and UBE2S, catalyze ubiquitination through distinct architectures for linking ubiquitin (UB) to substrates and elongating polyUB chains, respectively. MCC, which contains a second molecule of CDC20, blocks APC/C(CDC20)-UBE2C-dependent ubiquitination of Securin and Cyclins, while differentially determining or inhibiting CDC20 ubiquitination to regulate spindle surveillance, checkpoint activation, and checkpoint termination. Here electron microscopy reveals conformational variation of APC/C(CDC20)-MCC underlying this multifaceted regulation. MCC binds APC/C-bound CDC20 to inhibit substrate access. However, rotation about the CDC20-MCC assembly and conformational variability of APC/C modulate UBE2C-catalyzed ubiquitination of MCC's CDC20 molecule. Access of UBE2C is limiting for subsequent polyubiquitination by UBE2S. We propose that conformational dynamics of APC/C(CDC20)-MCC modulate E2 activation and determine distinctive ubiquitination activities as part of a response mechanism ensuring accurate sister chromatid segregation. PMID:27522463

  2. MET Receptor Tyrosine Kinase

    Science.gov (United States)

    Faoro, Leonardo; Cervantes, Gustavo M.; El-Hashani, Essam; Salgia, Ravi

    2010-01-01

    MET receptor tyrosine kinase (RTK) and its ligand hepatocyte growth factor (HGF) have become important therapeutic target in oncology, especially lung cancer. MET RTK is involved in cancer cell growth/survival, motility/migration, invasion/metastasis, and in angiogenesis. MET can be overexpressed in lung cancer, sometimes mutated, and sometimes amplified. Not only can MET be overexpressed, there are subsets of lung cancer tumors that have HGF overexpression. The mutations of MET can occur in the semaphorin and/or juxtamembrane domain in a majority of times. Amplification of MET can occur de novo in primary/metastatic tumors, as well arise in the context of therapeutic inhibition. There are a number of clinical inhibitors that have been developed against MET/HGF. Small molecule inhibitors such as XL184 and PF02341066 have come to clinical fruition, as well as antibodies against MET (such as MetMAb). These inhibitors will be discussed. PMID:19861919

  3. Fin1-PP1 Helps Clear Spindle Assembly Checkpoint Protein Bub1 from Kinetochores in Anaphase.

    Science.gov (United States)

    Bokros, Michael; Gravenmier, Curtis; Jin, Fengzhi; Richmond, Daniel; Wang, Yanchang

    2016-02-01

    The spindle assembly checkpoint (SAC) monitors chromosome attachment defects, and the assembly of SAC proteins at kinetochores is essential for its activation, but the SAC disassembly process remains unknown. We found that deletion of a 14-3-3 protein, Bmh1, or hyperactivation of Cdc14 early anaphase release (FEAR) allows premature SAC silencing in budding yeast, which depends on a kinetochore protein Fin1 that forms a complex with protein phosphatase PP1. Previous works suggest that FEAR-dependent Fin1 dephosphorylation promotes Bmh1-Fin1 dissociation, which enables kinetochore recruitment of Fin1-PP1. We found persistent kinetochore association of SAC protein Bub1 in fin1Δ mutants after anaphase entry. Therefore, we revealed a mechanism that clears SAC proteins from kinetochores. After anaphase entry, FEAR activation promotes kinetochore enrichment of Fin1-PP1, resulting in SAC disassembly at kinetochores. This mechanism is required for efficient SAC silencing after SAC is challenged, and untimely Fin1-kinetochore association causes premature SAC silencing and chromosome missegregation. PMID:26832405

  4. Stable kinetochore–microtubule attachment is sufficient to silence the spindle assembly checkpoint in human cells

    Science.gov (United States)

    Tauchman, Eric C.; Boehm, Frederick J.; DeLuca, Jennifer G.

    2015-01-01

    During mitosis, duplicated sister chromatids attach to microtubules emanating from opposing sides of the bipolar spindle through large protein complexes called kinetochores. In the absence of stable kinetochore–microtubule attachments, a cell surveillance mechanism known as the spindle assembly checkpoint (SAC) produces an inhibitory signal that prevents anaphase onset. Precisely how the inhibitory SAC signal is extinguished in response to microtubule attachment remains unresolved. To address this, we induced formation of hyper-stable kinetochore–microtubule attachments in human cells using a non-phosphorylatable version of the protein Hec1, a core component of the attachment machinery. We find that stable attachments are sufficient to silence the SAC in the absence of sister kinetochore bi-orientation and strikingly in the absence of detectable microtubule pulling forces or tension. Furthermore, we find that SAC satisfaction occurs despite the absence of large changes in intra-kinetochore distance, suggesting that substantial kinetochore stretching is not required for quenching the SAC signal. PMID:26620470

  5. Checkpoint-Inhibitoren in der Immuntherapie: Ein Meilenstein in der Behandlung des malignen Melanoms.

    Science.gov (United States)

    Wilden, Sophia M; Lang, Berenice M; Mohr, Peter; Grabbe, Stephan

    2016-07-01

    Seit Jahrzehnten ist bekannt, dass Tumoren vom Immunsystem erkannt und zerstört werden können. Diese, vor allem in Tierversuchen gewonnene Erkenntnis konnte jedoch in der Vergangenheit nicht zum Nutzen unserer Patienten umgesetzt werden, da immunonkologische Therapieansätze in den letzten Jahrzehnten in der Anwendung beim Menschen stets versagt haben. Daher hat, mit Ausnahme der adjuvanten Interferontherapie, keines dieser Verfahren den Einzug in die klinische Versorgung gefunden. Langzeitüberleben unter guter Lebensqualität war dabei sehr wenigen Patienten vorbehalten. Mit den neuen immunologischen Therapieansätzen wird jedoch sowohl das Langzeitüberleben als auch die Lebensqualität onkologischer Patienten neu definiert. Auf die neuen "Immun-Checkpoint-Inhibitoren" spricht erstmals ein relevanter Teil der behandelten Patienten an und diese zeigen in der Regel langandauernde Remissionen bis hin zur Heilung. Schon jetzt ist klar, dass die Immuntherapie in Zukunft eine der wesentlichen Therapiesäulen bei der Behandlung des metastasierten Melanoms und auch vieler anderer fortgeschrittener Tumoren bilden wird. In dieser Übersicht werden die wichtigsten neuen Therapiemodalitäten besprochen und sowohl deren Wirkprinzip als auch klinische Daten zum Therapieansprechen und zu erwartenden Nebenwirkungen der Therapie referiert. PMID:27373243

  6. Recognition of a Single Transmembrane Degron by Sequential Quality Control Checkpoints

    Science.gov (United States)

    Fayadat, Laurence; Kopito, Ron R.

    2003-01-01

    To understand the relationship between conformational maturation and quality control–mediated proteolysis in the secretory pathway, we engineered the well-characterized degron from the α-subunit of the T-cell antigen receptor (TCRα) into the α-helical transmembrane domain of homotrimeric type I integral membrane protein, influenza hemagglutinin (HA). Although the membrane degron does not appear to interfere with acquisition of native secondary structure, as assessed by the formation of native intrachain disulfide bonds, only ∼50% of nascent mutant HA chains (HA++) become membrane-integrated and acquire complex N-linked glycans indicative of transit to a post-ER compartment. The remaining ∼50% of nascent HA++ chains fail to integrate into the lipid bilayer and are subject to proteasome-dependent degradation. Site-specific cleavage by extracellular trypsin and reactivity with conformation-specific monoclonal antibodies indicate that membrane-integrated HA++ molecules are able to mature to the plasma membrane with a conformation indistinguishable from that of HAwt. These apparently native HA++ molecules are, nevertheless, rapidly degraded by a process that is insensitive to proteasome inhibitors but blocked by lysosomotropic amines. These data suggest the existence in the secretory pathway of at least two sequential quality control checkpoints that recognize the same transmembrane degron, thereby ensuring the fidelity of protein deployment to the plasma membrane. PMID:12631739

  7. Dictyostelium nucleomorphin is a member of the BRCT-domain family of cell cycle checkpoint proteins.

    Science.gov (United States)

    Myre, Michael A; O'Day, Danton H

    2004-11-18

    A search of the Dictyostelium genome project database (http://dictybase.org/db/cgi-bin/blast.pl) with nucleomorphin, a protein that regulates the nuclear number, predicted it to be encoded by a larger gene containing a putative breast cancer carboxy-terminus domain (BRCT). Using RT-PCR, Northern and Western blotting we have identified a differentially expressed, 2318 bp cDNA encoding a protein isoform of Dictyostelium NumA with an apparent molecular weight of 70 kDa that we have called NumB. It contains a single amino-terminal BRCT-domain spanning residues 125-201. Starvation of shaking cultures reduces NumA expression by approximately 88+/-5.6%, whereas NumB expression increases approximately 35+/-3.5% from vegetative levels. NumC, a third isoform that is also expressed during development but not growth, remains to be characterized. These findings suggest NumB may be a member of the BRCT-domain containing cell cycle checkpoint proteins. PMID:15535983

  8. Oncogene-induced senescence is part of the tumorigenesis barrier imposed by DNA damage checkpoints

    DEFF Research Database (Denmark)

    Bartkova, Jirina; Rezaei, Nousin; Liontos, Michalis;

    2006-01-01

    DNA double-strand breaks. Inhibiting the DNA double-strand break response kinase ataxia telangiectasia mutated (ATM) suppressed the induction of senescence and in a mouse model led to increased tumour size and invasiveness. Analysis of human precancerous lesions further indicated that DNA damage and...

  9. MAP Kinases in Immune Responses

    Institute of Scientific and Technical Information of China (English)

    Yongliang Zhang; Chen Dong

    2005-01-01

    MAP kinases are evolutionarily conserved signaling regulators from budding yeast to mammals and play essential roles in both innate and adaptive immune responses. There are three main families of MAPKs in mammals. Each of them has its own activators, inactivators, substrates and scaffolds, which altogether form a fine signaling network in response to different extracellular or intracellular stimulation. In this review, we summarize recent advances in understanding of the regulation of MAP kinases and the roles of MAP kinases in innate and adaptive immune responses.

  10. Yeast Dun1 Kinase Regulates Ribonucleotide Reductase Small Subunit Localization in Response to Iron Deficiency.

    Science.gov (United States)

    Sanvisens, Nerea; Romero, Antonia M; Zhang, Caiguo; Wu, Xiaorong; An, Xiuxiang; Huang, Mingxia; Puig, Sergi

    2016-04-29

    Ribonucleotide reductase (RNR) is an essential iron-dependent enzyme that catalyzes deoxyribonucleotide synthesis in eukaryotes. Living organisms have developed multiple strategies to tightly modulate RNR function to avoid inadequate or unbalanced deoxyribonucleotide pools that cause DNA damage and genome instability. Yeast cells activate RNR in response to genotoxic stress and iron deficiency by facilitating redistribution of its small heterodimeric subunit Rnr2-Rnr4 from the nucleus to the cytoplasm, where it forms an active holoenzyme with large Rnr1 subunit. Dif1 protein inhibits RNR by promoting nuclear import of Rnr2-Rnr4. Upon DNA damage, Dif1 phosphorylation by the Dun1 checkpoint kinase and its subsequent degradation enhances RNR function. In this report, we demonstrate that Dun1 kinase triggers Rnr2-Rnr4 redistribution to the cytoplasm in response to iron deficiency. We show that Rnr2-Rnr4 relocalization by low iron requires Dun1 kinase activity and phosphorylation site Thr-380 in the Dun1 activation loop, but not the Dun1 forkhead-associated domain. By using different Dif1 mutant proteins, we uncover that Dun1 phosphorylates Dif1 Ser-104 and Thr-105 residues upon iron scarcity. We observe that the Dif1 phosphorylation pattern differs depending on the stimuli, which suggests different Dun1 activating pathways. Importantly, the Dif1-S104A/T105A mutant exhibits defects in nucleus-to-cytoplasm redistribution of Rnr2-Rnr4 by iron limitation. Taken together, these results reveal that, in response to iron starvation, Dun1 kinase phosphorylates Dif1 to stimulate Rnr2-Rnr4 relocalization to the cytoplasm and promote RNR function. PMID:26970775

  11. Isolation of chloroplastic phosphoglycerate kinase

    Energy Technology Data Exchange (ETDEWEB)

    Macioszek, J.; Anderson, L.E. (Univ. of Illinois, Chicago (USA)); Anderson, J.B. (Pennsylvania State Univ., University Park (USA))

    1990-09-01

    We report here a method for the isolation of high specific activity phosphoglycerate kinase (EC 2.7.2.3) from chloroplasts. The enzyme has been purified over 200-fold from pea (Pisum sativum L.) stromal extracts to apparent homogeneity with 23% recovery. Negative cooperativity is observed with the two enzyme phosphoglycerate kinase/glyceraldehyde-3-P dehydrogenase (EC 1.2.1.13) couple restored from the purified enzymes when NADPH is the reducing pyridine nucleotide, consistent with earlier results obtained with crude chloroplastic extracts. Michaelis Menten kinetics are observed when 3-phosphoglycerate is held constant and phosphoglycerate kinase is varied, which suggests that phosphoglycerate kinase-bound 1,3-bisphosphoglycerate may be the preferred substrate for glyceraldehyde-3-P dehydrogenase in the chloroplast.

  12. Protein Crystals of Raf Kinase

    Science.gov (United States)

    1995-01-01

    This image shows crystals of the protein raf kinase grown on Earth (photo a) and on USML-2 (photo b). The space-grown crystals are an order of magnitude larger. Principal Investigator: Dan Carter of New Century Pharmaceuticals

  13. Immune checkpoint blockade with concurrent electrochemotherapy in advanced melanoma: a retrospective multicenter analysis.

    Science.gov (United States)

    Heppt, Markus V; Eigentler, Thomas K; Kähler, Katharina C; Herbst, Rudolf A; Göppner, Daniela; Gambichler, Thilo; Ulrich, Jens; Dippel, Edgar; Loquai, Carmen; Schell, Beatrice; Schilling, Bastian; Schäd, Susanne G; Schultz, Erwin S; Matheis, Fanny; Tietze, Julia K; Berking, Carola

    2016-08-01

    Growing evidence suggests that concurrent loco-regional and systemic treatment modalities may lead to synergistic anti-tumor effects in advanced melanoma. In this retrospective multicenter study, we evaluate the use of electrochemotherapy (ECT) combined with ipilimumab or PD-1 inhibition. We investigated patients with unresectable or metastatic melanoma who received the combination of ECT and immune checkpoint blockade for distant or cutaneous metastases within 4 weeks. Clinical and laboratory data were collected and analyzed with respect to safety and efficacy. A total of 33 patients from 13 centers were identified with a median follow-up time of 9 months. Twenty-eight patients received ipilimumab, while five patients were treated with a PD-1 inhibitor (pembrolizumab n = 3, nivolumab n = 2). The local overall response rate (ORR) was 66.7 %. The systemic ORR was 19.2 and 40.0 % in the ipilimumab and PD-1 cohort, respectively. The median duration of response was not reached in either group. The median time to disease progression was 2.5 months for the entire population with 2 months for ipilimumab and 5 months for PD-1 blockade. The median overall survival was not reached in patients with ipilimumab and 15 months in the PD-1 group. Severe systemic adverse events were detected in 25.0 % in the ipilimumab group. No treatment-related deaths were observed. This is the first reported evaluation of ECT and simultaneous PD-1 inhibition and the largest published dataset on ECT with concurrent ipilimumab. The local response was lower than reported for ECT only. Ipilimumab combined with ECT was feasible, tolerable and showed a high systemic response rate. PMID:27294607

  14. Structure of the sporulation histidine kinase inhibitor Sda from Bacillus subtilis and insights into its solution state

    Energy Technology Data Exchange (ETDEWEB)

    Jacques, David A.; Streamer, Margaret [School of Molecular and Microbial Biosciences, University of Sydney (Australia); Rowland, Susan L.; King, Glenn F. [Institute of Molecular Biology, University of Queensland (Australia); Guss, J. Mitchell; Trewhella, Jill; Langley, David B., E-mail: d.langley@usyd.edu.au [School of Molecular and Microbial Biosciences, University of Sydney (Australia)

    2009-06-01

    The crystal structure of Sda, a DNA-replication/damage checkpoint inhibitor of sporulation in B. subtilis, has been solved via the MAD method. The subunit arrangement in the crystal has enabled a reappraisal of previous biophysical data, resulting in a new model for the behaviour of the protein in solution. The crystal structure of the DNA-damage checkpoint inhibitor of sporulation, Sda, from Bacillus subtilis, has been solved by the MAD technique using selenomethionine-substituted protein. The structure closely resembles that previously solved by NMR, as well as the structure of a homologue from Geobacillus stearothermophilus solved in complex with the histidine kinase KinB. The structure contains three molecules in the asymmetric unit. The unusual trimeric arrangement, which lacks simple internal symmetry, appears to be preserved in solution based on an essentially ideal fit to previously acquired scattering data for Sda in solution. This interpretation contradicts previous findings that Sda was monomeric or dimeric in solution. This study demonstrates the difficulties that can be associated with the characterization of small proteins and the value of combining multiple biophysical techniques. It also emphasizes the importance of understanding the physical principles behind these techniques and therefore their limitations.

  15. Structure of the sporulation histidine kinase inhibitor Sda from Bacillus subtilis and insights into its solution state

    International Nuclear Information System (INIS)

    The crystal structure of Sda, a DNA-replication/damage checkpoint inhibitor of sporulation in B. subtilis, has been solved via the MAD method. The subunit arrangement in the crystal has enabled a reappraisal of previous biophysical data, resulting in a new model for the behaviour of the protein in solution. The crystal structure of the DNA-damage checkpoint inhibitor of sporulation, Sda, from Bacillus subtilis, has been solved by the MAD technique using selenomethionine-substituted protein. The structure closely resembles that previously solved by NMR, as well as the structure of a homologue from Geobacillus stearothermophilus solved in complex with the histidine kinase KinB. The structure contains three molecules in the asymmetric unit. The unusual trimeric arrangement, which lacks simple internal symmetry, appears to be preserved in solution based on an essentially ideal fit to previously acquired scattering data for Sda in solution. This interpretation contradicts previous findings that Sda was monomeric or dimeric in solution. This study demonstrates the difficulties that can be associated with the characterization of small proteins and the value of combining multiple biophysical techniques. It also emphasizes the importance of understanding the physical principles behind these techniques and therefore their limitations

  16. Methylations of histone H3 lysine 9 and lysine 36 are functionally linked to DNA replication checkpoint control in fission yeast

    International Nuclear Information System (INIS)

    Recently, histone H4 lysine 20 and H3 lysine 79 methylations were functionally linked to DNA damage checkpoint. The crosstalk between histone methylation and the S-M checkpoint, however, has remained unclear. Here, we show that H3 lysine 9 (K9) and lysine 36 (K36) methylations catalyzed by two histone methyltransferases Clr4 and Set2 are involved in hydroxyurea (HU)-induced replication checkpoint. The clr4-set2 double mutants besides histone H3-K9 and K36 double mutants exhibited HU-sensitivity, a defective HU-induced S-M checkpoint, and a significant reduction of HU-induced phosphorylation of Cdc2. Intriguingly, the clr4-set2 double mutations impaired the HU-induced accumulation of a mitotic inhibitor Mik1. Double mutants in Alp13 and Swi6, which can specifically bind to H3-K36 and K9 methylations, exhibited phenotypes similar to those of the clr4-set2 mutants. Together, these findings suggest that methylations of histone H3-K9 and K36 by Clr4 and Set2 are functionally linked to DNA replication checkpoint via accumulation of Mik1

  17. AcEST: DK947793 [AcEST

    Lifescience Database Archive (English)

    Full Text Available 8EK6|Q28EK6_XENTR CHK1 checkpoint homolog (S. pombe) OS=Xenopus tropicalis GN=chek1 PE=2 SV=1 Length = 231 S...06J40|PSAB_BIGNA Photosystem I P700 chlorophyll a apoprotein... 31 5.5 sp|Q5XHY8|CF146_RAT Uncharacterized p...KGFLVMGSKFRYSGRTQAQTRQASALIDRP 413 >sp|Q06J40|PSAB_BIGNA Photosystem I P700 chlorophyll a apop...6 tr|A8JJG4|A8JJG4_CHLRE Predicted protein OS=Chlamydomonas reinha... 81 5e-14 tr|B6A8G9|B6A8G9_HELAM CHK1 checkpo...rugi... 69 4e-13 tr|Q28EK6|Q28EK6_XENTR CHK1 checkpoint homolog (S. pombe) OS=Xen... 68 4e-10 tr|B5M6G9|B5M6

  18. AcEST: DK945737 [AcEST

    Lifescience Database Archive (English)

    Full Text Available jct: 15 GSIPEREPEKRLPHPRKAAGAQITHSRHGEVVT 47 >tr|Q28EK6|Q28EK6_XENTR CHK1 checkpoint homolog (S. pombe) OS=Xenopus trop...hyll a apoprotein... 31 2.2 sp|Q7TQM5|KPRP_RAT Keratinocyte pr...hyll a apoprotein A2 OS=Bigelowiella natans GN=psaB PE=3 SV=1 Length = 735 Score = 30...NHW8_BRUMA Putative uncharacterized protein (Fragmen... 59 4e-12 tr|B6A8G9|B6A8G9_HELAM CHK1 checkpo...int-like protein (Fragment) O... 69 1e-10 tr|Q28EK6|Q28EK6_XENTR CHK1 checkpoint homolog (S. po

  19. ZTF-8 interacts with the 9-1-1 complex and is required for DNA damage response and double-strand break repair in the C. elegans germline.

    Directory of Open Access Journals (Sweden)

    Hyun-Min Kim

    2014-10-01

    Full Text Available Germline mutations in DNA repair genes are linked to tumor progression. Furthermore, failure in either activating a DNA damage checkpoint or repairing programmed meiotic double-strand breaks (DSBs can impair chromosome segregation. Therefore, understanding the molecular basis for DNA damage response (DDR and DSB repair (DSBR within the germline is highly important. Here we define ZTF-8, a previously uncharacterized protein conserved from worms to humans, as a novel factor involved in the repair of both mitotic and meiotic DSBs as well as in meiotic DNA damage checkpoint activation in the C. elegans germline. ztf-8 mutants exhibit specific sensitivity to γ-irradiation and hydroxyurea, mitotic nuclear arrest at S-phase accompanied by activation of the ATL-1 and CHK-1 DNA damage checkpoint kinases, as well as accumulation of both mitotic and meiotic recombination intermediates, indicating that ZTF-8 functions in DSBR. However, impaired meiotic DSBR progression partially fails to trigger the CEP-1/p53-dependent DNA damage checkpoint in late pachytene, also supporting a role for ZTF-8 in meiotic DDR. ZTF-8 partially co-localizes with the 9-1-1 DDR complex and interacts with MRT-2/Rad1, a component of this complex. The human RHINO protein rescues the phenotypes observed in ztf-8 mutants, suggesting functional conservation across species. We propose that ZTF-8 is involved in promoting repair at stalled replication forks and meiotic DSBs by transducing DNA damage checkpoint signaling via the 9-1-1 pathway. Our findings define a conserved function for ZTF-8/RHINO in promoting genomic stability in the germline.

  20. Squalene Inhibits ATM-Dependent Signaling in γIR-Induced DNA Damage Response through Induction of Wip1 Phosphatase.

    Directory of Open Access Journals (Sweden)

    Naoto Tatewaki

    Full Text Available Ataxia telangiectasia mutated (ATM kinase plays a crucial role as a master controller in the cellular DNA damage response. Inhibition of ATM leads to inhibition of the checkpoint signaling pathway. Hence, addition of checkpoint inhibitors to anticancer therapies may be an effective targeting strategy. A recent study reported that Wip1, a protein phosphatase, de-phosphorylates serine 1981 of ATM during the DNA damage response. Squalene has been proposed to complement anticancer therapies such as chemotherapy and radiotherapy; however, there is little mechanistic information supporting this idea. Here, we report the inhibitory effect of squalene on ATM-dependent DNA damage signals. Squalene itself did not affect cell viability and the cell cycle of A549 cells, but it enhanced the cytotoxicity of gamma-irradiation (γIR. The in vitro kinase activity of ATM was not altered by squalene. However, squalene increased Wip1 expression in cells and suppressed ATM activation in γIR-treated cells. Consistent with the potential inhibition of ATM by squalene, IR-induced phosphorylation of ATM effectors such as p53 (Ser15 and Chk1 (Ser317 was inhibited by cell treatment with squalene. Thus, squalene inhibits the ATM-dependent signaling pathway following DNA damage through intracellular induction of Wip1 expression.

  1. Squalene Inhibits ATM-Dependent Signaling in γIR-Induced DNA Damage Response through Induction of Wip1 Phosphatase.

    Science.gov (United States)

    Tatewaki, Naoto; Konishi, Tetsuya; Nakajima, Yuki; Nishida, Miyako; Saito, Masafumi; Eitsuka, Takahiro; Sakamaki, Toshiyuki; Ikekawa, Nobuo; Nishida, Hiroshi

    2016-01-01

    Ataxia telangiectasia mutated (ATM) kinase plays a crucial role as a master controller in the cellular DNA damage response. Inhibition of ATM leads to inhibition of the checkpoint signaling pathway. Hence, addition of checkpoint inhibitors to anticancer therapies may be an effective targeting strategy. A recent study reported that Wip1, a protein phosphatase, de-phosphorylates serine 1981 of ATM during the DNA damage response. Squalene has been proposed to complement anticancer therapies such as chemotherapy and radiotherapy; however, there is little mechanistic information supporting this idea. Here, we report the inhibitory effect of squalene on ATM-dependent DNA damage signals. Squalene itself did not affect cell viability and the cell cycle of A549 cells, but it enhanced the cytotoxicity of gamma-irradiation (γIR). The in vitro kinase activity of ATM was not altered by squalene. However, squalene increased Wip1 expression in cells and suppressed ATM activation in γIR-treated cells. Consistent with the potential inhibition of ATM by squalene, IR-induced phosphorylation of ATM effectors such as p53 (Ser15) and Chk1 (Ser317) was inhibited by cell treatment with squalene. Thus, squalene inhibits the ATM-dependent signaling pathway following DNA damage through intracellular induction of Wip1 expression. PMID:26824362

  2. PD-L1 Regulates a Critical Checkpoint for Autoimmune Myocarditis and Pneumonitis in MRL mice1

    OpenAIRE

    Lucas, Julie A.; Menke, Julia; Rabacal, Whitney A.; Schoen, Frederick J.; Sharpe, Arlene H.; Kelley, Vicki R.

    2008-01-01

    MRL/MpJ-Faslpr (MRL-Faslpr) mice develop a spontaneous T cell and macrophage (Mø) dependent autoimmune disease that shares features with human lupus. Interactions via the PD-1/PD-L1 pathway down-regulate immune responses and provide a negative regulatory checkpoint in mediating tolerance and autoimmune disease. Therefore, we tested the hypothesis that the PD-1/PD-L1 pathway suppresses lupus nephritis and the systemic illness in MRL-Faslpr mice. For this purpose, we compared kidney and systemi...

  3. Mlp1 Acts as a Mitotic Scaffold to Spatially Regulate Spindle Assembly Checkpoint Proteins in Aspergillus nidulans

    OpenAIRE

    De Souza, Colin P.; Hashmi, Shahr B.; Nayak, Tania; Oakley, Berl; Osmani, Stephen A.

    2009-01-01

    During open mitosis several nuclear pore complex (NPC) proteins have mitotic specific localizations and functions. We find that the Aspergillus nidulans Mlp1 NPC protein has previously unrealized mitotic roles involving spatial regulation of spindle assembly checkpoint (SAC) proteins. In interphase, An-Mlp1 tethers the An-Mad1 and An-Mad2 SAC proteins to NPCs. During a normal mitosis, An-Mlp1, An-Mad1, and An-Mad2 localize similarly on, and around, kinetochores until telophase when they trans...

  4. Effect of Spindle Checkpoint on Akt2-mediated Paclitaxel-resistance in A2780 Ovarian Cancer Cells

    Institute of Scientific and Technical Information of China (English)

    周婷; 鲍引娣; 叶双梅; 翁丹卉; 陈刚; 卢运萍; 马丁; 王世宣

    2010-01-01

    Recent evidence has suggested that Akt2 plays an important role in the protection of cells from paclitaxel(PTX)-induced apoptosis and control of the cell cycle.In addition,some scholars suggested that the PTX sensitivity depends on a functional spindle assembly checkpoint.In the present study,we investigated the role of the Akt2/Bub1 cross-talking in apoptosis and cell cycle after exposure of the A2780 ovarian cancer cells to paclitaxel(PTX).Recombinant expression plasmid WT-Akt2 was transfected into A2780 ...

  5. Structure of the sporulation histidine kinase inhibitor Sda from Bacillus subtilis and insights into its solution state

    Energy Technology Data Exchange (ETDEWEB)

    Jacques, David A.; Streamer, Margaret; Rowland, Susan L.; King, Glenn F.; Guss, J. Mitchell; Trewhella, J.; Langley, David B.; (Sydney); (Queensland)

    2009-09-02

    The crystal structure of the DNA-damage checkpoint inhibitor of sporulation, Sda, from Bacillus subtilis, has been solved by the MAD technique using selenomethionine-substituted protein. The structure closely resembles that previously solved by NMR, as well as the structure of a homologue from Geobacillus stearothermophilus solved in complex with the histidine kinase KinB. The structure contains three molecules in the asymmetric unit. The unusual trimeric arrangement, which lacks simple internal symmetry, appears to be preserved in solution based on an essentially ideal fit to previously acquired scattering data for Sda in solution. This interpretation contradicts previous findings that Sda was monomeric or dimeric in solution. This study demonstrates the difficulties that can be associated with the characterization of small proteins and the value of combining multiple biophysical techniques. It also emphasizes the importance of understanding the physical principles behind these techniques and therefore their limitations.

  6. Checkpoint inhibitors in cancer immunotherapy: Cross reactivity of a CTLA-4 antibody and IDO-inhibitor L-1MT in pigs

    DEFF Research Database (Denmark)

    Al-Shatrawi, Zina Adil; Frøsig, Thomas Mørch; Jungersen, Gregers

    Blockade of checkpoint inhibitors has recently shown very convincing results in the treatment of cancer. One key target is CTLA-4, which has been demonstrated to be a potent negative regulator of lymphocyte activation. The treatment with the FDA-approved fully human CTLA-4 monoclonal antibody...... a non-specific activation of porcine T cells. This will be further investigated to provide the basis for in vivo studies investigating checkpoint inhibitor blockade in combination with other cancer immunotherapies. Eventually our goal is to establish pigs as an alternative large animal model...... Ipilimumab increases anticancer T-cell reactivity and overall survival of metastatic cancer patients. Indole-amine 2,3-dioxygenase (IDO) is another checkpoint inhibitor which suppresses T-cell immunity by the depletion of tryptophan in the T-cell microenvironment, and also inhibition of IDO by L-1...

  7. Combining the pan-aurora kinase inhibitor AMG 900 with histone deacetylase inhibitors enhances antitumor activity in prostate cancer

    International Nuclear Information System (INIS)

    Histone deacetylase inhibitors (HDACIs) are being tested in clinical trials for the treatment of solid tumors. While most studies have focused on the reexpression of silenced tumor suppressor genes, a number of genes/pathways are downregulated by HDACIs. This provides opportunities for combination therapy: agents that further disable these pathways through inhibition of residual gene function are speculated to enhance cell death in combination with HDACIs. A previous study from our group indicated that mitotic checkpoint kinases such as PLK1 and Aurora A are downregulated by HDACIs. We used in vitro and in vivo xenograft models of prostate cancer (PCA) to test whether combination of HDACIs with the pan-aurora kinase inhibitor AMG 900 can synergistically or additively kill PCA cells. AMG 900 and HDACIs synergistically decreased cell proliferation activity and clonogenic survival in DU-145, LNCaP, and PC3 PCA cell lines compared to single-agent treatment. Cellular senescence, polyploidy, and apoptosis was significantly increased in all cell lines after combination treatment. In vivo xenograft studies indicated decreased tumor growth and decreased aurora B kinase activity in mice treated with low-dose AMG 900 and vorinostat compared to either agent alone. Pharmacodynamics was assessed by scoring for phosphorylated histone H3 through immunofluorescence. Our results indicate that combination treatment with low doses of AMG 900 and HDACIs could be a promising therapy for future clinical trials against PCA

  8. Quantitative Phosphoproteomics Reveals Wee1 Kinase as a Therapeutic Target in a Model of Proneural Glioblastoma.

    Science.gov (United States)

    Lescarbeau, Rebecca S; Lei, Liang; Bakken, Katrina K; Sims, Peter A; Sarkaria, Jann N; Canoll, Peter; White, Forest M

    2016-06-01

    Glioblastoma (GBM) is the most common malignant primary brain cancer. With a median survival of about a year, new approaches to treating this disease are necessary. To identify signaling molecules regulating GBM progression in a genetically engineered murine model of proneural GBM, we quantified phosphotyrosine-mediated signaling using mass spectrometry. Oncogenic signals, including phosphorylated ERK MAPK, PI3K, and PDGFR, were found to be increased in the murine tumors relative to brain. Phosphorylation of CDK1 pY15, associated with the G2 arrest checkpoint, was identified as the most differentially phosphorylated site, with a 14-fold increase in phosphorylation in the tumors. To assess the role of this checkpoint as a potential therapeutic target, syngeneic primary cell lines derived from these tumors were treated with MK-1775, an inhibitor of Wee1, the kinase responsible for CDK1 Y15 phosphorylation. MK-1775 treatment led to mitotic catastrophe, as defined by increased DNA damage and cell death by apoptosis. To assess the extensibility of targeting Wee1/CDK1 in GBM, patient-derived xenograft (PDX) cell lines were also treated with MK-1775. Although the response was more heterogeneous, on-target Wee1 inhibition led to decreased CDK1 Y15 phosphorylation and increased DNA damage and apoptosis in each line. These results were also validated in vivo, where single-agent MK-1775 demonstrated an antitumor effect on a flank PDX tumor model, increasing mouse survival by 1.74-fold. This study highlights the ability of unbiased quantitative phosphoproteomics to reveal therapeutic targets in tumor models, and the potential for Wee1 inhibition as a treatment approach in preclinical models of GBM. Mol Cancer Ther; 15(6); 1332-43. ©2016 AACR. PMID:27196784

  9. Tetrandrine: A Potent Abrogator of G2 Checkpoint Function in Tumor Cells and Its Mechanism

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    (M phase). Endosomatic experiment showed that tetrandrine caused tumor growth delay in irradiated mice. Conclusion Tetrandrine boosts the cell killing activity of irradiation both in vitro and in vivo. Tetrandrine is a potent abrogator for G2 checkpoint control and can sensitize the cells to radiation.

  10. How oocytes try to get it right: spindle checkpoint control in meiosis.

    Science.gov (United States)

    Touati, Sandra A; Wassmann, Katja

    2016-06-01

    The generation of a viable, diploid organism depends on the formation of haploid gametes, oocytes, and spermatocytes, with the correct number of chromosomes. Halving the genome requires the execution of two consecutive specialized cell divisions named meiosis I and II. Unfortunately, and in contrast to male meiosis, chromosome segregation in oocytes is error prone, with human oocytes being extraordinarily "meiotically challenged". Aneuploid oocytes, that are with the wrong number of chromosomes, give rise to aneuploid embryos when fertilized. In humans, most aneuploidies are lethal and result in spontaneous abortions. However, some trisomies survive to birth or even adulthood, such as the well-known trisomy 21, which gives rise to Down syndrome (Nagaoka et al. in Nat Rev Genet 13:493-504, 2012). A staggering 20-25 % of oocytes ready to be fertilized are aneuploid in humans. If this were not bad enough, there is an additional increase in meiotic missegregations as women get closer to menopause. A woman above 40 has a risk of more than 30 % of getting pregnant with a trisomic child. Worse still, in industrialized western societies, child birth is delayed, with women getting their first child later in life than ever. This trend has led to an increase of trisomic pregnancies by 70 % in the last 30 years (Nagaoka et al. in Nat Rev Genet 13:493-504, 2012; Schmidt et al. in Hum Reprod Update 18:29-43, 2012). To understand why errors occur so frequently during the meiotic divisions in oocytes, we review here the molecular mechanisms at works to control chromosome segregation during meiosis. An important mitotic control mechanism, namely the spindle assembly checkpoint or SAC, has been adapted to the special requirements of the meiotic divisions, and this review will focus on our current knowledge of SAC control in mammalian oocytes. Knowledge on how chromosome segregation is controlled in mammalian oocytes may help to identify risk factors important for questions

  11. Structural and functional analysis of the Crb2–BRCT2 domain reveals distinct roles in checkpoint signaling and DNA damage repair

    OpenAIRE

    Kilkenny, Mairi L.; Doré, Andrew S.; Roe, S. Mark; Nestoras, Konstantinos; Ho, Jenny C. Y.; Watts, Felicity Z.; Pearl, Laurence H.

    2008-01-01

    Schizosaccharomyces pombe Crb2 is a checkpoint mediator required for the cellular response to DNA damage. Like human 53BP1 and Saccharomyces cerevisiae Rad9 it contains Tudor2 and BRCT2 domains. Crb2-Tudor2 domain interacts with methylated H4K20 and is required for recruitment to DNA dsDNA breaks. The BRCT2 domain is required for dimerization, but its precise role in DNA damage repair and checkpoint signaling is unclear. The crystal structure of the Crb2–BRCT2 domain, alone and in complex wit...

  12. Interactions of checkpoint-genes RAD9, RAD17, RAD24 and RAD53 determining radioresistance of Yeast Saccharomyces Cerevisiae

    International Nuclear Information System (INIS)

    The mechanisms of genetic control of progress through the division cell cycle (checkpoint-control) in yeast Saccharomyces cerevisiae have been studied intensively. To investigate the role of checkpoint-genes RAD9, RAD17, RAD24, RAD53 in cell radioresistance we have investigated cell sensitivity of double mutants to γ-ray. Double mutants involving various combinations with rad9Δ show epistatic interactions, i.e. the sensitivity of the double mutants to γ-ray was no greater than that of more sensitive of the two single mutants. This suggests that all these genes govern the same pathway. This group of genes was named RAD9-epistasis group. It is interesting to note that the genes RAD9 and RAD53 have positive effect but RAD17 and RAD24 have negative effect on radiosensitivity of yeast cells. Interactions between mutations may differ depending on the agent γ-ray or UV-light, for example mutations rad9Δ and rad24Δ show additive effect for γ-ray and epistatic effect for UV-light

  13. Stranglehold on the spindle assembly checkpoint: the human papillomavirus E2 protein provokes BUBR1-dependent aneuploidy.

    Science.gov (United States)

    Tan, Chye Ling; Teissier, Sébastien; Gunaratne, Jayantha; Quek, Ling Shih; Bellanger, Sophie

    2015-01-01

    The Human Papillomavirus (HPV) E2 protein, which inhibits the E6 and E7 viral oncogenes, is believed to have anti-oncogenic properties. Here, we challenge this view and show that HPV-18 E2 over-activates the Spindle Assembly Checkpoint (SAC) and induces DNA breaks in mitosis followed by aneuploidy. This phenotype is associated with interaction of E2 with the Mitotic Checkpoint Complex (MCC) proteins Cdc20, MAD2 and BUBR1. While BUBR1 silencing rescues the mitotic phenotype induced by E2, p53 silencing or presence of E6/E7 (inactivating p53 and increasing BUBR1 levels respectively) both amplify it. This work pinpoints E2 as a key protein in the initiation of HPV-induced cervical cancer and identifies the SAC as a target for oncogenic pathogens. Moreover, our results suggest a role of p53 in regulating the mitotic process itself and highlight SAC over-activation in a p53-negative context as a highly pathogenic event. PMID:25789401

  14. G1 checkpoint is compromised in mouse ESCs due to functional uncoupling of p53-p21Waf1 signaling.

    Science.gov (United States)

    Suvorova, Irina I; Grigorash, Bogdan B; Chuykin, Ilya A; Pospelova, Tatiana V; Pospelov, Valery A

    2016-01-01

    Mouse embryonic stem cells (mESCs) lack of G1 checkpoint despite that irradiation (IR) activates ATM/ATR-mediated DDR signaling pathway. The IR-induced p53 localizes in the nuclei and up-regulates p21/Waf1 transcription but that does not lead to accumulation of p21/Waf1 protein. The negative control of the p21Waf1 expression appears to occur at 2 levels of regulation. First, both p21/Waf1 gene transcription and the p21/Waf1 protein content increase in mESCs treated with histone-deacetylase inhibitors, implying its epigenetic regulation. Second, proteasome inhibitors cause the p21/Waf1 accumulation, indicating that the protein is a subject of proteasome-dependent degradation in ESСs. Then, the dynamics of IR-induced p21Waf1 protein show its accumulation at long-term time points (3 and 5 days) that coincides with an increase in the proportion of G1-phase cells, down-regulation of Oct4 and Nanog pluripotent gene transcription and activation of endoderm-specific genes sox17 and afp. In addition, nutlin-dependent stabilization of p53 in mESC was also accompanied by the accumulation of p21/Waf1 as well as restoration of G1 checkpoint and an onset of differentiation. Thus, the lack of functional p21/Waf1 is indispensable for maintaining self-renewal and pluripotency of mESCs. PMID:26636245

  15. Ermenilerin Kontrol Noktası: İskenderun Limanı Alexandretta Port - Checkpoint For Armenians

    Directory of Open Access Journals (Sweden)

    Naim ÜRKMEZ

    2013-07-01

    Full Text Available The period of Yavuz Sultan Selim and the Ottoman Empire’s entering Alexandretta until the first half of the 19th century had identity of a very small village. Right to the end of the century, the industry revolution’s impact and trading goods’ large amount of transport means gained importance starting especially in the city of Aleppo and then in one of South Anatolia’s natural ports as of the day the preliminary plan came out. After the 1890’s the increase of Armenian activities in Anatolia and the outbreak of revolts in many other places parallel the Ottoman government’s large forces’ involvement to prevent and be able to keep Armenian rebels under control, taking various measures. Abdul Hamid II started under this negative initiative; the Sultan tried to resist in various ways. From these measures in any of the provinces of Aleppo, Mamuretülaziz, Adana, Kayseri, Bitlis, Van, Diyarbekir, or Erzurum, Armenians living in the diaspora and connecting supplier port, as in Alexandretta, have a checkpoint facility. Sultan Abdul Hamid II’s direction of the facility is seen at the checkpoint from the dock outside rising or Anatolia geography’s various residential areas incoming Armenian travelers often reserved monthly lists. In addition to this, England in the grip of Cyprus was able to check Armenians’ entries into Anatolia set by a weapons and bombs training field. It is understood that this matter is elaborated on further in books prepared from lists. These books will come to light with the acceleration of the classification of records. Yavuz Sultan Selim döneminde Osmanlı hâkimiyetine giren İskenderun, 19. yüzyılın ilk yarısına kadar çok küçük bir köy hüviyetinde kalmıştır. Yüzyılın sonuna doğru sanayi devriminin etkisi ve ticari emtianın çokça taşınması vesilesi ile önem kazanmaya başlayan şehir özellikle Halep ve ardı ile Güney Anadolu’nun doğal bir limanı olarak gün geçtikçe ön plana

  16. Protein kinase CK2 in human diseases

    DEFF Research Database (Denmark)

    Guerra, Barbara; Issinger, Olaf-Georg

    2008-01-01

    Protein kinase CK2 (formerly referred to as casein kinase II) is an evolutionary conserved, ubiquitous protein kinase. There are two paralog catalytic subunits, i.e. alpha (A1) and alpha' (A2). The alpha and alpha' subunits are linked to two beta subunits to produce a heterotetrameric structure....... The catalytic alpha subunits are distantly related to the CMGC subfamily of kinases, such as the Cdk kinases. There are some peculiarities associated with protein kinase CK2, which are not found with most other protein kinases: (i) the enzyme is constitutively active, (ii) it can use ATP and GTP and...... specifically target this protein kinase [10]. Since not all the aspects of what has been published on CK2 can be covered in this review, we would like to recommend the following reviews; (i) for general information on CK2 [11-18] and (ii) with a focus on aberrant CK2 [19-22]....

  17. Degradation of Activated Protein Kinases by Ubiquitination

    OpenAIRE

    Lu, Zhimin; Hunter, Tony

    2009-01-01

    Protein kinases are important regulators of intracellular signal transduction pathways and play critical roles in diverse cellular functions. Once a protein kinase is activated, its activity is subsequently downregulated through a variety of mechanisms. Accumulating evidence indicates that the activation of protein kinases commonly initiates their downregulation via the ubiquitin/proteasome pathway. Failure to regulate protein kinase activity or expression levels can cause human diseases.

  18. Determinants of homodimerization specificity in histidine kinases

    OpenAIRE

    Ashenberg, Orr; Rozen-Gagnon, Kathryn; Laub, Michael T; Keating, Amy E.

    2011-01-01

    Two-component signal transduction pathways consisting of a histidine kinase and a response regulator are used by prokaryotes to respond to diverse environmental and intracellular stimuli. Most species encode numerous paralogous histidine kinases that exhibit significant structural similarity. Yet in almost all known examples, histidine kinases are thought to function as homodimers. We investigated the molecular basis of dimerization specificity, focusing on the model histidine kinase EnvZ and...

  19. The Level of Europium-154 Contaminating Samarium-153-EDTMP Activates the Radiation Alarm System at the US Homeland Security Checkpoints

    Directory of Open Access Journals (Sweden)

    Mohammed Najeeb Al Hallak

    2009-08-01

    Full Text Available 153Sm-EDTMP is a radiopharmaceutical composed of EDTMP (ethylenediamine-tetramethylenephosphonate and Samarium-153 [1]. 153Sm-EDTMP has an affinity for skeletal tissue and concentrates in areas with increased bone turnover; thus, it is successfully used in relieving pain related to diffuse bone metastases [1]. The manufacturing process of 153Sm-EDTMP leads to contamination with 154Eu (Europium-154 [2]. A previous study only alluded to the retention of 154Eu in the bones after receiving treatment with 153Sm-EDTMP [2]. Activation of the alarm at security checkpoints after 153Sm-EDTMP therapy has not been previously reported. Two out of 15 patients who received 153Sm-EDTMP at Roger Maris Cancer Center (Fargo, N. Dak., USA activated the radiation activity sensors while passing through checkpoints; one at a US airport and the other while crossing theAmerican-Canadian border. We assume that the 154Eu which remained in the patients’ bones activated the sensors. Methods: In order to investigate this hypothesis, we obtained the consent from 3 of our 15 patients who received 153Sm-EDTMP within the previous 4 months to 2 years, including the patient who had activated the radiation alarm at the airport. The patients were scanned with a handheld detector and a gamma camera for energies from 511 keV to 1.3 MeV. Results: All three patients exhibited identical spectral images, and further analysis showed that the observed spectra are the result of 154Eu emissions. Conclusion: Depending on the detection thresholds and windows used by local and federal authorities, the remaining activity of 154Eu retained in patients who received 153Sm-EDTMP could be sufficient enough to increase the count rates above background levels and activate the sensors. At Roger Maris Cancer Center, patients are now informed of the potential consequences of 153Sm-EDTMP therapy prior to initiating treatment. In addition, patients treated with 153Sm-EDTMP at Roger Maris Cancer Center

  20. DMPD: Bruton's tyrosine kinase (Btk)-the critical tyrosine kinase in LPS signalling? [Dynamic Macrophage Pathway CSML Database

    Lifescience Database Archive (English)

    Full Text Available 15081522 Bruton's tyrosine kinase (Btk)-the critical tyrosine kinase in LPS signall...ruton's tyrosine kinase (Btk)-the critical tyrosine kinase in LPS signalling? PubmedID 15081522 Title Bruton...'s tyrosine kinase (Btk)-the critical tyrosine kinase in LPS signalling? Authors

  1. Cell-cycle dependent expression of a translocation-mediated fusion oncogene mediates checkpoint adaptation in rhabdomyosarcoma.

    Science.gov (United States)

    Kikuchi, Ken; Hettmer, Simone; Aslam, M Imran; Michalek, Joel E; Laub, Wolfram; Wilky, Breelyn A; Loeb, David M; Rubin, Brian P; Wagers, Amy J; Keller, Charles

    2014-01-01

    Rhabdomyosarcoma is the most commonly occurring soft-tissue sarcoma in childhood. Most rhabdomyosarcoma falls into one of two biologically distinct subgroups represented by alveolar or embryonal histology. The alveolar subtype harbors a translocation-mediated PAX3:FOXO1A fusion gene and has an extremely poor prognosis. However, tumor cells have heterogeneous expression for the fusion gene. Using a conditional genetic mouse model as well as human tumor cell lines, we show that that Pax3:Foxo1a expression is enriched in G2 and triggers a transcriptional program conducive to checkpoint adaptation under stress conditions such as irradiation in vitro and in vivo. Pax3:Foxo1a also tolerizes tumor cells to clinically-established chemotherapy agents and emerging molecularly-targeted agents. Thus, the surprisingly dynamic regulation of the Pax3:Foxo1a locus is a paradigm that has important implications for the way in which oncogenes are modeled in cancer cells. PMID:24453992

  2. Cell-cycle dependent expression of a translocation-mediated fusion oncogene mediates checkpoint adaptation in rhabdomyosarcoma.

    Directory of Open Access Journals (Sweden)

    Ken Kikuchi

    2014-01-01

    Full Text Available Rhabdomyosarcoma is the most commonly occurring soft-tissue sarcoma in childhood. Most rhabdomyosarcoma falls into one of two biologically distinct subgroups represented by alveolar or embryonal histology. The alveolar subtype harbors a translocation-mediated PAX3:FOXO1A fusion gene and has an extremely poor prognosis. However, tumor cells have heterogeneous expression for the fusion gene. Using a conditional genetic mouse model as well as human tumor cell lines, we show that that Pax3:Foxo1a expression is enriched in G2 and triggers a transcriptional program conducive to checkpoint adaptation under stress conditions such as irradiation in vitro and in vivo. Pax3:Foxo1a also tolerizes tumor cells to clinically-established chemotherapy agents and emerging molecularly-targeted agents. Thus, the surprisingly dynamic regulation of the Pax3:Foxo1a locus is a paradigm that has important implications for the way in which oncogenes are modeled in cancer cells.

  3. Human papillomavirus type 16 E7 oncoprotein engages but does not abrogate the mitotic spindle assembly checkpoint

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Yueyang [Division of Infectious Diseases, Brigham and Women' s Hospital and Biological and Biomedical Sciences Program, Harvard Medical School, Boston, MA 02115 (United States); Munger, Karl, E-mail: kmunger@rics.bwh.harvard.edu [Division of Infectious Diseases, Brigham and Women' s Hospital and Biological and Biomedical Sciences Program, Harvard Medical School, Boston, MA 02115 (United States)

    2012-10-10

    The mitotic spindle assembly checkpoint (SAC) ensures faithful chromosome segregation during mitosis by censoring kinetochore-microtubule interactions. It is frequently rendered dysfunctional during carcinogenesis causing chromosome missegregation and genomic instability. There are conflicting reports whether the HPV16 E7 oncoprotein drives chromosomal instability by abolishing the SAC. Here we report that degradation of mitotic cyclins is impaired in cells with HPV16 E7 expression. RNAi-mediated depletion of Mad2 or BubR1 indicated the involvement of the SAC, suggesting that HPV16 E7 expression causes sustained SAC engagement. Mutational analyses revealed that HPV16 E7 sequences that are necessary for retinoblastoma tumor suppressor protein binding as well as sequences previously implicated in binding the nuclear and mitotic apparatus (NuMA) protein and in delocalizing dynein from the mitotic spindle contribute to SAC engagement. Importantly, however, HPV16 E7 does not markedly compromise the SAC response to microtubule poisons.

  4. Fault-Tolerance through Message-logging and Check-pointing: Disaster Recovery for CORBA-based Distributed Bank Servers

    CERN Document Server

    Vassev, Emil; Kuang, Heng

    2009-01-01

    This report presents results of our endeavor towards developing a failure-recovery variant of a CORBA-based bank server that provides fault tolerance features through message logging and checkpoint logging. In this group of projects, three components were developed to satisfy the requirements: 1) a message-logging protocol for the branch servers of the distributed banking system to log required information; 2) a recovery module that restarts the bank server using the message log to help the restarted bank server process subsequent requests for various operations; 3) a monitor module that periodically checks whether the bank server is down and helps the recovery module restart the bank server if the latter has crashed.

  5. Targeted therapies and immune checkpoint inhibitors in the treatment of metastatic melanoma patients: a guide and update for pathologists.

    Science.gov (United States)

    Kakavand, Hojabr; Wilmott, James S; Long, Georgina V; Scolyer, Richard A

    2016-02-01

    The previously dismal prospects for patients with advanced stage metastatic melanoma have greatly improved in recent years. Enhanced understanding of both the pathogenesis of melanoma and its molecular drivers, as well as the importance and regulation of anti-tumour immune responses, have provided new therapeutic opportunities for melanoma patients. There are two major distinct categories of systemic treatments with activity for patients with metastatic melanoma: (1) targeted therapies, which act to inhibit the oncogenes that drive the aberrant growth and dissemination of the tumour; and (2) immune checkpoint inhibitor therapies, which act to enhance anti-tumour immune responses by blocking negative regulators of immunity. Pathologists play a critical and expanding role in the selection of the most appropriate treatment for individual metastatic melanoma patients in the modern era of personalised/precision medicine. The molecular pathology testing of melanoma tumour tissue for the presence of targetable oncogenic mutations is already part of routine practice in many institutions. In addition, other potential oncogenic therapeutic targets continue to be identified and pathology testing techniques must readily adapt to this rapidly changing field. Recent research findings suggest that pathological assessment of tumour associated immune cells and immunosuppressive ligand expression of the tumour are likely to be important in identifying patients most likely to benefit from immune checkpoint inhibitors. Similarly, pathological and molecular observations of on-treatment tumour tissue biopsies taken from patients on targeted therapies have provided new insights into the mechanisms of action of targeted molecular therapies, have contributed to the identification of resistance mechanisms to these novel therapies and may be of higher value for selecting patients most likely to benefit from therapies. These data have already provided a rational biological basis for the

  6. RIP Kinases Initiate Programmed Necrosis

    Institute of Scientific and Technical Information of China (English)

    Lorenzo Galluzzi; Oliver Kepp; Guido Kroemer

    2009-01-01

    Some lethal stimuli can induce either apoptosis or necrosis, depending on the cell type and/or experimental setting. Until recently,the molecular bases of this phenomenon were largely unknown. Now, two members of the receptor-interacting serine-threonine kinase (RIP) family, RIP1 and RIP3, have been demonstrated to control the switch between apoptotic and necrotic cell death.Some mechanistic details, however, remain controversial.

  7. Thymidine kinase diversity in bacteria

    DEFF Research Database (Denmark)

    Sandrini, Michael; Clausen, A.R.; Munch-Petersen, B.;

    2006-01-01

    Thymidine kinases (TKs) appear to be almost ubiquitous and are found in nearly all prokaryotes, eukaryotes, and several viruses. They are the key enzymes in thymidine salvage and activation of several anti-cancer and antiviral drugs. We show that bacterial TKs can be subdivided into 2 groups. The...... TKs from Gram-positive bacteria are more closely related to the eukaryotic TK1 enzymes than are TKs from Gram-negative bacteria....

  8. Pantothenate Kinase-Associated Neurodegeneration

    OpenAIRE

    Meitinger, Thomas; Prokisch, Holger; Hartig, Monika B.; Klopstock, Thomas

    2012-01-01

    Pantothenate kinase-associated neurodegeneration (PKAN) is a hereditary progressive disorder and the most frequent form of neurodegeneration with brain iron accumulation (NBIA). PKAN patients present with a progressive movement disorder, dysarthria, cognitive impairment and retinitis pigmentosa. In magnetic resonance imaging, PKAN patients exhibit the pathognonomic "eye of the tiger" sign in the globus pallidus which corresponds to iron accumulation and gliosis as shown in neuropathological e...

  9. Oncoprotein protein kinase antibody kit

    Science.gov (United States)

    Karin, Michael; Hibi, Masahiko; Lin, Anning

    2008-12-23

    An isolated polypeptide (JNK) characterized by having a molecular weight of 46 kD as determined by reducing SDS-PAGE, having serine and threonine kinase activity, phosphorylating the c-Jun N-terminal activation domain and polynucleotide sequences and method of detection of JNK are provided herein. JNK phosphorylates c-Jun N-terminal activation domain which affects gene expression from AP-1 sites.

  10. Thymidine kinase diversity in bacteria

    DEFF Research Database (Denmark)

    Sandrini, Michael; Clausen, A.R.; Munch-Petersen, B.; Piskur, Jure

    Thymidine kinases (TKs) appear to be almost ubiquitous and are found in nearly all prokaryotes, eukaryotes, and several viruses. They are the key enzymes in thymidine salvage and activation of several anti-cancer and antiviral drugs. We show that bacterial TKs can be subdivided into 2 groups. The...... TKs from Gram-positive bacteria are more closely related to the eukaryotic TK1 enzymes than are TKs from Gram-negative bacteria....

  11. Regulation and function of TPL-2,an IκB kinase-regulated MAP kinase kinase kinase

    Institute of Scientific and Technical Information of China (English)

    Thorsten Gantke; Srividya Sriskantharajah; Steven C Ley

    2011-01-01

    The IκB kinase(IKK)complex plays a well-documented role in innate and adaptive immunity.This function has been widely attributed to its role as the central activator of the NF-κB family of transcription factors.However,another important consequence of IKK activation is the regulation of TPL-2,a MEK kinase that is required for activation of ERK-1/2 MAP kinases in myeioid cells following Toll-like receptor and TNF receptor stimulation.In unstimulated cells,TPL-2 is stoichiometrically complexed with the NF-κB inhibitory protein NF-κB1 p105,which blocks TPL-2 access to its substrate MEK,and the ubiquitin-binding protein ABIN-2(A20-binding inhibitor of NF-κB 2),both of which are required to maintain TPL-2 protein stability.Following agonist stimulation,the IKK complex phosphorylates p105,triggering its K48-1inked ubiquitination and degradation by the proteasome.This releases TPL-2 from p105-mediated inhibition,facilitating activation of MEK,in addition to modulating NF-κB activation by liberating associated Rel subunits for translocation into the nucleus.IKK-induced proteolysis of 0105,therefore,can directly regulate both NF-κB and ERK MAP kinase activation via NF-κB1 p105.TPL-2 is critical for production of the proinflammatory cytokine TNF during inflammatory responses.Consequently,there has been considerable interest in the pharmaceutical industry to develop selective TPL-2 inhibitors as drugs for the treatment of TNF-dependent inflammatory,diseases,such as rheumatoid arthritis and inflammatory bowel disease.This review summarizes our current understanding of the regulation of TPL-2 signaling function,and also the complex positive and negative roles of TPL-2 in immune and inflammatory responses.

  12. A proteomic approach for comprehensively screening substrates of protein kinases such as Rho-kinase.

    Directory of Open Access Journals (Sweden)

    Mutsuki Amano

    Full Text Available BACKGROUND: Protein kinases are major components of signal transduction pathways in multiple cellular processes. Kinases directly interact with and phosphorylate downstream substrates, thus modulating their functions. Despite the importance of identifying substrates in order to more fully understand the signaling network of respective kinases, efficient methods to search for substrates remain poorly explored. METHODOLOGY/PRINCIPAL FINDINGS: We combined mass spectrometry and affinity column chromatography of the catalytic domain of protein kinases to screen potential substrates. Using the active catalytic fragment of Rho-kinase/ROCK/ROK as the model bait, we obtained about 300 interacting proteins from the rat brain cytosol fraction, which included the proteins previously reported as Rho-kinase substrates. Several novel interacting proteins, including doublecortin, were phosphorylated by Rho-kinase both in vitro and in vivo. CONCLUSIONS/SIGNIFICANCE: This method would enable identification of novel specific substrates for kinases such as Rho-kinase with high sensitivity.

  13. Immunochemical characterization of rat brain protein kinase

    International Nuclear Information System (INIS)

    Polyclonal antibodies against rat brain protein kinase C (the Ca2+/phospholipid-dependent enzyme) were raised in goat. These antibodies can neutralize completely the kinase activity in purified enzyme preparation as well as that in the crude homogenate. Immunoblot analysis of the purified and the crude protein kinase C preparations revealed a major immunoreactive band of 80 kDa. The antibodies also recognize the same enzyme from other rat tissues. Neuronal tissues (cerebral cortex, cerebellum, hypothalamus, and retina) and lymphoid organs (thymus and spleen) were found to be enriched in protein kinase C, whereas lung, kidney, liver, heart, and skeletal muscle contained relatively low amounts of this kinase. Limited proteolysis of the purified rat brain protein kinase C with trypsin results in an initial degradation of the kinase into two major fragments of 48 and 38 kDa. Both fragments are recognized by the antibodies. However, further digestion of the 48-kDa fragment to 45 kDa and the 38-kDa fragment to 33 kDa causes a loss of the immunoreactivity. Upon incubation of the cerebellar extract with Ca2+, the 48-kDa fragment was also identified as a major proteolytic product of protein kinase C. Proteolytic degradation of protein kinase C converts the Ca2+/phospholipid-dependent kinase to an independent form without causing a large impairment of the binding of [3H]phorbol 12,13-dibutyrate. The two major proteolytic fragments were separated by ion exchange chromatography and one of them (45-48 kDa) was identified as a protein kinase and the other (33-38 kDa) as a phorbol ester-binding protein. These results demonstrate that rat brain protein kinase C is composed of two functionally distinct units, namely, a protein kinase and a Ca2+-independent/phospholipid-dependent phorbol ester-binding protein

  14. Regulation of the interaction between protein kinase C-related protein kinase 2 (PRK2) and its upstream kinase, 3-phosphoinositide-dependent protein kinase 1 (PDK1)

    DEFF Research Database (Denmark)

    Dettori, Rosalia; Sonzogni, Silvina; Meyer, Lucas;

    2009-01-01

    The members of the AGC kinase family frequently exhibit three conserved phosphorylation sites: the activation loop, the hydrophobic motif (HM), and the zipper (Z)/turn-motif (TM) phosphorylation site. 3-Phosphoinositide-dependent protein kinase 1 (PDK1) phosphorylates the activation loop of...... numerous AGC kinases, including the protein kinase C-related protein kinases (PRKs). Here we studied the docking interaction between PDK1 and PRK2 and analyzed the mechanisms that regulate this interaction. In vivo labeling of recombinant PRK2 by (32)P(i) revealed phosphorylation at two sites, the...... the mechanism that negatively regulates the docking interaction of PRK2 to the upstream kinase PDK1 is directly linked to the activation mechanism of PRK2 itself. Finally, our results indicate that the mechanisms underlying the regulation of the interaction between PRK2 and PDK1 are specific for PRK2...

  15. Molecular Pathways: Targeting ATR in Cancer Therapy.

    Science.gov (United States)

    Karnitz, Larry M; Zou, Lee

    2015-11-01

    The human ATR gene encodes a kinase that is activated by DNA damage and replication stress as a central transducer of a checkpoint signaling pathway. Once activated, ATR phosphorylates multiple substrates, including the kinase Chk1, to regulate cell-cycle progression, replication fork stability, and DNA repair. These events promote cell survival during replication stress and in cells with DNA damage. Accordingly, there has been the tantalizing possibility that ATR inhibitors would be therapeutically useful, especially if they were more effective in tumor versus normal cells. Indeed, multiple studies have demonstrated that alterations that promote tumorigenesis, such as defects in the ATM-p53 pathway, constitutive oncogene activation, and acquisition of the alternative lengthening of telomeres pathway, render tumor cells sensitive to ATR inhibitor monotherapy and/or increase the synergy between ATR inhibitors and genotoxic chemotherapies. Now, nearly two decades after the discovery of ATR, two highly selective and potent ATR inhibitors, AZD6738 and VX-970, are in early-phase clinical trials either as monotherapies or paired with a variety of genotoxic chemotherapies. These trials will generate important insights into the effects of ATR inhibition in humans and the potential role of inhibiting this kinase in the treatment of human malignancies. PMID:26362996

  16. Diacylglycerol Kinase Inhibition and Vascular Function

    OpenAIRE

    Choi, Hyehun; Allahdadi, Kyan J.; Tostes, Rita C A; Webb, R. Clinton

    2009-01-01

    Diacylglycerol kinases (DGKs), a family of lipid kinases, convert diacylglycerol (DG) to phosphatidic acid (PA). Acting as a second messenger, DG activates protein kinase C (PKC). PA, a signaling lipid, regulates diverse functions involved in physiological responses. Since DGK modulates two lipid second messengers, DG and PA, regulation of DGK could induce related cellular responses. Currently, there are 10 mammalian isoforms of DGK that are categorized into five groups based on their structu...

  17. P21-activated kinase 4 (PAK4) is required for metaphase spindle positioning and anchoring.

    Science.gov (United States)

    Bompard, G; Rabeharivelo, G; Cau, J; Abrieu, A; Delsert, C; Morin, N

    2013-02-14

    The oncogenic kinase PAK4 was recently found to be involved in the regulation of the G1 phase and the G2/M transition of the cell cycle. We have also identified that PAK4 regulates Ran GTPase activity during mitosis. Here, we show that after entering mitosis, PAK4-depleted cells maintain a prolonged metaphase-like state. In these cells, chromosome congression to the metaphase plate occurs with normal kinetics but is followed by an extended period during which membrane blebbing and spindle rotation are observed. These bipolar PAK4-depleted metaphase-like spindles have a defective astral microtubule (MT) network and are not centered in the cell but are in close contact with the cell cortex. As the metaphase-like state persists, centrosome fragmentation occurs, chromosomes scatter from the metaphase plate and move toward the spindle poles with an active spindle assembly checkpoint, a phenotype that is reminiscent of cohesion fatigue. PAK4 also regulates the acto-myosin cytoskeleton and we report that PAK4 depletion results in the induction of cortical membrane blebbing during prometaphase arrest. However, we show that membrane blebs, which are strongly enriched in phospho-cofilin, are not responsible for the poor anchoring of the spindle. As PAK4 depletion interferes with the localization of components of the dynein/dynactin complexes at the kinetochores and on the astral MTs, we propose that loss of PAK4 could induce a change in the activities of motor proteins. PMID:22450748

  18. Quantitative phospho-proteomics to investigate the polo-like kinase 1-dependent phospho-proteome.

    Science.gov (United States)

    Grosstessner-Hain, Karin; Hegemann, Björn; Novatchkova, Maria; Rameseder, Jonathan; Joughin, Brian A; Hudecz, Otto; Roitinger, Elisabeth; Pichler, Peter; Kraut, Norbert; Yaffe, Michael B; Peters, Jan-Michael; Mechtler, Karl

    2011-11-01

    Polo-like kinase 1 (PLK1) is a key regulator of mitotic progression and cell division, and small molecule inhibitors of PLK1 are undergoing clinical trials to evaluate their utility in cancer therapy. Despite this importance, current knowledge about the identity of PLK1 substrates is limited. Here we present the results of a proteome-wide analysis of PLK1-regulated phosphorylation sites in mitotic human cells. We compared phosphorylation sites in HeLa cells that were or were not treated with the PLK1-inhibitor BI 4834, by labeling peptides via methyl esterification, fractionation of peptides by strong cation exchange chromatography, and phosphopeptide enrichment via immobilized metal affinity chromatography. Analysis by quantitative mass spectrometry identified 4070 unique mitotic phosphorylation sites on 2069 proteins. Of these, 401 proteins contained one or multiple phosphorylation sites whose abundance was decreased by PLK1 inhibition. These include proteins implicated in PLK1-regulated processes such as DNA damage, mitotic spindle formation, spindle assembly checkpoint signaling, and chromosome segregation, but also numerous proteins that were not suspected to be regulated by PLK1. Analysis of amino acid sequence motifs among phosphorylation sites down-regulated under PLK1 inhibition in this data set identified two potential novel variants of the PLK1 consensus motif. PMID:21857030

  19. Expression and prognostic value of the WEE1 kinase in gliomas

    DEFF Research Database (Denmark)

    Music, Darija; Dahlrot, Rikke Hedegaard; Hermansen, Simon Kjær;

    2016-01-01

    High-grade gliomas have an aggressive clinical course and new clinical biomarkers and therapeutic targets are highly needed. WEE1 is a regulator of the G2 checkpoint in glioblastoma (GBM) cells. Inhibition of this kinase has, in experimental glioma studies, been suggested to enhance sensitivity to...... associated with better survival in GBMs (p = 0.002). This was confirmed in multivariate analysis (HR 0.60, p = 0.003) even when adjusted for MGMT status (HR 0.60, p = 0.005). In conclusion, we report a nuclear expression of WEE1 protein in all glioma grades and types. The WEE1 positive nuclear area was...... correlated with malignancy grade but it was inversely associated with prognosis in GBM. Although WEE1 is a frequently occurring protein and has been proposed as a novel target in GBM, the role of WEE1 in glioma patient survival appears to be connected to the MGMT status and is more complex than previously...

  20. Allosteric inhibition of SHP2 phosphatase inhibits cancers driven by receptor tyrosine kinases.

    Science.gov (United States)

    Chen, Ying-Nan P; LaMarche, Matthew J; Chan, Ho Man; Fekkes, Peter; Garcia-Fortanet, Jorge; Acker, Michael G; Antonakos, Brandon; Chen, Christine Hiu-Tung; Chen, Zhouliang; Cooke, Vesselina G; Dobson, Jason R; Deng, Zhan; Fei, Feng; Firestone, Brant; Fodor, Michelle; Fridrich, Cary; Gao, Hui; Grunenfelder, Denise; Hao, Huai-Xiang; Jacob, Jaison; Ho, Samuel; Hsiao, Kathy; Kang, Zhao B; Karki, Rajesh; Kato, Mitsunori; Larrow, Jay; La Bonte, Laura R; Lenoir, Francois; Liu, Gang; Liu, Shumei; Majumdar, Dyuti; Meyer, Matthew J; Palermo, Mark; Perez, Lawrence; Pu, Minying; Price, Edmund; Quinn, Christopher; Shakya, Subarna; Shultz, Michael D; Slisz, Joanna; Venkatesan, Kavitha; Wang, Ping; Warmuth, Markus; Williams, Sarah; Yang, Guizhi; Yuan, Jing; Zhang, Ji-Hu; Zhu, Ping; Ramsey, Timothy; Keen, Nicholas J; Sellers, William R; Stams, Travis; Fortin, Pascal D

    2016-07-01

    The non-receptor protein tyrosine phosphatase SHP2, encoded by PTPN11, has an important role in signal transduction downstream of growth factor receptor signalling and was the first reported oncogenic tyrosine phosphatase. Activating mutations of SHP2 have been associated with developmental pathologies such as Noonan syndrome and are found in multiple cancer types, including leukaemia, lung and breast cancer and neuroblastoma. SHP2 is ubiquitously expressed and regulates cell survival and proliferation primarily through activation of the RAS–ERK signalling pathway. It is also a key mediator of the programmed cell death 1 (PD-1) and B- and T-lymphocyte attenuator (BTLA) immune checkpoint pathways. Reduction of SHP2 activity suppresses tumour cell growth and is a potential target of cancer therapy. Here we report the discovery of a highly potent (IC50 = 0.071 μM), selective and orally bioavailable small-molecule SHP2 inhibitor, SHP099, that stabilizes SHP2 in an auto-inhibited conformation. SHP099 concurrently binds to the interface of the N-terminal SH2, C-terminal SH2, and protein tyrosine phosphatase domains, thus inhibiting SHP2 activity through an allosteric mechanism. SHP099 suppresses RAS–ERK signalling to inhibit the proliferation of receptor-tyrosine-kinase-driven human cancer cells in vitro and is efficacious in mouse tumour xenograft models. Together, these data demonstrate that pharmacological inhibition of SHP2 is a valid therapeutic approach for the treatment of cancers. PMID:27362227

  1. Allosteric small-molecule kinase inhibitors

    DEFF Research Database (Denmark)

    Wu, Peng; Clausen, Mads Hartvig; Nielsen, Thomas E.

    2015-01-01

    Small-molecule kinase inhibitors are invaluable targeted therapeutics for the treatment of various human diseases, especially cancers. While the majority of approved and developed preclinical small-molecule inhibitors are characterized as type I or type II inhibitors that target the ATP......-binding pocket of kinases, the remarkable sequential and structural similarity among ATP pockets renders the selective inhibition of kinases a daunting challenge. Therefore, targeting allosteric pockets of kinases outside the highly conversed ATP pocket has been proposed as a promising alternative to overcome...

  2. MST kinases in development and disease

    OpenAIRE

    Thompson, Barry J.; Sahai, Erik

    2015-01-01

    The mammalian MST kinase family, which is related to the Hippo kinase in Drosophila melanogaster, includes five related proteins: MST1 (also called STK4), MST2 (also called STK3), MST3 (also called STK24), MST4, and YSK1 (also called STK25 or SOK1). MST kinases are emerging as key signaling molecules that influence cell proliferation, organ size, cell migration, and cell polarity. Here we review the regulation and function of these kinases in normal physiology and pathologies, including cance...

  3. Mps1 kinase regulates tumor cell viability via its novel role in mitochondria.

    Science.gov (United States)

    Zhang, X; Ling, Y; Guo, Y; Bai, Y; Shi, X; Gong, F; Tan, P; Zhang, Y; Wei, C; He, X; Ramirez, A; Liu, X; Cao, C; Zhong, H; Xu, Q; Ma, R Z

    2016-01-01

    Targeting mitotic kinase monopolar spindle 1 (Mps1) for tumor therapy has been investigated for many years. Although it was suggested that Mps1 regulates cell viability through its role in spindle assembly checkpoint (SAC), the underlying mechanism remains less defined. In an endeavor to reveal the role of high levels of mitotic kinase Mps1 in the development of colon cancer, we unexpectedly found the amount of Mps1 required for cell survival far exceeds that of maintaining SAC in aneuploid cell lines. This suggests that other functions of Mps1 besides SAC are also employed to maintain cell viability. Mps1 regulates cell viability independent of its role in cytokinesis as the genetic depletion of Mps1 spanning from metaphase to cytokinesis affects neither cytokinesis nor cell viability. Furthermore, we developed a single-cycle inhibition strategy that allows disruption of Mps1 function only in mitosis. Using this strategy, we found the functions of Mps1 in mitosis are vital for cell viability as short-term treatment of mitotic colon cancer cell lines with Mps1 inhibitors is sufficient to cause cell death. Interestingly, Mps1 inhibitors synergize with microtubule depolymerizing drug in promoting polyploidization but not in tumor cell growth inhibition. Finally, we found that Mps1 can be recruited to mitochondria by binding to voltage-dependent anion channel 1 (VDAC1) via its C-terminal fragment. This interaction is essential for cell viability as Mps1 mutant defective for interaction fails to main cell viability, causing the release of cytochrome c. Meanwhile, deprivation of VDAC1 can make tumor cells refractory to loss of Mps1-induced cell death. Collectively, we conclude that inhibition of the novel mitochondrial function Mps1 is sufficient to kill tumor cells. PMID:27383047

  4. Inhibition of c-Abl Kinase Activity Renders Cancer Cells Highly Sensitive to Mitoxantrone

    Science.gov (United States)

    Tuomela, Johanna; Sandholm, Jouko; Aittokallio, Kaappo; Siljamäki, Elina; Kallio, Marko; Kähäri, Veli-Matti; Hietanen, Sakari

    2014-01-01

    Although c-Abl has increasingly emerged as a key player in the DNA damage response, its role in this context is far from clear. We studied the effect of inhibition of c-Abl kinase activity by imatinib with chemotherapy drugs and found a striking difference in cell survival after combined mitoxantrone (MX) and imatinib treatment compared to a panel of other chemotherapy drugs. The combinatory treatment induced apoptosis in HeLa cells and other cancer cell lines but not in primary fibroblasts. The difference in MX and doxorubicin was related to significant augmentation of DNA damage. Transcriptionally active p53 accumulated in cells in which human papillomavirus E6 normally degrades p53. The combination treatment resulted in caspase activation and apoptosis, but this effect did not depend on either p53 or p73 activity. Despite increased p53 activity, the cells arrested in G2 phase became defective in this checkpoint, allowing cell cycle progression. The effect after MX treatment depended partially on c-Abl: Short interfering RNA knockdown of c-Abl rendered HeLa cells less sensitive to MX. The effect of imatinib was decreased by c-Abl siRNA suggesting a role for catalytically inactive c-Abl in the death cascade. These findings indicate that MX has a unique cytotoxic effect when the kinase activity of c-Abl is inhibited. The treatment results in increased DNA damage and c-Abl–dependent apoptosis, which may offer new possibilities for potentiation of cancer chemotherapy. PMID:25148385

  5. Ataxia telangiectasia-mutated kinase deficiency exacerbates left ventricular dysfunction and remodeling late after myocardial infarction.

    Science.gov (United States)

    Daniel, Laura L; Scofield, Stephanie L C; Thrasher, Patsy; Dalal, Suman; Daniels, Christopher R; Foster, Cerrone R; Singh, Mahipal; Singh, Krishna

    2016-08-01

    Ataxia telangiectasia-mutated kinase (ATM), a cell cycle checkpoint protein, is activated in response to DNA damage and oxidative stress. We have previously shown that ATM deficiency is associated with increased apoptosis and fibrosis and attenuation of cardiac dysfunction early (1-7 days) following myocardial infarction (MI). Here, we tested the hypothesis that enhanced fibrosis and apoptosis, as observed early post-MI during ATM deficiency, exacerbate cardiac dysfunction and remodeling in ATM-deficient mice late post-MI. MIs were induced in wild-type (WT) and ATM heterozygous knockout (hKO) mice by ligation of the left anterior descending artery. Left ventricular (LV) structural and functional parameters were assessed by echocardiography 14 and 28 days post-MI, whereas biochemical parameters were measured 28 days post-MI. hKO-MI mice exhibited exacerbated LV dysfunction as observed by increased LV end-systolic volume and decreased percent fractional shortening and ejection fraction. Infarct size and thickness were not different between the two genotypes. Myocyte cross-sectional area was greater in hKO-MI group. The hKO-MI group exhibited increased fibrosis in the noninfarct and higher expression of α-smooth muscle actin (myofibroblast marker) in the infarct region. Apoptosis and activation of GSK-3β (proapoptotic kinase) were significantly lower in the infarct region of hKO-MI group. Matrix metalloproteinase 2 (MMP-2) expression was not different between the two genotypes. However, MMP-9 expression was significantly lower in the noninfarct region of hKO-MI group. Thus ATM deficiency exacerbates cardiac remodeling late post-MI with effects on cardiac function, fibrosis, apoptosis, and myocyte hypertrophy. PMID:27288435

  6. Inhibition of c-Abl kinase activity renders cancer cells highly sensitive to mitoxantrone.

    Directory of Open Access Journals (Sweden)

    Kemal Alpay

    Full Text Available Although c-Abl has increasingly emerged as a key player in the DNA damage response, its role in this context is far from clear. We studied the effect of inhibition of c-Abl kinase activity by imatinib with chemotherapy drugs and found a striking difference in cell survival after combined mitoxantrone (MX and imatinib treatment compared to a panel of other chemotherapy drugs. The combinatory treatment induced apoptosis in HeLa cells and other cancer cell lines but not in primary fibroblasts. The difference in MX and doxorubicin was related to significant augmentation of DNA damage. Transcriptionally active p53 accumulated in cells in which human papillomavirus E6 normally degrades p53. The combination treatment resulted in caspase activation and apoptosis, but this effect did not depend on either p53 or p73 activity. Despite increased p53 activity, the cells arrested in G2 phase became defective in this checkpoint, allowing cell cycle progression. The effect after MX treatment depended partially on c-Abl: Short interfering RNA knockdown of c-Abl rendered HeLa cells less sensitive to MX. The effect of imatinib was decreased by c-Abl siRNA suggesting a role for catalytically inactive c-Abl in the death cascade. These findings indicate that MX has a unique cytotoxic effect when the kinase activity of c-Abl is inhibited. The treatment results in increased DNA damage and c-Abl-dependent apoptosis, which may offer new possibilities for potentiation of cancer chemotherapy.

  7. Seeding Collaborations to Advance Kinase Science with the GSK Published Kinase Inhibitor Set (PKIS)

    OpenAIRE

    Drewry, David H.; Willson, Timothy M.; Zuercher, William J

    2014-01-01

    To catalyze research on historically untargeted protein kinases, we created the PKIS, an annotated set of 367 small molecule kinase inhibitors. The set has been widely distributed to academic collaborators as an open access tool. It has been used to identify chemical starting points for development of chemical probes for orphan kinases and to investigate kinase signaling in high content phenotypic assays. Access to the set comes with few restrictions other than the requirement that assay resu...

  8. Aristolochic acid-induced apoptosis and G2 cell cycle arrest depends on ROS generation and MAP kinases activation.

    Science.gov (United States)

    Romanov, Victor; Whyard, Terry C; Waltzer, Wayne C; Grollman, Arthur P; Rosenquist, Thomas

    2015-01-01

    Ingestion of aristolochic acids (AAs) contained in herbal remedies results in a renal disease and, frequently, urothelial malignancy. The genotoxicity of AA in renal cells, including mutagenic DNA adducts formation, is well documented. However, the mechanisms of AA-induced tubular atrophy and renal fibrosis are largely unknown. To better elucidate some aspects of this process, we studied cell cycle distribution and cell survival of renal epithelial cells treated with AAI at low and high doses. A low dose of AA induces cell cycle arrest in G2/M phase via activation of DNA damage checkpoint pathway ATM-Chk2-p53-p21. DNA damage signaling pathway is activated more likely via increased production of reactive oxygen species (ROS) caused by AA treatment then via DNA damage induced directly by AA. Higher AA concentration induced cell death partly via apoptosis. Since mitogen-activated protein kinases play an important role in cell survival, death and cell cycle progression, we assayed their function in AA-treated renal tubular epithelial cells. ERK1/2 and p38 but not JNK were activated in cells treated with AA. In addition, pharmacological inhibition of ERK1/2 and p38 as well as suppression of ROS generation with N-acetyl-L-cysteine resulted in the partial relief of cells from G2/M checkpoint and a decline of apoptosis level. Cell cycle arrest may be a mechanism for DNA repair, cell survival and reprogramming of epithelial cells to the fibroblast type. An apoptosis of renal epithelial cells at higher AA dose might be necessary to provide space for newly reprogrammed fibrotic cells. PMID:24792323

  9. Sensitive kinase assay linked with phosphoproteomics for identifying direct kinase substrates.

    Science.gov (United States)

    Xue, Liang; Wang, Wen-Horng; Iliuk, Anton; Hu, Lianghai; Galan, Jacob A; Yu, Shuai; Hans, Michael; Geahlen, Robert L; Tao, W Andy

    2012-04-10

    Our understanding of the molecular control of many disease pathologies requires the identification of direct substrates targeted by specific protein kinases. Here we describe an integrated proteomic strategy, termed kinase assay linked with phosphoproteomics, which combines a sensitive kinase reaction with endogenous kinase-dependent phosphoproteomics to identify direct substrates of protein kinases. The unique in vitro kinase reaction is carried out in a highly efficient manner using a pool of peptides derived directly from cellular kinase substrates and then dephosphorylated as substrate candidates. The resulting newly phosphorylated peptides are then isolated and identified by mass spectrometry. A further comparison of these in vitro phosphorylated peptides with phosphopeptides derived from endogenous proteins isolated from cells in which the kinase is either active or inhibited reveals new candidate protein substrates. The kinase assay linked with phosphoproteomics strategy was applied to identify unique substrates of spleen tyrosine kinase (Syk), a protein-tyrosine kinase with duel properties of an oncogene and a tumor suppressor in distinctive cell types. We identified 64 and 23 direct substrates of Syk specific to B cells and breast cancer cells, respectively. Both known and unique substrates, including multiple centrosomal substrates for Syk, were identified, supporting a unique mechanism that Syk negatively affects cell division through its centrosomal kinase activity. PMID:22451900

  10. Celecoxib Enhances the Radiosensitizing Effect of 7-Hydroxystaurosporine (UCN-01) in Human Lung Cancer Cell Lines

    International Nuclear Information System (INIS)

    Purpose: 7-Hydroxystaurosporine (UCN-01), a Chk1-specific inhibitor, showed promising in vitro and in vivo chemo- or radiosensitizing activity. However, there have been concerns about its limited therapeutic efficacy and risk of side effects. A method of enhancing the treatment efficacy of UCN-01 while not increasing its side effects on normal tissue may therefore be required to apply this drug in clinical settings. Celecoxib is a cyclooxygenase-2 (COX-2)-specific inhibitor that downregulates ataxia telangiectasia and rad3-related (ATR) protein, an upstream kinase of Chk1. In this study, we investigated whether the addition of celecoxib can potentiate the radiosensitizing effect of UCN-01. Methods and Materials: The cooperative radiosensitizing effects and the underlying molecular mechanisms of UCN-01 plus celecoxib were determined by clonogenic assay, tumor growth delay assay, flow cytometry, and Western blotting. Synergism of the three agents combined (UCN-01 plus celecoxib plus radiation) were evaluated using median drug effect analysis and drug-independent action model analysis. Results: The combination of UCN-01 and celecoxib could induce synergistic cytotoxicity and radiosensitizing effects in in vitro and in vivo systems. The combination of both drugs also cooperatively inhibited IR-induced G2/M arrest, and increased the G2 to mitotic transition. Conclusions: Combined treatment with UCN-01 and celecoxib can exert synergistically enhanced radiosensitizing effects via cooperative inhibition of the ionizing radiation-activated G2 checkpoint. We propose that this combination strategy may be useful in clinical applications of UCN-01 for radiotherapy of cancer patients.

  11. Celecoxib Enhances the Radiosensitizing Effect of 7-Hydroxystaurosporine (UCN-01) in Human Lung Cancer Cell Lines

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young-Mee; Jeong, In-Hye [Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Pyo, Hongryull, E-mail: Quasar93@yahoo.co.kr [Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

    2012-07-01

    Purpose: 7-Hydroxystaurosporine (UCN-01), a Chk1-specific inhibitor, showed promising in vitro and in vivo chemo- or radiosensitizing activity. However, there have been concerns about its limited therapeutic efficacy and risk of side effects. A method of enhancing the treatment efficacy of UCN-01 while not increasing its side effects on normal tissue may therefore be required to apply this drug in clinical settings. Celecoxib is a cyclooxygenase-2 (COX-2)-specific inhibitor that downregulates ataxia telangiectasia and rad3-related (ATR) protein, an upstream kinase of Chk1. In this study, we investigated whether the addition of celecoxib can potentiate the radiosensitizing effect of UCN-01. Methods and Materials: The cooperative radiosensitizing effects and the underlying molecular mechanisms of UCN-01 plus celecoxib were determined by clonogenic assay, tumor growth delay assay, flow cytometry, and Western blotting. Synergism of the three agents combined (UCN-01 plus celecoxib plus radiation) were evaluated using median drug effect analysis and drug-independent action model analysis. Results: The combination of UCN-01 and celecoxib could induce synergistic cytotoxicity and radiosensitizing effects in in vitro and in vivo systems. The combination of both drugs also cooperatively inhibited IR-induced G{sub 2}/M arrest, and increased the G{sub 2} to mitotic transition. Conclusions: Combined treatment with UCN-01 and celecoxib can exert synergistically enhanced radiosensitizing effects via cooperative inhibition of the ionizing radiation-activated G{sub 2} checkpoint. We propose that this combination strategy may be useful in clinical applications of UCN-01 for radiotherapy of cancer patients.

  12. Comparison of Peptide Array Substrate Phosphorylation of c-Raf and Mitogen Activated Protein Kinase Kinase Kinase 8

    NARCIS (Netherlands)

    Parikh, Kaushal; Diks, Sander H.; Tuynman, Jurriaan H. B.; Verhaar, Auke; Lowenberg, Mark; Hommes, Daan W.; Joore, Jos; Pandey, Akhilesh; Peppelenbosch, Maikel P.

    2009-01-01

    Kinases are pivotal regulators of cellular physiology. The human genome contains more than 500 putative kinases, which exert their action via the phosphorylation of specific substrates. The determinants of this specificity are still only partly understood and as a consequence it is difficult to pred

  13. Immune Reactivation by Cell-Free Fetal DNA in Healthy Pregnancies Re-Purposed to Target Tumors: Novel Checkpoint Inhibition in Cancer Therapeutics

    OpenAIRE

    Enninga, Elizabeth Ann L.; Nevala, Wendy K.; Holtan, Shernan G.; Svetomir N. Markovic

    2015-01-01

    The role of the immune system in cancer progression has become increasingly evident over the past decade. Chronic inflammation in the promotion of tumorigenesis is well established, and cancer-associated tolerance/immune evasion has long been appreciated. Recent developments of immunotherapies targeting cancer-associated inflammation and immune tolerance, such as cancer vaccines, cell therapies, neutralizing antibodies, and immune checkpoint inhibitors, have shown promising clinical results. ...

  14. A plant cyclin B2 is degraded early in mitosis and its ectopic expression shortens G2-phase and alleviates the DNA-damage checkpoint

    Czech Academy of Sciences Publication Activity Database

    Weingartner, M.; Pelayo, H. R.; Binarová, Pavla; Zwerger, K.; Melikant, B.; Torre, C.; Heberle-Bors, E.; Bogre, L.

    2003-01-01

    Roč. 116, č. 3 (2003), s. 487-498. ISSN 0021-9533 R&D Projects: GA MŠk LN00A081 Grant ostatní: GA Ministerio de Ciencia y Tecnologia (ES) BMC2001-2195; Biotechnology and Biological Science Research Council(AU) 111/P133340 Institutional research plan: CEZ:AV0Z5020903 Keywords : cyclin B * mitosis * checkpoint Subject RIV: EE - Microbiology, Virology Impact factor: 7.250, year: 2003

  15. Immune Checkpoint Blockade in Cancer Treatment: A Double-Edged Sword Cross-Targeting the Host as an “Innocent Bystander”

    Directory of Open Access Journals (Sweden)

    Lucia Gelao

    2014-03-01

    Full Text Available Targeted immune checkpoint blockade augments anti-tumor immunity and induces durable responses in patients with melanoma and other solid tumors. It also induces specific “immune-related adverse events” (irAEs. IrAEs mainly include gastrointestinal, dermatological, hepatic and endocrinological toxicities. Off-target effects that arise appear to account for much of the toxicity of the immune checkpoint blockade. These unique “innocent bystander” effects are likely a direct result of breaking immune tolerance upon immune check point blockade and require specific treatment guidelines that include symptomatic therapies or systemic corticosteroids. What do we need going forward to limit immune checkpoint blockade-induced toxicity? Most importantly, we need a better understanding of the roles played by these agents in normal tissues, so that we can begin to predict potentially problematic side effects on the basis of their selectivity profile. Second, we need to focus on the predictive factors of the response and toxicity of the host rather than serially focusing on individual agents. Third, rigorous biomarker-driven clinical trials are needed to further elucidate the mechanisms of both the benefit and toxicity. We will summarize the double-edged sword effect of immunotherapeutics in cancer treatment.

  16. Loss of yeast peroxiredoxin Tsa1p induces genome instability through activation of the DNA damage checkpoint and elevation of dNTP levels.

    Directory of Open Access Journals (Sweden)

    Hei-Man Vincent Tang

    2009-10-01

    Full Text Available Peroxiredoxins are a family of antioxidant enzymes critically involved in cellular defense and signaling. Particularly, yeast peroxiredoxin Tsa1p is thought to play a role in the maintenance of genome integrity, but the underlying mechanism is not understood. In this study, we took a genetic approach to investigate the cause of genome instability in tsa1Delta cells. Strong genetic interactions of TSA1 with DNA damage checkpoint components DUN1, SML1, and CRT1 were found when mutant cells were analyzed for either sensitivity to DNA damage or rate of spontaneous base substitutions. An elevation in intracellular dNTP production was observed in tsa1Delta cells. This was associated with constitutive activation of the DNA damage checkpoint as indicated by phosphorylation of Rad9/Rad53p, reduced steady-state amount of Sml1p, and induction of RNR and HUG1 genes. In addition, defects in the DNA damage checkpoint did not modulate intracellular level of reactive oxygen species, but suppressed the mutator phenotype of tsa1Delta cells. On the contrary, overexpression of RNR1 exacerbated this phenotype by increasing dNTP levels. Taken together, our findings uncover a new role of TSA1 in preventing the overproduction of dNTPs, which is a root cause of genome instability.

  17. Identification of a mutation causing a defective spindle assembly checkpoint in high ethyl caproate-producing sake yeast strain K1801.

    Science.gov (United States)

    Goshima, Tetsuya; Nakamura, Ryo; Kume, Kazunori; Okada, Hiroki; Ichikawa, Eri; Tamura, Hiroyasu; Hasuda, Hirokazu; Inahashi, Masaaki; Okazaki, Naoto; Akao, Takeshi; Shimoi, Hitoshi; Mizunuma, Masaki; Ohya, Yoshikazu; Hirata, Dai

    2016-08-01

    In high-quality sake brewing, the cerulenin-resistant sake yeast K1801 with high ethyl caproate-producing ability has been used widely; however, K1801 has a defective spindle assembly checkpoint (SAC). To identify the mutation causing this defect, we first searched for sake yeasts with a SAC-defect like K1801 and found that K13 had such a defect. Then, we searched for a common SNP in only K1801 and K13 by examining 15 checkpoint-related genes in 23 sake yeasts, and found 1 mutation, R48P of Cdc55, the PP2A regulatory B subunit that is important for the SAC. Furthermore, we confirmed that the Cdc55-R48P mutation was responsible for the SAC-defect in K1801 by molecular genetic analyses. Morphological analysis indicated that this mutation caused a high cell morphological variation. But this mutation did not affect the excellent brewing properties of K1801. Thus, this mutation is a target for breeding of a new risk-free K1801 with normal checkpoint integrity. PMID:27191586

  18. G{sub 1} arrest and down-regulation of cyclin E/cyclin-dependent kinase 2 by the protein kinase inhibitor staurosporine are dependent on the retinoblastoma protein in the bladder carcinoma cell line 5637

    Energy Technology Data Exchange (ETDEWEB)

    Schnier, J.B.; Nishi, K. [Univ. of California, Davis, CA (United States); Goodrich, D.W. [Univ. of Texas, Houston, TX (United States)] [and others

    1996-06-11

    The protein kinase inhibitor staurosporine has been shown to induce G{sub 1} phase arrest in normal cells but not in most transformed cells. Staurosporine did not induce G{sub 1} phase arrest in the bladder carcinoma cell line 5637 that lacks a functional retinoblastoma protein (pRB{sup {minus}}). However, when infected with a pRB-expressing retrovirus, these cells, now pRB{sup +} and pRB{sup {minus}} cells, cyclin D1-associated kinase activities were reduced on staurosporine treatment. In contrast, cylin-dependent kinase (CDK) 2 and cyclin E/CDK2 activities were inhibited only in pRB{sup +} cells. Staurosporine treatment did not cause reductions in the protein levels of CDK4, cyclin D1, CDK2, or cyclin E. The CDK inhibitor proteins p21{sup (Wafl/Cipl)} and p27{sup (Kipl}) levels increased in staurosporine-treated cells. Immunoprecipitation of CDK2, cyclin E, and p21 form staurosporine-treated pRB{sup +} cells revealed a 2.5- to 3-fold higher ratio of p21 bound to CDK2 compared with staurosporine-treated pRB cells. In pRB{sup +} cells, p21 was preferentially associated with Thr160 phosphorylated active CDK2. In pRB{sup {minus}} cells, however, p21 was bound preferentially to the unphosphorylated, inactive form of CDK2 even though the phosphorylated form was abundant. This is the first evidence suggesting that G{sub 1} arrest by 4 nM staurosporine is dependent on a functional pRB protein. Cell cycle arrest at the pRB-dependent checkpoint may prevent activation of cyclin E/CDK2 by stabilizing its interaction with inhibitor proteins p21 and p27. 47 refs.

  19. Genetics Home Reference: pyruvate kinase deficiency

    Science.gov (United States)

    ... National (UK) Information Centre for Metabolic Diseases National Organization for Rare Disorders (NORD): Pyruvate Kinase Deficiency Genetic Testing Registry (1 link) Pyruvate kinase deficiency of red cells Scientific articles on PubMed (1 link) PubMed OMIM (1 link) ...

  20. A multisubstrate deoxyribonucleoside kinase from plants

    DEFF Research Database (Denmark)

    Clausen, Anders R.; Girandon, Lenart; Knecht, Wolfgang;

    2008-01-01

    Deoxyribonucleoside kinases catalyze the rate limiting step during the salvage of deoxyribonucleosides and convert them into the corresponding monophosphate compounds. We have identified and characterized a unique multisubstrate deoxyribonucleoside kinase from plants. The phylogenetic relationship...... suicide gene in anti-cancer therapy....

  1. Tyrosine kinase of insulin-like growth factor receptor as target for novel treatment and prevention strategies of colorectal cancer

    Institute of Scientific and Technical Information of China (English)

    Michael H(o)pfner; Andreas P Sutter; Alexander Huether; Viola Baradari; Hans Scherübl

    2006-01-01

    AIM: To investigate the antineoplastic potency of the novel insulin-like growth factor 1 receptor (IGF-1R) tyrosine kinase inhibitor (TKI) NVP-AEW541 in cell lines and primary cell cultures of human colorectal cancer (CRC).METHODS: Cells of primary colorectal carcinomas were from 8 patients. Immunostaining and crystal violet staining were used for analysis of growth factor receptor protein expression and detection of cell number changes,respectively. Cytotoxicity was determined by measuring the release of the cytoplasmic enzyme lactate dehydrogenase (LDH). The proportion of apoptotic cells was determined by quantifying the percentage of sub-G1(hypodiploid) cells. Cell cycle status reflected by the DNA content of the nuclei was detected by flow cytometry.RESULTS: NVP-AEW541 dose-dependently inhibited the proliferation of colorectal carcinoma cell lines and primary cell cultures by inducing apoptosis and cell cycle arrest. Apoptosis was characterized by caspase-3 activation and nuclear degradation. Cell cycle was arrested at the G1/S checkpoint. The NVP-AEW541-mediated cell cycle-related signaling involved the inactivation of Akt and extracellular signal-regulated kinase (ERK) 1/2, the upregulation of the cyclin-dependent kinase inhibitors p21Waf1/CIP1 and p27Kip1, and the downregulation of the cell cycle promoter cyclin D1. Moreover, BAX was upregulated during NVP-AEW541-induced apoptosis, whereas Bcl-2 was downregulated. Measurement of LDH release showed that the antineoplastic effect of NVP-AEW541 was not due to general cytotoxicity of the compound.However, augmented antineoplastic effects were observed in combination treatments of NVP-AEW541 with either 5-FU, or the EGFR-antibody cetuximab, or the HMG-CoA-reductase inhibitor fluvastatin.CONCLUSION: IGF-1R-TK inhibition is a promising novel approach for either mono- or combination treatment strategies of colorectal carcinoma and even for CRC chemoprevention.

  2. The energy sensor AMPK regulates Hedgehog signaling in human cells through a unique Gli1 metabolic checkpoint

    Science.gov (United States)

    Di Magno, Laura; Basile, Alessio; Coni, Sonia; Manni, Simona; Sdruscia, Giulia; D'Amico, Davide; Antonucci, Laura; Infante, Paola; De Smaele, Enrico; Cucchi, Danilo; Ferretti, Elisabetta; Di Marcotullio, Lucia; Screpanti, Isabella; Canettieri, Gianluca

    2016-01-01

    Hedgehog signaling controls proliferation of cerebellar granule cell precursors (GCPs) and its aberrant activation is a leading cause of Medulloblastoma, the most frequent pediatric brain tumor. We show here that the energy sensor AMPK inhibits Hh signaling by phosphorylating a single residue of human Gli1 that is not conserved in other species. Studies with selective agonists and genetic deletion have revealed that AMPK activation inhibits canonical Hh signaling in human, but not in mouse cells. Indeed we show that AMPK phosphorylates Gli1 at the unique residue Ser408, which is conserved only in primates but not in other species. Once phosphorylated, Gli1 is targeted for proteasomal degradation. Notably, we show that selective AMPK activation inhibits Gli1-driven proliferation and that this effect is linked to Ser408 phosphorylation, which represents a key metabolic checkpoint for Hh signaling. Collectively, this data unveil a novel mechanism of inhibition of Gli1 function, which is exclusive for human cells and may be exploited for the treatment of Medulloblastoma or other Gli1 driven tumors. PMID:26843621

  3. Differential contribution of three immune checkpoint (VISTA, CTLA-4, PD-1) pathways to antitumor responses against squamous cell carcinoma.

    Science.gov (United States)

    Kondo, Yuta; Ohno, Tatsukuni; Nishii, Naoto; Harada, Kiyoshi; Yagita, Hideo; Azuma, Miyuki

    2016-06-01

    V domain-containing Ig suppressor of T-cell activation (VISTA)/PD-1H is a novel immune checkpoint molecule for regulating T-cell activation. We examined the effects of anti-VISTA mAb monotherapy and combination therapy with CTLA-4 or PD-1 blockade in a squamous cell carcinoma (SCCVII) model. VISTA monotherapy did not show clear tumor growth regression, but efficiently induced CD8(+) T cell activation by converting resting and exhausted cells into functional effector cells. VISTA monotherapy did not inhibit recruitment of regulatory T cells (Tregs) in the tumor microenvironment (TME). As an additional treatment to VISTA, CTLA-4 blockade, but not PD-1 blockade, elicited further tumor regression. The CTLA-4 and VISTA combination efficiently inhibited Treg recruitment and increased the ratios of both CD8 T/Treg and CD4 conventional T (Tcon)/Treg in the TME, whereas the PD-1 and VISTA combination dramatically increased tumor-recruiting CD8(+) T cells, but markedly reduced the Tcon/Treg ratio. Our results demonstrate that VISTA blockade efficiently converts CD8(+) T cells into functional effector T cells, but is not sufficient to regress tumor growth due to weak Treg suppression in the TME. Our results suggest that combined CTLA-4 and VISTA blockade is more efficacious than combined PD-1 and VISTA blockade for tumors like head and neck squamous cell carcinoma in which Treg-mediated immune regulation is dominant. PMID:27208845

  4. Human Zwint-1 Specifies Localization of Zeste White 10 to Kinetochores and Is Essential for Mitotic Checkpoint Signaling

    Institute of Scientific and Technical Information of China (English)

    HongmeiWang; XiaoyuHu; XiaDing; ZhenDou; ZhihongYank; AndrewW.Shaw; MaikunTcng; DonW.Cleveland; MichaelL.Goldberg; LiwenNiu; XucbiaoYao

    2005-01-01

    Chromosome segregation in mitosis is orchestrated by dynamic interaction between spindle microtubules and the kinetochore, a multiprotein complex assembled onto centromeric DNA of the chromosome. Here we show that Zwint-1 is required and is sufficient for kinetochore localization of Zestc White 10 (ZW10) in HeLa cells. Zwint-1 specifies the kinetochore association of ZW10 by interacting with its N-terminal domain. Suppression of synthesis of Zwint-1 by small interfering RNA abolishes the localization of ZW10 to the kinetochore, demonstrating the requirement of Zwint-1 for ZWl0 kinetochore localization. In addition, dcplction of Zwint-1 affects no mitotic arrest but causes aberrant premature chromo. some segregation. These Zwint-l-suppressed cells dis. play chromosome bridge phenotype with sister chromatids inter-connected. Moreover, Zwint-1 is required for stable association of CENP.F and dynamitin but not BUB1 with the kinetochore. Finally, our studies showthat Zwint-1 is a new component of the mitotic check. point, as cells lacking Zwint-1 fail to arrest in mitosis when exposed to microtubule inhibitors, yielding inter. phase cells with multinuclei. As ZWl0 and Zwint.1 are absent from yeast, we reasoned that metazoans evolved an elaborate spindle checkpoint machinery to ensure faithful chromosome segregation in mitosis.

  5. Taxifolin enhances andrographolide-induced mitotic arrest and apoptosis in human prostate cancer cells via spindle assembly checkpoint activation.

    Directory of Open Access Journals (Sweden)

    Zhong Rong Zhang

    Full Text Available Andrographolide (Andro suppresses proliferation and triggers apoptosis in many types of cancer cells. Taxifolin (Taxi has been proposed to prevent cancer development similar to other dietary flavonoids. In the present study, the cytotoxic and apoptotic effects of the addition of Andro alone and Andro and Taxi together on human prostate carcinoma DU145 cells were assessed. Andro inhibited prostate cancer cell proliferation by mitotic arrest and activation of the intrinsic apoptotic pathway. Although the effect of Taxi alone on DU145 cell proliferation was not significant, the combined use of Taxi with Andro significantly potentiated the anti-proliferative effect of increased mitotic arrest and apoptosis by enhancing the cleavage of poly(ADP-ribose polymerase, and caspases-7 and -9. Andro together with Taxi enhanced microtubule polymerization in vitro, and they induced the formation of twisted and elongated spindles in the cancer cells, thus leading to mitotic arrest. In addition, we showed that depletion of MAD2, a component in the spindle assembly checkpoint (SAC, alleviated the mitotic block induced by the two compounds, suggesting that they trigger mitotic arrest by SAC activation. This study suggests that the anti-cancer activity of Andro can be significantly enhanced in combination with Taxi by disrupting microtubule dynamics and activating the SAC.

  6. Protein kinases associated with the yeast phosphoproteome

    Directory of Open Access Journals (Sweden)

    Munn Alan L

    2006-01-01

    Full Text Available Abstract Background Protein phosphorylation is an extremely important mechanism of cellular regulation. A large-scale study of phosphoproteins in a whole-cell lysate of Saccharomyces cerevisiae has previously identified 383 phosphorylation sites in 216 peptide sequences. However, the protein kinases responsible for the phosphorylation of the identified proteins have not previously been assigned. Results We used Predikin in combination with other bioinformatic tools, to predict which of 116 unique protein kinases in yeast phosphorylates each experimentally determined site in the phosphoproteome. The prediction was based on the match between the phosphorylated 7-residue sequence and the predicted substrate specificity of each kinase, with the highest weight applied to the residues or positions that contribute most to the substrate specificity. We estimated the reliability of the predictions by performing a parallel prediction on phosphopeptides for which the kinase has been experimentally determined. Conclusion The results reveal that the functions of the protein kinases and their predicted phosphoprotein substrates are often correlated, for example in endocytosis, cytokinesis, transcription, replication, carbohydrate metabolism and stress response. The predictions link phosphoproteins of unknown function with protein kinases with known functions and vice versa, suggesting functions for the uncharacterized proteins. The study indicates that the phosphoproteins and the associated protein kinases represented in our dataset have housekeeping cellular roles; certain kinases are not represented because they may only be activated during specific cellular responses. Our results demonstrate the utility of our previously reported protein kinase substrate prediction approach (Predikin as a tool for establishing links between kinases and phosphoproteins that can subsequently be tested experimentally.

  7. Differential phosphorylation of ribosomal acidic proteins from yeast cell by two endogenous protein kinases: casein kinase-2 and 60S kinase

    International Nuclear Information System (INIS)

    The native 80S ribosomes isolated from ''Saccharomyces cerevisiae'' (strain W303) cells was phosphorylated by two endogenous protein kinases: multifunctional casein kinase-2 (CK-2) and specific 60S kinase. Three acidic proteins within the 60S ribosomal subunit: YP1β, YP1β' and YP2α are phosphorylated by both kinases. The other two proteins: YP1α and YP2β are predominantly phosphorylated by CK-2 but not by 60S kinase. This was confirmed in the experiment with the recombinant protein, YP2β, as a substrate, which is practically not phosphorylated by specific 60S kinase. These results together with the previous data based on the target amino-acid sequences suggest that, in addition to the multifunctional casein kinase-2 and specific 60S kinase, there exist probably other protein kinase(s) which phosphorylate the ribosomal acidic proteins in the cell. (author). 23 refs, 3 figs, 1 tab

  8. Crystal Structure of Pyridoxal Kinase from the Escherichia coli pdxK Gene: Implications for the Classification of Pyridoxal Kinases

    OpenAIRE

    Safo, Martin K.; Musayev, Faik N.; di Salvo, Martino L.; Hunt, Sharyn; Claude, Jean-Baptiste; Schirch, Verne

    2006-01-01

    The pdxK and pdxY genes have been found to code for pyridoxal kinases, enzymes involved in the pyridoxal phosphate salvage pathway. Two pyridoxal kinase structures have recently been published, including Escherichia coli pyridoxal kinase 2 (ePL kinase 2) and sheep pyridoxal kinase, products of the pdxY and pdxK genes, respectively. We now report the crystal structure of E. coli pyridoxal kinase 1 (ePL kinase 1), encoded by a pdxK gene, and an isoform of ePL kinase 2. The structures were deter...

  9. Physiological roles of mitogen-activated-protein-kinase-activated p38-regulated/activated protein kinase

    Institute of Scientific and Technical Information of China (English)

    Sergiy; Kostenko; Gianina; Dumitriu; Kari; Jenssen; Lgreid; Ugo; Moens

    2011-01-01

    Mitogen-activated protein kinases(MAPKs)are a family of proteins that constitute signaling pathways involved in processes that control gene expression,cell division, cell survival,apoptosis,metabolism,differentiation and motility.The MAPK pathways can be divided into conventional and atypical MAPK pathways.The first group converts a signal into a cellular response through a relay of three consecutive phosphorylation events exerted by MAPK kinase kinases,MAPK kinase,and MAPK.Atypical MAPK pathways are not organized into this three-tiered cascade.MAPK that belongs to both conventional and atypical MAPK pathways can phosphorylate both non-protein kinase substrates and other protein kinases.The latter are referred to as MAPK-activated protein kinases.This review focuses on one such MAPK-activated protein kinase,MAPK-activated protein kinase 5(MK5)or p38-regulated/activated protein kinase(PRAK).This protein is highly conserved throughout the animal kingdom and seems to be the target of both conventional and atypical MAPK pathways.Recent findings on the regulation of the activity and subcellular localization,bona fide interaction partners and physiological roles of MK5/PRAK are discussed.

  10. Mitogen-activated protein kinases in atherosclerosis

    Directory of Open Access Journals (Sweden)

    Dorota Bryk

    2014-01-01

    Full Text Available Intracellular signalling cascades, in which MAPK (mitogen-activated protein kinases intermediate, are responsible for a biological response of a cell to an external stimulus. MAP kinases, which include ERK1/2 (extracellular signalling-regulated kinase, JNK (c-Jun N-terminal kinase and p 38 MAPK, regulate the activity of many proteins, enzymes and transcription factors and thus have a wide spectrum of biological effects. Many basic scientific studies have defined numerous details of their pathway organization and activation. There are also more and more studies suggesting that individual MAP kinases probably play an important role in the pathogenesis of atherosclerosis. They may mediate inflammatory processes, endothelial cell activation, monocyte/macrophage recruitment and activation, smooth muscle cell proliferation and T-lymphocyte differentiation, all of which represent crucial mechanisms involved in pathogenesis of atherosclerosis. The specific inhibition of an activity of the respective MAP kinases may prove a new therapeutic approach to attenuate atherosclerotic plaque formation in the future. In this paper, we review the current state of knowledge concerning MAP kinase-dependent cellular and molecular mechanisms underlying atherosclerosis.

  11. [Mitogen-activated protein kinases in atherosclerosis].

    Science.gov (United States)

    Bryk, Dorota; Olejarz, Wioletta; Zapolska-Downar, Danuta

    2014-01-01

    Intracellular signalling cascades, in which MAPK (mitogen-activated protein kinases) intermediate, are responsible for a biological response of a cell to an external stimulus. MAP kinases, which include ERK1/2 (extracellular signalling-regulated kinase), JNK (c-Jun N-terminal kinase) and p 38 MAPK, regulate the activity of many proteins, enzymes and transcription factors and thus have a wide spectrum of biological effects. Many basic scientific studies have defined numerous details of their pathway organization and activation. There are also more and more studies suggesting that individual MAP kinases probably play an important role in the pathogenesis of atherosclerosis. They may mediate inflammatory processes, endothelial cell activation, monocyte/macrophage recruitment and activation, smooth muscle cell proliferation and T-lymphocyte differentiation, all of which represent crucial mechanisms involved in pathogenesis of atherosclerosis. The specific inhibition of an activity of the respective MAP kinases may prove a new therapeutic approach to attenuate atherosclerotic plaque formation in the future. In this paper, we review the current state of knowledge concerning MAP kinase-dependent cellular and molecular mechanisms underlying atherosclerosis. PMID:24491891

  12. Mitotic regulation by NIMA-related kinases

    Directory of Open Access Journals (Sweden)

    Blot Joelle

    2007-08-01

    Full Text Available Abstract The NIMA-related kinases represent a family of serine/threonine kinases implicated in cell cycle control. The founding member of this family, the NIMA kinase of Aspergillus nidulans, as well as the fission yeast homologue Fin1, contribute to multiple aspects of mitotic progression including the timing of mitotic entry, chromatin condensation, spindle organization and cytokinesis. Mammals contain a large family of eleven NIMA-related kinases, named Nek1 to Nek11. Of these, there is now substantial evidence that Nek2, Nek6, Nek7 and Nek9 also regulate mitotic events. At least three of these kinases, as well as NIMA and Fin1, have been localized to the microtubule organizing centre of their respective species, namely the centrosome or spindle pole body. Here, they have important functions in microtubule organization and mitotic spindle assembly. Other Nek kinases have been proposed to play microtubule-dependent roles in non-dividing cells, most notably in regulating the axonemal microtubules of cilia and flagella. In this review, we discuss the evidence that NIMA-related kinases make a significant contribution to the orchestration of mitotic progression and thereby protect cells from chromosome instability. Furthermore, we highlight their potential as novel chemotherapeutic targets.

  13. The mechanism of protein kinase C regulation

    Institute of Scientific and Technical Information of China (English)

    Julhash U. KAZI

    2011-01-01

    Protein kinase C (PKC) is a family ofserine/threonine protein kinases that plays a central role in transducing extracellular signals into a variety of intracellular responses ranging from cell proliferation to apoptosis.Nine PKC genes have been identified in the human genome,which encode 10 proteins.Each member of this protein kinase family displays distinct biochemical characteristics and is enriched in different cellular and subcellular locations.Activation of PKC has been implicated in the regulation of cell growth and differentiation.This review summarizes works of the past years in the field of PKC biochemistry that covers regulation and activation mechanism of different PKC isoforms.

  14. Differential AMP-activated Protein Kinase (AMPK) Recognition Mechanism of Ca2+/Calmodulin-dependent Protein Kinase Kinase Isoforms.

    Science.gov (United States)

    Fujiwara, Yuya; Kawaguchi, Yoshinori; Fujimoto, Tomohito; Kanayama, Naoki; Magari, Masaki; Tokumitsu, Hiroshi

    2016-06-24

    Ca(2+)/calmodulin-dependent protein kinase kinase β (CaMKKβ) is a known activating kinase for AMP-activated protein kinase (AMPK). In vitro, CaMKKβ phosphorylates Thr(172) in the AMPKα subunit more efficiently than CaMKKα, with a lower Km (∼2 μm) for AMPK, whereas the CaMKIα phosphorylation efficiencies by both CaMKKs are indistinguishable. Here we found that subdomain VIII of CaMKK is involved in the discrimination of AMPK as a native substrate by measuring the activities of various CaMKKα/CaMKKβ chimera mutants. Site-directed mutagenesis analysis revealed that Leu(358) in CaMKKβ/Ile(322) in CaMKKα confer, at least in part, a distinct recognition of AMPK but not of CaMKIα. PMID:27151216

  15. Rac-1 and Raf-1 kinases, components of distinct signaling pathways, activate myotonic dystrophy protein kinase

    Science.gov (United States)

    Shimizu, M.; Wang, W.; Walch, E. T.; Dunne, P. W.; Epstein, H. F.

    2000-01-01

    Myotonic dystrophy protein kinase (DMPK) is a serine-threonine protein kinase encoded by the myotonic dystrophy (DM) locus on human chromosome 19q13.3. It is a close relative of other kinases that interact with members of the Rho family of small GTPases. We show here that the actin cytoskeleton-linked GTPase Rac-1 binds to DMPK, and coexpression of Rac-1 and DMPK activates its transphosphorylation activity in a GTP-sensitive manner. DMPK can also bind Raf-1 kinase, the Ras-activated molecule of the MAP kinase pathway. Purified Raf-1 kinase phosphorylates and activates DMPK. The interaction of DMPK with these distinct signals suggests that it may play a role as a nexus for cross-talk between their respective pathways and may partially explain the remarkable pleiotropy of DM.

  16. Human CAR T cells with cell-intrinsic PD-1 checkpoint blockade resist tumor-mediated inhibition.

    Science.gov (United States)

    Cherkassky, Leonid; Morello, Aurore; Villena-Vargas, Jonathan; Feng, Yang; Dimitrov, Dimiter S; Jones, David R; Sadelain, Michel; Adusumilli, Prasad S

    2016-08-01

    Following immune attack, solid tumors upregulate coinhibitory ligands that bind to inhibitory receptors on T cells. This adaptive resistance compromises the efficacy of chimeric antigen receptor (CAR) T cell therapies, which redirect T cells to solid tumors. Here, we investigated whether programmed death-1-mediated (PD-1-mediated) T cell exhaustion affects mesothelin-targeted CAR T cells and explored cell-intrinsic strategies to overcome inhibition of CAR T cells. Using an orthotopic mouse model of pleural mesothelioma, we determined that relatively high doses of both CD28- and 4-1BB-based second-generation CAR T cells achieved tumor eradication. CAR-mediated CD28 and 4-1BB costimulation resulted in similar levels of T cell persistence in animals treated with low T cell doses; however, PD-1 upregulation within the tumor microenvironment inhibited T cell function. At lower doses, 4-1BB CAR T cells retained their cytotoxic and cytokine secretion functions longer than CD28 CAR T cells. The prolonged function of 4-1BB CAR T cells correlated with improved survival. PD-1/PD-1 ligand [PD-L1] pathway interference, through PD-1 antibody checkpoint blockade, cell-intrinsic PD-1 shRNA blockade, or a PD-1 dominant negative receptor, restored the effector function of CD28 CAR T cells. These findings provide mechanistic insights into human CAR T cell exhaustion in solid tumors and suggest that PD-1/PD-L1 blockade may be an effective strategy for improving the potency of CAR T cell therapies. PMID:27454297

  17. Exposure to methyl tert-butyl ether, benzene, and total hydrocarbons at the Singapore-Malaysia causeway immigration checkpoint

    Energy Technology Data Exchange (ETDEWEB)

    Tan, C.; Ong, H.Y.; Kok, P.W. [and others

    1996-12-31

    The primary aim of this study was to determine the extent and levels of exposure to volatile organic compounds (VOCs) from automobile emissions in a group of immigration officers at a busy cross-border checkpoint. A majority (80%) of the workers monitored were exposed to benzene at levels between 0.01 and 0.5 ppm, with only 1.2% exceeding the current Occupational Safety and Health Administration occupational exposure limit of 1 ppm. The geometric mean (GM) concentrations of 8-hr time-weighted average exposure were 0.03 ppm, 0.9 ppm, and 2.46 ppm for methyl-tert-butyl ether (MTBE), benzene, and total hydrocarbons (THC), respectively. The highest time-weighted average concentrations measured were 1.05 ppm for MTBE, 2.01 ppm for benzene, and 34 ppm for THC. It was found that motorbikes emitted a more significant amount of pollutants compared with motor cars. On average, officers at the motorcycle booths were exposed to four to five times higher levels of VOCs (GMs of 0.07 ppm, 0.23 ppm, and 4.7 ppm for MTBE, benzene, and THC) than their counterparts at the motor car booths (GMs of 0.01 ppm, 0.05 ppm, and 1.5 ppm). The airborne concentrations of all three pollutants correlated with the flow of vehicle traffic. Close correlations were also noted for the concentrations in ambient air for the three pollutants measured. Benzene and MTBE had a correlation coefficient of 0.97. The overall findings showed that the concentrations of various VOCs were closely related to the traffic density, suggesting that they were from a common source, such as exhaust emissions from the vehicles. The results also indicated that although benzene, MTBE, and THC are known to be volatile, a significant amount could still be detected in the ambient environment, thus contributing to our exposure to these compounds. 4 refs., 6 figs.

  18. DNA-damage response network at the crossroads of cell-cycle checkpoints, cellular senescence and apoptosis*

    OpenAIRE

    Schmitt, Estelle; Paquet, Claudie; Beauchemin, Myriam; Bertrand, Richard

    2007-01-01

    Tissue homeostasis requires a carefully-orchestrated balance between cell proliferation, cellular senescence and cell death. Cells proliferate through a cell cycle that is tightly regulated by cyclin-dependent kinase activities. Cellular senescence is a safeguard program limiting the proliferative competence of cells in living organisms. Apoptosis eliminates unwanted cells by the coordinated activity of gene products that regulate and effect cell death. The intimate link between the cell cycl...

  19. Pantothenate kinase-associated neurodegeneration.

    Science.gov (United States)

    Hartig, Monika B; Prokisch, Holger; Meitinger, Thomas; Klopstock, Thomas

    2012-08-01

    Pantothenate kinase-associated neurodegeneration (PKAN) is a hereditary progressive disorder and the most frequent form of neurodegeneration with brain iron accumulation (NBIA). PKAN patients present with a progressive movement disorder, dysarthria, cognitive impairment and retinitis pigmentosa. In magnetic resonance imaging, PKAN patients exhibit the pathognonomic "eye of the tiger" sign in the globus pallidus which corresponds to iron accumulation and gliosis as shown in neuropathological examinations. The discovery of the disease causing mutations in PANK2 has linked the disorder to coenzyme A (CoA) metabolism. PANK2 is the only one out of four PANK genes encoding an isoform which localizes to mitochondria. At least two other NBIA genes (PLA2G6, C19orf12) encode proteins that share with PANK2 a mitochondrial localization and all are suggested to play a role in lipid homeostasis. With no causal therapy available for PKAN until now, only symptomatic treatment is possible. A multi-centre retrospective study with bilateral pallidal deep brain stimulation in patients with NBIA revealed a significant improvement of dystonia. Recently, studies in the PANK Drosophila model "fumble" revealed improvement by the compound pantethine which is hypothesized to feed an alternate CoA biosynthesis pathway. In addition, pilot studies with the iron chelator deferiprone that crosses the blood brain barrier showed a good safety profile and some indication of efficacy. An adequately powered randomized clinical trial will start in 2012. This review summarizes clinical presentation, neuropathology and pathogenesis of PKAN. PMID:22515741

  20. Protein Kinase A in Cancer

    Directory of Open Access Journals (Sweden)

    Antonio Caretta

    2011-02-01

    Full Text Available In the past, many chromosomal and genetic alterations have been examined as possible causes of cancer. However, some tumors do not display a clear molecular and/or genetic signature. Therefore, other cellular processes may be involved in carcinogenesis. Genetic alterations of proteins involved in signal transduction have been extensively studied, for example oncogenes, while modifications in intracellular compartmentalization of these molecules, or changes in the expression of unmodified genes have received less attention. Yet, epigenetic modulation of second messenger systems can deeply modify cellular functioning and in the end may cause instability of many processes, including cell mitosis. It is important to understand the functional meaning of modifications in second messenger intracellular pathways and unravel the role of downstream proteins in the initiation and growth of tumors. Within this framework, the cAMP system has been examined. cAMP is a second messenger involved in regulation of a variety of cellular functions. It acts mainly through its binding to cAMP-activated protein kinases (PKA, that were suggested to participate in the onset and progression of various tumors. PKA may represent a biomarker for tumor detection, identification and staging, and may be a potential target for pharmacological treatment of tumors.

  1. Protein Kinase A in Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Caretta, Antonio; Mucignat-Caretta, Carla, E-mail: carla.mucignat@unipd.it [Department of Human Anatomy and Physiology, University of Padova, Via Marzolo 3, 35131 Padova (Italy)

    2011-02-28

    In the past, many chromosomal and genetic alterations have been examined as possible causes of cancer. However, some tumors do not display a clear molecular and/or genetic signature. Therefore, other cellular processes may be involved in carcinogenesis. Genetic alterations of proteins involved in signal transduction have been extensively studied, for example oncogenes, while modifications in intracellular compartmentalization of these molecules, or changes in the expression of unmodified genes have received less attention. Yet, epigenetic modulation of second messenger systems can deeply modify cellular functioning and in the end may cause instability of many processes, including cell mitosis. It is important to understand the functional meaning of modifications in second messenger intracellular pathways and unravel the role of downstream proteins in the initiation and growth of tumors. Within this framework, the cAMP system has been examined. cAMP is a second messenger involved in regulation of a variety of cellular functions. It acts mainly through its binding to cAMP-activated protein kinases (PKA), that were suggested to participate in the onset and progression of various tumors. PKA may represent a biomarker for tumor detection, identification and staging, and may be a potential target for pharmacological treatment of tumors.

  2. Genetics Home Reference: phosphoglycerate kinase deficiency

    Science.gov (United States)

    ... Children Living with Inherited Metabolic Diseases (CLIMB) (UK) Muscular Dystrophy Association National Organization for Rare Disorders (NORD) Resource list from the University of Kansas Medical Center: Metabolic Conditions Genetic Testing Registry (2 links) Deficiency of phosphoglycerate kinase ...

  3. Genetics Home Reference: mevalonate kinase deficiency

    Science.gov (United States)

    ... net Patient Support and Advocacy Resources (2 links) Autoinflammatory Alliance National Organization for Rare Disorders (NORD): Hyper ... Haas D, Hoffmann GF. Mevalonate kinase deficiency and autoinflammatory disorders. N Engl J Med. 2007 Jun 28; ...

  4. Genetics Home Reference: deoxyguanosine kinase deficiency

    Science.gov (United States)

    ... or mtDNA, which is essential for the normal function of these structures. Deoxyguanosine kinase is involved in producing and maintaining the ... DNA (known as mitochondrial DNA depletion) impairs mitochondrial function ... deficiency . Learn more about the gene associated ...

  5. Kinase inhibitors for advanced medullary thyroid carcinoma

    Directory of Open Access Journals (Sweden)

    Martin Schlumberger

    2012-01-01

    Full Text Available The recent availability of molecular targeted therapies leads to a reconsideration of the treatment strategy for patients with distant metastases from medullary thyroid carcinoma. In patients with progressive disease, treatment with kinase inhibitors should be offered.

  6. Kinome profiling of Arabidopsis using arrays of kinase consensus substrates

    NARCIS (Netherlands)

    Ritsema, T.; Joore, J.; Workum, W. van; Pieterse, C.M.J.

    2007-01-01

    Background: Kinome profiling aims at the parallel analysis of kinase activities in a cell. Novel developed arrays containing consensus substrates for kinases are used to assess those kinase activities. The arrays described in this paper were already used to determine kinase activities in mammalian s

  7. The Ca2+/Calmodulin-Dependent Protein Kinase Kinase, CaMKK2, Inhibits Preadipocyte Differentiation

    OpenAIRE

    Lin, Fumin; Ribar, Thomas J.; Means, Anthony R.

    2011-01-01

    When fed a standard chow diet, CaMKK2 null mice have increased adiposity and larger adipocytes than do wild-type mice, whereas energy balance is unchanged. Here, we show that Ca2+/calmodulin-dependent protein kinase kinase 2 (CaMKK2) is expressed in preadipocytes, where it functions as an AMP-activated protein kinase (AMPK)α kinase. Acute inhibition or deletion of CaMKK2 in preadipocytes enhances their differentiation into mature adipocytes, which can be reversed by 5-aminoimidazole-4-carboxa...

  8. Protein kinase domain of twitchin has protein kinase activity and an autoinhibitory region.

    Science.gov (United States)

    Lei, J; Tang, X; Chambers, T C; Pohl, J; Benian, G M

    1994-08-19

    Twitchin is a 753-kDa polypeptide located in the muscle A-bands of the nematode, Caenorhabditis elegans. It consists of multiple copies of both fibronectin III and immunoglobulin C2 domains and, near the C terminus, a protein kinase domain with greatest homology to the catalytic domains of myosin light chain kinases. We have expressed and purified from Escherichia coli twitchin's protein kinase catalytic core and flanking sequences that do not include fibronectin III and immunoglobulin C2 domains. The protein was shown to phosphorylate a model substrate and to undergo autophosphorylation. The autophosphorylation occurs at a slow rate, attaining a maximum at 3 h with a stoichiometry of about 1.0 mol of phosphate/mol of protein, probably through an intramolecular mechanism. Sequence analysis of proteolytically derived phosphopeptides revealed that autophosphorylation occurred N-terminal to the catalytic core, predominantly at Thr-5910, with possible minor sites at Ser5912 and/or Ser-5913. This portion of twitchin (residues 5890-6268) was also phosphorylated in vitro by protein kinase C in the absence of calcium and phosphotidylserine, but not by cAMP-dependent protein kinase. By comparing the activities of three twitchin segments, the enzyme appears to be inhibited by the 60-amino acid residues lying just C-terminal to the kinase catalytic core. Thus, like a number of other protein kinases including myosin light chain kinases, the twitchin kinase appears to be autoregulated. PMID:8063727

  9. Seeding collaborations to advance kinase science with the GSK Published Kinase Inhibitor Set (PKIS).

    Science.gov (United States)

    Drewry, David H; Willson, Timothy M; Zuercher, William J

    2014-01-01

    To catalyze research on historically untargeted protein kinases, we created the PKIS, an annotated set of 367 small molecule kinase inhibitors. The set has been widely distributed to academic collaborators as an open access tool. It has been used to identify chemical starting points for development of chemical probes for orphan kinases and to investigate kinase signaling in high content phenotypic assays. Access to the set comes with few restrictions other than the requirement that assay results be released into the public domain for the benefit of the entire research community. Examples from the efforts of several collaborators are summarized. PMID:24283969

  10. Janus kinases in immune cell signaling

    OpenAIRE

    Ghoreschi, Kamran; Laurence, Arian; O’Shea, John J.

    2009-01-01

    The Janus family kinases (Jaks), Jak1, Jak2, Jak3, and Tyk2, form one subgroup of the non-receptor protein tyrosine kinases. They are involved in cell growth, survival, development, and differentiation of a variety of cells but are critically important for immune cells and hematopoietic cells. Data from experimental mice and clinical observations have unraveled multiple signaling events mediated by Jak in innate and adaptive immunity. Deficiency of Jak3 or Tyk2 results in defined clinical dis...

  11. Non-degradative Ubiquitination of Protein Kinases.

    OpenAIRE

    K Aurelia Ball; Johnson, Jeffrey R.; Lewinski, Mary K; John Guatelli; Erik Verschueren; Krogan, Nevan J.; Matthew P Jacobson

    2016-01-01

    Growing evidence supports other regulatory roles for protein ubiquitination in addition to serving as a tag for proteasomal degradation. In contrast to other common post-translational modifications, such as phosphorylation, little is known about how non-degradative ubiquitination modulates protein structure, dynamics, and function. Due to the wealth of knowledge concerning protein kinase structure and regulation, we examined kinase ubiquitination using ubiquitin remnant immunoaffinity enrichm...

  12. K-Ras-Independent Effects of the Farnesyl Transferase Inhibitor L-744,832 on Cyclin B1/Cdc2 Kinase Activity, G2/M Cell Cycle Progression and Apoptosis in Human Pancreatic Ductal Adenocarcinoma Cell

    Directory of Open Access Journals (Sweden)

    Si Young Song

    2000-05-01

    Full Text Available Pancreatic ductal adenocarcinoma is a highly lethal malignancy that is resistant to traditional cytotoxic therapy. High rates of activating codon 12 K-Ras mutations in this disease have generated considerable interest in the therapeutic application of novel farnesyl transferase inhibitors (FTIs. However, a comprehensive analysis of the effects of FTI treatment on pancreatic cancer cells has not been performed. Treatment of five different human pancreatic cancer cell lines with FTI L744,832 resulted in inhibition of anchorage-dependent growth, with wide variation in sensitivity among different lines. Effective growth inhibition by L-744,832 correlated with accumulation of cells with a tetraploid (4N DNA content and high levels of cyclin B1/cdc2 kinase activity, implying cell cycle arrest downstream from the DNA damage -inducible G2/M cell cycle checkpoint. In addition, sensitive cell lines underwent apoptosis as evidenced by changes in nuclear morphology and internucleosomal DNA fragmentation. L-744,832 at a concentration of 1 µM additively enhanced the cytotoxic effect of ionizing radiation, apparently by overriding G2/M checkpoint activation. The effects of FTI treatment on cell growth and cell cycle regulation were associated with changes in posttranslational processing of H-Ras and N-Ras, but not K-Ras. The results confirm the potential therapeutic efficacy of FTI treatment in pancreatic cancer, and suggest that farnesylated proteins other than K-Ras may act as important regulators of G2/M cell cycle kinetics.

  13. Evolutionary Reconstruction and Population Genetics Analysis of Aurora Kinases

    OpenAIRE

    Balu Kamaraj; Ambuj Kumar; Rituraj Purohit

    2013-01-01

    BACKGROUND: Aurora kinases belong to the highly conserved kinase family and play a vital role in cell cycle regulation. The structure and function of these kinases are inter-related and sometimes they also act as substitutes in case of knockdown of other aurora kinases. METHOD: In this work we carried out the evolutionary reconstruction and population genetic studies of aurora kinase proteins. Substitution saturation test, CAI (Codon adaptation index), gene expression and RSCU (Relative synon...

  14. miR-424(322) reverses chemoresistance via T-cell immune response activation by blocking the PD-L1 immune checkpoint

    OpenAIRE

    Xu, Shaohua; Tao, Zhen; Hai, Bo; Liang, Huagen; SHI, YING; Tao WANG; Song, Wen; Chen, Yong; Ouyang, Jun; Chen, Jinhong; Kong, Fanfei; Dong, Yishan; Jiang, Shi-Wen; LI, WEIYONG; Ping WANG

    2016-01-01

    Immune checkpoint blockade of the inhibitory immune receptors PD-L1, PD-1 and CTLA-4 has emerged as a successful treatment strategy for several advanced cancers. Here we demonstrate that miR-424(322) regulates the PD-L1/PD-1 and CD80/CTLA-4 pathways in chemoresistant ovarian cancer. miR-424(322) is inversely correlated with PD-L1, PD-1, CD80 and CTLA-4 expression. High levels of miR-424(322) in the tumours are positively correlated with the progression-free survival of ovarian cancer patients...

  15. Hypomorphic bimA(APC3) alleles cause errors in chromosome metabolism that activate the DNA damage checkpoint blocking cytokinesis in Aspergillus nidulans.

    OpenAIRE

    Wolkow, T D; Mirabito, P.M.; Venkatram, S; Hamer, J. E.

    2000-01-01

    The Aspergillus nidulans sepI(+) gene has been implicated in the coordination of septation with nuclear division and cell growth. We find that the temperature-sensitive (ts) sepI1 mutation represents a novel allele of bimA(APC3), which encodes a conserved component of the anaphase-promoting complex/cyclosome (APC/C). We have characterized the septation, nuclear division, cell-cycle checkpoint defects, and DNA sequence alterations of sepI1 (renamed bimA10) and two other ts lethal bimA(APC3) al...

  16. Non-degradative Ubiquitination of Protein Kinases.

    Directory of Open Access Journals (Sweden)

    K Aurelia Ball

    2016-06-01

    Full Text Available Growing evidence supports other regulatory roles for protein ubiquitination in addition to serving as a tag for proteasomal degradation. In contrast to other common post-translational modifications, such as phosphorylation, little is known about how non-degradative ubiquitination modulates protein structure, dynamics, and function. Due to the wealth of knowledge concerning protein kinase structure and regulation, we examined kinase ubiquitination using ubiquitin remnant immunoaffinity enrichment and quantitative mass spectrometry to identify ubiquitinated kinases and the sites of ubiquitination in Jurkat and HEK293 cells. We find that, unlike phosphorylation, ubiquitination most commonly occurs in structured domains, and on the kinase domain, ubiquitination is concentrated in regions known to be important for regulating activity. We hypothesized that ubiquitination, like other post-translational modifications, may alter the conformational equilibrium of the modified protein. We chose one human kinase, ZAP-70, to simulate using molecular dynamics with and without a monoubiquitin modification. In Jurkat cells, ZAP-70 is ubiquitinated at several sites that are not sensitive to proteasome inhibition and thus may have other regulatory roles. Our simulations show that ubiquitination influences the conformational ensemble of ZAP-70 in a site-dependent manner. When monoubiquitinated at K377, near the C-helix, the active conformation of the ZAP-70 C-helix is disrupted. In contrast, when monoubiquitinated at K476, near the kinase hinge region, an active-like ZAP-70 C-helix conformation is stabilized. These results lead to testable hypotheses that ubiquitination directly modulates kinase activity, and that ubiquitination is likely to alter structure, dynamics, and function in other protein classes as well.

  17. Phospho-kinase profile of colorectal tumors guides in the selection of multi-kinase inhibitors.

    Science.gov (United States)

    Serrano-Heras, Gemma; Cuenca-López, María Dolores; Montero, Juan Carlos; Corrales-Sanchez, Verónica; Morales, Jorge Carlos; Núñez, Luz-Elena; Morís, Francisco; Pandiella, Atanasio; Ocaña, Alberto

    2015-10-13

    Protein kinases play a central role in the oncogenesis of colorectal tumors and are attractive druggable targets. Detection of activated kinases within a tumor could open avenues for drug selection and optimization of new kinase inhibitors. By using a phosphokinase arrays with human colorectal tumors we identified activated kinases, including the Epidermal Growth Factor Receptor (EGFR), components of the PI3K/mTOR pathway (AKT and S6), and STAT, among others. A pharmacological screening with kinase inhibitors against these proteins helped us to identify a new kinase inhibitor, termed EC-70124 that showed the highest anti-proliferative activity in cell lines. EC-70124 also inhibited cell migration and biochemical experiments demonstrated its effect targeting the PI3K/mTOR pathway. This drug also arrested cells at G2/M and induced apoptosis. Experiments in combination with standard chemotherapy used in the clinical setting indicated a synergistic effect. EC-70124 also reduced tumor growth in vivo and inhibited pS6 in the implanted tumors. In conclusion, by studying the kinase profile of colorectal tumors, we identified relevant activated pathways, and a new multi-kinase compound with significant antitumor properties. PMID:26418718

  18. CDPKs are dual-specificity protein kinases and tyrosine autophosphorylation attenuates kinase activity

    Science.gov (United States)

    Calcium-dependent protein kinases (CDPKs or CPKs) are classified as serine/threonine protein kinases but we made the surprising observation that soybean CDPK' and several Arabidopsis isoforms (AtCPK4 and AtCPK34) could also autophosphorylate on tyrosine residues. In studies with His6-GmCDPK', we ide...

  19. KinasePA: Phosphoproteomics data annotation using hypothesis driven kinase perturbation analysis.

    Science.gov (United States)

    Yang, Pengyi; Patrick, Ellis; Humphrey, Sean J; Ghazanfar, Shila; James, David E; Jothi, Raja; Yang, Jean Yee Hwa

    2016-07-01

    Mass spectrometry (MS)-based quantitative phosphoproteomics has become a key approach for proteome-wide profiling of phosphorylation in tissues and cells. Traditional experimental design often compares a single treatment with a control, whereas increasingly more experiments are designed to compare multiple treatments with respect to a control. To this end, the development of bioinformatic tools that can integrate multiple treatments and visualise kinases and substrates under combinatorial perturbations is vital for dissecting concordant and/or independent effects of each treatment. Here, we propose a hypothesis driven kinase perturbation analysis (KinasePA) to annotate and visualise kinases and their substrates that are perturbed by various combinatorial effects of treatments in phosphoproteomics experiments. We demonstrate the utility of KinasePA through its application to two large-scale phosphoproteomics datasets and show its effectiveness in dissecting kinases and substrates within signalling pathways driven by unique combinations of cellular stimuli and inhibitors. We implemented and incorporated KinasePA as part of the "directPA" R package available from the comprehensive R archive network (CRAN). Furthermore, KinasePA also has an interactive web interface that can be readily applied to annotate user provided phosphoproteomics data (http://kinasepa.pengyiyang.org). PMID:27145998

  20. Enhanced Expression of Bruton's Tyrosine Kinase in B Cells Drives Systemic Autoimmunity by Disrupting T Cell Homeostasis.

    Science.gov (United States)

    Corneth, Odilia B J; de Bruijn, Marjolein J W; Rip, Jasper; Asmawidjaja, Patrick S; Kil, Laurens P; Hendriks, Rudi W

    2016-07-01

    Upon BCR stimulation, naive B cells increase protein levels of the key downstream signaling molecule Bruton's tyrosine kinase (BTK). Transgenic CD19-hBtk mice with B cell-specific BTK overexpression show spontaneous germinal center formation, anti-nuclear autoantibodies, and systemic autoimmunity resembling lupus and Sjögren syndrome. However, it remains unknown how T cells are engaged in this pathology. In this study, we found that CD19-hBtk B cells were high in IL-6 and IL-10 and disrupted T cell homeostasis in vivo. CD19-hBtk B cells promoted IFN-γ production by T cells and expression of the immune-checkpoint protein ICOS on T cells and induced follicular Th cell differentiation. Crosses with CD40L-deficient mice revealed that increased IL-6 production and autoimmune pathology in CD19-hBtk mice was dependent on B-T cell interaction, whereas IL-10 production and IgM autoantibody formation were CD40L independent. Surprisingly, in Btk-overexpressing mice, naive B cells manifested increased CD86 expression, which was dependent on CD40L, suggesting that T cells interact with B cells in a very early stage of immune pathology. These findings indicate that increased BTK-mediated signaling in B cells involves a positive-feedback loop that establishes T cell-propagated autoimmune pathology, making BTK an attractive therapeutic target in autoimmune disease. PMID:27226091

  1. Expression and prognostic value of the WEE1 kinase in gliomas.

    Science.gov (United States)

    Music, Darija; Dahlrot, Rikke Hedegaard; Hermansen, Simon Kjær; Hjelmborg, Jacob; de Stricker, Karin; Hansen, Steinbjørn; Kristensen, Bjarne Winther

    2016-04-01

    High-grade gliomas have an aggressive clinical course and new clinical biomarkers and therapeutic targets are highly needed. WEE1 is a regulator of the G2 checkpoint in glioblastoma (GBM) cells. Inhibition of this kinase has, in experimental glioma studies, been suggested to enhance sensitivity to irradiation and temozolomide. However, expression level and prognostic potential of WEE1 protein in gliomas remain uninvestigated. In this study, glioma samples from 235 patients across all four WHO grades were analyzed by immunohistochemistry. Using image analysis, we calculated the area fraction of WEE1 positive nuclei. We found that WEE1 protein was localized in tumor cell nuclei and expressed in all glioma types and grades. Although WEE1 protein levels are higher in GBMs (mean 24.5%) relative to grade III (mean 14,0%, p < 0.05) and grade II (mean 6.8%, p < 0.001) gliomas, high WEE1 protein was associated with better survival in GBMs (p = 0.002). This was confirmed in multivariate analysis (HR 0.60, p = 0.003) even when adjusted for MGMT status (HR 0.60, p = 0.005). In conclusion, we report a nuclear expression of WEE1 protein in all glioma grades and types. The WEE1 positive nuclear area was correlated with malignancy grade but it was inversely associated with prognosis in GBM. Although WEE1 is a frequently occurring protein and has been proposed as a novel target in GBM, the role of WEE1 in glioma patient survival appears to be connected to the MGMT status and is more complex than previously anticipated. PMID:26738845

  2. Janus kinase inhibitors: jackpot or potluck?

    Directory of Open Access Journals (Sweden)

    Pavithran Keechilat

    2012-06-01

    Full Text Available The reports of a unique mutation in the Janus kinase-2 gene (JAK2 in polycythemia vera by several independent groups in 2005 quickly spurred the development of the Janus kinase inhibitors. In one of the great victories of translational research in recent times, the first smallmolecule Janus kinase inhibitor ruxolitinib entered a phase I trial in 2007. With the approval of ruxolitinib by the US Federal Drug Administration in November 2011 for high-risk and intermediate-2 risk myelofibrosis, a change in paradigm has occurred in the management of a subset of myeloproliferative neoplasms (MPN: primary myelofibrosis, post-polycythemia vera myelofibrosis, and post-essential thrombocythemia myelofibrosis. Whereas the current evidence for ruxolitinib only covers high-risk and intermediate-2 risk myelofibrosis, inhibitors with greater potency are likely to offer better disease control and survival advantage in patients belonging to these categories, and possibly to the low-risk and intermediate-1 risk categories of MPN as well. But use of the Janus kinase inhibitors also probably has certain disadvantages, such as toxicity, resistance, withdrawal phenomenon, non-reversal of histology, and an implausible goal of disease clone eradication, some of which could offset the gains. In spite of this, Janus kinase inhibitors are here to stay, and for use in more than just myeloproliferative neoplasms.

  3. Mechanism of polyphosphate kinase from Propionibacterium shermanii

    International Nuclear Information System (INIS)

    Polyphosphate kinase, which catalyzes the reaction shown below, is one of two enzymes which have been reported to catalyze the synthesis of polyphosphate. Purification performed by ammonium sulfate precipitation (0-40% fraction) was followed by chromatography. The enzyme represents 70% of the protein in the hydroxylapatite pool and is stable at this level of purity. The subunit molecular weight was determined by SDS polyacrylamide gel analysis, (83,000 +/- 3000), nondenaturing polyacrylamide gel electrophoresis, (80,000 and 86,000 daltons), gel filtration (Biogel A 0.5m column was 85,000 +/- 4000.) Polyphosphate kinase appears to be a monomeric enzyme of ∼83,000 daltons. Four assays were developed for polyphosphate kinase. Basic proteins such as polylysine stimulate the synthesis of polyphosphate, these proteins cause precipitation of polyphosphate kinase from relatively impure enzyme extracts: Synthesized polyphosphate interacts noncovalently with the basic protein-enzyme precipitate. Efficient synthesis of polyphosphate requires the addition of either phosphate or short chain polyphosphate. Synthesis did occur at 1/10 the rate when neither of these two compounds were included. Initiation, elongation, and termination events of polyphosphate synthesis were examined. Short chain polyphosphate acts as a primer, with [32P] short-chain polyphosphate incorporation into long chain polyphosphate by the kinase

  4. Novel role for cyclin-dependent kinase 2 in neuregulin-induced acetylcholine receptor epsilon subunit expression in differentiated myotubes.

    Science.gov (United States)

    Lu, Gang; Seta, Karen A; Millhorn, David E

    2005-06-10

    Cyclin-dependent kinases (CDKs) are a family of evolutionarily conserved serine/threonine kinases. CDK2 acts as a checkpoint for the G(1)/S transition in the cell cycle. Despite a down-regulation of CDK2 activity in postmitotic cells, many cell types, including muscle cells, maintain abundant levels of CDK2 protein. This led us to hypothesize that CDK2 may have a function in postmitotic cells. We show here for the first time that CDK2 can be activated by neuregulin (NRG) in differentiated C2C12 myotubes. In addition, this activity is required for expression of the acetylcholine receptor (AChR) epsilon subunit. The switch from the fetal AChRgamma subunit to the adult-type AChRepsilon is required for synapse maturation and the neuromuscular junction. Inhibition of CDK2 activity with either the specific CDK2 inhibitory peptide Tat-LFG or by RNA interference abolished neuregulin-induced AChRepsilon expression. Neuregulin-induced activation of CDK2 also depended on the ErbB receptor, MAPK, and PI3K, all of which have previously been shown to be required for AChRepsilon expression. Neuregulin regulated CDK2 activity through coordinating phosphorylation of CDK2 on Thr-160, accumulation of CDK2 in the nucleus, and down-regulation of the CDK2 inhibitory protein p27 in the nucleus. In addition, we also observed a novel mechanism of regulation of CDK2 activity by a low molecular weight variant of cyclin E in response to NRG. These findings establish CDK2 as an intermediate molecule that integrates NRG-activated signals from both the MAPK and PI3K pathways to AChRepsilon expression and reveal an undiscovered physiological role for CDK2 in postmitotic cells. PMID:15824106

  5. Discovery of 4-(4-aminopyrazolo[1,5-a][1,3,5]triazin-8-yl)benzamides as novel, highly potent and selective, orally bioavailable inhibitors of Tyrosine Threonine Kinase, TTK.

    Science.gov (United States)

    Laufer, Radoslaw; Li, Sze-Wan; Liu, Yong; Ng, Grace; Lang, Yunhui; Feher, Miklos; Brokx, Richard; Beletskaya, Irina; Hodgson, Richard; Mao, Guodong; Plotnikova, Olga; Awrey, Donald E; Mason, Jacqueline M; Wei, Xin; Lin, Dan Chi-Chia; Che, Yi; Kiarash, Reza; Madeira, Brian; Fletcher, Graham C; Mak, Tak W; Bray, Mark R; Pauls, Henry W

    2016-08-01

    TTK/Mps1 is a key kinase controlling progression of cell division via participation in the mitotic spindle assembly checkpoint and is overexpressed in a number of human cancers. Herein we report the discovery of 4-(4-aminopyrazolo[1,5-a][1,3,5]triazin-8-yl)benzamides as a potent, novel class of TTK inhibitors. The series was identified by means of bioisosteric replacement of the related imidazopyrazine and imidazopyridazine scaffolds. Optimization led to the identification of compounds with excellent potency (Ki=0.8nM) and exceptional kinase selectivity. The SAR indicates a strong dependence of activity on the presence of the N-cyclopropyl-2-methylbenzamide moiety delineating the geometry for 1½ type kinase inhibitor. Molecular modeling indicates the extensive and optimal contacts, mediated through H-bonds and hydrophobic interactions, are responsible for the selectivity and potency of the inhibitors. The compounds demonstrate a strong anti-proliferative activity in a panel of human cancer cell lines (HCT116 GI50<15nM) and good rodent pharmacokinetics (oral %F 97%). PMID:27335255

  6. miR-424(322) reverses chemoresistance via T-cell immune response activation by blocking the PD-L1 immune checkpoint

    Science.gov (United States)

    Xu, Shaohua; Tao, Zhen; Hai, Bo; Liang, Huagen; Shi, Ying; Wang, Tao; Song, Wen; Chen, Yong; OuYang, Jun; Chen, Jinhong; Kong, Fanfei; Dong, Yishan; Jiang, Shi-Wen; Li, Weiyong; Wang, Ping; Yuan, Zhiyong; Wan, Xiaoping; Wang, Chenguang; Li, Wencheng; Zhang, Xiaoping; Chen, Ke

    2016-01-01

    Immune checkpoint blockade of the inhibitory immune receptors PD-L1, PD-1 and CTLA-4 has emerged as a successful treatment strategy for several advanced cancers. Here we demonstrate that miR-424(322) regulates the PD-L1/PD-1 and CD80/CTLA-4 pathways in chemoresistant ovarian cancer. miR-424(322) is inversely correlated with PD-L1, PD-1, CD80 and CTLA-4 expression. High levels of miR-424(322) in the tumours are positively correlated with the progression-free survival of ovarian cancer patients. Mechanistic investigations demonstrated that miR-424(322) inhibited PD-L1 and CD80 expression through direct binding to the 3′-untranslated region. Restoration of miR-424(322) expression reverses chemoresistance, which is accompanied by blockage of the PD-L1 immune checkpoint. The synergistic effect of chemotherapy and immunotherapy is associated with the proliferation of functional cytotoxic CD8+ T cells and the inhibition of myeloid-derived suppressive cells and regulatory T cells. Collectively, our data suggest a biological and functional interaction between PD-L1 and chemoresistance through the microRNA regulatory cascade. PMID:27147225

  7. Kaposi sarcoma herpes virus latency associated nuclear antigen protein release the G2/M cell cycle blocks by modulating ATM/ATR mediated checkpoint pathway.

    Directory of Open Access Journals (Sweden)

    Amit Kumar

    Full Text Available The Kaposi's sarcoma-associated herpesvirus infects the human population and maintains latency stage of viral life cycle in a variety of cell types including cells of epithelial, mesenchymal and endothelial origin. The establishment of latent infection by KSHV requires the expression of an unique repertoire of genes among which latency associated nuclear antigen (LANA plays a critical role in the replication of the viral genome. LANA regulates the transcription of a number of viral and cellular genes essential for the survival of the virus in the host cell. The present study demonstrates the disruption of the host G2/M cell cycle checkpoint regulation as an associated function of LANA. DNA profile of LANA expressing human B-cells demonstrated the ability of this nuclear antigen in relieving the drug (Nocodazole induced G2/M checkpoint arrest. Caffeine suppressed nocodazole induced G2/M arrest indicating involvement of the ATM/ATR. Notably, we have also shown the direct interaction of LANA with Chk2, the ATM/ATR signalling effector and is responsible for the release of the G2/M cell cycle block.

  8. miR-424(322) reverses chemoresistance via T-cell immune response activation by blocking the PD-L1 immune checkpoint.

    Science.gov (United States)

    Xu, Shaohua; Tao, Zhen; Hai, Bo; Liang, Huagen; Shi, Ying; Wang, Tao; Song, Wen; Chen, Yong; OuYang, Jun; Chen, Jinhong; Kong, Fanfei; Dong, Yishan; Jiang, Shi-Wen; Li, Weiyong; Wang, Ping; Yuan, Zhiyong; Wan, Xiaoping; Wang, Chenguang; Li, Wencheng; Zhang, Xiaoping; Chen, Ke

    2016-01-01

    Immune checkpoint blockade of the inhibitory immune receptors PD-L1, PD-1 and CTLA-4 has emerged as a successful treatment strategy for several advanced cancers. Here we demonstrate that miR-424(322) regulates the PD-L1/PD-1 and CD80/CTLA-4 pathways in chemoresistant ovarian cancer. miR-424(322) is inversely correlated with PD-L1, PD-1, CD80 and CTLA-4 expression. High levels of miR-424(322) in the tumours are positively correlated with the progression-free survival of ovarian cancer patients. Mechanistic investigations demonstrated that miR-424(322) inhibited PD-L1 and CD80 expression through direct binding to the 3'-untranslated region. Restoration of miR-424(322) expression reverses chemoresistance, which is accompanied by blockage of the PD-L1 immune checkpoint. The synergistic effect of chemotherapy and immunotherapy is associated with the proliferation of functional cytotoxic CD8+ T cells and the inhibition of myeloid-derived suppressive cells and regulatory T cells. Collectively, our data suggest a biological and functional interaction between PD-L1 and chemoresistance through the microRNA regulatory cascade. PMID:27147225

  9. Functional dissection of Caenorhabditis elegans CLK-2/TEL2 cell cycle defects during embryogenesis and germline development.

    Directory of Open Access Journals (Sweden)

    Sandra C Moser

    2009-04-01

    Full Text Available CLK-2/TEL2 is essential for viability from yeasts to vertebrates, but its essential functions remain ill defined. CLK-2/TEL2 was initially implicated in telomere length regulation in budding yeast, but work in Caenorhabditis elegans has uncovered a function in DNA damage response signalling. Subsequently, DNA damage signalling defects associated with CLK-2/TEL2 have been confirmed in yeast and human cells. The CLK-2/TEL2 interaction with the ATM and ATR DNA damage sensor kinases and its requirement for their stability led to the proposal that CLK-2/TEL2 mutants might phenocopy ATM and/or ATR depletion. We use C. elegans to dissect developmental and cell cycle related roles of CLK-2. Temperature sensitive (ts clk-2 mutants accumulate genomic instability and show a delay of embryonic cell cycle timing. This delay partially depends on the worm p53 homolog CEP-1 and is rescued by co-depletion of the DNA replication checkpoint proteins ATL-1 (C. elegans ATR and CHK-1. In addition, clk-2 ts mutants show a spindle orientation defect in the eight cell stages that lead to major cell fate transitions. clk-2 deletion worms progress through embryogenesis and larval development by maternal rescue but become sterile and halt germ cell cycle progression. Unlike ATL-1 depleted germ cells, clk-2-null germ cells do not accumulate DNA double-strand breaks. Rather, clk-2 mutant germ cells arrest with duplicated centrosomes but without mitotic spindles in an early prophase like stage. This germ cell cycle arrest does not depend on cep-1, the DNA replication, or the spindle checkpoint. Our analysis shows that CLK-2 depletion does not phenocopy PIKK kinase depletion. Rather, we implicate CLK-2 in multiple developmental and cell cycle related processes and show that CLK-2 and ATR have antagonising functions during early C. elegans embryonic development.

  10. Phosphatidylinositol 3-Kinase (PI3K) and phosphatidylinositol 3-kinase-related kinase (PIKK) inhibitors: importance of the morpholine ring

    Czech Academy of Sciences Publication Activity Database

    Andrs, M.; Kobarecny, J.; Jun, D.; Hodný, Zdeněk; Bartek, Jiří; Kuca, K.

    2015-01-01

    Roč. 58, č. 1 (2015), s. 41-71. ISSN 0022-2623 R&D Projects: GA MŠk(CZ) CZ.1.07/2.3.00/30.0044 Grant ostatní: University Hospital Hradec Kralove(CZ) 00179906; Faculty of Military Health Sciences, University of Defence(CZ) SV/FVZ201402 Institutional support: RVO:68378050 Keywords : DEPENDENT PROTEIN-KINASE * STRAND BREAK REPAIR * SELECTIVE PI3K-BETA INHIBITORS * TELANGIECTASIA MUTATED KINASE Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.447, year: 2014

  11. The Role of PAS Kinase in PASsing the Glucose Signal

    Directory of Open Access Journals (Sweden)

    Julianne H. Grose

    2010-06-01

    Full Text Available PAS kinase is an evolutionarily conserved nutrient responsive protein kinase that regulates glucose homeostasis. Mammalian PAS kinase is activated by glucose in pancreatic beta cells, and knockout mice are protected from obesity, liver triglyceride accumulation, and insulin resistance when fed a high-fat diet. Yeast PAS kinase is regulated by both carbon source and cell integrity stress and stimulates the partitioning of glucose toward structural carbohydrate biosynthesis. In our current model for PAS kinase regulation, a small molecule metabolite binds the sensory PAS domain and activates the enzyme. Although bona fide PAS kinase substrates are scarce, in vitro substrate searches provide putative targets for exploration.

  12. Interleukin 3-dependent survival by the Akt protein kinase

    OpenAIRE

    Songyang, Zhou; Baltimore, David; Cantley, Lewis C.; Kaplan, David R; Franke, Thomas F.

    1997-01-01

    Interleukin 3 (IL-3)-dependent survival of hematopoietic cells is known to rely on the activity of multiple signaling pathways, including a pathway leading to activation of phosphoinositide 3-kinase (PI 3-kinase), and protein kinase Akt is a direct target of PI 3-kinase. We find that Akt kinase activity is rapidly induced by the cytokine IL-3, suggesting a role for Akt in PI 3-kinase-dependent signaling in hematopoetic cells. Dominant-negative mutants of Akt specifically block Akt activation ...

  13. X-Ray Crystal Structure of Bone Marrow Kinase in the X Chromosome: A Tec Family Kinase

    Energy Technology Data Exchange (ETDEWEB)

    Muckelbauer, Jodi; Sack, John S.; Ahmed, Nazia; Burke, James; Chang, ChiehYing Y.; Gao, Mian; Tino, Joseph; Xie, Dianlin; Tebben, Andrew J. (BMS)

    2012-06-27

    Bone marrow kinase in the X chromosome, a member of the Tec family of tyrosine kinases, plays a role in both monocyte/macrophage trafficking as well as cytokine secretion. Although the structures of Tec family kinases Bruton's tyrosine kinase and IL-2-inducible T-cell kinase are known, the crystal structures of other Tec family kinases have remained elusive. We report the X-ray crystal structures of bone marrow kinase in the X chromosome in complex with dasatinib at 2.4 {angstrom} resolution and PP2 at 1.9 {angstrom} resolution. The bone marrow kinase in the X chromosome structures reveal a typical kinase protein fold; with well-ordered protein conformation that includes an open/extended activation loop and a stabilized DFG-motif rendering the kinase in an inactive conformation. Dasatinib and PP2 bind to bone marrow kinase in the X chromosome in the ATP binding pocket and display similar binding modes to that observed in other Tec and Src protein kinases. The bone marrow kinase in the X chromosome structures identify conformational elements of the DFG-motif that could potentially be utilized to design potent and/or selective bone marrow kinase in the X chromosome inhibitors.

  14. Phosphorylation of varicella-zoster virus glycoprotein gpI by mammalian casein kinase II and casein kinase I

    International Nuclear Information System (INIS)

    Varicella-zoster virus (VZV) glycoprotein gpI is the predominant viral glycoprotein within the plasma membranes of infected cells. This viral glycoprotein is phosphorylated on its polypeptide backbone during biosynthesis. In this report, the authors investigated the protein kinases which participate in the phosphorylation events. Under in vivo conditions, VZV gpI was phosphorylated on its serine and threonine residues by protein kinases present within lysates of either VZV-infected or uninfected cells. Because this activity was diminished by heparin, a known inhibitor of casein kinase II, isolated gpI was incubated with purified casein kinase II and shown to be phosphorylated in an in vitro assay containing [γ-32P]ATP. The same glycoprotein was phosphorylated when [32P]GTP was substituted for [32P]ATP in the protein kinase assay. They also tested whether VZV gpI was phosphorylated by two other ubiquitous mammalian protein kinases--casein kinase I and cyclic AMP-dependent kinase--and found that only casein kinase I modified gpI. When the predicted 623-amino-acid sequence of gpI was examined, two phosphorylation sites known to be optimal for casein kinase II were observed. In summary, this study showed that VZV gpI was phosphorylated by each of two mammalian protein kinases (casein kinase I and casein kinase II) and that potential serine-threonine phosphorylation sites for each of these two kinases were present in the viral glycoprotein

  15. AcEST: BP918938 [AcEST

    Lifescience Database Archive (English)

    Full Text Available AGYRNGYNLNLLTRIYERASLV 78 >tr|Q28EK6|Q28EK6_XENTR CHK1 checkpoint homolog (S. pombe) OS=Xenopus trop... sp|Q06J40|PSAB_BIGNA Photosystem I P700 chlorophyll a apoprotein A2 OS=Bigelowiella natans Align length 48 ...ments: (bits) Value sp|Q06J40|PSAB_BIGNA Photosystem I P700 chlorophyll a apoprotein... 31 3.4 sp|Q5XHY8|CF1...|PSAB_BIGNA Photosystem I P700 chlorophyll a apoprotein A2 OS=Bigelowiella natans GN=psaB PE=3 SV=1 Length =...e uncharacterized protein (Fragmen... 59 8e-17 tr|B6A8G9|B6A8G9_HELAM CHK1 checkpoint-like protein (Fragment

  16. Rational design of protein kinase inhibitors

    Directory of Open Access Journals (Sweden)

    Yarmoluk S. M.

    2013-07-01

    Full Text Available Modern methodological approaches to rational design of low molecular weight compounds with specific activity in relation to predetermined biomolecular targets are considered by example of development of high effective protein kinase inhibitors. The application of new computational methods that allow to significantly improve the quality of computational experiments (in, particular, accuracy of low molecular weight compounds activity prediction without increase of computational and time costs are highlighted. The effectiveness of strategy of rational design is demonstrated by examples of several own investigations devoted to development of new inhibitors that are high effective and selective towards protein kinases CK2, FGFR1 and ASK1.

  17. Purification and characterization of a casein kinase 2-type protein kinase from pea nuclei

    Science.gov (United States)

    Li, H.; Roux, S. J.

    1992-01-01

    Almost all the polyamine-stimulated protein kinase activity associated with the chromatin fraction of nuclei purified from etiolated pea (Pisum sativum L.) plumules is present in a single enzyme that can be extracted from chromatin by 0.35 molar NaCl. This protein kinase can be further purified over 2000-fold by salt fractionation and anion-exchange and casein-agarose column chromatography, after which it is more than 90% pure. The purified kinase has a specific activity of about 650 nanomoles per minute per milligram protein in the absence of polyamines, with either ATP or GTP as phosphoryl donor. Spermidine can stimulate its activity fourfold, with half-maximal activation at about 2 millimolar. Spermine and putrescine also stimulate activity, although somewhat less effectively. This kinase has a tetrameric alpha 2 beta 2 structure with a native molecular weight of 130,000, and subunit molecular weights of 36,000 for the catalytic subunit (alpha) and 29,000 for the regulatory subunit (beta). In western blot analyses, only the alpha subunit reacts strongly with polyclonal antibodies to a Drosophila casein kinase II. The pea kinase can use casein and phosvitin as artificial substrates, phosphorylating both the serine and threonine residues of casein. It has a pH optimum near 8.0, a Vmax of 1.5 micromoles per minute per milligram protein, and a Km for ATP of approximately 75 micromolar. Its activity can be almost completely inhibited by heparin at 5 micrograms per milliliter, but is relatively insensitive to concentrations of staurosporine, K252a, and chlorpromazine that strongly antagonize Ca(2+) -regulated protein kinases. These results are discussed in relation to recent findings that casein kinase 2-type kinases may phosphorylate trans-acting factors that bind to light-regulated promoters in plants.

  18. Structural Evolution of the Protein Kinase-Like Superfamily.

    Directory of Open Access Journals (Sweden)

    2005-10-01

    Full Text Available The protein kinase family is large and important, but it is only one family in a larger superfamily of homologous kinases that phosphorylate a variety of substrates and play important roles in all three superkingdoms of life. We used a carefully constructed structural alignment of selected kinases as the basis for a study of the structural evolution of the protein kinase-like superfamily. The comparison of structures revealed a "universal core" domain consisting only of regions required for ATP binding and the phosphotransfer reaction. Remarkably, even within the universal core some kinase structures display notable changes, while still retaining essential activity. Hence, the protein kinase-like superfamily has undergone substantial structural and sequence revision over long evolutionary timescales. We constructed a phylogenetic tree for the superfamily using a novel approach that allowed for the combination of sequence and structure information into a unified quantitative analysis. When considered against the backdrop of species distribution and other metrics, our tree provides a compelling scenario for the development of the various kinase families from a shared common ancestor. We propose that most of the so-called "atypical kinases" are not intermittently derived from protein kinases, but rather diverged early in evolution to form a distinct phyletic group. Within the atypical kinases, the aminoglycoside and choline kinase families appear to share the closest relationship. These two families in turn appear to be the most closely related to the protein kinase family. In addition, our analysis suggests that the actin-fragmin kinase, an atypical protein kinase, is more closely related to the phosphoinositide-3 kinase family than to the protein kinase family. The two most divergent families, alpha-kinases and phosphatidylinositol phosphate kinases (PIPKs, appear to have distinct evolutionary histories. While the PIPKs probably have an

  19. Protein kinase CK2 in health and disease: Protein kinase CK2: from structures to insights

    DEFF Research Database (Denmark)

    Niefind, K; Raaf, J; Issinger, Olaf-Georg

    2009-01-01

    Within the last decade, 40 crystal structures corresponding to protein kinase CK2 (former name 'casein kinase 2'), to its catalytic subunit CK2alpha and to its regulatory subunit CK2beta were published. Together they provide a valuable, yet by far not complete basis to rationalize the biochemical...... critical region of CK2alpha recruitment is pre-formed in the unbound state. In CK2alpha the activation segment - a key element of protein kinase regulation - adapts invariably the typical conformation of the active enzymes. Recent structures of human CK2alpha revealed a surprising plasticity in the ATP...

  20. Differential Processing of Low and High LET Radiation Induced DNA Damage: Investigation of Switch from ATM to ATR Signaling

    Science.gov (United States)

    Saha, Janapriya; Wang, Minli; Hada, Megumi; Cucinotta, Francis A.

    2011-01-01

    The members of the phosphatidylinositol kinase-like kinase family of proteins namely ataxia-telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR) are directly responsible for the maintenance of genomic integrity by mounting DDR through signaling and facilitating the recruitment of repair factors at the sites of DNA damage along with coordinating the deployment of cell cycle checkpoints to permit repair by phosphorylating Checkpoint kinase Chk1, Chk2 and p53. High LET radiation from GCR (Galactic Cosmic Rays) consisting mainly of protons and high energy and charged (HZE) particles from SPE (Solar Particle Event) pose a major health risk for astronauts on their space flight missions. The determination of these risks and the design of potential safeguards require sound knowledge of the biological consequences of lesion induction and the capability of the cells to counter them. We here strive to determine the coordination of ATM and ATR kinases at the break sites directly affecting checkpoint signaling and DNA repair and whether differential processing of breaks induced by low and high LET radiation leads to possible augmentation of swap of these damage sensors at the sites of DNA damage. Exposure of cells to IR triggers rapid autophosphorylation of serine-1981 that causes dimer dissociation and initiates monomer formation of ATM. ATM kinase activity depends on the disruption of the dimer, which allows access and phosphorylation of downstream ATM substrates like Chk2. Evidence suggests that ATM is activated by the alterations in higher-order chromatin structure although direct binding of ATM to DSB ends may be a crucial step in its activation. On the other hand, in case of ATR, RPA (replication protein A)-coated ssDNA (single-stranded DNA) generated as a result of stalled DNA replication or during processing of chromosomal lesions is crucial for the localization of ATR to sites of DNA damage in association with ATR-interacting protein (ATRIP). Although the