1
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Amoiridis M, Verigos J, Meaburn K, Gittens WH, Ye T, Neale MJ, Soutoglou E. Inhibition of topoisomerase 2 catalytic activity impacts the integrity of heterochromatin and repetitive DNA and leads to interlinks between clustered repeats. Nat Commun 2024; 15:5727. [PMID: 38977669 PMCID: PMC11231352 DOI: 10.1038/s41467-024-49816-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 06/14/2024] [Indexed: 07/10/2024] Open
Abstract
DNA replication and transcription generate DNA supercoiling, which can cause topological stress and intertwining of daughter chromatin fibers, posing challenges to the completion of DNA replication and chromosome segregation. Type II topoisomerases (Top2s) are enzymes that relieve DNA supercoiling and decatenate braided sister chromatids. How Top2 complexes deal with the topological challenges in different chromatin contexts, and whether all chromosomal contexts are subjected equally to torsional stress and require Top2 activity is unknown. Here we show that catalytic inhibition of the Top2 complex in interphase has a profound effect on the stability of heterochromatin and repetitive DNA elements. Mechanistically, we find that catalytically inactive Top2 is trapped around heterochromatin leading to DNA breaks and unresolved catenates, which necessitate the recruitment of the structure specific endonuclease, Ercc1-XPF, in an SLX4- and SUMO-dependent manner. Our data are consistent with a model in which Top2 complex resolves not only catenates between sister chromatids but also inter-chromosomal catenates between clustered repetitive elements.
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Affiliation(s)
- Michalis Amoiridis
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, BN1 9RH, UK
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, Illkirch, France
- Centre National de Recherche Scientifique (CNRS), UMR7104, Illkirch, France
- Université de Strasbourg, Illkirch, France
| | - John Verigos
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, BN1 9RH, UK
| | - Karen Meaburn
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, BN1 9RH, UK
| | - William H Gittens
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, BN1 9RH, UK
| | - Tao Ye
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, Illkirch, France
- Centre National de Recherche Scientifique (CNRS), UMR7104, Illkirch, France
- Université de Strasbourg, Illkirch, France
| | - Matthew J Neale
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, BN1 9RH, UK
| | - Evi Soutoglou
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, BN1 9RH, UK.
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2
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Kelly RD, Parmar G, Bayat L, Maitland MER, Lajoie GA, Edgell DR, Schild-Poulter C. Noncanonical functions of Ku may underlie essentiality in human cells. Sci Rep 2023; 13:12162. [PMID: 37500706 PMCID: PMC10374653 DOI: 10.1038/s41598-023-39166-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 07/20/2023] [Indexed: 07/29/2023] Open
Abstract
The Ku70/80 heterodimer is a key player in non-homologous end-joining DNA repair but is involved in other cellular functions like telomere regulation and maintenance, in which Ku's role is not fully characterized. It was previously reported that knockout of Ku80 in a human cell line results in lethality, but the underlying cause of Ku essentiality in human cells has yet to be fully explored. Here, we established conditional Ku70 knockout cells using CRISPR/Cas9 editing to study the essentiality of Ku70 function. While we observed loss of cell viability upon Ku depletion, we did not detect significant changes in telomere length, nor did we record lethal levels of DNA damage upon loss of Ku. Analysis of global proteome changes following Ku70 depletion revealed dysregulations of several cellular pathways including cell cycle/mitosis, RNA related processes, and translation/ribosome biogenesis. Our study suggests that the driving cause of loss of cell viability in Ku70 knockouts is not linked to the functions of Ku in DNA repair or at telomeres. Moreover, our data shows that loss of Ku affects multiple cellular processes and pathways and suggests that Ku plays critical roles in cellular processes beyond DNA repair and telomere maintenance to maintain cell viability.
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Affiliation(s)
- Rachel D Kelly
- Department of Biochemistry, Western University, London, ON, Canada
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
| | - Gursimran Parmar
- Department of Biochemistry, Western University, London, ON, Canada
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
| | - Laila Bayat
- Department of Biochemistry, Western University, London, ON, Canada
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
| | - Matthew E R Maitland
- Department of Biochemistry, Western University, London, ON, Canada
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada
| | - Gilles A Lajoie
- Department of Biochemistry, Western University, London, ON, Canada
| | - David R Edgell
- Department of Biochemistry, Western University, London, ON, Canada
| | - Caroline Schild-Poulter
- Department of Biochemistry, Western University, London, ON, Canada.
- Robarts Research Institute, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada.
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3
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Liu Z, Xiao J, Wang N, Ding J. LSD1 regulates the FOXF2-mediated Wnt/β-catenin signaling pathway by interacting with Ku80 to promote colon cancer progression. Am J Cancer Res 2022; 12:3693-3712. [PMID: 36119820 PMCID: PMC9442015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Accepted: 06/18/2022] [Indexed: 06/15/2023] Open
Abstract
Lysine-specific demethylase 1 (LSD1) is widely involved in the proliferation, invasion, and metastasis of cancers. However, it is uncertain whether LSD1 plays a role in facilitating colon cancer progression. Here, we have clarified the molecular mechanism by which LSD1 interacts with X-ray repair cross complementing protein 5 (Ku80) to promote colon cancer progression by directly targeting forehead protein transcription factor 2 (FOXF2). First, the interacting proteins of LSD1 were identified by immunoprecipitation and mass spectrometry. The expression of Ku80 and FOXF2 in colon cancer was detected using immunohistochemistry, real-time quantitative transcription polymerase chain reaction, and western blot. Next, the proliferation, invasion, and metastasis of colon cancer in vitro and in vivo were detected by methyl thiazolyl tetrazolium, 5-ethynyl-20-deoxyuridine, colony formation, wound healing, and nude mice xenograft model assays, respectively. Chromatin immunoprecipitation (ChIP) and ChIP-PCR were performed to investigate the molecular mechanism of LSD1 and Ku80 in colon cancer. Our results indicated that Ku80 expression was positively correlated with the invasion and migration of colon cancer cells, and negatively correlated with FOXF2 expression. More importantly, the high expression of Ku80 and the low expression of FOXF2 were particularly associated with driving the progression of colon cancer. Ku80 knockdown and LSD1 silencing inhibited the proliferation, migration, and invasion of colon cancer in vitro and in vivo. Mechanically, LSD1 interacts with Ku80 and also binds directly to the 687-887-bp portion of the FOXF2 promoter region. The upregulated methylation level of H3K4me2 in the FOXF2 promoter region facilitated the transcriptional activation of FOXF2, and downregulated protein expression associated with the Wnt/β-catenin signaling pathway. In conclusion, our study suggests that LSD1 regulates the FOXF2-mediated Wnt/β-catenin signaling pathway by interacting with Ku80, promoting the malignant biological properties of colon cancer, highlighting the binding of LSD1 and Ku80 as a useful anti-cancer target for colon cancer.
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Affiliation(s)
- Zhenhua Liu
- Department of Gastrointestinal Surgery, Guizhou Provincial People’s HospitalGuiyang 550004, Guizhou, China
- Medical College of Guizhou UniversityGuiyang 550004, Guizhou, China
| | - Jingjing Xiao
- Department of Gastrointestinal Surgery, Guizhou Provincial People’s HospitalGuiyang 550004, Guizhou, China
- Medical College of Guizhou UniversityGuiyang 550004, Guizhou, China
| | - Ning Wang
- Department of Pharmacy, Guizhou Provincial Orthopedic HospitalGuiyang 550002, Guizhou, China
| | - Jie Ding
- Department of Gastrointestinal Surgery, Guizhou Provincial People’s HospitalGuiyang 550004, Guizhou, China
- Medical College of Guizhou UniversityGuiyang 550004, Guizhou, China
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4
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Liu T, Jin L, Chen M, Zheng Z, Lu W, Fan W, Li L, Zheng F, Zhu Q, Qiu H, Liu J, Chen M, Tian C, Hu Z, Zhang C, Luo M, Li J, Kang T, Yang L, Li Y, Deng W. Ku80 promotes melanoma growth and regulates antitumor effect of melatonin by targeting HIF1-α dependent PDK-1 signaling pathway. Redox Biol 2019; 25:101197. [PMID: 31023624 PMCID: PMC6859552 DOI: 10.1016/j.redox.2019.101197] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2018] [Revised: 03/26/2019] [Accepted: 04/08/2019] [Indexed: 12/15/2022] Open
Abstract
Melanoma is one of the most malignant and aggressive cancers with high cancer-related deaths. However, it is unclear whether Ku80 regulates tumor growth in human melanoma. In this study, we screened a siRNA library targeting 6024 human genes and identified Ku80 as a potential therapeutic target in melanoma cells. Knockdown of Ku80 significantly suppressed melanoma cell proliferation and induced apoptosis, as well as enhanced the antitumor effect of melatonin in melanoma in vitro and in vivo. Overexpression of Ku80, however, promoted melanoma growth and increased the insensitivity of melanoma cells to melatonin. Mechanistically, we found that Ku80 bound to the PDK1 promoter and activated the transcription of PDK1. Moreover, we showed that the binding of Ku80 at the PDK-1 promoter was HIF1-α dependent, and melatonin degraded HIF1-α in melanoma cells. Furthermore, clinical data revealed that the expression of Ku80 and PDK-1 proteins were positively correlated and elevated in the tumor tissues of melanoma patients, and high expression of Ku80 predicted a poor prognosis in melanoma. Collectively, our study demonstrated that Ku80 promoted melanoma growth and regulated antitumor activity of melatonin by targeting HIF1-α dependent PDK-1 signaling pathway, suggesting that Ku80 may be a potential molecular target for melanoma treatment.
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Affiliation(s)
- Tianze Liu
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China; The Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai, Guangdong, China
| | - Lizi Jin
- The Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai, Guangdong, China
| | - Miao Chen
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Zongheng Zheng
- The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Wenjing Lu
- The Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai, Guangdong, China
| | - Wenhua Fan
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Liren Li
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Fufu Zheng
- The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Qiaohua Zhu
- Shunde Hospital, Southern Medical University, Foshan, China
| | - Huijuan Qiu
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Jiani Liu
- The Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai, Guangdong, China
| | - Manyu Chen
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Chunfang Tian
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Zheng Hu
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Changlin Zhang
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Meihua Luo
- Shunde Hospital, Southern Medical University, Foshan, China
| | - Jian Li
- The Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai, Guangdong, China
| | - Tiebang Kang
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China
| | - Lukun Yang
- The Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai, Guangdong, China.
| | - Yizhuo Li
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China.
| | - Wuguo Deng
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China.
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5
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Qi D, Hu Y, Li J, Peng T, Su J, He Y, Ji W. Hyperthermia Induces Apoptosis of 786-O Cells through Suppressing Ku80 Expression. PLoS One 2015; 10:e0122977. [PMID: 25902193 PMCID: PMC4406445 DOI: 10.1371/journal.pone.0122977] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 02/26/2015] [Indexed: 11/24/2022] Open
Abstract
Hyperthermia as an anticancer method has been paid increasing attention in recent years. Several studies have shown that hyperthermia can kill tumor cells by inducing apoptosis. However, the underlying molecular mechanisms of hyperthermia-induced apoptosis are largely unknown. To investigate the effects and molecular mechanism of hyperthermia on the apoptosis in renal carcinoma 786-O cells, we firstly examined apoptosis and Ku expression in 786-O cell line treated with heat exposure (42°C for 0-4 h). The results showed that hyperthermia induced apoptosis of 786-O cells, and suppressed significantly Ku80 expression, but not Ku70 expression. Next, we knock-down Ku80 in 786-O cells, generating stable cell line 786-O-shKu80, and detected apoptosis, cell survival and cell cycle distribution. Our data showed higher apoptotic rate and lower surviving fraction in the stable cell line 786-O-shKu80 compared with those in control cells, exposed to the same heat stress (42°C for 0-4 h). Moreover, the results also showed suppression of Ku80 led to G2/M phase arrest in the stable cell line 786-O-shKu80 following heat treatment. Together, these findings indicate that Ku80 may play an important role in hyperthermia-induced apoptosis and heat-sensitivity of renal carcinoma cells through influencing the cell cycle distribution.
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Affiliation(s)
- Defeng Qi
- Department of Urology, Minimally Invasive Surgery Center, The First Affiliated Hospital of Guangzhou Medical University, Guangdong Provincial Key Laboratory of Urology, Guangzhou, China
- * E-mail: (DQ); (YH); (WJ)
| | - Yuan Hu
- Department of Urology, Minimally Invasive Surgery Center, The First Affiliated Hospital of Guangzhou Medical University, Guangdong Provincial Key Laboratory of Urology, Guangzhou, China
| | - Jinhui Li
- Department of Urology, Minimally Invasive Surgery Center, The First Affiliated Hospital of Guangzhou Medical University, Guangdong Provincial Key Laboratory of Urology, Guangzhou, China
| | - Tao Peng
- Department of Urology, Minimally Invasive Surgery Center, The First Affiliated Hospital of Guangzhou Medical University, Guangdong Provincial Key Laboratory of Urology, Guangzhou, China
| | - Jialin Su
- Department of Urology, Minimally Invasive Surgery Center, The First Affiliated Hospital of Guangzhou Medical University, Guangdong Provincial Key Laboratory of Urology, Guangzhou, China
| | - Yun He
- School of public health, Sun Yat-sen University, Guangzhou, China
- * E-mail: (DQ); (YH); (WJ)
| | - Weidong Ji
- The center for translational medicine, The first affiliated hospital, Sun Yat-Sen University, Guangzhou, China
- * E-mail: (DQ); (YH); (WJ)
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6
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The catalytic subunit of DNA-dependent protein kinase regulates proliferation, telomere length, and genomic stability in human somatic cells. Mol Cell Biol 2008; 28:6182-95. [PMID: 18710952 DOI: 10.1128/mcb.00355-08] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The DNA-dependent protein kinase (DNA-PK) complex is a serine/threonine protein kinase comprised of a 469-kDa catalytic subunit (DNA-PK(cs)) and the DNA binding regulatory heterodimeric (Ku70/Ku86) complex Ku. DNA-PK functions in the nonhomologous end-joining pathway for the repair of DNA double-stranded breaks (DSBs) introduced by either exogenous DNA damage or endogenous processes, such as lymphoid V(D)J recombination. Not surprisingly, mutations in Ku70, Ku86, or DNA-PK(cs) result in animals that are sensitive to agents that cause DSBs and that are also immune deficient. While these phenotypes have been validated in several model systems, an extension of them to humans has been missing due to the lack of patients with mutations in any one of the three DNA-PK subunits. The worldwide lack of patients suggests that during mammalian evolution this complex has become uniquely essential in primates. This hypothesis was substantiated by the demonstration that functional inactivation of either Ku70 or Ku86 in human somatic cell lines is lethal. Here we report on the functional inactivation of DNA-PK(cs) in human somatic cells. Surprisingly, DNA-PK(cs) does not appear to be essential, although the cell line lacking this gene has profound proliferation and genomic stability deficits not observed for other mammalian systems.
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7
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Park I, Avraham HK. Cell cycle-dependent DNA damage signaling induced by ICRF-193 involves ATM, ATR, CHK2, and BRCA1. Exp Cell Res 2006; 312:1996-2008. [PMID: 16630610 DOI: 10.1016/j.yexcr.2006.02.029] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2005] [Revised: 02/11/2006] [Accepted: 02/28/2006] [Indexed: 01/13/2023]
Abstract
Topoisomerase II is essential for cell proliferation and survival and has been a target of various anticancer drugs. ICRF-193 has long been used as a catalytic inhibitor to study the function of topoisomerase II. Here, we show that ICRF-193 treatment induces DNA damage signaling. Treatment with ICRF-193 induced G2 arrest and DNA damage signaling involving gamma-H2AX foci formation and CHK2 phosphorylation. DNA damage by ICRF-193 was further demonstrated by formation of the nuclear foci of 53BP1, NBS1, BRCA1, MDC1, and FANCD2 and increased comet tail moment. The DNA damage signaling induced by ICRF-193 was mediated by ATM and ATR and was restricted to cells in specific cell cycle stages such as S, G2, and mitosis including late and early G1 phases. Downstream signaling of ATM and ATR involved the phosphorylation of CHK2 and BRCA1. Altogether, our results demonstrate that ICRF-193 induces DNA damage signaling in a cell cycle-dependent manner and suggest that topoisomerase II might be essential for the progression of the cell cycle at several stages including DNA decondensation.
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Affiliation(s)
- Iha Park
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, 4 Blackfan Circle, 3rd Floor, Boston, MA 02115, USA
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8
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Chen TY, Chen JS, Su WC, Wu MS, Tsao CJ. Expression of DNA repair gene Ku80 in lymphoid neoplasm. Eur J Haematol 2005; 74:481-8. [PMID: 15876251 DOI: 10.1111/j.1600-0609.2005.00428.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
OBJECTIVES Ku, a heterodimer of KU70 and Ku80 that binds to double-strand DNA breaks (DSBs) and activates the catalytic subunit (DNA-PKcs) when DNA is bound, is essential in DSB repair and V(D)J recombination. Ku80 is a putative tumor suppressor gene that might play an important role in drug resistance. Our aim was to determine the role of Ku80 in lymphoid malignancy. PATIENTS AND METHODS Competitive reverse transcription-polymerase chain reaction assays were performed and the expression levels of Ku80 were measured in normal peripheral blood mononuclear cells (n = 9) and malignant cells from 25 patients with acute lymphoblastic leukemia (ALL) (14 children, 11 adults), and chronic lymphoproliferative disorders (n = 6). The Ku80 transcripts were sequencing for the possibility of mutation. RESULTS No mutation or Ku80 variant at the RNA level was seen in any patient samples or in the Raji or CCRF-CEM cell lines. In Ku80 expression, 8.8-, 1.9-, and 6.2-fold mean increases were seen in adult, pediatric ALL, and chronic lymphoid malignancies compared with the control. The Ku80 was significantly higher in adult than in pediatric ALL (P = 0.02). The amount of Ku80 expression in ALL was moderately correlated with peripheral white blood cell counts, but not with Ki67 labeling index. High Ku80 expressers (higher than the mean of all patients with ALL) tended to respond poorly to therapy: Only 22% of high Ku80 expressers achieved durable complete remission compared to 62% of low expressers. CONCLUSIONS Our study suggests that Ku80 might contribute to generally poor prognoses in adult ALL.
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MESH Headings
- Adolescent
- Adult
- Antigens, Nuclear/biosynthesis
- Antigens, Nuclear/genetics
- Cell Line, Tumor
- Child
- Child, Preschool
- DNA Repair/genetics
- DNA-Binding Proteins/biosynthesis
- DNA-Binding Proteins/genetics
- Gene Expression Regulation, Leukemic
- Humans
- Infant
- Ki-67 Antigen/biosynthesis
- Ki-67 Antigen/genetics
- Ku Autoantigen
- Leukemia, Lymphocytic, Chronic, B-Cell/genetics
- Leukemia, Lymphocytic, Chronic, B-Cell/pathology
- Leukocytes, Mononuclear/metabolism
- Male
- Middle Aged
- Precursor Cell Lymphoblastic Leukemia-Lymphoma/genetics
- Precursor Cell Lymphoblastic Leukemia-Lymphoma/pathology
- Prognosis
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
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Affiliation(s)
- Tsai-Yun Chen
- Section of Hematology/Oncology, Department of Internal Medicine, National Cheng Kung University Hospital, Tainan, Taiwan.
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9
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Nakagawa T, Hayashita Y, Maeno K, Masuda A, Sugito N, Osada H, Yanagisawa K, Ebi H, Shimokata K, Takahashi T. Identification of Decatenation G2 Checkpoint Impairment Independently of DNA Damage G2 Checkpoint in Human Lung Cancer Cell Lines. Cancer Res 2004; 64:4826-32. [PMID: 15256452 DOI: 10.1158/0008-5472.can-04-0871] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
It has been suggested that attenuation of the decatenation G(2) checkpoint function, which ensures sufficient chromatid decatenation by topoisomerase II before entering into mitosis, may contribute to the acquisition of genetic instability in cancer cells. To date, however, very little information is available on this type of checkpoint defect in human cancers. In this study, we report for the first time that a proportion of human lung cancer cell lines did not properly arrest before entering mitosis in the presence of a catalytic, circular cramp-forming topoisomerase II inhibitor ICRF-193, whereas the decatenation G(2) checkpoint impairment was present independently of the impaired DNA damage G(2) checkpoint. In addition, the presence of decatenation G(2) checkpoint dysfunction was found to be associated with diminished activation of ataxia-telangiectasia mutated in response to ICRF-193, suggesting the potential involvement of an upstream pathway sensing incompletely catenated chromatids. Interestingly, hypersensitivity to ICRF-193 was observed in cell lines with decatenation G(2) checkpoint impairment and negligible activation of ataxia-telangiectasia mutated. These findings suggest the possible involvement of decatenation G(2) checkpoint impairment in the development of human lung cancers, as well as the potential clinical implication of selective killing of lung cancer cells with such defects by this type of topoisomerase II inhibitor.
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Affiliation(s)
- Taku Nakagawa
- Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chukusa-ku, Nagoya 464-8681, Japan
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10
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Oestergaard VH, Knudsen BR, Andersen AH. Dissecting the cell-killing mechanism of the topoisomerase II-targeting drug ICRF-193. J Biol Chem 2004; 279:28100-5. [PMID: 15123716 DOI: 10.1074/jbc.m402119200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Topoisomerase II is an essential enzyme that is targeted by a number of clinically valuable anticancer drugs. One class referred to as topoisomerase II poisons works by increasing the cellular level of topoisomerase II-mediated DNA breaks, resulting in apoptosis. Another class of topoisomerase II-directed drugs, the bis-dioxopiperazines, stabilizes the conformation of the enzyme where it attains an inactive salt-stable closed clamp structure. Bis-dioxopiperazines, similar to topoisomerase II poisons, induce cell killing, but the underlying mechanism is presently unclear. In this study, we use three different biochemically well characterized human topoisomerase IIalpha mutant enzymes to dissect the catalytic requirements needed for the enzyme to cause dominant sensitivity in yeast to the bis-dioxopirazine ICRF-193 and the topoisomerase II poison m-AMSA. We find that the clamp-closing activity, the DNA cleavage activity, and even both activities together are insufficient for topoisomerase II to cause dominant sensitivity to ICRF-193 in yeast. Rather, the strand passage event per se is an absolute requirement, most probably because this involves a simultaneous interaction of the enzyme with two DNA segments. Furthermore, we show that the ability of human topoisomerase IIalpha to cause dominant sensitivity to m-AMSA in yeast does not depend on clamp closure or strand passage but is directly related to the capability of the enzyme to respond to m-AMSA with increased DNA cleavage complex formation.
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Affiliation(s)
- Vibe H Oestergaard
- Department of Molecular Biology, University of Aarhus, C. F. Møllers Allé, Building 130, 8000 Aarhus C, Denmark
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11
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Adachi N, Suzuki H, Iiizumi S, Koyama H. Hypersensitivity of nonhomologous DNA end-joining mutants to VP-16 and ICRF-193: implications for the repair of topoisomerase II-mediated DNA damage. J Biol Chem 2003; 278:35897-902. [PMID: 12842886 DOI: 10.1074/jbc.m306500200] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A number of clinically useful anticancer drugs, including etoposide (VP-16), target DNA topoisomerase (topo) II. These drugs, referred to as topo II poisons, stabilize cleavable complexes, thereby generating DNA double-strand breaks. Bis-2,6-dioxopiperazines such as ICRF-193 also inhibit topo II by inducing a distinct type of DNA damage, termed topo II clamps, which has been believed to be devoid of double-strand breaks. Despite the biological and clinical importance, the molecular mechanisms for the repair of topo II-mediated DNA damage remain largely unknown. Here, we perform genetic analyses using the chicken DT40 cell line to investigate how DNA lesions caused by topo II inhibitors are repaired. Notably, we show that LIG4-/- and KU70-/- cells, which are defective in nonhomologous DNA end-joining (NHEJ), are extremely sensitive to both VP-16 and ICRF-193. In contrast, RAD54-/- cells (defective in homologous recombination) are much less hypersensitive to VP-16 than the NHEJ mutants and, more importantly, are not hypersensitive to ICRF-193. Our results provide the first evidence that NHEJ is the predominant pathway for the repair of topo II-mediated DNA damage; that is, cleavable complexes and topo II clamps. The outstandingly increased cytotoxicity of topo II inhibitors in the absence of NHEJ suggests that simultaneous inhibition of topo II and NHEJ would provide a powerful protocol in cancer chemotherapy involving topo II inhibitors.
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Affiliation(s)
- Noritaka Adachi
- Kihara Institute for Biological Research, Graduate School of Integrated Science, Yokohama City University, Totsuka-ku, Yokohama 244-0813, Japan.
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12
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Hajji N, Pastor N, Mateos S, Domínguez I, Cortés F. DNA strand breaks induced by the anti-topoisomerase II bis-dioxopiperazine ICRF-193. Mutat Res 2003; 530:35-46. [PMID: 14563529 DOI: 10.1016/s0027-5107(03)00135-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The bis-dioxopiperazine ICRF-193 has long time been considered as a pure topoisomerase II catalytic inhibitor able to exert its inhibitory effect on the enzyme without stabilization of the so-called cleavable complex formed by DNA covalently bound to topoisomerase II. In recent years, however, this concept has been challenged, as a number of reports have shown that ICRF-193 really "poisons" the enzyme, most likely through a different mechanism from that shown by the classical topoisomerase II poisons used in cancer chemotherapy. In the present investigation, we have carried out a study of the capacity of ICRF-193 to induce DNA strand breaks, as classical poisons do, in cultured V79 and irs-2 Chinese hamster lung fibroblasts using the comet assay and pulsed-field gel electrophoresis (PFGE). Our results clearly show that ICRF-193 readily induces breakage in DNA through a mechanism as yet poorly understood.
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Affiliation(s)
- N Hajji
- Department of Cell Biology, Faculty of Biology, University of Seville, Avda. Reina Mercedes no. 6, 41012 Seville, Spain
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13
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Abstract
The nuclear enzyme DNA topoisomerase II is a major target for antineoplastic agents. All topoisomerase II-directed agents are able to interfere with at least one step of the catalytic cycle. Agents able to stabilize the covalent DNA topoisomerase II complex (also known as the cleavable complex) are traditionally called topoisomerase II poisons, while agents acting on any of the other steps in the catalytic cycle are called catalytic inhibitors. Thus, catalytic topoisomerase II inhibitors are a heterogeneous group of compounds that might interfere with the binding between DNA and topoisomerase II (aclarubicin and suramin), stabilize noncovalent DNA topoisomerase II complexes (merbarone, ICRF-187, and structurally related bisdioxopiperazine derivatives), or inhibit ATP binding (novobiocin). Some, such as fostriecin, may also have alternative biological targets. Whereas topoisomerase II poisons are used solely for their antitumor activities, catalytic inhibitors are utilized for a variety of reasons, including their activity as antineoplastic agents (aclarubicin and MST-16), cardioprotectors (ICRF-187), or modulators in order to increase the efficacy of other agents (suramin and novobiocin). In this review, the mechanism and biological activity of different catalytic inhibitors is described, with emphasis on therapeutically used compounds. We will then discuss future development and applications of this interesting class of compounds.
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Affiliation(s)
- Annette K Larsen
- CNRS UMR 8532, Ecole Normale Supérieure, Cachan and Institut Gustave Roussy PR2, 94805 Villejuif, France.
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14
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Schild-Poulter C, Matheos D, Novac O, Cui B, Giffin W, Ruiz MT, Price GB, Zannis-Hadjopoulos M, Haché RJG. Differential DNA binding of Ku antigen determines its involvement in DNA replication. DNA Cell Biol 2003; 22:65-78. [PMID: 12713733 DOI: 10.1089/104454903321515887] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Ku antigen (Ku70/Ku80) is a regulatory subunit of DNA-dependent protein kinase, which participates in the regulation of DNA replication and gene transcription through specific DNA sequences. In this study, we have compared the mechanism of action of Ku from A3/4, a DNA sequence that appears in mammalian origins of DNA replication, and NRE1, a transcriptional regulatory element in the long terminal repeat of mouse mammary tumor virus through which Ku antigen and its associated kinase, DNA-dependent protein kinase (DNA-PK(cs)), act to repress steroid-induced transcription. Our results indicate that replication from a minimal replication origin of ors8 is independent of DNA-PK(cs) and that Ku interacts with A3/4-like sequences and NRE1 in fundamentally different ways. UV crosslinking experiments revealed differential interactions of the Ku subunits with A3/4, NRE1, and two other proposed Ku transcriptional regulatory elements. In vitro footprinting experiments showed direct contact of Ku on A3/4 and over the region of ors8 homologous to A3/4. In vitro replication assays using ors8 templates bearing mutations in the A3/4-like sequence suggested that Ku binding to this element was necessary for replication. By contrast, in vitro replication experiments revealed that NRE1 was not involved in DNA replication. Our results establish A3/4 as a new class of Ku DNA binding site. Classification of Ku DNA binding into eight categories of interaction based on recognition and DNA crosslinking experiments is discussed.
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Affiliation(s)
- Caroline Schild-Poulter
- Department of Medicine, The Ottawa Health Research Institute, University of Ottawa, Ottawa, Ontario, Canada
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15
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Matheos D, Novac O, Price GB, Zannis-Hadjopoulos M. Analysis of the DNA replication competence of the xrs-5 mutant cells defective in Ku86. J Cell Sci 2003; 116:111-24. [PMID: 12456721 DOI: 10.1242/jcs.00156] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The radiosensitive mutant xrs-5, a derivative of the Chinese hamster ovary (CHO) K1 cell line, is defective in DNA double-strand break repair and V(D)J recombination. The defective phenotypes of xrs-5 cells are complemented by the 86 kDa subunit of Ku antigen. OBA is a protein, previously purified from HeLa cells, that binds in a sequence-specific manner to mammalian origins of DNA replication. The DNA-binding subunit of OBA has been identified as Ku86. We tested the xrs-5 cell line for its ability to replicate a mammalian origin-containing plasmid, p186, in vivo and in vitro. In vivo, the p186 episomal DNA replication in transfected xrs-5 cells was reduced by 45% when compared with the CHO K1 cells transfected with p186. In vitro, although total and cytoplasmic cell extracts from xrs-5 cells replicated the p186 with the same efficiency as the parental CHO K1 cell extracts, xrs-5 nuclear extracts did not possess any detectable replication activity. Addition of affinity-purified OBA/Ku restored replication in the xrs-5 nuclear extract reaction. Western blot analyses showed that the levels of other replication proteins (Orc2, PCNA, DNA polymerase epsilon and delta, Primase and Topoisomerase IIalpha) were comparable in both the xrs-5 mutant and CHO K1 wild-type cell lines. In addition, the in vivo association of Ku with the DHFR origin-containing sequence (oribeta) was examined in both the CHO K1 and xrs-5 cell lines by a chromatin immunoprecipitation (ChIP) assay. Anti-Ku antibodies did not immunoprecipitate a detectable amount of Ku from the xrs-5 cells in the origin-containing sequence, in contrast to the CHO K1 cells, wherein Ku was found to be associated with the oribeta origin. The data implicate Ku antigen in in vivo and in vitro DNA replication and suggest the existence of another protein with Ku-like functions in the xrs-5 cells.
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Affiliation(s)
- Diamanto Matheos
- McGill Cancer Centre, McGill University, Montréal, Québec, Canada, H3G 1Y6
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16
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Koike M. Dimerization, translocation and localization of Ku70 and Ku80 proteins. JOURNAL OF RADIATION RESEARCH 2002; 43:223-236. [PMID: 12518983 DOI: 10.1269/jrr.43.223] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The Ku protein is a complex of two subunits, Ku70 and Ku80, and was originally identified as an autoantigen recognized by the sera of patients with autoimmune diseases. The Ku protein plays a key role in multiple nuclear processes, e.g., DNA repair, chromosome maintenance, transcription regulation, and V(D)J recombination. The mechanism underlying the regulation of all the diverse functions of Ku is still unclear, although it seems that Ku is a multifunctional protein that works in nuclei. On the other hand, several studies have reported cytoplasmic or cell surface localization of Ku in various cell types. To clarify the fundamental characteristics of Ku, we have examined the expression, heterodimerization, subcellular localization, chromosome location, and molecular mechanisms of the nuclear transport of Ku70 and Ku80. The mechanism that regulates for nuclear localization of Ku70 and Ku80 appears to play, at least in part, a key role in regulating the physiological function of Ku in vivo.
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Affiliation(s)
- Manabu Koike
- Radiation Hazards Research Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
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17
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Huang KC, Gao H, Yamasaki EF, Grabowski DR, Liu S, Shen LL, Chan KK, Ganapathi R, Snapka RM. Topoisomerase II poisoning by ICRF-193. J Biol Chem 2001; 276:44488-94. [PMID: 11577077 DOI: 10.1074/jbc.m104383200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Antineoplastic bis(dioxopiperazine)s, such as meso-2,3-bis(2,6-dioxopiperazin-4-yl)butane (ICRF-193), are widely believed to be only catalytic inhibitors of topoisomerase II. However, topoisomerase inhibitors have little or no antineoplastic activity unless they are topoisomerase poisons, a special subclass of topoisomerase-targeting drugs that stabilize topoisomerase-DNA strand passing intermediates and thus cause the topoisomerase to become a cytotoxic DNA-damaging agent. Here we report that ICRF-193 is a very significant topoisomerase II poison. Detection of topoisomerase II poisoning by ICRF-193 required the use of a chaotropic protein denaturant in the topoisomerase poisoning assays. ICRF-193 caused dose-dependent cross-linking of human topoisomerase IIbeta to DNA and stimulated topoisomerase IIbeta-mediated DNA cleavage at specific sites on (32)P-end-labeled DNA. Human topoisomerase IIalpha-mediated DNA cleavage was stimulated to a lesser extent by ICRF-193. In vivo experiments with MCF-7 cells also showed the requirement of a chaotropic protein denaturant in the assays and selectivity for the beta-isozyme of human topoisomerase II. Studies with two topoisomerase IIbeta-negative cell model systems confirmed significant topoisomerase II poisoning by ICRF-193 in the wild type cells and were consistent with beta-isozyme selectivity. Common use of only the detergent, SDS, in assays may have led to failure to detect topoisomerase II poisoning by ICRF-193 in earlier studies.
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Affiliation(s)
- K C Huang
- Department of Radiology, The Ohio State University College of Medicine, Columbus, Ohio 43210, USA
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18
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Lynch EM, Moreland RB, Ginis I, Perrine SP, Faller DV. Hypoxia-activated ligand HAL-1/13 is lupus autoantigen Ku80 and mediates lymphoid cell adhesion in vitro. Am J Physiol Cell Physiol 2001; 280:C897-911. [PMID: 11245607 DOI: 10.1152/ajpcell.2001.280.4.c897] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hypoxia is known to induce extravasation of lymphocytes and leukocytes during ischemic injury and increase the metastatic potential of malignant lymphoid cells. We have recently identified a new adhesion molecule, hypoxia-activated ligand-1/13 (HAL-1/13), that mediates the hypoxia-induced increases in lymphocyte and neutrophil adhesion to endothelium and hypoxia-mediated invasion of endothelial cell monolayers by tumor cells. In this report, we used expression cloning to identify this molecule as the lupus antigen and DNA-dependent protein kinase-associated nuclear protein, Ku80. The HAL-1/13-Ku80 antigen is present on the surface of leukemic and solid tumor cell lines, including T and B lymphomas, myeloid leukemias, neuroblastoma, rhabdomyosarcoma, and breast carcinoma cells. Transfection and ectopic expression of HAL-1/13-Ku80 on (murine) NIH/3T3 fibroblasts confers the ability of these normally nonadhesive cells to bind to a variety of human lymphoid cell lines. This adhesion can be specifically blocked by HAL-1/13 or Ku80-neutralizing antibodies. Loss of expression variants of these transfectants simultaneously lost their adhesive properties toward human lymphoid cells. Hypoxic exposure of tumor cell lines resulted in upregulation of HAL-1/13-Ku80 expression at the cell surface, mediated by redistribution of the antigen from the nucleus. These studies indicate that the HAL-1/13-Ku80 molecule may mediate, in part, the hypoxia-induced adhesion of lymphocytes, leukocytes, and tumor cells.
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Affiliation(s)
- E M Lynch
- Cancer Research Center, Boston University School of Medicine, 80 E. Concord St., Boston, MA 02118, USA
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19
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Muñoz P, Baus F, Piette J. Ku antigen is required to relieve G2 arrest caused by inhibition of DNA topoisomerase II activity by the bisdioxopiperazine ICRF-193. Oncogene 2001; 20:1990-9. [PMID: 11360183 DOI: 10.1038/sj.onc.1204262] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2000] [Revised: 01/09/2001] [Accepted: 01/15/2001] [Indexed: 11/09/2022]
Abstract
Ku antigen is necessary for DNA double-strand break (DSB) repair through its ability to bind DNA ends with high affinity and to recruit the catalytic subunit of DNA-PK to the DSBs. Ku-deficient cells are hypersensitive to agents causing DSBs in DNA but also to the DNA topoisomerase II (topo II) inhibitor ICRF-193, which does not induce DSBs. This suggests a new role of Ku antigen, that is independent of DSB repair by DNA-PK. Here we characterize the basis for the hypersensitivity of Ku-deficient cells to ICRF-193. Chromosome condensation and segregation, which are dependent on topo II, but also the catalytic activity of topo II in late S-G2 were inhibited to a comparable extent when ICRF-193 was applied to Ku-deficient cells or wild-type cells. However, mutant cells arrested in G2 by ICRF-193 treatment were unable to progress into M phase upon drug removal, although drug-trapped topo II complexes were removed from DNA and the two isoforms of topo II recovered their catalytic activity as in wild-type cells. The reversibility of G2 arrest was recovered by complementation of mutant cells with a human Ku86 cDNA. Notably, chromosome condensation was abnormal in Ku-deficient cells after suppression of the G2 arrest by caffeine, even in the absence of ICRF-193. These results reflect the involvement of Ku-antigen in the cellular response to topo II inhibition, more particularly in relieving G2 arrest caused by topo II inhibition in late S/G2 and the subsequent recovery of chromosome condensation.
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Affiliation(s)
- P Muñoz
- Institut de Génétique Moléculaire de Montpellier, UMR 5535, IFR 24, CNRS, 1919 route de Mende, 34293 Montpellier Cedex 5, France
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20
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Arrington ED, Caldwell MC, Kumaravel TS, Lohani A, Joshi A, Evans MK, Chen HT, Nussenzweig A, Holbrook NJ, Gorospe M. Enhanced sensitivity and long-term G2 arrest in hydrogen peroxide-treated Ku80-null cells are unrelated to DNA repair defects. Free Radic Biol Med 2000; 29:1166-76. [PMID: 11121725 DOI: 10.1016/s0891-5849(00)00439-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
While the Ku complex, comprised of Ku70 and Ku80, is primarily involved in the repair of DNA double-strand breaks, it is also believed to participate in additional cellular processes. Here, treatment of embryo fibroblasts (MEFs) derived from either wild-type or Ku80-null (Ku80(-/-)) mice with various stress agents revealed that hydrogen peroxide (H(2)O(2)) was markedly more cytotoxic for Ku80(-/-) MEFs and led to their long-term accumulation in the G2 phase. This differential response was not due to differences in DNA repair, since H(2)O(2)-triggered DNA damage was repaired with comparable efficiency in both Wt and Ku80(-/-) MEFs, but was associated with differences in the expression of important cell cycle regulatory genes. Our results support the notion that Ku80-mediated cytoprotection and G2-progression are not only dependent on the cell's DNA repair but also may reflect Ku80's influence on additional cellular processes such as gene expression.
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Affiliation(s)
- E D Arrington
- Laboratory of Biological Chemistry, National Institute on Aging, NIH, Baltimore, MD 21224, USA
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21
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Abstract
Ku is a heterodimeric protein composed of approximately 70- and approximately 80-kDa subunits (Ku70 and Ku80) originally identified as an autoantigen recognized by the sera of patients with autoimmune diseases. Ku has high binding affinity for DNA ends and that is why originally it was known as a DNA end binding protein, but now it is known to also bind the DNA structure at nicks, gaps, hairpins, as well as the ends of telomeres. It has been reported also to bind with sequence specificity to DNA and with weak affinity to RNA. Ku is an abundant nuclear protein and is present in vertebrates, insects, yeast, and worms. Ku contains ssDNA-dependent ATPase and ATP-dependent DNA helicase activities. It is the regulatory subunit of the DNA-dependent protein kinase that phosphorylates many proteins, including SV-40 large T antigen, p53, RNA-polymerase II, RP-A, topoisomerases, hsp90, and many transcription factors such as c-Jun, c-Fos, oct-1, sp-1, c-Myc, TFIID, and many more. It seems to be a multifunctional protein that has been implicated to be involved directly or indirectly in many important cellular metabolic processes such as DNA double-strand break repair, V(D)J recombination of immunoglobulins and T-cell receptor genes, immunoglobulin isotype switching, DNA replication, transcription regulation, regulation of heat shock-induced responses, regulation of the precise structure of telomeric termini, and it also plays a novel role in G2 and M phases of the cell cycle. The mechanism underlying the regulation of all the diverse functions of Ku is still obscure.
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Affiliation(s)
- R Tuteja
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi.
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22
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Koike M, Awaji T, Kataoka M, Tsujimoto G, Kartasova T, Koike A, Shiomi T. Differential subcellular localization of DNA-dependent protein kinase components Ku and DNA-PKcs during mitosis. J Cell Sci 1999; 112 ( Pt 22):4031-9. [PMID: 10547363 DOI: 10.1242/jcs.112.22.4031] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Ku protein is a complex of two subunits, Ku70 and Ku80. Ku plays an important role in DNA-PKcs-dependent double-strand break repair and V(D)J recombination, and in growth regulation, which is DNA-PKcs-independent. We studied the expression and the subcellular localization of Ku and DNA-PKcs throughout the cell cycle in several established human cell lines. Using immunofluorescence analysis and confocal laser scanning microscopy, we detected Ku70 and Ku80 in the nuclei in interphase cells. In mitotic cells (1) most of Ku protein was found diffused in the cytoplasm, (2) a fraction was detected at the periphery of condensed chromosomes, (3) no Ku protein was present in the chromosome interior. Association of Ku with isolated chromosomes was also observed. On the other hand, DNA-PKcs was detected in the nucleus in interphase cells and not at the periphery of condensed chromosomes during mitosis. Using indirect immunoprecipitation, we found that throughout the cell cycle, Ku70 and Ku80 were present as heterodimers, some in complex with DNA-PKcs. Our findings suggest that the localization of Ku at the periphery of metaphase chromosomes might be imperative for a novel function of Ku in the G(2)/M phase, which does not require DNA-PKcs.
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Affiliation(s)
- M Koike
- Genome Research Group, National Institute of Radiological Sciences, Inage-ku, Chiba 263-8555, Japan.
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23
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Sert V, Cans C, Tasca C, Bret-Bennis L, Oswald E, Ducommun B, De Rycke J. The bacterial cytolethal distending toxin (CDT) triggers a G2 cell cycle checkpoint in mammalian cells without preliminary induction of DNA strand breaks. Oncogene 1999; 18:6296-304. [PMID: 10597228 DOI: 10.1038/sj.onc.1203007] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The bacterial cytolethal distending toxin (CDT) was previously shown to arrest the tumor-derived HeLa cell line in the G2-phase of the cell cycle through inactivation of CDK1, a cyclin-dependent kinase whose state of activation determines entry into mitosis. We have analysed the effects induced in HeLa cells by CDT, in comparison to those induced by etoposide, a prototype anti-tumoral agent that triggers a G2 cell cycle checkpoint by inducing DNA damage. Both CDT and etoposide inhibit cell proliferation and induces the formation of enlarged mononucleated cells blocked in G2. In both cases, CDK1 from arrested cells could be reactivated both in vitro by dephosphorylation by recombinant Cdc25B phosphatase and in vivo by caffeine. However, the cell cycle arrest triggered by CDT, unlike etoposide, did not originate from DNA strand breaks as demonstrated in the single cell gel electrophoresis assay and by the absence of slowing down of S phase in synchronized cells. Together with additional observations on synchronized HeLa cells, our results suggest that CDT triggers a G2 cell cycle checkpoint that is initiated during DNA replication and that is independent of DNA damage.
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Affiliation(s)
- V Sert
- Unité associée de Microbiologie Moléculaire, Institut National de la Recherche Agronomique et Ecole Nationale Vétérinaire, Toulouse, France
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24
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Galande S, Kohwi-Shigematsu T. Poly(ADP-ribose) polymerase and Ku autoantigen form a complex and synergistically bind to matrix attachment sequences. J Biol Chem 1999; 274:20521-8. [PMID: 10400681 DOI: 10.1074/jbc.274.29.20521] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Genomic sequences with a cluster of ATC sequence stretches where one strand consists exclusively of well mixed As, Ts, and Cs confer high base unpairing propensity under negative superhelical strain. Such base unpairing regions (BURs) are typically found in scaffold or matrix attachment regions (SARs/MARs) that are thought to contribute to the formation of the loop domain structure of chromatin. Several proteins, including cell type-specific proteins, have been identified that bind specifically to double-stranded BURs either in vitro or in vivo. By using BUR-affinity chromatography to isolate BUR-binding proteins from breast cancer SK-BR-3 cells, we almost exclusively obtained a complex of poly(ADP-ribose) polymerase (PARP) and DNA-dependent protein kinase (DNA-PK). Both PARP and DNA-PK are activated by DNA strand breaks and are implicated in DNA repair, recombination, DNA replication, and transcription. In contrast to the previous notion that PARP and Ku autoantigen, the DNA-binding subunit of DNA-PK, mainly bind to free ends of DNA, here we show that both proteins individually bind BURs with high affinity and specificity in an end-independent manner using closed circular BUR-containing DNA substrates. We further demonstrate that PARP and Ku autoantigen form a molecular complex in vivo and in vitro in the absence of DNA, and as a functional consequence, their affinity to the BURs are synergistically enhanced. ADP-ribosylation of the nuclear extract abrogated the BUR binding activity of this complex. These results provide a mechanistic link toward understanding the functional overlap of PARP and DNA-PK and suggest a novel role for these proteins in the regulation of chromatin structure and function.
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Affiliation(s)
- S Galande
- Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, USA
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25
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Giffin W, Gong W, Schild-Poulter C, Haché RJ. Ku antigen-DNA conformation determines the activation of DNA-dependent protein kinase and DNA sequence-directed repression of mouse mammary tumor virus transcription. Mol Cell Biol 1999; 19:4065-78. [PMID: 10330147 PMCID: PMC104366 DOI: 10.1128/mcb.19.6.4065] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mouse mammary tumor virus (MMTV) transcription is repressed by DNA-dependent protein kinase (DNA-PK) through a DNA sequence element, NRE1, in the viral long terminal repeat that is a sequence-specific DNA binding site for the Ku antigen subunit of the kinase. While Ku is an essential component of the active kinase, how the catalytic subunit of DNA-PK (DNA-PKcs) is regulated through its association with Ku is only beginning to be understood. We report that activation of DNA-PKcs and the repression of MMTV transcription from NRE1 are dependent upon Ku conformation, the manipulation of DNA structure by Ku, and the contact of Ku80 with DNA. Truncation of one copy of the overlapping direct repeat that comprises NRE1 abrogated the repression of MMTV transcription by Ku-DNA-PKcs. Remarkably, the truncated element was recognized by Ku-DNA-PKcs with affinity similar to that of the full-length element but was unable to promote the activation of DNA-PKcs. Analysis of Ku-DNA-PKcs interactions with DNA ends, double- and single-stranded forms of NRE1, and the truncated NRE1 element revealed striking differences in Ku conformation that differentially affected the recruitment of DNA-PKcs and the activation of kinase activity.
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Affiliation(s)
- W Giffin
- Departments of Medicine, Microbiology and Immunology, The Loeb Health Research Institute at the Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada
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