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Ma MC, Lavi ES, Altwerger G, Lin ZP, Ratner ES. Predictive modeling of gene mutations for the survival outcomes of epithelial ovarian cancer patients. PLoS One 2024; 19:e0305273. [PMID: 38976671 PMCID: PMC11230535 DOI: 10.1371/journal.pone.0305273] [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: 12/14/2023] [Accepted: 05/27/2024] [Indexed: 07/10/2024] Open
Abstract
Epithelial ovarian cancer (EOC) has a low overall survival rate, largely due to frequent recurrence and acquiring resistance to platinum-based chemotherapy. EOC with homologous recombination (HR) deficiency has increased sensitivity to platinum-based chemotherapy because platinum-induced DNA damage cannot be repaired. Mutations in genes involved in the HR pathway are thought to be strongly correlated with favorable response to treatment. Patients with these mutations have better prognosis and an improved survival rate. On the other hand, mutations in non-HR genes in EOC are associated with increased chemoresistance and poorer prognosis. For this reason, accurate predictions in response to treatment and overall survival remain challenging. Thus, analyses of 360 EOC cases on NCI's The Cancer Genome Atlas (TCGA) program were conducted to identify novel gene mutation signatures that were strongly correlated with overall survival. We found that a considerable portion of EOC cases exhibited multiple and overlapping mutations in a panel of 31 genes. Using logistical regression modeling on mutational profiles and patient survival data from TCGA, we determined whether specific sets of deleterious gene mutations in EOC patients had impacts on patient survival. Our results showed that six genes that were strongly correlated with an increased survival time are BRCA1, NBN, BRIP1, RAD50, PTEN, and PMS2. In addition, our analysis shows that six genes that were strongly correlated with a decreased survival time are FANCE, FOXM1, KRAS, FANCD2, TTN, and CSMD3. Furthermore, Kaplan-Meier survival analysis of 360 patients stratified by these positive and negative gene mutation signatures corroborated that our regression model outperformed the conventional HR genes-based classification and prediction of survival outcomes. Collectively, our findings suggest that EOC exhibits unique mutation signatures beyond HR gene mutations. Our approach can identify a novel panel of gene mutations that helps improve the prediction of treatment outcomes and overall survival for EOC patients.
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Affiliation(s)
- Mirielle C Ma
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Ethan S Lavi
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Gary Altwerger
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Z Ping Lin
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Elena S Ratner
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, Connecticut, United States of America
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Möller C, Sharma R, Öz R, Reginato G, Cannavo E, Ceppi I, Sriram KK, Cejka P, Westerlund F. Xrs2/NBS1 promote end-bridging activity of the MRE11-RAD50 complex. Biochem Biophys Res Commun 2024; 695:149464. [PMID: 38217957 DOI: 10.1016/j.bbrc.2023.149464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 12/04/2023] [Accepted: 12/29/2023] [Indexed: 01/15/2024]
Abstract
DNA double strand breaks (DSBs) can be detrimental to the cell and need to be efficiently repaired. A first step in DSB repair is to bring the free ends in close proximity to enable ligation by non-homologous end-joining (NHEJ), while the more precise, but less available, repair by homologous recombination (HR) requires close proximity of a sister chromatid. The human MRE11-RAD50-NBS1 (MRN) complex, Mre11-Rad50-Xrs2 (MRX) in yeast, is involved in both repair pathways. Here we use nanofluidic channels to study, on the single DNA molecule level, how MRN, MRX and their constituents interact with long DNA and promote DNA bridging. Nanofluidics is a suitable method to study reactions on DNA ends since no anchoring of the DNA end(s) is required. We demonstrate that NBS1 and Xrs2 play important, but differing, roles in the DNA tethering by MRN and MRX. NBS1 promotes DNA bridging by MRN consistent with tethering of a repair template. MRX shows a "synapsis-like" DNA end-bridging, stimulated by the Xrs2 subunit. Our results highlight the different ways MRN and MRX bridge DNA, and the results are in agreement with their key roles in HR and NHEJ, respectively, and contribute to the understanding of the roles of NBS1 and Xrs2 in DSB repair.
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Affiliation(s)
- Carl Möller
- Department of Life Sciences, Chalmers University of Technology, Gothenburg, SE, 41296, Sweden
| | - Rajhans Sharma
- Department of Life Sciences, Chalmers University of Technology, Gothenburg, SE, 41296, Sweden
| | - Robin Öz
- Department of Life Sciences, Chalmers University of Technology, Gothenburg, SE, 41296, Sweden
| | - Giordano Reginato
- Institute for Research in Biomedicine, Universitá della Svizzera Italiana, Bellinzona, CH 6500, Switzerland
| | - Elda Cannavo
- Institute for Research in Biomedicine, Universitá della Svizzera Italiana, Bellinzona, CH 6500, Switzerland
| | - Ilaria Ceppi
- Institute for Research in Biomedicine, Universitá della Svizzera Italiana, Bellinzona, CH 6500, Switzerland
| | - K K Sriram
- Department of Life Sciences, Chalmers University of Technology, Gothenburg, SE, 41296, Sweden
| | - Petr Cejka
- Institute for Research in Biomedicine, Universitá della Svizzera Italiana, Bellinzona, CH 6500, Switzerland; Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH) Zürich, Switzerland
| | - Fredrik Westerlund
- Department of Life Sciences, Chalmers University of Technology, Gothenburg, SE, 41296, Sweden.
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Zhong A, Cheng CS, Lu RQ, Guo L. Suppression of NBS1 Upregulates CyclinB to Induce Olaparib Sensitivity in Ovarian Cancer. Technol Cancer Res Treat 2024; 23:15330338231212085. [PMID: 38192153 PMCID: PMC10777771 DOI: 10.1177/15330338231212085] [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: 05/27/2023] [Revised: 09/17/2023] [Accepted: 10/18/2023] [Indexed: 01/10/2024] Open
Abstract
Background: Deficiencies in DNA damage repair responses promote chemotherapy sensitivity of tumor cells. The Nibrin homolog encoding gene Nijmegen Breakage Syndrome 1 (NBS1) is a crucial component of the MRE11-RAD50-NBN complex (MRN complex) and is involved in the response to DNA double-strand breaks (DSBs) repair that has emerged as an attractive strategy to overcome tumor drug resistance, but the functional relationship between NBS1 regulated DNA damage repair and cell cycle checkpoints has not been fully elucidated. Methods: In this study, lentivirus-mediated RNAi was used to construct NBS1-downregulated cells. Flow cytometry, qPCR, and immunohistochemistry were used to explore the regulatory relationship between NBS1 and CyclinB in vivo and in vitro. Results: Our findings suggest that NBS1 deficiency leads to defective homologous recombination repair. Inhibition of NBS1 expression activates CHK1 and CyclinB signaling pathways leading to cell cycle arrest and sensitizes ovarian cancer cells to Olaparib treatment in vitro and in vivo. NBS1-deficient ovarian cancer cells tend to maintain sensitivity to chemotherapeutic drugs through activation of cell cycle checkpoints. Conclusions: NBS1 may be a potential therapeutic target for epithelial ovarian cancer as it plays a role in the regulation of the DNA damage response and cell cycle checkpoints. Suppression of NBS1 upregulates CyclinB to induce Olaparib sensitivity in ovarian cancer.
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Affiliation(s)
- Ailing Zhong
- Department of Clinical Laboratory, Fudan University, Shanghai Cancer Center, Shanghai, China
| | - Chien-shan Cheng
- Department of Integrative Oncology, Fudan University, Shanghai Cancer Center, Shanghai, China
| | - Ren quan Lu
- Department of Clinical Laboratory, Fudan University, Shanghai Cancer Center, Shanghai, China
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Lin Guo
- Department of Clinical Laboratory, Fudan University, Shanghai Cancer Center, Shanghai, China
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China
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Ding X, Gong X, Fan Y, Cao J, Zhao J, Zhang Y, Wang X, Meng K. DNA double-strand break genetic variants in patients with premature ovarian insufficiency. J Ovarian Res 2023; 16:135. [PMID: 37430352 DOI: 10.1186/s13048-023-01221-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Accepted: 06/20/2023] [Indexed: 07/12/2023] Open
Abstract
Premature ovarian insufficiency (POI) is a clinically heterogeneous disease that may seriously affect the physical and mental health of women of reproductive age. POI primarily manifests as ovarian function decline and endocrine disorders in women prior to age 40 and is an established cause of female infertility. It is crucial to elucidate the causative factors of POI, not only to expand the understanding of ovarian physiology, but also to provide genetic counselling and fertility guidance to affected patients. Factors leading to POI are multifaceted with genetic factors accounting for 7% to 30%. In recent years, an increasing number of DNA damage-repair-related genes have been linked with the occurrence of POI. Among them, DNA double-strand breaks (DSBs), one of the most damaging to DNA, and its main repair methods including homologous recombination (HR) and non-homologous end joining (NHEJ) are of particular interest. Numerous genes are known to be involved in the regulation of programmed DSB formation and damage repair. The abnormal expression of several genes have been shown to trigger defects in the overall repair pathway and induce POI and other diseases. This review summarises the DSB-related genes that may contribute to the development of POI and their potential regulatory mechanisms, which will help to further establish role of DSB in the pathogenesis of POI and provide theoretical guidance for the study of the pathogenesis and clinical treatment of this disease.
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Affiliation(s)
- Xuechun Ding
- Collaborative Innovation Center for Birth Defect Research and Transformation of Shandong Province, Jining Medical University, Jining, China
- College of Second Clinical Medical, Jining Medical University, Jining, China
| | - Xiaowei Gong
- Collaborative Innovation Center for Birth Defect Research and Transformation of Shandong Province, Jining Medical University, Jining, China
- College of Second Clinical Medical, Jining Medical University, Jining, China
| | - Yingying Fan
- Affiliated Hospital of Jining Medical University, Jining, China
| | - Jinghe Cao
- Affiliated Hospital of Jining Medical University, Jining, China
| | - Jingyu Zhao
- Collaborative Innovation Center for Birth Defect Research and Transformation of Shandong Province, Jining Medical University, Jining, China
- College of Second Clinical Medical, Jining Medical University, Jining, China
| | - Yixin Zhang
- Collaborative Innovation Center for Birth Defect Research and Transformation of Shandong Province, Jining Medical University, Jining, China
- College of Second Clinical Medical, Jining Medical University, Jining, China
| | - Xiaomei Wang
- College of Basic Medicine, Jining Medical University, Jining, China.
| | - Kai Meng
- Collaborative Innovation Center for Birth Defect Research and Transformation of Shandong Province, Jining Medical University, Jining, China.
- Lin He's Academician Workstation of New Medicine and Clinical Translation, Jining Medical University, Jining, China.
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5
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Otsuka K, Iwasaki T. Insights into radiation carcinogenesis based on dose-rate effects in tissue stem cells. Int J Radiat Biol 2023; 99:1503-1521. [PMID: 36971595 DOI: 10.1080/09553002.2023.2194398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 03/16/2023] [Indexed: 03/29/2023]
Abstract
PURPOSE Increasing epidemiological and biological evidence suggests that radiation exposure enhances cancer risk in a dose-dependent manner. This can be attributed to the 'dose-rate effect,' where the biological effect of low dose-rate radiation is lower than that of the same dose at a high dose-rate. This effect has been reported in epidemiological studies and experimental biology, although the underlying biological mechanisms are not completely understood. In this review, we aim to propose a suitable model for radiation carcinogenesis based on the dose-rate effect in tissue stem cells. METHODS We surveyed and summarized the latest studies on the mechanisms of carcinogenesis. Next, we summarized the radiosensitivity of intestinal stem cells and the role of dose-rate in the modulation of stem-cell dynamics after irradiation. RESULTS Consistently, driver mutations can be detected in most cancers from past to present, supporting the hypothesis that cancer progression is initiated by the accumulation of driver mutations. Recent reports demonstrated that driver mutations can be observed even in normal tissues, which suggests that the accumulation of mutations is a necessary condition for cancer progression. In addition, driver mutations in tissue stem cells can cause tumors, whereas they are not sufficient when they occur in non-stem cells. For non-stem cells, tissue remodeling induced by marked inflammation after the loss of tissue cells is important in addition to the accumulation of mutations. Therefore, the mechanism of carcinogenesis differs according to the cell type and magnitude of stress. In addition, our results indicated that non-irradiated stem cells tend to be eliminated from three-dimensional cultures of intestinal stem cells (organoids) composed of irradiated and non-irradiated stem cells, supporting the stem-cell competition. CONCLUSIONS We propose a unique scheme in which the dose-rate dependent response of intestinal stem cells incorporates the concept of the threshold of stem-cell competition and context-dependent target shift from stem cells to whole tissue. The concept highlights four key issues that should be considered in radiation carcinogenesis: i.e. accumulation of mutations; tissue reconstitution; stem-cell competition; and environmental factors like epigenetic modifications.
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Affiliation(s)
- Kensuke Otsuka
- Biology and Environmental Chemistry Division, Sustainable System Research Laboratory, Central Research Institute of Electric Power Industry, Tokyo, Japan
| | - Toshiyasu Iwasaki
- Strategy and Planning Division, Sustainable System Research Laboratory, Central Research Institute of Electric Power Industry, Tokyo, Japan
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6
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Sohn EJ, Goralsky JA, Shay JW, Min J. The Molecular Mechanisms and Therapeutic Prospects of Alternative Lengthening of Telomeres (ALT). Cancers (Basel) 2023; 15:cancers15071945. [PMID: 37046606 PMCID: PMC10093677 DOI: 10.3390/cancers15071945] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 03/14/2023] [Accepted: 03/15/2023] [Indexed: 04/14/2023] Open
Abstract
As detailed by the end replication problem, the linear ends of a cell's chromosomes, known as telomeres, shorten with each successive round of replication until a cell enters into a state of growth arrest referred to as senescence. To maintain their immortal proliferation capacity, cancer cells must employ a telomere maintenance mechanism, such as telomerase activation or the Alternative Lengthening of Telomeres pathway (ALT). With only 10-15% of cancers utilizing the ALT mechanism, progress towards understanding its molecular components and associated hallmarks has only recently been made. This review analyzes the advances towards understanding the ALT pathway by: (1) detailing the mechanisms associated with engaging the ALT pathway as well as (2) identifying potential therapeutic targets of ALT that may lead to novel cancer therapeutic treatments. Collectively, these studies indicate that the ALT molecular mechanisms involve at least two distinct pathways induced by replication stress and damage at telomeres. We suggest exploiting tumor dependency on ALT is a promising field of study because it suggests new approaches to ALT-specific therapies for cancers with poorer prognosis. While substantial progress has been made in the ALT research field, additional progress will be required to realize these advances into clinical practices to treat ALT cancers and improve patient prognoses.
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Affiliation(s)
- Eric J Sohn
- Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Julia A Goralsky
- Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Jerry W Shay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA
| | - Jaewon Min
- Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
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7
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Wang X, Huang Z, Li L, Yang Y, Zhang J, Wang L, Yuan J, Li Y. The Role of Alternative Splicing Factors, DDB2-Related Ageing and DNA Damage Repair in the Progression and Prognosis of Stomach Adenocarcinoma Patients. Genes (Basel) 2022; 14:genes14010039. [PMID: 36672781 PMCID: PMC9858704 DOI: 10.3390/genes14010039] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 12/08/2022] [Accepted: 12/20/2022] [Indexed: 12/25/2022] Open
Abstract
DNA damage response is a key signal transduction pathway in triggering ageing and tumor progression. Abnormal alternative splicing (AS) is associated with tumors and ageing. However, the role of AS factors associated with DNA damage repair and ageing in stomach adenocarcinoma (STAD) remains unclear. We downloaded the percentage of splicing (PSI) values for AS in STAD from the TCGA SpliceSeq database. The PSI values of DNA repair gene AS events were integrated with STAD patient survival data for Cox regression analysis. The prediction model for the overall survival (OS) was constructed by the clinical traits. The tumor immune microenvironment was analyzed by CIBERSORT and ESTIMATE. We detected 824 AS events originating from 166 DNA repair genes. Cox regression analysis provided 21 prognostic AS events connected with OS statistically, and a prognostic prediction model was constructed. The expression of these AS factors was higher in STAD tumors. DDB2 high senescence levels were associated with active immune responses and better survival in STAD patients. We built a novel prognostic model founded on DNA repair genes with AS events and identified that DDB2 may be a potential biomarker to apply in clinics.
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Affiliation(s)
- Xinshu Wang
- Postgraduate Training Base of Jinzhou Medical University, Shanghai East Hospital, Shanghai 200120, China
| | - Zhiyuan Huang
- Research Center for Translational Medicine, East Hospital, Tongji University, School of Medicine, Shanghai 200120, China
| | - Lei Li
- Research Center for Translational Medicine, East Hospital, Tongji University, School of Medicine, Shanghai 200120, China
| | - Yuntong Yang
- Research Center for Translational Medicine, East Hospital, Tongji University, School of Medicine, Shanghai 200120, China
| | - Jiyuan Zhang
- Research Center for Translational Medicine, East Hospital, Tongji University, School of Medicine, Shanghai 200120, China
| | - Li Wang
- Research Center for Translational Medicine, East Hospital, Tongji University, School of Medicine, Shanghai 200120, China
| | - Jian Yuan
- Research Center for Translational Medicine, East Hospital, Tongji University, School of Medicine, Shanghai 200120, China
- Department of Biochemistry and Molecular Biology, Tongji University School of Medicine, Shanghai 200120, China
- Correspondence: (J.Y.); (Y.L.); Tel.: +86-138-1823-3596 (J.Y.); +86-188-1730-0177 (Y.L.)
| | - Yunhui Li
- Research Center for Translational Medicine, East Hospital, Tongji University, School of Medicine, Shanghai 200120, China
- Ji’an Hospital, Shanghai East Hospital, Ji’an 343000, China
- Correspondence: (J.Y.); (Y.L.); Tel.: +86-138-1823-3596 (J.Y.); +86-188-1730-0177 (Y.L.)
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8
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NBS1 I171V variant underlies individual differences in chromosomal radiosensitivity within human populations. Sci Rep 2021; 11:19661. [PMID: 34608183 PMCID: PMC8490386 DOI: 10.1038/s41598-021-98673-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 09/13/2021] [Indexed: 02/02/2023] Open
Abstract
Genetic information is protected against a variety of genotoxins including ionizing radiation (IR) through the DNA double-strand break (DSB) repair machinery. Genome-wide association studies and clinical sequencing of cancer patients have suggested that a number of variants in the DNA DSB repair genes might underlie individual differences in chromosomal radiosensitivity within human populations. However, the number of established variants that directly affect radiosensitivity is still limited. In this study, we performed whole-exome sequencing of 29 Japanese ovarian cancer patients and detected the NBS1 I171V variant, which is estimated to exist at a rate of approximately 0.15% in healthy human populations, in one patient. To clarify whether this variant indeed contributes to chromosomal radiosensitivity, we generated NBS1 I171V variant homozygous knock-in HCT116 cells and mice using the CRISPR/Cas9 system. Radiation-induced micronucleus formation and chromosomal aberration frequency were significantly increased in both HCT116 cells and mouse embryonic fibroblasts (MEFs) with knock-in of the NBS1 I171V variant compared with the levels in wild-type cells. These results suggested that the NBS1 I171V variant might be a genetic factor underlying individual differences in chromosomal radiosensitivity.
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9
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Yin L, Zhu Z, Huang L, Luo X, Li Y, Xiao C, Yang J, Wang J, Zou Q, Tao L, Kang Z, Tang R, Wang M, Fu S. DNA repair- and nucleotide metabolism-related genes exhibit differential CHG methylation patterns in natural and synthetic polyploids (Brassica napus L.). HORTICULTURE RESEARCH 2021; 8:142. [PMID: 34193846 PMCID: PMC8245426 DOI: 10.1038/s41438-021-00576-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 03/29/2021] [Accepted: 04/07/2021] [Indexed: 05/03/2023]
Abstract
Polyploidization plays a crucial role in the evolution of angiosperm species. Almost all newly formed polyploids encounter genetic or epigenetic instabilities. However, the molecular mechanisms contributing to genomic instability in synthetic polyploids have not been clearly elucidated. Here, we performed a comprehensive transcriptomic and methylomic analysis of natural and synthetic polyploid rapeseeds (Brassica napus). Our results showed that the CHG methylation levels of synthetic rapeseed in different genomic contexts (genes, transposon regions, and repeat regions) were significantly lower than those of natural rapeseed. The total number and length of CHG-DMRs between natural and synthetic polyploids were much greater than those of CG-DMRs and CHH-DMRs, and the genes overlapping with these CHG-DMRs were significantly enriched in DNA damage repair and nucleotide metabolism pathways. These results indicated that CHG methylation may be more sensitive than CG and CHH methylation in regulating the stability of the polyploid genome of B. napus. In addition, many genes involved in DNA damage repair, nucleotide metabolism, and cell cycle control were significantly differentially expressed between natural and synthetic rapeseeds. Our results highlight that the genes related to DNA repair and nucleotide metabolism display differential CHG methylation patterns between natural and synthetic polyploids and reveal the potential connection between the genomic instability of polyploid plants with DNA methylation defects and dysregulation of the DNA repair system. In addition, it was found that the maintenance of CHG methylation in B. napus might be partially regulated by MET1. Our study provides novel insights into the establishment and evolution of polyploid plants and offers a potential idea for improving the genomic stability of newly formed Brassica polyploids.
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Affiliation(s)
- Liqin Yin
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China.
- College of Life Sciences, Sichuan University, 29 Wangjiang Road, Chengdu, China.
| | - Zhendong Zhu
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China
| | - Liangjun Huang
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China
- Agricultural College, Sichuan Agricultural University, 211 Huimin Road, Chengdu, China
| | - Xuan Luo
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China
- Agricultural College, Sichuan Agricultural University, 211 Huimin Road, Chengdu, China
| | - Yun Li
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China
| | - Chaowen Xiao
- College of Life Sciences, Sichuan University, 29 Wangjiang Road, Chengdu, China
| | - Jin Yang
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China
| | - Jisheng Wang
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China
| | - Qiong Zou
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China
| | - Lanrong Tao
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China
| | - Zeming Kang
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China
| | - Rong Tang
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China
| | - Maolin Wang
- College of Life Sciences, Sichuan University, 29 Wangjiang Road, Chengdu, China.
| | - Shaohong Fu
- Institute of Crop Research, Chengdu Academy of Agricultural and Forestry Sciences, 200 Nongke Road, Chengdu, China.
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10
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p85β alters response to EGFR inhibitor in ovarian cancer through p38 MAPK-mediated regulation of DNA repair. Neoplasia 2021; 23:718-730. [PMID: 34144267 PMCID: PMC8220107 DOI: 10.1016/j.neo.2021.05.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 05/14/2021] [Accepted: 05/18/2021] [Indexed: 11/24/2022] Open
Abstract
EGFR signaling promotes ovarian cancer tumorigenesis, and high EGFR expression correlates with poor prognosis. However, EGFR inhibitors alone have demonstrated limited clinical benefit for ovarian cancer patients, owing partly to tumor resistance and the lack of predictive biomarkers. Cotargeting EGFR and the PI3K pathway has been previously shown to yield synergistic antitumor effects in ovarian cancer. Therefore, we reasoned that PI3K may affect cellular response to EGFR inhibition. In this study, we revealed PI3K isoform-specific effects on the sensitivity of ovarian cancer cells to the EGFR inhibitor erlotinib. Gene silencing of PIK3CA (p110α) and PIK3CB (p110β) rendered cells more susceptible to erlotinib. In contrast, low expression of PIK3R2 (p85β) was associated with erlotinib resistance. Depletion of PIK3R2, but not PIK3CA or PIK3CB, led to increased DNA damage and reduced level of the nonhomologous end joining DNA repair protein BRD4. Intriguingly, these defects in DNA repair were reversed upon erlotinib treatment, which caused activation and nuclear import of p38 MAPK to promote DNA repair with increased protein levels of 53BP1 and BRD4 and foci formation of 53BP1. Remarkably, inhibition of p38 MAPK or BRD4 re-sensitized PIK3R2-depleted cells to erlotinib. Collectively, these data suggest that p38 MAPK activation and the subsequent DNA repair serve as a resistance mechanism to EGFR inhibitor. Combined inhibition of EGFR and p38 MAPK or DNA repair may maximize the therapeutic potential of EGFR inhibitor in ovarian cancer.
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Wang YY, Chen YK, Lo S, Chi TC, Chen YH, Hu SCS, Chen YW, Jiang SS, Tsai FY, Liu W, Li RN, Hsieh YC, Huang CJ, Yuan SSF. MRE11 promotes oral cancer progression through RUNX2/CXCR4/AKT/FOXA2 signaling in a nuclease-independent manner. Oncogene 2021; 40:3510-3532. [PMID: 33927349 PMCID: PMC8134045 DOI: 10.1038/s41388-021-01698-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 01/28/2021] [Accepted: 02/04/2021] [Indexed: 01/23/2023]
Abstract
MRE11, the nuclease component of RAD50/MRE11/NBS1 DNA repair complex which is essential for repair of DNA double-strand-breaks in normal cells, has recently garnered attention as a critical factor in solid tumor development. Herein we report the crucial role of MRE11 in oral cancer progression in a nuclease-independent manner and delineate its key downstream effectors including CXCR4. MRE11 expression in oral cancer samples was positively associated with tumor size, cancer stage and lymph node metastasis, and was predictive of poorer patient survival and radiotherapy resistance. MRE11 promoted cell proliferation/migration/invasion in a nuclease-independent manner but enhanced radioresistance via a nuclease-dependent pathway. The nuclease independent promotion of EMT and metastasis was mediated by RUNX2, CXCR4, AKT, and FOXA2, while CXCR4 neutralizing antibody mitigated these effects in vitro and in vivo. Collectively, MRE11 may serve as a crucial prognostic factor and therapeutic target in oral cancer, displaying dual nuclease dependent and independent roles that permit separate targeting of tumor vulnerabilities in oral cancer treatment.
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Affiliation(s)
- Yen-Yun Wang
- School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.,Translational Research Center, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.,Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.,Center for Cancer Research, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Yuk-Kwan Chen
- School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.,Center for Cancer Research, Kaohsiung Medical University, Kaohsiung, Taiwan.,Division of Oral Pathology & Maxillofacial Radiology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.,Oral & Maxillofacial Imaging Center, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Steven Lo
- College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Tsung-Chen Chi
- Translational Research Center, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Yi-Hua Chen
- Translational Research Center, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Stephen Chu-Sung Hu
- Department of Dermatology, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.,Department of Dermatology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Ya-Wen Chen
- National Institute of Cancer Research, National Health Research Institutes, Miaoli, Taiwan
| | - Shih Sheng Jiang
- National Institute of Cancer Research, National Health Research Institutes, Miaoli, Taiwan
| | - Fang-Yu Tsai
- National Institute of Cancer Research, National Health Research Institutes, Miaoli, Taiwan
| | - Wangta Liu
- Center for Cancer Research, Kaohsiung Medical University, Kaohsiung, Taiwan.,Department of Biotechnology, College of Life Science, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Ruei-Nian Li
- Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Ya-Ching Hsieh
- Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Chih-Jen Huang
- Department of Radiation Oncology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.,Department of Radiation Oncology, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Shyng-Shiou F Yuan
- Translational Research Center, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan. .,Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan. .,Center for Cancer Research, Kaohsiung Medical University, Kaohsiung, Taiwan. .,Department of Obstetrics and Gynecology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan. .,Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan. .,Department of Biological Science and Technology, College of Biological Science and Technology, National ChiaoTung University, Hsinchu, Taiwan. .,Center For Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Chiao Tung University, Hsinchu, Taiwan.
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12
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Zhou S, Cai Y, Liu X, Jin L, Wang X, Ma W, Zhang T. Role of H2B mono-ubiquitination in the initiation and progression of cancer. Bull Cancer 2021; 108:385-398. [PMID: 33685627 DOI: 10.1016/j.bulcan.2020.12.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 12/04/2020] [Accepted: 12/11/2020] [Indexed: 01/07/2023]
Abstract
Numerous epigenetic alterations are observed in cancer cells, and dysregulation of mono-ubiquitination of histone H2B (H2Bub1) has often been linked to tumorigenesis. H2Bub1 is a dynamic post-translational histone modification associated with transcriptional elongation and DNA damage response. Histone H2B monoubiquitination occurs in the site of lysine 120, written predominantly by E3 ubiquitin ligases RNF20/RNF40 and deubiquitinated by ubiquitin specific peptidase 22 (USP22). RNF20/40 is often altered in the primary tumors including colorectal cancer, breast cancer, ovarian cancer, prostate cancer, and lung cancer, and the loss of H2Bub1 is usually associated with poor prognosis in tumor patients. The purpose of this review is to summarize the current knowledge of H2Bub1 in transcription, DNA damage response and primary tumors. This review also provides novel options for exploiting the potential therapeutic target H2Bub1 in personalized cancer therapy.
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Affiliation(s)
- Sa Zhou
- Tianjin University of Science and Technology, College of Biotechnology, Tianjin 300457, PR China
| | - Yuqiao Cai
- Tianjin University of Science and Technology, College of Biotechnology, Tianjin 300457, PR China
| | - Xinyi Liu
- Tianjin University of Science and Technology, College of Biotechnology, Tianjin 300457, PR China
| | - Lijun Jin
- Tianjin University of Science and Technology, College of Biotechnology, Tianjin 300457, PR China
| | - Xiaoqin Wang
- Beijing University of Agriculture, Key Laboratory of Urban Agriculture (North) of Ministry of Agriculture, Beijing 102206, PR China
| | - Wenjian Ma
- Tianjin University of Science and Technology, College of Biotechnology, Tianjin 300457, PR China; Qilu Institute of Technology, Shandong 250200, PR China.
| | - Tongcun Zhang
- Tianjin University of Science and Technology, College of Biotechnology, Tianjin 300457, PR China; Wuhan University of Science and Technology, Institute of Biology and Medicine, Wuhan 430081, PR China.
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13
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Sakamoto Y, Kokuta T, Teshigahara A, Iijima K, Kitao H, Takata M, Tauchi H. Mitotic cells can repair DNA double-strand breaks via a homology-directed pathway. JOURNAL OF RADIATION RESEARCH 2021; 62:25-33. [PMID: 33009557 PMCID: PMC7779344 DOI: 10.1093/jrr/rraa095] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 08/21/2020] [Indexed: 05/04/2023]
Abstract
The choice of repair pathways of DNA double-strand breaks (DSBs) is dependent upon the cell cycle phases. While homologous recombination repair (HRR) is active between the S and G2 phases, its involvement in mitotic DSB repair has not been examined in detail. In the present study, we developed a new reporter assay system to detect homology-directed repair (HDR), a major pathway used for HRR, in combination with an inducible DSB-generation system. As expected, the maximal HDR activity was observed in the late S phase, along with minimal activity in the G1 phase and at the G1/S boundary. Surprisingly, significant HDR activity was observed in M phase, and the repair efficiency was similar to that observed in late S phase. HDR was also confirmed in metaphase cells collected with continuous colcemid exposure. ChIP assays revealed the recruitment of RAD51 to the vicinity of DSBs in M phase. In addition, the ChIP assay for gamma-H2AX and phosphorylated DNA-PKcs indicated that a part of M-phase cells with DSBs could proceed into the next G1 phase. These results provide evidence showing that a portion of mitotic cell DSBs are undoubtedly repaired through action of the HDR repair pathway.
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Affiliation(s)
- Yuki Sakamoto
- Department of Biological Sciences, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512, Japan
| | - Tetsuya Kokuta
- Department of Biological Sciences, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512, Japan
| | - Ai Teshigahara
- Department of Biological Sciences, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512, Japan
| | - Kenta Iijima
- Department of Biological Sciences, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512, Japan
- Department of Cancer Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan
| | - Hiroyuki Kitao
- Department of Molecular Cancer Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812-8582, Japan
| | - Minoru Takata
- Radiation Biology Center, Kyoto University, Yoshida-Konoe Cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hiroshi Tauchi
- Corresponding author. Department of Biological Sciences, Faculty of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512, Japan. Tel: +81-29-228-8383; Fax: +81-29-228-8403;
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14
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OsMre11 Is Required for Mitosis during Rice Growth and Development. Int J Mol Sci 2020; 22:ijms22010169. [PMID: 33375295 PMCID: PMC7795355 DOI: 10.3390/ijms22010169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 12/22/2020] [Accepted: 12/22/2020] [Indexed: 11/16/2022] Open
Abstract
Meiotic recombination 11 (Mre11) is a relatively conserved nuclease in various species. Mre11 plays important roles in meiosis and DNA damage repair in yeast, humans and Arabidopsis, but little research has been done on mitotic DNA replication and repair in rice. Here, it was found that Mre11 was an extensively expressed gene among the various tissues and organs of rice, and loss-of-function of Mre11 resulted in severe defects of vegetative and reproductive growth, including dwarf plants, abnormally developed male and female gametes, and completely abortive seeds. The decreased number of cells in the apical meristem and the appearance of chromosomal fragments and bridges during the mitotic cell cycle in rice mre11 mutant roots revealed an essential role of OsMre11. Further research showed that DNA replication was suppressed, and a large number of DNA strand breaks occurred during the mitotic cell cycle of rice mre11 mutants. The expression of OsMre11 was up-regulated with the treatment of hydroxyurea and methyl methanesulfonate. Moreover, OsMre11 could form a complex with OsRad50 and OsNbs1, and they might function together in non-homologous end joining and homologous recombination repair pathways. These results indicated that OsMre11 plays vital roles in DNA replication and damage repair of the mitotic cell cycle, which ensure the development and fertility of rice by maintaining genome stability.
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15
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BET-Inhibitor I-BET762 and PARP-Inhibitor Talazoparib Synergy in Small Cell Lung Cancer Cells. Int J Mol Sci 2020; 21:ijms21249595. [PMID: 33339368 PMCID: PMC7766292 DOI: 10.3390/ijms21249595] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 12/07/2020] [Accepted: 12/14/2020] [Indexed: 12/21/2022] Open
Abstract
Small cell lung cancer (SCLC) is an aggressive type of lung cancer with high mortality that is caused by frequent relapses and acquired resistance. Despite that several target-based approaches with potential therapeutic impact on SCLC have been identified, numerous targeted drugs have not been successful in providing improvements in cancer patients when used as single agents. A combination of targeted therapies could be a strategy to induce maximum lethal effects on cancer cells. As a starting point in the development of new drug combination strategies for the treatment of SCLC, we performed a mid-throughput screening assay by treating a panel of SCLC cell lines with BETi or AKi in combination with PARPi or EZH2i. We observed drug synergy between I-BET762 and Talazoparib, BETi and PARPi, respectively, in SCLC cells. Combinatorial efficacy was observed in MYCs-amplified and MYCs-wt SCLC cells over SCLC cells with impaired MYC signaling pathway or non-tumor cells. We indicate that drug synergy between I-BET762 and Talazoparib is associated with the attenuation HR-DSBR process and the downregulation of various players of DNA damage response by BET inhibition, such as CHEK2, PTEN, NBN, and FANCC. Our results provide a rationale for the development of new combinatorial strategies for the treatment of SCLC.
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16
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Kiran KR, Deepika VB, Swathy PS, Prasad K, Kabekkodu SP, Murali TS, Satyamoorthy K, Muthusamy A. ROS-dependent DNA damage and repair during germination of NaCl primed seeds. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2020; 213:112050. [PMID: 33075649 DOI: 10.1016/j.jphotobiol.2020.112050] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 09/08/2020] [Accepted: 10/05/2020] [Indexed: 10/23/2022]
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17
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Piatosa B, Wolska-Kuśnierz B, Tkaczyk K, Heropolitanska-Pliszka E, Grycuk U, Wakulinska A, Gregorek H. T Lymphocytes in Patients With Nijmegen Breakage Syndrome Demonstrate Features of Exhaustion and Senescence in Flow Cytometric Evaluation of Maturation Pathway. Front Immunol 2020; 11:1319. [PMID: 32695108 PMCID: PMC7338427 DOI: 10.3389/fimmu.2020.01319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 05/26/2020] [Indexed: 01/10/2023] Open
Abstract
Patients with Nijmegen Breakage Syndrome (NBS) suffer from recurrent infections due to humoral and cellular immune deficiency. Despite low number of T lymphocytes and their maturation defect, the clinical manifestations of cell-mediated deficiency are not as severe as in case of patients with other types of combined immune deficiencies and similar T cell lymphopenia. In this study, multicolor flow cytometry was used for evaluation of peripheral T lymphocyte maturation according to the currently known differentiation pathway, in 46 patients with genetically confirmed NBS and 46 sex and age-matched controls. Evaluation of differential expression of CD27, CD31, CD45RA, CD95, and CD197 revealed existence of cell subsets so far not described in NBS patients. Although recent thymic emigrants and naïve T lymphocyte cell populations were significantly lower, the generation of antigen-primed T cells was similar or even greater in NBS patients than in healthy controls. Moreover, the senescent and exhausted T cell populations defined by expression of CD57, KLRG1, and PD1 were more numerous than in healthy people. Although this hypothesis needs further investigations, such properties might be related to an increased susceptibility to malignancy and milder clinical course than expected in view of T cell lymphopenia in patients with NBS.
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Affiliation(s)
- Barbara Piatosa
- Histocompatibility Laboratory, Children's Memorial Health Institute, Warsaw, Poland
| | | | - Katarzyna Tkaczyk
- Histocompatibility Laboratory, Children's Memorial Health Institute, Warsaw, Poland
| | | | - Urszula Grycuk
- Histocompatibility Laboratory, Children's Memorial Health Institute, Warsaw, Poland
| | - Anna Wakulinska
- Department of Oncology, Children's Memorial Health Institute, Warsaw, Poland
| | - Hanna Gregorek
- Department of Microbiology and Clinical Immunology, Children's Memorial Health Institute, Warsaw, Poland
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18
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Li D, Ye L, Lei Y, Wan J, Chen H. Downregulation of FoxM1 sensitizes nasopharyngeal carcinoma cells to cisplatin via inhibition of MRN-ATM-mediated DNA repair. BMB Rep 2019. [PMID: 30638177 PMCID: PMC6476488 DOI: 10.5483/bmbrep.2019.52.3.249] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Chemoresistance is the primary obstacle in the treatment of locally advanced and metastatic nasopharyngeal carcinoma (NPC). Recent evidence suggests that the transcription factor forkhead box M1 (FoxM1) is involved in chemoresistance. Our group previously confirmed that FoxM1 is overexpressed in NPC. In this study, we investigated the role of FoxM1 in cisplatin resistance of the cell lines 5–8F and HONE-1 and explored its possible mechanism. Our results showed that FoxM1 and NBS1 were both overexpressed in NPC tissues based on data from the GSE cohort (GSE12452). Then, we measured FoxM1 levels in NPC cells and found FoxM1 was overexpressed in NPC cell lines and could be stimulated by cisplatin. MTT and clonogenic assays, flow cytometry, γH2AX immunofluorescence, qRT-PCR, and western blotting revealed that downregulation of FoxM1 sensitized NPC cells to cisplatin and reduced the repair of cisplatin-induced DNA double-strand breaks via inhibition of the MRN (MRE11-RAD50-NBS1)-ATM axis, which might be related to the ability of FoxM1 to regulate NBS1. Subsequently, we demonstrated that enhanced sensitivity of FoxM1 knockdown cells could be reduced by overexpression of NBS1. Taken together, our data demonstrate that downregulation of FoxM1 could improve the sensitivity of NPC cells to cisplatin through inhibition of MRN-ATM-mediated DNA repair, which could be related to FoxM1-dependent regulation of NBS1.
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Affiliation(s)
- Dandan Li
- Department of Otolaryngology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016; Laboratory Research Center, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016, China
| | - Lin Ye
- Department of cardiothoracic surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China
| | - Yue Lei
- Laboratory Research Center, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016, China
| | - Jie Wan
- Department of Otolaryngology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016; Laboratory Research Center, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016, China
| | - Hongyan Chen
- Department of Otolaryngology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016, China
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19
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Li D, Ye L, Lei Y, Wan J, Chen H. Downregulation of FoxM1 sensitizes nasopharyngeal carcinoma cells to cisplatin via inhibition of MRN-ATM-mediated DNA repair. BMB Rep 2019; 52:208-213. [PMID: 30638177 PMCID: PMC6476488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Revised: 11/13/2018] [Accepted: 01/10/2019] [Indexed: 12/17/2023] Open
Abstract
Chemoresistance is the primary obstacle in the treatment of locally advanced and metastatic nasopharyngeal carcinoma (NPC). Recent evidence suggests that the transcription factor forkhead box M1 (FoxM1) is involved in chemoresistance. Our group previously confirmed that FoxM1 is overexpressed in NPC. In this study, we investigated the role of FoxM1 in cisplatin resistance of the cell lines 5-8F and HONE-1 and explored its possible mechanism. Our results showed that FoxM1 and NBS1 were both overexpressed in NPC tissues based on data from the GSE cohort (GSE12452). Then, we measured FoxM1 levels in NPC cells and found FoxM1 was overexpressed in NPC cell lines and could be stimulated by cisplatin. MTT and clonogenic assays, flow cytometry, γH2AX immunofluorescence, qRT-PCR, and western blotting revealed that downregulation of FoxM1 sensitized NPC cells to cisplatin and reduced the repair of cisplatin-induced DNA double-strand breaks via inhibition of the MRN (MRE11-RAD50-NBS1)-ATM axis, which might be related to the ability of FoxM1 to regulate NBS1. Subsequently, we demonstrated that enhanced sensitivity of FoxM1 knockdown cells could be reduced by overexpression of NBS1. Taken together, our data demonstrate that downregulation of FoxM1 could improve the sensitivity of NPC cells to cisplatin through inhibition of MRN-ATM-mediated DNA repair, which could be related to FoxM1-dependent regulation of NBS1. [BMB Reports 2019; 52(3): 208-213].
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Affiliation(s)
- Dandan Li
- Department of Otolaryngology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016,
China
- Laboratory Research Center, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016,
China
| | - Lin Ye
- Department of cardiothoracic surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016,
China
| | - Yue Lei
- Laboratory Research Center, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016,
China
| | - Jie Wan
- Department of Otolaryngology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016,
China
- Laboratory Research Center, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016,
China
| | - Hongyan Chen
- Department of Otolaryngology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 40016,
China
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20
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Alblihy A, Mesquita KA, Sadiq MT, Madhusudan S. Development and implementation of precision therapies targeting base-excision DNA repair in BRCA1-associated tumors. EXPERT REVIEW OF PRECISION MEDICINE AND DRUG DEVELOPMENT 2019. [DOI: 10.1080/23808993.2019.1567266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Adel Alblihy
- Translational Oncology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham University Hospitals, Nottingham, UK
| | - Katia A. Mesquita
- Translational Oncology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham University Hospitals, Nottingham, UK
| | - Maaz T. Sadiq
- Department of Oncology, Nottingham University Hospitals, City Hospital Campus, Nottingham, UK
| | - Srinivasan Madhusudan
- Translational Oncology, Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham University Hospitals, Nottingham, UK
- Department of Oncology, Nottingham University Hospitals, City Hospital Campus, Nottingham, UK
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21
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Myler LR, Soniat MM, Zhang X, Deshpande RA, Paull TT, Finkelstein IJ. Purification and Biophysical Characterization of the Mre11-Rad50-Nbs1 Complex. Methods Mol Biol 2019; 2004:269-287. [PMID: 31147924 PMCID: PMC6667175 DOI: 10.1007/978-1-4939-9520-2_20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The Mre11-Rad50-Nbs1 (MRN) complex coordinates the repair of DNA double-strand breaks, replication fork restart, meiosis, class-switch recombination, and telomere maintenance. As such, MRN is an essential molecular machine that has homologs in all organisms of life, from bacteriophage to humans. In human cells, MRN is a >500 kDa multifunctional complex that encodes DNA binding, ATPase, and both endonuclease and exonuclease activities. MRN also forms larger assemblies and interacts with multiple DNA repair and replication factors. The enzymatic properties of MRN have been the subject of intense research for over 20 years, and more recently, single-molecule biophysics studies are beginning to probe its many biochemical activities. Here, we describe the methods used to overexpress, fluorescently label, and visualize MRN and its activities on single molecules of DNA.
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Affiliation(s)
- Logan R Myler
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA
| | - Michael M Soniat
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA
- Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, TX, USA
| | - Xiaoming Zhang
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA
- The Howard Hughes Medical Institute, The University of Texas at Austin, Austin, TX, USA
| | - Rajashree A Deshpande
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA
- The Howard Hughes Medical Institute, The University of Texas at Austin, Austin, TX, USA
| | - Tanya T Paull
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA
- The Howard Hughes Medical Institute, The University of Texas at Austin, Austin, TX, USA
| | - Ilya J Finkelstein
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA.
- Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, TX, USA.
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22
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Abstract
DNA double-strand breaks (DSBs) are a potentially lethal DNA lesions that disrupt both the physical and genetic continuity of the DNA duplex. Homologous recombination (HR) is a universally conserved genome maintenance pathway that initiates via nucleolytic processing of the broken DNA ends (resection). Eukaryotic DNA resection is catalyzed by the resectosome-a multicomponent molecular machine consisting of the nucleases DNA2 or Exonuclease 1 (EXO1), Bloom's helicase (BLM), the MRE11-RAD50-NBS1 (MRN) complex, and additional regulatory factors. Here, we describe methods for purification and single-molecule imaging and analysis of EXO1, DNA2, and BLM. We also describe how to adapt resection assays to the high-throughput single-molecule DNA curtain assay. By organizing hundreds of individual molecules on the surface of a microfluidic flowcell, DNA curtains visualize protein complexes with the required spatial and temporal resolution to resolve the molecular choreography during critical DNA-processing reactions.
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23
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Mi Y, Gurumurthy RK, Zadora PK, Meyer TF, Chumduri C. Chlamydia trachomatis Inhibits Homologous Recombination Repair of DNA Breaks by Interfering with PP2A Signaling. mBio 2018; 9:e01465-18. [PMID: 30401777 PMCID: PMC6222135 DOI: 10.1128/mbio.01465-18] [Citation(s) in RCA: 19] [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: 07/05/2018] [Accepted: 10/01/2018] [Indexed: 12/05/2022] Open
Abstract
Cervical and ovarian cancers exhibit characteristic mutational signatures that are reminiscent of mutational processes, including defective homologous recombination (HR) repair. How these mutational processes are initiated during carcinogenesis is largely unclear. Chlamydia trachomatis infections are epidemiologically associated with cervical and ovarian cancers. Previously, we showed that C. trachomatis induces DNA double-strand breaks (DSBs) but suppresses Ataxia-telangiectasia mutated (ATM) activation and cell cycle checkpoints. The mechanisms by which ATM regulation is modulated and its consequences for the repair pathway in C. trachomatis-infected cells remain unknown. Here, we found that Chlamydia bacteria interfere with the usual response of PP2A to DSBs. As a result, PP2A activity remains high, as the level of inhibitory phosphorylation at Y307 remains unchanged following C. trachomatis-induced DSBs. Protein-protein interaction analysis revealed that C. trachomatis facilitates persistent interactions of PP2A with ATM, thus suppressing ATM activation. This correlated with a remarkable lack of homologous recombination (HR) repair in C. trachomatis-infected cells. Chemical inhibition of PP2A activity in infected cells released ATM from PP2A, resulting in ATM phosphorylation. Activated ATM was then recruited to DSBs and initiated downstream signaling, including phosphorylation of MRE11 and NBS1 and checkpoint kinase 2 (Chk2)-mediated activation of the G2/M cell cycle checkpoint in C. trachomatis-infected cells. Further, PP2A inhibition led to the restoration of C. trachomatis-suppressed HR DNA repair function. Taking the data together, this study revealed that C. trachomatis modulates PP2A signaling to suppress ATM activation to prevent cell cycle arrest, thus contributing to a deficient high-fidelity HR pathway and a conducive environment for mutagenesis.IMPORTANCEChlamydia trachomatis induces DNA double-strand breaks in host cells but simultaneously inhibits proper DNA damage response and repair mechanisms. This may render host cells prone to loss of genetic integrity and transformation. Here we show that C. trachomatis prevents activation of the key DNA damage response mediator ATM by preventing the release from PP2A, leading to a complete absence of homologous recombination repair in host cells.
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Affiliation(s)
- Yang Mi
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
- Key Laboratory of H. pylori and Gastrointestinal Microecology of Henan Province, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China
| | | | - Piotr K Zadora
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Thomas F Meyer
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Cindrilla Chumduri
- Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
- Department of Hepatology and Gastroenterology, Charité University Medicine, Berlin, Germany
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24
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Chen MY, Hsu WC, Hsu SC, Yang YS, Chuang TH, Lin WJ, Tan TH, Su YW. PP4 deficiency leads to DNA replication stress that impairs immunoglobulin class switch efficiency. Cell Death Differ 2018; 26:1221-1234. [PMID: 30237510 PMCID: PMC6748143 DOI: 10.1038/s41418-018-0199-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 07/30/2018] [Accepted: 08/27/2018] [Indexed: 01/02/2023] Open
Abstract
The serine/threonine phosphatase PP4 has been implicated in DNA damage repair and cell cycle regulation through its dephosphorylation of specific substrates. We previously showed that PP4 is required for mouse B cell development, germinal center (GC) formation and immunoglobulin (Ig) class switch recombination (CSR). Here, we investigate the mechanisms underlying this requirement and demonstrate that murine PP4-deficient B lymphocytes have a defect in cell proliferation. Strikingly, the DNA damage response pathway that involves ATM/p53 and is linked to cell cycle arrest and impaired cell survival is strongly induced in these mutant B cells. In response to LPS + IL-4, stimuli that trigger IgG1 production, these PP4-deficient B cells show inefficient phosphorylation of ATR, leading to reduced retention of γH2AX-NBS1 complexes at sites of DNA damage, and compromised switching to IgG1. However, beyond the cell proliferation phase, conditional deletion of PP4 under the control of AID/cre completely restores normal IgG1 production in mutant B cell cultures. In vivo, co-deletion of PP4 and p53 by AID/cre partially rescues switching to IgG1 in B cells of mice immunized with TNP-KLH. Our findings establish that PP4 is indispensable for preventing DNA replication stress that could interfere with CSR, thereby promoting antibody switching during the humoral immune response.
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Affiliation(s)
- Ming-Yu Chen
- Immunology Research Center, National Health Research Institutes (NHRI), Zhunan, Miaoli County, Taiwan
| | - Wei-Chan Hsu
- Immunology Research Center, National Health Research Institutes (NHRI), Zhunan, Miaoli County, Taiwan
| | - Shu-Ching Hsu
- National Institute of Infectious Diseases and Vaccinology, NHRI, Zhunan, Miaoli County, Taiwan.,Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.,Department of Medical Research and Development, Chang Bing Show Chwan Memorial Hospital, Chang Hua, Taiwan
| | - Yu-Shao Yang
- National Institute of Infectious Diseases and Vaccinology, NHRI, Zhunan, Miaoli County, Taiwan
| | - Tsung-Hsien Chuang
- Immunology Research Center, National Health Research Institutes (NHRI), Zhunan, Miaoli County, Taiwan
| | - Wen-Jye Lin
- Immunology Research Center, National Health Research Institutes (NHRI), Zhunan, Miaoli County, Taiwan
| | - Tse-Hua Tan
- Immunology Research Center, National Health Research Institutes (NHRI), Zhunan, Miaoli County, Taiwan.,Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX, USA
| | - Yu-Wen Su
- Immunology Research Center, National Health Research Institutes (NHRI), Zhunan, Miaoli County, Taiwan.
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25
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Kannappan R, Mattapally S, Wagle PA, Zhang J. Transactivation domain of p53 regulates DNA repair and integrity in human iPS cells. Am J Physiol Heart Circ Physiol 2018; 315:H512-H521. [PMID: 29775409 PMCID: PMC6172637 DOI: 10.1152/ajpheart.00160.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 04/23/2018] [Accepted: 05/03/2018] [Indexed: 12/12/2022]
Abstract
The role of p53 transactivation domain (p53-TAD), a multifunctional and dynamic domain, on DNA repair and retaining DNA integrity in human induced pluripotent stem cells (hiPSCs) has never been studied. p53-TAD was knocked out in iPSCs using CRISPR/Cas9 and was confirmed by DNA sequencing. p53-TAD knockout (KO) cells were characterized by accelerated proliferation, decreased population doubling time, and unaltered Bcl-2, Bcl-2-binding component 3, insulin-like growth factor 1 receptor, and Bax and altered Mdm2, p21, and p53-induced death domain transcript expression. In p53-TAD KO cells, the p53-regulated DNA repair proteins xeroderma pigmentosum group A, DNA polymerase H, and DNA-binding protein 2 expression were found to be reduced compared with p53 wild-type cells. Exposure to a low dose of doxorubicin (Doxo) induced similar DNA damage and DNA damage response (DDR) as measured by RAD50 and MRE11 expression, checkpoint kinase 2 activation, and γH2A.X recruitment at DNA strand breaks in both cell groups, indicating that silence of p53-TAD does not affect the DDR mechanism upstream of p53. After removal of Doxo, p53 wild-type hiPSCs underwent DNA repair, corrected their damaged DNA, and restored DNA integrity. Conversely, p53-TAD KO hiPSCs did not undergo complete DNA repair and failed to restore DNA integrity. More importantly, continuous culture of p53-TAD KO hiPSCs underwent G2/M cell cycle arrest and expressed the cellular senescent marker p16INK4a. Our data clearly show that silence of the TAD of p53 did not affect DDR but affected the DNA repair process, implying the crucial role of p53-TAD in maintaining DNA integrity. Therefore, activating p53-TAD domain using small molecules may promote DNA repair and integrity of cells and prevent cellular senescence.
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Affiliation(s)
- Ramaswamy Kannappan
- Department of Biomedical Engineering, School of Medicine, School of Engineering, The University of Alabama at Birmingham , Birmingham, Alabama
| | - Saidulu Mattapally
- Department of Biomedical Engineering, School of Medicine, School of Engineering, The University of Alabama at Birmingham , Birmingham, Alabama
| | - Pooja A Wagle
- Department of Biomedical Engineering, School of Medicine, School of Engineering, The University of Alabama at Birmingham , Birmingham, Alabama
| | - Jianyi Zhang
- Department of Biomedical Engineering, School of Medicine, School of Engineering, The University of Alabama at Birmingham , Birmingham, Alabama
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26
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Smith LJ, Wright J, Clark G, Ul-Hasan T, Jin X, Fong A, Chandra M, St Martin T, Rubin H, Knowlton D, Ellsworth JL, Fong Y, Wong KK, Chatterjee S. Stem cell-derived clade F AAVs mediate high-efficiency homologous recombination-based genome editing. Proc Natl Acad Sci U S A 2018; 115:E7379-E7388. [PMID: 30018062 PMCID: PMC6077703 DOI: 10.1073/pnas.1802343115] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The precise correction of genetic mutations at the nucleotide level is an attractive permanent therapeutic strategy for human disease. However, despite significant progress, challenges to efficient and accurate genome editing persist. Here, we report a genome editing platform based upon a class of hematopoietic stem cell (HSC)-derived clade F adeno-associated virus (AAV), which does not require prior nuclease-mediated DNA breaks and functions exclusively through BRCA2-dependent homologous recombination. Genome editing is guided by complementary homology arms and is highly accurate and seamless, with no evidence of on-target mutations, including insertion/deletions or inclusion of AAV inverted terminal repeats. Efficient genome editing was demonstrated at different loci within the human genome, including a safe harbor locus, AAVS1, and the therapeutically relevant IL2RG gene, and at the murine Rosa26 locus. HSC-derived AAV vector (AAVHSC)-mediated genome editing was robust in primary human cells, including CD34+ cells, adult liver, hepatic endothelial cells, and myocytes. Importantly, high-efficiency gene editing was achieved in vivo upon a single i.v. injection of AAVHSC editing vectors in mice. Thus, clade F AAV-mediated genome editing represents a promising, highly efficient, precise, single-component approach that enables the development of therapeutic in vivo genome editing for the treatment of a multitude of human gene-based diseases.
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Affiliation(s)
- Laura J Smith
- Department of Surgery, Beckman Research Institute, City of Hope Medical Center, Duarte, CA 91010
| | | | - Gabriella Clark
- Department of Surgery, Beckman Research Institute, City of Hope Medical Center, Duarte, CA 91010
| | - Taihra Ul-Hasan
- Department of Surgery, Beckman Research Institute, City of Hope Medical Center, Duarte, CA 91010
| | - Xiangyang Jin
- Department of Surgery, Beckman Research Institute, City of Hope Medical Center, Duarte, CA 91010
| | - Abigail Fong
- Department of Surgery, Beckman Research Institute, City of Hope Medical Center, Duarte, CA 91010
| | - Manasa Chandra
- Department of Surgery, Beckman Research Institute, City of Hope Medical Center, Duarte, CA 91010
| | | | | | | | | | - Yuman Fong
- Department of Surgery, Beckman Research Institute, City of Hope Medical Center, Duarte, CA 91010
| | - Kamehameha K Wong
- Department of Hematology and Stem Cell Transplantation, City of Hope Medical Center, Duarte, CA 91010
| | - Saswati Chatterjee
- Department of Surgery, Beckman Research Institute, City of Hope Medical Center, Duarte, CA 91010;
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27
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Role of RNF20 in cancer development and progression - a comprehensive review. Biosci Rep 2018; 38:BSR20171287. [PMID: 29934362 PMCID: PMC6043722 DOI: 10.1042/bsr20171287] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 06/20/2018] [Accepted: 06/22/2018] [Indexed: 02/06/2023] Open
Abstract
Evolving strategies to counter cancer initiation and progression rely on the identification of novel therapeutic targets that exploit the aberrant genetic changes driving oncogenesis. Several chromatin associated enzymes have been shown to influence post-translational modification (PTM) in DNA, histones, and non-histone proteins. Any deregulation of this core group of enzymes often leads to cancer development. Ubiquitylation of histone H2B in mammalian cells was identified over three decades ago. An exciting really interesting new gene (RING) family of E3 ubiquitin ligases, known as RNF20 and RNF40, monoubiquitinates histone H2A at K119 or H2B at K120, is known to function in transcriptional elongation, DNA double-strand break (DSB) repair processes, maintenance of chromatin differentiation, and exerting tumor suppressor activity. RNF20 is somatically altered in breast, lung, prostate cancer, clear cell renal cell carcinoma (ccRCC), and mixed lineage leukemia, and its reduced expression is a key factor in initiating genome instability; and it also functions as one of the significant driving factors of oncogenesis. Loss of RNF20/40 and H2B monoubiquitination (H2Bub1) is found in several cancers and is linked to an aggressive phenotype, and is also an indicator of poor prognosis. In this review, we summarized the current knowledge of RNF20 in chronic inflammation-driven cancers, DNA DSBs, and apoptosis, and its impact on chromatin structure beyond the single nucleosome level.
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28
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Raposo AE, Piller SC. Protein arginine methylation: an emerging regulator of the cell cycle. Cell Div 2018; 13:3. [PMID: 29568320 PMCID: PMC5859524 DOI: 10.1186/s13008-018-0036-2] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 03/13/2018] [Indexed: 12/19/2022] Open
Abstract
Protein arginine methylation is a common post-translational modification where a methyl group is added onto arginine residues of a protein to alter detection by its binding partners or regulate its activity. It is known to be involved in many biological processes, such as regulation of signal transduction, transcription, facilitation of protein–protein interactions, RNA splicing and transport. The enzymes responsible for arginine methylation, protein arginine methyltransferases (PRMTs), have been shown to methylate or associate with important regulatory proteins of the cell cycle and DNA damage repair pathways, such as cyclin D1, p53, p21 and the retinoblastoma protein. Overexpression of PRMTs resulting in aberrant methylation patterns in cancers often correlates with poor recovery prognosis. This indicates that protein arginine methylation is also an important regulator of the cell cycle, and consequently a target for cancer regulation. The effect of protein arginine methylation on the cell cycle and how this emerging key player of cell cycle regulation may be used in therapeutic strategies for cancer are the focus of this review.
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Affiliation(s)
- Anita E Raposo
- School of Science and Health, Western Sydney University, Penrith, NSW 2751 Australia
| | - Sabine C Piller
- School of Science and Health, Western Sydney University, Penrith, NSW 2751 Australia
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29
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Li JSZ, Denchi EL. How stem cells keep telomeres in check. Differentiation 2018; 100:21-25. [PMID: 29413749 DOI: 10.1016/j.diff.2018.01.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 01/19/2018] [Accepted: 01/23/2018] [Indexed: 10/18/2022]
Abstract
In multicellular organisms, regulation of telomere length in pluripotent stem cells is critical to ensure organism development and survival. Telomeres consist of repetitive DNA that are progressively lost with each cellular division. When telomeres become critically short, they activate a DNA damage response that results in cell cycle arrest. To counteract telomere attrition, pluripotent stem cells are equipped with telomere elongation mechanisms that ensure prolonged proliferation capacity and self-renewal capacity. Excessive telomere elongation can also be deleterious and is counteracted by a rapid telomere deletion mechanism termed telomere trimming. While the consequences of critically short telomeres are well established, we are only beginning to understand the mechanisms that counteract excessive telomere elongation. The balance between telomere elongation and shortening determine the telomere length set point in pluripotent stem cells and ensures sustained proliferative potential without causing chromosome instability.
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Affiliation(s)
- Julia Su Zhou Li
- Department of Molecular Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Eros Lazzerini Denchi
- Department of Molecular Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
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30
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Abstract
Accurate repair of DNA double-strand breaks (DSBs) is carried out by homologous recombination. In order to repair DNA breaks by the recombination pathway, the 5'-terminated DNA strand at DSB sites must be first nucleolytically processed to produce 3'-overhang. The process is termed DNA end resection and involves the interplay of several nuclease complexes. DNA end resection commits DSB repair to the recombination pathway including a process termed single-strand annealing, as resected DNA ends are generally nonligatable by the competing nonhomologous end-joining machinery. Biochemical reconstitution experiments provided invaluable mechanistic insights into the DNA end resection pathways. In this chapter, we describe preparation procedures of key proteins involved in DNA end resection in human cells, including the MRE11-RAD50-NBS1 complex, phosphorylated variant of CtIP, the DNA2 nuclease-helicase with its helicase partners Bloom (BLM) or Werner (WRN), as well as the single-stranded DNA-binding protein replication protein A. The availability of recombinant DNA end resection factors will help to further elucidate resection mechanisms and regulatory processes that may involve novel protein partners and posttranslational modifications.
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Affiliation(s)
- Roopesh Anand
- Institute for Research in Biomedicine, Università della Svizzera italiana, Bellinzona, Switzerland
| | - Cosimo Pinto
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Petr Cejka
- Institute for Research in Biomedicine, Università della Svizzera italiana, Bellinzona, Switzerland; Institute of Biochemistry, Swiss Federal Institute of Technology, Zurich, Switzerland.
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31
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Zhou H, Kawamura K, Yanagihara H, Kobayashi J, Zhang-Akiyama QM. NBS1 is regulated by two kind of mechanisms: ATM-dependent complex formation with MRE11 and RAD50, and cell cycle-dependent degradation of protein. JOURNAL OF RADIATION RESEARCH 2017; 58:487-494. [PMID: 28369484 PMCID: PMC5570008 DOI: 10.1093/jrr/rrx014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 01/27/2017] [Indexed: 05/03/2023]
Abstract
Nijmegen breakage syndrome (NBS), a condition similar to Ataxia-Telangiectasia (A-T), is a radiation-hypersensitive genetic disorder showing chromosomal instability, radio-resistant DNA synthesis, immunodeficiency, and predisposition to malignances. The product of the responsible gene, NBS1, forms a complex with MRE11 and RAD50 (MRN complex). The MRN complex is necessary for the DNA damage-induced activation of ATM. However, the regulation of MRN complex formation is still unclear. Here, we investigated the regulatory mechanisms of MRN complex formation. We used an immunoprecipitation assay to determine whether levels of the MRN complex were increased by radiation-induced DNA damage and found that the levels of these proteins and their mRNAs did not increase. ATM-dependent phosphorylation of NBS1 contributed to the DNA damage-induced MRN complex formation. However, pre-treatment of cells with an ATM-specific inhibitor did not affect homologous recombination (HR) and non-homologous end-joining (NHEJ) repair. G0 phase cells, decreasing NBS1 and HR activity but not NHEJ, gained HR-related chromatin association of RAD51 by overexpression of NBS1, suggesting that the amount of NBS1 may be important for repressing accidental activation of HR. These evidences suggest that NBS1 is regulated by two kind of mechanisms: complex formation dependent on ATM, and protein degradation mediated by an unknown MG132-resistant pathway. Such regulation of NBS1 may contribute to cellular responses to double-strand breaks.
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Affiliation(s)
- Hui Zhou
- Laboratory of Stress Response Biology, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8501, Japan
- Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Yoshidakonoecho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Kasumi Kawamura
- Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Yoshidakonoecho, Sakyo-ku, Kyoto 606-8501, Japan
- Department of Interdisciplinary Environment, Graduate School of Human and Environmental Sciences, Kyoto University, Yoshidanihonmatsucho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hiromi Yanagihara
- Department of Genetics and Cell Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan
| | - Junya Kobayashi
- Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Yoshidakonoecho, Sakyo-ku, Kyoto 606-8501, Japan
- Department of Interdisciplinary Environment, Graduate School of Human and Environmental Sciences, Kyoto University, Yoshidanihonmatsucho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Qiu-Mei Zhang-Akiyama
- Laboratory of Stress Response Biology, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8501, Japan
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32
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Gadducci A, Guerrieri ME. PARP inhibitors alone and in combination with other biological agents in homologous recombination deficient epithelial ovarian cancer: From the basic research to the clinic. Crit Rev Oncol Hematol 2017; 114:153-165. [PMID: 28477743 DOI: 10.1016/j.critrevonc.2017.04.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 03/15/2017] [Accepted: 04/11/2017] [Indexed: 12/21/2022] Open
Abstract
Hereditary epithelial ovarian cancer [EOC] in germline BRCA mutation (gBRCAm) carriers has a distinct clinical behavior characterized by younger age, high- grade serous histology, advanced stage, visceral distribution of disease, high response to platinum and other non-platinum agents and better clinical outcome. Sporadic EOC with homologous recombination deficiency [HDR] but no gBRCAm has the same biological and clinical behavior as EOC in gBRCAm carriers ("BRCAness"phenotype). Biomarkers are in development to enable an accurate definition of molecular features of BRCAness phenotype, and trials are warranted to determine whether such HDR signature will predict sensitivity to PARP inhibitors in sporadic EOC. Moreover, the link between PARP inhibition and angiogenesis suppression, the immunologic properties of EOC in gBRCAm carriers, the HRD induced by PI3K inhibition in EOC cells in vitro strongly support novel clinical trials testing the combination of PARP inhibitors with other biological agents.
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Affiliation(s)
- Angiolo Gadducci
- Department of Clinical and Experimental Medicine, Division of Gynecology and Obstetrics, University of Pisa, Italy.
| | - Maria Elena Guerrieri
- Department of Clinical and Experimental Medicine, Division of Gynecology and Obstetrics, University of Pisa, Italy
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33
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DNA damage repair in breast cancer and its therapeutic implications. Pathology 2016; 49:156-165. [PMID: 28034453 DOI: 10.1016/j.pathol.2016.11.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 10/06/2016] [Accepted: 11/02/2016] [Indexed: 11/23/2022]
Abstract
The DNA damage response (DDR) involves the activation of numerous cellular activities that repair DNA lesions and maintain genomic integrity, and is critical in preventing tumorigenesis. Inherited or acquired mutations in specific genes involved in the DNA damage response, for example the breast cancer susceptibility genes 1/2 (BRCA1/2), phosphatase and tensin homolog (PTEN) and P53 are associated with various subtypes of breast cancer. Such changes can render breast cancer cells particularly sensitive to specific DNA damage response inhibitors, for example BRCA1/2 germline mutated cells are sensitive to poly (ADP-ribose) polymerase (PARP) inhibitors. The aims of this review are to discuss specific DNA damage response defects in breast cancer and to present the current stage of development of various DDR inhibitors (namely PARP, ATM/ATR, DNA-PK, PARG, RECQL5, FEN1 and APE1) for breast cancer mono- and combination therapy.
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34
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Lokhande S, Patra BN, Ray A. A link between chromatin condensation mechanisms and Huntington's disease: connecting the dots. MOLECULAR BIOSYSTEMS 2016; 12:3515-3529. [PMID: 27714015 DOI: 10.1039/c6mb00598e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Huntington's disease is a rare neurodegenerative disorder whose complex pathophysiology exhibits system-wide changes in the body, with striking and debilitating clinical features targeting the central nervous system. Among the various molecular functions affected in this disease, mitochondrial dysfunction and transcriptional dysregulation are some of the most studied aspects of this disease. However, there is evidence of the involvement of a mutant Huntingtin protein in the processes of DNA damage, chromosome condensation and DNA repair. This review attempts to briefly recapitulate the clinical features, model systems used to study the disease, major molecular processes affected, and, more importantly, examines recent evidence for the involvement of the mutant Huntingtin protein in the processes regulating chromosome condensation, leading to DNA damage response and neuronal death.
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Affiliation(s)
- Sonali Lokhande
- Keck Graduate Institute of Applied Life Sciences, Claremont, CA 91711, USA.
| | - Biranchi N Patra
- Keck Graduate Institute of Applied Life Sciences, Claremont, CA 91711, USA.
| | - Animesh Ray
- Keck Graduate Institute of Applied Life Sciences, Claremont, CA 91711, USA.
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35
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Hartlerode AJ, Willis NA, Rajendran A, Manis JP, Scully R. Complex Breakpoints and Template Switching Associated with Non-canonical Termination of Homologous Recombination in Mammalian Cells. PLoS Genet 2016; 12:e1006410. [PMID: 27832076 PMCID: PMC5104497 DOI: 10.1371/journal.pgen.1006410] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 10/07/2016] [Indexed: 12/11/2022] Open
Abstract
A proportion of homologous recombination (HR) events in mammalian cells resolve by "long tract" gene conversion, reflecting copying of several kilobases from the donor sister chromatid prior to termination. Cells lacking the major hereditary breast/ovarian cancer predisposition genes, BRCA1 or BRCA2, or certain other HR-defective cells, reveal a bias in favor of long tract gene conversion, suggesting that this aberrant HR outcome might be connected with genomic instability. If termination of gene conversion occurs in regions lacking homology with the second end of the break, the normal mechanism of HR termination by annealing (i.e., homologous pairing) is not available and termination must occur by as yet poorly defined non-canonical mechanisms. Here we use a previously described HR reporter to analyze mechanisms of non-canonical termination of long tract gene conversion in mammalian cells. We find that non-canonical HR termination can occur in the absence of the classical non-homologous end joining gene XRCC4. We observe obligatory use of microhomology (MH)-mediated end joining and/or nucleotide addition during rejoining with the second end of the break. Notably, non-canonical HR termination is associated with complex breakpoints. We identify roles for homology-mediated template switching and, potentially, MH-mediated template switching/microhomology-mediated break-induced replication, in the formation of complex breakpoints at sites of non-canonical HR termination. This work identifies non-canonical HR termination as a potential contributor to genomic instability and to the formation of complex breakpoints in cancer.
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Affiliation(s)
- Andrea J. Hartlerode
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Nicholas A. Willis
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Anbazhagan Rajendran
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America
| | - John P. Manis
- Department of Pathology, Boston Children’s Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Ralph Scully
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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36
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Myler LR, Finkelstein IJ. Eukaryotic resectosomes: A single-molecule perspective. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 127:119-129. [PMID: 27498169 DOI: 10.1016/j.pbiomolbio.2016.08.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 08/02/2016] [Indexed: 12/13/2022]
Abstract
DNA double-strand breaks (DSBs) disrupt the physical and genetic continuity of the genome. If unrepaired, DSBs can lead to cellular dysfunction and malignant transformation. Homologous recombination (HR) is a universally conserved DSB repair mechanism that employs the information in a sister chromatid to catalyze error-free DSB repair. To initiate HR, cells assemble the resectosome: a multi-protein complex composed of helicases, nucleases, and regulatory proteins. The resectosome nucleolytically degrades (resects) the free DNA ends for downstream homologous recombination. Several decades of intense research have identified the core resectosome components in eukaryotes, archaea, and bacteria. More recently, these proteins have been characterized via single-molecule approaches. Here, we focus on recent single-molecule studies that have begun to unravel how nucleases, helicases, processivity factors, and other regulatory proteins dictate the extent and efficiency of DNA resection in eukaryotic cells. We conclude with a discussion of outstanding questions that can be addressed via single-molecule approaches.
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Affiliation(s)
- Logan R Myler
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX, 78712, USA; Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Ilya J Finkelstein
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX, 78712, USA; Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, TX, 78712, USA.
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37
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Komatsu K. NBS1 and multiple regulations of DNA damage response. JOURNAL OF RADIATION RESEARCH 2016; 57 Suppl 1:i11-i17. [PMID: 27068998 PMCID: PMC4990113 DOI: 10.1093/jrr/rrw031] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 02/09/2016] [Accepted: 02/13/2016] [Indexed: 05/19/2023]
Abstract
DNA damage response is finely tuned, with several pathways including those for DNA repair, chromatin remodeling and cell cycle checkpoint, although most studies to date have focused on single pathways. Genetic diseases characterized by genome instability have provided novel insights into the underlying mechanisms of DNA damage response. NBS1, a protein responsible for the radiation-sensitive autosomal recessive disorder Nijmegen breakage syndrome, is one of the first factors to accumulate at sites of DNA double-strand breaks (DSBs). NBS1 binds to at least five key proteins, including ATM, RPA, MRE11, RAD18 and RNF20, in the conserved regions within a limited span of the C terminus, functioning in the regulation of chromatin remodeling, cell cycle checkpoint and DNA repair in response to DSBs. In this article, we reviewed the functions of these binding proteins and their comprehensive association with NBS1.
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Affiliation(s)
- Kenshi Komatsu
- Division of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Yoshida-Konoecho, Sakyo-Ku, Kyoto 606-8501, Japan
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Takeda S, Hoa NN, Sasanuma H. The role of the Mre11-Rad50-Nbs1 complex in double-strand break repair-facts and myths. JOURNAL OF RADIATION RESEARCH 2016; 57 Suppl 1:i25-i32. [PMID: 27311583 PMCID: PMC4990115 DOI: 10.1093/jrr/rrw034] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 02/16/2016] [Accepted: 02/23/2016] [Indexed: 06/06/2023]
Abstract
Homologous recombination (HR) initiates double-strand break (DSB) repair by digesting 5'-termini at DSBs, the biochemical reaction called DSB resection, during which DSBs are processed by nucleases to generate 3' single-strand DNA. Rad51 recombinase polymerizes along resected DNA, and the resulting Rad51-DNA complex undergoes homology search. Although DSB resection by the Mre11 nuclease plays a critical role in HR in Saccharomyces cerevisiae, it remains elusive whether DSB resection by Mre11 significantly contributes to HR-dependent DSB repair in mammalian cells. Depletion of Mre11 decreases the efficiency of DSB resection only by 2- to 3-fold in mammalian cells. We show that although Mre11 is required for efficient HR-dependent repair of ionizing-radiation-induced DSBs, Mre11 is largely dispensable for DSB resection in both chicken DT40 and human TK6 B cell lines. Moreover, a 2- to 3-fold decrease in DSB resection has virtually no impact on the efficiency of HR. Thus, although a large number of researchers have reported the vital role of Mre11-mediated DSB resection in HR, the role may not explain the very severe defect in HR in Mre11-deficient cells, including their lethality. We here show experimental evidence for the additional roles of Mre11 in (i) elimination of chemical adducts from DSB ends for subsequent DSB repair, and (ii) maintaining HR intermediates for their proper resolution.
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Affiliation(s)
- Shunichi Takeda
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501, Japan
| | - Nguyen Ngoc Hoa
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hiroyuki Sasanuma
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501, Japan
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Liu T, Huang J. DNA End Resection: Facts and Mechanisms. GENOMICS PROTEOMICS & BIOINFORMATICS 2016; 14:126-130. [PMID: 27240470 PMCID: PMC4936662 DOI: 10.1016/j.gpb.2016.05.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 05/04/2016] [Accepted: 05/05/2016] [Indexed: 01/05/2023]
Abstract
DNA double-strand breaks (DSBs), which arise following exposure to a number of endogenous and exogenous agents, can be repaired by either the homologous recombination (HR) or non-homologous end-joining (NHEJ) pathways in eukaryotic cells. A vital step in HR repair is DNA end resection, which generates a long 3′ single-stranded DNA (ssDNA) tail that can invade the homologous DNA strand. The generation of 3′ ssDNA is not only essential for HR repair, but also promotes activation of the ataxia telangiectasia and Rad3-related protein (ATR). Multiple factors, including the MRN/X complex, C-terminal-binding protein interacting protein (CtIP)/Sae2, exonuclease 1 (EXO1), Bloom syndrome protein (BLM)/Sgs1, DNA2 nuclease/helicase, and several chromatin remodelers, cooperate to complete the process of end resection. Here we review the basic machinery involved in DNA end resection in eukaryotic cells.
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Affiliation(s)
- Ting Liu
- Department of Cell Biology and Program in Molecular Cell Biology, Zhejiang University School of Medicine, Hangzhou 310058, China.
| | - Jun Huang
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, China.
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40
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Lanning DK, Knight KL. Diversification of the Primary Antibody Repertoire by AID-Mediated Gene Conversion. Results Probl Cell Differ 2016; 57:279-93. [PMID: 26537386 DOI: 10.1007/978-3-319-20819-0_12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Gene conversion, mediated by activation-induced cytidine deaminase (AID), has been found to contribute to generation of the primary antibody repertoire in several vertebrate species. Generation of the primary antibody repertoire by gene conversion of immunoglobulin (Ig) genes occurs primarily in gut-associated lymphoid tissues (GALT) and is best described in chicken and rabbit. Here, we discuss current knowledge of the mechanism of gene conversion as well as the contribution of the microbiota in promoting gene conversion of Ig genes. Finally, we propose that the antibody diversification strategy used in GALT species, such as chicken and rabbit, is conserved in a subset of human and mouse B cells.
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Affiliation(s)
- Dennis K Lanning
- Department of Microbiology and Immunology, Loyola University Chicago, 2160 S. First Avenue, Maywood, IL, 60153, USA
| | - Katherine L Knight
- Department of Microbiology and Immunology, Loyola University Chicago, 2160 S. First Avenue, Maywood, IL, 60153, USA.
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41
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Wu Y, Lee SH, Williamson EA, Reinert BL, Cho JH, Xia F, Jaiswal AS, Srinivasan G, Patel B, Brantley A, Zhou D, Shao L, Pathak R, Hauer-Jensen M, Singh S, Kong K, Wu X, Kim HS, Beissbarth T, Gaedcke J, Burma S, Nickoloff JA, Hromas RA. EEPD1 Rescues Stressed Replication Forks and Maintains Genome Stability by Promoting End Resection and Homologous Recombination Repair. PLoS Genet 2015; 11:e1005675. [PMID: 26684013 PMCID: PMC4684289 DOI: 10.1371/journal.pgen.1005675] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 10/26/2015] [Indexed: 12/13/2022] Open
Abstract
Replication fork stalling and collapse is a major source of genome instability leading to neoplastic transformation or cell death. Such stressed replication forks can be conservatively repaired and restarted using homologous recombination (HR) or non-conservatively repaired using micro-homology mediated end joining (MMEJ). HR repair of stressed forks is initiated by 5’ end resection near the fork junction, which permits 3’ single strand invasion of a homologous template for fork restart. This 5’ end resection also prevents classical non-homologous end-joining (cNHEJ), a competing pathway for DNA double-strand break (DSB) repair. Unopposed NHEJ can cause genome instability during replication stress by abnormally fusing free double strand ends that occur as unstable replication fork repair intermediates. We show here that the previously uncharacterized Exonuclease/Endonuclease/Phosphatase Domain-1 (EEPD1) protein is required for initiating repair and restart of stalled forks. EEPD1 is recruited to stalled forks, enhances 5’ DNA end resection, and promotes restart of stalled forks. Interestingly, EEPD1 directs DSB repair away from cNHEJ, and also away from MMEJ, which requires limited end resection for initiation. EEPD1 is also required for proper ATR and CHK1 phosphorylation, and formation of gamma-H2AX, RAD51 and phospho-RPA32 foci. Consistent with a direct role in stalled replication fork cleavage, EEPD1 is a 5’ overhang nuclease in an obligate complex with the end resection nuclease Exo1 and BLM. EEPD1 depletion causes nuclear and cytogenetic defects, which are made worse by replication stress. Depleting 53BP1, which slows cNHEJ, fully rescues the nuclear and cytogenetic abnormalities seen with EEPD1 depletion. These data demonstrate that genome stability during replication stress is maintained by EEPD1, which initiates HR and inhibits cNHEJ and MMEJ. The cell itself damages its own DNA throughout the cell cycle as a result of oxidative metabolism, and this damage creates barriers for replication fork progression. Thus, DNA replication is not a smooth and continuous process, but rather one of stalls and restarts. Therefore, proper replication fork restart is crucial to maintain the integrity of the cell’s genome, and preventing its own death or immortalization. To restart after stalling, the replication fork subverts a DNA repair pathway termed homologous recombination. Using any other pathway for fork repair will result in an unstable genome. How the homologous recombination repair pathway is initiated at the replication fork is not well defined. In this study we demonstrate the previously uncharacterized EEPD1 protein is a novel gatekeeper for the initiation of this fork repair pathway. EEPD1 promotes 5’ end resection, the initial step of homologous recombination, which also prevents alternative fork repair pathways that lead to unstable chromosomes. Thus, EEPD1 protects the integrity of the cell genome by promoting the safe homologous recombination fork repair pathway.
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Affiliation(s)
- Yuehan Wu
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, Florida, United States of America
| | - Suk-Hee Lee
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Elizabeth A. Williamson
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, Florida, United States of America
| | - Brian L. Reinert
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, Florida, United States of America
| | - Ju Hwan Cho
- Department of Radiation Oncology, Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio, United States of America
| | - Fen Xia
- Department of Radiation Oncology, Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio, United States of America
| | - Aruna Shanker Jaiswal
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, Florida, United States of America
| | - Gayathri Srinivasan
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, Florida, United States of America
| | - Bhavita Patel
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, Florida, United States of America
| | - Alexis Brantley
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, Florida, United States of America
| | - Daohong Zhou
- Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Lijian Shao
- Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Rupak Pathak
- Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Martin Hauer-Jensen
- Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Sudha Singh
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, Florida, United States of America
| | - Kimi Kong
- Department of Craniofacial Regeneration, College of Dental Medicine, Columbia University, New York, New York, United States of America
| | - Xaiohua Wu
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California, United States of America
| | - Hyun-Suk Kim
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America
| | - Timothy Beissbarth
- Department of Medical Statistics, and General, Visceral, and Pediatric Surgery, University Medical Center Göttingen, Göttingen, Germany
| | - Jochen Gaedcke
- Department of Medical Statistics, and General, Visceral, and Pediatric Surgery, University Medical Center Göttingen, Göttingen, Germany
| | - Sandeep Burma
- Department of Radiation Oncology, University of Texas Southwestern, Dallas, Texas, United States of America
| | - Jac A. Nickoloff
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, Colorado, United States of America
- * E-mail: (JAN); (RAH)
| | - Robert A. Hromas
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, Florida, United States of America
- * E-mail: (JAN); (RAH)
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42
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Acetylation of Histone H2AX at Lys 5 by the TIP60 Histone Acetyltransferase Complex Is Essential for the Dynamic Binding of NBS1 to Damaged Chromatin. Mol Cell Biol 2015; 35:4147-57. [PMID: 26438602 DOI: 10.1128/mcb.00757-15] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 10/02/2015] [Indexed: 11/20/2022] Open
Abstract
The association and dissociation of DNA damage response (DDR) factors with damaged chromatin occurs dynamically, which is crucial for the activation of DDR signaling in a spatiotemporal manner. We previously showed that the TIP60 histone acetyltransferase complex acetylates histone H2AX, to facilitate H2AX exchange at sites of DNA damage. However, it remained unclear how the acetylation of histone H2AX by TIP60 is related to the DDR signaling. We found that the acetylation but not the phosphorylation of H2AX is essential for the turnover of NBS1 on damaged chromatin. The loss of H2AX acetylation at Lys 5 by TIP60 in cells disturbed the accumulation of NBS1 at sites of DNA damage. Although the phosphorylation of H2AX is also reportedly required for the retention of NBS1 at damage sites, our data indicated that the acetylation-dependent NBS1 turnover by TIP60 on damaged chromatin restricts the dispersal of NBS1 foci from the sites of DNA damage. These findings indicate the importance of the acetylation-dependent dynamic binding of NBS1 to damaged chromatin, created by histone H2AX exchange, for the proper accumulation of NBS1 at DNA damage sites.
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43
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Saito Y, Komatsu K. Functional Role of NBS1 in Radiation Damage Response and Translesion DNA Synthesis. Biomolecules 2015; 5:1990-2002. [PMID: 26308066 PMCID: PMC4598784 DOI: 10.3390/biom5031990] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/11/2015] [Accepted: 08/13/2015] [Indexed: 12/15/2022] Open
Abstract
Nijmegen breakage syndrome (NBS) is a recessive genetic disorder characterized by increased sensitivity to ionizing radiation (IR) and a high frequency of malignancies. NBS1, a product of the mutated gene in NBS, contains several protein interaction domains in the N-terminus and C-terminus. The C-terminus of NBS1 is essential for interactions with MRE11, a homologous recombination repair nuclease, and ATM, a key player in signal transduction after the generation of DNA double-strand breaks (DSBs), which is induced by IR. Moreover, NBS1 regulates chromatin remodeling during DSB repair by histone H2B ubiquitination through binding to RNF20 at the C-terminus. Thus, NBS1 is considered as the first protein to be recruited to DSB sites, wherein it acts as a sensor or mediator of DSB damage responses. In addition to DSB response, we showed that NBS1 initiates Polη-dependent translesion DNA synthesis by recruiting RAD18 through its binding at the NBS1 C-terminus after UV exposure, and it also functions after the generation of interstrand crosslink DNA damage. Thus, NBS1 has multifunctional roles in response to DNA damage from a variety of genotoxic agents, including IR.
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Affiliation(s)
- Yuichiro Saito
- Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501, Japan.
| | - Kenshi Komatsu
- Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Yoshida Konoe, Sakyo-ku, Kyoto 606-8501, Japan.
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44
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He MD, Zhang FH, Wang HL, Wang HP, Zhu ZY, Sun YH. Efficient ligase 3-dependent microhomology-mediated end joining repair of DNA double-strand breaks in zebrafish embryos. Mutat Res 2015; 780:86-96. [PMID: 26318124 DOI: 10.1016/j.mrfmmm.2015.08.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 07/21/2015] [Accepted: 08/14/2015] [Indexed: 02/07/2023]
Abstract
DNA double-strand break (DSB) repair is of considerable importance for genomic integrity. Homologous recombination (HR) and non-homologous end joining (NHEJ) are considered as two major mechanistically distinct pathways involved in repairing DSBs. In recent years, another DSB repair pathway, namely, microhomology-mediated end joining (MMEJ), has received increasing attention. MMEJ is generally believed to utilize an alternative mechanism to repair DSBs when NHEJ and other mechanisms fail. In this study, we utilized zebrafish as an in vivo model to study DSB repair and demonstrated that efficient MMEJ repair occurred in the zebrafish genome when DSBs were induced using TALEN (transcription activator-like effector nuclease) or CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 technologies. The wide existence of MMEJ repair events in zebrafish embryos was further demonstrated via the injection of several in vitro-designed exogenous MMEJ reporters. Interestingly, the inhibition of endogenous ligase 4 activity significantly increased MMEJ frequency, and the inhibition of ligase 3 activity severely decreased MMEJ activity. These results suggest that MMEJ in zebrafish is dependent on ligase 3 but independent of ligase 4. This study will enhance our understanding of the mechanisms of MMEJ in vivo and facilitate inducing desirable mutations via DSB-induced repair.
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Affiliation(s)
- Mu-Dan He
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Feng-Hua Zhang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Hua-Lin Wang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Hou-Peng Wang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Zuo-Yan Zhu
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Yong-Hua Sun
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
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45
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Oei AL, Vriend LEM, Crezee J, Franken NAP, Krawczyk PM. Effects of hyperthermia on DNA repair pathways: one treatment to inhibit them all. Radiat Oncol 2015; 10:165. [PMID: 26245485 PMCID: PMC4554295 DOI: 10.1186/s13014-015-0462-0] [Citation(s) in RCA: 186] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 07/13/2015] [Indexed: 12/03/2022] Open
Abstract
The currently available arsenal of anticancer modalities includes many DNA damaging agents that can kill malignant cells. However, efficient DNA repair mechanisms protect both healthy and cancer cells against the effects of treatment and contribute to the development of drug resistance. Therefore, anti-cancer treatments based on inflicting DNA damage can benefit from inhibition of DNA repair. Hyperthermia – treatment at elevated temperature – considerably affects DNA repair, among other cellular processes, and can thus sensitize (cancer) cells to DNA damaging agents. This effect has been known and clinically applied for many decades, but how heat inhibits DNA repair and which pathways are targeted has not been fully elucidated. In this review we attempt to summarize the known effects of hyperthermia on DNA repair pathways relevant in clinical treatment of cancer. Furthermore, we outline the relationships between the effects of heat on DNA repair and sensitization of cells to various DNA damaging agents.
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Affiliation(s)
- Arlene L Oei
- Laboratory for Experimental Oncology and Radiobiology (LEXOR), Center for Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands. .,Department of Radiotherapy, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands.
| | - Lianne E M Vriend
- Van Leeuwenhoek Centre for Advanced Microscopy (LCAM)-AMC, Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands.
| | - Johannes Crezee
- Department of Radiotherapy, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands.
| | - Nicolaas A P Franken
- Laboratory for Experimental Oncology and Radiobiology (LEXOR), Center for Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands. .,Department of Radiotherapy, Academic Medical Center, University of Amsterdam, 1105 AZ, Amsterdam, The Netherlands.
| | - Przemek M Krawczyk
- Van Leeuwenhoek Centre for Advanced Microscopy (LCAM)-AMC, Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands.
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46
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Kato A, Komatsu K. RNF20-SNF2H Pathway of Chromatin Relaxation in DNA Double-Strand Break Repair. Genes (Basel) 2015; 6:592-606. [PMID: 26184323 PMCID: PMC4584319 DOI: 10.3390/genes6030592] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Revised: 07/07/2015] [Accepted: 07/09/2015] [Indexed: 01/25/2023] Open
Abstract
Rapid progress in the study on the association of histone modifications with chromatin remodeling factors has broadened our understanding of chromatin dynamics in DNA transactions. In DNA double-strand break (DSB) repair, the well-known mark of histones is the phosphorylation of the H2A variant, H2AX, which has been used as a surrogate marker of DSBs. The ubiquitylation of histone H2B by RNF20 E3 ligase was recently found to be a DNA damage-induced histone modification. This modification is required for DSB repair and regulated by a distinctive pathway from that of histone H2AX phosphorylation. Moreover, the connection between H2B ubiquitylation and the chromatin remodeling activity of SNF2H has been elucidated. In this review, we summarize the current knowledge of RNF20-mediated processes and the molecular link to H2AX-mediated processes during DSB repair.
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Affiliation(s)
- Akihiro Kato
- Division of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Yoshida-konoecho, Sakyo-ku, Kyoto 606-8501, Japan.
| | - Kenshi Komatsu
- Division of Genome Repair Dynamics, Radiation Biology Center, Kyoto University, Yoshida-konoecho, Sakyo-ku, Kyoto 606-8501, Japan.
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47
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Dillon LW, Kumar P, Shibata Y, Wang YH, Willcox S, Griffith JD, Pommier Y, Takeda S, Dutta A. Production of Extrachromosomal MicroDNAs Is Linked to Mismatch Repair Pathways and Transcriptional Activity. Cell Rep 2015; 11:1749-59. [PMID: 26051933 DOI: 10.1016/j.celrep.2015.05.020] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 04/20/2015] [Accepted: 05/11/2015] [Indexed: 12/15/2022] Open
Abstract
MicroDNAs are <400-base extrachromosomal circles found in mammalian cells. Tens of thousands of microDNAs have been found in all tissue types, including sperm. MicroDNAs arise preferentially from areas with high gene density, GC content, and exon density from promoters with activating chromatin modifications and in sperm from the 5'-UTR of full-length LINE-1 elements, but are depleted from lamin-associated heterochromatin. Analysis of microDNAs from a set of human cancer cell lines revealed lineage-specific patterns of microDNA origins. A survey of microDNAs from chicken cells defective in various DNA repair proteins reveals that homologous recombination and non-homologous end joining repair pathways are not required for microDNA production. Deletion of the MSH3 DNA mismatch repair protein results in a significant decrease in microDNA abundance, specifically from non-CpG genomic regions. Thus, microDNAs arise as part of normal cellular physiology—either from DNA breaks associated with RNA metabolism or from replication slippage followed by mismatch repair.
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Affiliation(s)
- Laura W Dillon
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Pankaj Kumar
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Yoshiyuki Shibata
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Yuh-Hwa Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Smaranda Willcox
- Lineberger Comprehensive Cancer Center, Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Jack D Griffith
- Lineberger Comprehensive Cancer Center, Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Yves Pommier
- Laboratory of Molecular Pharmacology and Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA
| | - Shunichi Takeda
- CREST Research Project, Japan Science and Technology Corporation, Radiation Genetics, Faculty of Medicine, Kyoto University, Konoe Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Anindya Dutta
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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48
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Saito Y, Zhou H, Kobayashi J. Chromatin modification and NBS1: their relationship in DNA double-strand break repair. Genes Genet Syst 2015; 90:195-208. [DOI: 10.1266/ggs.15-00010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Affiliation(s)
- Yuichiro Saito
- Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University
| | - Hui Zhou
- Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University
| | - Junya Kobayashi
- Department of Genome Repair Dynamics, Radiation Biology Center, Kyoto University
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49
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Hopfner KP. ATP puts the brake on DNA double-strand break repair: a new study shows that ATP switches the Mre11-Rad50-Nbs1 repair factor between signaling and processing of DNA ends. Bioessays 2014; 36:1170-8. [PMID: 25213441 DOI: 10.1002/bies.201400102] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
DNA double-strand breaks (DSBs) are one of the most deleterious forms of DNA damage and can result in cell inviability or chromosomal aberrations. The Mre11-Rad50-Nbs1 (MRN) ATPase-nuclease complex is a central player in the cellular response to DSBs and is implicated in the sensing and nucleolytic processing of DSBs, as well as in DSB signaling by activating the cell cycle checkpoint kinase ATM. ATP binding to Rad50 switches MRN from an open state with exposed Mre11 nuclease sites to a closed state with partially buried nuclease sites. The functional meaning of this switch remained unclear. A new study shows that ATP binding to Rad50 promotes DSB recognition, tethering, and ATM activation, while ATP hydrolysis opens the nuclease active sites to promote processing of DSBs. MRN thus emerges as functional switch that may coordinate the temporal transition from signaling to processing of DSBs.
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Affiliation(s)
- Karl-Peter Hopfner
- Department of Biochemistry, Gene Center, Ludwig-Maximilians-University, Munich, Germany; Center for Integrated Protein Science Munich, Gene Center, Ludwig-Maximilians-University, Munich, Germany
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50
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Liu T, Huang J. Quality control of homologous recombination. Cell Mol Life Sci 2014; 71:3779-97. [PMID: 24858417 PMCID: PMC11114062 DOI: 10.1007/s00018-014-1649-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 05/09/2014] [Indexed: 12/21/2022]
Abstract
Exogenous and endogenous genotoxic agents, such as ionizing radiation and numerous chemical agents, cause DNA double-strand breaks (DSBs), which are highly toxic and lead to genomic instability or tumorigenesis if not repaired accurately and efficiently. Cells have over evolutionary time developed certain repair mechanisms in response to DSBs to maintain genomic integrity. Major DSB repair mechanisms include non-homologous end joining and homologous recombination (HR). Using sister homologues as templates, HR is a high-fidelity repair pathway that can rejoin DSBs without introducing mutations. However, HR execution without appropriate guarding may lead to more severe gross genome rearrangements. Here we review current knowledge regarding the factors and mechanisms required for accomplishment of accurate HR.
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Affiliation(s)
- Ting Liu
- Life Sciences Institute, Zhejiang University, Hangzhou, 310058 Zhejiang China
| | - Jun Huang
- Life Sciences Institute, Zhejiang University, Hangzhou, 310058 Zhejiang China
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