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Aredia F, Czaplinski S, Fulda S, Scovassi AI. Molecular features of the cytotoxicity of an NHE inhibitor: Evidence of mitochondrial alterations, ROS overproduction and DNA damage. BMC Cancer 2016; 16:851. [PMID: 27816051 PMCID: PMC5097842 DOI: 10.1186/s12885-016-2878-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/24/2016] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND NH exchangers (NHEs) play a crucial role in regulating intra/extracellular pH, which is altered in cancer cells, and are therefore suitable targets to alter cancer cell metabolism in order to inhibit cell survival and proliferation. Among NHE inhibitors, amiloride family members are commonly used in clinical practice as diuretics; we focused on the amiloride HMA, reporting a net cytotoxic effect on a panel of human cancer cell lines; now we aim to provide new insights into the molecular events leading to cell death by HMA. METHODS Colon cancer cell lines were treated with HMA and analysed with: morphological and cellular assays for cell viability and death, and autophagy; biochemical approaches to evaluate mitochondrial function and ROS production; in situ detection of DNA damage; molecular tools to silence crucial autophagy/necroptosis factors. RESULTS HMA affects cellular morphology, alters mitochondrial structure and function, causes an increase in ROS, which is detrimental to DNA integrity, stimulates poly(ADP-ribose) synthesis, activates RIPK3-dependent death and triggers autophagy, which is unable to rescue cell survival. These features are hot points of an intricate network of processes, including necroptosis and autophagy, regulating the homeostasis between survival and death. CONCLUSION Our results allow the identification of multiple events leading to cell death in cancer cells treated with HMA. The here-defined intricate network activated by HMA could be instrumental to selectively target the key players of each pathway in the attempt to improve the global response to HMA. Our data could be the starting point for developing a newly designed targeted therapy.
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Affiliation(s)
- Francesca Aredia
- Istituto di Genetica Molecolare CNR, Via Abbiategrasso 207, 27100, Pavia, Italy.,Dipartimento di Biologia e Biotecnologie "L. Spallanzani", Università di Pavia, Via Ferrata 9, 27100, Pavia, Italy
| | - Sebastian Czaplinski
- Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Komturstrasse 3a, 60528, Frankfurt, Germany
| | - Simone Fulda
- Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Komturstrasse 3a, 60528, Frankfurt, Germany
| | - A Ivana Scovassi
- Istituto di Genetica Molecolare CNR, Via Abbiategrasso 207, 27100, Pavia, Italy.
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102
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Xia L, Wang XR, Wang XL, Liu SH, Ding XW, Chen GQ, Lu Y. A Novel Role for Pyruvate Kinase M2 as a Corepressor for P53 during the DNA Damage Response in Human Tumor Cells. J Biol Chem 2016; 291:26138-26150. [PMID: 27810895 DOI: 10.1074/jbc.m116.737056] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2016] [Revised: 10/17/2016] [Indexed: 01/07/2023] Open
Abstract
The pyruvate kinase (PK) is a rate-limiting glycolytic enzyme catalyzing the dephosphorylation of phosphoenolpyruvate to pyruvate, yielding one molecule of ATP. The M2 isoform of PK (PKM2) is predominantly expressed in normal proliferating cells and tumors, and both metabolic and non-metabolic activities for the enzyme in promoting tumor cell proliferation have been identified. However, the exact roles of PKM2 in tumor initiation, growth and maintenance are not yet fully understood. Using immunoprecipitation-coupled LC-MS/MS in MCF7 cells exposed to DNA-damaging agent, we report that the nuclear PKM2 interacts directly with P53 protein, a critical safeguard for genome stability. Specifically, PKM2 inhibits P53-dependent transactivation of the P21 gene by preventing P53 binding to the P21 promoter, leading to a nonstop G1 phase. As a result, PKM2 expression provides a growth advantage for tumor cells in the presence of a DNA damage stimulus. In addition, PKM2 interferes with phosphorylation of P53 at serine 15, known to stimulate P53 activity by the ATM serine/threonine kinase. These findings reveal a new role for PKM2 in modulating the DNA damage response and illustrate a novel mechanism of PKM2 participating in tumorigenesis.
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Affiliation(s)
- Li Xia
- From the Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Ministry of Education, Shanghai Jiao Tong University School of Medicine (SJTU-SM), Shanghai 200025, China and
| | - Xin-Ran Wang
- From the Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Ministry of Education, Shanghai Jiao Tong University School of Medicine (SJTU-SM), Shanghai 200025, China and
| | - Xiao-Ling Wang
- From the Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Ministry of Education, Shanghai Jiao Tong University School of Medicine (SJTU-SM), Shanghai 200025, China and
| | - Su-Hui Liu
- From the Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Ministry of Education, Shanghai Jiao Tong University School of Medicine (SJTU-SM), Shanghai 200025, China and
| | - Xiao-Wei Ding
- From the Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Ministry of Education, Shanghai Jiao Tong University School of Medicine (SJTU-SM), Shanghai 200025, China and
| | - Guo-Qiang Chen
- From the Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Ministry of Education, Shanghai Jiao Tong University School of Medicine (SJTU-SM), Shanghai 200025, China and .,the Institute of Health Sciences, Shanghai Institutes for Biological Sciences of Chinese Academy of Sciences and SJTU-SM, Shanghai 200025, China
| | - Ying Lu
- From the Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Ministry of Education, Shanghai Jiao Tong University School of Medicine (SJTU-SM), Shanghai 200025, China and
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103
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Li CH, Lim SH, Ryu HH, Moon KS, Jung TY, Jung S. Enhancement of radiosensitivity by inhibition of c-Jun N-terminal kinase activity in a Lewis lung carcinoma‑bearing subcutaneous tumor mouse model. Oncol Rep 2016; 36:3397-3404. [PMID: 27779695 DOI: 10.3892/or.2016.5204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 08/26/2016] [Indexed: 11/06/2022] Open
Abstract
Stereotactic radiosurgery has been recognized as an effective treatment approach for metastatic brain tumors. By increasing the sensitivity of the tumor to radiation and decreasing the marginal dose, it is possible to improve therapeutic efficacy and decrease side-effects. In radiation-induced cells, c-Jun N-terminal kinase (JNK) signaling mediates the phosphorylation of H2AX, which indicates DNA damage sensitivity and modulates the effect of radiation. Lewis lung cancer (LLC) and breast cancer (4T1) cells were irradiated with a Gamma Knife in cell culture tubes. To evaluate the relationship between radiosensitivity and JNK activity, clonogenic assay was performed. DNA damage response was estimated by γH2AX focus formation assay and apoptosis‑related protein levels were assessed by western blotting. The mice were subcutaneously inoculated with LLC cells, and irradiated concomitantly with JNK inhibitor treatment. The effect of the JNK inhibitor was investigated by tumor volumetry and immunohistochemistry. γH2AX expression, which mediates repair of radiation‑induced DNA damage, was reduced in the cancer cell group pretreated with the JNK inhibitor. This finding shows that JNK inhibition may increase the radiosensitivity in radiated lung and breast cancer cells. For the in vivo study, irradiated tumor growth was significantly delayed in the JNK inhibitor-treated mouse group. Blockade of JNK signaling decreased γH2AX expression and increased apoptosis in the radiation-induced cancer cells. JNK inhibitor may be useful for enhancing the radiosensitivity of lung and breast cancer cells and improving the treatment efficacy of radiosurgical approaches for metastatic brain tumors.
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Affiliation(s)
- Chun-Hao Li
- Brain Tumor Research Laboratory, Chonnam National University Research Institute of Medical Sciences, Chonnam National University Medical School and Chonnam National University Hwasun Hospital, Hwasun, Jeollanam-do 519-763, Republic of Korea
| | - Sa-Hoe Lim
- Brain Tumor Research Laboratory, Chonnam National University Research Institute of Medical Sciences, Chonnam National University Medical School and Chonnam National University Hwasun Hospital, Hwasun, Jeollanam-do 519-763, Republic of Korea
| | - Hyang-Hwa Ryu
- Brain Tumor Research Laboratory, Chonnam National University Research Institute of Medical Sciences, Chonnam National University Medical School and Chonnam National University Hwasun Hospital, Hwasun, Jeollanam-do 519-763, Republic of Korea
| | - Kyung-Sub Moon
- Department of Neurosurgery, Chonnam National University Medical School and Chonnam National University Hwasun Hospital, Hwasun, Jeollanam-do 519-763, Republic of Korea
| | - Tae-Young Jung
- Department of Neurosurgery, Chonnam National University Medical School and Chonnam National University Hwasun Hospital, Hwasun, Jeollanam-do 519-763, Republic of Korea
| | - Shin Jung
- Brain Tumor Research Laboratory, Chonnam National University Research Institute of Medical Sciences, Chonnam National University Medical School and Chonnam National University Hwasun Hospital, Hwasun, Jeollanam-do 519-763, Republic of Korea
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104
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Estrada-Bernal A, Chatterjee M, Haque SJ, Yang L, Morgan MA, Kotian S, Morrell D, Chakravarti A, Williams TM. MEK inhibitor GSK1120212-mediated radiosensitization of pancreatic cancer cells involves inhibition of DNA double-strand break repair pathways. Cell Cycle 2016; 14:3713-24. [PMID: 26505547 DOI: 10.1080/15384101.2015.1104437] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
PURPOSE Over 90% of pancreatic adenocarcinoma PC express oncogenic mutant KRAS that constitutively activates the Raf-MEK-MAPK pathway conferring resistance to both radiation and chemotherapy. MEK inhibitors have shown promising anti-tumor responses in recent preclinical and clinical studies, and are currently being tested in combination with radiation in clinical trials. Here, we have evaluated the radiosensitizing potential of a novel MEK1/2 inhibitor GSK1120212 (GSK212,or trametinib) and evaluated whether MEK1/2 inhibition alters DNA repair mechanisms in multiple PC cell lines. METHODS Radiosensitization and DNA double-strand break (DSB) repair were evaluated by clonogenic assays, comet assay, nuclear foci formation (γH2AX, DNA-PK, 53BP1, BRCA1, and RAD51), and by functional GFP-reporter assays for homologous recombination (HR) and non-homologous end-joining (NHEJ). Expression and activation of DNA repair proteins were measured by immunoblotting. RESULTS GSK212 blocked ERK1/2 activity and radiosensitized multiple KRAS mutant PC cell lines. Prolonged pre-treatment with GSK212 for 24-48 hours was required to observe significant radiosensitization. GSK212 treatment resulted in delayed resolution of DNA damage by comet assays and persistent γH2AX nuclear foci. GSK212 treatment also resulted in altered BRCA1, RAD51, DNA-PK, and 53BP1 nuclear foci appearance and resolution after radiation. Using functional reporters, GSK212 caused repression of both HR and NHEJ repair activity. Moreover, GSK212 suppressed the expression and activation of a number of DSB repair pathway intermediates including BRCA1, DNA-PK, RAD51, RRM2, and Chk-1. CONCLUSION GSK212 confers radiosensitization to KRAS-driven PC cells by suppressing major DNA-DSB repair pathways. These data provide support for the combination of MEK1/2 inhibition and radiation in the treatment of PC.
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Affiliation(s)
- Adriana Estrada-Bernal
- a The Ohio State University Medical Center; Arthur G James Comprehensive Cancer Center and Richard J Solove Research Institute ; Columbus , OH USA
| | - Moumita Chatterjee
- a The Ohio State University Medical Center; Arthur G James Comprehensive Cancer Center and Richard J Solove Research Institute ; Columbus , OH USA
| | - S Jaharul Haque
- a The Ohio State University Medical Center; Arthur G James Comprehensive Cancer Center and Richard J Solove Research Institute ; Columbus , OH USA
| | - Linlin Yang
- a The Ohio State University Medical Center; Arthur G James Comprehensive Cancer Center and Richard J Solove Research Institute ; Columbus , OH USA
| | - Meredith A Morgan
- b University of Michigan Comprehensive Cancer Center ; Ann Arbor , MI , USA
| | - Shweta Kotian
- a The Ohio State University Medical Center; Arthur G James Comprehensive Cancer Center and Richard J Solove Research Institute ; Columbus , OH USA
| | - David Morrell
- a The Ohio State University Medical Center; Arthur G James Comprehensive Cancer Center and Richard J Solove Research Institute ; Columbus , OH USA
| | - Arnab Chakravarti
- a The Ohio State University Medical Center; Arthur G James Comprehensive Cancer Center and Richard J Solove Research Institute ; Columbus , OH USA
| | - Terence M Williams
- a The Ohio State University Medical Center; Arthur G James Comprehensive Cancer Center and Richard J Solove Research Institute ; Columbus , OH USA
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105
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Li M, Cole F, Patel DS, Misenko SM, Her J, Malhowski A, Alhamza A, Zheng H, Baer R, Ludwig T, Jasin M, Nussenzweig A, Serrano L, Bunting SF. 53BP1 ablation rescues genomic instability in mice expressing 'RING-less' BRCA1. EMBO Rep 2016; 17:1532-1541. [PMID: 27670884 DOI: 10.15252/embr.201642497] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 09/09/2016] [Indexed: 11/09/2022] Open
Abstract
BRCA1 mutations strongly predispose affected individuals to breast and ovarian cancer, but the mechanism by which BRCA1 acts as a tumor suppressor is not fully understood. Homozygous deletion of exon 2 of the mouse Brca1 gene normally causes embryonic lethality, but we show that exon 2-deleted alleles of Brca1 are expressed as a mutant isoform that lacks the N-terminal RING domain. This "RING-less" BRCA1 protein is stable and efficiently recruited to the sites of DNA damage. Surprisingly, robust RAD51 foci form in cells expressing RING-less BRCA1 in response to DNA damage, but the cells nonetheless display the substantial genomic instability. Genomic instability can be rescued by the deletion of Trp53bp1, which encodes the DNA damage response factor 53BP1, and mice expressing RING-less BRCA1 do not show an increased susceptibility to tumors in the absence of 53BP1. Genomic instability in cells expressing RING-less BRCA1 correlates with the loss of BARD1 and a defect in restart of replication forks after hydroxyurea treatment, suggesting a role of BRCA1-BARD1 in genomic integrity that is independent of RAD51 loading.
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Affiliation(s)
- Minxing Li
- Department of Molecular Biology and Biochemistry, Rutgers The State University of New Jersey, Piscataway, NJ, USA
| | - Francesca Cole
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.,Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, TX, USA
| | - Dharm S Patel
- Department of Molecular Biology and Biochemistry, Rutgers The State University of New Jersey, Piscataway, NJ, USA
| | - Sarah M Misenko
- Department of Molecular Biology and Biochemistry, Rutgers The State University of New Jersey, Piscataway, NJ, USA
| | - Joonyoung Her
- Department of Molecular Biology and Biochemistry, Rutgers The State University of New Jersey, Piscataway, NJ, USA
| | - Amy Malhowski
- Laboratory of Genome Integrity, Center for Cancer Research, National Cancer Institute National Institutes of Health, Bethesda, MD, USA
| | - Ali Alhamza
- Department of Molecular Biology and Biochemistry, Rutgers The State University of New Jersey, Piscataway, NJ, USA
| | - Haiyan Zheng
- Biological Mass Spectrometry Facility, Rutgers The State University of New Jersey, Piscataway, NJ, USA
| | - Richard Baer
- Institute of Cancer Genetics, Department of Pathology & Cell Biology, Columbia University Medical Center, New York, NY, USA
| | - Thomas Ludwig
- Department of Cancer Biology & Genetics, Ohio State University, Columbus, OH, USA
| | - Maria Jasin
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
| | - André Nussenzweig
- Laboratory of Genome Integrity, Center for Cancer Research, National Cancer Institute National Institutes of Health, Bethesda, MD, USA
| | - Lourdes Serrano
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers The State University of New Jersey, Piscataway, NJ, USA
| | - Samuel F Bunting
- Department of Molecular Biology and Biochemistry, Rutgers The State University of New Jersey, Piscataway, NJ, USA
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106
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Moureau S, Luessing J, Harte EC, Voisin M, Lowndes NF. A role for the p53 tumour suppressor in regulating the balance between homologous recombination and non-homologous end joining. Open Biol 2016; 6:rsob.160225. [PMID: 27655732 PMCID: PMC5043586 DOI: 10.1098/rsob.160225] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 08/25/2016] [Indexed: 12/24/2022] Open
Abstract
Loss of p53, a transcription factor activated by cellular stress, is a frequent event in cancer. The role of p53 in tumour suppression is largely attributed to cell fate decisions. Here, we provide evidence supporting a novel role for p53 in the regulation of DNA double-strand break (DSB) repair pathway choice. 53BP1, another tumour suppressor, was initially identified as p53 Binding Protein 1, and has been shown to inhibit DNA end resection, thereby stimulating non-homologous end joining (NHEJ). Yet another tumour suppressor, BRCA1, reciprocally promotes end resection and homologous recombination (HR). Here, we show that in both human and mouse cells, the absence of p53 results in impaired 53BP1 focal recruitment to sites of DNA damage induced by ionizing radiation. This effect is largely independent of cell cycle phase and the extent of DNA damage. In p53-deficient cells, diminished localization of 53BP1 is accompanied by a reciprocal increase in BRCA1 recruitment to DSBs. Consistent with these findings, we demonstrate that DSB repair via NHEJ is abrogated, while repair via homology-directed repair (HDR) is stimulated. Overall, we propose that in addition to its role as an ‘effector’ protein in the DNA damage response, p53 plays a role in the regulation of DSB repair pathway choice.
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Affiliation(s)
- Sylvie Moureau
- Genome Stability Laboratory, Centre for Chromosome Biology and School of Natural Science, Biomedical Science Building, National University of Ireland Galway, Dangan, Ireland
| | - Janna Luessing
- Genome Stability Laboratory, Centre for Chromosome Biology and School of Natural Science, Biomedical Science Building, National University of Ireland Galway, Dangan, Ireland
| | - Emma Christina Harte
- Genome Stability Laboratory, Centre for Chromosome Biology and School of Natural Science, Biomedical Science Building, National University of Ireland Galway, Dangan, Ireland
| | - Muriel Voisin
- Genome Stability Laboratory, Centre for Chromosome Biology and School of Natural Science, Biomedical Science Building, National University of Ireland Galway, Dangan, Ireland
| | - Noel Francis Lowndes
- Genome Stability Laboratory, Centre for Chromosome Biology and School of Natural Science, Biomedical Science Building, National University of Ireland Galway, Dangan, Ireland
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107
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Del Poggetto E, Tanturli M, Ben-Califa N, Gozzini A, Tusa I, Cheloni G, Marzi I, Cipolleschi MG, Kashman Y, Neumann D, Rovida E, Dello Sbarba P. Salarin C inhibits the maintenance of chronic myeloid leukemia progenitor cells. Cell Cycle 2016; 14:3146-54. [PMID: 26291130 DOI: 10.1080/15384101.2015.1078029] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
We previously showed that incubation of chronic myeloid leukemia (CML) cells in very low oxygen selects a cell subset where the oncogenetic BCR/Abl protein is suppressed and which is thereby refractory to tyrosine kinase inhibitors used for CML therapy. In this study, salarin C, an anticancer macrolide extracted from the Fascaplysinopsis sponge, was tested as for its activity on CML cells, especially after their incubation in atmosphere at 0.1% oxygen. Salarin C induced mitotic cycle arrest, apoptosis and DNA damage. Salarin C also concentration-dependently inhibited the maintenance of stem cell potential in cultures in low oxygen of either CML cell lines or primary cells. Surprisingly, the drug also concentration-dependently enforced the maintenance of BCR/Abl signaling in low oxygen, an effect which was paralleled by the rescue of sensitivity of stem cell potential to IM. These results suggest a potential use of salarin C for the suppression of CML cells refractory to tyrosine kinase inhibitors.
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Affiliation(s)
- E Del Poggetto
- a Department of Experimental and Clinical Biomedical Sciences "Mario Serio" ; Universita degli Studi di Firenze ; Florence , Italy
| | - M Tanturli
- a Department of Experimental and Clinical Biomedical Sciences "Mario Serio" ; Universita degli Studi di Firenze ; Florence , Italy
| | - N Ben-Califa
- b Department of Cell and Developmental Biology; Sackler Faculty of Medicine ; Tel Aviv University ; Tel Aviv , Israel
| | - A Gozzini
- c Hematology Unit; "Careggi" University Hospital ; Florence , Italy
| | - I Tusa
- a Department of Experimental and Clinical Biomedical Sciences "Mario Serio" ; Universita degli Studi di Firenze ; Florence , Italy
| | - G Cheloni
- a Department of Experimental and Clinical Biomedical Sciences "Mario Serio" ; Universita degli Studi di Firenze ; Florence , Italy
| | - I Marzi
- a Department of Experimental and Clinical Biomedical Sciences "Mario Serio" ; Universita degli Studi di Firenze ; Florence , Italy
| | - M G Cipolleschi
- a Department of Experimental and Clinical Biomedical Sciences "Mario Serio" ; Universita degli Studi di Firenze ; Florence , Italy
| | - Y Kashman
- d School of Chemistry ; Tel Aviv University ; Tel Aviv , Israel
| | - D Neumann
- b Department of Cell and Developmental Biology; Sackler Faculty of Medicine ; Tel Aviv University ; Tel Aviv , Israel
| | - E Rovida
- a Department of Experimental and Clinical Biomedical Sciences "Mario Serio" ; Universita degli Studi di Firenze ; Florence , Italy
| | - P Dello Sbarba
- a Department of Experimental and Clinical Biomedical Sciences "Mario Serio" ; Universita degli Studi di Firenze ; Florence , Italy
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108
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Selvaratnam J, Robaire B. Overexpression of catalase in mice reduces age-related oxidative stress and maintains sperm production. Exp Gerontol 2016; 84:12-20. [PMID: 27575890 DOI: 10.1016/j.exger.2016.08.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Revised: 08/22/2016] [Accepted: 08/25/2016] [Indexed: 11/18/2022]
Abstract
Advanced paternal age is associated with increased complications in pregnancy and genetic diseases in offspring. Oxidative stress is a major contributor to the damage accumulated in sperm during aging. Complex networks of antioxidants regulate reactive oxygen species (ROS) in the testis. While mounting evident shows that redox dysfunction compromises the quality of developing male germ cells, the mechanisms by which aging causes this remain unclear. Furthermore, therapies to successfully alleviate aging-associated loss in germ cell quality are limited. The antioxidant catalase (CAT) has been used in aging-associated pathologies to alleviate oxidative stress. We used mice overexpressing CAT (MCAT) to determine whether CAT overexpression alleviates the redox dysfunction observed with aging. We found that MCAT mice did not exhibit the age-dependent loss of spermatozoa, nor did they show aging associated loss in testicular germ and Sertoli cells seen in wild type (WT). Low overall ROS and reduced peroxynitrite levels were detected in spermatocytes from aged MCAT mice, following exposure to the pro-oxidant tert-butyl hydroperoxide. Germ cells from young MCATs showed elevated levels of DNA-damage repair markers, γ-H2AX and 53BP1, but this response was lost with aging. Finally, we found oxidative stress induced 8-oxodG lesions to increase in sperm with aging; these lesions were significantly reduced in aged MCAT and these mice showed no decrease in the age-dependent number of pups per litter. Thus we conclude that aged MCAT mice generate sperm at the same rate as young mice; these sperm are protected from oxidative stress associated damage.
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Affiliation(s)
- Johanna Selvaratnam
- Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec H3G 1Y6, Canada
| | - Bernard Robaire
- Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec H3G 1Y6, Canada; Obstetrics and Gynecology, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec H3G 1Y6, Canada.
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109
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Skrdlant L, Stark JM, Lin RJ. Myelodysplasia-associated mutations in serine/arginine-rich splicing factor SRSF2 lead to alternative splicing of CDC25C. BMC Mol Biol 2016; 17:18. [PMID: 27552991 PMCID: PMC4994158 DOI: 10.1186/s12867-016-0071-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Accepted: 08/16/2016] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Serine-arginine rich splicing factor 2 (SRSF2) is a protein known for its role in RNA splicing and genome stability. It has been recently discovered that SRSF2, along with other splicing regulators, is frequently mutated in patients with myelodysplastic syndrome (MDS). The most common MDS mutations in SRSF2 occur at proline 95; the mutant proteins are shown to have different RNA binding preferences, which may contribute to splicing changes detected in mutant cells. However, the influence of these SRSF2 MDS-associated mutations on specific splicing events remains poorly understood. RESULTS A tetracycline-inducible TF-1 erythroleukemia cell line was transduced with retroviruses to create cell lines expressing HA-tagged wildtype SRSF2, SRSF2 with proline 95 point mutations found in MDS, or SRSF2 with a deletion of one of the four major domains of the protein. Effects of these mutants on apoptosis and specific alternative splicing events were evaluated. Cells were also treated with DNA damaging drugs for comparison. MDS-related P95 point mutants of SRSF2 were expressed and phosphorylated at similar levels as wildtype SRSF2. However, cells expressing mutant SRSF2 exhibited higher levels of apoptosis than cells expressing wildtype SRSF2. Regarding alternative splicing events, in nearly all examined cases, SRSF2 P95 mutants acted in a similar fashion as the wildtype SRSF2. However, cells expressing SRSF2 P95 mutants had a percent increase in the C5 spliced isoform of cell division cycle 25C (CDC25C). The same alternative splicing of CDC25C was detected by treating cells with DNA damaging drugs, such as cisplatin, camptothecin, and trichostatin A at appropriate dosage. However, unlike DNA damaging drugs, SRSF2 P95 mutants did not activate the Ataxia telangiectasia mutated (ATM) pathway. CONCLUSION SRSF2 P95 mutants lead to alternative splicing of CDC25C in a manner that is not dependent on the DNA damage response.
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Affiliation(s)
- Lindsey Skrdlant
- Department of Molecular and Cellular Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, CA 91010 USA
| | - Jeremy M. Stark
- Department of Cancer Genetics and Epigenetics, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, CA 91010 USA
| | - Ren-Jang Lin
- Department of Molecular and Cellular Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, CA 91010 USA
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110
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Heiser K, Nicholas C, Garcea RL. Activation of DNA damage repair pathways by murine polyomavirus. Virology 2016; 497:346-356. [PMID: 27529739 DOI: 10.1016/j.virol.2016.07.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 07/08/2016] [Accepted: 07/26/2016] [Indexed: 11/27/2022]
Abstract
Nuclear replication of DNA viruses activates DNA damage repair (DDR) pathways, which are thought to detect and inhibit viral replication. However, many DNA viruses also depend on these pathways in order to optimally replicate their genomes. We investigated the relationship between murine polyomavirus (MuPyV) and components of DDR signaling pathways including CHK1, CHK2, H2AX, ATR, and DNAPK. We found that recruitment and retention of DDR proteins at viral replication centers was independent of H2AX, as well as the viral small and middle T-antigens. Additionally, infectious virus production required ATR kinase activity, but was independent of CHK1, CHK2, or DNAPK signaling. ATR inhibition did not reduce the total amount of viral DNA accumulated, but affected the amount of virus produced, indicating a defect in virus assembly. These results suggest that MuPyV may utilize a subset of DDR proteins or non-canonical DDR signaling pathways in order to efficiently replicate and assemble.
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Affiliation(s)
- Katie Heiser
- Department of Molecular, Cellular, and Developmental Biology and BioFrontiers Institute, University of Colorado at Boulder, Jennie Smoly Caruthers Biotechnology Building, 3415 Colorado Avenue, Boulder, CO 80303, USA
| | - Catherine Nicholas
- Department of Molecular, Cellular, and Developmental Biology and BioFrontiers Institute, University of Colorado at Boulder, Jennie Smoly Caruthers Biotechnology Building, 3415 Colorado Avenue, Boulder, CO 80303, USA
| | - Robert L Garcea
- Department of Molecular, Cellular, and Developmental Biology and BioFrontiers Institute, University of Colorado at Boulder, Jennie Smoly Caruthers Biotechnology Building, 3415 Colorado Avenue, Boulder, CO 80303, USA.
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111
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Chen Q, Yu X. OGT restrains the expansion of DNA damage signaling. Nucleic Acids Res 2016; 44:9266-9278. [PMID: 27458206 PMCID: PMC5100584 DOI: 10.1093/nar/gkw663] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 07/13/2016] [Indexed: 12/22/2022] Open
Abstract
O-linked N-acetylglucosamine linkage (O-GlcNAcylation) to serine or threonine residues regulates numerous biological processes; however, its role in DNA damage response remains elusive. Here, we found that O-GlcNAcylation is induced by DNA damage response. O-GlcNAc transferase (OGT), the solo enzyme for O-GlcNAcylation, relocates to the sites of DNA damage and induces the O-GlcNAcylation of histone H2AX and mediator of DNA damage checkpoint 1 (MDC1). The O-GlcNAcylation negatively regulates DNA double-strand break-induced phosphorylation of H2AX and MDC1 by restraining the expansion of these phosphorylation events from the sites of DNA damage. Therefore, our study reveals the molecular mechanism and biological function of OGT-dependent O-GlcNAcylation in response to DNA damage.
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Affiliation(s)
- Qiang Chen
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA
| | - Xiaochun Yu
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA
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112
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Wang L, Zhang P, Molkentine DP, Chen C, Molkentine JM, Piao H, Raju U, Zhang J, Valdecanas DR, Tailor RC, Thames HD, Buchholz TA, Chen J, Ma L, Mason KA, Ang KK, Meyn RE, Skinner HD. TRIP12 as a mediator of human papillomavirus/p16-related radiation enhancement effects. Oncogene 2016; 36:820-828. [PMID: 27425591 DOI: 10.1038/onc.2016.250] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 05/16/2016] [Accepted: 06/03/2016] [Indexed: 12/21/2022]
Abstract
Patients with human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) have better responses to radiotherapy and higher overall survival rates than do patients with HPV-negative HNSCC, but the mechanisms underlying this phenomenon are unknown. p16 is used as a surrogate marker for HPV infection. Our goal was to examine the role of p16 in HPV-related favorable treatment outcomes and to investigate the mechanisms by which p16 may regulate radiosensitivity. HNSCC cells and xenografts (HPV/p16-positive and -negative) were used. p16-overexpressing and small hairpin RNA-knockdown cells were generated, and the effect of p16 on radiosensitivity was determined by clonogenic cell survival and tumor growth delay assays. DNA double-strand breaks (DSBs) were assessed by immunofluorescence analysis of 53BP1 foci; DSB levels were determined by neutral comet assay; western blotting was used to evaluate protein changes; changes in protein half-life were tested with a cycloheximide assay; gene expression was examined by real-time polymerase chain reaction; and data from The Cancer Genome Atlas HNSCC project were analyzed. p16 overexpression led to downregulation of TRIP12, which in turn led to increased RNF168 levels, repressed DNA damage repair (DDR), increased 53BP1 foci and enhanced radioresponsiveness. Inhibition of TRIP12 expression further led to radiosensitization, and overexpression of TRIP12 was associated with poor survival in patients with HPV-positive HNSCC. These findings reveal that p16 participates in radiosensitization through influencing DDR and support the rationale of blocking TRIP12 to improve radiotherapy outcomes.
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Affiliation(s)
- L Wang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - P Zhang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - D P Molkentine
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - C Chen
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - J M Molkentine
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - H Piao
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.,Division of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
| | - U Raju
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - J Zhang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - D R Valdecanas
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - R C Tailor
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - H D Thames
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - T A Buchholz
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - J Chen
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - L Ma
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - K A Mason
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - K-K Ang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.,Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - R E Meyn
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - H D Skinner
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
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113
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Shimada M, Goshima T, Matsuo H, Johmura Y, Haruta M, Murata K, Tanaka H, Ikawa M, Nakanishi K, Nakanishi M. Essential role of autoactivation circuitry on Aurora B-mediated H2AX-pS121 in mitosis. Nat Commun 2016; 7:12059. [PMID: 27389782 PMCID: PMC4941122 DOI: 10.1038/ncomms12059] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 05/20/2016] [Indexed: 02/06/2023] Open
Abstract
Proper deposition and activation of Aurora B at the centromere is critical for faithful chromosome segregation in mammals. However, the mechanistic basis for abrupt Aurora B kinase activation at the centromere has not yet been fully understood. We demonstrate here that Aurora B-mediated phosphorylation of histone H2AX at serine 121 (H2AX-pS121) promotes Aurora B autophosphorylation and is essential for proper chromosome segregation. Aurora B-mediated H2AX-pS121 is specifically detected at the centromere during mitosis. H2AX depletion results in a severe defect in activation and deposition of Aurora B at this locus. A phosphomimic mutant of H2AX at S121 interacts with activated Aurora B more efficiently than wild-type in vitro. Taken together, these results propose a model in which Aurora B-mediated H2AX-pS121 probably provide a platform for Aurora B autoactivation circuitry at centromeres and thus play a pivotal role in proper chromosome segregation. Aurora B activation at the centromere is critical for faithful chromosome segregation in mammals. Here the authors show that Aurora B-mediated phosphorylation of histone H2AX at serine 121 is essential for Aurora B auto-activation circuitry at centromeres, ensuring proper chromosome segregation.
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Affiliation(s)
- Midori Shimada
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
| | - Takahiro Goshima
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
| | - Hiromi Matsuo
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
| | - Yoshikazu Johmura
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
| | - Mayumi Haruta
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
| | - Kazuhiro Murata
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
| | - Hiromitsu Tanaka
- Faculty of Pharmaceutical Sciences, Nagasaki International University, Sasebo, Nagasaki 859-3298, Japan
| | - Masahito Ikawa
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
| | - Keiko Nakanishi
- Department of Perinatology, Institute for Developmental Research, Aichi Human Service Center, 713-8 Kamiya-cho, Kasugai, Aichi 489-0392, Japan
| | - Makoto Nakanishi
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan.,Division of Cancer Cell Biology, Department of Cancer Biology, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
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114
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Kulashreshtha M, Mehta IS, Kumar P, Rao BJ. Chromosome territory relocation during DNA repair requires nuclear myosin 1 recruitment to chromatin mediated by ϒ-H2AX signaling. Nucleic Acids Res 2016; 44:8272-91. [PMID: 27365048 PMCID: PMC5041470 DOI: 10.1093/nar/gkw573] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 06/03/2016] [Indexed: 11/22/2022] Open
Abstract
During DNA damage response (DDR), certain gene rich chromosome territories (CTs) relocate to newer positions within interphase nuclei and revert to their native locations following repair. Such dynamic relocation of CTs has been observed under various cellular conditions, however, the underlying mechanistic basis of the same has remained largely elusive. In this study, we aim to understand the temporal and molecular details of such crosstalk between DDR signaling and CT relocation dynamics. We demonstrate that signaling at DNA double strand breaks (DSBs) by the phosphorylated histone variant (ϒ-H2AX) is a pre-requisite for damage induced CT relocation, as cells deficient in ϒ-H2AX signaling fail to exhibit such a response. Inhibition of Rad51 or DNA Ligase IV mediated late steps of double strand break repair does not seem to abrogate CT relocation completely. Upon DNA damage, an increase in the levels of chromatin bound motor protein nuclear myosin 1 (NM1) ensues, which appears to be functionally linked to ϒ-H2AX signaling. Importantly, the motor function of NM1 is essential for its recruitment to chromatin and CT relocation following damage. Taking these observations together, we propose that early DDR sensing and signaling result in NM1 recruitment to chromosomes which in turn guides DNA damage induced CT relocation.
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Affiliation(s)
- Mugdha Kulashreshtha
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, Maharashtra 400005, India
| | - Ishita S Mehta
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, Maharashtra 400005, India UM-DAE Centre for Excellence in Basic Sciences, Biological Sciences, Kalina Campus, Santacruz (E), Mumbai, Maharashtra 400098, India
| | - Pradeep Kumar
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, Maharashtra 400005, India UM-DAE Centre for Excellence in Basic Sciences, Biological Sciences, Kalina Campus, Santacruz (E), Mumbai, Maharashtra 400098, India
| | - Basuthkar J Rao
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, Maharashtra 400005, India
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115
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Huang F, Liu Q, Xie S, Xu J, Huang B, Wu Y, Xia D. Cypermethrin Induces Macrophages Death through Cell Cycle Arrest and Oxidative Stress-Mediated JNK/ERK Signaling Regulated Apoptosis. Int J Mol Sci 2016; 17:ijms17060885. [PMID: 27322250 PMCID: PMC4926419 DOI: 10.3390/ijms17060885] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/17/2016] [Accepted: 05/30/2016] [Indexed: 12/25/2022] Open
Abstract
Cypermethrin is one of the most highly effective synthetic pyrethroid insecticides. The toxicity of cypermethrin to the reproductive and nervous systems has been well studied. However, little is known about the toxic effect of cypermethrin on immune cells such as macrophages. Here, we investigated the cytotoxicity of cypermethrin on macrophages and the underlying molecular mechanisms. We found that cypermethrin reduced cell viability and induced apoptosis in RAW 264.7 cells. Cypermethrin also increased reactive oxygen species (ROS) production and DNA damage in a dose-dependent manner. Moreover, cypermethrin-induced G1 cell cycle arrest was associated with an enhanced expression of p21, wild-type p53, and down-regulation of cyclin D1, cyclin E and CDK4. In addition, cypermethrin treatment activated MAPK signal pathways by inducing c-Jun N-terminal kinase (JNK) and extracellular regulated protein kinases 1/2 ERK1/2 phosphorylation, and increased the cleaved poly ADP-ribose polymerase (PARP). Further, pretreatment with antioxidant N-acetylcysteine (NAC) effectively abrogated cypermethrin-induced cell cytotoxicity, G1 cell cycle arrest, DNA damage, PARP activity, and JNK and ERK1/2 activation. The specific JNK inhibitor (SP600125) and ERK1/2 inhibitor (PD98059) effectively reversed the phosphorylation level of JNK and ERK1/2, and attenuated the apoptosis. Taken together, these data suggested that cypermethrin caused immune cell death via inducing cell cycle arrest and apoptosis regulated by ROS-mediated JNK/ERK pathway.
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Affiliation(s)
- Fang Huang
- Department of Toxicology, Zhejiang University School of Public Health, 866 Yu-Hang-Tang Road, Hangzhou 310058, China.
| | - Qiaoyun Liu
- Department of Toxicology, Zhejiang University School of Public Health, 866 Yu-Hang-Tang Road, Hangzhou 310058, China.
| | - Shujun Xie
- Department of Toxicology, Zhejiang University School of Public Health, 866 Yu-Hang-Tang Road, Hangzhou 310058, China.
| | - Jian Xu
- Department of Toxicology, Zhejiang University School of Public Health, 866 Yu-Hang-Tang Road, Hangzhou 310058, China.
| | - Bo Huang
- Department of Toxicology, Zhejiang University School of Public Health, 866 Yu-Hang-Tang Road, Hangzhou 310058, China.
| | - Yihua Wu
- Department of Toxicology, Zhejiang University School of Public Health, 866 Yu-Hang-Tang Road, Hangzhou 310058, China.
| | - Dajing Xia
- Department of Toxicology, Zhejiang University School of Public Health, 866 Yu-Hang-Tang Road, Hangzhou 310058, China.
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116
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Xu Y, Wang S, Miao Q, Jin K, Lou L, Ye X, Xi Y, Ye J. Protective Role of Hinokitiol Against H 2O 2-Induced Injury in Human Corneal Epithelium. Curr Eye Res 2016; 42:47-53. [PMID: 27269503 DOI: 10.3109/02713683.2016.1151530] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE We recently found that hinokitiol has anti-inflammatory activity in human corneal epithelial (HCE) cells. Herein, we investigated the protective role of hinokitiol against H2O2-induced injury in HCE cells and the mechanisms that underlie its action. METHODS HCE cells were incubated with different concentrations of hinokitiol or dimethylsulfoxide (DMSO), which served as a vehicle control, before H2O2 stimulus. The cell viability was evaluated using a cell counting kit-8 (CCK-8) assay. TUNEL, phosphorylated histone γH2A.X, cleaved caspase-3 expression analyses, and location of cytochrome c were conducted to detect cell injury and apoptosis. Reactive oxygen species (ROS), catalase (CAT), superoxide dismutase (SOD), methane dicarboxylic aldehyde (MDA), and total antioxidative capacity (T-AOC) were used to determine oxidative stress. Bcl-2 and Bax protein expressions were measured by western blotting. RESULTS Hinokitiol significantly improved the cell viability, decreased the apoptosis rate, inhibited DNA damage, and reduced cleaved caspase-3 expression and the leakage of cytochrome c from mimitochondrion to cytoplasm of HCE cells against the oxidative stress induced by H2O2. Generation of ROS and MDA and decreased activity of CAT, SOD, and T-AOC were also ameliorated by hinokitiol administration. Moreover, Bcl-2 expression was down-regulated while Bax was up-regulated by H2O2 stimulus, which were reversed by hinokitiol application. CONCLUSION Hinokitiol protects HCE cells against H2O2-induced injury likely by its antioxidant activity and modulating the Bcl-2 signaling pathway.
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Affiliation(s)
- Yufeng Xu
- a Department of Ophthalmology , The Second Affiliated Hospital of Zhejiang University, College of Medicine , Hangzhou , Zhejiang , China
| | - Shengzhan Wang
- a Department of Ophthalmology , The Second Affiliated Hospital of Zhejiang University, College of Medicine , Hangzhou , Zhejiang , China
| | - Qi Miao
- a Department of Ophthalmology , The Second Affiliated Hospital of Zhejiang University, College of Medicine , Hangzhou , Zhejiang , China
| | - Kai Jin
- a Department of Ophthalmology , The Second Affiliated Hospital of Zhejiang University, College of Medicine , Hangzhou , Zhejiang , China
| | - Lixia Lou
- a Department of Ophthalmology , The Second Affiliated Hospital of Zhejiang University, College of Medicine , Hangzhou , Zhejiang , China
| | - Xin Ye
- a Department of Ophthalmology , The Second Affiliated Hospital of Zhejiang University, College of Medicine , Hangzhou , Zhejiang , China
| | - Yan Xi
- a Department of Ophthalmology , The Second Affiliated Hospital of Zhejiang University, College of Medicine , Hangzhou , Zhejiang , China
| | - Juan Ye
- a Department of Ophthalmology , The Second Affiliated Hospital of Zhejiang University, College of Medicine , Hangzhou , Zhejiang , China
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117
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Effect of mild temperature shift on poly(ADP-ribose) and γH2AX levels in cultured cells. Biochem Biophys Res Commun 2016; 476:594-599. [PMID: 27262441 DOI: 10.1016/j.bbrc.2016.06.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 06/01/2016] [Indexed: 12/28/2022]
Abstract
Poly (ADP-ribose) (PAR) is rapidly synthesized by PAR polymerases (PARPs) upon activation by DNA single- and double-strand breaks. In this study, we examined the quantitative amount of PAR in HeLa cells cultured within the physiological temperatures below 41 °C for verification of the effect of shifting-up or -down the temperature from 37.0 °C on the DNA breaks, whether the temperature-shift caused breaks that could be monitored by the level of PAR. While PAR level did not change significantly when HeLa cells were cultured at 33.5 °C or 37.0 °C, it was significantly increased 2- and 3-fold when cells were cultured for 12 h and 24 h, respectively, at 40.5 °C as compared to 37.0 °C. Similar to the results with HeLa cells, PAR level was increased 2-fold in CHO-K1 cells cultured at 40.5 °C for 24 h as compared to 37.0 °C. As the cellular levels of PAR polymerase1 (PARP1) and PAR glycohydrolase (PARG), a major degradation enzyme for PAR, did not seem to change significantly, this increase could be caused by activation of PARP1 by DNA strand breaks. In fact, γH2AX, claimed to be a marker of DNA double-strand breaks, was found in cell extracts of HeLa cells and CHO-K1 cells at elevated temperature vs. 37.0 °C, and these γH2AX signals were intensified in the presence of 3-aminobenzamide, a PARP inhibitor. The γH2AX immunohistochemistry results in HeLa cells were consistent with Western blot analyses. In HeLa cells, proliferation was significantly suppressed at 40.5 °C in 72 h-continuous cultures and decreased viabilities were also observed after 24-72 h at 40.5 °C. Flow cytometric analyses showed that the HeLa cells were arrested at G2/M after temperature shift-up to 40.5 °C. These physiological changes were potentiated in the presence of 3-aminobenzamide. Decrease in growth rates, increased cytotoxicity and G2/M arrest, were associated with the temperature-shift to 40.5 °C and are indirect evidence of DNA breaks. In addition to γH2AX, PAR could be a sensitive marker for DNA single- and double-strand breaks. These two molecular markers provide evidence of physiological changes occurring within cells.
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118
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Gruosso T, Mieulet V, Cardon M, Bourachot B, Kieffer Y, Devun F, Dubois T, Dutreix M, Vincent-Salomon A, Miller KM, Mechta-Grigoriou F. Chronic oxidative stress promotes H2AX protein degradation and enhances chemosensitivity in breast cancer patients. EMBO Mol Med 2016; 8:527-49. [PMID: 27006338 PMCID: PMC5123617 DOI: 10.15252/emmm.201505891] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Anti‐cancer drugs often increase reactive oxygen species (ROS) and cause DNA damage. Here, we highlight a new cross talk between chronic oxidative stress and the histone variant H2AX, a key player in DNA repair. We observe that persistent accumulation of ROS, due to a deficient JunD‐/Nrf2‐antioxidant response, reduces H2AX protein levels. This effect is mediated by an enhanced interaction of H2AX with the E3 ubiquitin ligase RNF168, which is associated with H2AX poly‐ubiquitination and promotes its degradation by the proteasome. ROS‐mediated H2AX decrease plays a crucial role in chemosensitivity. Indeed, cycles of chemotherapy that sustainably increase ROS reduce H2AX protein levels in Triple‐Negative breast cancer (TNBC) patients. H2AX decrease by such treatment is associated with an impaired NRF2‐antioxidant response and is indicative of the therapeutic efficiency and survival of TNBC patients. Thus, our data describe a novel ROS‐mediated regulation of H2AX turnover, which provides new insights into genetic instability and treatment efficacy in TNBC patients.
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Affiliation(s)
- Tina Gruosso
- Stress and Cancer Laboratory, Equipe Labelisée LNCC, Institut Curie, Paris Cedex 05, France Inserm, U830, Paris, France
| | - Virginie Mieulet
- Stress and Cancer Laboratory, Equipe Labelisée LNCC, Institut Curie, Paris Cedex 05, France Inserm, U830, Paris, France
| | - Melissa Cardon
- Stress and Cancer Laboratory, Equipe Labelisée LNCC, Institut Curie, Paris Cedex 05, France Inserm, U830, Paris, France
| | - Brigitte Bourachot
- Stress and Cancer Laboratory, Equipe Labelisée LNCC, Institut Curie, Paris Cedex 05, France Inserm, U830, Paris, France
| | - Yann Kieffer
- Stress and Cancer Laboratory, Equipe Labelisée LNCC, Institut Curie, Paris Cedex 05, France Inserm, U830, Paris, France
| | - Flavien Devun
- Institut Curie, CNRS UMR3347, INSERM U1021, University Paris-Sud 11, Orsay, France
| | - Thierry Dubois
- Department of Translational Research, Institut Curie, Paris Cedex 05, France
| | - Marie Dutreix
- Institut Curie, CNRS UMR3347, INSERM U1021, University Paris-Sud 11, Orsay, France
| | | | - Kyle Malcolm Miller
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, USA
| | - Fatima Mechta-Grigoriou
- Stress and Cancer Laboratory, Equipe Labelisée LNCC, Institut Curie, Paris Cedex 05, France Inserm, U830, Paris, France
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119
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Agarwal P, Miller KM. The nucleosome: orchestrating DNA damage signaling and repair within chromatin. Biochem Cell Biol 2016; 94:381-395. [PMID: 27240007 DOI: 10.1139/bcb-2016-0017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
DNA damage occurs within the chromatin environment, which ultimately participates in regulating DNA damage response (DDR) pathways and repair of the lesion. DNA damage activates a cascade of signaling events that extensively modulates chromatin structure and organization to coordinate DDR factor recruitment to the break and repair, whilst also promoting the maintenance of normal chromatin functions within the damaged region. For example, DDR pathways must avoid conflicts between other DNA-based processes that function within the context of chromatin, including transcription and replication. The molecular mechanisms governing the recognition, target specificity, and recruitment of DDR factors and enzymes to the fundamental repeating unit of chromatin, i.e., the nucleosome, are poorly understood. Here we present our current view of how chromatin recognition by DDR factors is achieved at the level of the nucleosome. Emerging evidence suggests that the nucleosome surface, including the nucleosome acidic patch, promotes the binding and activity of several DNA damage factors on chromatin. Thus, in addition to interactions with damaged DNA and histone modifications, nucleosome recognition by DDR factors plays a key role in orchestrating the requisite chromatin response to maintain both genome and epigenome integrity.
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Affiliation(s)
- Poonam Agarwal
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, 2506 Speedway Stop A5000, Austin, TX 78712, USA.,Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, 2506 Speedway Stop A5000, Austin, TX 78712, USA
| | - Kyle M Miller
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, 2506 Speedway Stop A5000, Austin, TX 78712, USA.,Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, 2506 Speedway Stop A5000, Austin, TX 78712, USA
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120
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Hofer M, Falk M, Komůrková D, Falková I, Bačíková A, Klejdus B, Pagáčová E, Štefančíková L, Weiterová L, Angelis KJ, Kozubek S, Dušek L, Galbavý Š. Two New Faces of Amifostine: Protector from DNA Damage in Normal Cells and Inhibitor of DNA Repair in Cancer Cells. J Med Chem 2016; 59:3003-17. [PMID: 26978566 DOI: 10.1021/acs.jmedchem.5b01628] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amifostine protects normal cells from DNA damage induction by ionizing radiation or chemotherapeutics, whereas cancer cells typically remain uninfluenced. While confirming this phenomenon, we have revealed by comet assay and currently the most sensitive method of DNA double strand break (DSB) quantification (based on γH2AX/53BP1 high-resolution immunofluorescence microscopy) that amifostine treatment supports DSB repair in γ-irradiated normal NHDF fibroblasts but alters it in MCF7 carcinoma cells. These effects follow from the significantly lower activity of alkaline phosphatase measured in MCF7 cells and their supernatants as compared with NHDF fibroblasts. Liquid chromatography-mass spectrometry confirmed that the amifostine conversion to WR-1065 was significantly more intensive in normal NHDF cells than in tumor MCF cells. In conclusion, due to common differences between normal and cancer cells in their abilities to convert amifostine to its active metabolite WR-1065, amifostine may not only protect in multiple ways normal cells from radiation-induced DNA damage but also make cancer cells suffer from DSB repair alteration.
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Affiliation(s)
- Michal Hofer
- Department of Cell Biology and Radiobiology, Institute of Biophysics, v.v.i., Czech Academy of Sciences , Královopolská 135, CZ-612 65 Brno, Czech Republic
| | - Martin Falk
- Department of Cell Biology and Radiobiology, Institute of Biophysics, v.v.i., Czech Academy of Sciences , Královopolská 135, CZ-612 65 Brno, Czech Republic
| | - Denisa Komůrková
- Department of Cell Biology and Radiobiology, Institute of Biophysics, v.v.i., Czech Academy of Sciences , Královopolská 135, CZ-612 65 Brno, Czech Republic
| | - Iva Falková
- Department of Cell Biology and Radiobiology, Institute of Biophysics, v.v.i., Czech Academy of Sciences , Královopolská 135, CZ-612 65 Brno, Czech Republic.,Department of Medical Technology, St. Elisabeth University of Health and Social Sciences , Palackého 1, SK-810 00 Bratislava, Slovak Republic
| | - Alena Bačíková
- Department of Cell Biology and Radiobiology, Institute of Biophysics, v.v.i., Czech Academy of Sciences , Královopolská 135, CZ-612 65 Brno, Czech Republic
| | | | - Eva Pagáčová
- Department of Cell Biology and Radiobiology, Institute of Biophysics, v.v.i., Czech Academy of Sciences , Královopolská 135, CZ-612 65 Brno, Czech Republic
| | - Lenka Štefančíková
- Department of Cell Biology and Radiobiology, Institute of Biophysics, v.v.i., Czech Academy of Sciences , Královopolská 135, CZ-612 65 Brno, Czech Republic
| | - Lenka Weiterová
- Department of Cell Biology and Radiobiology, Institute of Biophysics, v.v.i., Czech Academy of Sciences , Královopolská 135, CZ-612 65 Brno, Czech Republic
| | - Karel J Angelis
- Institute of Experimental Botany, v.v.i., Czech Academy of Sciences , Na Karlovce 1, CZ-160 00 Prague 6, Czech Republic
| | - Stanislav Kozubek
- Department of Cell Biology and Radiobiology, Institute of Biophysics, v.v.i., Czech Academy of Sciences , Královopolská 135, CZ-612 65 Brno, Czech Republic
| | - Ladislav Dušek
- Institute of Biostatistics and Analyses, Masaryk University , Kamenice 126/3, CZ-625 00 Brno, Czech Republic
| | - Štefan Galbavý
- Department of Medical Technology, St. Elisabeth University of Health and Social Sciences , Palackého 1, SK-810 00 Bratislava, Slovak Republic
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Kocyłowski MK, Rey AJ, Stewart GS, Halazonetis TD. Ubiquitin-H2AX fusions render 53BP1 recruitment to DNA damage sites independent of RNF8 or RNF168. Cell Cycle 2016; 14:1748-58. [PMID: 25695757 PMCID: PMC4615105 DOI: 10.1080/15384101.2015.1010918] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
The mammalian E3 ubiquitin ligases RNF8 and RNF168 facilitate recruitment of the DNA damage response protein 53BP1 to sites of DNA double-strand breaks (DSBs). The mechanism involves recruitment of RNF8, followed by recruitment of RNF168, which ubiquitinates histones H2A/H2AX on K15. 53BP1 then binds to nucleosomes at sites of DNA DSBs by recognizing, in addition to methyl marks, histone H2A/H2AX ubiquitinated on K15. We report here that expressing H2AX fusion proteins with N-terminal bulky moieties can rescue 53BP1 recruitment to sites of DNA DSBs in cells lacking RNF8 or RNF168 or in cells treated with proteasome inhibitors, in which histone ubiquitination at sites of DNA DSBs is compromised. The rescue required S139 at the C-terminus of the H2AX fusion protein and was occasionally accompanied by partial rescue of ubiquitination at sites of DNA DSBs. We conclude that recruitment of 53BP1 to sites of DNA DSBs is possible in the absence of RNF8 or RNF168, but still dependent on chromatin ubiquitination.
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Affiliation(s)
- Maciej K Kocyłowski
- a Department of Molecular Biology; University of Geneva ; Geneva , Switzerland
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122
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Shastri VM, Schmidt KH. Cellular defects caused by hypomorphic variants of the Bloom syndrome helicase gene BLM. Mol Genet Genomic Med 2016; 4:106-19. [PMID: 26788541 PMCID: PMC4707026 DOI: 10.1002/mgg3.188] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 10/28/2015] [Accepted: 10/29/2015] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Bloom syndrome is an autosomal recessive disorder characterized by extraordinary cancer incidence early in life and an average life expectancy of ~27 years. Premature stop codons in BLM, which encodes a DNA helicase that functions in DNA double-strand-break repair, make up the vast majority of Bloom syndrome mutations, with only 13 single amino acid changes identified in the syndrome. Sequencing projects have identified nearly one hundred single nucleotide variants in BLM that cause amino acid changes of uncertain significance. METHODS AND RESULTS Here, in addition to identifying five BLM variants incapable of complementing certain defects of Bloom syndrome cells, making them candidates for new Bloom syndrome causing mutations, we characterize a new class of BLM variants that cause some, but not all, cellular defects of Bloom syndrome. We find elevated sister-chromatid exchanges, a delayed DNA damage response and inefficient DNA repair. Conversely, hydroxyurea sensitivity and quadriradial chromosome accumulation, both characteristic of Bloom syndrome cells, are absent. These intermediate variants affect sites in BLM that function in ATP hydrolysis and in contacting double-stranded DNA. CONCLUSION Allele frequency and cellular defects suggest candidates for new Bloom syndrome causing mutations, and intermediate BLM variants that are hypomorphic which, instead of causing Bloom syndrome, may increase a person's risk for cancer or possibly other Bloom-syndrome-associated disorders, such as type-2 diabetes.
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Affiliation(s)
- Vivek M Shastri
- Department of Cell Biology, Microbiology and Molecular BiologyUniversity of South FloridaTampaFlorida33620; Graduate Program in Cell and Molecular BiologyUniversity of South FloridaTampaFlorida33620
| | - Kristina H Schmidt
- Department of Cell Biology, Microbiology and Molecular BiologyUniversity of South FloridaTampaFlorida33620; Cancer Biology and Evolution ProgramH. Lee Moffitt Cancer Center and Research InstituteTampaFlorida33612
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Jung C, Hong JY, Bae SY, Kang SS, Park HJ, Lee SK. Antitumor Activity of Americanin A Isolated from the Seeds of Phytolacca americana by Regulating the ATM/ATR Signaling Pathway and the Skp2-p27 Axis in Human Colon Cancer Cells. JOURNAL OF NATURAL PRODUCTS 2015; 78:2983-2993. [PMID: 26595875 DOI: 10.1021/acs.jnatprod.5b00743] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The antiproliferative and antitumor activities of americanin A (1), a neolignan isolated from the seeds of Phytolacca americana, were investigated in human colon cancer cells. Compound 1 inhibited the proliferation of HCT116 human colon cancer cells both in vitro and in vivo. The induction of G2/M cell-cycle arrest by 1 was concomitant with regulation of the ataxia telangiectasia-mutated/ATM and Rad3-related (ATM/ATR) signaling pathway. Treatment with 1 activated ATM and ATR, initiating the subsequent signal transduction cascades that include checkpoint kinase 1 (Chk1), checkpoint kinase 2 (Chk2), and tumor suppressor p53. Another line of evidence underlined the significance of 1 in regulation of the S phase kinase-associated protein 2 (Skp2)-p27 axis. Compound 1 targeted selectively Skp2 for degradation and thereby stabilized p27. Therefore, compound 1 suppressed the activity of cyclin B1 and its partner cell division cycle 2 (cdc2) to prevent entry into mitosis. Furthermore, prolonged treatment with 1 induced apoptosis by producing excessive reactive oxygen species. The intraperitoneal administration of 1 inhibited the growth of HCT116 tumor xenografts in nude mice without any overt toxicity. Modulation of the ATM/ATR signaling pathway and the Skp2-p27 axis might be plausible mechanisms of action for the antiproliferative and antitumor activities of 1 in human colon cancer cells.
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Affiliation(s)
- Cholomi Jung
- College of Pharmacy, Natural Products Research Institute, Seoul National University , Seoul 151-742, Korea
| | - Ji-Young Hong
- College of Pharmacy, Natural Products Research Institute, Seoul National University , Seoul 151-742, Korea
| | - Song Yi Bae
- College of Pharmacy, Natural Products Research Institute, Seoul National University , Seoul 151-742, Korea
| | - Sam Sik Kang
- College of Pharmacy, Natural Products Research Institute, Seoul National University , Seoul 151-742, Korea
| | - Hyen Joo Park
- College of Pharmacy, Natural Products Research Institute, Seoul National University , Seoul 151-742, Korea
| | - Sang Kook Lee
- College of Pharmacy, Natural Products Research Institute, Seoul National University , Seoul 151-742, Korea
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124
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How cancer cells hijack DNA double-strand break repair pathways to gain genomic instability. Biochem J 2015; 471:1-11. [PMID: 26392571 DOI: 10.1042/bj20150582] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
DNA DSBs (double-strand breaks) are a significant threat to the viability of a normal cell, since they can result in loss of genetic material if mitosis or replication is attempted in their presence. Consequently, evolutionary pressure has resulted in multiple pathways and responses to enable DSBs to be repaired efficiently and faithfully. Cancer cells, which are under pressure to gain genomic instability, have a striking ability to avoid the elegant mechanisms by which normal cells maintain genomic stability. Current models suggest that, in normal cells, DSB repair occurs in a hierarchical manner that promotes rapid and efficient rejoining first, with the utilization of additional steps or pathways of diminished accuracy if rejoining is unsuccessful or delayed. In the present review, we evaluate the fidelity of DSB repair pathways and discuss how cancer cells promote the utilization of less accurate processes. Homologous recombination serves to promote accuracy and stability during replication, providing a battlefield for cancer to gain instability. Non-homologous end-joining, a major DSB repair pathway in mammalian cells, usually operates with high fidelity and only switches to less faithful modes if timely repair fails. The transition step is finely tuned and provides another point of attack during tumour progression. In addition to DSB repair, a DSB signalling response activates processes such as cell cycle checkpoint arrest, which enhance the possibility of accurate DSB repair. We consider the ways by which cancers modify and hijack these processes to gain genomic instability.
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125
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Suchánková J, Kozubek S, Legartová S, Sehnalová P, Küntziger T, Bártová E. Distinct kinetics of DNA repair protein accumulation at DNA lesions and cell cycle-dependent formation of γH2AX- and NBS1-positive repair foci. Biol Cell 2015; 107:440-54. [DOI: 10.1111/boc.201500050] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 10/13/2015] [Indexed: 01/10/2023]
Affiliation(s)
- Jana Suchánková
- Institute of Biophysics; Academy of Sciences of the Czech Republic; Brno 612 65 the Czech Republic
| | - Stanislav Kozubek
- Institute of Biophysics; Academy of Sciences of the Czech Republic; Brno 612 65 the Czech Republic
| | - Soňa Legartová
- Institute of Biophysics; Academy of Sciences of the Czech Republic; Brno 612 65 the Czech Republic
| | - Petra Sehnalová
- Institute of Biophysics; Academy of Sciences of the Czech Republic; Brno 612 65 the Czech Republic
| | | | - Eva Bártová
- Institute of Biophysics; Academy of Sciences of the Czech Republic; Brno 612 65 the Czech Republic
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Abstract
DNA damage is correlated with and may drive the ageing process. Neurons in the brain are postmitotic and are excluded from many forms of DNA repair; therefore, neurons are vulnerable to various neurodegenerative diseases. The challenges facing the field are to understand how and when neuronal DNA damage accumulates, how this loss of genomic integrity might serve as a 'time keeper' of nerve cell ageing and why this process manifests itself as different diseases in different individuals.
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Affiliation(s)
- Hei-man Chow
- Division of Life Science and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.,Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Karl Herrup
- Division of Life Science and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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127
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YANG LINA, LIU YUANYUAN, SUN CHAO, YANG XINRUI, YANG ZHEN, RAN JUNTAO, ZHANG QIUNING, ZHANG HONG, WANG XINYU, WANG XIAOHU. Inhibition of DNA-PKcs enhances radiosensitivity and increases the levels of ATM and ATR in NSCLC cells exposed to carbon ion irradiation. Oncol Lett 2015; 10:2856-2864. [PMID: 26722253 PMCID: PMC4665689 DOI: 10.3892/ol.2015.3730] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 08/20/2015] [Indexed: 11/23/2022] Open
Abstract
Non-small cell lung cancer (NSCLC) exhibits radioresistance to conventional rays, due to its DNA damage repair systems. NSCLC may potentially be sensitized to radiation treatment by reducing those factors that continuously enhance the repair of damaged DNA. In the present study, normal lung fibroblast MRC-5 and lung cancer A549 cells were treated with NU7026 and CGK733, which are inhibitors of the DNA-dependent protein kinase catalytic subunit (PKcs) and ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR), respectively, followed by exposure to X-rays and carbon ion irradiation. The cytotoxic activity, cell survival rate, DNA damage repair ability, cell cycle arrest and apoptosis rate of the treated cells were analyzed with MTT assay, colony formation assay, immunofluorescence and flow cytometry, respectively. The transcription and translation levels of the ATM, ATR and DNA-PKcs genes were detected by reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. The results indicated that the radiosensitivity and DNA repair ability of A549 cells were reduced, and the percentages of apoptotic cells and those arrested at the G2/M phase of the cell cycle were significantly increased, following ionizing radiation with inhibitor-pretreatment. The expression levels of ATM, ATR, DNA-PKcs and phosphorylated histone H2AX, a biomarker for DNA double-strand breaks, were all upregulated at the transcriptional or translational level in A549 cells treated with carbon ion irradiation, compared with the control and X-rays-treated cells. In addition, the treatment with 5–50 µM NU7026 or CGK733 did not produce any obvious cytotoxicity in MRC-5 cells, and the effect of the DNA-PKcs-inhibitor on enhancing the radiosensitivity of A549 cells was stronger than that observed for the ATM and ATR-inhibitor. These findings demonstrated a minor role for ATM and ATR in radiation-induced cell death, since the upregulation of ATM and ATR did not rescue the A549 cells subjected to ionizing irradiation. Therefore, future studies on DNA-PKcs, ATM and ATR may lead to novel specific therapies that supplement general radiotherapy for the treatment of lung cancer.
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128
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Chemical proteomics reveals a γH2AX-53BP1 interaction in the DNA damage response. Nat Chem Biol 2015; 11:807-14. [PMID: 26344695 PMCID: PMC4589150 DOI: 10.1038/nchembio.1908] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 08/12/2015] [Indexed: 11/16/2022]
Abstract
DNA double-strand break repair involves phosphorylation of histone variant H2AX (‘γH2AX’), which accumulates in foci at sites of damage. In current models, the recruitment of multiple DNA repair proteins to γH2AX foci depends mainly on recognition of this ‘mark’ by a single protein, MDC1. However, DNA repair proteins accumulate at γH2AX sites without MDC1, suggesting that other ‘readers’ exist. Here, we use a quantitative chemical proteomics approach to profile direct, phospho-selective γH2AX binders in native proteomes. We identify γH2AX binders, including the DNA repair mediator, 53BP1, which we show recognizes γH2AX through its BRCT domains. Furthermore, we investigate targeting of wild-type 53BP1 or a mutant form deficient in γH2AX binding, to chromosomal breaks resulting from endogenous and exogenous DNA damage. Our results show how direct recognition of γH2AX modulates protein localization at DNA damage sites, and suggest how specific chromatin ‘mark’-‘reader’ interactions contribute to essential mechanisms ensuring genome stability.
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129
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Jayakumar S, Pal D, Sandur SK. Nrf2 facilitates repair of radiation induced DNA damage through homologous recombination repair pathway in a ROS independent manner in cancer cells. Mutat Res 2015; 779:33-45. [PMID: 26133502 DOI: 10.1016/j.mrfmmm.2015.06.007] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 06/06/2015] [Accepted: 06/16/2015] [Indexed: 05/12/2023]
Abstract
Nrf2 is a redox sensitive transcription factor that is involved in the co-ordinated transcription of genes involved in redox homeostasis. But the role of Nrf2 in DNA repair is not investigated in detail. We have employed A549 and MCF7 cells to study the role of Nrf2 on DNA repair by inhibiting Nrf2 using all-trans retinoic acid (ATRA) or by knock down approach prior to radiation exposure (4 Gy). DNA damage and repair analysis was studied by γH2AX foci formation and comet assay. Results suggested that the inhibition of Nrf2 in A549 or MCF7 cells led to significant slowdown in DNA repair as compared to respective radiation controls. The persistence of residual DNA damage even in the presence of free radical scavenger N-acetyl cysteine, suggested that the influence of Nrf2 on DNA repair was not linked to its antioxidant functions. Further, its influence on non-homologous end joining repair pathway was studied by inhibiting both Nrf2 and DNA-PK together. This led to synergistic reduction of survival fraction, indicating that Nrf2 may not be influencing the NHEJ pathway. To investigate the role of homologous recombination repair (HR) pathway, RAD51 foci formation was monitored. There was a significant reduction in the foci formation in cells treated with ATRA or shRNA against Nrf2 as compared to their respective radiation controls. Further, Nrf2 inhibition led to significant reduction in mRNA levels of RAD51. BLAST analysis was also performed on upstream regions of DNA repair genes to identify antioxidant response element and found that many repair genes that are involved in HR pathway may be regulated by Nrf2. Together, these results suggest the involvement of Nrf2 in DNA repair, a hitherto unknown function of Nrf2, putatively through its influence on HR pathway.
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Affiliation(s)
- Sundarraj Jayakumar
- Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - Debojyoti Pal
- Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - Santosh K Sandur
- Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
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130
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Enns L, Rasouli-Nia A, Hendzel M, Marples B, Weinfeld M. Association of ATM activation and DNA repair with induced radioresistance after low-dose irradiation. RADIATION PROTECTION DOSIMETRY 2015; 166:131-6. [PMID: 25904696 PMCID: PMC4572139 DOI: 10.1093/rpd/ncv203] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Mammalian cells often exhibit a hyper-radiosensitivity (HRS) to radiation doses <20 cGy, followed by increased radioresistance (IRR) at slightly higher doses (∼20-30 cGy). Here, the influence of DNA double-strand break repair (DSBR) on IRR was examined. The failure of Ataxia telangiectasia (AT) cells to undergo IRR reported by others was confirmed. Flow cytometric analysis indicated that normal cells fail to show a measurable increase in serine 1981 phosphorylated AT-mutated (ATM) protein after 10 cGy up to 4 h post irradiation, but a two- to fourfold increase after 25 cGy. Similarly, more proficient reduction of phosphorylated histone H2AX was observed 24 h after 25 cGy than after 10 cGy, suggesting that DSBR is more efficient during IRR than HRS. A direct examination of the consequences of inefficient DNA repair per se (as opposed to ATM-mediated signal transduction/cell cycle responses), by determining the clonogenic survival of cells lacking the DNA repair enzyme polynucleotide kinase/phosphatase, indicated that these cells have a response similar to AT cells, i.e. HRS but no IRR, strongly linking IRR to DSBR.
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Affiliation(s)
- L Enns
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, Alberta T6G 1Z2, Canada
| | - A Rasouli-Nia
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, Alberta T6G 1Z2, Canada
| | - M Hendzel
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, Alberta T6G 1Z2, Canada
| | - B Marples
- Department of Radiation Oncology, William Beaumont Hospital, 3811 W. Thirteen Mile Rd., 105-RI, Royal Oak, MI 48073, USA
| | - M Weinfeld
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, Alberta T6G 1Z2, Canada
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131
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Hartlerode AJ, Morgan MJ, Wu Y, Buis J, Ferguson DO. Recruitment and activation of the ATM kinase in the absence of DNA-damage sensors. Nat Struct Mol Biol 2015; 22:736-43. [PMID: 26280532 PMCID: PMC4560612 DOI: 10.1038/nsmb.3072] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 07/22/2015] [Indexed: 12/26/2022]
Abstract
Two kinases, ATM and DNA-PKcs, control rapid responses to DNA double-strand breaks (DSBs). The paradigm for ATM control is recruitment and activation by the Mre11-Rad50-NBS1 (MRN) sensor complex, whereas DNA-PKcs requires the sensor Ku (Ku70-Ku80). Using mouse cells containing targeted mutant alleles of Mre11 (Mre11a) and/or Ku70 (Xrcc6), together with pharmacologic kinase inhibition, we demonstrate that ATM can be activated by DSBs in the absence of MRN. When MRN is deficient, DNA-PKcs efficiently substitutes for ATM in facilitating local chromatin responses. In the absence of both MRN and Ku, ATM is recruited to chromatin, where it phosphorylates H2AX and triggers the G2-M cell-cycle checkpoint, but the DNA-repair functions of MRN are not restored. These results suggest that, in contrast to straightforward recruitment and activation by MRN, a complex interplay between sensors has a substantial role in ATM control.
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Affiliation(s)
- Andrea J. Hartlerode
- Department of Pathology, The University of Michigan Medical School, Ann Arbor, MI 48109. USA
| | - Mary J. Morgan
- Department of Pathology, The University of Michigan Medical School, Ann Arbor, MI 48109. USA
| | - Yipin Wu
- Department of Pathology, The University of Michigan Medical School, Ann Arbor, MI 48109. USA
| | - Jeffrey Buis
- Department of Pathology, The University of Michigan Medical School, Ann Arbor, MI 48109. USA
| | - David O. Ferguson
- Department of Pathology, The University of Michigan Medical School, Ann Arbor, MI 48109. USA
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132
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Miyata S, Fukuda Y, Tojima H, Matsuzaki K, Kitanaka S, Sawada H. Mechanism of the inhibition of leukemia cell growth and induction of apoptosis through the activation of ATR and PTEN by the topoisomerase inhibitor 3EZ, 20Ac-ingenol. Leuk Res 2015. [DOI: 10.1016/j.leukres.2015.06.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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133
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Zhong HZ, Lv FT, Deng XL, Hu Y, Xie DN, Lin B, Mo ZN, Lin FQ. Evaluating γH2AX in spermatozoa from male infertility patients. Fertil Steril 2015; 104:574-81. [PMID: 26158906 DOI: 10.1016/j.fertnstert.2015.06.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 06/03/2015] [Accepted: 06/04/2015] [Indexed: 01/07/2023]
Abstract
OBJECTIVE To investigate whether γH2AX levels were different in the spermatozoa of healthy men compared with infertility patients, and to assess the possible correlations between γH2AX and conventional semen parameters and double-stranded breaks (DSBs) identified with the use of comet assay. DESIGN Prospective study. SETTING Clinical laboratory. PATIENT(S) Semen from 100 male infertile patients and 100 healthy sperm donors. INTERVENTION(S) Human sperm samples were analyzed in terms of World Health Organization parameters. The γH2AX levels were detected by means of flow cytometry. DSBs of sperm were detected by means of comet assay. Morphology slides were made and the sperm morphology assessed according to strict criteria. MAIN OUTCOME MEASURE(S) Conventional semen analyses, γH2AX levels in sperm, DNA DSBs in sperm, and correlations among γH2AX, conventional semen analyses, and DSBs. RESULT(S) Concentration, viability, motility, and normal sperm morphology were significantly lower in male infertility patients compared with healthy men. Also, γH2AX levels and the number of DSBs were significantly higher in the sperm of infertile subjects compared with healthy men. γH2AX levels correlated negatively with conventional semen parameters and positively with DSBs. A threshold γH2AX level of 18.55% was identified as a cutoff value to discriminate infertile subjects from fertile control subjects with a specificity of 86.0% and a sensitivity of 83.0%. The positive and negative predictive values of the 18.55% γH2AX threshold were high: 87.7% and 85.5%, respectively. CONCLUSION(S) γH2AX levels were higher in the sperm of male infertility patients than in healthy men. γH2AX levels in sperm, as evaluated with the use of flow cytometry, might be a useful biomarker for evaluating DSBs in human spermatozoa.
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Affiliation(s)
- Hui-zhi Zhong
- First Affiliated Hospital of Guangxi Medical University, Guangxi, People's Republic of China
| | - Fu-tong Lv
- Research Center for Population and Family Planning of Guangxi Zhuang Autonomous Region, Guangxi, People's Republic of China
| | - Xue-lian Deng
- First Affiliated Hospital of Guangxi Medical University, Guangxi, People's Republic of China
| | - Ying Hu
- First Affiliated Hospital of Guangxi Medical University, Guangxi, People's Republic of China
| | - Dan-ni Xie
- Research Center for Population and Family Planning of Guangxi Zhuang Autonomous Region, Guangxi, People's Republic of China
| | - Bin Lin
- First Affiliated Hospital of Guangxi Medical University, Guangxi, People's Republic of China
| | - Zeng-nan Mo
- First Affiliated Hospital of Guangxi Medical University, Guangxi, People's Republic of China
| | - Fa-quan Lin
- First Affiliated Hospital of Guangxi Medical University, Guangxi, People's Republic of China.
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134
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Hollingworth R, Skalka GL, Stewart GS, Hislop AD, Blackbourn DJ, Grand RJ. Activation of DNA Damage Response Pathways during Lytic Replication of KSHV. Viruses 2015; 7:2908-27. [PMID: 26057167 PMCID: PMC4488719 DOI: 10.3390/v7062752] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 05/29/2015] [Accepted: 05/29/2015] [Indexed: 01/03/2023] Open
Abstract
Kaposi’s sarcoma-associated herpesvirus (KSHV) is the causative agent of several human malignancies. Human tumour viruses such as KSHV are known to interact with the DNA damage response (DDR), the molecular pathways that recognise and repair lesions in cellular DNA. Here it is demonstrated that lytic reactivation of KSHV leads to activation of the ATM and DNA-PK DDR kinases resulting in phosphorylation of multiple downstream substrates. Inhibition of ATM results in the reduction of overall levels of viral replication while inhibition of DNA-PK increases activation of ATM and leads to earlier viral release. There is no activation of the ATR-CHK1 pathway following lytic replication and CHK1 phosphorylation is inhibited at later times during the lytic cycle. Despite evidence of double-strand breaks and phosphorylation of H2AX, 53BP1 foci are not consistently observed in cells containing lytic virus although RPA32 and MRE11 localise to sites of viral DNA synthesis. Activation of the DDR following KSHV lytic reactivation does not result in a G1 cell cycle block and cells are able to proceed to S-phase during the lytic cycle. KSHV appears then to selectively activate DDR pathways, modulate cell cycle progression and recruit DDR proteins to sites of viral replication during the lytic cycle.
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Affiliation(s)
- Robert Hollingworth
- School of Cancer Sciences, the College of Medicine and Dentistry, University of Birmingham, Birmingham B15 2TT, UK.
| | - George L Skalka
- School of Cancer Sciences, the College of Medicine and Dentistry, University of Birmingham, Birmingham B15 2TT, UK.
| | - Grant S Stewart
- School of Cancer Sciences, the College of Medicine and Dentistry, University of Birmingham, Birmingham B15 2TT, UK.
| | - Andrew D Hislop
- School of Cancer Sciences, the College of Medicine and Dentistry, University of Birmingham, Birmingham B15 2TT, UK.
| | - David J Blackbourn
- School of Biosciences and Medicine, University of Surrey, Surrey GU2 7XH, UK.
| | - Roger J Grand
- School of Cancer Sciences, the College of Medicine and Dentistry, University of Birmingham, Birmingham B15 2TT, UK.
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135
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Cheng Y, Kiess AP, Herman JM, Pomper MG, Meltzer SJ, Abraham JM. Phosphorus-32, a clinically available drug, inhibits cancer growth by inducing DNA double-strand breakage. PLoS One 2015; 10:e0128152. [PMID: 26030880 PMCID: PMC4450878 DOI: 10.1371/journal.pone.0128152] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 04/22/2015] [Indexed: 12/16/2022] Open
Abstract
Radioisotopes that emit electrons (beta particles), such as radioiodine, can effectively kill target cells, including cancer cells. Aqueous 32P[PO4] is a pure beta-emitter that has been used for several decades to treat non-malignant human myeloproliferative diseases. 32P[PO4] was directly compared to a more powerful pure beta-emitter, the clinically important 90Y isotope. In vitro, 32P[PO4] was more effective at killing cells than was the more powerful isotope 90Y (P ≤ 0.001) and also caused substantially more double-stranded DNA breaks than did 90Y. In vivo, a single low-dose intravenous dose of aqueous elemental 32P significantly inhibited tumor growth in the syngeneic murine cancer model (P ≤ 0.001). This effect is exerted by direct incorporation into nascent DNA chains, resulting in double-stranded breakage, a unique mechanism not duplicatable by other, more powerful electron-emitting radioisotopes. 32P[PO4] should be considered for human clinical trials as a potential novel anti-cancer drug.
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Affiliation(s)
- Yulan Cheng
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Ana P. Kiess
- Department of Radiation Oncology and Molecular Radiation, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Joseph M. Herman
- Department of Radiation Oncology and Molecular Radiation, The Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Martin G. Pomper
- Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Stephen J. Meltzer
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
| | - John M. Abraham
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
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136
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Ghule PN, Xie RL, Colby JL, Jones SN, Lian JB, Wijnen AJV, Stein JL, Stein GS. p53 checkpoint ablation exacerbates the phenotype of Hinfp dependent histone H4 deficiency. Cell Cycle 2015; 14:2501-8. [PMID: 26030398 DOI: 10.1080/15384101.2015.1049783] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Histone Nuclear Factor P (HINFP) is essential for expression of histone H4 genes. Ablation of Hinfp and consequential depletion of histones alter nucleosome spacing and cause stalled replication and DNA damage that ultimately result in genomic instability. Faithful replication and packaging of newly replicated DNA are required for normal cell cycle control and proliferation. The tumor suppressor protein p53, the guardian of the genome, controls multiple cell cycle checkpoints and its loss leads to cellular transformation. Here we addressed whether the absence of p53 impacts the outcomes/consequences of Hinfp-mediated histone H4 deficiency. We examined mouse embryonic fibroblasts lacking both Hinfp and p53. Our data revealed that the reduced histone H4 expression caused by depletion of Hinfp persists when p53 is also inactivated. Loss of p53 enhanced the abnormalities in nuclear shape and size (i.e. multi-lobed irregularly shaped nuclei) caused by Hinfp depletion and also altered the sub-nuclear organization of Histone Locus Bodies (HLBs). In addition to the polyploid phenotype resulting from deletion of either p53 or Hinfp, inactivation of both p53 and Hinfp increased mitotic defects and generated chromosomal fragility and susceptibility to DNA damage. Thus, our study conclusively establishes that simultaneous loss of both Hinfp and the p53 checkpoint is detrimental to normal cell growth and may predispose to cellular transformation.
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Affiliation(s)
- Prachi N Ghule
- a Department of Biochemistry and University of Vermont Cancer Center ; University of Vermont College of Medicine ; Burlington , VT USA
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137
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Lieberman R, Xiong D, James M, Han Y, Amos CI, Wang L, You M. Functional characterization of RAD52 as a lung cancer susceptibility gene in the 12p13.33 locus. Mol Carcinog 2015; 55:953-63. [PMID: 26013599 DOI: 10.1002/mc.22334] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 03/27/2015] [Accepted: 04/21/2015] [Indexed: 11/11/2022]
Abstract
Recent genome-wide association studies have identified variations in the recombination repair gene, RAD52, that are associated with increased lung cancer risk, and particularly with the development of lung squamous cell carcinomas (LUSC). As LUSC development is strongly associated with smoking, DNA repair is increased in the lung tissues of smokers, presumably because of ongoing DNA damage from exposure to tobacco smoke. A key player in the DNA damage response, RAD52 plays a role in DNA strand exchange and annealing during homologous recombination (HR) in mammalian cells. In this study, we discovered two cis-expression quantitative trait loci (eQTL) SNPs in the RAD52 gene that are associated with its expression and are also associated with LUSC risk. In addition, we report that amplification of the genomic region 12p13.33, which contains the RAD52 gene, is significantly associated with the development of LUSC in the TCGA database and that somatic overexpression of RAD52 was confirmed to be significant in LUSC tumors from our own patient cohort. Consistent with these genetic findings, we demonstrate that blockade of Rad52 slows cell growth and induces senescence in mouse bronchial epithelial cells. In contrast, overexpression of Rad52 leads to an increased rate of cell proliferation. We show that depletion of Rad52 in mouse lung tumor cells alters cell cycle distribution and increases DNA damage accumulation associated with increased tumor cell death. Our genetic and functional data implicate RAD52 as a significant determinant of risk in the development of LUSC.
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Affiliation(s)
- Rachel Lieberman
- Department of Pharmacology & Toxicology and Cancer Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Donghai Xiong
- Department of Pharmacology & Toxicology and Cancer Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Michael James
- Department of Pharmacology & Toxicology and Cancer Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Younghun Han
- Department of Community and Family Medicine, Geisel School of Medicine, Dartmouth College, Lebanon, New Hampshire
| | - Christopher I Amos
- Department of Community and Family Medicine, Geisel School of Medicine, Dartmouth College, Lebanon, New Hampshire
| | - Liang Wang
- Department of Pathology and Cancer Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Ming You
- Department of Pharmacology & Toxicology and Cancer Center, Medical College of Wisconsin, Milwaukee, Wisconsin
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138
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Modulation of DNA damage and repair pathways by human tumour viruses. Viruses 2015; 7:2542-91. [PMID: 26008701 PMCID: PMC4452920 DOI: 10.3390/v7052542] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 05/12/2015] [Indexed: 02/07/2023] Open
Abstract
With between 10% and 15% of human cancers attributable to viral infection, there is great interest, from both a scientific and clinical viewpoint, as to how these pathogens modulate host cell functions. Seven human tumour viruses have been identified as being involved in the development of specific malignancies. It has long been known that the introduction of chromosomal aberrations is a common feature of viral infections. Intensive research over the past two decades has subsequently revealed that viruses specifically interact with cellular mechanisms responsible for the recognition and repair of DNA lesions, collectively known as the DNA damage response (DDR). These interactions can involve activation and deactivation of individual DDR pathways as well as the recruitment of specific proteins to sites of viral replication. Since the DDR has evolved to protect the genome from the accumulation of deleterious mutations, deregulation is inevitably associated with an increased risk of tumour formation. This review summarises the current literature regarding the complex relationship between known human tumour viruses and the DDR and aims to shed light on how these interactions can contribute to genomic instability and ultimately the development of human cancers.
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139
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Elgart SR, Bostani M, Mok KC, Adibi A, Ruehm S, Enzmann D, McNitt-Gray M, Iwamoto KS. Investigation of DNA Damage Dose-Response Kinetics after Ionizing Radiation Schemes Similar to CT Protocols. Radiat Res 2015; 183:701-7. [PMID: 25950819 DOI: 10.1667/rr13752.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Although there has been extensive research done on the biological response to doses of ionizing radiation relevant to radiodiagnostic procedures, very few studies have examined radiation schemes similar to those frequently utilized in CT exams. Instead of a single exposure, CT exams are often made up of a series of scans separated on the order of minutes. DNA damage dose-response kinetics after radiation doses and schemes similar to CT protocols were established in both cultured (ESW-WT3) and whole blood lymphocytes and compared to higher dose exposures. Both the kinetics and extent of H2AX phosphorylation were found to be dose dependent. Damage induction and detection showed a clear dose response, albeit different, at all time points and differences in the DNA repair kinetics of ESW-WT3 and whole blood lymphocytes were characterized. Moreover, using a modified split-dose in vitro experiment, we show that phosphorylation of H2AX is significantly reduced after exposure to CT doses fractionated over a few minutes compared to the same total dose delivered as a single exposure. Because the split-dose exposures investigated here are more similar to those experienced during a CT examination, it is essential to understand why and how these differences occur. This work provides compelling evidence supporting differential biological responses not only between high and low doses, but also between single and multiple exposures to low doses of ionizing radiation.
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Affiliation(s)
| | - Maryam Bostani
- b Radiology, David Geffen School of Medicine at University of California, Los Angeles, California
| | | | - Ali Adibi
- b Radiology, David Geffen School of Medicine at University of California, Los Angeles, California
| | - Stefan Ruehm
- b Radiology, David Geffen School of Medicine at University of California, Los Angeles, California
| | - Dieter Enzmann
- b Radiology, David Geffen School of Medicine at University of California, Los Angeles, California
| | - Michael McNitt-Gray
- b Radiology, David Geffen School of Medicine at University of California, Los Angeles, California
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140
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Chen W, Hu GH. Biomarkers for enhancing the radiosensitivity of nasopharyngeal carcinoma. Cancer Biol Med 2015; 12:23-32. [PMID: 25859408 PMCID: PMC4383846 DOI: 10.7497/j.issn.2095-3941.2014.0015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Accepted: 01/07/2015] [Indexed: 12/14/2022] Open
Abstract
Nasopharyngeal carcinoma (NPC) is a common head and neck malignancy. The incidence of NPC is higher in Southern China and Southeast Asia compared with Western countries. Given its high radiosensitivity, the standard treatment for NPC is radiotherapy. However, radioresistance remains a serious obstacle to successful treatment. Radioresistance can cause local recurrence and distant metastases in some patients after treatment by radiation. Thus, special emphasis has been given to the discovery of effective radiosensitizers. This review aims to discuss the biomarkers, classified according to the main mechanisms of radiosensitization, which can enhance the sensitivity of NPC cells to ionizing radiation.
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Affiliation(s)
- Wei Chen
- Department of Otorhinolaryngology, the First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China
| | - Guo-Hua Hu
- Department of Otorhinolaryngology, the First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China
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141
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Weiss CN, Ito K. DNA damage: a sensible mediator of the differentiation decision in hematopoietic stem cells and in leukemia. Int J Mol Sci 2015; 16:6183-201. [PMID: 25789504 PMCID: PMC4394526 DOI: 10.3390/ijms16036183] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 03/04/2015] [Accepted: 03/09/2015] [Indexed: 12/30/2022] Open
Abstract
In the adult, the source of functionally diverse, mature blood cells are hematopoietic stem cells, a rare population of quiescent cells that reside in the bone marrow niche. Like stem cells in other tissues, hematopoietic stem cells are defined by their ability to self-renew, in order to maintain the stem cell population for the lifetime of the organism, and to differentiate, in order to give rise to the multiple lineages of the hematopoietic system. In recent years, increasing evidence has suggested a role for the accumulation of reactive oxygen species and DNA damage in the decision for hematopoietic stem cells to exit quiescence and to differentiate. In this review, we will examine recent work supporting the idea that detection of cell stressors, such as oxidative and genetic damage, is an important mediator of cell fate decisions in hematopoietic stem cells. We will explore the benefits of such a system in avoiding the development and progression of malignancies, and in avoiding tissue exhaustion and failure. Additionally, we will discuss new work that examines the accumulation of DNA damage and replication stress in aging hematopoietic stem cells and causes us to rethink ideas of genoprotection in the bone marrow niche.
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Affiliation(s)
- Cary N Weiss
- Ruth L. and David S. Gottesman Institute for Stem Cell and Regenerative Medicine Research, Departments of Cell Biology/Stem Cell Institute and Medicine, Albert Einstein Cancer Center and Diabetes Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Keisuke Ito
- Ruth L. and David S. Gottesman Institute for Stem Cell and Regenerative Medicine Research, Departments of Cell Biology/Stem Cell Institute and Medicine, Albert Einstein Cancer Center and Diabetes Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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142
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Li X, Nan A, Xiao Y, Chen Y, Lai Y. PP2A-B56ϵ complex is involved in dephosphorylation of γ-H2AX in the repair process of CPT-induced DNA double-strand breaks. Toxicology 2015; 331:57-65. [PMID: 25772433 DOI: 10.1016/j.tox.2015.03.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 02/25/2015] [Accepted: 03/11/2015] [Indexed: 10/23/2022]
Abstract
Phosphorylation of histone H2AX (γ-H2AX) in response to DNA double-strand breaks (DSBs) should be eliminated from the sites of DNA damage to fulfill the DNA repair and release cells from the growth arrest. Previous study showed that protein phosphatase 2A (PP2A) interact with γ-H2AX that lead to the dephosphorylation of γ-H2AX. Here, we examined the effects of suppression of PP2A regulatory subunits on dephosphorylation of γ-H2AX in human embryonic kidney epithelial cells (HEK) treated by topoisomerase I inhibitor camptothecin (CPT). We found that cells with suppression of B55α or B56ϵ were more sensitive to DNA damage agents. Suppression of B56ϵ led to persistence of γ-H2AX, resulting in prolonged DSBs repair and increased chromatin instability measured by comet assay. In addition, the deficiency of B56ϵ impaired the cell cycle regulation and the DNA repair pathway of homologous recombination (HR). Notably, we detected that PP2A B56ϵ subunit was involved directly in dephosphorylation of γ-H2AX and translocated from cytoplasm to nucleus upon the treatment of CPT. Our findings demonstrate that PP2A holoenzyme containing B56ϵ is responsible for the dephosphorylation of γ-H2AX and regulation of DNA repair of DSBs induced by CPT.
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Affiliation(s)
- Xiuying Li
- Institute for Chemical Carcinogenesis, Guangzhou Medical University, Guangzhou 510182, China; College of Pharmacy, Jinan University, Guangzhou 510632, China
| | - Anuo Nan
- Institute for Chemical Carcinogenesis, Guangzhou Medical University, Guangzhou 510182, China
| | - Ying Xiao
- College of Pharmacy, Jinan University, Guangzhou 510632, China
| | - Yongzhong Chen
- Institute for Chemical Carcinogenesis, Guangzhou Medical University, Guangzhou 510182, China
| | - Yandong Lai
- Institute for Chemical Carcinogenesis, Guangzhou Medical University, Guangzhou 510182, China.
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143
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Xiong X, Du Z, Wang Y, Feng Z, Fan P, Yan C, Willers H, Zhang J. 53BP1 promotes microhomology-mediated end-joining in G1-phase cells. Nucleic Acids Res 2015; 43:1659-70. [PMID: 25586219 PMCID: PMC4330367 DOI: 10.1093/nar/gku1406] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Alternative non-homologous end joining (alt-NHEJ) was originally identified as a backup repair mechanism in the absence of classical NHEJ (c-NHEJ) factors but recent studies have demonstrated that alt-NHEJ is active even when c-NHEJ as well as homologous recombination is available. The functions of 53BP1 in NHEJ processes are not well understood. Here, we report that 53BP1 promotes DNA double-strand break (DSB) repair and genomic stability not only in c-NHEJ-proficient but also -deficient human G1-phase cells. Using an array of repair substrates we show that these effects of 53BP1 are correlated with a promotion of microhomology-mediated end-joining (MMEJ), a subtype of alt-NHEJ, in G1-phase. Consistent with a specific role in MMEJ we confirm that 53BP1 status does not affect c-NHEJ. 53BP1 supports sequence deletion during MMEJ consistent with a putative role in facilitating end-resection. Interestingly, promotion of MMEJ by 53BP1 in G1-phase cells is only observed in the presence of functional BRCA1. Depletion of both 53BP1 and BRCA1 increases repair needing microhomology usage and augments loss of DNA sequence, suggesting that MMEJ is a highly regulated DSB repair process. Together, these findings significantly expand our understanding of the cell-cycle-dependent roles of 53BP1 in DSB repair.
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Affiliation(s)
- Xiahui Xiong
- Department of Radiation Oncology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, BRB 323, Cleveland, OH 44106, USA
| | - Zhanwen Du
- Department of Radiation Oncology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, BRB 323, Cleveland, OH 44106, USA
| | - Ying Wang
- Department of Radiation Oncology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, BRB 323, Cleveland, OH 44106, USA
| | - Zhihui Feng
- Department of Radiation Oncology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, BRB 323, Cleveland, OH 44106, USA
| | - Pan Fan
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine,1650 Orleans Street, Baltimore, MD 21231, USA
| | - Chunhong Yan
- Department of Biochemistry and Molecular Biology, Georgia Regents University, 1410 Laney Walker Blvd., CN-2134, Augusta, GA 30912, USA
| | - Henning Willers
- Department of Radiation Oncology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
| | - Junran Zhang
- Department of Radiation Oncology, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, BRB 323, Cleveland, OH 44106, USA
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144
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Tong Q, Cui G, Botuyan MV, Rothbart SB, Hayashi R, Musselman CA, Singh N, Appella E, Strahl BD, Mer G, Kutateladze TG. Structural plasticity of methyllysine recognition by the tandem tudor domain of 53BP1. Structure 2015; 23:312-21. [PMID: 25579814 DOI: 10.1016/j.str.2014.11.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 11/11/2014] [Accepted: 11/13/2014] [Indexed: 11/29/2022]
Abstract
p53 is dynamically regulated through various posttranslational modifications (PTMs), which differentially modulate its function and stability. The dimethylated marks p53K370me2 and p53K382me2 are associated with p53 activation or stabilization and both are recognized by the tandem Tudor domain (TTD) of 53BP1, a p53 cofactor. Here we detail the molecular mechanisms for the recognition of p53K370me2 and p53K382me2 by 53BP1. The solution structures of TTD in complex with the p53K370me2 and p53K382me2 peptides show a remarkable plasticity of 53BP1 in accommodating these diverse dimethyllysine-containing sequences. We demonstrate that dimeric TTDs are capable of interacting with the two PTMs on a single p53K370me2K382me2 peptide, greatly strengthening the 53BP1-p53 interaction. Analysis of binding affinities of TTD toward methylated p53 and histones reveals strong preference of 53BP1 for p53K382me2, H4K20me2, and H3K36me2 and suggests a possible role of multivalent contacts of 53BP1 in p53 targeting to and accumulation at the sites of DNA damage.
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Affiliation(s)
- Qiong Tong
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Gaofeng Cui
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| | | | - Scott B Rothbart
- Department of Biochemistry and Biophysics and the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Ryo Hayashi
- Laboratory of Cell Biology, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Catherine A Musselman
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Namit Singh
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| | - Ettore Appella
- Laboratory of Cell Biology, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Brian D Strahl
- Department of Biochemistry and Biophysics and the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
| | - Georges Mer
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA.
| | - Tatiana G Kutateladze
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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145
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Laurent A, Blasi F. Differential DNA damage signalling and apoptotic threshold correlate with mouse epiblast-specific hypersensitivity to radiation. Development 2015; 142:3675-85. [DOI: 10.1242/dev.125708] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 09/08/2015] [Indexed: 12/31/2022]
Abstract
Between implantation and gastrulation, the mouse pluripotent epiblast cells expand enormously and exhibit a remarkable hypersensitivity to DNA damage. Upon low dose irradiation, they undergo mitotic arrest followed by p53-dependent apoptosis, while the other cell types simply arrest. This protective mechanism, active exclusively after e5.5 and lost during gastrulation, ensures the elimination of every mutated cell before its clonal expansion, and is therefore expected to greatly increase individuals' fitness.
We show that the insurgence of apoptosis relies on the epiblast-specific convergence of both increased DNA damage signalling and stronger pro-apoptotic balance. Although upstream Atm/Atr global activity and specific γH2AX phosphorylation are similar in all cell types of the embryo, 53BP1 recruitment at DNA breaks is immediately amplified only in epiblast cells after ionizing radiation. This correlates with a rapid epiblast-specific activation of p53 and its transcriptional properties. Moreover, between e5.5 and e6.5, epiblast cells lower their apoptotic threshold by overexpressing pro-apoptotic Bak and Bim and repressing the anti-apoptotic Bcl-xL. Thus even after low dose irradiation, the cytoplasmic priming of epiblast cells allows p53 to rapidly induce apoptosis via a partially transcription-independent mechanism.
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Affiliation(s)
- Audrey Laurent
- IFOM (FIRC Institute of Molecular Oncology), IFOM-IEO-Campus, Via Adamello 16, Milan, Italy
| | - Francesco Blasi
- IFOM (FIRC Institute of Molecular Oncology), IFOM-IEO-Campus, Via Adamello 16, Milan, Italy
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146
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Fidelity of histone gene regulation is obligatory for genome replication and stability. Mol Cell Biol 2014; 34:2650-9. [PMID: 24797072 DOI: 10.1128/mcb.01567-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fidelity of chromatin organization is crucial for normal cell cycle progression, and perturbations in packaging of DNA may predispose to transformation. Histone H4 protein is the most highly conserved chromatin protein, required for nucleosome assembly, with multiple histone H4 gene copies encoding identical protein. There is a long-standing recognition of the linkage of histone gene expression and DNA replication. A fundamental and unresolved question is the mechanism that couples histone biosynthesis with DNA replication and fidelity of cell cycle control. Here, we conditionally ablated the obligatory histone H4 transcription factor HINFP to cause depletion of histone H4 in mammalian cells. Deregulation of histone H4 results in catastrophic cellular and molecular defects that lead to genomic instability. Histone H4 depletion increases nucleosome spacing, impedes DNA synthesis, alters chromosome complement, and creates replicative stress. Our study provides functional evidence that the tight coupling between DNA replication and histone synthesis is reciprocal.
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147
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Coster G, Goldberg M. The cellular response to DNA damage: A focus on MDC1 and its interacting proteins. Nucleus 2014. [DOI: 10.4161/nucl.11176] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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148
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Gonzalo S. Novel roles of 1α,25(OH)2D3 on DNA repair provide new strategies for breast cancer treatment. J Steroid Biochem Mol Biol 2014; 144 Pt A:59-64. [PMID: 24080249 PMCID: PMC3968232 DOI: 10.1016/j.jsbmb.2013.09.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 09/16/2013] [Accepted: 09/20/2013] [Indexed: 12/11/2022]
Abstract
Breast cancers classified as triple-negative (TNBC) and BRCA1-deficient, are particularly aggressive and difficult to treat. A major breakthrough was the finding that these tumors are exquisitely sensitive to inhibitors of poly(ADP-ribose) polymerase (PARPi). Phase II clinical trials have shown encouraging outcomes, with tolerable side effects. However, a significant fraction of these cancers acquire resistance. Elegant studies demonstrated that loss of the DNA repair protein 53BP1 contributes to the resistance of BRCA1-deficient cells and tumors to PARPi. Thus, raising the levels of 53BP1 in these aggressive tumors could potentially restore their sensitivity to PARPi and other genotoxic agents. We will review here our studies revealing that 1α,25(OH)2D3, an active form of vitamin D, stabilizes 53BP1 levels in tumor cells. Breast tumor cells that become BRCA1-deficient activate cathepsin L-mediated degradation of 53BP1 to ensure genome stability and proliferation. Importantly, 1α,25(OH)2D3 treatment restores the levels of 53BP1 as efficiently as cathepsin L inhibitors, which results in increased genomic instability in response to PARPi or radiation, and reduced proliferation. Furthermore, analysis of human breast tumors identified nuclear cathepsin L as a positive biomarker for TNBC, which correlates inversely with 53BP1 when vitamin D receptor (VDR) nuclear levels are low. The major findings of these studies are: (1) identification of a new pathway contributing to breast cancers with the poorest prognosis; (2) discovery of the ability of 1α,25(OH)2D3 to inhibit this pathway; and (3) discovery of a triple biomarker signature for identification of patients that could benefit from the treatment. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.
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Affiliation(s)
- Susana Gonzalo
- Edward A. Doisy Department of Biochemistry and Molecular Biology, St Louis University School of Medicine, St. Louis, MO 63104, USA.
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149
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Liu T, Huang J. Quality control of homologous recombination. Cell Mol Life Sci 2014; 71:3779-97. [PMID: 24858417 PMCID: PMC11114062 DOI: 10.1007/s00018-014-1649-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 05/09/2014] [Indexed: 12/21/2022]
Abstract
Exogenous and endogenous genotoxic agents, such as ionizing radiation and numerous chemical agents, cause DNA double-strand breaks (DSBs), which are highly toxic and lead to genomic instability or tumorigenesis if not repaired accurately and efficiently. Cells have over evolutionary time developed certain repair mechanisms in response to DSBs to maintain genomic integrity. Major DSB repair mechanisms include non-homologous end joining and homologous recombination (HR). Using sister homologues as templates, HR is a high-fidelity repair pathway that can rejoin DSBs without introducing mutations. However, HR execution without appropriate guarding may lead to more severe gross genome rearrangements. Here we review current knowledge regarding the factors and mechanisms required for accomplishment of accurate HR.
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Affiliation(s)
- Ting Liu
- Life Sciences Institute, Zhejiang University, Hangzhou, 310058 Zhejiang China
| | - Jun Huang
- Life Sciences Institute, Zhejiang University, Hangzhou, 310058 Zhejiang China
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