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Fan R, Zhou Y, Chen X, Zhong X, He F, Peng W, Li L, Wang X, Xu Y. Porphyromonas gingivalis Outer Membrane Vesicles Promote Apoptosis via msRNA-Regulated DNA Methylation in Periodontitis. Microbiol Spectr 2023; 11:e0328822. [PMID: 36629433 PMCID: PMC9927323 DOI: 10.1128/spectrum.03288-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 12/07/2022] [Indexed: 01/12/2023] Open
Abstract
The outer membrane vesicles (OMVs) produced by Porphyromonas gingivalis contain a variety of bioactive molecules that may be involved in the progression of periodontitis. However, the participation of P. gingivalis OMVs in the development of periodontitis has not been elucidated. Here, we isolated P. gingivalis OMVs and confirmed their participation in periodontitis both in vivo and in vitro. Microcomputed tomography (micro-CT) and histological analysis showed that under stimulation with P. gingivalis OMVs, the alveolar bone of rats was significantly resorbed in vivo. We found that P. gingivalis OMVs were taken up by human periodontal ligament cells ([hPDLCs]) in vitro, which subsequently resulted in apoptosis and inflammatory cytokine release, which was accomplished by the microRNA-size small RNA (msRNA) sRNA45033 in the P. gingivalis OMVs. Through bioinformatics analysis and screening of target genes, chromobox 5 (CBX5) was identified as the downstream target of screened-out sRNA45033. Using a dual-luciferase reporter assay, overexpression, and knockdown methods, sRNA45033 was confirmed to target CBX5 to regulate hPDLC apoptosis. In addition, CUT&Tag (cleavage under targets and tagmentation) analysis confirmed the mechanism that CBX5 regulates apoptosis through the methylation of p53 DNA. Collectively, these findings indicate that the role of P. gingivalis OMVs is immunologically relevant and related to bacterial virulence during the development of periodontitis. IMPORTANCE P. gingivalis is a bacterium often associated with periodontitis. This study demonstrates that (i) sRNA45033 in P. gingivalis OMVs targets CBX5, (ii) CBX5 regulates the methylation of p53 DNA and its expression, which is associated with apoptosis, and (iii) a novel mechanism of interaction between hosts and pathogens is mediated by OMVs in the occurrence of periodontitis.
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Affiliation(s)
- Ruyi Fan
- Department of Periodontics, the Affiliated Stomatological Hospital of Nanjing Medical University, Nanjing, China
- Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China
- Jiangsu Province Engineering Research Center of Stomatological Translational Medicine, Nanjing, China
| | - Yi Zhou
- Department of Periodontics, the Affiliated Stomatological Hospital of Nanjing Medical University, Nanjing, China
- Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China
- Jiangsu Province Engineering Research Center of Stomatological Translational Medicine, Nanjing, China
| | - Xu Chen
- Department of Periodontics, the Affiliated Stomatological Hospital of Nanjing Medical University, Nanjing, China
- Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China
- Jiangsu Province Engineering Research Center of Stomatological Translational Medicine, Nanjing, China
| | - Xianmei Zhong
- Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China
- Department of Periodontics, Taizhou Stomatological Hospital, Taizhou, China
| | - Fanzhen He
- Department of Periodontics, the Affiliated Stomatological Hospital of Nanjing Medical University, Nanjing, China
- Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China
| | - Wenzao Peng
- Department of Periodontics, the Affiliated Stomatological Hospital of Nanjing Medical University, Nanjing, China
- Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China
| | - Lu Li
- Department of Periodontics, the Affiliated Stomatological Hospital of Nanjing Medical University, Nanjing, China
- Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China
- Jiangsu Province Engineering Research Center of Stomatological Translational Medicine, Nanjing, China
| | - Xiaoqian Wang
- Department of Periodontics, the Affiliated Stomatological Hospital of Nanjing Medical University, Nanjing, China
- Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China
- Jiangsu Province Engineering Research Center of Stomatological Translational Medicine, Nanjing, China
| | - Yan Xu
- Department of Periodontics, the Affiliated Stomatological Hospital of Nanjing Medical University, Nanjing, China
- Jiangsu Province Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China
- Jiangsu Province Engineering Research Center of Stomatological Translational Medicine, Nanjing, China
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2
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Sun H, Chen Y, Yan K, Shao Y, Zhang QC, Lin Y, Xi Q. Recruitment of TRIM33 to cell-context specific PML nuclear bodies regulates nodal signaling in mESCs. EMBO J 2023; 42:e112058. [PMID: 36524443 PMCID: PMC9890237 DOI: 10.15252/embj.2022112058] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 11/15/2022] [Accepted: 11/28/2022] [Indexed: 12/23/2022] Open
Abstract
TRIM33 is a chromatin reader required for mammalian mesendoderm differentiation after activation of Nodal signaling, while its role in mESCs is still elusive. Here, we report that TRIM33 co-localizes with promyelocytic leukemia nuclear bodies (PML-NBs) specifically in mESCs, to mediate Nodal signaling-directed transcription of Lefty1/2. We show that TRIM33 puncta formation in mESCs depends on PML and on specific assembly of PML-NBs. Moreover, TRIM33 and PML co-regulate Lefty1/2 expression in mESCs, with both PML protein and formation of mESCs-specific PML-NBs being required for TRIM33 recruitment to these loci, and PML-NBs directly associating with the Lefty1/2 loci. Finally, a TurboID proximity-labeling experiment confirmed that TRIM33 is highly enriched only in mESCs-specific PML-NBs. Thus, our study supports a model in which TRIM33 condensates regulate Nodal signaling-directed transcription in mESCs and shows that PML-NBs can recruit distinct sets of client proteins in a cell-context-dependent manner.
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Affiliation(s)
- Hongyao Sun
- MOE Key Laboratory of Protein Sciences, School of Life SciencesTsinghua UniversityBeijingChina
- Joint Graduate Program of Peking‐Tsinghua‐NIBSTsinghua UniversityBeijingChina
| | - Yutong Chen
- IDG/McGovern Institute for Brain Research, School of Life SciencesTsinghua UniversityBeijingChina
| | - Kun Yan
- Tsinghua‐Peking Center for Life Sciences, School of Life SciencesTsinghua UniversityBeijingChina
| | - Yanqiu Shao
- Tsinghua‐Peking Center for Life Sciences, School of Life SciencesTsinghua UniversityBeijingChina
| | - Qiangfeng C Zhang
- Joint Graduate Program of Peking‐Tsinghua‐NIBSTsinghua UniversityBeijingChina
- Tsinghua‐Peking Center for Life Sciences, School of Life SciencesTsinghua UniversityBeijingChina
- MOE Key Laboratory of Bioinformatics, Center for Synthetic and Systems Biology, School of Life SciencesTsinghua UniversityBeijingChina
| | - Yi Lin
- IDG/McGovern Institute for Brain ResearchTsinghua‐Peking Joint Centre for Life SciencesBeijingChina
| | - Qiaoran Xi
- MOE Key Laboratory of Protein Sciences, School of Life SciencesTsinghua UniversityBeijingChina
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3
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Martínez P, Sánchez-Vázquez R, Ferrara-Romeo I, Serrano R, Flores JM, Blasco MA. A mouse model for Li-Fraumeni-Like Syndrome with cardiac angiosarcomas associated to POT1 mutations. PLoS Genet 2022; 18:e1010260. [PMID: 35727838 PMCID: PMC9212151 DOI: 10.1371/journal.pgen.1010260] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 05/16/2022] [Indexed: 11/18/2022] Open
Abstract
The shelterin protein POT1 has been found mutated in many different familial and sporadic cancers, however, no mouse models to understand the pathobiology of these mutations have been developed so far. To address the molecular mechanisms underlying the tumorigenic effects of POT1 mutant proteins in humans, we have generated a mouse model for the human POT1R117C mutation found in Li-Fraumeni-Like families with cases of cardiac angiosarcoma by introducing this mutation in the Pot1a endogenous locus, knock-in for Pot1aR117C. We find here that both mouse embryonic fibroblasts (MEFs) and tissues from Pot1a+/ki mice show longer telomeres than wild-type controls. Longer telomeres in Pot1a+/ki MEFs are dependent on telomerase activity as they are not found in double mutant Pot1a+/kiTert-/- telomerase-deficient MEFs. By using complementation assays we further show that POT1a pR117C exerts dominant-negative effects at telomeres. As in human Li-Fraumeni patients, heterozygous Pot1a+/ki mice spontaneously develop a high incidence of angiosarcomas, including cardiac angiosarcomas, and this is associated to the presence of abnormally long telomeres in endothelial cells as well as in the tumors. The Pot1a+/R117C mouse model constitutes a useful tool to understand human cancers initiated by POT1 mutations. We have generated a mouse model for the human POT1R117C mutation found in Li-Fraumeni-Like (LFL) families with cases of cardiac angiosarcoma by introducing this mutation in the Pot1a endogenous locus, knock-in for Pot1aR117C. The Pot1a+/ki mice show longer telomeres than wild-type controls. Longer telomeres in mutant mice are dependent on telomerase activity as they are not found in a telomerase deficient background. As in human Li-Fraumeni patients, heterozygous Pot1a+/ki mice spontaneously develop a high incidence of angiosarcomas, including cardiac angiosarcomas, and this is associated to the presence of abnormally long telomeres in endothelial cells as well as in the tumors. The ki-Pot1aR117C mouse constitutes a potential pre-clinical mouse model for LFL syndrome presenting with high angiosarcoma incidence that could provide in the future a very useful tool for the study of treatments for these tumors.
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Affiliation(s)
- Paula Martínez
- Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Centre (CNIO), Madrid, Spain
| | - Raúl Sánchez-Vázquez
- Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Centre (CNIO), Madrid, Spain
| | - Iole Ferrara-Romeo
- Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Centre (CNIO), Madrid, Spain
| | - Rosa Serrano
- Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Centre (CNIO), Madrid, Spain
| | - Juana M. Flores
- Animal Surgery and Medicine Department, Faculty of Veterinary Science, Complutense University of Madrid, Madrid, Spain
| | - Maria A. Blasco
- Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Centre (CNIO), Madrid, Spain
- * E-mail:
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Functional characterization of miR-708 microRNA in telomerase positive and negative human cancer cells. Sci Rep 2021; 11:17052. [PMID: 34426596 PMCID: PMC8382839 DOI: 10.1038/s41598-021-96096-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 07/29/2021] [Indexed: 02/07/2023] Open
Abstract
Activation of a telomere length maintenance mechanism (TMM), including telomerase and alternative lengthening of telomeres (ALT), is essential for replicative immortality of tumor cells, although its regulatory mechanisms are incompletely understood. We conducted a microRNA (miRNA) microarray analysis on isogenic telomerase positive (TEP) and ALT cancer cell lines. Amongst nine miRNAs that showed difference in their expression in TEP and ALT cancer cells in array analysis, miR-708 was selected for further analysis since it was consistently highly expressed in a large panel of ALT cells. miR-708 in TEP and ALT cancer cells was not correlated with C-circle levels, an established feature of ALT cells. Its overexpression induced suppression of cell migration, invasion, and angiogenesis in both TEP and ALT cells, although cell proliferation was inhibited only in TEP cells suggesting that ALT cells may have acquired the ability to escape inhibition of cell proliferation by sustained miR-708 overexpression. Further, cell proliferation regulation in TEP cells by miR708 appears to be through the CARF-p53 pathway. We demonstrate here that miR-708 (i) is the first miRNA shown to be differentially regulated in TEP and ALT cancer cells, (ii) possesses tumor suppressor function, and (iii) deregulates CARF and p21WAF1-mediated signaling to limit proliferation in TEP cells.
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Mutations inhibiting KDM4B drive ALT activation in ATRX-mutated glioblastomas. Nat Commun 2021; 12:2584. [PMID: 33972520 PMCID: PMC8110556 DOI: 10.1038/s41467-021-22543-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 03/16/2021] [Indexed: 12/24/2022] Open
Abstract
Alternative Lengthening of Telomeres (ALT) is a telomere maintenance pathway utilised in 15% of cancers. ALT cancers are strongly associated with inactivating mutations in ATRX; yet loss of ATRX alone is insufficient to trigger ALT, suggesting that additional cooperating factors are involved. We identify H3.3G34R and IDH1/2 mutations as two such factors in ATRX-mutated glioblastomas. Both mutations are capable of inactivating histone demethylases, and we identify KDM4B as the key demethylase inactivated in ALT. Mouse embryonic stem cells inactivated for ATRX, TP53, TERT and KDM4B (KDM4B knockout or H3.3G34R) show characteristic features of ALT. Conversely, KDM4B over-expression in ALT cancer cells abrogates ALT-associated features. In this work, we demonstrate that inactivation of KDM4B, through H3.3G34R or IDH1/2 mutations, acts in tandem with ATRX mutations to promote ALT in glioblastomas. Alternative Lengthening of Telomeres (ALT) is a telomere maintenance pathway utilised in 15% of cancers that have been associated with mutations in ATRX. Here the authors reveal a functional role of histone demethylases KDM4B in regulating ALT activation.
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6
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Shen M, Young A, Autexier C. PCNA, a focus on replication stress and the alternative lengthening of telomeres pathway. DNA Repair (Amst) 2021; 100:103055. [PMID: 33581499 DOI: 10.1016/j.dnarep.2021.103055] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 01/25/2021] [Indexed: 12/16/2022]
Abstract
The maintenance of telomeres, which are specialized stretches of DNA found at the ends of linear chromosomes, is a crucial step for the immortalization of cancer cells. Approximately 10-15 % of cancer cells use a homologous recombination-based mechanism known as the Alternative Lengthening of Telomeres (ALT) pathway to maintain their telomeres. Telomeres in general pose a challenge to DNA replication owing to their repetitive nature and potential for forming secondary structures. Telomeres in ALT+ cells especially are subject to elevated levels of replication stress compared to telomeres that are maintained by the enzyme telomerase, in part due to the incorporation of telomeric variant repeats at ALT+ telomeres, their on average longer lengths, and their modified chromatin states. Many DNA metabolic strategies exist to counter replication stress and to protect stalled replication forks. The role of proliferating cell nuclear antigen (PCNA) as a platform for recruiting protein partners that participate in several of these DNA replication and repair pathways has been well-documented. We propose that many of these pathways may be active at ALT+ telomeres, either to facilitate DNA replication, to manage replication stress, or during telomere extension. Here, we summarize recent evidence detailing the role of PCNA in pathways including DNA secondary structure resolution, DNA damage bypass, replication fork restart, and DNA damage synthesis. We propose that an examination of PCNA and its post-translational modifications (PTMs) may offer a unique lens by which we might gain insight into the DNA metabolic landscape that is distinctively present at ALT+ telomeres.
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Affiliation(s)
- Michelle Shen
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, H3A 0C7, Canada; Jewish General Hospital, Lady Davis Institute, Montreal, Quebec, H3T 1E2, Canada
| | - Adrian Young
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, H3A 0C7, Canada; Jewish General Hospital, Lady Davis Institute, Montreal, Quebec, H3T 1E2, Canada
| | - Chantal Autexier
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, H3A 0C7, Canada; Jewish General Hospital, Lady Davis Institute, Montreal, Quebec, H3T 1E2, Canada.
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7
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Collin V, Gravel A, Kaufer BB, Flamand L. The Promyelocytic Leukemia Protein facilitates human herpesvirus 6B chromosomal integration, immediate-early 1 protein multiSUMOylation and its localization at telomeres. PLoS Pathog 2020; 16:e1008683. [PMID: 32658923 PMCID: PMC7394443 DOI: 10.1371/journal.ppat.1008683] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 07/31/2020] [Accepted: 06/04/2020] [Indexed: 02/05/2023] Open
Abstract
Human herpesvirus 6B (HHV-6B) is a betaherpesvirus capable of integrating its genome into the telomeres of host chromosomes. Until now, the cellular and/or viral proteins facilitating HHV-6B integration have remained elusive. Here we show that a cellular protein, the promyelocytic leukemia protein (PML) that forms nuclear bodies (PML-NBs), associates with the HHV-6B immediate early 1 (IE1) protein at telomeres. We report enhanced levels of SUMOylated IE1 in the presence of PML and have identified a putative SUMO Interacting Motif (SIM) within IE1, essential for its nuclear distribution, overall SUMOylation and association with PML to nuclear bodies. Furthermore, using PML knockout cell lines we made the original observation that PML is required for efficient HHV-6B integration into host chromosomes. Taken together, we could demonstrate that PML-NBs are important for IE1 multiSUMOylation and that PML plays an important role in HHV-6B integration into chromosomes, a strategy developed by this virus to maintain its genome in its host over long periods of time. Human herpesvirus 6B (HHV-6B) is a ubiquitous virus that can be life threatening in immunocompromised patients. HHV-6B is among a few other herpesviruses that integrate their genome in host chromosomes as a mean to establish dormancy. Integration of HHV-6B occurs in host telomeres, a region that protects our genome from deterioration and controls the cellular lifespan. To date, the mechanisms leading to HHV-6B integration remain elusive. Our laboratory has identified that the IE1 protein of HHV-6B associates with PML, a cellular protein that is responsible for the regulation of important cellular mechanisms including DNA recombination and repair. With the objective of understanding how IE1 is brought to PML, we discovered that PML aids the SUMOylation of IE1. This finding led us to identify a putative SUMO interaction motif on IE1 that is essentials for both its SUMOylation and IE1 oligomerization with PML-NBs. We next studied the role of PML on HHV-6B integration and identified that cells that are deficient for PML were less susceptible to HHV-6B integration. These results correlate with the fact that PML influences IE1 localization at telomeres, the site of HHV-6B integration. Our study further contributes to our understanding of the mechanisms leading to HHV-6B chromosomal integration.
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Affiliation(s)
- Vanessa Collin
- Division of Infectious Disease and Immunity, CHU de Québec Research Center, Quebec City, Quebec, Canada
| | - Annie Gravel
- Division of Infectious Disease and Immunity, CHU de Québec Research Center, Quebec City, Quebec, Canada
| | | | - Louis Flamand
- Division of Infectious Disease and Immunity, CHU de Québec Research Center, Quebec City, Quebec, Canada
- Department of microbiology, infectious disease and immunology, Faculty of Medicine, Université Laval, Quebec City, Québec, Canada
- * E-mail:
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8
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Valori V, Tus K, Laukaitis C, Harris DT, LeBeau L, Maggert KA. Human rDNA copy number is unstable in metastatic breast cancers. Epigenetics 2020; 15:85-106. [PMID: 31352858 PMCID: PMC6961696 DOI: 10.1080/15592294.2019.1649930] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 07/07/2019] [Accepted: 07/22/2019] [Indexed: 12/27/2022] Open
Abstract
Chromatin-mediated silencing, including the formation of heterochromatin, silent chromosome territories, and repressed gene promoters, acts to stabilize patterns of gene regulation and the physical structure of the genome. Reduction of chromatin-mediated silencing can result in genome rearrangements, particularly at intrinsically unstable regions of the genome such as transposons, satellite repeats, and repetitive gene clusters including the rRNA gene clusters (rDNA). It is thus expected that mutational or environmental conditions that compromise heterochromatin function might cause genome instability, and diseases associated with decreased epigenetic stability might exhibit genome changes as part of their aetiology. We find the support of this hypothesis in invasive ductal breast carcinoma, in which reduced epigenetic silencing has been previously described, by using a facile method to quantify rDNA copy number in biopsied breast tumours and pair-matched healthy tissue. We found that rDNA and satellite DNA sequences had significant copy number variation - both losses and gains of copies - compared to healthy tissue, arguing that these genome rearrangements are common in developing breast cancer. Thus, any proposed aetiology onset or progression of breast cancer should consider alterations to the epigenome, but must also accommodate concomitant changes to genome sequence at heterochromatic loci.
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Affiliation(s)
- Virginia Valori
- Department of Applied Biosciences, University of Arizona, College of Medicine, Tucson, AZ, USA
| | - Katalin Tus
- Department of Pathology, University of Arizona, College of Medicine, Tucson, AZ, USA
| | - Christina Laukaitis
- Department of Medicine, University of Arizona, College of Medicine, Tucson, AZ, USA
- University of Arizona Cancer Center, University of Arizona, College of Medicine, Tucson, AZ, USA
| | - David T. Harris
- Department of Immunobiology, University of Arizona, College of Medicine, Tucson, AZ, USA
- Arizona Health Sciences Center Biorepository, University of Arizona, College of Medicine, Tucson, AZ, USA
| | - Lauren LeBeau
- Department of Pathology, University of Arizona, College of Medicine, Tucson, AZ, USA
| | - Keith A. Maggert
- University of Arizona Cancer Center, University of Arizona, College of Medicine, Tucson, AZ, USA
- Department of Cellular and Molecular Medicine, University of Arizona, College of Medicine, Tucson, AZ, USA
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9
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Philip B, Yu DX, Silvis MR, Shin CH, Robinson JP, Robinson GL, Welker AE, Angel SN, Tripp SR, Sonnen JA, VanBrocklin MW, Gibbons RJ, Looper RE, Colman H, Holmen SL. Mutant IDH1 Promotes Glioma Formation In Vivo. Cell Rep 2019; 23:1553-1564. [PMID: 29719265 PMCID: PMC6032974 DOI: 10.1016/j.celrep.2018.03.133] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 02/23/2018] [Accepted: 03/29/2018] [Indexed: 02/08/2023] Open
Abstract
Isocitrate dehydrogenase 1 (IDH1) is the most commonly mutated gene in grade II–III glioma and secondary glioblastoma (GBM). A causal role for IDH1R132H in gliomagenesis has been proposed, but functional validation in vivo has not been demonstrated. In this study, we assessed the role of IDH1R132H in glioma development in the context of clinically relevant cooperating genetic alterations in vitro and in vivo. Immortal astrocytes expressing IDH1R132H exhibited elevated (R)-2-hydroxyglutarate levels, reduced NADPH, increased proliferation, and anchorage-independent growth. Although not sufficient on its own, IDH1R132H cooperated with PDGFA and loss of Cdkn2a, Atrx, and Pten to promote glioma development in vivo. These tumors resembled pro-neural human mutant IDH1 GBM genetically, histologically, and functionally. Our findings support the hypothesis that IDH1R132H promotes glioma development. This model enhances our understanding of the biology of IDH1R132H-driven gliomas and facilitates testing of therapeutic strategies designed to combat this deadly disease.
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Affiliation(s)
- Beatrice Philip
- Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA; Department of Surgery, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA
| | - Diana X Yu
- Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA; Department of Surgery, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA
| | - Mark R Silvis
- Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA; Department of Surgery, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA
| | - Clifford H Shin
- Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA; Department of Oncological Sciences, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA
| | - James P Robinson
- Hormel Institute, University of Minnesota, 801 16(th) Avenue NE, Austin, MN 55912, USA
| | - Gemma L Robinson
- Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA; Department of Surgery, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA
| | - Adam E Welker
- Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA
| | - Stephanie N Angel
- Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA; Department of Surgery, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA
| | - Sheryl R Tripp
- ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT 84108, USA
| | - Joshua A Sonnen
- ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT 84108, USA; Department of Pathology, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA
| | - Matthew W VanBrocklin
- Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA; Department of Surgery, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA; Department of Oncological Sciences, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA
| | - Richard J Gibbons
- MRC Molecular Haematology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Ryan E Looper
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
| | - Howard Colman
- Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA; Department of Neurosurgery, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA
| | - Sheri L Holmen
- Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA; Department of Surgery, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA; Department of Oncological Sciences, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA.
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10
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Kwon M, Lee JJ, Min J, Hwang K, Park SG, Kim E, Kim BC, Bhak J, Lee H. Brca2 abrogation engages with the alternative lengthening of telomeres via break‐induced replication. FEBS J 2019; 286:1841-1858. [DOI: 10.1111/febs.14796] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 01/21/2019] [Accepted: 02/25/2019] [Indexed: 11/30/2022]
Affiliation(s)
- Mi‐Sun Kwon
- Department of Biological Sciences Institute of Molecular Biology and Genetics (IMBG) Seoul National University South Korea
| | - Jennifer J. Lee
- Department of Biological Sciences Institute of Molecular Biology and Genetics (IMBG) Seoul National University South Korea
| | - Jaewon Min
- Department of Biological Sciences Institute of Molecular Biology and Genetics (IMBG) Seoul National University South Korea
| | - Kwangwoo Hwang
- Department of Biological Sciences Institute of Molecular Biology and Genetics (IMBG) Seoul National University South Korea
| | - Seung Gu Park
- Department of Biomedical Engineering UNIST Ulsan Korea
| | - Eun‐Hye Kim
- Department of Biomedical Engineering UNIST Ulsan Korea
| | | | - Jong Bhak
- Department of Biomedical Engineering UNIST Ulsan Korea
- Clinomics Inc. Ulsan Korea
| | - Hyunsook Lee
- Department of Biological Sciences Institute of Molecular Biology and Genetics (IMBG) Seoul National University South Korea
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11
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Juhász S, Elbakry A, Mathes A, Löbrich M. ATRX Promotes DNA Repair Synthesis and Sister Chromatid Exchange during Homologous Recombination. Mol Cell 2018; 71:11-24.e7. [PMID: 29937341 DOI: 10.1016/j.molcel.2018.05.014] [Citation(s) in RCA: 83] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 03/20/2018] [Accepted: 05/10/2018] [Indexed: 01/15/2023]
Abstract
ATRX is a chromatin remodeler that, together with its chaperone DAXX, deposits the histone variant H3.3 in pericentromeric and telomeric regions. Notably, ATRX is frequently mutated in tumors that maintain telomere length by a specific form of homologous recombination (HR). Surprisingly, in this context, we demonstrate that ATRX-deficient cells exhibit a defect in repairing exogenously induced DNA double-strand breaks (DSBs) by HR. ATRX operates downstream of the Rad51 removal step and interacts with PCNA and RFC-1, which are collectively required for DNA repair synthesis during HR. ATRX depletion abolishes DNA repair synthesis and prevents the formation of sister chromatid exchanges at exogenously induced DSBs. DAXX- and H3.3-depleted cells exhibit identical HR defects as ATRX-depleted cells, and both ATRX and DAXX function to deposit H3.3 during DNA repair synthesis. This suggests that ATRX facilitates the chromatin reconstitution required for extended DNA repair synthesis and sister chromatid exchange during HR.
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Affiliation(s)
- Szilvia Juhász
- Radiation Biology and DNA Repair, Darmstadt University of Technology, 64287 Darmstadt, Germany
| | - Amira Elbakry
- Radiation Biology and DNA Repair, Darmstadt University of Technology, 64287 Darmstadt, Germany
| | - Arthur Mathes
- Radiation Biology and DNA Repair, Darmstadt University of Technology, 64287 Darmstadt, Germany
| | - Markus Löbrich
- Radiation Biology and DNA Repair, Darmstadt University of Technology, 64287 Darmstadt, Germany.
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12
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Si X, Shao C, Li J, Jia S, Tang W, Zhang J, Yang J, Wu X, Luo Y. Loss of p21 promoted tumorigenesis in the background of telomere dysfunctions induced by TRF2 and Wrn deficiency. Int J Biol Sci 2018; 14:165-177. [PMID: 29483835 PMCID: PMC5821038 DOI: 10.7150/ijbs.23477] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 12/10/2017] [Indexed: 01/01/2023] Open
Abstract
Werner syndrome (WS) is a rare autosomal recessive progeria disease with genetic instability/cancer predisposition, thus a good model in understanding aging related carcinogenesis. Telomere dysfunction induced cellular senescence is essential in the manifestation of the WS phenotype. Our previous data has shown that p21 (encoded by Cdkn1a gene) could induce cellular senescence and suppress cellular growth of ALT (alternative lengthening of telomere) tumors derived from WS, suggested that p21 might play a key role in maintaining senescence of WS cells. To confirm the role of p21 in suppressing telomere dysfunction induced tumorigenesis, we overexpressed dominant negative protein TRF2ΔBΔM in p21-/- mouse embryonic fibroblasts (MEFs). To further stress the cell, we crossed Wrn-/-mice with p21-/- mice to obtained p21-/-Wrn-/- MEFs, and overexpressed TRF2ΔBΔM in these MEFs to induce telomere dysfunction similar to that in WS cells. Our data showed that, in the context of p21-/-TRF2ΔBΔM, loss of p21 function rescued cellular senescence, and induced p53 mutation, but did not induce tumorigenesis. However, in the set of p21-/-Wrn-/-TRF2ΔBΔM, loss of p21 function induced p53 mutation and tumorigenesis. To further verify the role of p21 in suppressing telomere dysfunction related tumorigenesis, we knocked down p21 in non-tumorigenic immortalized cells derived from WS MEFs (mTerc-/-Wrn-/-), and found that loss of p21 could induce ALT tumorigenesis, which displayed typical smear pattern of telomere length and arc-shaped telomeric DNA. In another hand, recovering telomerase activity in these MEFs could also induce tumorigenesis without affecting p21 expression level. Together our data suggested that p21 controlled cell cycle regulation played an essential role in suppressing telomere dysfunction-related tumorigenesis. These data also suggested that the genetic context is essential in determining the role of p21 in cancer prevention. Therefore, targeting p21 in the treatment of human degenerative diseases would require a personalized genetic background screen.
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Affiliation(s)
- Xiaoyu Si
- Lab of Molecular Genetics of Aging & Tumor, Faculty of Medicine, Kunming University of Science & Technology, 727 South Jing Ming Road, Chenggong County, Kunming, Yunnan Province, China, 650500.,College of Biological Engineering, Qilu University of Technology (Shandong Academy of Sciences), 3501 University Road, Changqing County, Jinan, Shandong Province, China, 250353
| | - Chihao Shao
- Lab of Molecular Genetics of Aging & Tumor, Faculty of Medicine, Kunming University of Science & Technology, 727 South Jing Ming Road, Chenggong County, Kunming, Yunnan Province, China, 650500
| | - Jing Li
- Lab of Molecular Genetics of Aging & Tumor, Faculty of Medicine, Kunming University of Science & Technology, 727 South Jing Ming Road, Chenggong County, Kunming, Yunnan Province, China, 650500.,Faculty of Environmental Science and Engineering, Kunming University of Science & Technology, 727 South Jing Ming Road, Chenggong County, Kunming, Yunnan Province, China, 650500
| | - Shuting Jia
- Lab of Molecular Genetics of Aging & Tumor, Faculty of Medicine, Kunming University of Science & Technology, 727 South Jing Ming Road, Chenggong County, Kunming, Yunnan Province, China, 650500
| | - Wenru Tang
- Lab of Molecular Genetics of Aging & Tumor, Faculty of Medicine, Kunming University of Science & Technology, 727 South Jing Ming Road, Chenggong County, Kunming, Yunnan Province, China, 650500
| | - Jihong Zhang
- Lab of Molecular Genetics of Aging & Tumor, Faculty of Medicine, Kunming University of Science & Technology, 727 South Jing Ming Road, Chenggong County, Kunming, Yunnan Province, China, 650500
| | - Julun Yang
- Faculty of Environmental Science and Engineering, Kunming University of Science & Technology, 727 South Jing Ming Road, Chenggong County, Kunming, Yunnan Province, China, 650500
| | - Xiaoming Wu
- Lab of Molecular Genetics of Aging & Tumor, Faculty of Medicine, Kunming University of Science & Technology, 727 South Jing Ming Road, Chenggong County, Kunming, Yunnan Province, China, 650500
| | - Ying Luo
- Lab of Molecular Genetics of Aging & Tumor, Faculty of Medicine, Kunming University of Science & Technology, 727 South Jing Ming Road, Chenggong County, Kunming, Yunnan Province, China, 650500.,College of Biological Engineering, Qilu University of Technology (Shandong Academy of Sciences), 3501 University Road, Changqing County, Jinan, Shandong Province, China, 250353.,Department of Pathology, Kunming General Hospital, 212 Daguan Road, Kunming, Yunnan Province, China, 650032
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13
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Chang HR, Munkhjargal A, Kim MJ, Park SY, Jung E, Ryu JH, Yang Y, Lim JS, Kim Y. The functional roles of PML nuclear bodies in genome maintenance. Mutat Res 2017; 809:99-107. [PMID: 28521962 DOI: 10.1016/j.mrfmmm.2017.05.002] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/28/2017] [Accepted: 05/04/2017] [Indexed: 02/07/2023]
Abstract
In the nucleus, there are several membraneless structures called nuclear bodies. Among them, promyelocytic leukemia nuclear bodies (PML-NBs) are involved in multiple genome maintenance pathways including the DNA damage response, DNA repair, telomere homeostasis, and p53-associated apoptosis. In response to DNA damage, PML-NBs are coalesced and divided by a fission mechanism, thus increasing their number. PML-NBs also play a role in repairing DNA double-strand breaks (DSBs) by homologous recombination (HR). Clinically, the dominant negative PML-RARα fusion protein expressed in acute promyelocytic leukemia (APL) inhibits the transactivation of downstream factors and disrupts PML function, revealing the tumor suppressor role of PML-NBs. All-trans retinoic acid and arsenic trioxide treatment has been implemented for promyelocytic leukemia to target the PML-RARα fusion protein. PML-NBs are associated with various factors implicated in genome maintenance, and are found at the sites of DNA damage. Their interaction with proteins such as p53 indicates that PML-NBs may play a significant role in apoptosis and cancer. Decades of research have revealed the importance of PML-NBs in diverse cellular pathways, yet the underlying molecular mechanisms and exact functions of PML-NBs remain elusive. In this review, PML protein modifications and the functional relevance of PML-NB and its associated factors in genome maintenance will be discussed.
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Affiliation(s)
- Hae Ryung Chang
- Department of Biological Sciences, Sookmyung Women's University, Seoul 04310, Republic of Korea
| | - Anudari Munkhjargal
- Department of Biological Sciences, Sookmyung Women's University, Seoul 04310, Republic of Korea
| | - Myung-Jin Kim
- Department of Biological Sciences, Sookmyung Women's University, Seoul 04310, Republic of Korea
| | - Seon Young Park
- Department of Biological Sciences, Sookmyung Women's University, Seoul 04310, Republic of Korea
| | - Eunyoung Jung
- Department of Biological Sciences, Sookmyung Women's University, Seoul 04310, Republic of Korea
| | - Jae-Ha Ryu
- Research Center for Cell Fate Control, Sookmyung Women's University, Seoul 04310, Republic of Korea
| | - Young Yang
- Department of Biological Sciences, Sookmyung Women's University, Seoul 04310, Republic of Korea
| | - Jong-Seok Lim
- Department of Biological Sciences, Sookmyung Women's University, Seoul 04310, Republic of Korea
| | - Yonghwan Kim
- Department of Biological Sciences, Sookmyung Women's University, Seoul 04310, Republic of Korea.
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14
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Withaferin-A kills cancer cells with and without telomerase: chemical, computational and experimental evidences. Cell Death Dis 2017; 8:e2755. [PMID: 28425984 PMCID: PMC5477593 DOI: 10.1038/cddis.2017.33] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 12/28/2016] [Accepted: 01/03/2017] [Indexed: 01/03/2023]
Abstract
Maintenance of telomere length is the most consistent attribute of cancer cells. Tightly connected to their capacity to overcome replicative mortality, it is achieved either by activation of telomerase or an Alternative mechanism of Lengthening of Telomeres (ALT). Disruption of either of these mechanisms has been shown to induce DNA damage signalling leading to senescence or apoptosis. Telomerase inhibitors are considered as potential anticancer drugs but are ineffective for ALT cancers (~15% of all cancers). Withaferin-A (Wi-A), a major constituent of the medicinal plant, Withania somnifera (Ashwagandha), has been shown to exert anti-tumour activity. However, its effect on either telomerase or ALT mechanisms has not been investigated. Here, by using isogenic cancer cells with/without telomerase, we found that Wi-A caused stronger cytotoxicity to ALT cells. It was associated with inhibition of ALT-associated promyelocytic leukemia nuclear bodies, an established marker of ALT. Comparative analyses of telomerase positive and ALT cells revealed that Wi-A caused stronger telomere dysfunction and upregulation of DNA damage response in ALT cells. Molecular computational and experimental analyses revealed that Wi-A led to Myc-Mad mediated transcriptional suppression of NBS-1, an MRN complex protein that is an essential component of the ALT mechanism. The results suggest that Wi-A could be a new candidate drug for ALT cancers.
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15
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Essential role of the Cdk2 activator RingoA in meiotic telomere tethering to the nuclear envelope. Nat Commun 2016; 7:11084. [PMID: 27025256 PMCID: PMC4820962 DOI: 10.1038/ncomms11084] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 02/19/2016] [Indexed: 11/24/2022] Open
Abstract
Cyclin-dependent kinases (CDKs) play key roles in cell cycle regulation. Genetic analysis in mice has revealed an essential role for Cdk2 in meiosis, which renders Cdk2 knockout (KO) mice sterile. Here we show that mice deficient in RingoA, an atypical activator of Cdk1 and Cdk2 that has no amino acid sequence homology to cyclins, are sterile and display meiotic defects virtually identical to those observed in Cdk2 KO mice including non-homologous chromosome pairing, unrepaired double-strand breaks, undetectable sex-body and pachytene arrest. Interestingly, RingoA is required for Cdk2 targeting to telomeres and RingoA KO spermatocytes display severely affected telomere tethering as well as impaired distribution of Sun1, a protein essential for the attachment of telomeres to the nuclear envelope. Our results identify RingoA as an important activator of Cdk2 at meiotic telomeres, and provide genetic evidence for a physiological function of mammalian Cdk2 that is not dependent on cyclins. CDKs play central roles in cell cycle regulation and are normally activated by cyclins. Here the authors show that RingoA induces a cyclin-independent function of CDK2 at meiotic telomeres, which regulates their tethering to the nuclear envelope and proper synapsis of homologous chromosomes.
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16
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Pickett HA, Reddel RR. Molecular mechanisms of activity and derepression of alternative lengthening of telomeres. Nat Struct Mol Biol 2015; 22:875-80. [PMID: 26581522 DOI: 10.1038/nsmb.3106] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 09/01/2015] [Indexed: 02/08/2023]
Abstract
Alternative lengthening of telomeres (ALT) involves homology-directed telomere synthesis. This multistep process is facilitated by loss of the ATRX or DAXX chromatin-remodeling factors and by abnormalities of the telomere nucleoprotein architecture, including altered DNA sequence and decreased TRF2 saturation. Induction of telomere-specific DNA damage triggers homology-directed searches, and NuRD-ZNF827 protein-protein interactions provide a platform for the telomeric recruitment of homologous recombination (HR) proteins. Telomere lengthening proceeds by strand exchange and template-driven DNA synthesis, which culminates in dissolution of HR intermediates.
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Affiliation(s)
- Hilda A Pickett
- Telomere Length Regulation Group, Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, Australia
| | - Roger R Reddel
- Cancer Research Unit, Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, Australia
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17
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Fan X, Chen JJ. Role of Cdk1 in DNA damage-induced G1 checkpoint abrogation by the human papillomavirus E7 oncogene. Cell Cycle 2015; 13:3249-59. [PMID: 25485505 DOI: 10.4161/15384101.2014.953879] [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] [Indexed: 01/02/2023] Open
Abstract
The high-risk human papillomavirus (HPV) E7 oncogene abrogates DNA damage-induced G1 checkpoint but the mechanism is not fully understood. The G1 kinase Cdk2 is activated in E7-expressing cells. However, whether Cdk2 is required for E7 to abrogate the G1 checkpoint is not known. Accumulating evidence implicates a role for the mitotic Cdk1 in G1/S phase transition in the absence of Cdk2. We therefore examined the expression and requirement of Cdk1 and Cdk2 in the G1 checkpoint abrogation in E7-expressing cells. Although both Cdk1 and Cdk2 were up-regulated in E7-expressing cells upon DNA damage, down-regulation of Cdk1 but not Cdk2 impairs the ability of E7 to abrogate the G1 checkpoint. Our study thus demonstrated an important role for Cdk1 in bypassing the G1 checkpoint in E7-expressing cells. To understand the mechanism by which E7 activates Cdk1, we examined the transcription factor B-Myb. Our studies demonstrated that downregulation of B-Myb reduced the steady-state level of Cdk1 and induced G1 arrest in E7-expressing cells upon DNA damage. In addition, it remains a mystery how E7 promotes cell cycle progression in the presence of Cdk inhibitor p21. As p21 binds Cdk1 with lower affinity than Cdk2, our results suggest a mechanism by which E7 bypasses the inhibitory effect of p21. Nonetheless, our studies demonstrated that p21 still possessed partial ability to arrest cells at G1 phase in E7-expressing cells. These studies shed light on mechanisms by which HPV E7 modulates cell cycle checkpoint.
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Affiliation(s)
- Xueli Fan
- a Department of Medicine ; University of Massachusetts Medical School ; Worcester , MA USA
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18
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Osterwald S, Deeg KI, Chung I, Parisotto D, Wörz S, Rohr K, Erfle H, Rippe K. PML induces compaction, TRF2 depletion and DNA damage signaling at telomeres and promotes their alternative lengthening. J Cell Sci 2015; 128:1887-1900. [DOI: 10.1242/jcs.148296] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
Abstract
ABSTRACT
The alternative lengthening of telomeres (ALT) mechanism allows cancer cells to escape senescence and apoptosis in the absence of active telomerase. A characteristic feature of this pathway is the assembly of ALT-associated promyelocytic leukemia (PML) nuclear bodies (APBs) at telomeres. Here, we dissected the role of APBs in a human ALT cell line by performing an RNA interference screen using an automated 3D fluorescence microscopy platform and advanced 3D image analysis. We identified 29 proteins that affected APB formation, which included proteins involved in telomere and chromatin organization, protein sumoylation and DNA repair. By integrating and extending these findings, we found that APB formation induced clustering of telomere repeats, telomere compaction and concomitant depletion of the shelterin protein TRF2 (also known as TERF2). These APB-dependent changes correlated with the induction of a DNA damage response at telomeres in APBs as evident by a strong enrichment of the phosphorylated form of the ataxia telangiectasia mutated (ATM) kinase. Accordingly, we propose that APBs promote telomere maintenance by inducing a DNA damage response in ALT-positive tumor cells through changing the telomeric chromatin state to trigger ATM phosphorylation.
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Affiliation(s)
- Sarah Osterwald
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum (DKFZ) & BioQuant, 69120 Heidelberg, Germany
| | - Katharina I. Deeg
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum (DKFZ) & BioQuant, 69120 Heidelberg, Germany
| | - Inn Chung
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum (DKFZ) & BioQuant, 69120 Heidelberg, Germany
| | - Daniel Parisotto
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum (DKFZ) & BioQuant, 69120 Heidelberg, Germany
| | - Stefan Wörz
- Department of Bioinformatics and Functional Genomics, Biomedical Computer Vision Group, University of Heidelberg & DKFZ, BioQuant, IPMB, 69120 Heidelberg, Germany
| | - Karl Rohr
- Department of Bioinformatics and Functional Genomics, Biomedical Computer Vision Group, University of Heidelberg & DKFZ, BioQuant, IPMB, 69120 Heidelberg, Germany
| | - Holger Erfle
- ViroQuant-CellNetworks RNAi Screening Facility, University of Heidelberg & BioQuant, 69120 Heidelberg, Germany
| | - Karsten Rippe
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum (DKFZ) & BioQuant, 69120 Heidelberg, Germany
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Chatterjee D, Bhattacharjee P, Sau TJ, Das JK, Sarma N, Bandyopadhyay AK, Roy SS, Giri AK. Arsenic exposure through drinking water leads to senescence and alteration of telomere length in humans: A case-control study in West Bengal, India. Mol Carcinog 2014; 54:800-9. [PMID: 24665044 DOI: 10.1002/mc.22150] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 02/14/2014] [Accepted: 02/25/2014] [Indexed: 12/20/2022]
Affiliation(s)
- Debmita Chatterjee
- Molecular and Human Genetics Division; CSIR-Indian Institute of Chemical Biology; Kolkata India
| | | | - Tanmoy J. Sau
- Sir Nil Ratan Sircar Medical College and Hospital; Kolkata India
| | - Jayanta K. Das
- Department of Dermatology; West Bank Hospital; Howrah, West Bengal India
| | - Nilendu Sarma
- Sir Nil Ratan Sircar Medical College and Hospital; Kolkata India
| | - Apurba K. Bandyopadhyay
- Molecular and Human Genetics Division; CSIR-Indian Institute of Chemical Biology; Kolkata India
| | - Sib Sankar Roy
- Cell Biology and Physiology Division; CSIR-Indian Institute of Chemical Biology; Kolkata India
| | - Ashok K. Giri
- Molecular and Human Genetics Division; CSIR-Indian Institute of Chemical Biology; Kolkata India
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20
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Feng X, Luo Z, Jiang S, Li F, Han X, Hu Y, Wang D, Zhao Y, Ma W, Liu D, Huang J, Songyang Z. The telomere-associated homeobox-containing protein TAH1/HMBOX1 participates in telomere maintenance in ALT cells. J Cell Sci 2013; 126:3982-9. [PMID: 23813958 DOI: 10.1242/jcs.128512] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The majority of cancer cells rely on elevated telomerase expression and activity for rapid growth and proliferation. Telomerase-negative cancer cells, by contrast, often employ the alternative lengthening of telomeres (ALT) pathway to maintain telomeres. ALT cells are characterized by long and dynamic telomeres and the presence of ALT-associated promyelocytic leukemia (PML) bodies (APBs). Previous work has shown the importance of APBs to the ALT pathway, but their formation and precise role remain unclear. Here, we demonstrate that a homeobox-containing protein known as HMBOX1 can directly bind telomeric double-stranded DNA and associate with PML nuclear bodies. Hence, we renamed this protein TAH1 for telomere-associated homeobox-containing protein 1. TAH1 knockdown significantly reduced the number of APBs and led to an increase in DNA damage response signals at telomeres. Importantly, TAH1 inhibition also notably reduced the presence of telomere C-circles, indicating altered ALT activity. Our findings point to TAH1 as a novel link between pathways that regulate DNA damage responses, PML nuclear bodies, and telomere homeostasis in ALT cells, and provide insight into how ALT cells may achieve sustained growth and proliferation independent of the telomerase.
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Affiliation(s)
- Xuyang Feng
- Key Laboratory of Gene Engineering of the Ministry of Education, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510006, China
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Chung I, Osterwald S, Deeg KI, Rippe K. PML body meets telomere: the beginning of an ALTernate ending? Nucleus 2012; 3:263-75. [PMID: 22572954 PMCID: PMC3414403 DOI: 10.4161/nucl.20326] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The unlimited proliferation potential of cancer cells requires the maintenance of their telomeres. This is frequently accomplished by reactivation of telomerase. However, in a significant fraction of tumors an alternative lengthening of telomeres (ALT) mechanism is active. The molecular mechanism of the ALT pathway remains elusive. In particular, the role of characteristic complexes of promyelocytic leukemia nuclear bodies (PML-NBs) with telomeres, the ALT-associated PML-NBs (APBs), is currently under investigation. Here, we review recent findings on the assembly, structure and functions of APBs. It is discussed how genomic aberrations in ALT-positive cancer cells could result in the formation of APBs and in ALT activity. We conclude that they are important functional intermediates in what is considered the canonical ALT pathway and discuss deregulations of cellular pathways that contribute to the emergence of the ALT phenotype.
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Affiliation(s)
- Inn Chung
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum (DKFZ) and BioQuant, Heidelberg, Germany
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22
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Modulation of telomeres in alternative lengthening of telomeres type I like human cells by the expression of werner protein and telomerase. JOURNAL OF ONCOLOGY 2012; 2012:806382. [PMID: 22545052 PMCID: PMC3321466 DOI: 10.1155/2012/806382] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 12/13/2011] [Accepted: 01/10/2012] [Indexed: 02/06/2023]
Abstract
The alternative lengthening of telomeres (ALT) is a recombination-based mechanism of telomere maintenance activated in 5–20% of human cancers. In Saccharomyces cerevisiae, survivors that arise after inactivation of telomerase can be classified as type I or type II ALT. In type I, telomeres have a tandem array structure, with each subunit consisting of a subtelomeric Y′ element and short telomere sequence. Telomeres in type II have only long telomere repeats and require Sgs1, the S. cerevisiae RecQ family helicase. We previously described the first human ALT cell line, AG11395, that has a telomere structure similar to type I ALT yeast cells. This cell line lacks the activity of the Werner syndrome protein, a human RecQ helicase. The telomeres in this cell line consist of tandem repeats containing SV40 DNA, including the origin of replication, and telomere sequence. We investigated the role of the SV40 origin of replication and the effects of Werner protein and telomerase on telomere structure and maintenance in AG11395 cells. We report that the expression of Werner protein facilitates the transition in human cells of ALT type I like telomeres to type II like telomeres in some aspects. These findings have implications for the diagnosis and treatment of cancer.
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Slatter TL, Tan X, Yuen YC, Gunningham S, Ma SS, Daly E, Packer S, Devenish C, Royds JA, Hung NA. The alternative lengthening of telomeres pathway may operate in non-neoplastic human cells. J Pathol 2012; 226:509-18. [DOI: 10.1002/path.2981] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 07/27/2011] [Accepted: 08/04/2011] [Indexed: 01/20/2023]
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Chung I, Leonhardt H, Rippe K. De novo assembly of a PML nuclear subcompartment occurs through multiple pathways and induces telomere elongation. J Cell Sci 2011; 124:3603-18. [PMID: 22045732 DOI: 10.1242/jcs.084681] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Telomerase-negative tumor cells use an alternative lengthening of telomeres (ALT) pathway that involves DNA recombination and repair to maintain their proliferative potential. The cytological hallmark of this process is the accumulation of promyelocytic leukemia (PML) nuclear protein at telomeric DNA to form ALT-associated PML bodies (APBs). Here, the de novo formation of a telomeric PML nuclear subcompartment was investigated by recruiting APB protein components. We show that functionally distinct proteins were able to initiate the formation of bona fide APBs with high efficiency in a self-organizing and self-propagating manner. These included: (1) PML and Sp100 as the constituting components of PML nuclear bodies, (2) telomere repeat binding factors 1 and 2 (TRF1 and TRF2, respectively), (3) the DNA repair protein NBS1 and (4) the SUMO E3 ligase MMS21, as well as the isolated SUMO1 domain, through an interacting domain of another protein factor. By contrast, the repair factors Rad9, Rad17 and Rad51 were less efficient in APB nucleation but were recruited to preassembled APBs. The artificially created APBs induced telomeric extension through a DNA repair mechanism, as inferred from their colocalization with sites of non-replicative DNA synthesis and histone H2A.X phosphorylation, and an increase of the telomere repeat length. These activities were absent after recruitment of the APB factors to a pericentric locus and establish APBs as functional intermediates of the ALT pathway.
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Affiliation(s)
- Inn Chung
- German Cancer Research Center & BioQuant, Research Group Genome Organization & Function, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
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25
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Osterwald S, Wörz S, Reymann J, Sieckmann F, Rohr K, Erfle H, Rippe K. A three-dimensional colocalization RNA interference screening platform to elucidate the alternative lengthening of telomeres pathway. Biotechnol J 2011; 7:103-16. [DOI: 10.1002/biot.201000474] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 03/03/2011] [Accepted: 04/04/2011] [Indexed: 01/17/2023]
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26
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Shen H, Maki CG. p53 and p21(Waf1) are recruited to distinct PML-containing nuclear foci in irradiated and Nutlin-3a-treated U2OS cells. J Cell Biochem 2011; 111:1280-90. [PMID: 20803550 DOI: 10.1002/jcb.22852] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Promyelocytic leukemia nuclear bodies (PML-NBs) are multiprotein complexes that include PML protein and localize in nuclear foci. PML-NBs are implicated in multiple stress responses, including apoptosis, DNA repair, and p53-dependent growth inhibition. ALT-associated PML bodies (APBs) are specialized PML-NBs that include telomere-repeat binding-factor TRF1 and are exclusively in telomerase-negative tumors where telomere length is maintained through alternative (ALT) recombination mechanisms. We compared cell-cycle and p53 responses in ALT-positive cancer cells (U2OS) exposed to ionizing radiation (IR) or the p53 stabilizer Nutlin-3a. Both IR and Nutlin-3a caused growth arrest and comparable induction of p53. However, p21, whose gene p53 activates, displayed biphasic induction following IR and monophasic induction following Nutlin-3a. p53 was recruited to PML-NBs 3-4 days after IR, approximately coincident with the secondary p21 increase. These p53/PML-NBs marked sites of apparently unrepaired DNA double-strand breaks (DSBs), identified by colocalization with phosphorylated histone H2AX. Both Nutlin-3a and IR caused a large increase in APBs that was dependent on p53 and p21 expression. Moreover, p21, and to a lesser extent p53, was recruited to APBs in a fraction of Nutlin-3a-treated cells. These data indicate (1) p53 is recruited to PML-NBs after IR that likely mark unrepaired DSBs, suggesting p53 may either be further activated at these sites and/or function in their repair; (2) p53-p21 pathway activation increases the percentage of APB-positive cells, (3) p21 and p53 are recruited to ALT-associated PML-NBs after Nutlin-3a treatment, suggesting that they may play a previously unrecognized role in telomere maintenance.
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Affiliation(s)
- Hong Shen
- Department of Anatomy and Cell Biology, Rush University Medical Center, 1750 W Harrison Ave., Jelke Building, Room 1306, Chicago, Illinois, USA
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Jiang WQ, Nguyen A, Cao Y, Chang ACM, Reddel RR. HP1-mediated formation of alternative lengthening of telomeres-associated PML bodies requires HIRA but not ASF1a. PLoS One 2011; 6:e17036. [PMID: 21347226 PMCID: PMC3039646 DOI: 10.1371/journal.pone.0017036] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2010] [Accepted: 01/11/2011] [Indexed: 12/20/2022] Open
Abstract
Approximately 10% of cancers use recombination-mediated Alternative Lengthening of Telomeres (ALT) instead of telomerase to prevent telomere shortening. A characteristic of cells that utilize ALT is the presence of ALT-associated PML nuclear bodies (APBs) containing (TTAGGG)n DNA, telomere binding proteins, DNA recombination proteins, and heterochromatin protein 1 (HP1). The function of APBs is unknown and it is possible that they are functionally heterogeneous. Most ALT cells lack functional p53, and restoration of the p53/p21 pathway in these cells results in growth arrest/senescence and a substantial increase in the number of large APBs that is dependent on two HP1 isoforms, HP1α and HP1γ. Here we investigated the mechanism of HP1-mediated APB formation, and found that histone chaperones, HIRA and ASF1a, are present in APBs following activation of the p53/p21 pathway in ALT cells. HIRA and ASF1a were also found to colocalize inside PML bodies in normal fibroblasts approaching senescence, providing evidence for the existence of a senescence-associated ASF1a/HIRA complex inside PML bodies, consistent with a role for these proteins in induction of senescence in both normal and ALT cells. Moreover, knockdown of HIRA but not ASF1a significantly reduced p53-mediated induction of large APBs, with a concomitant reduction of large HP1 foci. We conclude that HIRA, in addition to its physical and functional association with ASF1a, plays a unique, ASF1a-independent role, which is required for the localization of HP1 to PML bodies and thus for APB formation.
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Affiliation(s)
- Wei-Qin Jiang
- Cancer Research Unit, Children's Medical Research Institute, Westmead, New South Wales, Australia
- Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Akira Nguyen
- Cancer Research Unit, Children's Medical Research Institute, Westmead, New South Wales, Australia
- Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Ying Cao
- Cancer Research Unit, Children's Medical Research Institute, Westmead, New South Wales, Australia
- Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Andy C.-M. Chang
- Cancer Research Unit, Children's Medical Research Institute, Westmead, New South Wales, Australia
- Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Roger R. Reddel
- Cancer Research Unit, Children's Medical Research Institute, Westmead, New South Wales, Australia
- Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
- * E-mail:
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Nabetani A, Ishikawa F. Alternative lengthening of telomeres pathway: recombination-mediated telomere maintenance mechanism in human cells. J Biochem 2011; 149:5-14. [PMID: 20937668 DOI: 10.1093/jb/mvq119] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Unlimitedly proliferating cells need to acquire the telomere DNA maintenance mechanism, to counteract possible shortening through multiple rounds of replication and segregation of linear chromosomes. Most human cancer cells express telomerase whereas the other cells utilize the alternative lengthening of telomeres (ALT) pathway to elongate telomere DNA. It is suggested that ALT depends on the recombination between telomere repetitive DNAs. However, the molecular details remain unknown. Recent studies have provided evidence of special structures of telomere DNA and genes essential for the phenotypes of ALT cells. The molecular models of the ALT pathway should be validated to elucidate recombination-mediated telomere maintenance and promote the applications to anti-cancer therapy.
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Affiliation(s)
- Akira Nabetani
- Laboratory of Cell Cycle Regulation, Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University,Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
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Wong LH. Epigenetic regulation of telomere chromatin integrity in pluripotent embryonic stem cells. Epigenomics 2010; 2:639-55. [DOI: 10.2217/epi.10.49] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Telomeres are protective chromosomal structures highly conserved from primitive organisms to humans. The evolutionary conservation of telomere DNA implicates the importance of telomeric structure for basic cellular functions. Loss of telomere function causes chromosomal fusion, activation of DNA damage checkpoint responses, genome instability and impaired stem cell function. In human cells, the telomeric chromatin consists of TTAGGG repeats associated with a complex of proteins known as Shelterin. It is also organized in nucleosomes enriched with epigenetic modifications of ‘closed’ or ‘silenced’ chromatin states, including DNA hypermethylation and trimethylation of H3K9 and H4K20. These heterochromatin marks serve as a higher-order level of control of telomere length and structural integrity. Recent studies have shown that the telomere nucleosome in pluripotent embryonic stem cells is characterized by a more ‘open’ chromatin state that switches to become more repressive during differentiation. Conversely, the reprogramming of adult somatic cells into induced pluripotent cells results in the switch in telomeric chromatin from a repressive to a more open embryonic stem cell-like state, coupled with the restoration of telomere length. These findings indicate that telomeric chromatin is dynamic and reprogrammable, and has a fundamental role in the maintenance of embryonic stem cell pluripotency.
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Affiliation(s)
- Lee H Wong
- Chromosome & Chromatin Research, Murdoch Children’s Research Institute, Flemington Road, Parkville, Victoria 3052, Australia
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Abstract
The linear nature of eukaryotic chromosomes necessitates protection of their physical ends, the telomeres, because the DNA-repair machinery can misconstrue the ends as double-stranded DNA breaks. Thus, protection is crucial for avoiding an unwarranted DNA-damage response that could have catastrophic ramifications for the integrity and stability of the linear genome. In this Commentary, we attempt to define what is currently understood by the term ;telomere protection'. Delineating the defining boundaries of chromosome-end protection is important now more than ever, as it is becoming increasingly evident that, although unwanted DNA repair at telomeres must be avoided at all costs, the molecular players involved in recognition, signaling and repair of DNA damage might also serve to protect telomeres.
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Affiliation(s)
- Liana Oganesian
- The Salk Institute for Biological Studies, Molecular and Cellular Biology Department, La Jolla, CA 92037, USA
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Capes-Davis A, Theodosopoulos G, Atkin I, Drexler HG, Kohara A, MacLeod RAF, Masters JR, Nakamura Y, Reid YA, Reddel RR, Freshney RI. Check your cultures! A list of cross-contaminated or misidentified cell lines. Int J Cancer 2010; 127:1-8. [PMID: 20143388 DOI: 10.1002/ijc.25242] [Citation(s) in RCA: 330] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Continuous cell lines consist of cultured cells derived from a specific donor and tissue of origin that have acquired the ability to proliferate indefinitely. These cell lines are well-recognized models for the study of health and disease, particularly for cancer. However, there are cautions to be aware of when using continuous cell lines, including the possibility of contamination, in which a foreign cell line or microorganism is introduced without the handler's knowledge. Cross-contamination, in which the contaminant is another cell line, was first recognized in the 1950s but, disturbingly, remains a serious issue today. Many cell lines become cross-contaminated early, so that subsequent experimental work has been performed only on the contaminant, masquerading under a different name. What can be done in response-how can a researcher know if their own cell lines are cross-contaminated? Two practical responses are suggested here. First, it is important to check the literature, looking for previous work on cross-contamination. Some reports may be difficult to find and to make these more accessible, we have compiled a list of known cross-contaminated cell lines. The list currently contains 360 cell lines, drawn from 68 references. Most contaminants arise within the same species, with HeLa still the most frequently encountered (29%, 106/360) among human cell lines, but interspecies contaminants account for a small but substantial minority of cases (9%, 33/360). Second, even if there are no previous publications on cross-contamination for that cell line, it is essential to check the sample itself by performing authentication testing.
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Affiliation(s)
- Amanda Capes-Davis
- CellBank Australia - Children's Medical Research Institute, Westmead, NSW, Australia.
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Henson JD, Reddel RR. Assaying and investigating Alternative Lengthening of Telomeres activity in human cells and cancers. FEBS Lett 2010; 584:3800-11. [PMID: 20542034 DOI: 10.1016/j.febslet.2010.06.009] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 06/08/2010] [Indexed: 12/14/2022]
Abstract
Alternative Lengthening of Telomeres (ALT) activity can be deduced from the presence of telomere length maintenance in the absence of telomerase activity. More convenient assays for ALT utilize phenotypic markers of ALT activity, but only a few of these assays are potentially definitive. Here we assess each of the current ALT assays and their implications for understanding the ALT mechanism. We also review the clinical situations where availability of an ALT activity assay would be advantageous. The prevalence of ALT ranges from 25% to 60% in sarcomas and 5% to 15% in carcinomas. Patients with many of these types of ALT[+] tumors have a poor prognosis.
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Affiliation(s)
- Jeremy D Henson
- Children's Medical Research Institute, Sydney, NSW, Australia
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Abstract
Unlimited cellular proliferation depends on counteracting the telomere attrition that accompanies DNA replication. In human cancers this usually occurs through upregulation of telomerase activity, but in 10-15% of cancers - including some with particularly poor outcome - it is achieved through a mechanism known as alternative lengthening of telomeres (ALT). ALT, which is dependent on homologous recombination, is therefore an important target for cancer therapy. Although dissection of the mechanism or mechanisms of ALT has been challenging, recent advances have led to the identification of several genes that are required for ALT and the elucidation of the biological significance of some phenotypic markers of ALT. This has enabled development of a rapid assay of ALT activity levels and the construction of molecular models of ALT.
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Wong LH, McGhie JD, Sim M, Anderson MA, Ahn S, Hannan RD, George AJ, Morgan KA, Mann JR, Choo KHA. ATRX interacts with H3.3 in maintaining telomere structural integrity in pluripotent embryonic stem cells. Genome Res 2010; 20:351-60. [PMID: 20110566 PMCID: PMC2840985 DOI: 10.1101/gr.101477.109] [Citation(s) in RCA: 307] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Accepted: 12/14/2009] [Indexed: 02/07/2023]
Abstract
ATRX (alpha thalassemia/mental retardation syndrome X-linked) belongs to the SWI2/SNF2 family of chromatin remodeling proteins. Besides the ATPase/helicase domain at its C terminus, it contains a PHD-like zinc finger at the N terminus. Mutations in the ATRX gene are associated with X-linked mental retardation (XLMR) often accompanied by alpha thalassemia (ATRX syndrome). Although ATRX has been postulated to be a transcriptional regulator, its precise roles remain undefined. We demonstrate ATRX localization at the telomeres in interphase mouse embryonic stem (ES) cells in synchrony with the incorporation of H3.3 during telomere replication at S phase. Moreover, we found that chromobox homolog 5 (CBX5) (also known as heterochromatin protein 1 alpha, or HP1 alpha) is also present at the telomeres in ES cells. We show by coimmunoprecipitation that this localization is dependent on the association of ATRX with histone H3.3, and that mutating the K4 residue of H3.3 significantly diminishes ATRX and H3.3 interaction. RNAi-knockdown of ATRX induces a telomere-dysfunction phenotype and significantly reduces CBX5 enrichment at the telomeres. These findings suggest a novel function of ATRX, working in conjunction with H3.3 and CBX5, as a key regulator of ES-cell telomere chromatin.
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Affiliation(s)
- Lee H Wong
- Chromosome and Chromatin Research, Murdoch Childrens Research Institute, Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Parkville, Victoria 3052, Australia.
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Nuclear bodies: random aggregates of sticky proteins or crucibles of macromolecular assembly? Dev Cell 2009; 17:639-47. [PMID: 19922869 DOI: 10.1016/j.devcel.2009.10.017] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The principles of self-assembly and self-organization are major tenets of molecular and cellular biology. Governed by these principles, the eukaryotic nucleus is composed of numerous subdomains and compartments, collectively described as nuclear bodies. Emerging evidence reveals that associations within and between various nuclear bodies and genomic loci are dynamic and can change in response to cellular signals. This review will discuss recent progress in our understanding of how nuclear body components come together, what happens when they form, and what benefit these subcellular structures may provide to the tissues or organisms in which they are found.
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