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Mladenov E, Staudt C, Soni A, Murmann-Konda T, Siemann-Loekes M, Iliakis G. Strong suppression of gene conversion with increasing DNA double-strand break load delimited by 53BP1 and RAD52. Nucleic Acids Res 2020; 48:1905-1924. [PMID: 31832684 PMCID: PMC7038941 DOI: 10.1093/nar/gkz1167] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 10/30/2019] [Accepted: 12/11/2019] [Indexed: 02/06/2023] Open
Abstract
In vertebrates, genomic DNA double-strand breaks (DSBs) are removed by non-homologous end-joining processes: classical non-homologous end-joining (c-NHEJ) and alternative end-joining (alt-EJ); or by homology-dependent processes: gene-conversion (GC) and single-strand annealing (SSA). Surprisingly, these repair pathways are not real alternative options restoring genome integrity with equal efficiency, but show instead striking differences in speed, accuracy and cell-cycle-phase dependence. As a consequence, engagement of one pathway may be associated with processing-risks for the genome absent from another pathway. Characterization of engagement-parameters and their consequences is, therefore, essential for understanding effects on the genome of DSB-inducing agents, such as ionizing-radiation (IR). Here, by addressing pathway selection in G2-phase, we discover regulatory confinements in GC with consequences for SSA- and c-NHEJ-engagement. We show pronounced suppression of GC with increasing DSB-load that is not due to RAD51 availability and which is delimited but not defined by 53BP1 and RAD52. Strikingly, at low DSB-loads, GC repairs ∼50% of DSBs, whereas at high DSB-loads its contribution is undetectable. Notably, with increasing DSB-load and the associated suppression of GC, SSA gains ground, while alt-EJ is suppressed. These observations explain earlier, apparently contradictory results and advance our understanding of logic and mechanisms underpinning the wiring between DSB repair pathways.
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Affiliation(s)
- Emil Mladenov
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
| | - Christian Staudt
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
| | - Aashish Soni
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
| | - Tamara Murmann-Konda
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
| | - Maria Siemann-Loekes
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
| | - George Iliakis
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
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2
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Park I, Kwon MS, Paik S, Kim H, Lee HO, Choi E, Lee H. HDAC2/3 binding and deacetylation of BubR1 initiates spindle assembly checkpoint silencing. FEBS J 2017; 284:4035-4050. [DOI: 10.1111/febs.14286] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 08/11/2017] [Accepted: 10/02/2017] [Indexed: 02/06/2023]
Affiliation(s)
- Inai Park
- Department of Biological Sciences and Institute of Molecular Biology and Genetics; Seoul National University; South Korea
| | - Mi-Sun Kwon
- Department of Biological Sciences and Institute of Molecular Biology and Genetics; Seoul National University; South Korea
| | - Sangjin Paik
- Department of Biological Sciences and Institute of Molecular Biology and Genetics; Seoul National University; South Korea
| | - Hyeonjong Kim
- Department of Biological Sciences and Institute of Molecular Biology and Genetics; Seoul National University; South Korea
| | - Hae-Ock Lee
- Department of Biological Sciences and Institute of Molecular Biology and Genetics; Seoul National University; South Korea
| | - Eunhee Choi
- Department of Biological Sciences and Institute of Molecular Biology and Genetics; Seoul National University; South Korea
| | - Hyunsook Lee
- Department of Biological Sciences and Institute of Molecular Biology and Genetics; Seoul National University; South Korea
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3
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Do TV, Hirst J, Hyter S, Roby KF, Godwin AK. Aurora A kinase regulates non-homologous end-joining and poly(ADP-ribose) polymerase function in ovarian carcinoma cells. Oncotarget 2017; 8:50376-50392. [PMID: 28881569 PMCID: PMC5584138 DOI: 10.18632/oncotarget.18970] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 06/16/2017] [Indexed: 01/08/2023] Open
Abstract
Ovarian cancer is usually diagnosed at late stages when cancer has spread beyond the ovary and patients ultimately succumb to the development of drug-resistant disease. There is an urgent and unmet need to develop therapeutic strategies that effectively treat ovarian cancer and this requires a better understanding of signaling pathways important for ovarian cancer progression. Aurora A kinase (AURKA) plays an important role in ovarian cancer progression by mediating mitosis and chromosomal instability. In the current study, we investigated the role of AURKA in regulating the DNA damage response and DNA repair in ovarian carcinoma cells. We discovered that AURKA modulated the expression and activity of PARP, a crucial mediator of DNA repair that is a target of therapeutic interest for the treatment of ovarian and other cancers. Further, specific inhibition of AURKA activity with the small molecule inhibitor, alisertib, stimulated the non-homologous end-joining (NHEJ) repair pathway by elevating DNA-PKcs activity, a catalytic subunit required for double-strand break (DSB) repair, as well as decreased the expression of PARP and BRCA1/2, which are required for high-fidelity homologous recombination-based DNA repair. Further, AURKA inhibition stimulates error-prone NHEJ repair of DNA double-strand breaks with incompatible ends. Consistent with in vitro findings, alisertib treatment increased phosphorylated DNA-PKcs(pDNA-PKcsT2609) and decreased PARP levels in vivo. Collectively, these results reveal new non-mitotic functions for AURKA in the regulation of DNA repair, which may inform of new therapeutic targets and strategies for treating ovarian cancer.
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Affiliation(s)
- Thuy-Vy Do
- Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, USA
| | - Jeff Hirst
- Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, USA
| | - Stephen Hyter
- Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, USA
| | - Katherine F. Roby
- Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS, USA
- University of Kansas Cancer Center, Kansas City, KS, USA
| | - Andrew K. Godwin
- Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, USA
- University of Kansas Cancer Center, Kansas City, KS, USA
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4
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Huang F, Goyal N, Sullivan K, Hanamshet K, Patel M, Mazina OM, Wang CX, An WF, Spoonamore J, Metkar S, Emmitte KA, Cocklin S, Skorski T, Mazin AV. Targeting BRCA1- and BRCA2-deficient cells with RAD52 small molecule inhibitors. Nucleic Acids Res 2016; 44:4189-99. [PMID: 26873923 PMCID: PMC4872086 DOI: 10.1093/nar/gkw087] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 02/03/2016] [Indexed: 12/20/2022] Open
Abstract
RAD52 is a member of the homologous recombination (HR) pathway that is important for maintenance of genome integrity. While single RAD52 mutations show no significant phenotype in mammals, their combination with mutations in genes that cause hereditary breast cancer and ovarian cancer like BRCA1, BRCA2, PALB2 and RAD51C are lethal. Consequently, RAD52 may represent an important target for cancer therapy. In vitro, RAD52 has ssDNA annealing and DNA strand exchange activities. Here, to identify small molecule inhibitors of RAD52 we screened a 372,903-compound library using a fluorescence-quenching assay for ssDNA annealing activity of RAD52. The obtained 70 putative inhibitors were further characterized using biochemical and cell-based assays. As a result, we identified compounds that specifically inhibit the biochemical activities of RAD52, suppress growth of BRCA1- and BRCA2-deficient cells and inhibit RAD52-dependent single-strand annealing (SSA) in human cells. We will use these compounds for development of novel cancer therapy and as a probe to study mechanisms of DNA repair.
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Affiliation(s)
- Fei Huang
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Nadish Goyal
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Katherine Sullivan
- Department of Microbiology and Immunology, and Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA 10140, USA
| | - Kritika Hanamshet
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Mikir Patel
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Olga M Mazina
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Charles X Wang
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - W Frank An
- Broad Institute of Harvard and Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - James Spoonamore
- Broad Institute of Harvard and Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Shailesh Metkar
- Broad Institute of Harvard and Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Kyle A Emmitte
- Vanderbilt Specialized Chemistry Center for Accelerated Probe Development, Vanderbilt Center for Neuroscience Drug Discovery, Department of Pharmacology and Chemistry, Vanderbilt University, Nashville, TN 37232, USA
| | - Simon Cocklin
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Tomasz Skorski
- Department of Microbiology and Immunology, and Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA 10140, USA
| | - Alexander V Mazin
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
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5
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Moro L, Guaragnella N, Giannattasio S. Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells. J Vis Exp 2015:e52849. [PMID: 26327352 DOI: 10.3791/52849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Silencing of the tumor suppressor protein BRCA2 and its detection by conventional biochemical analyses represent a great technical challenge owing to the large size of the human BRCA2 protein (approximately 390 kDa). We report modifications of standard siRNA transfection and immunoblotting protocols to silence human BRCA2 and detect endogenous BRCA2 protein, respectively, in human epithelial cell lines. Key steps include a high siRNA to transfection reagent ratio and two subsequent rounds of siRNA transfection within the same experiment. Using these and other modifications to the standard protocol we consistently achieve more than 70% silencing of the human BRCA2 gene as judged by immunoblotting analysis with anti-BRCA2 antibodies. In addition, denaturation of the cell lysates at 55 °C instead of the conventional 70-100 °C and other technical optimizations of the immunoblotting procedure allow detection of intact BRCA2 protein even when very low amounts of starting material are available or when BRCA2 protein expression levels are very low. Efficient silencing of BRCA2 in human cells offers a valuable strategy to disrupt BRCA2 function in cells with intact BRCA2, including tumor cells, to examine new molecular pathways and cellular functions that may be affected by pathogenic BRCA2 mutations in tumors. Adaptation of this protocol for efficient silencing and analysis of other 'large' proteins like BRCA2 should be readily achievable.
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Affiliation(s)
- Loredana Moro
- Institute of Biomembranes and Bioenergetics, National Research Council;
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Wali N, Hosokawa K, Malik S, Saito H, Miyaguchi K, Imajoh-Ohmi S, Miki Y, Nakanishi A. Centrosomal BRCA2 is a target protein of membrane type-1 matrix metalloproteinase (MT1-MMP). Biochem Biophys Res Commun 2013; 443:1148-54. [PMID: 24384087 DOI: 10.1016/j.bbrc.2013.12.103] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 12/11/2013] [Indexed: 01/07/2023]
Abstract
BRCA2 localizes to centrosomes between G1 and prophase and is removed from the centrosomes during mitosis, but the underlying mechanism is not clear. Here we show that BRCA2 is cleaved into two fragments by membrane type-1 matrix metalloproteinase (MT1-MMP), and that knockdown of MT1-MMP prevents the removal of BRCA2 from centrosomes during metaphase. Mass spectrometry mapping revealed that the MT1-MMP cleavage site of human BRCA2 is between Asn-2135 and Leu-2136 ((2132)LSNN/LNVEGG(2141)), and the point mutation L2136D abrogated MT1-MMP cleavage. Our data demonstrate that MT1-MMP proteolysis of BRCA2 regulates the abundance of BRCA2 on centrosomes.
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Affiliation(s)
- Nadila Wali
- Department of Molecular Genetics, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Japan; Department of Obstetrics and Gynecology, Urumqi Friendship Hospital, Xinjiang, PR China
| | - Kana Hosokawa
- Department of Molecular Genetics, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Japan
| | - Sadiya Malik
- Department of Molecular Genetics, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Japan
| | - Hiroko Saito
- Department of Molecular Diagnosis, Cancer Institute, The Japanese Foundation of Cancer Research (JFCR), Japan
| | - Ken Miyaguchi
- Department of Molecular Genetics, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Japan
| | - Shinobu Imajoh-Ohmi
- Medical Proteomics Laboratory, The Institute of Medical Science, The University of Tokyo, Japan
| | - Yoshio Miki
- Department of Molecular Genetics, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Japan; Department of Molecular Diagnosis, Cancer Institute, The Japanese Foundation of Cancer Research (JFCR), Japan.
| | - Akira Nakanishi
- Department of Molecular Genetics, Medical Research Institute, Tokyo Medical and Dental University (TMDU), Japan
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7
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Wilkerson PM, Dedes KJ, Wetterskog D, Mackay A, Lambros MB, Mansour M, Frankum J, Lord CJ, Natrajan R, Ashworth A, Reis-Filho JS. Functional characterization of EMSY
gene amplification in human cancers. J Pathol 2011; 225:29-42. [DOI: 10.1002/path.2944] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 05/18/2011] [Accepted: 05/18/2011] [Indexed: 11/10/2022]
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8
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Misra S, Sharma S, Agarwal A, Khedkar SV, Tripathi MK, Mittal MK, Chaudhuri G. Cell cycle-dependent regulation of the bi-directional overlapping promoter of human BRCA2/ZAR2 genes in breast cancer cells. Mol Cancer 2010; 9:50. [PMID: 20202217 PMCID: PMC2842238 DOI: 10.1186/1476-4598-9-50] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Accepted: 03/04/2010] [Indexed: 01/23/2023] Open
Abstract
Background BRCA2 gene expression is tightly regulated during the cell cycle in human breast cells. The expression of BRCA2 gene is silenced at the G0/G1 phase of cell growth and is de-silenced at the S/G2 phase. While studying the activity of BRCA2 gene promoter in breast cancer cells, we discovered that this promoter has bi-directional activity and the product of the reverse activity (a ZAR1-like protein, we named ZAR2) silences the forward promoter at the G0/G1 phase of the cell. Standard techniques like cell synchronization by serum starvation, flow cytometry, N-terminal or C-terminal FLAG epitope-tagged protein expression, immunofluorescence confocal microscopy, dual luciferase assay for promoter evaluation, and chromatin immunoprecipitation assay were employed during this study. Results Human BRCA2 gene promoter is active in both the forward and the reverse orientations. This promoter is 8-20 fold more active in the reverse orientation than in the forward orientation when the cells are in the non-dividing stage (G0/G1). When the cells are in the dividing state (S/G2), the forward activity of the promoter is 5-8 folds higher than the reverse activity. The reverse activity transcribes the ZAR2 mRNA with 966 nt coding sequence which codes for a 321 amino acid protein. ZAR2 has two C4 type zinc fingers at the carboxyl terminus. In the G0/G1 growth phase ZAR2 is predominantly located inside the nucleus of the breast cells, binds to the BRCA2 promoter and inhibits the expression of BRCA2. In the dividing cells, ZAR2 is trapped in the cytoplasm. Conclusions BRCA2 gene promoter has bi-directional activity, expressing BRCA2 and a novel C4-type zinc finger containing transcription factor ZAR2. Subcellular location of ZAR2 and its expression from the reverse promoter of the BRCA2 gene are stringently regulated in a cell cycle dependent manner. ZAR2 binds to BRCA2/ZAR2 bi-directional promoter in vivo and is responsible, at least in part, for the silencing of BRCA2 gene expression in the G0/G1 phase in human breast cells.
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Affiliation(s)
- Smita Misra
- Division of Biomedical Sciences, Meharry Medical College, Nashville, TN 37208, USA
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9
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Abstract
BRCA2 is a tumor suppressor gene that when mutated confers an increased susceptibility to developing breast and prostate carcinoma. Besides its role in mediating DNA repair, new evidence suggests that BRCA2 may also play a role in suppressing cancer cell growth. Because altered interactions between neoplastic cells and the surrounding extracellular matrix (ECM) play a pivotal role in unchecked cancer cell proliferation and metastatic progression, we hypothesized that the ECM may have an effect in BRCA2 expression. By using normal and prostate carcinoma cell lines, we demonstrated that although normal cells transiently increase BRCA2 protein levels when adhering to the ECM protein collagen type I (COL1), carcinoma cells exhibit a significant reduction in BRCA2 protein. This aberrant effect is independent from de novo protein synthesis and results from COL1-beta(1) integrin signaling through phosphatidylinositol (PI) 3-kinase leading to BRCA2 ubiquitination and degradation in the proteasome. BRCA2 protein depletion after cancer cell adhesion to COL1 or in small RNA interference assays triggers new DNA synthesis, a trophic effect that is abrogated by recombinant BRCA2 expression. Blocking or inhibiting beta(1) integrin, PI 3-kinase, or proteasome activity all have a negative effect on COL1-mediated DNA synthesis in cancer cells. In normal cells, the transient increase in BRCA2 expression is independent from beta(1) integrin or PI 3-kinase and has no effect in cell proliferation. In summary, these results unravel a novel mechanism whereby prostate carcinoma cell proliferation is enhanced by the down-regulation of BRCA2 expression when interacting with COL1, a major component of the ECM at osseous metastatic sites.
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Affiliation(s)
- Loredana Moro
- Institute of Biomembranes and Bioenergetics, National Research Council (Consiglio Nazionale delle Ricerche), Via Amendola 165/A, Bari 70126, Italy.
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10
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Tripathi MK, Misra S, Khedkar SV, Hamilton N, Irvin-Wilson C, Sharan C, Sealy L, Chaudhuri G. Regulation of BRCA2 gene expression by the SLUG repressor protein in human breast cells. J Biol Chem 2005; 280:17163-71. [PMID: 15734731 PMCID: PMC3092429 DOI: 10.1074/jbc.m501375200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The expression of the breast cancer susceptibility protein BRCA2 is highly regulated in human breast, ovary, and pancreatic cells. BRCA2 is not expressed in the non-dividing cells, and expression is cell cycle stage-dependent and is elevated in the sporadic cancer cells. Mutational analysis of the upstream sequence of the human BRCA2 gene revealed an E2-box-containing silencer at the -701 to -921 position. The E2-box is essential for the cell-cycle stage-dependent activity of the silencer. We affinity-purified a 29-kDa silencer-binding protein (SBP) from the nuclear extracts of human breast cells BT-549 and MDA-MB-231. We explored whether the E2-box-binding repressor protein SLUG, which is of similar molecular size, is involved in the silencing process. Supershift assay with the purified SBP and anti-SLUG antibody revealed the identity of the SBP as SLUG. We found that silencer is inactive in the human breast cancer cells such as MDA-MB-468 and MCF-7 that do not express SLUG, further suggesting the involvement of SLUG in the BRCA2 gene silencing. Inducible expression of human SLUG in the dividing MDA-MB-468 cells reduced BRCA2 RNA levels with the activation of the silencer. Furthermore, small interfering RNA-mediated knockdown of SLUG mRNA in the BT-549 cells caused inhibition of the silencer function. Chromatin immunoprecipitation assays suggested that SLUG mediates its action by recruiting C-terminal-binding protein-1 (CtBP-1) and histone deacetylase-1 (HDAC-1) at the silencer E2-box. The general HDAC inhibitor, trichostatin A, inhibited the SLUG-mediated regulation of the silencer function. It thus appears that SLUG is a negative regulator for BRCA2 gene expression.
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MESH Headings
- Acetylation
- Alcohol Oxidoreductases
- BRCA2 Protein/biosynthesis
- BRCA2 Protein/genetics
- Base Sequence
- Blotting, Northern
- Blotting, Western
- Breast Neoplasms/genetics
- Breast Neoplasms/metabolism
- Breast Neoplasms/pathology
- Cell Line, Tumor
- Cell Nucleus/metabolism
- Chromatin Immunoprecipitation
- DNA/metabolism
- DNA Mutational Analysis
- DNA-Binding Proteins/metabolism
- Gene Expression Regulation, Neoplastic
- Gene Silencing
- Histone Deacetylases/metabolism
- Histones/chemistry
- Humans
- Models, Genetic
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Phosphoproteins/metabolism
- Promoter Regions, Genetic
- Protein Binding
- Protein Conformation
- Protein Structure, Tertiary
- RNA, Messenger/metabolism
- RNA, Small Interfering/metabolism
- Recombinant Proteins/chemistry
- Reverse Transcriptase Polymerase Chain Reaction
- Snail Family Transcription Factors
- Transcription Factors/metabolism
- Transfection
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Affiliation(s)
- Manish K. Tripathi
- Division of Cancer Biology, Department of Biomedical Sciences, Meharry Medical College, Vanderbilt University Medical Center, Nashville, Tennessee 37208
| | - Smita Misra
- Division of Cancer Biology, Department of Biomedical Sciences, Meharry Medical College, Vanderbilt University Medical Center, Nashville, Tennessee 37208
| | - Sheetal V. Khedkar
- Division of Cancer Biology, Department of Biomedical Sciences, Meharry Medical College, Vanderbilt University Medical Center, Nashville, Tennessee 37208
| | - Nalo Hamilton
- Division of Cancer Biology, Department of Biomedical Sciences, Meharry Medical College, Vanderbilt University Medical Center, Nashville, Tennessee 37208
| | - Charletha Irvin-Wilson
- Division of Cancer Biology, Department of Biomedical Sciences, Meharry Medical College, Vanderbilt University Medical Center, Nashville, Tennessee 37208
| | - Chakradhari Sharan
- Division of Cancer Biology, Department of Biomedical Sciences, Meharry Medical College, Vanderbilt University Medical Center, Nashville, Tennessee 37208
| | - Linda Sealy
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37208
| | - Gautam Chaudhuri
- Division of Cancer Biology, Department of Biomedical Sciences, Meharry Medical College, Vanderbilt University Medical Center, Nashville, Tennessee 37208
- To whom correspondence should be addressed: Div, of Cancer Biology, Dept. of Biomedical Sciences, Meharry Medical College, 1005 D. B. Todd, Jr. Blvd., Nashville, TN 37208. Tel.: 615-327-6499; Fax 615-327-5559;
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11
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Chen F, Medhurst AL, de Winter JP, Waisfisz Q, Rooimans MA, Oostra AB, Meyer S, Zhang KJ, Xia B, Pals G, Arwert F, Zwaan CM, Joenje H. Apparent absence of BRCA2 protein in a proportion of acute myeloid leukemia cell lines. Leukemia 2004; 18:1918-20. [PMID: 15356654 DOI: 10.1038/sj.leu.2403473] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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12
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Yan DH, Wen Y, Su LK, Xia W, Wang SC, Zhang S, Gan L, Lee DF, Spohn B, Frey JA, Hortobagyi GN, Hung MC. A delayed chemically induced tumorigenesis in Brca2 mutant mice. Oncogene 2004; 23:1896-901. [PMID: 14981540 DOI: 10.1038/sj.onc.1207314] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BRCA2 is a breast cancer susceptibility gene. Germline mutations of BRCA2 account for about 10-30% of familial breast cancer cases. Consistent with its tumor-suppressor activity, BRCA2 plays an important role in DNA repair. To assess the susceptibility of carriers of mutant BRCA2 to tumorigenesis induced by DNA-damaging carcinogens, we generated a Brca2 knockout mouse strain and studied its susceptibility to chemically induced tumorigenesis. Similar to previously reported Brca2 knockout mice, our Brca2-/- embryos die at E8.5-9.5, while the Brca2+/- mice are tumor-free and fertile. Unexpectedly, Brca2+/- mice developed tumors slower than did their wild-type littermates when treated with a potent carcinogen 7,12-dimethylbenz[a]anthracene (DMBA). In vitro experiments showed that Brca2+/- mouse cells and Capan-1 cells, a human pancreatic cancer cell line deficient of BRCA2, were more sensitive to DMBA-induced apoptosis, than were Brca2+/+ mouse cells and a derivative of Capan-1 cells that expressed exogenous wild-type BRCA2, respectively. Our results suggest that enhanced sensitivity of Brca2 mutant cells to DMBA-induced apoptosis at the dose of DMBA we used contributes to the delayed tumorigenesis of Brca2+/- animals. This suggestion may also provide a rational explanation for a previous unexpected finding that cigarette smoking appears to reduce the breast cancer risk of BRCA2 mutation carriers.
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Affiliation(s)
- Duen-Hwa Yan
- Department of Molecular and Cellular Oncology, The University of Texas, Houston, TX, USA
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13
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Vissac C, Lémery D, Le Corre L, Fustier P, Déchelotte P, Maurizis JC, Bignon YJ, Bernard-Gallon DJ. Presence of BRCA1 and BRCA2 proteins in human milk fat globules after delivery. Biochim Biophys Acta 2002; 1586:50-6. [PMID: 11781149 DOI: 10.1016/s0925-4439(01)00085-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We evaluated BRCA1 and BRCA2 oncosuppressor protein expression in 26 milk samples in women just after delivery. The quantification of BRCA1 and BRCA2 proteins was performed in isolated milk fat globules using an affinity chromatography strategy. The amounts of BRCA1 and BRCA2 proteins were found to be similar. We explained the presence of BRCA1 and BRCA2 proteins in human milk fat globules by the fact that they are formed by exocytosis of lipids from epithelial cells of the mammary gland and are enveloped by plasma membrane from the apical part of the milk-secreting cells. This raises the possibility that BRCA1 and BRCA2 proteins are a protective response to proliferation and play a possible role in newborn nutrition.
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Affiliation(s)
- Cécile Vissac
- Laboratoire d'Oncologie Moléculaire, Centre Jean Perrin, 63011 Clermont-Ferrand, France
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14
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Abstract
The BRCA2 tumor suppressor has been implicated in the maintenance of chromosomal stability through a function in DNA repair. In this report, we examine human and mouse cell lines containing different BRCA2 mutations for their ability to repair chromosomal breaks by homologous recombination. Using the I-SceI endonuclease to introduce a double-strand break at a specific chromosomal locus, we find that BRCA2 mutant cell lines are recombination deficient, such that homology-directed repair is reduced 6- to >100-fold, depending on the cell line. Thus, BRCA2 is essential for efficient homology-directed repair, presumably in conjunction with the Rad51 recombinase. We propose that impaired homology-directed repair caused by BRCA2 deficiency leads to chromosomal instability and, possibly, tumorigenesis, through lack of repair or misrepair of DNA damage.
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Affiliation(s)
- M E Moynahan
- Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
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15
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Abstract
The breast cancer predisposing genes BRCA1 and BRCA2 appear to be involved in DNA repair. In particular, the sensitivity of BRCA2-deficient mouse embryonic fibroblasts to ionizing radiation and the demonstrated interaction of the BRCA2 protein with Rad51, a major factor in recombinational repair, indicate that BRCA2 is important for double strand break repair. The human BRCA2-deficient human cell line Capan-1, whilst being sensitive to ionizing radiation, is also sensitive to the alkylating agent methymethanesulfonate. The major lesions induced by this agent are methylated bases which are removed primarily by the base excision repair (BER) pathway. We have investigated the efficiency of BER in Capan-1 cells by an in vitro assay in which plasmid substrates containing a single lesion are repaired by mammalian cell extracts. In comparison to the control cell lines BxPC-3, T24 and MCF7, Capan-1 cells exhibited a reduced rate of DNA ligation during both the single-nucleotide insertion and PCNA-dependent pathways of BER. The reduced rate of DNA ligation exhibited by Capan-1 cell extracts was complemented by addition of bacteriophage T4 DNA ligase or human DNA ligase III. BRCA2-mutant Capan-1 cells may possess reduced DNA ligase activity during BER.
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Affiliation(s)
- M Bogliolo
- Mutagenesis Laboratory, Istituto Nazionale Ricerca Cancro, Genova, Italy
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16
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Abstract
BRCA2 mutations predispose carriers mainly to breast cancer. The vast majority of BRCA2 mutations are predicted to result in a truncated protein product. The smallest known cancer-associated deletion removes from the C terminus only 224 of the 3,418 residues constituting BRCA2, suggesting that these terminal amino acids are crucial for BRCA2 function. A series of green fluorescent protein (GFP)-tagged BRCA2 deletion mutants revealed that nuclear localization depends on two nuclear localization signals that reside within the final 156 residues of BRCA2. Consistent with this observation, an endogenous truncated BRCA2 mutant (6174delT) was found to be cytoplasmic. Together, these studies provide a simple explanation for why the vast majority of BRCA2 mutants are nonfunctional: they do not translocate into the nucleus.
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Affiliation(s)
- B H Spain
- Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
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