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Wang L, Bitar M, Lu X, Jacquelin S, Nair S, Sivakumaran H, Hillman KM, Kaufmann S, Ziegman R, Casciello F, Gowda H, Rosenbluh J, Edwards SL, French JD. CRISPR-Cas13d screens identify KILR, a breast cancer risk-associated lncRNA that regulates DNA replication and repair. Mol Cancer 2024; 23:101. [PMID: 38745269 PMCID: PMC11094906 DOI: 10.1186/s12943-024-02021-y] [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: 11/17/2023] [Accepted: 05/09/2024] [Indexed: 05/16/2024] Open
Abstract
BACKGROUND Long noncoding RNAs (lncRNAs) have surpassed the number of protein-coding genes, yet the majority have no known function. We previously discovered 844 lncRNAs that were genetically linked to breast cancer through genome-wide association studies (GWAS). Here, we show that a subset of these lncRNAs alter breast cancer risk by modulating cell proliferation, and provide evidence that a reduced expression on one lncRNA increases breast cancer risk through aberrant DNA replication and repair. METHODS We performed pooled CRISPR-Cas13d-based knockdown screens in breast cells to identify which of the 844 breast cancer-associated lncRNAs alter cell proliferation. We selected one of the lncRNAs that increased cell proliferation, KILR, for follow-up functional studies. KILR pull-down followed by mass spectrometry was used to identify binding proteins. Knockdown and overexpression studies were performed to assess the mechanism by which KILR regulates proliferation. RESULTS We show that KILR functions as a tumor suppressor, safeguarding breast cells against uncontrolled proliferation. The half-life of KILR is significantly reduced by the risk haplotype, revealing an alternative mechanism by which variants alter cancer risk. Mechanistically, KILR sequesters RPA1, a subunit of the RPA complex required for DNA replication and repair. Reduced KILR expression promotes breast cancer cell proliferation by increasing the available pool of RPA1 and speed of DNA replication. Conversely, KILR overexpression promotes apoptosis in breast cancer cells, but not normal breast cells. CONCLUSIONS Our results confirm lncRNAs as mediators of breast cancer risk, emphasize the need to annotate noncoding transcripts in relevant cell types when investigating GWAS variants and provide a scalable platform for mapping phenotypes associated with lncRNAs.
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Affiliation(s)
- Lu Wang
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
- Faculty of Health, Queensland University of Technology, Brisbane, Australia
| | - Mainá Bitar
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
- Faculty of Health, Queensland University of Technology, Brisbane, Australia
- Faculty of Medicine, The University of Queensland, Brisbane, Australia
| | - Xue Lu
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Sebastien Jacquelin
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
- Macrophage Biology Laboratory, Mater Research, Brisbane, Australia
| | - Sneha Nair
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Haran Sivakumaran
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Kristine M Hillman
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Susanne Kaufmann
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Rebekah Ziegman
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Francesco Casciello
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Harsha Gowda
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Joseph Rosenbluh
- Cancer Research Program, Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, Australia
- Functional Genomics Platform, Monash University, Clayton, Australia
| | - Stacey L Edwards
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia.
- Faculty of Health, Queensland University of Technology, Brisbane, Australia.
- Faculty of Medicine, The University of Queensland, Brisbane, Australia.
| | - Juliet D French
- Cancer Research Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia.
- Faculty of Health, Queensland University of Technology, Brisbane, Australia.
- Faculty of Medicine, The University of Queensland, Brisbane, Australia.
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Wang J, Meng X, Chen X, Xiao J, Yu X, Wu L, Li Z, Chen K, Zhang X, Xiong B, Feng J. Cinchophen induces RPA1 related DNA damage and apoptosis to impair ENS development of zebrafish. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2024; 272:116032. [PMID: 38306819 DOI: 10.1016/j.ecoenv.2024.116032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 01/21/2024] [Accepted: 01/25/2024] [Indexed: 02/04/2024]
Abstract
Nonsteroidal anti-inflammatory drugs (NSAIDs) have become contaminants widely distributed in the environment due to improper disposal and discharge. Previous study has found several components might involve in impairing enteric nervous system (ENS) development of zebrafish, including NSAIDs cinchophen. Deficient ENS development in fetal could lead to Hirschsprung disease (HSCR), a congenital neurocristopathy characterized by absence of enteric neurons in hindgut. However, the intrinsic mechanism of neurotoxicity of cinchophen is unclear. We confirmed that cinchophen could impair ENS development of zebrafish and transcriptome sequencing revealed that disfunction of Replication protein A1 (RPA1), which is involved in DNA replication and repairment, might be relevant to the neurotoxicity effects induced by cinchophen. Based on previous data of single cell RNA sequencing (scRNA-seq) of zebrafish gut cells, we observed that rpa1 mainly expressed in proliferating, differentiating ENS cells and neural crest progenitors. Interestingly, cinchophen induced apoptosis and impaired proliferation. Furthermore, cinchophen caused DNA damage and abnormal activation of ataxia telangiectasia mutated/ Rad3 related (ATM/ATR) and checkpoint kinase 2 (CHK2). Finally, molecular docking indicated cinchophen could bind and antagonize RPA1 more effectively. Our study might provide a better understanding and draw more attention to the role of environmental factors in the pathogenesis of HSCR. And the mechanism of cinchophen neurotoxicity would give theoretical guidance for clinical pharmacy.
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Affiliation(s)
- Jing Wang
- Department of Pediatric Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Xinyao Meng
- Department of Pediatric Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Xuyong Chen
- Department of Pediatric Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Jun Xiao
- Department of Pediatric Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Xiaosi Yu
- Department of Pediatric Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Luyao Wu
- Department of Pediatric Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Zejian Li
- Department of Pediatric Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Ke Chen
- Department of Pediatric Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Xuan Zhang
- Department of Pediatric Surgery, Pingshan District Maternal & Child Healthcare Hospital of Shenzhen, Shenzhen 518000, China
| | - Bo Xiong
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
| | - Jiexiong Feng
- Department of Pediatric Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
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Mladenov E, Mladenova V, Stuschke M, Iliakis G. New Facets of DNA Double Strand Break Repair: Radiation Dose as Key Determinant of HR versus c-NHEJ Engagement. Int J Mol Sci 2023; 24:14956. [PMID: 37834403 PMCID: PMC10573367 DOI: 10.3390/ijms241914956] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 10/01/2023] [Accepted: 10/03/2023] [Indexed: 10/15/2023] Open
Abstract
Radiation therapy is an essential component of present-day cancer management, utilizing ionizing radiation (IR) of different modalities to mitigate cancer progression. IR functions by generating ionizations in cells that induce a plethora of DNA lesions. The most detrimental among them are the DNA double strand breaks (DSBs). In the course of evolution, cells of higher eukaryotes have evolved four major DSB repair pathways: classical non-homologous end joining (c-NHEJ), homologous recombination (HR), alternative end-joining (alt-EJ), and single strand annealing (SSA). These mechanistically distinct repair pathways have different cell cycle- and homology-dependencies but, surprisingly, they operate with widely different fidelity and kinetics and therefore contribute unequally to cell survival and genome maintenance. It is therefore reasonable to anticipate tight regulation and coordination in the engagement of these DSB repair pathway to achieve the maximum possible genomic stability. Here, we provide a state-of-the-art review of the accumulated knowledge on the molecular mechanisms underpinning these repair pathways, with emphasis on c-NHEJ and HR. We discuss factors and processes that have recently come to the fore. We outline mechanisms steering DSB repair pathway choice throughout the cell cycle, and highlight the critical role of DNA end resection in this process. Most importantly, however, we point out the strong preference for HR at low DSB loads, and thus low IR doses, for cells irradiated in the G2-phase of the cell cycle. We further explore the molecular underpinnings of transitions from high fidelity to low fidelity error-prone repair pathways and analyze the coordination and consequences of this transition on cell viability and genomic stability. Finally, we elaborate on how these advances may help in the development of improved cancer treatment protocols in radiation therapy.
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Affiliation(s)
- Emil Mladenov
- Division of Experimental Radiation Biology, Department of Radiation Therapy, University Hospital Essen, University of Duisburg-Essen, 45122 Essen, Germany; (V.M.); (M.S.)
- Institute of Medical Radiation Biology, University Hospital Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Veronika Mladenova
- Division of Experimental Radiation Biology, Department of Radiation Therapy, University Hospital Essen, University of Duisburg-Essen, 45122 Essen, Germany; (V.M.); (M.S.)
- Institute of Medical Radiation Biology, University Hospital Essen, University of Duisburg-Essen, 45122 Essen, Germany
| | - Martin Stuschke
- Division of Experimental Radiation Biology, Department of Radiation Therapy, University Hospital Essen, University of Duisburg-Essen, 45122 Essen, Germany; (V.M.); (M.S.)
- German Cancer Consortium (DKTK), Partner Site University Hospital Essen, 45147 Essen, Germany
- German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - George Iliakis
- Division of Experimental Radiation Biology, Department of Radiation Therapy, University Hospital Essen, University of Duisburg-Essen, 45122 Essen, Germany; (V.M.); (M.S.)
- Institute of Medical Radiation Biology, University Hospital Essen, University of Duisburg-Essen, 45122 Essen, Germany
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4
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Miao X, Guo R, Williams A, Lee C, Ma J, Wang PJ, Cui W. Replication Protein A1 is essential for DNA damage repair during mammalian oogenesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.04.547725. [PMID: 37461444 PMCID: PMC10349974 DOI: 10.1101/2023.07.04.547725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/30/2023]
Abstract
Persistence of unrepaired DNA damage in oocytes is detrimental and may cause genetic aberrations, miscarriage, and infertility. RPA, an ssDNA-binding complex, is essential for various DNA-related processes. Here we report that RPA plays a novel role in DNA damage repair during postnatal oocyte development after meiotic recombination. To investigate the role of RPA during oogenesis, we inactivated RPA1 (replication protein A1), the largest subunit of the heterotrimeric RPA complex, specifically in oocytes using two germline-specific Cre drivers (Ddx4-Cre and Zp3-Cre). We find that depletion of RPA1 leads to the disassembly of the RPA complex, as evidenced by the absence of RPA2 and RPA3 in RPA1-deficient oocytes. Strikingly, severe DNA damage occurs in RPA1-deficient GV-stage oocytes. Loss of RPA in oocytes triggered the canonical DNA damage response mechanisms and pathways, such as activation of ATM, ATR, DNA-PK, and p53. In addition, the RPA deficiency causes chromosome misalignment at metaphase I and metaphase II stages of oocytes, which is consistent with altered transcript levels of genes involved in cytoskeleton organization in RPA1-deficient oocytes. Absence of the RPA complex in oocytes severely impairs folliculogenesis and leads to a significant reduction in oocyte number and female infertility. Our results demonstrate that RPA plays an unexpected role in DNA damage repair during mammalian folliculogenesis.
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Affiliation(s)
- Xiaosu Miao
- Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA, USA
| | - Rui Guo
- Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA, USA
- NHC Key Laboratory of Study on Abnormal Gametes and Reproductive Tract, Anhui Medical University, Hefei, Anhui, China
| | - Andrea Williams
- Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA, USA
| | - Catherine Lee
- Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA, USA
| | - Jun Ma
- Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA, USA
| | - P. Jeremy Wang
- Department of Biomedical Sciences, University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA, USA
| | - Wei Cui
- Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA, USA
- Animal Models Core Facility, Institute for Applied Life Sciences (IALS), University of Massachusetts, Amherst, MA, USA
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Holland CL, Weis MF, England CJ, Berry AM, Hall PD, Lewis LK. Deficiency in homologous recombination is associated with changes in cell cycling and morphology in Saccharomyces cerevisiae. Exp Cell Res 2023:113701. [PMID: 37393982 DOI: 10.1016/j.yexcr.2023.113701] [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: 05/04/2023] [Revised: 06/23/2023] [Accepted: 06/25/2023] [Indexed: 07/04/2023]
Abstract
Exposure of eukaryotic cells to ionizing radiation or clastogenic chemicals leads to formation of DNA double-strand breaks (DSBs). These lesions are also generated internally by chemicals and enzymes, in the absence of exogenous agents, though the sources and consequences of such endogenously generated DSBs remain poorly understood. In the current study, we have investigated the impact of reduced recombinational repair of endogenous DSBs on stress responses, cell morphology and other physical properties of S. cerevisiae (budding yeast) cells. Use of phase contrast and DAPI-based fluorescence microscopy combined with FACS analysis confirmed that recombination-deficient rad52 cell cultures exhibit chronically high levels of G2 phase cells. Cell cycle phase transit times during G1, S and M were similar in WT and rad52 cells, but the length of G2 phase was increased by three-fold in the mutants. rad52 cells were larger than WT in all phases of the cycle and displayed other quantifiable changes in physical characteristics. The high G2 cell phenotype was abolished when DNA damage checkpoint genes, but not spindle assembly checkpoint genes, were co-inactivated with RAD52. Several other RAD52 group mutants (rad51, rad54, rad55, rad57 and rad59) also exhibited the high G2 cell phenotype. The results indicate that recombination deficiency leads to accumulation of unrepaired DSBs during normal mitotic growth that activate a major stress response and produce distinct changes in cellular physiology and morphology.
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Affiliation(s)
- Cory L Holland
- Chemistry and Biochemistry, Texas State University, 601 University Drive, San Marcos, TX, 78666, USA
| | - Monica F Weis
- Chemistry and Biochemistry, Texas State University, 601 University Drive, San Marcos, TX, 78666, USA
| | - Corbin J England
- Chemistry and Biochemistry, Texas State University, 601 University Drive, San Marcos, TX, 78666, USA
| | - Armand M Berry
- Chemistry and Biochemistry, Texas State University, 601 University Drive, San Marcos, TX, 78666, USA
| | - Paige D Hall
- Chemistry and Biochemistry, Texas State University, 601 University Drive, San Marcos, TX, 78666, USA
| | - L Kevin Lewis
- Chemistry and Biochemistry, Texas State University, 601 University Drive, San Marcos, TX, 78666, USA.
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Yao X, Wang C, Sun L, Yan L, Chen X, Lv Z, Xie X, Tian S, Liu W, Li L, Zhang H, Liu J. BCAS2 regulates granulosa cell survival by participating in mRNA alternative splicing. J Ovarian Res 2023; 16:104. [PMID: 37248466 DOI: 10.1186/s13048-023-01187-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 05/14/2023] [Indexed: 05/31/2023] Open
Abstract
BACKGROUND Granulosa cell proliferation and differentiation are essential for follicle development. Breast cancer amplified sequence 2 (BCAS2) is necessary for spermatogenesis, oocyte development, and maintaining the genome integrity of early embryos in mice. However, the function of BCAS2 in granulosa cells is still unknown. RESULTS We show that conditional disruption of Bcas2 in granulosa cells caused follicle development failure; the ratio of the positive cells of the cell proliferation markers PCNA and Ki67 were unchanged in granulosa cells. Specific deletion of Bcas2 caused a decrease in the BrdU-positive cell ratio, cell cycle arrest, DNA damage, and an increase in apoptosis in granulosa cells, and RPA1 was abnormally stained in granulosa cells. RNA-seq results revealed that knockout of Bcas2 results in unusual expression of cellular senescence genes. BCAS2 participated in the PRP19 complex to mediate alternative splicing (AS) of E2f3 and Flt3l mRNA to inhibit the cell cycle. Knockout of Bcas2 resulted in a significant decrease in the ratio of BrdU-positive cells in the human granulosa-like tumour (KGN) cell line. CONCLUSIONS Our results suggest that BCAS2 may influence the proliferation and survival of granulosa cells through regulating pre-mRNA splicing of E2f3 and Flt3l by forming the splicing complex with CDC5L and PRP19.
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Affiliation(s)
- Xiaohong Yao
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Chaofan Wang
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Longjie Sun
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Lu Yan
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Xuexue Chen
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Zheng Lv
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Xiaomei Xie
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Shuang Tian
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Wenbo Liu
- Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Guangdong Provincial Key Laboratory of Major Obstetric Diseases, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Lei Li
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Hua Zhang
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing, 100193, China.
| | - Jiali Liu
- State Key Laboratory of Animal Biotech Breeding, College of Biological Sciences, China Agricultural University, Beijing, 100193, China.
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Activation of DNA damage response signaling in mammalian cells by ionizing radiation. Free Radic Res 2021; 55:581-594. [PMID: 33455476 DOI: 10.1080/10715762.2021.1876853] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Cellular responses to DNA damage are fundamental to preserve genomic integrity during various endogenous and exogenous stresses. Following radiation therapy and chemotherapy, this DNA damage response (DDR) also determines development of carcinogenesis and therapeutic outcome. In humans, DNA damage activates a robust network of signal transduction cascades, driven primarily through phosphorylation events. These responses primarily involve two key non-redundant signal transducing proteins of phosphatidylinositol 3-kinase-like (PIKK) family - ATR and ATM, and their downstream kinases (hChk1 and hChk2). They further phosphorylate effectors proteins such as p53, Cdc25A and Cdc25C which function either to activate the DNA damage checkpoints and cell death mechanisms, or DNA repair pathways. Identification of molecular pathways that determine signaling after DNA damage and trigger DNA repair in response to differing types of DNA lesions allows for a far better understanding of the consequences of radiation and chemotherapy on normal and tumor cells. Here we highlight the network of DNA damage response pathways that are activated after treatment with different types of radiation. Further, we discuss regulation of cell cycle checkpoint and DNA repair processes in the context of DDR in response to radiation.
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Velegzhaninov IO, Belykh ES, Rasova EE, Pylina YI, Shadrin DM, Klokov DY. Radioresistance, DNA Damage and DNA Repair in Cells With Moderate Overexpression of RPA1. Front Genet 2020; 11:855. [PMID: 32849834 PMCID: PMC7411226 DOI: 10.3389/fgene.2020.00855] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Accepted: 07/13/2020] [Indexed: 12/02/2022] Open
Abstract
Molecular responses to genotoxic stress, such as ionizing radiation, are intricately complex and involve hundreds of genes. Whether targeted overexpression of an endogenous gene can enhance resistance to ionizing radiation remains to be explored. In the present study we take an advantage of the CRISPR/dCas9 technology to moderately overexpress the RPA1 gene that encodes a key functional subunit of the replication protein A (RPA). RPA is a highly conserved heterotrimeric single-stranded DNA-binding protein complex involved in DNA replication, recombination, and repair. Dysfunction of RPA1 is detrimental for cells and organisms and can lead to diminished resistance to many stress factors. We demonstrate that HEK293T cells overexpressing RPA1 exhibit enhanced resistance to cell killing by gamma-radiation. Using the alkali comet assay, we show a remarkable acceleration of DNA breaks rejoining after gamma-irradiation in RPA1 overexpressing cells. However, the spontaneous rate of DNA damage was also higher in the presence of RPA1 overexpression, suggesting alterations in the processing of replication errors due to elevated activity of the RPA protein. Additionally, the analysis of the distributions of cells with different levels of DNA damage showed a link between the RPA1 overexpression and the kinetics of DNA repair within differentially damaged cell subpopulations. Our results provide knew knowledge on DNA damage stress responses and indicate that the concept of enhancing radioresistance by targeted alteration of the expression of a single gene is feasible, however undesired consequences should be considered and evaluated.
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Affiliation(s)
- Ilya O Velegzhaninov
- Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences, Syktyvkar, Russia
| | - Elena S Belykh
- Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences, Syktyvkar, Russia
| | - Elena E Rasova
- Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences, Syktyvkar, Russia
| | - Yana I Pylina
- Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences, Syktyvkar, Russia
| | - Dmitry M Shadrin
- Institute of Biology of Komi Scientific Centre of the Ural Branch of the Russian Academy of Sciences, Syktyvkar, Russia
| | - Dmitry Yu Klokov
- Institut de Radioprotection et de Sureté Nucléaire, PSE-SANTE, SESANE, LRTOX, Fontenay-aux-Roses, France.,Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
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9
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Guo Y, Chen J, Feng Y, Chua MLK, Zeng Y, Hui EP, Chan AKC, Tang L, Wang L, Cui Q, Han H, Luo C, Lin G, Liang Y, Liu Y, He Z, Liu Y, Wei P, Liu C, Peng W, Han B, Zuo X, Ong EHW, Yeo ELL, Low KP, Tan GS, Lim TKH, Hwang JSG, Li B, Feng Q, Xia X, Xia Y, Ko J, Dai W, Lung ML, Chan ATC, Lo DYM, Zeng M, Mai H, Liu J, Zeng Y, Bei J. Germline Polymorphisms and Length of Survival of Nasopharyngeal Carcinoma: An Exome-Wide Association Study in Multiple Cohorts. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:1903727. [PMID: 32440486 PMCID: PMC7237860 DOI: 10.1002/advs.201903727] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/14/2020] [Accepted: 02/17/2020] [Indexed: 06/11/2023]
Abstract
Germline polymorphisms are linked with differential survival outcomes in cancers but are not well studied in nasopharyngeal carcinoma (NPC). Here, a two-phase association study is conducted to discover germline polymorphisms that are associated with the prognosis of NPC. The discovery phase includes two consecutive hospital cohorts of patients with NPC from Southern China. Exome-wide genotypes at 246 173 single nucleotide polymorphisms (SNPs) are determined, followed by survival analysis for each SNP under Cox proportional hazard regression model. Candidate SNP is replicated in another two independent cohorts from Southern China and Singapore. Meta-analysis of all samples (n = 5553) confirms that the presence of rs1131636-T, located in the 3'-UTR of RPA1, confers an inferior overall survival (HR = 1.33, 95% CI = 1.20-1.47, P = 6.31 × 10-8). Bioinformatics and biological assays show that rs1131636 has regulatory effects on upstream RPA1. Functional studies further demonstrate that RPA1 promotes the growth, invasion, migration, and radioresistance of NPC cells. Additionally, miR-1253 is identified as a suppressor for RPA1 expression, likely through regulation of its binding affinity to rs1131636 locus. Collectively, these findings provide a promising biomarker aiding in stratifying patients with poor survival, as well as a potential drug target for NPC.
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Chauhan N, Wagh V, Joshi P, Jariyal H. ATM and ATR checkpoint kinase pathways: A concise review. ADVANCES IN HUMAN BIOLOGY 2020. [DOI: 10.4103/aihb.aihb_78_19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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11
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Kim JL, Ha GH, Campo L, Breuer EK. Negative regulation of BRCA1 by transforming acidic coiled-coil protein 3 (TACC3). Biochem Biophys Res Commun 2018; 496:633-640. [PMID: 29355525 DOI: 10.1016/j.bbrc.2018.01.101] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 01/15/2018] [Indexed: 01/13/2023]
Abstract
In spite of the push to identify modifiers of BRCAness, it still remains unclear how tumor suppressor BRCA1 is lost in breast cancers in the absence of genetic or epigenetic aberrations. Mounting evidence indicates that the transforming acidic coiled-coil 3 (TACC3) plays an important role in the centrosome-microtubule network during mitosis and gene expression, and that deregulation of TACC3 is associated with breast cancer. However, the molecular mechanisms by which TACC3 contributes to breast cancer development have yet to be elucidated. Herein, we found that high levels of TACC3 in human mammary epithelial cells can cause genomic instability possibly in part through destabilizing BRCA1. We also found that high levels of TACC3 inhibited the interaction between BRCA1 and BARD1, thus subsequently allowing the BARD1-uncoupled BRCA1 to be destabilized by ubiquitin-mediated proteosomal pathway. Moreover, there is an inverse correlation between TACC3 and BRCA1 expression in breast cancer tissues. Overall, our findings provide a new insight into the role of TACC3 in genomic instability and breast tumorigenesis.
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Affiliation(s)
- Jung-Lye Kim
- Department of Radiation Oncology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, 60153, USA
| | - Geun-Hyoung Ha
- Department of Radiation Oncology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, 60153, USA
| | - Loredana Campo
- Department of Radiation Oncology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, 60153, USA
| | - Eun-Kyoung Breuer
- Department of Radiation Oncology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, 60153, USA.
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Abstract
Proliferating cells rely on the so-called DNA replication checkpoint to ensure orderly completion of genome duplication, and its malfunction may lead to catastrophic genome disruption, including unscheduled firing of replication origins, stalling and collapse of replication forks, massive DNA breakage, and, ultimately, cell death. Despite many years of intensive research into the molecular underpinnings of the eukaryotic replication checkpoint, the mechanisms underlying the dismal consequences of its failure remain enigmatic. A recent development offers a unifying model in which the replication checkpoint guards against global exhaustion of rate-limiting replication regulators. Here we discuss how such a mechanism can prevent catastrophic genome disruption and suggest how to harness this knowledge to advance therapeutic strategies to eliminate cancer cells that inherently proliferate under increased DNA replication stress.
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Affiliation(s)
- Luis Toledo
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen, Denmark; Center for Chromosome Stability, Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen, Denmark.
| | - Kai John Neelsen
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen, Denmark
| | - Jiri Lukas
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen, Denmark.
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13
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Köhler C, Koalick D, Fabricius A, Parplys AC, Borgmann K, Pospiech H, Grosse F. Cdc45 is limiting for replication initiation in humans. Cell Cycle 2017; 15:974-85. [PMID: 26919204 PMCID: PMC4889307 DOI: 10.1080/15384101.2016.1152424] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cdc45 is an essential protein that together with Mcm2-7 and GINS forms the eukaryotic replicative helicase CMG. Cdc45 seems to be rate limiting for the initial unwinding or firing of replication origins. In line with this view, Cdc45-overexpressing cells fired at least twice as many origins as control cells. However, these cells displayed an about 2-fold diminished fork elongation rate, a pronounced asymmetry of replication fork extension, and an early S phase arrest. This was accompanied by H2AX-phosphorylation and subsequent apoptosis. Unexpectedly, we did not observe increased ATR/Chk1 signaling but rather a mild ATM/Chk2 response. In addition, we detected accumulation of long stretches of single-stranded DNA, a hallmark of replication catastrophe. We conclude that increased origin firing by upregulated Cdc45 caused exhaustion of the single-strand binding protein RPA, which in consequence diminished the ATR/Chk1 response; the subsequently occurring fork breaks led to an ATM/Chk2 mediated phosphorylation of H2AX and eventually to apoptosis.
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Affiliation(s)
- Carsten Köhler
- a Research group Biochemistry, Leibniz Institute for Age Research - Fritz Lipmann Institute , Jena , Germany
| | - Dennis Koalick
- a Research group Biochemistry, Leibniz Institute for Age Research - Fritz Lipmann Institute , Jena , Germany
| | - Anja Fabricius
- a Research group Biochemistry, Leibniz Institute for Age Research - Fritz Lipmann Institute , Jena , Germany
| | - Ann Christin Parplys
- b Laboratory of Radiobiology and Experimental Radiation Oncology, University Medical Center Hamburg-Eppendorf , Hamburg , Germany
| | - Kerstin Borgmann
- b Laboratory of Radiobiology and Experimental Radiation Oncology, University Medical Center Hamburg-Eppendorf , Hamburg , Germany
| | - Helmut Pospiech
- a Research group Biochemistry, Leibniz Institute for Age Research - Fritz Lipmann Institute , Jena , Germany.,c Faculty of Biochemistry and Molecular Medicine, University of Oulu , Finland
| | - Frank Grosse
- a Research group Biochemistry, Leibniz Institute for Age Research - Fritz Lipmann Institute , Jena , Germany.,d Centre for Molecular Biomedicine, Friedrich-Schiller University , Jena , Germany
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14
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Jang SW, Jung JK, Kim JM. Replication Protein A (RPA) deficiency activates the Fanconi anemia DNA repair pathway. Cell Cycle 2016; 15:2336-45. [PMID: 27398742 DOI: 10.1080/15384101.2016.1201621] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The Fanconi anemia (FA) pathway regulates DNA inter-strand crosslink (ICL) repair. Despite our greater understanding of the role of FA in ICL repair, its function in the preventing spontaneous genome instability is not well understood. Here, we show that depletion of replication protein A (RPA) activates the FA pathway. RPA1 deficiency increases chromatin recruitment of FA core complex, leading to FANCD2 monoubiquitination (FANCD2-Ub) and foci formation in the absence of DNA damaging agents. Importantly, ATR depletion, but not ATM, abolished RPA1 depletion-induced FANCD2-Ub, suggesting that ATR activation mediated FANCD2-Ub. Interestingly, we found that depletion of hSSB1/2-INTS3, a single-stranded DNA-binding protein complex, induces FANCD2-Ub, like RPA1 depletion. More interestingly, depletion of either RPA1 or INTS3 caused increased accumulation of DNA damage in FA pathway deficient cell lines. Taken together, these results indicate that RPA deficiency induces activation of the FA pathway in an ATR-dependent manner, which may play a role in the genome maintenance.
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Affiliation(s)
- Seok-Won Jang
- a Department of Pharmacology , Medical Research Center for Gene Regulation, Chonnam National University Medical School , Gwangju , Korea
| | - Jin Ki Jung
- a Department of Pharmacology , Medical Research Center for Gene Regulation, Chonnam National University Medical School , Gwangju , Korea
| | - Jung Min Kim
- a Department of Pharmacology , Medical Research Center for Gene Regulation, Chonnam National University Medical School , Gwangju , Korea
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15
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miR-30a can inhibit DNA replication by targeting RPA1 thus slowing cancer cell proliferation. Biochem J 2016; 473:2131-9. [PMID: 27208176 DOI: 10.1042/bcj20160177] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 05/17/2016] [Indexed: 02/04/2023]
Abstract
Cell proliferation was inhibited following forced over-expression of miR-30a in the ovary cancer cell line A2780DX5 and the gastric cancer cell line SGC7901R. Interestingly, miR-30a targets the DNA replication protein RPA1, hinders the replication of DNA and induces DNA fragmentation. Furthermore, ataxia telangiectasia mutated (ATM) and checkpoint kinase 2 (CHK2) were phosphorylated after DNA damage, which induced p53 expression, thus triggering the S-phase checkpoint, arresting cell cycle progression and ultimately initiating cancer cell apoptosis. Therefore, forced miR-30a over-expression in cancer cells can be a potential way to inhibit tumour development.
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16
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Abstract
ATR (Ataxia Telangiectasia and Rad3-related) is a member of the Phosphatidylinositol 3-kinase-related kinases (PIKKs) family, amongst six other vertebrate proteins known so far. ATR is indispensable for cell survival and its essential role is in sensing DNA damage and initiating appropriate repair responses. In this review we highlight emerging and recent observations connecting ATR to alternative roles in controlling the nuclear envelope, nucleolus, centrosome and other organelles in response to both internal and external stress conditions. We propose that ATR functions control cell plasticity by sensing structural deformations of different cellular components, including DNA and initiating appropriate repair responses, most of which are yet to be understood completely.
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Affiliation(s)
- Gururaj Rao Kidiyoor
- Istituto FIRC di Oncologia Molecolare, Milan, Italy; University of Milan, Milan, Italy
| | - Amit Kumar
- Developmental Toxicology Laboratory, Systems Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research, M.G. Marg, Lucknow 226001, India; Academy of Scientific and Innovative Research (AcSIR), India
| | - Marco Foiani
- Istituto FIRC di Oncologia Molecolare, Milan, Italy; University of Milan, Milan, Italy.
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17
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Abstract
ATM and ATR signaling pathways are well conserved throughout evolution and are central to the maintenance of genome integrity. Although the role of both ATM and ATR in DNA repair, cell cycle regulation and apoptosis have been well studied, both still remain in the focus of current research activities owing to their role in cancer. Recent advances in the field suggest that these proteins have an additional function in maintaining cellular homeostasis under both stressed and non-stressed conditions. In this Cell Science at a Glance article and the accompanying poster, we present an overview of recent advances in ATR and ATM research with emphasis on that into the modes of ATM and ATR activation, the different signaling pathways they participate in - including those that do not involve DNA damage - and highlight their relevance in cancer.
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Affiliation(s)
- Poorwa Awasthi
- Developmental Toxicology Laboratory, Systems Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research, M.G. Marg 80, Lucknow 226001, India Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR campus, Lucknow 226001, India
| | - Marco Foiani
- IFOM (Fondazione Istituto FIRC di Oncologia Molecolare), IFOM-IEO Campus Via Adamello 16, Milan 20139, Italy DSBB-Università degli Studi di Milano, Milan 20133, Italy
| | - Amit Kumar
- Developmental Toxicology Laboratory, Systems Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research, M.G. Marg 80, Lucknow 226001, India Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR campus, Lucknow 226001, India
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18
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Guven M, Brem R, Macpherson P, Peacock M, Karran P. Oxidative Damage to RPA Limits the Nucleotide Excision Repair Capacity of Human Cells. J Invest Dermatol 2015; 135:2834-2841. [PMID: 26134950 DOI: 10.1038/jid.2015.255] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 06/01/2015] [Accepted: 06/18/2015] [Indexed: 12/13/2022]
Abstract
Nucleotide excision repair (NER) protects against sunlight-induced skin cancer. Defective NER is associated with photosensitivity and a high skin cancer incidence. Some clinical treatments that cause photosensitivity can also increase skin cancer risk. Among these, the immunosuppressant azathioprine and the fluoroquinolone antibiotics ciprofloxacin and ofloxacin interact with UVA radiation to generate reactive oxygen species that diminish NER capacity by causing protein damage. The replication protein A (RPA) DNA-binding protein has a pivotal role in DNA metabolism and is an essential component of NER. The relationship between protein oxidation and NER inhibition was investigated in cultured human cells expressing different levels of RPA. We show here that RPA is limiting for NER and that oxidative damage to RPA compromises NER capability. Our findings reveal that cellular RPA is surprisingly vulnerable to oxidation, and we identify oxidized forms of RPA that are associated with impaired NER. The vulnerability of NER to inhibition by oxidation provides a connection between cutaneous photosensitivity, protein damage, and increased skin cancer risk. Our findings emphasize that damage to DNA repair proteins, as well as to DNA itself, is likely to be an important contributor to skin cancer risk.
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Affiliation(s)
- Melisa Guven
- Francis Crick Institute, Clare Hall Laboratory, South Mimms, Herts, UK
| | - Reto Brem
- Francis Crick Institute, Clare Hall Laboratory, South Mimms, Herts, UK
| | - Peter Macpherson
- Francis Crick Institute, Clare Hall Laboratory, South Mimms, Herts, UK
| | - Matthew Peacock
- Francis Crick Institute, Clare Hall Laboratory, South Mimms, Herts, UK
| | - Peter Karran
- Francis Crick Institute, Clare Hall Laboratory, South Mimms, Herts, UK.
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19
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Kar A, Kaur M, Ghosh T, Khan MM, Sharma A, Shekhar R, Varshney A, Saxena S. RPA70 depletion induces hSSB1/2-INTS3 complex to initiate ATR signaling. Nucleic Acids Res 2015; 43:4962-74. [PMID: 25916848 PMCID: PMC4446429 DOI: 10.1093/nar/gkv369] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 04/08/2015] [Indexed: 01/12/2023] Open
Abstract
The primary eukaryotic single-stranded DNA-binding protein, Replication protein A (RPA), binds to single-stranded DNA at the sites of DNA damage and recruits the apical checkpoint kinase, ATR via its partner protein, ATRIP. It has been demonstrated that absence of RPA incapacitates the ATR-mediated checkpoint response. We report that in the absence of RPA, human single-stranded DNA-binding protein 1 (hSSB1) and its partner protein INTS3 form sub-nuclear foci, associate with the ATR-ATRIP complex and recruit it to the sites of genomic stress. The ATRIP foci formed after RPA depletion are abrogated in the absence of INTS3, establishing that hSSB-INTS3 complex recruits the ATR-ATRIP checkpoint complex to the sites of genomic stress. Depletion of homologs hSSB1/2 and INTS3 in RPA-deficient cells attenuates Chk1 phosphorylation, indicating that the cells are debilitated in responding to stress. We have identified that TopBP1 and the Rad9-Rad1-Hus1 complex are essential for the alternate mode of ATR activation. In summation, we report that the single-stranded DNA-binding protein complex, hSSB1/2-INTS3 can recruit the checkpoint complex to initiate ATR signaling.
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Affiliation(s)
- Ananya Kar
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Manpreet Kaur
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Tanushree Ghosh
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Md Muntaz Khan
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Aparna Sharma
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Ritu Shekhar
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Akhil Varshney
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Sandeep Saxena
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
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20
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Hu L, Wu Y, Tan D, Meng H, Wang K, Bai Y, Yang K. Up-regulation of long noncoding RNA MALAT1 contributes to proliferation and metastasis in esophageal squamous cell carcinoma. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2015; 34:7. [PMID: 25613496 PMCID: PMC4322446 DOI: 10.1186/s13046-015-0123-z] [Citation(s) in RCA: 187] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Accepted: 01/04/2015] [Indexed: 01/26/2023]
Abstract
BACKGROUND Metastasis Associated Lung Adenocarcinoma Transcript 1 (MALAT1) has been demonstrated to be an important player in various human malignancies; it is thought to promote tumor growth by cell cycle regulating. However, the roles of MALAT1 in esophageal squamous cell carcinoma(ESCC), and the mechanisms involved in cell cycle regulation remain poorly understood. Moreover, the factors contributing to its up-regulation in tumor tissues are still largely unclear. METHODS Expression of MALAT1 was determined from cell lines and clinical samples by qRT-PCR. The effects of MALAT1 knockdown on cell proliferation, cell cycle, apoptosis, migration, and invasion were evaluated by in vitro and in vivo assays. The potential protein expression changes were investigated by Western-blotting. The methylation status of the CpG island in the MALAT1 promoter was explored by bisulfite sequencing, while the copy numbers in tumor tissues and blood samples were detected by a well-established AccuCopy(TM) method. RESULTS MALAT1 was over-expressed in 46.3% of ESCC tissues, mostly in the high-stage tumor samples. Enhanced MALAT1 expression levels were positively correlated with clinical stages, primary tumor size, and lymph node metastasis. Inhibition of MALAT1 suppressed tumor proliferation in vitro and in vivo, as well as the migratory and invasive capacity. MALAT1 depletion also induced G2/M phase arrest and increased the percentage of apoptotic cells. Western-blotting results implicated that the ATM-CHK2 pathway which is associated with G2/M arrest was phosphorylated by MALAT1 knockdown. No effects of CpG island methylation status on MALAT1 expression were found, whereas amplification of MALAT1 was found in 22.2% of tumor tissues, which correlated significantly with its over-expression. However, neither association between tissue copy number amplification and germline copy number variation, nor correlation between germline copy number variation and ESCC risk were identified in the case-control study. CONCLUSIONS Our data suggest that MALAT1 serves as an oncogene in ESCC, and it regulates ESCC growth by modifying the ATM-CHK2 pathway. Moreover, amplification of MALAT1 in tumor tissues may play an important role for its up-regulation, and it seems that the gene amplification in tumor tissues emerges during ESCC progression, but is not derived from germline origins.
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Affiliation(s)
- Liwen Hu
- Department of Cardiothoracic Surgery, Southwest Hospital, Third Military Medical University, Gaotanyan St., Shapingba District, Chongqing, People's Republic of China.
| | - Yuanyuan Wu
- Department of Medical Genetics, College of Basic Medical Science, Third Military Medical University, Gaotanyan St., Shapingba District, Chongqing, People's Republic of China.
| | - Deli Tan
- Department of Cardiothoracic Surgery, Southwest Hospital, Third Military Medical University, Gaotanyan St., Shapingba District, Chongqing, People's Republic of China.
| | - Hui Meng
- Department of Medical Genetics, College of Basic Medical Science, Third Military Medical University, Gaotanyan St., Shapingba District, Chongqing, People's Republic of China.
| | - Kai Wang
- Department of Medical Genetics, College of Basic Medical Science, Third Military Medical University, Gaotanyan St., Shapingba District, Chongqing, People's Republic of China.
| | - Yun Bai
- Department of Medical Genetics, College of Basic Medical Science, Third Military Medical University, Gaotanyan St., Shapingba District, Chongqing, People's Republic of China.
| | - Kang Yang
- Department of Cardiothoracic Surgery, Southwest Hospital, Third Military Medical University, Gaotanyan St., Shapingba District, Chongqing, People's Republic of China.
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21
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Li P, Ma X, Adams IR, Yuan P. A tight control of Rif1 by Oct4 and Smad3 is critical for mouse embryonic stem cell stability. Cell Death Dis 2015; 6:e1588. [PMID: 25569105 PMCID: PMC4669749 DOI: 10.1038/cddis.2014.551] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Revised: 11/03/2014] [Accepted: 11/17/2014] [Indexed: 12/20/2022]
Abstract
Prolonged culture of embryonic stem cells (ESCs) leads them to adopt embryonal carcinoma cell features, creating enormous dangers for their further application. The mechanism involved in ESC stability has not, however, been extensively studied. We previously reported that SMAD family member 3 (Smad3) has an important role in maintaining mouse ESC stability, as depletion of Smad3 results in cancer cell-like properties in ESCs and Smad3-/- ESCs are prone to grow large, malignant teratomas. To understand how Smad3 contributes to ESC stability, we performed microarray analysis to compare the transcriptome of wild-type and Smad3-/- ESCs. We found that Rif1 (RAP1-associated protein 1), a factor important for genomic stability, is significantly upregulated in Smad3-/- ESCs. The expression level of Rif1 needs to be tightly controlled in ESCs, as a low level of Rif1 is associated with ESC differentiation, but a high level of Rif1 is linked to ESC transformation. In ESCs, Oct4 activates Rif1, whereas Smad3 represses its expression. Oct4 recruits Smad3 to bind to Rif1 promoter, but Smad3 joining facilitates the loading of a polycomb complex that generates a repressive epigenetic modification on Rif1 promoter, and thus maintains the expression of Rif1 at a proper level in ESCs. Interestingly, Rif1 short hairpin RNA (shRNA)-transduced Smad3-/- ESCs showed less malignant properties than the control shRNA-transduced Smad3-/- ESCs, suggesting a critical role of Rif1 in maintaining the stability of ESCs during proliferation.
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Affiliation(s)
- P Li
- 1] Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China [2] Department of Chemical Pathology, Stem Cell and Functional Genomics, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China [3] The Chinese University of Hong Kong Shenzhen Research Institute, Shenzhen, China
| | - X Ma
- 1] Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China [2] Department of Chemical Pathology, Stem Cell and Functional Genomics, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - I R Adams
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, UK
| | - P Yuan
- 1] Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China [2] Department of Chemical Pathology, Stem Cell and Functional Genomics, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China [3] The Chinese University of Hong Kong Shenzhen Research Institute, Shenzhen, China [4] School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
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22
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González Besteiro MA, Gottifredi V. The fork and the kinase: a DNA replication tale from a CHK1 perspective. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2014; 763:168-80. [PMID: 25795119 DOI: 10.1016/j.mrrev.2014.10.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2014] [Revised: 10/07/2014] [Accepted: 10/10/2014] [Indexed: 11/30/2022]
Abstract
Replication fork progression is being continuously hampered by exogenously introduced and naturally occurring DNA lesions and other physical obstacles. Checkpoint kinase 1 (Chk1) is activated at replication forks that encounter damaged DNA. Subsequently, Chk1 inhibits the initiation of new replication factories and stimulates the firing of dormant origins (those in the vicinity of stalled forks). Chk1 also avoids fork collapse into DSBs (double strand breaks) and promotes fork elongation. At the molecular level, the current model considers stalled forks as the site of Chk1 activation and the nucleoplasm as the location where Chk1 phosphorylates target proteins. This model certainly serves to explain how Chk1 modulates origin firing, but how Chk1 controls the fate of stalled forks is less clear. Interestingly, recent reports demonstrating that Chk1 phosphorylates chromatin-bound proteins and even holds kinase-independent functions might shed light on how Chk1 contributes to the elongation of damaged DNA. Indeed, such findings have unveiled a puzzling connection between Chk1 and DNA lesion bypass, which might be central to promoting fork elongation and checkpoint attenuation. In summary, Chk1 is a multifaceted and versatile signaling factor that acts at ongoing forks and replication origins to determine the extent and quality of the cellular response to replication stress.
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Affiliation(s)
- Marina A González Besteiro
- Cell Cycle and Genomic Stability Laboratory, Fundación Instituto Leloir, CONICET, Buenos Aires, Argentina
| | - Vanesa Gottifredi
- Cell Cycle and Genomic Stability Laboratory, Fundación Instituto Leloir, CONICET, Buenos Aires, Argentina.
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23
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TACC3 deregulates the DNA damage response and confers sensitivity to radiation and PARP inhibition. Oncogene 2014; 34:1667-78. [PMID: 24769898 DOI: 10.1038/onc.2014.105] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 02/28/2014] [Accepted: 03/12/2014] [Indexed: 12/21/2022]
Abstract
Deregulation of the transforming acidic coiled-coil protein 3 (TACC3), an important factor in the centrosome-microtubule system, has been linked to a variety of human cancer types. We have recently reported on the oncogenic potential of TACC3; however, the molecular mechanisms by which TACC3 mediates oncogenic function remain to be elucidated. In this study, we show that high levels of TACC3 lead to the accumulation of DNA double-strand breaks (DSBs) and disrupt the normal cellular response to DNA damage, at least in part, by negatively regulating the expression of ataxia telangiectasia mutated (ATM) and the subsequent DNA damage response (DDR) signaling cascade. Cells expressing high levels of TACC3 display defective checkpoints and DSB-mediated homologous recombination (HR) and non-homologous end joining (NHEJ) repair systems, leading to genomic instability. Importantly, high levels of TACC3 confer cellular sensitization to radiation and poly(ADP-ribose) polymerase (PARP) inhibition. Overall, our findings provide critical information regarding the mechanisms by which TACC3 contributes to genomic instability, potentially leading to cancer development, and suggest a novel prognostic, diagnostic and therapeutic strategy for the treatment of cancer types expressing high levels of TACC3.
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24
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Molecular mechanisms of DNA replication checkpoint activation. Genes (Basel) 2014; 5:147-75. [PMID: 24705291 PMCID: PMC3978517 DOI: 10.3390/genes5010147] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 02/20/2014] [Accepted: 02/21/2014] [Indexed: 01/27/2023] Open
Abstract
The major challenge of the cell cycle is to deliver an intact, and fully duplicated, genetic material to the daughter cells. To this end, progression of DNA synthesis is monitored by a feedback mechanism known as replication checkpoint that is untimely linked to DNA replication. This signaling pathway ensures coordination of DNA synthesis with cell cycle progression. Failure to activate this checkpoint in response to perturbation of DNA synthesis (replication stress) results in forced cell division leading to chromosome fragmentation, aneuploidy, and genomic instability. In this review, we will describe current knowledge of the molecular determinants of the DNA replication checkpoint in eukaryotic cells and discuss a model of activation of this signaling pathway crucial for maintenance of genomic stability.
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25
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Carvalho JFS, Kanaar R. Targeting homologous recombination-mediated DNA repair in cancer. Expert Opin Ther Targets 2014; 18:427-58. [PMID: 24491188 DOI: 10.1517/14728222.2014.882900] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
INTRODUCTION DNA is the target of many traditional non-specific chemotherapeutic drugs. New drugs or therapeutic approaches with a more rational and targeted component are mandatory to improve the success of cancer therapy. The homologous recombination (HR) pathway is an attractive target for the development of inhibitors because cancer cells rely heavily on HR for repair of DNA double-strand breaks resulting from chemotherapeutic treatments. Additionally, the discovery that poly(ADP)ribose polymerase-1 inhibitors selectively kill cells with genetic defects in HR has spurned an even greater interest in inhibitors of HR. AREAS COVERED HR drives the repair of broken DNA via numerous protein-mediated sequential DNA manipulations. Due to extensive number of steps and proteins involved, the HR pathway provides a rich pool of potential drug targets. This review discusses the latest developments concerning the strategies being explored to inhibit HR. Particular attention is given to the identification of small molecule inhibitors of key HR proteins, including the BRCA proteins and RAD51. EXPERT OPINION Current HR inhibitors are providing the basis for pharmaceutical development of more potent and specific inhibitors to be applied in mono- or combinatorial therapy regimes, while novel targets will be uncovered by experiments aimed to gain a deeper mechanistic understanding of HR and its subpathways.
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Affiliation(s)
- João F S Carvalho
- Erasmus MC Cancer Institute, Department of Genetics, Department of Radiation Oncology, Cancer Genomics Netherlands , PO Box 2040, 3000 CA Rotterdam , The Netherlands
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26
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Banerjee P, deJesus R, Gjoerup O, Schaffhausen BS. Viral interference with DNA repair by targeting of the single-stranded DNA binding protein RPA. PLoS Pathog 2013; 9:e1003725. [PMID: 24204272 PMCID: PMC3812037 DOI: 10.1371/journal.ppat.1003725] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 09/09/2013] [Indexed: 11/18/2022] Open
Abstract
Correct repair of damaged DNA is critical for genomic integrity. Deficiencies in DNA repair are linked with human cancer. Here we report a novel mechanism by which a virus manipulates DNA damage responses. Infection with murine polyomavirus sensitizes cells to DNA damage by UV and etoposide. Polyomavirus large T antigen (LT) alone is sufficient to sensitize cells 100 fold to UV and other kinds of DNA damage. This results in activated stress responses and apoptosis. Genetic analysis shows that LT sensitizes via the binding of its origin-binding domain (OBD) to the single-stranded DNA binding protein replication protein A (RPA). Overexpression of RPA protects cells expressing OBD from damage, and knockdown of RPA mimics the LT phenotype. LT prevents recruitment of RPA to nuclear foci after DNA damage. This leads to failure to recruit repair proteins such as Rad51 or Rad9, explaining why LT prevents repair of double strand DNA breaks by homologous recombination. A targeted intervention directed at RPA based on this viral mechanism could be useful in circumventing the resistance of cancer cells to therapy.
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Affiliation(s)
- Pubali Banerjee
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Rowena deJesus
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Ole Gjoerup
- Molecular Oncology Research Institute, Tufts Medical Center, Boston, Massachusetts, United States of America
| | - Brian S. Schaffhausen
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- * E-mail:
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27
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A Relationship Between Replication Protein A and Occurrence and Prognosis of Esophageal Carcinoma. Cell Biochem Biophys 2013; 67:175-80. [DOI: 10.1007/s12013-013-9530-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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The natural absence of RPA1N domain did not impair Leishmania amazonensis RPA-1 participation in DNA damage response and telomere protection. Parasitology 2013; 140:547-59. [DOI: 10.1017/s0031182012002028] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
SUMMARYWe have previously shown that the subunit 1 of Leishmania amazonensis RPA (LaRPA-1) alone binds the G-rich telomeric strand and is structurally different from other RPA-1. It is analogous to telomere end-binding proteins described in model eukaryotes whose homologues were not identified in the protozoan´s genome. Here we show that LaRPA-1 is involved with damage response and telomere protection although it lacks the RPA1N domain involved with the binding with multiple checkpoint proteins. We induced DNA double-strand breaks (DSBs) in Leishmania using phleomycin. Damage was confirmed by TUNEL-positive nuclei and triggered a G1/S cell cycle arrest that was accompanied by nuclear accumulation of LaRPA-1 and RAD51 in the S phase of hydroxyurea-synchronized parasites. DSBs also increased the levels of RAD51 in non-synchronized parasites and of LaRPA-1 and RAD51 in the S phase of synchronized cells. More LaRPA-1 appeared immunoprecipitating telomeres in vivo and associated in a complex containing RAD51, although this interaction needs more investigation. RAD51 apparently co-localized with few telomeric clusters but it did not immunoprecipitate telomeric DNA. These findings suggest that LaRPA-1 and RAD51 work together in response to DNA DSBs and at telomeres, upon damage, LaRPA-1 works probably to prevent loss of single-stranded DNA and to assume a capping function.
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Namkoong S, Lee EJ, Jang IS, Park J. Elevated level of human RPA interacting protein α (hRIPα) in cervical tumor cells is involved in cell proliferation through regulating RPA transport. FEBS Lett 2012; 586:3753-60. [PMID: 23010595 DOI: 10.1016/j.febslet.2012.09.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 09/06/2012] [Accepted: 09/06/2012] [Indexed: 10/27/2022]
Abstract
Replication protein A (RPA) is a eukaryotic single-stranded DNA binding protein that is essential for DNA replication, repair, and recombination, and human RPA interacting protein α (hRIPα) is the nuclear transporter of RPA. Here, we report the regulatory role of hRIPα protein in cell proliferation. Western blot analysis revealed that the level of hRIPα was frequently elevated in cervical tumors tissues and hRIPα knockdown by siRNA inhibited cellular proliferation through deregulation of the cell cycle. In addition, overexpression of hRIPα resulted in increased clonogenicity. These results indicate that hRIPα is involved in cell proliferation through regulation of RPA transport.
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Affiliation(s)
- Sim Namkoong
- Division of Biological Science and Technology, Yonsei University, Wonju 220-100, Republic of Korea
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30
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Recolin B, Van der Laan S, Maiorano D. Role of replication protein A as sensor in activation of the S-phase checkpoint in Xenopus egg extracts. Nucleic Acids Res 2011; 40:3431-42. [PMID: 22187152 PMCID: PMC3333866 DOI: 10.1093/nar/gkr1241] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Uncoupling between DNA polymerases and helicase activities at replication forks, induced by diverse DNA lesions or replication inhibitors, generate long stretches of primed single-stranded DNA that is implicated in activation of the S-phase checkpoint. It is currently unclear whether nucleation of the essential replication factor RPA onto this substrate stimulates the ATR-dependent checkpoint response independently of its role in DNA synthesis. Using Xenopus egg extracts to investigate the role of RPA recruitment at uncoupled forks in checkpoint activation we have surprisingly found that in conditions in which DNA synthesis occurs, RPA accumulation at forks stalled by either replication stress or UV irradiation is dispensable for Chk1 phosphorylation. In contrast, when both replication fork uncoupling and RPA hyperloading are suppressed, Chk1 phosphorylation is inhibited. Moreover, we show that extracts containing reduced levels of RPA accumulate ssDNA and induce spontaneous, caffeine-sensitive, Chk1 phosphorylation in S-phase. These results strongly suggest that disturbance of enzymatic activities of replication forks, rather than RPA hyperloading at stalled forks, is a critical determinant of ATR activation.
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Affiliation(s)
- Bénédicte Recolin
- Genome Surveillance and Stability Laboratory, CNRS-UPR1142, Institute of Human Genetics, 141 rue de la Cardonille, Montpellier 34396 Cedex 5, France
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31
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Zhang Y, Rohde LH, Wu H. Involvement of nucleotide excision and mismatch repair mechanisms in double strand break repair. Curr Genomics 2011; 10:250-8. [PMID: 19949546 PMCID: PMC2709936 DOI: 10.2174/138920209788488544] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Revised: 03/28/2009] [Accepted: 03/30/2009] [Indexed: 11/25/2022] Open
Abstract
Living organisms are constantly threatened by environmental DNA-damaging agents, including UV and ionizing radiation (IR). Repair of various forms of DNA damage caused by IR is normally thought to follow lesion-specific repair pathways with distinct enzymatic machinery. DNA double strand break is one of the most serious kinds of damage induced by IR, which is repaired through double strand break (DSB) repair mechanisms, including homologous recombination (HR) and non-homologous end joining (NHEJ). However, recent studies have presented increasing evidence that various DNA repair pathways are not separated, but well interlinked. It has been suggested that non-DSB repair mechanisms, such as Nucleotide Excision Repair (NER), Mismatch Repair (MMR) and cell cycle regulation, are highly involved in DSB repairs. These findings revealed previously unrecognized roles of various non-DSB repair genes and indicated that a successful DSB repair requires both DSB repair mechanisms and non-DSB repair systems. One of our recent studies found that suppressed expression of non-DSB repair genes, such as XPA, RPA and MLH1, influenced the yield of IR induced micronuclei formation and/or chromosome aberrations, suggesting that these genes are highly involved in DSB repair and DSB-related cell cycle arrest, which reveals new roles for these gene products in the DNA repair network. In this review, we summarize current progress on the function of non-DSB repair-related proteins, especially those that participate in NER and MMR pathways, and their influence on DSB repair. In addition, we present our developing view that the DSB repair mechanisms are more complex and are regulated by not only the well known HR/NHEJ pathways, but also a systematically coordinated cellular network.
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Affiliation(s)
- Ye Zhang
- NASA Johnson Space Center, Houston, Texas 77058
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32
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Xu B, Sun Z, Liu Z, Guo H, Liu Q, Jiang H, Zou Y, Gong Y, Tischfield JA, Shao C. Replication stress induces micronuclei comprising of aggregated DNA double-strand breaks. PLoS One 2011; 6:e18618. [PMID: 21525980 PMCID: PMC3078113 DOI: 10.1371/journal.pone.0018618] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2010] [Accepted: 03/07/2011] [Indexed: 11/30/2022] Open
Abstract
Background Micronuclei (MN) in mammalian cells serve as a reliable biomarker of genomic instability and genotoxic exposure. Elevation of MN is commonly observed in cells bearing intrinsic genomic instability and in normal cells exposed to genotoxic agents. DNA double-strand breaks are marked by phosphorylation of H2AX at serine 139 (γ-H2AX). One subclass of MN contains massive and uniform γ-H2AX signals. This study tested whether this subclass of MN can be induced by replication stress. Principal Findings We observed that a large proportion of MN, from 20% to nearly 50%, showed uniform staining by antibodies against γ-H2AX, a marker of DNA double-strand breaks (DSBs). Such micronuclei were designated as MN-γ–H2AX (+). We showed that such MN can be induced by chemicals that are known to cause DNA replication stress and S phase arrest. Hydroxyurea, aphidicolin and thymidine could all significantly induce MN-γ–H2AX (+), which were formed during S phase and appeared to be derived from aggregation of DSBs. MN-γ–H2AX (−), MN that were devoid of uniform γ-H2AX signals, were induced to a lesser extent in terms of fold change. Paclitaxel, which inhibits the disassembly of microtubules, only induced MN-γ–H2AX (−). The frequency of MN-γ–H2AX (+), but not that of MN-γ–H2AX (−), was also significantly increased in cells that experience S phase prolongation due to depletion of cell cycle regulator CUL4B. Depletion of replication protein A1 (RPA1) by RNA interference resulted in an elevation of both MN-γ–H2AX (+) and MN-γ–H2AX (−). Conclusions/Significance A subclass of MN, MN-γ–H2AX (+), can be preferentially induced by replication stress. Classification of MN according to their γ-H2AX status may provide a more refined evaluation of intrinsic genomic instabilities and the various environmental genotoxicants.
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Affiliation(s)
- Bing Xu
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Zhaoliang Sun
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Zhaojian Liu
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Haiyang Guo
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Qiao Liu
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Haiyan Jiang
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Yongxin Zou
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Yaoqin Gong
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
| | - Jay A. Tischfield
- Department of Genetics, Rutgers University, Piscataway, New Jersey, United States of America
| | - Changshun Shao
- Key Laboratory of Experimental Teratology, Ministry of Education, and Institute of Molecular Medicine and Genetics, Shandong University School of Medicine, Jinan, Shandong, China
- Department of Genetics, Rutgers University, Piscataway, New Jersey, United States of America
- * E-mail:
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Gupta S, Sathishkumar S, Ahmed MM. Influence of cell cycle checkpoints and p53 function on the toxicity of temozolomide in human pancreatic cancer cells. Pancreatology 2010; 10:565-79. [PMID: 20980775 PMCID: PMC2992636 DOI: 10.1159/000317254] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2009] [Accepted: 06/06/2010] [Indexed: 12/11/2022]
Abstract
BACKGROUND Though an increased efficacy of carmustine and temozolomide (TMZ) has been demonstrated by inactivation of O(6)-methylguanine-DNA methyltransferase (MGMT) with O(6)-benzyl-guanine (BG) in human pancreatic tumors refractive to alkylating agents, the regulatory mechanisms have not been explored. METHODS The effects of TMZ and BG on apoptosis, cell growth, the mitotic index, cell cycle distribution, and protein expression were studied by TUNEL, cell counting, flow cytometry, and Western blot analysis, respectively. RESULTS The wt-p53 human pancreatic tumor cell line Capan-2 and p53-efficient mouse embryonic fibroblasts (MEFs) were more responsive to treatment with TMZ + BG than mutant p53 Capan-1 and p53-null MEFs. S phase delay with a subsequent G2/M arrest was observed in Capans in response to BG + TMZ. The G1-to-S transition delay in Capan-2 was associated with p53-dependent apoptosis and was distinctly different from the presumed mismatch repair (MMR) killing operative during the G2/M arrest. The effect of p53 on BG + TMZ toxicity was supported by a marked change in apoptosis when p53 function was restored/inactivated. There was an early induction of MMR proteins in p53-efficient lines. CONCLUSION p53 provokes a classic proapoptotic response by delaying G1-to-S progression, but it may also facilitate cell killing by enhancing MMR-related cell cycle arrest and cell death.
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Affiliation(s)
- Seema Gupta
- Department of Radiation Oncology, Miller School of Medicine, University of Miami, Miami, Fla., USA,Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, Fla., USA
| | | | - Mansoor M. Ahmed
- Department of Radiation Oncology, Miller School of Medicine, University of Miami, Miami, Fla., USA,Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, Fla., USA,*Mansoor M. Ahmed, PhD, Department of Radiation Oncology, 1475 NW 12th Ave (D-31) Miami, FL 33136 (USA), Tel. +1 305 243 5454, Fax +1 305 243 1854, E-Mail
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34
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Hass CS, Gakhar L, Wold MS. Functional characterization of a cancer causing mutation in human replication protein A. Mol Cancer Res 2010; 8:1017-26. [PMID: 20587534 DOI: 10.1158/1541-7786.mcr-10-0161] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Replication protein A (RPA) is the primary ssDNA-binding protein in eukaryotes. RPA is essential for DNA replication, repair, and recombination. Mutation of a conserved leucine residue to proline in the high-affinity DNA binding site of RPA (residue L221 in human RPA) has been shown to have defects in DNA repair and a high rate of chromosomal rearrangements in yeast. The homologous mutation in mice was found to be lethal when homozygous and to cause high rates of cancer when heterozygous. To understand the molecular defect causing these phenotypes, we created the homologous mutation in the human RPA1 gene (L221P) and analyzed its properties in cells and in vitro. RPA1(L221P) does not support cell cycle progression when it is the only form of RPA1 in HeLa cells. This phenotype is caused by defects in DNA replication and repair. No phenotype is observed when cells contain both wild-type and L221P forms of RPA1, indicating that L221P is not dominant. Recombinant L221P polypeptide forms a stable complex with the other subunits of RPA, indicating that the mutation does not destabilize the protein; however, the resulting complex has dramatically reduced ssDNA binding activity and cannot support SV40 DNA replication in vitro. These findings indicate that in mammals, the L221P mutation causes a defect in ssDNA binding and a nonfunctional protein complex. This suggests that haploinsufficiency of RPA causes an increase in the levels of DNA damage and in the incidence of cancer.
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Affiliation(s)
- Cathy S Hass
- Department of Biochemistry, Carver College of Medicine, University of Iowa, USA
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35
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Shuck SC, Turchi JJ. Targeted inhibition of Replication Protein A reveals cytotoxic activity, synergy with chemotherapeutic DNA-damaging agents, and insight into cellular function. Cancer Res 2010; 70:3189-98. [PMID: 20395205 DOI: 10.1158/0008-5472.can-09-3422] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Targeting uncontrolled cell proliferation and resistance to DNA-damaging chemotherapeutics with a single agent has significant potential in cancer treatment. Replication protein A (RPA), the eukaryotic ssDNA-binding protein, is essential for genomic maintenance and stability via roles in both DNA replication and repair. We have identified a novel small molecule that inhibits the in vitro and cellular ssDNA-binding activity of RPA, prevents cell cycle progression, induces cytotoxicity, and increases the efficacy of chemotherapeutic DNA-damaging agents. These results provide new insight into the mechanism of RPA-ssDNA interactions in chromosome maintenance and stability. This represents the first molecularly targeted eukaryotic DNA-binding inhibitor and reveals the utility of targeting a protein-DNA interaction as a therapeutic strategy for cancer treatment.
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Affiliation(s)
- Sarah C Shuck
- Departments of Medicine and Biochemistry, Indiana University School of Medicine, Indianapolis, Indiana, USA
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36
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Bouley J, Pionneau C, Varinot J, Biard D, Genestie C, Antoine M, Coulet F, Stern MH, Stoppa-Lyonnet D, Soubrier F. Proteomic analysis of BRCA1-depleted cell line reveals a putative role for replication protein A2 up-regulation in BRCA1
breast tumor development. Proteomics Clin Appl 2010; 4:489-98. [DOI: 10.1002/prca.200900107] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Revised: 11/16/2009] [Accepted: 11/17/2009] [Indexed: 12/24/2022]
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37
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Haring SJ, Humphreys TD, Wold MS. A naturally occurring human RPA subunit homolog does not support DNA replication or cell-cycle progression. Nucleic Acids Res 2009; 38:846-58. [PMID: 19942684 PMCID: PMC2817474 DOI: 10.1093/nar/gkp1062] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Replication Protein A (RPA) is a single-stranded DNA-binding protein essential for DNA replication, repair, recombination and cell-cycle regulation. A human homolog of the RPA2 subunit, called RPA4, was previously identified and shown to be expressed in colon mucosal and placental cells; however, the function of RPA4 was not determined. To examine the function of RPA4 in human cells, we carried out knockdown and replacement studies to determine whether RPA4 can substitute for RPA2 in the cell. Unlike RPA2, exogenous RPA4 expression did not support chromosomal DNA replication and lead to cell-cycle arrest in G2/M. In addition, RPA4 localized to sites of DNA repair and reduced γ-H2AX caused by RPA2 depletion. These studies suggest that RPA4 cannot support cell proliferation but can support processes that maintain the genomic integrity of the cell.
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Affiliation(s)
- Stuart J Haring
- Department of Biochemistry, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA
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38
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Casteel DE, Zhuang S, Zeng Y, Perrino FW, Boss GR, Goulian M, Pilz RB. A DNA polymerase-{alpha}{middle dot}primase cofactor with homology to replication protein A-32 regulates DNA replication in mammalian cells. J Biol Chem 2008; 284:5807-18. [PMID: 19119139 DOI: 10.1074/jbc.m807593200] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
alpha-Accessory factor (AAF) stimulates the activity of DNA polymerase-alpha.primase, the only enzyme known to initiate DNA replication in eukaryotic cells ( Goulian, M., Heard, C. J., and Grimm, S. L. (1990) J. Biol. Chem. 265, 13221-13230 ). We purified the AAF heterodimer composed of 44- and 132-kDa subunits from cultured cells and identified full-length cDNA clones using amino acid sequences from internal peptides. AAF-132 demonstrated no homologies to known proteins; AAF-44, however, is evolutionarily related to the 32-kDa subunit of replication protein A (RPA-32) and contains an oligonucleotide/oligosaccharide-binding (OB) fold domain similar to the OB fold domains of RPA involved in single-stranded DNA binding. Epitope-tagged versions of AAF-44 and -132 formed a complex in intact cells, and purified recombinant AAF-44 bound to single-stranded DNA and stimulated DNA primase activity only in the presence of AAF-132. Mutations in conserved residues within the OB fold of AAF-44 reduced DNA binding activity of the AAF-44.AAF-132 complex. Immunofluorescence staining of AAF-44 and AAF-132 in S phase-enriched HeLa cells demonstrated punctate nuclear staining, and AAF co-localized with proliferating cell nuclear antigen, a marker for replication foci containing DNA polymerase-alpha.primase and RPA. Small interfering RNA-mediated depletion of AAF-44 in tumor cell lines inhibited [methyl-(3)H]thymidine uptake into DNA but did not affect cell viability. We conclude that AAF shares structural and functional similarities with RPA-32 and regulates DNA replication, consistent with its ability to increase polymerase-alpha.primase template affinity and stimulate both DNA primase and polymerase-alpha activities in vitro.
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Affiliation(s)
- Darren E Casteel
- Department of Medicine and Cancer Center of the University of California, San Diego, La Jolla, California 92093, USA
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The basic cleft of RPA70N binds multiple checkpoint proteins, including RAD9, to regulate ATR signaling. Mol Cell Biol 2008; 28:7345-53. [PMID: 18936170 DOI: 10.1128/mcb.01079-08] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
ATR kinase activation requires the recruitment of the ATR-ATRIP and RAD9-HUS1-RAD1 (9-1-1) checkpoint complexes to sites of DNA damage or replication stress. Replication protein A (RPA) bound to single-stranded DNA is at least part of the molecular recognition element that recruits these checkpoint complexes. We have found that the basic cleft of the RPA70 N-terminal oligonucleotide-oligosaccharide fold (OB-fold) domain is a key determinant of checkpoint activation. This protein-protein interaction surface is able to bind several checkpoint proteins, including ATRIP, RAD9, and MRE11. RAD9 binding to RPA is mediated by an acidic peptide within the C-terminal RAD9 tail that has sequence similarity to the primary RPA-binding surface in the checkpoint recruitment domain (CRD) of ATRIP. Mutation of the RAD9 CRD impairs its localization to sites of DNA damage or replication stress without perturbing its ability to form the 9-1-1 complex or bind the ATR activator TopBP1. Disruption of the RAD9-RPA interaction also impairs ATR signaling to CHK1 and causes hypersensitivity to both DNA damage and replication stress. Thus, the basic cleft of the RPA70 N-terminal OB-fold domain binds multiple checkpoint proteins, including RAD9, to promote ATR signaling.
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40
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Haring SJ, Mason AC, Binz SK, Wold MS. Cellular functions of human RPA1. Multiple roles of domains in replication, repair, and checkpoints. J Biol Chem 2008; 283:19095-111. [PMID: 18469000 PMCID: PMC2441558 DOI: 10.1074/jbc.m800881200] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Revised: 05/05/2008] [Indexed: 11/06/2022] Open
Abstract
In eukaryotes, the single strand DNA (ssDNA)-binding protein, replication protein A (RPA), is essential for DNA replication, repair, and recombination. RPA is composed of the following three subunits: RPA1, RPA2, and RPA3. The RPA1 subunit contains four structurally related domains and is responsible for high affinity ssDNA binding. This study uses a depletion/replacement strategy in human cells to reveal the contributions of each domain to RPA cellular functions. Mutations that substantially decrease ssDNA binding activity do not necessarily disrupt cellular RPA function. Conversely, mutations that only slightly affect ssDNA binding can dramatically affect cellular function. The N terminus of RPA1 is not necessary for DNA replication in the cell; however, this region is important for the cellular response to DNA damage. Highly conserved aromatic residues in the high affinity ssDNA-binding domains are essential for DNA repair and cell cycle progression. Our findings suggest that as long as a threshold of RPA-ssDNA binding activity is met, DNA replication can occur and that an RPA activity separate from ssDNA binding is essential for function in DNA repair.
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Affiliation(s)
- Stuart J Haring
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
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41
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Richard DJ, Bolderson E, Cubeddu L, Wadsworth RIM, Savage K, Sharma GG, Nicolette ML, Tsvetanov S, McIlwraith MJ, Pandita RK, Takeda S, Hay RT, Gautier J, West SC, Paull TT, Pandita TK, White MF, Khanna KK. Single-stranded DNA-binding protein hSSB1 is critical for genomic stability. Nature 2008; 453:677-81. [PMID: 18449195 DOI: 10.1038/nature06883] [Citation(s) in RCA: 187] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Accepted: 03/03/2008] [Indexed: 12/30/2022]
Abstract
Single-strand DNA (ssDNA)-binding proteins (SSBs) are ubiquitous and essential for a wide variety of DNA metabolic processes, including DNA replication, recombination, DNA damage detection and repair. SSBs have multiple roles in binding and sequestering ssDNA, detecting DNA damage, stimulating nucleases, helicases and strand-exchange proteins, activating transcription and mediating protein-protein interactions. In eukaryotes, the major SSB, replication protein A (RPA), is a heterotrimer. Here we describe a second human SSB (hSSB1), with a domain organization closer to the archaeal SSB than to RPA. Ataxia telangiectasia mutated (ATM) kinase phosphorylates hSSB1 in response to DNA double-strand breaks (DSBs). This phosphorylation event is required for DNA damage-induced stabilization of hSSB1. Upon induction of DNA damage, hSSB1 accumulates in the nucleus and forms distinct foci independent of cell-cycle phase. These foci co-localize with other known repair proteins. In contrast to RPA, hSSB1 does not localize to replication foci in S-phase cells and hSSB1 deficiency does not influence S-phase progression. Depletion of hSSB1 abrogates the cellular response to DSBs, including activation of ATM and phosphorylation of ATM targets after ionizing radiation. Cells deficient in hSSB1 exhibit increased radiosensitivity, defective checkpoint activation and enhanced genomic instability coupled with a diminished capacity for DNA repair. These findings establish that hSSB1 influences diverse endpoints in the cellular DNA damage response.
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Affiliation(s)
- Derek J Richard
- Signal Transduction Laboratory, Queensland Institute of Medical Research, Brisbane, Queensland 4029, Australia
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Rimkus SA, Katzenberger RJ, Trinh AT, Dodson GE, Tibbetts RS, Wassarman DA. Mutations in String/CDC25 inhibit cell cycle re-entry and neurodegeneration in a Drosophila model of Ataxia telangiectasia. Genes Dev 2008; 22:1205-20. [PMID: 18408079 DOI: 10.1101/gad.1639608] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mutations in ATM (Ataxia telangiectasia mutated) result in Ataxia telangiectasia (A-T), a disorder characterized by progressive neurodegeneration. Despite advances in understanding how ATM signals cell cycle arrest, DNA repair, and apoptosis in response to DNA damage, it remains unclear why loss of ATM causes degeneration of post-mitotic neurons and why the neurological phenotype of ATM-null individuals varies in severity. To address these issues, we generated a Drosophila model of A-T. RNAi knockdown of ATM in the eye caused progressive degeneration of adult neurons in the absence of exogenously induced DNA damage. Heterozygous mutations in select genes modified the neurodegeneration phenotype, suggesting that genetic background underlies variable neurodegeneration in A-T. The neuroprotective activity of ATM may be negatively regulated by deacetylation since mutations in a protein deacetylase gene, RPD3, suppressed neurodegeneration, and a human homolog of RPD3, histone deacetylase 2, bound ATM and abrogated ATM activation in cell culture. Moreover, knockdown of ATM in post-mitotic neurons caused cell cycle re-entry, and heterozygous mutations in the cell cycle activator gene String/CDC25 inhibited cell cycle re-entry and neurodegeneration. Thus, we hypothesize that ATM performs a cell cycle checkpoint function to protect post-mitotic neurons from degeneration and that cell cycle re-entry causes neurodegeneration in A-T.
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Affiliation(s)
- Stacey A Rimkus
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA
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43
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Supreme EnLIGHTenment: damage recognition and signaling in the mammalian UV response. Mol Cell 2008; 29:279-90. [PMID: 18280234 DOI: 10.1016/j.molcel.2008.01.001] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Indexed: 12/21/2022]
Abstract
Like their prokaryotic counterparts, mammalian cells can sense light, especially in the ultraviolet (UV) range of the spectrum. After UV exposure, cells mount an elaborate response--called the UV response--that mimics physiological signaling responses except that it targets multiple pathways, thereby lacking the defined specificity of receptor-triggered signal transduction. Despite many years of research, it is still not fully clear how UV radiation is sensed and converted into the "language of cells"--signal reception and transduction. This review focuses on how photonic energy and its primary cellular products are sensed to elicit the UV response.
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Apoptosis induced by replication inhibitors in Chk1-depleted cells is dependent upon the helicase cofactor Cdc45. Cell Death Differ 2008; 15:889-98. [PMID: 18239674 DOI: 10.1038/cdd.2008.4] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Checkpoint kinase 1 (Chk1) responds to disruption of DNA replication to maintain the integrity of stalled forks, promote homologous recombination-mediated repair of replication fork lesions, and control inappropriate firing of replication origins. This response is essential for viability as replication inhibitors trigger apoptosis in S-phase cells depleted of Chk1. Given the complex network of cellular responses controlled by Chk1, our aim was to determine which of these protect cells from apoptosis following replication stress. Work with cell-free systems has shown that RPA-ssDNA complex forms following replication inhibition through the uncoupling of replication and helicase complexes. Here we show that replication protein A (RPA) foci form in cells treated with replication inhibitors and that the number of foci dramatically increases together with hyperphosphorylation of RPA34 in Chk1-depleted cells in advance of the induction of apoptosis. RPA foci, RPA34 hyperphosphorylation, and apoptosis were suppressed by siRNA-mediated knockdown of Cdc45, an essential replication helicase cofactor required for both the initiation and elongation steps of DNA replication. In contrast, loss of p21, a negative effector of origin firing, stimulates both the accumulation of RPA foci and apoptosis. Taken together, these results suggest that the loss of control of replication origin firing following Chk1 depletion triggers the accumulation of the RPA-ssDNA complex and apoptosis when replication is blocked.
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Zhao X, Qiu W, Kung J, Zhao X, Peng X, Yegappan M, Yen-Lieberman B, Hsi ED. Bortezomib induces caspase-dependent apoptosis in Hodgkin lymphoma cell lines and is associated with reduced c-FLIP expression: A gene expression profiling study with implications for potential combination therapies. Leuk Res 2008; 32:275-85. [PMID: 17659339 DOI: 10.1016/j.leukres.2007.05.024] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2005] [Revised: 05/10/2007] [Accepted: 05/19/2007] [Indexed: 01/09/2023]
Abstract
The Hodgkin cells and Reed-Sternberg cells (HRS) of classical Hodgkin lymphoma (CHL) are derived from germinal center B cells. The pathogenesis of CHL is unclear but constitutive activation of NFkappaB may contribute. Proteasome inhibition aimed at inhibiting NFkappaB has been shown to result in apoptosis in HRS cells. Here we investigated the effects of bortezomib, a proteasome inhibitor, in HRS cells with a combination of functional assays and gene expression profiling (GEP). Exposure of KMH2 and L428 cells to bortezomib resulted in inhibition of proliferation and induction of apoptosis. Gene expression analysis of KMH2 cells by oligonucleotide cDNA microarrays showed that a limited set of genes were differentially expressed involving several key cellular pathways including cell cycle and apoptosis. Among them, the caspase 8 inhibitor cFLIP was down-regulated and confirmed by Q-PCR. Given the evidence that cFLIP in HRS cells contribute to cells' insensitive to death receptor-mediated apoptosis, we combined bortezomib and TRAIL. This combination caused further down-regulation of cFLIP protein and increased apoptosis in CHL cells demonstrated by PARP p85 immunohistochemistry and immunoblotting. Such apoptotic effects were inhibited by caspase inhibitor z-VAD-FMK, confirming the pro-apoptotic effects of bortezomib and TRAIL are caspase-dependent. Bortezomib has no detectable effect on expression of TRAIL receptor DR4/DR5 in these two cell lines. Tissue microarray analysis of primary Hodgkin lymphomas displayed that 82% cases (95/116) expressed cFLIP in Reed-Sternberg cells. The discovery of apoptotic pathways that can be manipulated by proteasome inhibition provides rationale for the combination of bortezomib and agents such as TRAIL in CHL treatment.
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Grudic A, Jul-Larsen A, Haring SJ, Wold MS, Lønning PE, Bjerkvig R, Bøe SO. Replication protein A prevents accumulation of single-stranded telomeric DNA in cells that use alternative lengthening of telomeres. Nucleic Acids Res 2007; 35:7267-78. [PMID: 17959650 PMCID: PMC2175364 DOI: 10.1093/nar/gkm738] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The activation of a telomere maintenance mechanism is required for cancer development in humans. While most tumors achieve this by expressing the enzyme telomerase, a fraction (5–15%) employs a recombination-based mechanism termed alternative lengthening of telomeres (ALT). Here we show that loss of the single-stranded DNA-binding protein replication protein A (RPA) in human ALT cells, but not in telomerase-positive cells, causes increased exposure of single-stranded G-rich telomeric DNA, cell cycle arrest in G2/M phase, accumulation of single-stranded telomeric DNA within ALT-associated PML bodies (APBs), and formation of telomeric aggregates at the ends of metaphase chromosomes. This study demonstrates differences between ALT cells and telomerase-positive cells in the requirement for RPA in telomere processing and implicates the ALT mechanism in tumor cells as a possible therapeutic target.
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Affiliation(s)
- Amra Grudic
- Section of Oncology, Department of Medicine, Haukeland University Hospital
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47
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Anantha RW, Vassin VM, Borowiec JA. Sequential and synergistic modification of human RPA stimulates chromosomal DNA repair. J Biol Chem 2007; 282:35910-23. [PMID: 17928296 DOI: 10.1074/jbc.m704645200] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The activity of human replication protein A (RPA) in DNA replication and repair is regulated by phosphorylation of the middle RPA2 subunit. It has previously been shown that up to nine different N-terminal residues are modified in vivo and in response to genotoxic stress. Using a novel antibody against phospho-Ser(29), a moiety formed by cyclin-Cdk, we observed that RPA2 was phosphorylated during mitosis in nonstressed cells. Robust phosphorylation of Ser(29) was also seen in interphase cells following treatment with the DNA-damaging agent camptothecin, a rare example of stress stimulating the modification of a repair factor by cyclin-Cdk. RPA2 phosphorylation is regulated both in cis and trans. Cis-phosphorylation follows a preferred pathway. (That is, the initial modification of Ser(33) by ATR stimulates subsequent phosphorylation of Cdk sites Ser(23) and Ser(29)). These events then facilitate modification of Thr(21) and extreme N-terminal sites Ser(4) and Ser(8), probably by DNA-PK. Our data also indicate that the phosphorylation of one RPA molecule can influence the phosphorylation of other RPA molecules in trans. Cells in which endogenous RPA2 was "replaced" with a double S23A/S29A-RPA2 mutant were seen to have an abnormal cell cycle distribution both in normal and in stressed cells. Such cells also showed aberrant DNA damage-dependent RPA foci and had persistent staining of gammaH2AX following DNA damage. Our data indicate that RPA phosphorylation facilitates chromosomal DNA repair. We postulate that the RPA phosphorylation pattern provides a means to regulate the DNA repair pathway utilized.
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Affiliation(s)
- Rachel W Anantha
- Department of Biochemistry and New York University Cancer Institute, New York University School of Medicine, New York, New York 10016, USA
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48
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Sleeth KM, Sørensen CS, Issaeva N, Dziegielewski J, Bartek J, Helleday T. RPA mediates recombination repair during replication stress and is displaced from DNA by checkpoint signalling in human cells. J Mol Biol 2007; 373:38-47. [PMID: 17765923 DOI: 10.1016/j.jmb.2007.07.068] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Revised: 07/20/2007] [Accepted: 07/25/2007] [Indexed: 10/22/2022]
Abstract
The replication protein A (RPA) is involved in most, if not all, nuclear metabolism involving single-stranded DNA. Here, we show that RPA is involved in genome maintenance at stalled replication forks by the homologous recombination repair system in humans. Depletion of the RPA protein inhibited the formation of RAD51 nuclear foci after hydroxyurea-induced replication stalling leading to persistent unrepaired DNA double-strand breaks (DSBs). We demonstrate a direct role of RPA in homology directed recombination repair. We find that RPA is dispensable for checkpoint kinase 1 (Chk1) activation and that RPA directly binds RAD52 upon replication stress, suggesting a direct role in recombination repair. In addition we show that inhibition of Chk1 with UCN-01 decreases dissociation of RPA from the chromatin and inhibits association of RAD51 and RAD52 with DNA. Altogether, our data suggest a direct role of RPA in homologous recombination in assembly of the RAD51 and RAD52 proteins. Furthermore, our data suggest that replacement of RPA with the RAD51 and RAD52 proteins is affected by checkpoint signalling.
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Affiliation(s)
- Kate M Sleeth
- The Institute for Cancer Studies, University of Sheffield, Sheffield, UK
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49
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Liu JS, Kuo SR, Melendy T. DNA damage-induced RPA focalization is independent of gamma-H2AX and RPA hyper-phosphorylation. J Cell Biochem 2007; 99:1452-62. [PMID: 16927366 DOI: 10.1002/jcb.21066] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Replication protein A (RPA) is the major eukaryotic single stranded DNA binding protein that plays a central role in DNA replication, repair and recombination. Like many DNA repair proteins RPA is heavily phosphorylated (specifically on its 32 kDa subunit) in response to DNA damage. Phosphorylation of many repair proteins has been shown to be important for their recruitment to DNA damage-induced intra-nuclear foci. Further, phosphorylation of H2AX (gamma-H2AX) has been shown to be important for either the recruitment or stable retention of DNA repair proteins to these intra-nuclear foci. We address here the relationship between DNA damage-induced hyper-phosphorylation of RPA and its intra-nuclear focalization, and whether gamma-H2AX is required for RPA's presence at these foci. Using GFP-conjugated RPA, we demonstrate the formation of extraction-resistant RPA foci induced by DNA damage or stalled replication forks. The strong DNA damage-induced RPA foci appear after phosphorylated histone H2AX and Chk1, but earlier than the appearance of hyper-phosphorylated RPA. We demonstrate that while the functions of phosphoinositol-3-kinase-related protein kinases are essential for DNA damage-induced H2AX phosphorylation and RPA hyper-phosphorylation, they are dispensable for the induction of extraction-resistant RPA and RPA foci. Furthermore, in mouse cells genetically devoid of H2AX, DNA damage-induced extraction-resistant RPA appears with the same kinetics as in normal mouse cells. These results demonstrate that neither RPA hyper-phosphorylation nor H2AX are required for the formation in RPA intra-nuclear foci in response to DNA damage/replicational stress and are consistent with a role for RPA as a DNA damage sensor involved in the initial recognition of damaged DNA or blocked replication forks.
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Affiliation(s)
- Jen-Sing Liu
- Department of Microbiology, University at Buffalo, School of Medicine and Biomedical Sciences, Buffalo, New York 14214, USA
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50
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Rizzolio F, Sala C, Alboresi S, Bione S, Gilli S, Goegan M, Pramparo T, Zuffardi O, Toniolo D. Epigenetic control of the critical region for premature ovarian failure on autosomal genes translocated to the X chromosome: a hypothesis. Hum Genet 2007; 121:441-50. [PMID: 17265046 DOI: 10.1007/s00439-007-0329-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Accepted: 01/08/2007] [Indexed: 11/28/2022]
Abstract
Chromosomal rearrangements in Xq are frequently associated to premature ovarian failure (POF) and have contributed to define a POF "critical region" from Xq13.3 to Xq26. Search for X-linked genes responsible for the phenotype has been elusive as most rearrangements did not interrupt genes and many were mapped to gene deserts. We now report that ovary-expressed genes flanked autosomal breakpoints in four POF cases analyzed whose X chromosome breakpoints interrupted a gene poor region in Xq21, where no ovary-expressed candidate genes could be found. We also show that the global down regulation in the oocyte and up regulation in the ovary of X-linked genes compared to the autosomes is mainly due to genes in the POF "critical region". We thus propose that POF, in X;autosome balanced translocations, may not only be caused by haploinsufficiency, but also by a oocyte-specific position effect on autosomal genes, dependent on dosage compensation mechanisms operating on the active X chromosome in mammals.
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Affiliation(s)
- Flavio Rizzolio
- Department of Molecular Biology and Functional Genomics, San Raffaele Scientific Institute, Milan, Italy
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