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Martin F. Lavin - One of the best experts on this subject based on the ideXlab platform.
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the spectrum of atm gene mutations in iranian patients with Ataxia Telangiectasia
Authorea Preprints, 2020Co-Authors: Parisa Amirifar, Martin F. Lavin, Mohammad Reza Ranjouri, Reza Yazdani, Salar Pashangzadeh, Tannaz Moeini Shad, Mahya Mehrmohamadi, Fereshte Salami, Samaneh DelavariAbstract:Abstract Background: Ataxia-Telangiectasia (A-T) is a rare genetic disorder characterized by a distinct range of clinical manifestations, including progressive Ataxia, immunodeficiency, and radiosensitivity. Methods: Clinical data, laboratory results, and genetic data were collected from forty-three A-T patients. Whole exome sequencing and Sanger sequencing were done for the patients clinically diagnosed as suffering from A-T. Based on the phenotype severity of the disease, patients were divided into severe and mild sub-groups. Results: The median (IQR) age of diagnosis in this cohort was 5 (3-7) years and various types of clinical manifestations, including fever (p= 0.005), lower respiratory tract infection (p= 0.033), diarrhea (p= 0.014), and hepatosplenomegaly (p= 0.032) were significantly higher amongst patients diagnosed with the severe phenotype. Our results showed a strong correlation between phenotype severity and mutation type. The chance of having severe phenotype in patients who have severe mutations, including frameshift and nonsense, was 7.3 times higher compared to patients who were categorized in the mild genotype group (odds ratio= 7.3, p= 0.006). Thirty-four types of mutations including 9 novel mutations, were observed in our study. Conclusion: Molecular analysis provides the opportunity for accurate diagnosis and timely management in A-T patients with chronic progressive disease, especially infections and the risk of malignancies. This study characterizes for the first time, the broad spectrum of mutations and phenotypes in Iranian A-T patients which are required for carrier detection and reducing the burden of disease in future using the patients’ families and for the public health care system. Keywords: Ataxia-Telangiectasia (A-T), ATM, Whole-exome sequencing, Class switching recombination (CSR), phenotype severity.
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Radioresistant malignant myoepithelioma of the breast with high level of Ataxia Telangiectasia mutated protein
Journal of Medical Imaging and Radiation Oncology, 2009Co-Authors: Zhiming Fang, Vm Marjoniemi, Sergei Kozlov, Peter H. Graham, John H. Kearsley, Hongmin Chen, Martin F. Lavin, Raymond A. ClarkeAbstract:Malignant myoepithelioma of the breast (MMB) is a rare and often aggressive disease with poor prognosis. Little is known regarding its optimal treatment and progression. We describe the clinical history of a woman following excision of a benign adenomyoepithelioma which recurred years later as a radioresistant malignant myoepithelioma with high levels of Ataxia Telangiectasia mutated protein and mutant p53 (Cys135Phe). MMB requires close follow-up and aggressive treatment. If adjuvant radiotherapy is adopted to improve local control, minimal postoperative delay and higher doses than for standard post-mastectomy radiation are recommended.
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current and potential therapeutic strategies for the treatment of Ataxia Telangiectasia
British Medical Bulletin, 2007Co-Authors: Martin F. Lavin, Nuri Gueven, Stephen Bottle, Richard A GattiAbstract:Ataxia-Telangiectasia (A-T) is a rare autosomal recessive genetic disorder characterized by progressive neurodegeneration, a high risk of cancer and immunodeficiency. These patients are also hypersensitive to radiotherapy. The gene product defective in this syndrome, ATM (Ataxia-Telangiectasia mutated), normally recognizes DNA damage and signal to the DNA repair machinery and the cell cycle checkpoints to minimize the risk of genetic damage. No curative strategy for this disease exists. Treatment has focused on slowing the progress of the neurodegeneration; devising approaches for the treatment of tumours while minimizing side effects and treatment with immunoglobulin for the immunodeficiency. The most debilitating feature of this disorder is the progressive neurodegeneration due to loss of Purkinje cells in the cerebellum and malfunction of other neuronal cells. Correcting for the loss of Purkinje cells is technically very difficult and would require transplantation of embryonic stem cells. However, since it seems likely that oxidative stress may contribute to the neurodegeneration in A-T, potential therapies based on the use of antioxidants offer some hope. We describe the natural course of disease, some supportive therapeutic approaches already in use and those with potential based on our knowledge of molecular and cellular characteristics of this disorder.
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atp activates Ataxia Telangiectasia mutated atm in vitro importance of autophosphorylation
Journal of Biological Chemistry, 2003Co-Authors: Sergei Kozlov, Jonathan Ramsay, Katherine Keating, Nuri Gueven, Martin F. LavinAbstract:Ataxia-Telangiectasia Mutated (ATM), mutated in the human disorder Ataxia-Telangiectasia, is rapidly activated by DNA double strand breaks. The mechanism of activation remains unresolved, and it is uncertain whether autophosphorylation contributes to activation. We describe an in vitro immunoprecipitation system demonstrating activation of ATM kinase from unirradiated extracts by preincubation with ATP. Activation is both time- and ATP concentration-dependent, other nucleotides fail to activate ATM, and DNA is not required. ATP activation is specific for ATM since it is not observed with kinase-dead ATM, it requires Mn2+, and it is inhibited by wortmannin. Exposure of activated ATM to phosphatase abrogates activity, and repeat cycles of ATP and phosphatase treatment reveal a requirement for autophosphorylation in the activation process. Phosphopeptide mapping revealed similarities between the patterns of autophosphorylation for irradiated and ATP-treated ATM. Caffeine inhibited ATM kinase activity for substrates but did not interfere with ATM autophosphorylation. ATP failed to activate either A-T and rad3-related protein (ATR) or DNA-dependent protein kinase under these conditions, supporting the specificity for ATM. These data demonstrate that ATP can specifically induce activation of ATM by a mechanism involving autophosphorylation. The relationship of this activation to DNA damage activation remains unclear but represents a useful model for understanding in vivo activation.
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Ataxia Telangiectasia mutated gene product inhibits dna damage induced apoptosis via ceramide synthase
Journal of Biological Chemistry, 1999Co-Authors: Wen-chieh Liao, Roger S Persaud, Maureen Mcloughlin, Desiree Ehleiter, Magtouf Gatei, Richard Kolesnick, Adriana Haimovitzfriedman, Martin F. Lavin, Ning Zhang, Zvi FuksAbstract:Abstract DNA double-stranded breaks (dsb) activate surveillance systems that identify DNA damage and either initiate repair or signal cell death. Failure of cells to undergo appropriate death in response to DNA damage leads to misrepair, mutations, and neoplastic transformation. Pathways linking DNA dsb to reproductive or apoptotic death are virtually unknown. Here we report that metabolic incorporation of 125I-labeled 5-iodo-2′deoxyuridine, which produces DNA dsb, signaled de novo ceramide synthesis by post-translational activation of ceramide synthase (CS) and apoptosis. CS activation was obligatory, since fumonisin B1, a fungal pathogen that acts as a specific CS inhibitor, abrogated DNA damage-induced death. X-irradiation yielded similar results. Furthermore, inhibition of apoptosis using the peptide caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone did not affect CS activation, indicating this event is not a consequence of induction of apoptosis. ATM, the gene mutated in Ataxia Telangiectasia, is a member of the phosphatidylinositol 3-kinase family that constitutes the DNA damage surveillance/repair system. Epstein-Barr virus-immortalized B cell lines from six Ataxia Telangiectasia patients with different mutations exhibited radiation-induced CS activation, ceramide generation, and apoptosis, whereas three lines from normal patients failed to manifest these responses. Stable transfection of wild type ATM cDNA reversed these events, whereas antisense inactivation of Ataxia Telangiectasia-mutated gene product in normal B cells conferred the Ataxia Telangiectasia phenotype. We propose that one of the functions of Ataxia Telangiectasia-mutated gene product is to constrain activation of CS, thereby regulating DNA damage-induced apoptosis.
Luciana Chessa - One of the best experts on this subject based on the ideXlab platform.
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Activation of NRF2 by dexamethasone in Ataxia Telangiectasia cells involves KEAP1 inhibition but not the inhibition of p38
2019Co-Authors: Sara Biagiotti, Luciana Chessa, Marzia Bianchi, Luigia Rossi, Mauro MagnaniAbstract:Oxidative stress has been shown to play a crucial role in the pathophysiology of the neurodegenerative disease Ataxia Telangiectasia. We have recently demonstrated that Dexamethasone treatment is able to counteract the oxidative state by promoting nuclear factor erythroid 2-related factor 2 (NRF2) nuclear accumulation. However, substantial gaps remain in our knowledge of the underlying molecular mechanism(s) according to which Dexamethasone acts as an NRF2 inducer. Herein we investigate the possible effects of the drug on the main NRF2 activation pathways by initially focusing on key kinases known to differently affect NRF2 activation. Neither AKT nor ERK1/2, known to be NRF2-activating kinases, were found to be activated upon Dexamethasone treatment, thus excluding their involvement in the transcription factor nuclear shift. Likewise, GSK3 inactivating kinase was not inhibited, thus ruling out its role in NRF2 activation. On the other hand, p38 MAPK, another NRF2-inhibitory kinase, was indeed switched-off in Ataxia Telangiectasia cells by Dexamethasone-mediated induction of DUSP1 phosphatase, and therefore it appeared that it might account for NRF2 triggering. However, this mechanism was excluded by the use of a selective p38 inhibitor, which failed to cause a significant NRF2 nuclear shift and target gene induction. Finally, dexamethasone effects on the classical oxidative pathway orchestrated by KEAP1 were addressed. Dexamethasone was found to decrease the expression of the inhibitor KEAP1 at both mRNA and protein levels and to induce the shift from the reduced to the oxidized form of KEAP1, thus favouring NRF2 translocation into the nucleus. Furthermore, preliminary data revealed very low levels of the negative regulator Fyn in Ataxia Telangiectasia cells, which might account for the prolonged NRF2-activated gene expression.
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dexamethasone partially rescues Ataxia Telangiectasia mutated atm deficiency in Ataxia Telangiectasia by promoting a shortened protein variant retaining kinase activity
Journal of Biological Chemistry, 2012Co-Authors: Michele Menotta, Luciana Chessa, Sara Biagiotti, Marzia Bianchi, Mauro MagnaniAbstract:Abstract Ataxia Telangiectasia (AT) is a rare genetic disease still incurable, resulting from biallelic mutations in the Ataxia Telangiectasia-Mutated (ATM) gene. Recently, short-term treatment with glucocorticoid analogues improved neurological symptoms characteristic of this syndrome. Nevertheless, the molecular mechanism involved in glucocorticoid action in AT patients is not yet known. Here we describe, for the first time in mammalian cells, a short direct repeat-mediated non-canonical splicing event induced by dexamethasone, which leads to the skipping of mutations upstream of nucleotide residue 8450 of ATM coding sequence. The resulting transcript provides an alternative ORF translated in a new ATM variant with the complete kinase domain. This miniATM variant was also highlighted in lymphoblastoid cell lines from AT patients and resulted to be likely active. In conclusion, dexamethasone treatment may partly restore ATM activity in Ataxia Telangiectasia cells by a new molecular mechanism that overcomes most of the mutations so far described within this gene.
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dexamethasone partially rescues Ataxia Telangiectasia mutated atm deficiency in Ataxia Telangiectasia by promoting a shortened protein variant retaining kinase activity
Journal of Biological Chemistry, 2012Co-Authors: Michele Menotta, Luciana Chessa, Sara Biagiotti, Marzia Bianchi, Mauro MagnaniAbstract:Ataxia Telangiectasia (AT) is a rare genetic disease, still incurable, resulting from biallelic mutations in the Ataxia Telangiectasia-mutated (ATM) gene. Recently, short term treatment with glucocorticoid analogues improved neurological symptoms characteristic of this syndrome. Nevertheless, the molecular mechanism involved in glucocorticoid action in AT patients is not yet known. Here we describe, for the first time in mammalian cells, a short direct repeat-mediated noncanonical splicing event induced by dexamethasone, which leads to the skipping of mutations upstream of nucleotide residue 8450 of ATM coding sequence. The resulting transcript provides an alternative ORF translated in a new ATM variant with the complete kinase domain. This miniATM variant was also highlighted in lymphoblastoid cell lines from AT patients and was shown to be likely active. In conclusion, dexamethasone treatment may partly restore ATM activity in Ataxia Telangiectasia cells by a new molecular mechanism that overcomes most of the mutations so far described within this gene.
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The Ataxia-Telangiectasia gene product, a constitutively expressed nuclear protein that is not up-regulated following genome damage
Proceedings of the National Academy of Sciences of the United States of America, 1997Co-Authors: Kevin D. Brown, Luciana Chessa, Yosef Shiloh, Yael Ziv, Sunanda N. Sadanandan, Francis S. Collins, Danilo A. TagleAbstract:The product of the Ataxia-Telangiectasia gene (ATM) was identified by using an antiserum developed to a peptide corresponding to the deduced amino acid sequence. The ATM protein is a single, high-molecular weight protein predominantly confined to the nucleus of human fibroblasts, but is present in both nuclear and microsomal fractions from human lymphoblast cells and peripheral blood lymphocytes. ATM protein levels and localization remain constant throughout all stages of the cell cycle. Truncated ATM protein was not detected in lymphoblasts from Ataxia-Telangiectasia patients homozygous for mutations leading to premature protein termination. Exposure of normal human cells to γ-irradiation and the radiomimetic drug neocarzinostatin had no effect on ATM protein levels, in contrast to a noted rise in p53 levels over the same time interval. These findings are consistent with a role for the ATM protein in ensuring the fidelity of DNA repair and cell cycle regulation following genome damage.
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Predominance of Null Mutations in Ataxia-Telangiectasia
Human molecular genetics, 1996Co-Authors: Shlomit Gilad, Luciana Chessa, Yael Ziv, Rami Khosravi, Dganit Shkedy, Tamar Uziel, Kinneret Savitsky, Galit Rotman, Sara Smith, Timothy J. JorgensenAbstract:Ataxia-Telangiectasia (A-T) is an autosomal recessive disorder involving cerebellar degeneration, immunodeficiency, chromosomal instability, radiosensitivity and cancer predisposition. The responsible gene, ATM, was recently identified by positional cloning and found to encode a putative 350 kDa protein with a PI 3-kinase-like domain, presumably involved in mediating cell cycle arrest in response to radiation-induced DNA damage. The nature and location of A-T mutations should provide insight into the function of the ATM protein and the molecular basis of this pleiotropic disease. Of 44 A-T mutations identified by us to date, 39 (89%) are expected to inactivate the ATM protein by truncating it, by abolishing correct initiation or termination of translation, or by deleting large segments. Additional mutations are four smaller in-frame deletions and insertions, and one substitution of a highly conserved amino acid at the PI 3-kinase domain. The emerging profile of mutations causing A-T is thus dominated by those expected to completely inactivate the ATM protein. ATM mutations with milder effects may result in phenotypes related, but not identical, to A-T.
Mauro Magnani - One of the best experts on this subject based on the ideXlab platform.
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Activation of NRF2 by dexamethasone in Ataxia Telangiectasia cells involves KEAP1 inhibition but not the inhibition of p38
2019Co-Authors: Sara Biagiotti, Luciana Chessa, Marzia Bianchi, Luigia Rossi, Mauro MagnaniAbstract:Oxidative stress has been shown to play a crucial role in the pathophysiology of the neurodegenerative disease Ataxia Telangiectasia. We have recently demonstrated that Dexamethasone treatment is able to counteract the oxidative state by promoting nuclear factor erythroid 2-related factor 2 (NRF2) nuclear accumulation. However, substantial gaps remain in our knowledge of the underlying molecular mechanism(s) according to which Dexamethasone acts as an NRF2 inducer. Herein we investigate the possible effects of the drug on the main NRF2 activation pathways by initially focusing on key kinases known to differently affect NRF2 activation. Neither AKT nor ERK1/2, known to be NRF2-activating kinases, were found to be activated upon Dexamethasone treatment, thus excluding their involvement in the transcription factor nuclear shift. Likewise, GSK3 inactivating kinase was not inhibited, thus ruling out its role in NRF2 activation. On the other hand, p38 MAPK, another NRF2-inhibitory kinase, was indeed switched-off in Ataxia Telangiectasia cells by Dexamethasone-mediated induction of DUSP1 phosphatase, and therefore it appeared that it might account for NRF2 triggering. However, this mechanism was excluded by the use of a selective p38 inhibitor, which failed to cause a significant NRF2 nuclear shift and target gene induction. Finally, dexamethasone effects on the classical oxidative pathway orchestrated by KEAP1 were addressed. Dexamethasone was found to decrease the expression of the inhibitor KEAP1 at both mRNA and protein levels and to induce the shift from the reduced to the oxidized form of KEAP1, thus favouring NRF2 translocation into the nucleus. Furthermore, preliminary data revealed very low levels of the negative regulator Fyn in Ataxia Telangiectasia cells, which might account for the prolonged NRF2-activated gene expression.
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dexamethasone partially rescues Ataxia Telangiectasia mutated atm deficiency in Ataxia Telangiectasia by promoting a shortened protein variant retaining kinase activity
Journal of Biological Chemistry, 2012Co-Authors: Michele Menotta, Luciana Chessa, Sara Biagiotti, Marzia Bianchi, Mauro MagnaniAbstract:Abstract Ataxia Telangiectasia (AT) is a rare genetic disease still incurable, resulting from biallelic mutations in the Ataxia Telangiectasia-Mutated (ATM) gene. Recently, short-term treatment with glucocorticoid analogues improved neurological symptoms characteristic of this syndrome. Nevertheless, the molecular mechanism involved in glucocorticoid action in AT patients is not yet known. Here we describe, for the first time in mammalian cells, a short direct repeat-mediated non-canonical splicing event induced by dexamethasone, which leads to the skipping of mutations upstream of nucleotide residue 8450 of ATM coding sequence. The resulting transcript provides an alternative ORF translated in a new ATM variant with the complete kinase domain. This miniATM variant was also highlighted in lymphoblastoid cell lines from AT patients and resulted to be likely active. In conclusion, dexamethasone treatment may partly restore ATM activity in Ataxia Telangiectasia cells by a new molecular mechanism that overcomes most of the mutations so far described within this gene.
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dexamethasone partially rescues Ataxia Telangiectasia mutated atm deficiency in Ataxia Telangiectasia by promoting a shortened protein variant retaining kinase activity
Journal of Biological Chemistry, 2012Co-Authors: Michele Menotta, Luciana Chessa, Sara Biagiotti, Marzia Bianchi, Mauro MagnaniAbstract:Ataxia Telangiectasia (AT) is a rare genetic disease, still incurable, resulting from biallelic mutations in the Ataxia Telangiectasia-mutated (ATM) gene. Recently, short term treatment with glucocorticoid analogues improved neurological symptoms characteristic of this syndrome. Nevertheless, the molecular mechanism involved in glucocorticoid action in AT patients is not yet known. Here we describe, for the first time in mammalian cells, a short direct repeat-mediated noncanonical splicing event induced by dexamethasone, which leads to the skipping of mutations upstream of nucleotide residue 8450 of ATM coding sequence. The resulting transcript provides an alternative ORF translated in a new ATM variant with the complete kinase domain. This miniATM variant was also highlighted in lymphoblastoid cell lines from AT patients and was shown to be likely active. In conclusion, dexamethasone treatment may partly restore ATM activity in Ataxia Telangiectasia cells by a new molecular mechanism that overcomes most of the mutations so far described within this gene.
Karl Mechtler - One of the best experts on this subject based on the ideXlab platform.
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Quantitative Phosphoproteomics of the Ataxia Telangiectasia-Mutated (ATM) and Ataxia Telangiectasia-Mutated and Rad3-related (ATR) Dependent DNA Damage Response in
2016Co-Authors: Elisabeth Roitinger, Manuel Hofer, Peter Pichler, Maria Novatchkova, Jianhua Yang, Karl MechtlerAbstract:The reversible phosphorylation of proteins on serine, thre-onine, and tyrosine residues is an important biological regulatory mechanism. In the context of genome integrity, signaling cascades driven by phosphorylation are crucial for the coordination and regulation of DNA repair. The two serine/threonine protein kinases Ataxia Telangiectasia-mutated (ATM) and Ataxia Telangiectasia-mutated and Rad3-related (ATR) are key factors in this process, each specific for different kinds of DNA lesions. They are con-served across eukaryotes, mediating the activation of cell-cycle checkpoints, chromatin modifications, and reg-ulation of DNA repair proteins. We designed a novel mass spectrometry-based phosphoproteomics approach to study DNA damage repair in Arabidopsis thaliana. The protocol combines filter aided sample preparation, immo-bilized metal affinity chromatography, metal oxide affinity chromatography, and strong cation exchange chroma-tography for phosphopeptide generation, enrichment, and separation. Isobaric labeling employing iTRAQ (isobaric tags for relative and absolute quantitation) was used for profiling the phosphoproteome of atm atr double mutants and wild type plants under either regular growth condi-tions or challenged by irradiation. A total of 10,831 pro-teins were identified and 15,445 unique phosphopeptides were quantified, containing 134 up- and 38 down-regu-lated ATM/ATR dependent phosphopeptides. We identi-fied known and novel ATM/ATR targets such as LIG4 and MRE11 (needed for resistance against ionizing radiation), PIE1 and SDG26 (implicated in chromatin remodeling), PCNA1, WAPL, and PDS5 (implicated in DNA replication)
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quantitative phosphoproteomics of the Ataxia Telangiectasia mutated atm and Ataxia Telangiectasia mutated and rad3 related atr dependent dna damage response in arabidopsis thaliana
Molecular & Cellular Proteomics, 2015Co-Authors: Elisabeth Roitinger, Manuel Hofer, Peter Pichler, Peter Schlögelhofer, Thomas Kocher, Maria Novatchkova, Jianhua Yang, Karl MechtlerAbstract:The reversible phosphorylation of proteins on serine, threonine, and tyrosine residues is an important biological regulatory mechanism. In the context of genome integrity, signaling cascades driven by phosphorylation are crucial for the coordination and regulation of DNA repair. The two serine/threonine protein kinases Ataxia Telangiectasia-mutated (ATM) and Ataxia Telangiectasia-mutated and Rad3-related (ATR) are key factors in this process, each specific for different kinds of DNA lesions. They are conserved across eukaryotes, mediating the activation of cell-cycle checkpoints, chromatin modifications, and regulation of DNA repair proteins. We designed a novel mass spectrometry-based phosphoproteomics approach to study DNA damage repair in Arabidopsis thaliana. The protocol combines filter aided sample preparation, immobilized metal affinity chromatography, metal oxide affinity chromatography, and strong cation exchange chromatography for phosphopeptide generation, enrichment, and separation. Isobaric labeling employing iTRAQ (isobaric tags for relative and absolute quantitation) was used for profiling the phosphoproteome of atm atr double mutants and wild type plants under either regular growth conditions or challenged by irradiation. A total of 10,831 proteins were identified and 15,445 unique phosphopeptides were quantified, containing 134 up- and 38 down-regulated ATM/ATR dependent phosphopeptides. We identified known and novel ATM/ATR targets such as LIG4 and MRE11 (needed for resistance against ionizing radiation), PIE1 and SDG26 (implicated in chromatin remodeling), PCNA1, WAPL, and PDS5 (implicated in DNA replication), and ASK1 and HTA10 (involved in meiosis).
Zvi Fuks - One of the best experts on this subject based on the ideXlab platform.
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Ataxia Telangiectasia mutated gene product inhibits dna damage induced apoptosis via ceramide synthase
Journal of Biological Chemistry, 1999Co-Authors: Wen-chieh Liao, Roger S Persaud, Maureen Mcloughlin, Desiree Ehleiter, Magtouf Gatei, Richard Kolesnick, Adriana Haimovitzfriedman, Martin F. Lavin, Ning Zhang, Zvi FuksAbstract:Abstract DNA double-stranded breaks (dsb) activate surveillance systems that identify DNA damage and either initiate repair or signal cell death. Failure of cells to undergo appropriate death in response to DNA damage leads to misrepair, mutations, and neoplastic transformation. Pathways linking DNA dsb to reproductive or apoptotic death are virtually unknown. Here we report that metabolic incorporation of 125I-labeled 5-iodo-2′deoxyuridine, which produces DNA dsb, signaled de novo ceramide synthesis by post-translational activation of ceramide synthase (CS) and apoptosis. CS activation was obligatory, since fumonisin B1, a fungal pathogen that acts as a specific CS inhibitor, abrogated DNA damage-induced death. X-irradiation yielded similar results. Furthermore, inhibition of apoptosis using the peptide caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone did not affect CS activation, indicating this event is not a consequence of induction of apoptosis. ATM, the gene mutated in Ataxia Telangiectasia, is a member of the phosphatidylinositol 3-kinase family that constitutes the DNA damage surveillance/repair system. Epstein-Barr virus-immortalized B cell lines from six Ataxia Telangiectasia patients with different mutations exhibited radiation-induced CS activation, ceramide generation, and apoptosis, whereas three lines from normal patients failed to manifest these responses. Stable transfection of wild type ATM cDNA reversed these events, whereas antisense inactivation of Ataxia Telangiectasia-mutated gene product in normal B cells conferred the Ataxia Telangiectasia phenotype. We propose that one of the functions of Ataxia Telangiectasia-mutated gene product is to constrain activation of CS, thereby regulating DNA damage-induced apoptosis.
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Ataxia Telangiectasia mutated gene product inhibits dna damage induced apoptosis via ceramide synthase
Journal of Biological Chemistry, 1999Co-Authors: Wen-chieh Liao, Roger S Persaud, Maureen Mcloughlin, Desiree Ehleiter, Magtouf Gatei, Richard Kolesnick, Adriana Haimovitzfriedman, Martin F. Lavin, Ning Zhang, Zvi FuksAbstract:Abstract DNA double-stranded breaks (dsb) activate surveillance systems that identify DNA damage and either initiate repair or signal cell death. Failure of cells to undergo appropriate death in response to DNA damage leads to misrepair, mutations, and neoplastic transformation. Pathways linking DNA dsb to reproductive or apoptotic death are virtually unknown. Here we report that metabolic incorporation of 125I-labeled 5-iodo-2′deoxyuridine, which produces DNA dsb, signaled de novo ceramide synthesis by post-translational activation of ceramide synthase (CS) and apoptosis. CS activation was obligatory, since fumonisin B1, a fungal pathogen that acts as a specific CS inhibitor, abrogated DNA damage-induced death. X-irradiation yielded similar results. Furthermore, inhibition of apoptosis using the peptide caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone did not affect CS activation, indicating this event is not a consequence of induction of apoptosis. ATM, the gene mutated in Ataxia Telangiectasia, is a member of the phosphatidylinositol 3-kinase family that constitutes the DNA damage surveillance/repair system. Epstein-Barr virus-immortalized B cell lines from six Ataxia Telangiectasia patients with different mutations exhibited radiation-induced CS activation, ceramide generation, and apoptosis, whereas three lines from normal patients failed to manifest these responses. Stable transfection of wild type ATM cDNA reversed these events, whereas antisense inactivation of Ataxia Telangiectasia-mutated gene product in normal B cells conferred the Ataxia Telangiectasia phenotype. We propose that one of the functions of Ataxia Telangiectasia-mutated gene product is to constrain activation of CS, thereby regulating DNA damage-induced apoptosis.