151
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Jowsey PA, Williams FM, Blain PG. DNA damage responses in cells exposed to sulphur mustard. Toxicol Lett 2012; 209:1-10. [DOI: 10.1016/j.toxlet.2011.11.009] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 10/26/2011] [Accepted: 11/09/2011] [Indexed: 12/25/2022]
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152
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Quanz M, Herbette A, Sayarath M, de Koning L, Dubois T, Sun JS, Dutreix M. Heat shock protein 90α (Hsp90α) is phosphorylated in response to DNA damage and accumulates in repair foci. J Biol Chem 2012; 287:8803-15. [PMID: 22270370 DOI: 10.1074/jbc.m111.320887] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
DNA damage triggers a complex signaling cascade involving a multitude of phosphorylation events. We found that the threonine 7 (Thr-7) residue of heat shock protein 90α (Hsp90α) was phosphorylated immediately after DNA damage. The phosphorylated Hsp90α then accumulated at sites of DNA double strand breaks and formed repair foci with slow kinetics, matching the repair kinetics of complex DNA damage. The phosphorylation of Hsp90α was dependent on phosphatidylinositol 3-kinase-like kinases, including the DNA-dependent protein kinase (DNA-PK) in particular. DNA-PK plays an essential role in the repair of DNA double strand breaks by nonhomologous end-joining and in the signaling of DNA damage. It is also present in the cytoplasm of the cell and has been suggested to play a role in cytoplasmic signaling pathways. Using stabilized double-stranded DNA molecules to activate DNA-PK, we showed that an active DNA-PK complex could be assembled in the cytoplasm, resulting in phosphorylation of the cytoplasmic pool of Hsp90α. In vivo, reverse phase protein array data for tumors revealed that basal levels of Thr-7-phosphorylated Hsp90α were correlated with phosphorylated histone H2AX levels. The Thr-7 phosphorylation of the ubiquitously produced and secreted Hsp90α may therefore serve as a surrogate biomarker of DNA damage. These findings shed light on the interplay between central DNA repair enzymes and an essential molecular chaperone.
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Affiliation(s)
- Maria Quanz
- Institut Curie, CNRS UMR3347, INSERM U1021, Université Paris-Sud 11, Centre Universitaire, Orsay, France.
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153
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Abstract
Gliobastoma multiform (GBM) is the most common and aggressive brain tumor, which is characterized by its infiltrative nature. Current standard therapy for GBMs consists of surgery followed by radiotherapy combined with the alkylating agent temozolomide (TMZ). Recent clinical trials have demonstrated that this chemo-irradiation approach results in a significant increase in survival compared to radiotherapy alone. Nevertheless, due to tumor recurrence, the median survival time is still limited to approximately 15 months. Recently, several studies have focused on aberrant signal transduction in GBM, resistance mechanisms of GBM to TMZ and to radiotherapy. Attention has been focused on molecular targets including phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, protein kinase C (pKC) pathway, Ras/mitogen-activated protein kinase pathway (MAPK), Wnt pathway and intrinsic or extrinsic apoptosis pathways. In addition, research has been directed to radiotherapy and radiosensitizing agents, and cancer gene therapy as well. This article will address several resistance mechanisms of GBM to chemotherapy and radiotherapy and the recent preclinical and clinical studies on targeted therapy.
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Affiliation(s)
- N H Rekers
- Department of Medical Oncology, VU University Medical Center, The Netherlands
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154
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Liu Q, Kirubakaran S, Hur W, Niepel M, Westover K, Thoreen CC, Wang J, Ni J, Patricelli MP, Vogel K, Riddle S, Waller DL, Traynor R, Sanda T, Zhao Z, Kang SA, Zhao J, Look AT, Sorger PK, Sabatini DM, Gray NS. Kinome-wide selectivity profiling of ATP-competitive mammalian target of rapamycin (mTOR) inhibitors and characterization of their binding kinetics. J Biol Chem 2012; 287:9742-9752. [PMID: 22223645 DOI: 10.1074/jbc.m111.304485] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
An intensive recent effort to develop ATP-competitive mTOR inhibitors has resulted in several potent and selective molecules such as Torin1, PP242, KU63794, and WYE354. These inhibitors are being widely used as pharmacological probes of mTOR-dependent biology. To determine the potency and specificity of these agents, we have undertaken a systematic kinome-wide effort to profile their selectivity and potency using chemical proteomics and assays for enzymatic activity, protein binding, and disruption of cellular signaling. Enzymatic and cellular assays revealed that all four compounds are potent inhibitors of mTORC1 and mTORC2, with Torin1 exhibiting ∼20-fold greater potency for inhibition of Thr-389 phosphorylation on S6 kinases (EC(50) = 2 nM) relative to other inhibitors. In vitro biochemical profiling at 10 μM revealed binding of PP242 to numerous kinases, although WYE354 and KU63794 bound only to p38 kinases and PI3K isoforms and Torin1 to ataxia telangiectasia mutated, ATM and Rad3-related protein, and DNA-PK. Analysis of these protein targets in cellular assays did not reveal any off-target activities for Torin1, WYE354, and KU63794 at concentrations below 1 μM but did show that PP242 efficiently inhibited the RET receptor (EC(50), 42 nM) and JAK1/2/3 kinases (EC(50), 780 nM). In addition, Torin1 displayed unusually slow kinetics for inhibition of the mTORC1/2 complex, a property likely to contribute to the pharmacology of this inhibitor. Our results demonstrated that, with the exception of PP242, available ATP-competitive compounds are highly selective mTOR inhibitors when applied to cells at concentrations below 1 μM and that the compounds may represent a starting point for medicinal chemistry efforts aimed at developing inhibitors of other PI3K kinase-related kinases.
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Affiliation(s)
- Qingsong Liu
- Department of Cancer Biology, Dana Farber Cancer Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - Sivapriya Kirubakaran
- Department of Cancer Biology, Dana Farber Cancer Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - Wooyoung Hur
- Department of Cancer Biology, Dana Farber Cancer Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - Mario Niepel
- Center for Cell Decision Processes, and Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115
| | | | - Carson C Thoreen
- Department of Cancer Biology, Dana Farber Cancer Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - Jinhua Wang
- Department of Cancer Biology, Dana Farber Cancer Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - Jing Ni
- Department of Cancer Biology, Dana Farber Cancer Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | | | - Kurt Vogel
- Invitrogen Corp., Madison, Wisconsin 53719
| | | | - David L Waller
- Department of Cancer Biology, Dana Farber Cancer Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - Ryan Traynor
- National Centre for Protein Kinase Profiling, Dundee Division of Signal Transduction Therapy, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | - Takaomi Sanda
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215
| | - Zheng Zhao
- High Magnetic Field Laboratory, Chinese Academy of Science, P. O. Box 1110, Hefei, Anhui, 230031, China
| | - Seong A Kang
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, and; Koch Center for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Jean Zhao
- Department of Cancer Biology, Dana Farber Cancer Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - A Thomas Look
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215
| | - Peter K Sorger
- Center for Cell Decision Processes, and Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115
| | - David M Sabatini
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, and; Koch Center for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Nathanael S Gray
- Department of Cancer Biology, Dana Farber Cancer Institute, Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115.
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155
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Baer A, Austin D, Narayanan A, Popova T, Kainulainen M, Bailey C, Kashanchi F, Weber F, Kehn-Hall K. Induction of DNA damage signaling upon Rift Valley fever virus infection results in cell cycle arrest and increased viral replication. J Biol Chem 2012; 287:7399-410. [PMID: 22223653 DOI: 10.1074/jbc.m111.296608] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Rift Valley fever virus (RVFV) is a highly pathogenic arthropod-borne virus infecting a wide range of vertebrate hosts. Of particular interest is the nonstructural NSs protein, which forms large filamentous fibril bundles in the nucleus. Past studies have shown NSs to be a multifaceted protein important for virulence through modulation of the interferon response as well acting as a general inhibitor of transcription. Here we investigated the regulation of the DNA damage signaling cascades by RVFV infection and found virally inducted phosphorylation of the classical DNA damage signaling proteins, ataxia-telangiectasia mutated (ATM) (Ser-1981), Chk.2 (Thr-68), H2A.X (Ser-139), and p53 (Ser-15). In contrast, ataxia-telangiectasia mutated and Rad3-related kinase (ATR) (Ser-428) phosphorylation was decreased following RVFV infection. Importantly, both the attenuated vaccine strain MP12 and the fully virulent strain ZH548 showed strong parallels in their up-regulation of the ATM arm of the DNA damage response and in the down-regulation of the ATR pathway. The increase in DNA damage signaling proteins did not result from gross DNA damage as no increase in DNA damage was observed following infection. Rather the DNA damage signaling was found to be dependent on the viral protein NSs, as an NSs mutant virus was not found to induce the equivalent signaling pathways. RVFV MP12-infected cells also displayed an S phase arrest that was found to be dependent on NSs expression. Use of ATM and Chk.2 inhibitors resulted in a marked decrease in S phase arrest as well as viral production. These results indicate that RVFV NSs induces DNA damage signaling pathways that are beneficial for viral replication.
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Affiliation(s)
- Alan Baer
- National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, Virginia 20110, USA
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156
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Abstract
Phosphoinositide 3-kinases (PI3Ks) control cell growth, proliferation, cell survival, metabolic activity, vesicular trafficking, degranulation, and migration. Through these processes, PI3Ks modulate vital physiology. When over-activated in disease, PI3K promotes tumor growth, angiogenesis, metastasis or excessive immune cell activation in inflammation, allergy and autoimmunity. This chapter will introduce molecular activation and signaling of PI3Ks, and connections to target of rapamycin (TOR) and PI3K-related protein kinases (PIKKs). The focus will be on class I PI3Ks, and extend into current developments to exploit mechanistic knowledge for therapy.
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Affiliation(s)
- Matthias Wymann
- Institute Biochemistry & Genetics, Department Biomedicine, University of Basel, Mattenstrasse 28, 4058, Basel, Switzerland,
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157
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158
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Xu Y, Xu C, Price BD. Mechanistic links between ATM and histone methylation codes during DNA repair. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 110:263-88. [PMID: 22749149 DOI: 10.1016/b978-0-12-387665-2.00010-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The ataxia telangiectasia-mutated (ATM) protein kinase is the master regulator of the DNA double-strand break (DSB) repair pathway. The activation of ATM involves its recruitment to the DSB through interaction with the mre11-rad50-nbs1 complex, followed by the acetylation of ATM by the Tip60 acetyltransferase. This acetylation of ATM within its regulatory domain is essential for activating ATM's kinase activity. Further work has now revealed that Tip60 is activated through direct interaction between Tip60's chromodomain and histone H3 trimethylated on lysine 9 (H3K9me3). The loading of Tip60 onto the chromatin at DSBs therefore represents the primary mechanism for activation of Tip60's acetyltransferase activity in response to DNA damage. The ability of H3K9me3 at DSBs to regulate the activity of Tip60 and the subsequent activation of ATM emphasizes the crucial role played by chromatin architecture in regulating DSB repair. Further, histone methylation and chromatin structure are disrupted in human cancers, implying that altered chromatin structure in tumor cells may impact DSB repair, increasing genomic instability and contributing to the progression of cancer.
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Affiliation(s)
- Ye Xu
- Division of Genome Stability and DNA Repair, Department of Radiation Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA
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159
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Yu K, Toral-Barza L. Biochemical and pharmacological inhibition of mTOR by rapamycin and an ATP-competitive mTOR inhibitor. Methods Mol Biol 2012; 821:15-28. [PMID: 22125057 DOI: 10.1007/978-1-61779-430-8_2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The mammalian target of rapamycin (mTOR) is the catalytic subunit of two multiprotein complexes, mTOR complex-1 (mTORC1) and mTOR complex-2 (mTORC2). Clinically used rapamycin and rapalogs are FKBP12-dependent allosteric inhibitors of mTORC1. The recently discovered WYE-125132 and related drugs represent a new generation of ATP competitive and highly specific inhibitors targeting mTOR globally. As mTORC1 and mTORC2 mediate diverse sets of both redundant and distinctive cellular pathways of growth, nutrient and energy homeostasis, rapamycin and WYE-125132 elicit both overlapping and distinctive pharmacological properties with important implications in treating cancer, metabolic, and age-related degenerative diseases. Detailed methods are described for the determination of mTOR inhibition by rapamycin and WYE-125132 in assays of recombinant mTOR enzyme, immunprecipitated native mTOR complexes, growth factor- and amino acid-induced cellular phosphorylation cascades as well as the PI3K/AKT/mTOR hyperactive breast tumor model in vitro and in vivo. The methods have been particularly useful in discovery and biochemical characterization of mTOR inhibitors, cellular and in vivo mTOR substrate phosphorylation analysis, and in deciphering novel biomarkers of mTORC1 and mTORC2 signaling pathways.
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Affiliation(s)
- Ker Yu
- Cancer Pharmacology, Fudan University, Shanghai, PR, China.
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160
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Shen Y, Wang Y, Sheng K, Fei X, Guo Q, Larner J, Kong X, Qiu Y, Mi J. Serine/threonine protein phosphatase 6 modulates the radiation sensitivity of glioblastoma. Cell Death Dis 2011; 2:e241. [PMID: 22158480 PMCID: PMC3252736 DOI: 10.1038/cddis.2011.126] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Increasing the sensitivity of glioblastoma cells to radiation is a promising approach to improve survival in patients with glioblastoma multiforme (GBM). This study aims to determine if serine/threonine phosphatase (protein phosphatase 6 (PP6)) is a molecular target for GBM radiosensitization treatment. The GBM orthotopic xenograft mice model was used in this study. Our data demonstrated that the protein level of PP6 catalytic subunit (PP6c) was upregulated in the GBM tissue from about 50% patients compared with the surrounding tissue or control tissue. Both the in vitro survival fraction of GBM cells and the patient survival time were highly correlated or inversely correlated with PP6c expression (R2=0.755 and −0.707, respectively). We also found that siRNA knockdown of PP6c reduced DNA-dependent protein kinase (DNA-PK) activity in three different GBM cell lines, increasing their sensitivity to radiation. In the orthotopic mice model, the overexpression of PP6c in GBM U87 cells attenuated the effect of radiation treatment, and reduced the survival time of mice compared with the control mice, while the PP6c knocking-down improved the effect of radiation treatment, and increased the survival time of mice. These findings demonstrate that PP6 regulates the sensitivity of GBM cells to radiation, and suggest small molecules disrupting or inhibiting PP6 association with DNA-PK is a potential radiosensitizer for GBM.
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Affiliation(s)
- Y Shen
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Institute of Medical Science, Shanghai JiaoTong University School of Medicine, Shanghai, China
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161
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Ku regulates signaling to DNA damage response pathways through the Ku70 von Willebrand A domain. Mol Cell Biol 2011; 32:76-87. [PMID: 22037767 DOI: 10.1128/mcb.05661-11] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The Ku heterodimer (Ku70/Ku80) is a main component of the nonhomologous end-joining (NHEJ) pathway that repairs DNA double-strand breaks (DSBs). Ku binds the broken DNA end and recruits other proteins to facilitate the processing and ligation of the broken end. While Ku interacts with many proteins involved in DNA damage/repair-related functions, few interactions have been mapped to the N-terminal von Willebrand A (vWA) domain, a predicted protein interaction domain. The mutagenesis of Ku70 vWA domain S155/D156 unexpectedly increased cell survival following ionizing radiation (IR) treatment. DNA repair appeared unaffected, but defects in the activation of apoptosis and alterations in the DNA damage signaling response were identified. In particular, Ku70 S155A/D156A affected the IR-induced transcriptional response of several activating transcription factor 2 (ATF2)-regulated genes involved in apoptosis regulation. ATF2 phosphorylation and recruitment to DNA damage-induced foci was increased in Ku70-deficient cells, suggesting that Ku represses ATF2 activation. Ku70 S155A/D156A substitutions further enhanced this repression. S155A substitution alone was sufficient to confer enhanced survival, whereas alteration to a phosphomimetic residue (S155D) reversed this effect, suggesting that S155 is a phosphorylation site. Thus, these findings infer that Ku links signals from the DNA repair machinery to DNA damage signaling regulators that control apoptotic pathways.
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162
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Brzostek-Racine S, Gordon C, Van Scoy S, Reich NC. The DNA damage response induces IFN. THE JOURNAL OF IMMUNOLOGY 2011; 187:5336-45. [PMID: 22013119 DOI: 10.4049/jimmunol.1100040] [Citation(s) in RCA: 162] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
This study reveals a new complexity in the cellular response to DNA damage: activation of IFN signaling. The DNA damage response involves the rapid recruitment of repair enzymes and the activation of signal transducers that regulate cell-cycle checkpoints and cell survival. To understand the link between DNA damage and the innate cellular defense that occurs in response to many viral infections, we evaluated the effects of agents such as etoposide that promote dsDNA breaks. Treatment of human cells with etoposide led to the induction of IFN-stimulated genes and the IFN-α and IFN-λ genes. NF-κB, known to be activated in response to DNA damage, was shown to be a key regulator of this IFN gene induction. Expression of an NF-κB subunit, p65/RelA, was sufficient for induction of the human IFN-λ1 gene. In addition, NF-κB was required for the induction of IFN regulatory factor-1 and -7 that are able to stimulate expression of the IFN-α and IFN-λ genes. Cells that lack the NF-κB essential modulator lack the ability to induce the IFN genes following DNA damage. Breaks in DNA are generated during normal physiological processes of replication, transcription, and recombination, as well as by external genotoxic agents or infectious agents. The significant finding of IFN production as a stress response to DNA damage provides a new perspective on the role of IFN signaling.
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Affiliation(s)
- Sabrina Brzostek-Racine
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794-5200, USA
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163
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Abstract
The mechanistic (or mammalian) target of rapamycin (mTOR), an evolutionarily conserved protein kinase, orchestrates cellular responses to growth, metabolic and stress signals. mTOR processes various extracellular and intracellular inputs as part of two mTOR protein complexes, mTORC1 or mTORC2. The mTORCs have numerous cellular targets but members of a family of protein kinases, the protein kinase (PK)A/PKG/PKC (AGC) family are the best characterized direct mTOR substrates. The AGC kinases control multiple cellular functions and deregulation of many members of this family underlies numerous pathological conditions. mTOR phosphorylates conserved motifs in these kinases to allosterically augment their activity, influence substrate specificity, and promote protein maturation and stability. Activation of AGC kinases in turn triggers the phosphorylation of diverse, often overlapping, targets that ultimately control cellular response to a wide spectrum of stimuli. This review will highlight recent findings on how mTOR regulates AGC kinases and how mTOR activity is feedback regulated by these kinases. We will discuss how this regulation can modulate downstream targets in the mTOR pathway that could account for the varied cellular functions of mTOR.
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Affiliation(s)
- Bing Su
- Department of Immunobiology and The Vascular Biology and Therapeutics Program, Yale University School of Medicine, New Haven, CT, USA.
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164
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Yoshida S, Hong S, Suzuki T, Nada S, Mannan AM, Wang J, Okada M, Guan KL, Inoki K. Redox regulates mammalian target of rapamycin complex 1 (mTORC1) activity by modulating the TSC1/TSC2-Rheb GTPase pathway. J Biol Chem 2011; 286:32651-60. [PMID: 21784859 PMCID: PMC3173157 DOI: 10.1074/jbc.m111.238014] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Mammalian target of rapamycin (mTOR) is a kinase that plays a key role in a wide array of cellular processes and exists in two distinct functional complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). Although mTORC2 is primarily activated by growth factors, mTORC1 is regulated by numerous extracellular and intracellular signals such as nutrients, growth factors, and cellular redox. Previous study has shown that cysteine oxidants sufficiently activate mTORC1 activity under amino acid-depleted conditions and that a reducing agent effectively suppresses amino acid-induced mTORC1 activity, thereby raising the possibility that redox-sensitive mechanisms underlie amino acid-dependent mTORC1 regulation. However, the molecular mechanism by which redox regulates mTORC1 activity is not well understood. In this study, we show that the redox-sensitive regulation of mTORC1 occurs via Rheb but not the Rag small GTPase. Enhancing cellular redox potential with cysteine oxidants significantly increases Rheb GTP levels. Importantly, modulation of the cellular redox potential with a cysteine oxidant or reducing agent failed to alter mTORC1 activity in TSC1(-/-) or TSC2(-/-) mouse embryonic fibroblast cells. Furthermore, a cysteine oxidant has little effect on mTOR localization but sufficiently activates mTORC1 activity in both p18(-/-) and control mouse embryonic fibroblast cells, suggesting that the redox-sensitive regulation of mTORC1 occurs independent of the Ragulator·Rag complex. Taken together, our results suggest that the TSC complex plays an important role in redox-sensitive mTORC1 regulation and argues for the activation of mTORC1 in places other than the lysosome upon inhibition of the TSC complex.
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Affiliation(s)
| | | | | | - Shigeyuki Nada
- the Department of Oncogene Research, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan, and
| | | | | | - Masato Okada
- the Department of Oncogene Research, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan, and
| | - Kun-Liang Guan
- the Department of Pharmacology, Moores Cancer Center, University of California, San Diego, La Jolla, California 92093-0815
| | - Ken Inoki
- From the Life Sciences Institute and ,Departments of Molecular and Integrative Physiology and ,Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109, , To whom correspondence should be addressed: 210 Washtenaw Ave., Ann Arbor, MI 48109-2216. Fax: 734-647-9702; E-mail:
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165
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Bouquet F, Ousset M, Biard D, Fallone F, Dauvillier S, Frit P, Salles B, Muller C. A DNA-dependent stress response involving DNA-PK occurs in hypoxic cells and contributes to cellular adaptation to hypoxia. J Cell Sci 2011; 124:1943-51. [PMID: 21576354 DOI: 10.1242/jcs.078030] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
DNA-dependent protein kinase (DNA-PK) is involved in DNA double-strand break (DSB) signalling and repair. We report that DNA-PK is activated by mild hypoxia conditions (0.1-1% O₂) as shown by (1) its autophosphorylation on Ser2056, and (2) its mobilisation from a soluble nucleoplasmic compartment to a less extractable nuclear fraction. The recruitment of DNA-PK was not followed by activation and recruitment of the XRCC4-DNA-ligase-IV complex, suggesting that DSBs are not responsible for activation of DNA-PK. To unravel the mechanism of DNA-PK activation, we show that exposure of cells to trichostatin A, a histone deacetylase inhibitor, leads to DNA-PK autophosphorylation and relocalisation to DNA. Histone acetylation (mainly H3K14) is increased in hypoxic cells and treatment with anacardic acid, an inhibitor of histone acetyl transferase, prevented both histone modifications and DNA-PK activation in hypoxic conditions. Importantly, in using either silenced DNA-PK cells or cells exposed to a specific DNA-PK inhibitor (NU7026), we demonstrated that hypoxic DNA-PK activation positively regulates the key transcription factor HIF-1 and one subsequent target gene, GLUT1. Our results show that hypoxia initiates chromatin modification and consequently DNA-PK activation, which positively regulate cellular oxygen-sensing and oxygen-signalling pathways.
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Affiliation(s)
- Fanny Bouquet
- CNRS-IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse, France
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166
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Hanakahi L. Effect of the Inositol Polyphosphate InsP6 on DNA-PK–Dependent Phosphorylation. Mol Cancer Res 2011; 9:1366-76. [DOI: 10.1158/1541-7786.mcr-11-0230] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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167
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DE Wever O, Sobczak-Thépot J, Vercoutter-Edouart AS, Michalski JC, Ouelaa-Benslama R, Stupack DG, Bracke M, Wang JYJ, Gespach C, Emami S. Priming and potentiation of DNA damage response by fibronectin in human colon cancer cells and tumor-derived myofibroblasts. Int J Oncol 2011; 39:393-400. [PMID: 21567080 PMCID: PMC5003111 DOI: 10.3892/ijo.2011.1034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Accepted: 02/28/2011] [Indexed: 12/16/2022] Open
Abstract
We have previously shown that the genotoxin-induced apoptosis in mouse embryo fibroblasts was enhanced by the extracellular matrix protein fibronectin (FN). In the present study, we tested the hypothesis that FN regulates the DNA damage response (DDR) signaling pathways in HCT116 (p53-wt) and HT29 (p53-mut) human colon cancer cells and tumor-derived myofibroblasts. DNA damage recognition mechanisms were analyzed by immunofluorescence staining, cell cycle analysis and immunoblotting addressed at specific molecular sensors and executors involved in the DDR pathways. The results show that FN, but not collagen type IV or Matrigel, initiates and potentiates the DDR to the anticancer drug cisplatin in an α5 integrin and cell cycle-dependent manner (S and G2/M phases) in human colon cancer cells. Accordingly, we demonstrate that adhesion of HCT116 cells to FN upregulated the expression of α5 integrin FN receptors at the cell surface. These FN-induced DDR pathways include the concerted phosphorylation of histone H2AX on Ser139 detected as nuclear foci (γ-H2AX, 15 and 25 kDa forms), of ataxia telangiectasia mutated (ATM-Ser1981), checkpoint kinase 2 (CHK2-Thr68, 62 and 67 kDa) and p53-Ser15. These FN-induced γ-H2AX signals were interrupted or attenuated by selective inhibitors acting on the DDR pathway kinases, including wortmannin (targeting the phosphatidylinositol-3-kinase-related protein kinases, PIKK), KU55933 (ATM), NU7026 (DNA-dependent protein kinase catalytic subunit, DNA-PK-cs) and SP600125 (JNK2, stress activated protein kinase/c-Jun N-terminal kinase-2). Adhesion to FN also potentiated the γ-H2AX signals and the cytotoxic effects of cisplatin in human colon tumor-derived myofibroblasts. These data provide evidence that FN promotes DNA damage recognition and chemosensitization to cisplatin via the potentiation of the DNA damage signaling responses in human colon cancer cells and tumor-derived myofibroblasts.
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Affiliation(s)
- Olivier DE Wever
- Laboratory of Experimental Cancerology, Ghent University Hospital, Ghent, Belgium
| | | | | | - Jean-Claude Michalski
- Unité de Glycobiologie Structurale et Fonctionnelle UMR USTL/CNRS no. 8576 - IFR147, Villeneuve-d'Ascq, France
| | - Radia Ouelaa-Benslama
- INSERM U673 and U938, Laboratory of Cancer Biology and Therapeutics, Centre de recherche Saint-Antoine
| | - Dwayne G Stupack
- Moores UCSD Cancer Center, UCSD School of Medicine, La Jolla, CA, USA
| | - Marc Bracke
- Laboratory of Experimental Cancerology, Ghent University Hospital, Ghent, Belgium
| | - Jean Y J Wang
- Moores UCSD Cancer Center, UCSD School of Medicine, La Jolla, CA, USA
| | - Christian Gespach
- INSERM U673 and U938, Laboratory of Cancer Biology and Therapeutics, Centre de recherche Saint-Antoine
- Université Pierre-et-Marie-Curie (UPMC) Paris-6, Paris, France
| | - Shahin Emami
- INSERM U673 and U938, Laboratory of Cancer Biology and Therapeutics, Centre de recherche Saint-Antoine
- Université Pierre-et-Marie-Curie (UPMC) Paris-6, Paris, France
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168
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O'Driscoll M. Haploinsufficiency of DNA Damage Response Genes and their Potential Influence in Human Genomic Disorders. Curr Genomics 2011; 9:137-46. [PMID: 19440510 PMCID: PMC2679649 DOI: 10.2174/138920208784340795] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2008] [Revised: 03/31/2008] [Accepted: 03/31/2008] [Indexed: 11/22/2022] Open
Abstract
Genomic disorders are a clinically diverse group of conditions caused by gain, loss or re-orientation of a genomic region containing dosage-sensitive genes. One class of genomic disorder is caused by hemizygous deletions resulting in haploinsufficiency of a single or, more usually, several genes. For example, the heterozygous contiguous gene deletion on chromosome 22q11.2 causing DiGeorge syndrome involves at least 20-30 genes. Determining how the copy number variation (CNV) affects human variation and contributes to the aetiology and progression of various genomic disorders represents important questions for the future. Here, I will discuss the functional significance of one form of CNV, haploinsufficiency (i.e. loss of a gene copy), of DNA damage response components and its association with certain genomic disorders. There is increasing evidence that haploinsufficiency for certain genes encoding key players in the cells response to DNA damage, particularly those of the Ataxia Telangiectasia and Rad3-related (ATR)-pathway, has a functional impact. I will review this evidence and present examples of some well known clinically similar genomic disorders that have recently been shown to be defective in the ATR-dependent DNA damage response. Finally, I will discuss the potential implications of a haploinsufficiency-induced defective DNA damage response for the clinical management of certain human genomic disorders.
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Affiliation(s)
- Mark O'Driscoll
- Genome Damage & Stability Centre, University of Sussex, Falmer, Brighton, East Sussex, BN1 9RQ, UK
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169
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Soares DG, Battistella A, Rocca CJ, Matuo R, Henriques JAP, Larsen AK, Escargueil AE. Ataxia telangiectasia mutated- and Rad3-related kinase drives both the early and the late DNA-damage response to the monofunctional antitumour alkylator S23906. Biochem J 2011; 437:63-73. [PMID: 21470188 DOI: 10.1042/bj20101770] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Numerous anticancer agents and environmental mutagens target DNA. Although all such compounds interfere with the progression of the replication fork and inhibit DNA synthesis, there are marked differences in the DNA-damage response pathways they trigger, and the relative impact of the proximal or the distal signal transducers on cell survival is mainly lesion-specific. Accordingly, checkpoint kinase inhibitors in current clinical development show synergistic activity with some DNA-targeting agents, but not with others. In the present study, we characterize the DNA-damage response to the antitumour acronycine derivative S23906, which forms monofunctional adducts with guanine residues in the minor groove of DNA. S23906 exposure is accompanied by specific recruitment of RPA (replication protein A) at replication sites and rapid Chk1 activation. In contrast, neither MRN (Mre11-Rad50-Nbs1) nor ATM (ataxia-telangiectasia mutated), contributes to the initial response to S23906. Interestingly, genetic attenuation of ATR (ATM- and Ras3-related) activity inhibits not only the early phosphorylation of histone H2AX and Chk1, but also interferes with the late phosphorylation of Chk2. Moreover, loss of ATR function or pharmacological inhibition of the checkpoint kinases by AZD7762 is accompanied by abrogation of the S-phase arrest and increased sensitivity towards S23906. These findings identify ATR as a central co-ordinator of the DNA-damage response to S23906, and provide a mechanistic rationale for combinations of S23906 and similar agents with checkpoint abrogators.
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Affiliation(s)
- Daniele G Soares
- Laboratory of Cancer Biology and Therapeutics, Centre de Recherche Saint-Antoine, Paris 75571, France
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170
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Pawelczak KS, Bennett SM, Turchi JJ. Coordination of DNA-PK activation and nuclease processing of DNA termini in NHEJ. Antioxid Redox Signal 2011; 14:2531-43. [PMID: 20698792 PMCID: PMC3096510 DOI: 10.1089/ars.2010.3368] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
DNA double-strand breaks (DSB), particularly those induced by ionizing radiation (IR), are complex lesions that can be cytotoxic if not properly repaired. IR-induced DSB often have DNA termini modifications, including thymine glycols, ring fragmentation, 3'-phosphoglycolates, 5'-hydroxyl groups, and abasic sites. Nonhomologous end joining (NHEJ) is a major pathway responsible for the repair of these complex breaks. Proteins involved in NHEJ include the Ku 70/80 heterodimer, DNA-PKcs, processing proteins including Artemis and DNA polymerases μ and λ, XRCC4, DNA ligase IV, and XLF. We will discuss the role of the physical and functional interactions of DNA-PK as a result of activation, with an emphasis on DNA structure, chemistry, and sequence. With the diversity of IR induced DSB, it is becoming increasingly clear that multiple DNA processing enzymes are likely necessary for effective repair of a break. We will explore the roles of several important processing enzymes, with a focus on the nuclease Artemis and its role in processing diverse DSB. The effect of DNA termini on both DNA-PK and Artemis activity will be analyzed from a structural and biochemical view.
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Affiliation(s)
- Katherine S Pawelczak
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 980 W. Walnut St., Indianapolis, IN 46202, USA
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171
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Liu Q, Wang J, Kang SA, Thoreen CC, Hur W, Choi HG, Waller DL, Sim T, Sabatini DM, Gray NS. Discovery and optimization of potent and selective benzonaphthyridinone analogs as small molecule mTOR inhibitors with improved mouse microsome stability. Bioorg Med Chem Lett 2011; 21:4036-40. [PMID: 21621413 DOI: 10.1016/j.bmcl.2011.04.129] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2011] [Revised: 04/26/2011] [Accepted: 04/27/2011] [Indexed: 12/31/2022]
Abstract
Starting from small molecule mTOR inhibitor Torin1, replacement of the piperazine ring with a phenyl ring resulted in a new series of mTOR inhibitors (as exemplified by 10) that showed superior potency and selectivity for mTOR, along with significantly improved mouse liver microsome stability and a longer in vivo half-life.
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Affiliation(s)
- Qingsong Liu
- Department of Cancer Biology, Dana Farber Cancer Institute, 44 Binney Street, Boston, MA 02115, USA
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172
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Kong X, Shen Y, Jiang N, Fei X, Mi J. Emerging roles of DNA-PK besides DNA repair. Cell Signal 2011; 23:1273-80. [PMID: 21514376 DOI: 10.1016/j.cellsig.2011.04.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2010] [Revised: 03/13/2011] [Accepted: 04/04/2011] [Indexed: 10/24/2022]
Abstract
The DNA-dependent protein kinase (DNA-PK) is a DNA-activated serine/threonine protein kinase, and abundantly expressed in almost all mammalian cells. The roles of DNA-PK in DNA-damage repair pathways, including non-homologous end-joining (NHEJ) repair and homologous recombinant (HR) repair, have been studied intensively. However, the high levels of DNA-PK in human cells are somewhat paradoxical in that it does not impart any increased ability to repair DNA damage. If DNA-PK essentially exceeds the demand for DNA damage repair, why do human cells universally express such high levels of this huge complex? DNA-PK has been recently reported to be involved in metabolic gene regulation in response to feeding/insulin stimulation; our studies have also suggested a role of DNA-PK in the regulation of the homeostasis of cell proliferation. These novel findings expand our horizons about the importance of DNA-PK.
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Affiliation(s)
- Xianming Kong
- Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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173
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Morris EP, Rivera-Calzada A, da Fonseca PCA, Llorca O, Pearl LH, Spagnolo L. Evidence for a remodelling of DNA-PK upon autophosphorylation from electron microscopy studies. Nucleic Acids Res 2011; 39:5757-67. [PMID: 21450809 PMCID: PMC3141256 DOI: 10.1093/nar/gkr146] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The multi-subunit DNA-dependent protein kinase (DNA-PK), a crucial player in DNA repair by non-homologous end-joining in higher eukaryotes, consists of a catalytic subunit (DNA-PKcs) and the Ku heterodimer. Ku recruits DNA-PKcs to double-strand breaks, where DNA-PK assembles prior to DNA repair. The interaction of DNA-PK with DNA is regulated via autophosphorylation. Recent SAXS data addressed the conformational changes occurring in the purified catalytic subunit upon autophosphorylation. Here, we present the first structural analysis of the effects of autophosphorylation on the trimeric DNA-PK enzyme, performed by electron microscopy and single particle analysis. We observe a considerable degree of heterogeneity in the autophosphorylated material, which we resolved into subpopulations of intact complex, and separate DNA-PKcs and Ku, by using multivariate statistical analysis and multi-reference alignment on a partitioned particle image data set. The proportion of dimeric oligomers was reduced compared to non-phosphorylated complex, and those dimers remaining showed a substantial variation in mutual monomer orientation. Together, our data indicate a substantial remodelling of DNA-PK holo-enzyme upon autophosphorylation, which is crucial to the release of protein factors from a repaired DNA double-strand break.
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Affiliation(s)
- Edward P Morris
- Structural Electron Microscopy Group, Section of Structural Biology, The Institute of Cancer Research, London SW3 6JB, UK
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174
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Arias-Palomo E, Yamashita A, Fernández IS, Núñez-Ramírez R, Bamba Y, Izumi N, Ohno S, Llorca O. The nonsense-mediated mRNA decay SMG-1 kinase is regulated by large-scale conformational changes controlled by SMG-8. Genes Dev 2011; 25:153-64. [PMID: 21245168 DOI: 10.1101/gad.606911] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Nonsense-mediated mRNA decay (NMD) is a eukaryotic surveillance pathway that regulates the degradation of mRNAs harboring premature translation termination codons. NMD also influences the expression of many physiological transcripts. SMG-1 is a large kinase essential to NMD that phosphorylates Upf1, which seems to be the definitive signal triggering mRNA decay. However, the regulation of the kinase activity of SMG-1 remains poorly understood. Here, we reveal the three-dimensional architecture of SMG-1 in complex with SMG-8 and SMG-9, and the structural mechanisms regulating SMG-1 kinase. A bent arm comprising a long region of HEAT (huntington, elongation factor 3, a subunit of PP2A and TOR1) repeats at the N terminus of SMG-1 functions as a scaffold for SMG-8 and SMG-9, and projects from the C-terminal core containing the phosphatidylinositol 3-kinase domain. SMG-9 seems to control the activity of SMG-1 indirectly through the recruitment of SMG-8 to the N-terminal HEAT repeat region of SMG-1. Notably, SMG-8 binding to the SMG-1:SMG-9 complex specifically down-regulates the kinase activity of SMG-1 on Upf1 without contacting the catalytic domain. Assembly of the SMG-1:SMG-8:SMG-9 complex induces a significant motion of the HEAT repeats that is signaled to the kinase domain. Thus, large-scale conformational changes induced by SMG-8 after SMG-9-mediated recruitment tune SMG-1 kinase activity to modulate NMD.
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Affiliation(s)
- Ernesto Arias-Palomo
- Centro de Investigaciones Biológicas (CIB), Spanish National Research Council (Consejo Superior de Investigaciones Científicas, CSIC), 28040 Madrid, Spain
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175
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Liu Q, Wang J, Kang SA, Thoreen CC, Hur W, Ahmed T, Sabatini DM, Gray NS. Discovery of 9-(6-aminopyridin-3-yl)-1-(3-(trifluoromethyl)phenyl)benzo[h][1,6]naphthyridin-2(1H)-one (Torin2) as a potent, selective, and orally available mammalian target of rapamycin (mTOR) inhibitor for treatment of cancer. J Med Chem 2011; 54:1473-80. [PMID: 21322566 DOI: 10.1021/jm101520v] [Citation(s) in RCA: 161] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The mTOR mediated PI3K/AKT/mTOR signal transduction pathway has been demonstrated to play a key role in a broad spectrum of cancers. Starting from the mTOR selective inhibitor 1 (Torin1), a focused medicinal chemistry effort led to the discovery of an improved mTOR inhibitor 3 (Torin2), which possesses an EC(50) of 0.25 nM for inhibiting cellular mTOR activity. Compound 3 exhibited 800-fold selectivity over PI3K (EC(50): 200 nM) and over 100-fold binding selectivity relative to 440 other protein kinases. Compound 3 has significantly improved bioavailability (54%), metabolic stability, and plasma exposure relative to compound 1.
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Affiliation(s)
- Qingsong Liu
- Department of Cancer Biology, Dana Farber Cancer Institute, 44 Binney Street, Boston, Massachusetts 02115, United States
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176
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hSMG-1 is a granzyme B-associated stress-responsive protein kinase. J Mol Med (Berl) 2011; 89:411-21. [DOI: 10.1007/s00109-010-0708-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 11/24/2010] [Accepted: 11/25/2010] [Indexed: 10/18/2022]
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177
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Dar I, Yosha G, Elfassy R, Galron R, Wang ZQ, Shiloh Y, Barzilai A. Investigation of the functional link between ATM and NBS1 in the DNA damage response in the mouse cerebellum. J Biol Chem 2011; 286:15361-76. [PMID: 21300797 DOI: 10.1074/jbc.m110.204172] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ataxia-telangiectasia (A-T) and Nijmegen breakage syndrome (NBS) are related genomic instability syndromes characterized by neurological deficits. The NBS1 protein that is defective in NBS is a component of the Mre11/RAD50/NBS1 (MRN) complex, which plays a major role in the early phase of the complex cellular response to double strand breaks (DSBs) in the DNA. Among others, Mre11/RAD50/NBS1 is required for timely activation of the protein kinase ATM (A-T, mutated), which is missing or inactivated in patients with A-T. Understanding the molecular pathology of A-T, primarily its cardinal symptom, cerebellar degeneration, requires investigation of the DSB response in cerebellar neurons, particularly Purkinje cells, which are the first to be lost in A-T patients. Cerebellar cultures derived from mice with different mutations in DNA damage response genes is a useful experimental system to study malfunctioning of the damage response in the nervous system. To clarify the interrelations between murine Nbs1 and Atm, we generated a mouse strain with specific disruption of the Nbs1 gene in the central nervous system on the background of general Atm deficiency (Nbs1-CNS-Δ//Atm(-/-)). This genotype exacerbated several features of both conditions and led to a markedly reduced life span, dramatic decline in the number of cerebellar granule neurons with considerable cerebellar disorganization, abolishment of the white matter, severe reduction in glial cell proliferation, and delayed DSB repair in cerebellar tissue. Combined loss of Nbs1 and Atm in the CNS significantly abrogated the DSB response compared with the single mutation genotypes. Importantly, the data indicate that Atm has cellular roles not regulated by Nbs1 in the murine cerebellum.
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Affiliation(s)
- Inbal Dar
- Department of Neurobiology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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178
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Pabla N, Ma Z, McIlhatton MA, Fishel R, Dong Z. hMSH2 recruits ATR to DNA damage sites for activation during DNA damage-induced apoptosis. J Biol Chem 2011; 286:10411-8. [PMID: 21285353 DOI: 10.1074/jbc.m110.210989] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
DNA damage response (DDR) activates a complex signaling network that triggers DNA repair, cell cycle arrest, and/or cell death. Depending on the type and severity of DNA lesion, DDR is controlled by "master" regulators including ATM and ATR protein kinases. Cisplatin, a major chemotherapy drug that cross-links DNA, induces ATR-dependent DDR, resulting in apoptosis. However, it is unclear how ATR is activated. To identify the key regulators of ATR, we analyzed the proteins that associate with ATR after cisplatin treatment by blue native-PAGE and co-immunoprecipitation. The mismatch repair protein hMSH2 was found to be a major ATR-binding protein. Functionally, ATR activation and its recruitment to nuclear foci during cisplatin treatment were attenuated, and DNA damage signaling, involving Chk2, p53, and PUMA-α, was suppressed in hMSH2-deficient cells. ATR activation induced by the DNA methylating agent N-methyl-N-nitrosourea was also shown to be hMSH2-dependent. Intriguingly, hMSH2-mediated ATR recruitment and activation appeared independent of replication protein A, Rad17, and the Rad9-Hus1-Rad1 protein complex. Together the results support a hMSH2-dependent pathway of ATR activation and downstream Chk2/p53 signaling.
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Affiliation(s)
- Navjotsingh Pabla
- Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, Georgia 30912, USA
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179
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Cuffe S, Dowling CM, Claffey J, Pampillón C, Hogan M, Fitzpatrick JM, Carty MP, Tacke M, Watson RWG. Effects of titanocene dichloride derivatives on prostate cancer cells, specifically DNA damage-induced apoptosis. Prostate 2011; 71:111-24. [PMID: 20665530 DOI: 10.1002/pros.21227] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND While locally advanced prostate cancer is initially treatable with androgen ablation, eventually cells develop a castrate-resistant phenotype. Currently, there are no effective treatments for this form of the disease with Docetaxel only providing a small survival advantage. In this study, the effects of novel derivatives of titanocene dichloride on prostate cancer cell lines has been investigated. METHODS Cellular effects were assessed using the crystal violet assay and the clonogenic survival assay. Cell cycle and apoptosis were assessed by propidium iodide staining. DNA damage was analyzed by comet assay and Western analysis. DNA damage response inhibition was achieved by pre-incubation with an ATM/ATR inhibitor; CGK733 and DNA-PK inhibitor; DMNB. RESULTS These analogs caused a reduction in cell number. In particular titanocene Y and C had significant effects in all cell lines. A reduction in clonogenic survival was found in response to titanocene Y in three cell lines while the PC-3 cells exhibited increased resistance.Further analysis showed no effect on cell cycle however, the analogs were found to induce apoptosis in a dose-dependent manner in all cell lines. These analogs associate with DNA, induce DNA damage and a differential damage response. Inhibition of key regulators of this DNA damage response sensitized the PC-3 cell line to titanocene-induced apoptosis and significantly reduced the clonogenic capacity of the cells. CONCLUSION These results demonstrate the mechanism of action of these novel titanocene dichloride analogs and their potential use in castrate-independent advanced prostate cancer.
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Affiliation(s)
- Sandra Cuffe
- UCD School of Medicine and Medical Science, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, Ireland.
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180
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Kalghatgi S, Kelly CM, Cerchar E, Torabi B, Alekseev O, Fridman A, Friedman G, Azizkhan-Clifford J. Effects of non-thermal plasma on mammalian cells. PLoS One 2011; 6:e16270. [PMID: 21283714 PMCID: PMC3025030 DOI: 10.1371/journal.pone.0016270] [Citation(s) in RCA: 265] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2010] [Accepted: 12/09/2010] [Indexed: 11/18/2022] Open
Abstract
Thermal plasmas and lasers have been widely used in medicine to cut, ablate and cauterize tissues through heating; in contrast, non-thermal plasma produces no heat, so its effects can be selective. In order to exploit the potential for clinical applications, including wound healing, sterilization, blood coagulation, and cancer treatment, a mechanistic understanding of the interaction of non-thermal plasma with living tissues is required. Using mammalian cells in culture, it is shown here that non-thermal plasma created by dielectric barrier discharge (DBD) has dose-dependent effects that range from increasing cell proliferation to inducing apoptosis. It is also shown that these effects are primarily due to formation of intracellular reactive oxygen species (ROS). We have utilized γ-H2AX to detect DNA damage induced by non-thermal plasma and found that it is initiated by production of active neutral species that most likely induce formation of organic peroxides in cell medium. Phosphorylation of H2AX following non-thermal plasma treatment is ATR dependent and ATM independent, suggesting that plasma treatment may lead to replication arrest or formation of single-stranded DNA breaks; however, plasma does not lead to formation of bulky adducts/thymine dimers.
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Affiliation(s)
- Sameer Kalghatgi
- Department of Electrical and Computer Engineering, Drexel University, Philadelphia, Pennsylvania, United States of America
| | - Crystal M. Kelly
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Ekaterina Cerchar
- Department of Surgery, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Behzad Torabi
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Oleg Alekseev
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Alexander Fridman
- Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, Pennsylvania, United States of America
| | - Gary Friedman
- Department of Electrical and Computer Engineering, Drexel University, Philadelphia, Pennsylvania, United States of America
| | - Jane Azizkhan-Clifford
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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181
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Hardt M, Chantaravisoot N, Tamanoi F. Activating mutations of TOR (target of rapamycin). Genes Cells 2011; 16:141-51. [PMID: 21210909 DOI: 10.1111/j.1365-2443.2010.01482.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Mammalian target of rapamycin (mTOR) is a key regulator of eukaryotic cell growth. In particular, mTORC1, one of the two complexes that contain mTOR, is involved in the regulation of protein synthesis, proliferation, cell cycle and autophagy. Hyperactivation of the mTOR signaling pathway is observed in human cancer. A variety of approaches including deletion analysis, yeast genetic screens and mining of human cancer genome databases were taken that resulted in the identification of activating mutations of TOR. These studies suggest that the FAT, FRB and kinase domains are the three regions of TOR where activating mutations can be identified. Within the kinase domain, the mutations are clustered in three hot spots that are all located in the kinase active site that was deduced by the alignment with PI3K. One of the hot spots corresponds to the region where PI3K oncogenic mutations have been identified. These results are beginning to provide important insights into the mechanism of activation of mTOR.
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Affiliation(s)
- Molly Hardt
- Department of Microbiology, Immunology and Molecular Genetics, Jonsson Comprehensive Cancer Center, Molecular Biology Institute, University of California, Los Angeles, CA 90095-1489, USA
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182
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Vogt PK, Hart JR, Gymnopoulos M, Jiang H, Kang S, Bader AG, Zhao L, Denley A. Phosphatidylinositol 3-kinase: the oncoprotein. Curr Top Microbiol Immunol 2011; 347:79-104. [PMID: 20582532 DOI: 10.1007/82_2010_80] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The catalytic and regulatory subunits of class I phosphoinositide 3-kinase (PI3K) have oncogenic potential. The catalytic subunit p110α and the regulatory subunit p85 undergo cancer-specific gain-of-function mutations that lead to enhanced enzymatic activity, ability to signal constitutively, and oncogenicity. The β, γ, and δ isoforms of p110 are cell-transforming as overexpressed wild-type proteins. Class I PI3Ks have the unique ability to generate phosphoinositide 3,4,5 trisphosphate (PIP(3)). Class II and class III PI3Ks lack this ability. Genetic and cell biological evidence suggests that PIP(3) is essential for PI3K-mediated oncogenicity, explaining why class II and class III enzymes have not been linked to cancer. Mutational analysis reveals the existence of at least two distinct molecular mechanisms for the gain of function seen with cancer-specific mutations in p110α; one causing independence from upstream receptor tyrosine kinases, the other inducing independence from Ras. An essential component of the oncogenic signal that is initiated by PI3K is the TOR (target of rapamycin) kinase. TOR is an integrator of growth and of metabolic inputs. In complex with the raptor protein (TORC1), it controls cap-dependent translation, and this function is essential for PI3K-initiated oncogenesis.
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Affiliation(s)
- Peter K Vogt
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
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183
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Xie Y, Awonuga AO, Zhou S, Puscheck EE, Rappolee DA. Interpreting the stress response of early mammalian embryos and their stem cells. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2011; 287:43-95. [PMID: 21414586 DOI: 10.1016/b978-0-12-386043-9.00002-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
This review analyzes and interprets the normal, pathogenic, and pathophysiological roles of stress and stress enzymes in mammalian development. Emerging data suggest that stem cells from early embryos are induced by stress to perform stress-enzyme-mediated responses that use the strategies of compensatory, prioritized, and reversible differentiation. These strategies have been optimized during evolution and in turn have aspects of energy conservation during stress that optimize and maximize the efficacy of the stress response. It is likely that different types of stem cells have varying degrees of flexibility in mediating compensatory and prioritized differentiation. The significance of this analysis and interpretation is that it will serve as a foundation for yielding tools for diagnosing, understanding normal and pathophysiological mechanisms, and providing methods for managing stress enzymes to improve short- and long-term reproductive outcomes.
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Affiliation(s)
- Y Xie
- CS Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, Michigan, USA
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184
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Abstract
The Ataxia-Telangiectasia mutated (ATM) kinase is regarded as the major regulator of the cellular response to DNA double strand breaks (DSBs). In response to DSBs, ATM dimers dissociate into active monomers in a process promoted by the Mre11-Rad50-Nbs1 (MRN) complex. ATM can also be activated by oxidative stress directly in the form of exposure to H2O2. The active ATM in this case is a disulfide-crosslinked dimer containing 2 or more disulfide bonds. Mutation of a critical cysteine residue in the FATC domain involved in disulfide bond formation specifically blocks ATM activation by oxidative stress. Here we show that ATM activation by DSBs is inhibited in the presence of H2O2 because oxidation blocks the ability of MRN to bind to DNA. However, ATM activation via direct oxidation by H2O2 complements the loss of MRN/DSB-dependent activation and contributes significantly to the overall level of ATM activity in the presence of both DSBs and oxidative stress.
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Affiliation(s)
- Zhi Guo
- Howard Hughes Medical Institute, University of Texas at Austin, Austin, TX, USA
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Domains of Tra1 important for activator recruitment and transcription coactivator functions of SAGA and NuA4 complexes. Mol Cell Biol 2010; 31:818-31. [PMID: 21149579 DOI: 10.1128/mcb.00687-10] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The Tra1 protein is a direct transcription activator target that is essential for coactivator function of both the SAGA and NuA4 histone acetyltransferase (HAT) complexes. The ∼400-kDa Saccharomyces cerevisiae Tra1 polypeptide and its human counterpart TRRAP contain 67 or 68 tandem α-helical HEAT and TPR protein repeats that extend from the N terminus to the conserved yet catalytically inactive phosphatidylinositol 3-kinase (PI3K) domain. We generated a series of mutations spanning the length of the protein and assayed for defects in transcription, coactivator recruitment, and histone acetylation at SAGA- and NuA4-dependent genes. Inviable TRA1 mutants all showed defects in SAGA and NuA4 complex stability, suggesting that similar surfaces of Tra1 mediate assembly of these two very different coactivator complexes. Nearly all of the viable Tra1 mutants showed transcription defects that fell into one of three classes: (i) defective recruitment to promoters, (ii) reduced stability of the SAGA and NuA4 HAT modules, or (iii) normal recruitment of Tra1-associated subunits but reduced HAT activity in vivo. Our results show that Tra1 recruitment at Gcn4-dependent and Rap1-dependent promoters requires the same regions of Tra1 and that separate regions of Tra1 contribute to the HAT activity and stability of the SAGA and NuA4 HAT modules.
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186
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Bau DT, Chang CH, Tsai MH, Chiu CF, Tsou YA, Wang RF, Tsai CW, Tsai RY. Association between DNA repair gene ATM polymorphisms and oral cancer susceptibility. Laryngoscope 2010; 120:2417-22. [DOI: 10.1002/lary.21009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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187
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Liu Q, Chang JW, Wang J, Kang SA, Thoreen CC, Markhard A, Hur W, Zhang J, Sim T, Sabatini DM, Gray NS. Discovery of 1-(4-(4-propionylpiperazin-1-yl)-3-(trifluoromethyl)phenyl)-9-(quinolin-3-yl)benzo[h][1,6]naphthyridin-2(1H)-one as a highly potent, selective mammalian target of rapamycin (mTOR) inhibitor for the treatment of cancer. J Med Chem 2010; 53:7146-55. [PMID: 20860370 DOI: 10.1021/jm101144f] [Citation(s) in RCA: 174] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The mTOR protein is a master regulator of cell growth and proliferation, and inhibitors of its kinase activity have the potential to become new class of anticancer drugs. Starting from quinoline 1, which was identified in a biochemical mTOR assay, we developed a tricyclic benzonaphthyridinone inhibitor 37 (Torin1), which inhibited phosphorylation of mTORC1 and mTORC2 substrates in cells at concentrations of 2 and 10 nM, respectively. Moreover, Torin1 exhibits 1000-fold selectivity for mTOR over PI3K (EC(50) = 1800 nM) and exhibits 100-fold binding selectivity relative to 450 other protein kinases. Torin1 was efficacious at a dose of 20 mg/kg in a U87MG xenograft model and demonstrated good pharmacodynamic inhibition of downstream effectors of mTOR in tumor and peripheral tissues. These results demonstrate that Torin1 is a useful probe of mTOR-dependent phenomena and that benzonaphthridinones represent a promising scaffold for the further development of mTOR-specific inhibitors with the potential for clinical utility.
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Affiliation(s)
- Qingsong Liu
- Department of Cancer Biology, Dana Farber Cancer Institute, 44 Binney Street, Boston, Massachusetts 02115, USA
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188
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Al-Hakim A, Escribano-Diaz C, Landry MC, O'Donnell L, Panier S, Szilard RK, Durocher D. The ubiquitous role of ubiquitin in the DNA damage response. DNA Repair (Amst) 2010; 9:1229-40. [PMID: 21056014 PMCID: PMC7105183 DOI: 10.1016/j.dnarep.2010.09.011] [Citation(s) in RCA: 174] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/05/2010] [Indexed: 01/22/2023]
Abstract
Protein ubiquitylation has emerged as an important regulatory mechanism that impacts almost every aspect of the DNA damage response. In this review, we discuss how DNA repair and checkpoint pathways utilize the diversity offered by the ubiquitin conjugation system to modulate the response to genotoxic lesions in space and time. In particular, we will highlight recent work done on the regulation of DNA double-strand breaks signalling and repair by the RNF8/RNF168 E3 ubiquitin ligases, the Fanconi anemia pathway and the role of protein degradation in the enforcement and termination of checkpoint signalling. We also discuss the various functions of deubiquitylating enzymes in these processes along with potential avenues for exploiting the ubiquitin conjugation/deconjugation system for therapeutic purposes.
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Affiliation(s)
- Abdallah Al-Hakim
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, M5G 1X5, ON, Canada
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189
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ATR and ATRIP are recruited to herpes simplex virus type 1 replication compartments even though ATR signaling is disabled. J Virol 2010; 84:12152-64. [PMID: 20861269 DOI: 10.1128/jvi.01643-10] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although the herpes simplex virus type 1 (HSV-1) genome might be expected to induce a DNA damage response, the ATR kinase is not activated in infected cells. We previously proposed that spatial uncoupling of ATR from its interaction partner, ATRIP, could be the basis for inactivation of the ATR kinase in infected cells; however, we now show that ATR and ATRIP are in fact both recruited to HSV-1 replication compartments and can be coimmunoprecipitated from infected-cell lysates. ATRIP and replication protein A (RPA) are recruited to the earliest detectable prereplicative sites, stage II microfoci. In a normal cellular DNA damage response, ATR/ATRIP are recruited to stretches of RPA-coated single-stranded DNA in an RPA- and kinase-dependent manner, resulting in the phosphorylation of RPA by ATR in damage foci. In contrast, in HSV-1-infected cells, RPA is not phosphorylated, and endogenous phosphorylated RPA is excluded from stage II microfoci; in addition, the recruitment of ATR/ATRIP is independent of RPA and the kinase activity of ATR. Furthermore, we show that ATR/ATRIP play a beneficial role in viral gene expression and virus production. Although ICP0 has been shown to be important for partial inactivation of other cellular DNA repair pathways, we show that ICP0 is not responsible for the inactivation of ATR signaling and, furthermore, that neither ATR nor ATRIP is a target of ICP0 degradation. Thus, ATR and ATRIP may function outside the context of the canonical ATR damage signaling pathway during HSV-1 infection to participate in the viral life cycle.
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190
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Ishikawa T, Kamei Y, Otozai S, Kim J, Sato A, Kuwahara Y, Tanaka M, Deguchi T, Inohara H, Tsujimura T, Todo T. High-resolution melting curve analysis for rapid detection of mutations in a Medaka TILLING library. BMC Mol Biol 2010; 11:70. [PMID: 20840787 PMCID: PMC2949603 DOI: 10.1186/1471-2199-11-70] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Accepted: 09/15/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND During the last two decades, DNA sequencing has led to the identification of numerous genes in key species; however, in most cases, their functions are still unknown. In this situation, reverse genetics is the most suitable method to assign function to a gene. TILLING (Targeting Induced Local Lesions IN Genomes) is a reverse-genetic strategy that combines random chemical mutagenesis with high-throughput discovery of the induced mutations in target genes. The method has been applied to a variety of plant and animal species. Screening of the induced mutations is the most important step in TILLING. Currently, direct sequencing or nuclease-mediated screening of heteroduplexes is widely used for detection of mutations in TILLING. Both methods are useful, but the costs are substantial and turnaround times are relatively long. Thus, there is a need for an alternative method that is of higher throughput and more cost effective. RESULTS In this study, we developed a high resolution melting (HRM) assay and evaluated its effectiveness for screening ENU-induced mutations in a medaka TILLING library. We had previously screened mutations in the p53 gene by direct sequencing. Therefore, we first tested the efficiency of the HRM assay by screening mutations in p53, which indicated that the HRM assay is as useful as direct sequencing. Next, we screened mutations in the atr and atm genes with the HRM assay. Nonsense mutations were identified in each gene, and the phenotypes of these nonsense mutants confirmed their loss-of-function nature. CONCLUSIONS These results demonstrate that the HRM assay is useful for screening mutations in TILLING. Furthermore, the phenotype of the obtained mutants indicates that medaka is an excellent animal model for investigating genome stability and gene function, especially when combined with TILLING.
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Affiliation(s)
- Tomoko Ishikawa
- Department of Radiation Biology and Medical Genetics, Graduate School of Medicine, Osaka University, B4, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
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191
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Takai H, Xie Y, de Lange T, Pavletich NP. Tel2 structure and function in the Hsp90-dependent maturation of mTOR and ATR complexes. Genes Dev 2010; 24:2019-30. [PMID: 20801936 DOI: 10.1101/gad.1956410] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We reported previously that the stability of all mammalian phosphatidylinositol 3-kinase-related protein kinases (PIKKs) depends on their interaction with Tel2, the ortholog of yeast Tel2 and Caenorhabditis elegans Clk-2. Here we provide evidence that Tel2 acts with Hsp90 in the maturation of PIKK complexes. Quantitative immunoblotting showed that the abundance of Tel2 is low compared with the PIKKs, and Tel2 preferentially bound newly synthesized ATM, ATR, mTOR, and DNA-PKcs. Tel2 complexes contained, in addition to Tti1-Tti2, the Hsp90 chaperone, and inhibition of Hsp90 interfered with the interaction of Tel2 with the PIKKs. Analysis of in vivo labeled nascent protein complexes showed that Tel2 and Hsp90 mediate the formation of the mTOR TORC1 and TORC2 complexes and the association of ATR with ATRIP. The structure of yeast Tel2, reported here, shows that Tel2 consists of HEAT-like helical repeats that assemble into two separate α-solenoids. Through mutagenesis, we identify a surface patch of conserved residues involved in binding to the Tti1-Tti2 complex in vitro. In vivo, mutation of this conserved patch affects cell growth, levels of PIKKs, and ATM/ATR-mediated checkpoint signaling, highlighting the importance of Tti1-Tti2 binding to the function of Tel2. Taken together, our data suggest that the Tel2-Tti1-Tti2 complex is a PIKK-specific cochaperone for Hsp90.
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Affiliation(s)
- Hiroyuki Takai
- Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, New York 10065, USA
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192
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Gao LB, Pan XM, Sun H, Wang X, Rao L, Li LJ, Liang WB, Lv ML, Yang WZ, Zhang L. The association between ATM D1853N polymorphism and breast cancer susceptibility: a meta-analysis. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2010; 29:117. [PMID: 20799949 PMCID: PMC2936337 DOI: 10.1186/1756-9966-29-117] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/14/2010] [Accepted: 08/27/2010] [Indexed: 01/09/2023]
Abstract
Background Emerging evidence suggests that ataxia telangiectasia-mutated (ATM) is involved in numerous damage repair signaling pathways and cell-cycle checkpoints. Heterozygous carriers of ATM-mutations have an increased risk for the development of breast cancer. The purpose of this study is to evaluate the association between ATM exon39 5557G > A (D1853N, rs1801516) polymorphism and breast cancer susceptibility with the use of a meta-analysis. Methods By searching PubMed and Embase databases, a total of 9 epidemiological studies with 4,191 cases and 3,780 controls were identified. Crude odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) for ATM D1853N polymorphism and breast cancer risk were calculated using fixed- or random-effects model based on the degree of heterogeneity among studies. Results No significant association between the ATM D1853N polymorphism and breast cancer risk was observed in overall analysis (GA versus GG: OR = 1.18; 95% CI, 0.90-1.53; AA versus GG: OR = 0.77; 95% CI, 0.58-1.03; dominant model: OR = 1.16; 95% CI, 0.89-1.51; and recessive model: OR = 0.78; 95% CI, 0.59-1.04, respectively). Conclusion Our results indicate that ATM D1853N polymorphism is not a risk factor for developing breast cancer.
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Affiliation(s)
- Lin-Bo Gao
- Laboratory of Molecular Translational Medicine, West China Second University Hospital, Sichuan University, Chengdu, Sichuan, China
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193
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Mutational analysis of the C-terminal FATC domain of Saccharomyces cerevisiae Tra1. Curr Genet 2010; 56:447-65. [PMID: 20635087 PMCID: PMC2943577 DOI: 10.1007/s00294-010-0313-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Revised: 06/25/2010] [Accepted: 06/29/2010] [Indexed: 01/22/2023]
Abstract
Tra1 is a component of the Saccharomyces cerevisiae SAGA and NuA4 complexes and a member of the PIKK family, which contain a C-terminal phosphatidylinositol 3-kinase-like (PI3K) domain followed by a 35-residue FATC domain. Single residue changes of L3733A and F3744A, within the FATC domain, resulted in transcriptional changes and phenotypes that were similar but not identical to those caused by mutations in the PI3K domain or deletions of other SAGA or NuA4 components. The distinct nature of the FATC mutations was also apparent from the additive effect of tra1-L3733A with SAGA, NuA4, and tra1 PI3K domain mutations. Tra1-L3733A associates with SAGA and NuA4 components and with the Gal4 activation domain, to the same extent as wild-type Tra1; however, steady-state levels of Tra1-L3733A were reduced. We suggest that decreased stability of Tra1-L3733A accounts for the phenotypes since intragenic suppressors of tra1-L3733A restored Tra1 levels, and reducing wild-type Tra1 led to comparable growth defects. Also supporting a key role for the FATC domain in the structure/function of Tra1, addition of a C-terminal glycine residue resulted in decreased association with Spt7 and Esa1, and loss of cellular viability. These findings demonstrate the regulatory potential of mechanisms targeting the FATC domains of PIKK proteins.
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194
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Vogt PK, Hart JR, Gymnopoulos M, Jiang H, Kang S, Bader AG, Zhao L, Denley A. Phosphatidylinositol 3-kinase: the oncoprotein. Curr Top Microbiol Immunol 2010. [PMID: 20582532 DOI: 10.1007/82-2010-80] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The catalytic and regulatory subunits of class I phosphoinositide 3-kinase (PI3K) have oncogenic potential. The catalytic subunit p110α and the regulatory subunit p85 undergo cancer-specific gain-of-function mutations that lead to enhanced enzymatic activity, ability to signal constitutively, and oncogenicity. The β, γ, and δ isoforms of p110 are cell-transforming as overexpressed wild-type proteins. Class I PI3Ks have the unique ability to generate phosphoinositide 3,4,5 trisphosphate (PIP(3)). Class II and class III PI3Ks lack this ability. Genetic and cell biological evidence suggests that PIP(3) is essential for PI3K-mediated oncogenicity, explaining why class II and class III enzymes have not been linked to cancer. Mutational analysis reveals the existence of at least two distinct molecular mechanisms for the gain of function seen with cancer-specific mutations in p110α; one causing independence from upstream receptor tyrosine kinases, the other inducing independence from Ras. An essential component of the oncogenic signal that is initiated by PI3K is the TOR (target of rapamycin) kinase. TOR is an integrator of growth and of metabolic inputs. In complex with the raptor protein (TORC1), it controls cap-dependent translation, and this function is essential for PI3K-initiated oncogenesis.
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Affiliation(s)
- Peter K Vogt
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
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195
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Expansion of the target of rapamycin (TOR) kinase family and function in Leishmania shows that TOR3 is required for acidocalcisome biogenesis and animal infectivity. Proc Natl Acad Sci U S A 2010; 107:11965-70. [PMID: 20551225 DOI: 10.1073/pnas.1004599107] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Target of rapamycin (TOR) kinases are key regulators of cell growth, proliferation, and structure in eukaryotes, processes that are highly coordinated during the infectious cycle of eukaryotic pathogens. Database mining revealed three TOR kinases in the trypanosomatid parasite Leishmania major, as defined by homology to the phosphoinositide 3-kinase-related kinase (PIKK) family and a signature conserved FKBP12/rapamycin-binding domain. Consistent with the essential roles of TOR complexes in other organisms, we were unable to generate null TOR1 or TOR2 mutants in cultured L. major promastigotes. In contrast, tor3(-) null mutants were readily obtained; while exhibiting somewhat slower growth, tor3(-) maintained normal morphology, rapamycin sensitivity, and differentiation into the animal-infective metacyclic stage. Significantly, tor3(-) mutants were unable to survive or replicate in macrophages in vitro, or to induce pathology or establish infections in mice in vivo. The loss of virulence was associated with a defect in acidocalcisome formation, as this unique organelle was grossly altered in tor3- mutants and no longer accumulated polyphosphates. Correspondingly, tor3- mutants showed defects in osmoregulation and were sensitive to starvation for glucose but not amino acids, glucose being a limiting nutrient in the parasitophorous vacuole. Thus, in Leishmania, the TOR kinase family has expanded to encompass a unique role in AC function and biology, one that is essential for parasite survival in the mammalian infective stage. Given their important roles in cell survival and virulence, inhibition of TOR kinase function in trypanosomatids offers an attractive target for chemotherapy.
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196
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Izumi N, Yamashita A, Iwamatsu A, Kurata R, Nakamura H, Saari B, Hirano H, Anderson P, Ohno S. AAA+ proteins RUVBL1 and RUVBL2 coordinate PIKK activity and function in nonsense-mediated mRNA decay. Sci Signal 2010; 3:ra27. [PMID: 20371770 DOI: 10.1126/scisignal.2000468] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Phosphatidylinositol 3-kinase-related protein kinase (PIKK) family proteins play essential roles in DNA-based and RNA-based processes, such as the response to DNA damage, messenger RNA (mRNA) quality control, transcription, and translation, where they contribute to the maintenance of genome integrity and accurate gene expression. The adenosine triphosphatases associated with diverse cellular activities (AAA+) family proteins RuvB-like 1 (RUVBL1) and RUVBL2 are involved in various cellular processes, including transcription, RNA modification, DNA repair, and telomere maintenance. We show that RUVBL1 and RUVBL2 associate with each PIKK family member. We also show that RUVBL1 and RUVBL2 control PIKK abundance at least at the mRNA level. Knockdown of RUVBL1 or RUVBL2 decreased PIKK abundance and impaired PIKK-mediated signaling. Analysis of SMG-1, a PIKK family member involved in nonsense-mediated mRNA decay (NMD), revealed an essential role for RUVBL1 and RUVBL2 in NMD. RUVBL1 and RUVBL2 associated with SMG-1 and the messenger ribonucleoproteins in the cytoplasm and promoted the formation of mRNA surveillance complexes during NMD. Thus, RUVBL1 and RUVBL2 regulate PIKK functions on two different levels: They control the abundance of PIKKs, and they stimulate the formation of PIKK-containing molecular complexes, such as those involved in NMD.
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Affiliation(s)
- Natsuko Izumi
- Department of Molecular Biology, Yokohama City University School of Medicine, Yokohama, Japan
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197
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Deng Q, Sheng L, Su D, Zhang L, Liu P, Lu K, Ma S. Genetic polymorphisms in ATM, ERCC1, APE1 and iASPP genes and lung cancer risk in a population of southeast China. Med Oncol 2010; 28:667-72. [PMID: 20354815 DOI: 10.1007/s12032-010-9507-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2010] [Accepted: 03/17/2010] [Indexed: 11/29/2022]
Abstract
Polymorphisms in DNA repair and apoptosis genes are suspected to alter the individual susceptibility to develop lung cancer. We investigated the relationship between polymorphisms in ATM (A60G), ERCC1 (Asn118Asn), APE1 (Asn148Glu) and iASPP (A67T) and the risk of developing lung cancer. A case-control study was conducted with 315 patients with lung cancer and 315 cancer-free controls, matched on age and sex. Genotypes were detected using the ABI 7500 real-time PCR system. The T/T homozygote in ERCC1 (Asn118Asn) was correlated with a strong statistically significant increased risk of developing lung cancer (adjusted OR=2.44; 95% CI=1.13-5.28; P=0.023), especially lung adenocarcinoma (adjusted OR=3.18) and small cell lung cancer (adjusted OR=6.08). For iASPP (A67T), smokers with at least one T allele (A/T+T/T) were more likely to develop lung cancer (95% CI, 1.07-2.84, P=0.026). Subjects carrying the G allele in APE1 (Asn148Glu) had a decreased risk of lung cancer (P<0.05), which showing a protective effect. Our results suggest that polymorphism Asn118Asn in ERCC1, A67T in iASPP and Asn148Glu in APE1 may associated with early onset of lung cancer as well as some specific subtype of lung cancer. Detection of these biomarkers may be helpful for screening this high-risk population for primary preventing.
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Affiliation(s)
- Qinghua Deng
- Department of Radiation Oncology, Zhejiang Cancer Hospital, 38 Banshan Road, Hangzhou, 310022, China
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198
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Workman P, Clarke PA, Raynaud FI, van Montfort RLM. Drugging the PI3 kinome: from chemical tools to drugs in the clinic. Cancer Res 2010; 70:2146-57. [PMID: 20179189 PMCID: PMC3242038 DOI: 10.1158/0008-5472.can-09-4355] [Citation(s) in RCA: 226] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The phosphatidylinositide 3-kinase (PI3K) pathway is very commonly activated in a wide range of human cancers and is a major driving force in oncogenesis. One of the class I lipid kinase members of the PI3K family, p110alpha, is probably the most commonly mutated kinase in the human genome. Alongside genetic, molecular biological, and biochemical studies, chemical inhibitors have been extremely helpful tools in understanding the role of PI3K enzymes in signal transduction and downstream physiological and pathological processes, and also in validating PI3Ks as therapeutic targets. Although they have been valuable in the past, the early and still frequently employed inhibitors, wortmannin and LY294002, have significant limitations as chemical tools. Here, we discuss the case history of the discovery and properties of an increasingly used chemical probe, the pan-class I PI3K and mammalian target of rapamycin (mTOR) inhibitor PI-103 (a pyridofuropyrimidine), and its very recent evolution into the thienopyrimidine drug GDC-0941, which exhibits excellent oral anticancer activity in preclinical models and is now undergoing phase I clinical trials in cancer patients. We also illustrate the impact of structural biology on the design of PI3K inhibitors and on the interpretation of their effects. The challenges and outlook for drugging the PI3 kinome are discussed in the more general context of the role of structural biology and chemical biology in innovative drug discovery.
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Affiliation(s)
- Paul Workman
- Cancer Research UK Centre for Cancer Therapeutics, Section of Cancer Therapeutics, The Institute of Cancer Research, Haddow Laboratories, Sutton, Surrey, United Kingdom.
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199
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Nicholson P, Yepiskoposyan H, Metze S, Zamudio Orozco R, Kleinschmidt N, Mühlemann O. Nonsense-mediated mRNA decay in human cells: mechanistic insights, functions beyond quality control and the double-life of NMD factors. Cell Mol Life Sci 2010; 67:677-700. [PMID: 19859661 PMCID: PMC11115722 DOI: 10.1007/s00018-009-0177-1] [Citation(s) in RCA: 254] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 09/16/2009] [Accepted: 10/06/2009] [Indexed: 12/16/2022]
Abstract
Nonsense-mediated decay is well known by the lucid definition of being a RNA surveillance mechanism that ensures the speedy degradation of mRNAs containing premature translation termination codons. However, as we review here, NMD is far from being a simple quality control mechanism; it also regulates the stability of many wild-type transcripts. We summarise the abundance of research that has characterised each of the NMD factors and present a unified model for the recognition of NMD substrates. The contentious issue of how and where NMD occurs is also discussed, particularly with regard to P-bodies and SMG6-driven endonucleolytic degradation. In recent years, the discovery of additional functions played by several of the NMD factors has further complicated the picture. Therefore, we also review the reported roles of UPF1, SMG1 and SMG6 in other cellular processes.
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Affiliation(s)
- Pamela Nicholson
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland
| | - Hasmik Yepiskoposyan
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland
| | - Stefanie Metze
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland
| | - Rodolfo Zamudio Orozco
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland
| | - Nicole Kleinschmidt
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland
| | - Oliver Mühlemann
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland
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200
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Rajagopalan S, Moyle MW, Joosten I, Long EO. DNA-PKcs controls an endosomal signaling pathway for a proinflammatory response by natural killer cells. Sci Signal 2010; 3:ra14. [PMID: 20179272 DOI: 10.1126/scisignal.2000467] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Endosomes are emerging as specialized signaling compartments that endow receptors with distinct signaling properties. The diversity of endosomal signaling pathways and their contribution to various biological responses is still unclear. CD158d, which is also known as the killer cell immunoglobulin-like receptor (KIR) 2DL4 (KIR2DL4), is an endosome-resident receptor in natural killer (NK) cells that stimulates the release of a unique set of proinflammatory and proangiogenic mediators in response to soluble human leukocyte antigen G (HLA-G). Here, we identified the CD158d signaling cascade. In response to soluble agonist antibody or soluble HLA-G, signaling by CD158d was dependent on the activation of nuclear factor kappaB (NF-kappaB) and the serine-threonine kinase Akt. CD158d associated with the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), promoted the recruitment of Akt to endosomes, and stimulated the DNA-PKcs-dependent phosphorylation of Akt. The sequential requirement for DNA-PKcs, Akt, and NF-kappaB in signaling by CD158d delineates a previously uncharacterized endosomal signaling pathway for a proinflammatory response in NK cells.
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Affiliation(s)
- Sumati Rajagopalan
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.
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