451
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Abstract
The number of DNA polymerases identified in each organism has mushroomed in the past two decades. Most newly found DNA polymerases specialize in translesion synthesis and DNA repair instead of replication. Although intrinsic error rates are higher for translesion and repair polymerases than for replicative polymerases, the specialized polymerases increase genome stability and reduce tumorigenesis. Reflecting the numerous types of DNA lesions and variations of broken DNA ends, translesion and repair polymerases differ in structure, mechanism, and function. Here, we review the unique and general features of polymerases specialized in lesion bypass, as well as in gap-filling and end-joining synthesis.
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Affiliation(s)
- Wei Yang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA;
| | - Yang Gao
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA;
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452
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Double-stranded DNA break polarity skews repair pathway choice during intrachromosomal and interchromosomal recombination. Proc Natl Acad Sci U S A 2018; 115:2800-2805. [PMID: 29472448 DOI: 10.1073/pnas.1720962115] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Activation-induced cytidine deaminase (AID) inflicts DNA damage at Ig genes to initiate class switch recombination (CSR) and chromosomal translocations. However, the DNA lesions formed during these processes retain an element of randomness, and thus knowledge of the relationship between specific DNA lesions and AID-mediated processes remains incomplete. To identify necessary and sufficient DNA lesions in CSR, the Cas9 endonuclease and nickase variants were used to program DNA lesions at a greater degree of predictability than is achievable with conventional induction of CSR. Here we show that Cas9-mediated nicks separated by up to 250 nucleotides on opposite strands can mediate CSR. Staggered double-stranded breaks (DSBs) result in more end resection and junctional microhomology than blunt DSBs. Moreover, Myc-Igh chromosomal translocations, which are carried out primarily by alternative end joining (A-EJ), were preferentially induced by 5' DSBs. These data indicate that DSBs with 5' overhangs skew intrachromosomal and interchromosomal end-joining toward A-EJ. In addition to lending potential insight to AID-mediated phenomena, this work has broader carryover implications in DNA repair and lymphomagenesis.
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453
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Her J, Bunting SF. How cells ensure correct repair of DNA double-strand breaks. J Biol Chem 2018; 293:10502-10511. [PMID: 29414795 DOI: 10.1074/jbc.tm118.000371] [Citation(s) in RCA: 197] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
DNA double-strand breaks (DSBs) arise regularly in cells and when left unrepaired cause senescence or cell death. Homologous recombination (HR) and nonhomologous end-joining (NHEJ) are the two major DNA-repair pathways. Whereas HR allows faithful DSB repair and healthy cell growth, NHEJ has higher potential to contribute to mutations and malignancy. Many regulatory mechanisms influence which of these two pathways is used in DSB repair. These mechanisms depend on the cell cycle, post-translational modifications, and chromatin effects. Here, we summarize current research into these mechanisms, with a focus on mammalian cells, and also discuss repair by "alternative end-joining" and single-strand annealing.
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Affiliation(s)
- Joonyoung Her
- From the Department of Molecular Biology and Biochemistry, Rutgers, State University of New Jersey, Piscataway, New Jersey 08540
| | - Samuel F Bunting
- From the Department of Molecular Biology and Biochemistry, Rutgers, State University of New Jersey, Piscataway, New Jersey 08540
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454
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Pajic M, Froio D, Daly S, Doculara L, Millar E, Graham PH, Drury A, Steinmann A, de Bock CE, Boulghourjian A, Zaratzian A, Carroll S, Toohey J, O'Toole SA, Harris AL, Buffa FM, Gee HE, Hollway GE, Molloy TJ. miR-139-5p Modulates Radiotherapy Resistance in Breast Cancer by Repressing Multiple Gene Networks of DNA Repair and ROS Defense. Cancer Res 2018; 78:501-515. [PMID: 29180477 DOI: 10.1158/0008-5472.can-16-3105] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 05/12/2017] [Accepted: 11/02/2017] [Indexed: 11/16/2022]
Abstract
Radiotherapy is essential to the treatment of most solid tumors and acquired or innate resistance to this therapeutic modality is a major clinical problem. Here we show that miR-139-5p is a potent modulator of radiotherapy response in breast cancer via its regulation of genes involved in multiple DNA repair and reactive oxygen species defense pathways. Treatment of breast cancer cells with a miR-139-5p mimic strongly synergized with radiation both in vitro and in vivo, resulting in significantly increased oxidative stress, accumulation of unrepaired DNA damage, and induction of apoptosis. Several miR-139-5p target genes were also strongly predictive of outcome in radiotherapy-treated patients across multiple independent breast cancer cohorts. These prognostically relevant miR-139-5p target genes were used as companion biomarkers to identify radioresistant breast cancer xenografts highly amenable to sensitization by cotreatment with a miR-139-5p mimetic.Significance: The microRNA described in this study offers a potentially useful predictive biomarker of radiosensitivity in solid tumors and a generally applicable druggable target for tumor radiosensitization. Cancer Res; 78(2); 501-15. ©2017 AACR.
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Affiliation(s)
- Marina Pajic
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
- St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - Danielle Froio
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Sheridan Daly
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Louise Doculara
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Ewan Millar
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
- Department of Anatomical Pathology, South Eastern Area Laboratory Service (SEALS), St George Hospital, Sydney, New South Wales, Australia
- Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - Peter H Graham
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Alison Drury
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Angela Steinmann
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Charles E de Bock
- Laboratory for the Molecular Biology of Leukemia, Center for Human Genetics, KU Leuven and Center for the Biology of Disease, VIB, Leuven, Belgium
| | - Alice Boulghourjian
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Anaiis Zaratzian
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
| | - Susan Carroll
- The Chris O'Brien Lifehouse, Sydney, New South Wales, Australia
| | - Joanne Toohey
- The Chris O'Brien Lifehouse, Sydney, New South Wales, Australia
| | - Sandra A O'Toole
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
- Department of Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
- Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Adrian L Harris
- Growth Factor Group, Cancer Research UK, Molecular Oncology Laboratories, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford, United Kingdom
| | - Francesca M Buffa
- Growth Factor Group, Cancer Research UK, Molecular Oncology Laboratories, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford, United Kingdom
| | - Harriet E Gee
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
- The Chris O'Brien Lifehouse, Sydney, New South Wales, Australia
- Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Georgina E Hollway
- Cancer Research Division, The Kinghorn Cancer Centre/Garvan Institute of Medical Research, Sydney, New South Wales, Australia
- St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - Timothy J Molloy
- St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia.
- St Vincent's Centre for Applied Medical Research, Darlinghurst, New South Wales, Australia
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455
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Family A and B DNA Polymerases in Cancer: Opportunities for Therapeutic Interventions. BIOLOGY 2018; 7:biology7010005. [PMID: 29301327 PMCID: PMC5872031 DOI: 10.3390/biology7010005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 12/14/2017] [Accepted: 12/29/2017] [Indexed: 02/07/2023]
Abstract
DNA polymerases are essential for genome replication, DNA repair and translesion DNA synthesis (TLS). Broadly, these enzymes belong to two groups: replicative and non-replicative DNA polymerases. A considerable body of data suggests that both groups of DNA polymerases are associated with cancer. Many mutations in cancer cells are either the result of error-prone DNA synthesis by non-replicative polymerases, or the inability of replicative DNA polymerases to proofread mismatched nucleotides due to mutations in 3'-5' exonuclease activity. Moreover, non-replicative, TLS-capable DNA polymerases can negatively impact cancer treatment by synthesizing DNA past lesions generated from treatments such as cisplatin, oxaliplatin, etoposide, bleomycin, and radiotherapy. Hence, the inhibition of DNA polymerases in tumor cells has the potential to enhance treatment outcomes. Here, we review the association of DNA polymerases in cancer from the A and B families, which participate in lesion bypass, and conduct gene replication. We also discuss possible therapeutic interventions that could be used to maneuver the role of these enzymes in tumorigenesis.
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456
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Baird DM, Hendrickson EA. Telomeres and Chromosomal Translocations : There's a Ligase at the End of the Translocation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1044:89-112. [PMID: 29956293 DOI: 10.1007/978-981-13-0593-1_7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Chromosomal translocations are now well understood to not only constitute signature molecular markers for certain human cancers but often also to be causative in the genesis of that tumor. Despite the obvious importance of such events, the molecular mechanism of chromosomal translocations in human cells remains poorly understood. Part of the explanation for this dearth of knowledge is due to the complexity of the reaction and the need to archaeologically work backwards from the final product (a translocation) to the original unrearranged chromosomes to infer mechanism. Although not definitive, these studies have indicated that the aberrant usage of endogenous DNA repair pathways likely lies at the heart of the problem. An equally obfuscating aspect of this field, however, has also originated from the unfortunate species-specific differences that appear to exist in the relevant model systems that have been utilized to investigate this process. Specifically, yeast and murine systems (which are often used by basic science investigators) rely on different DNA repair pathways to promote chromosomal translocations than human somatic cells. In this chapter, we will review some of the basic concepts of chromosomal translocations and the DNA repair systems thought to be responsible for their genesis with an emphasis on underscoring the differences between other species and human cells. In addition, we will focus on a specific subset of translocations that involve the very end of a chromosome (a telomere). A better understanding of the relationship between DNA repair pathways and chromosomal translocations is guaranteed to lead to improved therapeutic treatments for cancer.
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Affiliation(s)
- Duncan M Baird
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, UK
| | - Eric A Hendrickson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota Medical School, Minneapolis, MN, USA.
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457
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Processing-Challenges Generated by Clusters of DNA Double-Strand Breaks Underpin Increased Effectiveness of High-LET Radiation and Chromothripsis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1044:149-168. [DOI: 10.1007/978-981-13-0593-1_10] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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458
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Laverty DJ, Greenberg MM. In Vitro Bypass of Thymidine Glycol by DNA Polymerase θ Forms Sequence-Dependent Frameshift Mutations. Biochemistry 2017; 56:6726-6733. [PMID: 29243925 PMCID: PMC5743609 DOI: 10.1021/acs.biochem.7b01093] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Unrepaired DNA lesions block replication and threaten genomic stability. Several specialized translesion polymerases, including polymerase θ (Pol θ), contribute to replicative bypass of these lesions. The role of Pol θ in double-strand break repair is well-understood, but its contribution to translesion synthesis is much less so. We describe the action of Pol θ on templates containing thymidine glycol (Tg), a major cytotoxic, oxidative DNA lesion that blocks DNA replication. Unrepaired Tg lesions are bypassed in human cells by specialized translesion polymerases by one of two distinct pathways: high-fidelity bypass by the combined action of Pol κ and Pol ζ or weakly mutagenic bypass by Pol θ. Here we report that in vitro bypass of Tg by Pol θ results in frameshift mutations (deletions) in a sequence-dependent fashion. Steady-state kinetic analysis indicated that one- and two-nucleotide deletions are formed 9- and 6-fold more efficiently, respectively, than correct, full-length bypass products. Sequencing of in vitro bypass products revealed that bypass preference decreased in the following order on a template where all three outcomes were possible: two-nucleotide deletion > correct bypass > one-nucleotide deletion. These results suggest that bypass of Tg by Pol θ results in mutations opposite the lesion, as well as frameshift mutations.
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Affiliation(s)
- Daniel J. Laverty
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| | - Marc M. Greenberg
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
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459
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Reczek CR, Shakya R, Miteva Y, Szabolcs M, Ludwig T, Baer R. The DNA resection protein CtIP promotes mammary tumorigenesis. Oncotarget 2017; 7:32172-83. [PMID: 27058754 PMCID: PMC5078005 DOI: 10.18632/oncotarget.8605] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 03/14/2016] [Indexed: 01/15/2023] Open
Abstract
Many DNA repair factors act to suppress tumor formation by preserving genomic stability. Similarly, the CtIP protein, which interacts with the BRCA1 tumor suppressor, is also thought to have tumor suppression activity. Through its role in DNA end resection, CtIP facilitates DNA double-strand break (DSB) repair by homologous recombination (DSBR-HR) and microhomology-mediated end joining (MMEJ). In addition, however, CtIP has also been implicated in the formation of aberrant chromosomal rearrangements in an MMEJ-dependent manner, an activity that could potentially promote tumor development by increasing genome instability. To clarify whether CtIP acts in vivo to suppress or promote tumorigenesis, we have examined its oncogenic potential in mouse models of human breast cancer. Surprisingly, mice heterozygous for a null Ctip allele did not display an increased susceptibility to tumor formation. Moreover, mammary-specific biallelic CtIP ablation did not elicit breast tumors in a manner reminiscent of BRCA1 loss. Instead, CtIP inactivation dramatically reduced the kinetics of mammary tumorigenesis in mice bearing mammary-specific lesions of the p53 gene. Thus, unlike other repair factors, CtIP is not a tumor suppressor, but has oncogenic properties that can promote tumorigenesis, consistent with its ability to facilitate MMEJ-dependent chromosomal instability. Consequently, inhibition of CtIP-mediated MMEJ may prove effective against tumor types, such as human breast cancer, that display MMEJ-dependent chromosomal rearrangements.
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Affiliation(s)
- Colleen R Reczek
- Institute for Cancer Genetics, Department of Pathology and Cell Biology, and Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, NY 10032, USA
| | - Reena Shakya
- Institute for Cancer Genetics, Department of Pathology and Cell Biology, and Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, NY 10032, USA.,Current address: Department of Molecular Virology, Immunology, and Medical Genetics, Ohio State University Wexner Medical Center and Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Yana Miteva
- Institute for Cancer Genetics, Department of Pathology and Cell Biology, and Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, NY 10032, USA
| | - Matthias Szabolcs
- Institute for Cancer Genetics, Department of Pathology and Cell Biology, and Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, NY 10032, USA
| | - Thomas Ludwig
- Institute for Cancer Genetics, Department of Pathology and Cell Biology, and Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, NY 10032, USA.,Current address: Department of Molecular Virology, Immunology, and Medical Genetics, Ohio State University Wexner Medical Center and Comprehensive Cancer Center, Columbus, OH 43210, USA
| | - Richard Baer
- Institute for Cancer Genetics, Department of Pathology and Cell Biology, and Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, NY 10032, USA
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460
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Pommier Y, O'Connor MJ, de Bono J. Laying a trap to kill cancer cells: PARP inhibitors and their mechanisms of action. Sci Transl Med 2017; 8:362ps17. [PMID: 27797957 DOI: 10.1126/scitranslmed.aaf9246] [Citation(s) in RCA: 485] [Impact Index Per Article: 69.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Poly(ADP-ribose) polymerase (PARP) inhibitors are the first DNA damage response targeted agents approved for cancer therapy. Here, we focus on their molecular mechanism of action by PARP "trapping" and what this means for both clinical monotherapy and combination with chemotherapeutic agents.
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Affiliation(s)
- Yves Pommier
- Laboratory of Molecular Pharmacology and Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Mark J O'Connor
- DNA Damage Response Biology, Oncology IMED, AstraZeneca, Hodgkin Building, B900 Chesterford Research Park, Little Chesterford, Cambridge CB10 1XL, U.K
| | - Johann de Bono
- Drug Development Unit, Institute of Cancer Research and Royal Marsden National Health Service Foundation Trust, London SM2 5PT, U.K
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461
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Association and prognostic significance of BRCA1/2-mutation status with neoantigen load, number of tumor-infiltrating lymphocytes and expression of PD-1/PD-L1 in high grade serous ovarian cancer. Oncotarget 2017; 7:13587-98. [PMID: 26871470 PMCID: PMC4924663 DOI: 10.18632/oncotarget.7277] [Citation(s) in RCA: 449] [Impact Index Per Article: 64.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 01/24/2016] [Indexed: 12/28/2022] Open
Abstract
Immune checkpoint inhibitors (e.g., anti-PD-1 and anti-PD-L1 antibodies) have demonstrated remarkable efficacy against hypermutated cancers such as melanomas and lung carcinomas. One explanation for this effect is that hypermutated lesions harbor more tumor-specific neoantigens that stimulate recruitment of an increased number of tumor-infiltrating lymphocytes (TILs), which is counterbalanced by overexpression of immune checkpoints such as PD-1 or PD-L1. Given that BRCA1/2-mutated high grade serous ovarian cancers (HGSOCs) exhibit a higher mutational load and a unique mutational signature with an elevated number of larger indels up to 50 bp, we hypothesized that they may also harbor more tumor-specific neoantigens, and, therefore, exhibit increased TILs and PD-1/PD-L1 expression. Here, we report significantly higher predicted neoantigens in BRCA1/2-mutated tumors compared to tumors without alterations in homologous recombination (HR) genes (HR-proficient tumors). Tumors with higher neoantigen load were associated with improved overall survival and higher expression of immune genes associated with tumor cytotoxicity such as genes of the TCR, the IFN-gamma and the TNFR pathways. Furthermore, immunohistochemistry studies demonstrated that BRCA1/2-mutated tumors exhibited significantly increased CD3+ and CD8+ TILs, as well as elevated expression of PD-1 and PD-L1 in tumor-associated immune cells compared to HR-proficient tumors. Survival analysis showed that both BRCA1/2-mutation status and number of TILs were independently associated with outcome. Of note, two distinct groups of HGSOCs, one with very poor prognosis (HR proficient with low number of TILs) and one with very good prognosis (BRCA1/2-mutated tumors with high number of TILs) were defined. These findings support a link between BRCA1/2-mutation status, immunogenicity and survival, and suggesting that BRCA1/2-mutated HGSOCs may be more sensitive to PD-1/PD-L1 inhibitors compared to HR-proficient HGSOCs.
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462
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Schimmel J, Kool H, van Schendel R, Tijsterman M. Mutational signatures of non-homologous and polymerase theta-mediated end-joining in embryonic stem cells. EMBO J 2017; 36:3634-3649. [PMID: 29079701 PMCID: PMC5730883 DOI: 10.15252/embj.201796948] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 09/05/2017] [Accepted: 09/29/2017] [Indexed: 12/11/2022] Open
Abstract
Cells employ potentially mutagenic DNA repair mechanisms to avoid the detrimental effects of chromosome breaks on cell survival. While classical non-homologous end-joining (cNHEJ) is largely error-free, alternative end-joining pathways have been described that are intrinsically mutagenic. Which end-joining mechanisms operate in germ and embryonic cells and thus contribute to heritable mutations found in congenital diseases is, however, still largely elusive. Here, we determined the genetic requirements for the repair of CRISPR/Cas9-induced chromosomal breaks of different configurations, and establish the mutational consequences. We find that cNHEJ and polymerase theta-mediated end-joining (TMEJ) act both parallel and redundant in mouse embryonic stem cells and account for virtually all end-joining activity. Surprisingly, mutagenic repair by polymerase theta (Pol θ, encoded by the Polq gene) is most prevalent for blunt double-strand breaks (DSBs), while cNHEJ dictates mutagenic repair of DSBs with protruding ends, in which the cNHEJ polymerases lambda and mu play minor roles. We conclude that cNHEJ-dependent repair of DSBs with protruding ends can explain de novo formation of tandem duplications in mammalian genomes.
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Affiliation(s)
- Joost Schimmel
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Hanneke Kool
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Robin van Schendel
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Marcel Tijsterman
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
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463
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Affiliation(s)
- Judith L Campbell
- Braun Laboratories, California Institute of Technology, Pasadena, California, USA
| | - Hongzhi Li
- City of Hope, Bioinformatics Department, Duarte, California, USA
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464
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Mateos-Gomez PA, Kent T, Deng SK, McDevitt S, Kashkina E, Hoang TM, Pomerantz RT, Sfeir A. The helicase domain of Polθ counteracts RPA to promote alt-NHEJ. Nat Struct Mol Biol 2017; 24:1116-1123. [PMID: 29058711 PMCID: PMC6047744 DOI: 10.1038/nsmb.3494] [Citation(s) in RCA: 111] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 09/22/2017] [Indexed: 12/15/2022]
Abstract
Mammalian polymerase theta (Polθ) is a multifunctional enzyme that promotes error-prone DNA repair by alternative nonhomologous end joining (alt-NHEJ). Here we present structure-function analyses that reveal that, in addition to the polymerase domain, Polθ-helicase activity plays a central role during double-strand break (DSB) repair. Our results show that the helicase domain promotes chromosomal translocations by alt-NHEJ in mouse embryonic stem cells and also suppresses CRISPR-Cas9- mediated gene targeting by homologous recombination (HR). In vitro assays demonstrate that Polθ-helicase activity facilitates the removal of RPA from resected DSBs to allow their annealing and subsequent joining by alt-NHEJ. Consistent with an antagonistic role for RPA during alt-NHEJ, inhibition of RPA1 enhances end joining and suppresses recombination. Taken together, our results reveal that the balance between HR and alt-NHEJ is controlled by opposing activities of Polθ and RPA, providing further insight into the regulation of repair-pathway choice in mammalian cells.
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Affiliation(s)
- Pedro A. Mateos-Gomez
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, USA
- Department of Cell Biology, New York University School of Medicine, New York, USA
| | - Tatiana Kent
- Temple University Lewis Katz School of Medicine, Philadelphia, USA
| | - Sarah K. Deng
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, USA
- Department of Cell Biology, New York University School of Medicine, New York, USA
| | - Shane McDevitt
- Temple University Lewis Katz School of Medicine, Philadelphia, USA
| | | | - Trung M. Hoang
- Temple University Lewis Katz School of Medicine, Philadelphia, USA
| | | | - Agnel Sfeir
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, USA
- Department of Cell Biology, New York University School of Medicine, New York, USA
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465
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Tanori M, Casciati A, Berardinelli F, Leonardi S, Pasquali E, Antonelli F, Tanno B, Giardullo P, Pannicelli A, Babini G, De Stefano I, Sgura A, Mancuso M, Saran A, Pazzaglia S. Synthetic lethal genetic interactions between Rad54 and PARP-1 in mouse development and oncogenesis. Oncotarget 2017; 8:100958-100974. [PMID: 29254138 PMCID: PMC5731848 DOI: 10.18632/oncotarget.10479] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 06/26/2016] [Indexed: 12/27/2022] Open
Abstract
Mutations in DNA repair pathways are frequent in human cancers. Hence, gaining insights into the interaction of DNA repair genes is key to development of novel tumor-specific treatment strategies. In this study, we tested the functional relationship in development and oncogenesis between the homologous recombination (HR) factor Rad54 and Parp-1, a nuclear enzyme that plays a multifunctional role in DNA damage signaling and repair. We introduced single or combined Rad54 and Parp-1 inactivating germline mutations in Ptc1 heterozygous mice, a well-characterized model of medulloblastoma, the most common malignant pediatric brain tumor. Our study reveals that combined inactivation of Rad54 and Parp-1 causes a marked growth delay culminating in perinatallethality, providing for the first time evidence of synthetic lethal interactions between Rad54 and Parp-1 in vivo. Although the double mutation hampered investigation of Rad54 and Parp-1 interactions in cerebellum tumorigenesis, insights were gained by showing accumulation of endogenous DNA damage and increased apoptotic rate in granule cell precursors (GCPs). A network-based approach to detect differential expression of DNA repair genes in the cerebellum revealed perturbation of p53 signaling in Rad54-/-/Parp-1-/-/Ptc1+/-, and MEFs from combined Rad54/Parp-1 mutants showed p53/p21-dependent typical senescent features. These findings help elucidate the genetic interplay between Rad54 and Parp-1 by suggesting that p53/p21-mediated apoptosis and/or senescence may be involved in synthetic lethal interactions occurring during development and inhibition of tumor growth.
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Affiliation(s)
- Mirella Tanori
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l’Energia e lo Sviluppo Economico Sostenibile (ENEA), CR-Casaccia, Rome, Italy
| | - Arianna Casciati
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l’Energia e lo Sviluppo Economico Sostenibile (ENEA), CR-Casaccia, Rome, Italy
| | | | - Simona Leonardi
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l’Energia e lo Sviluppo Economico Sostenibile (ENEA), CR-Casaccia, Rome, Italy
| | - Emanuela Pasquali
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l’Energia e lo Sviluppo Economico Sostenibile (ENEA), CR-Casaccia, Rome, Italy
| | - Francesca Antonelli
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l’Energia e lo Sviluppo Economico Sostenibile (ENEA), CR-Casaccia, Rome, Italy
| | - Barbara Tanno
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l’Energia e lo Sviluppo Economico Sostenibile (ENEA), CR-Casaccia, Rome, Italy
| | - Paola Giardullo
- Department of Science, University Roma Tre, Rome, Italy
- Department of Radiation Physics, Università degli Studi Guglielmo Marconi, Rome, Italy
| | | | | | - Ilaria De Stefano
- Department of Radiation Physics, Università degli Studi Guglielmo Marconi, Rome, Italy
| | | | - Mariateresa Mancuso
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l’Energia e lo Sviluppo Economico Sostenibile (ENEA), CR-Casaccia, Rome, Italy
| | - Anna Saran
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l’Energia e lo Sviluppo Economico Sostenibile (ENEA), CR-Casaccia, Rome, Italy
| | - Simonetta Pazzaglia
- Laboratory of Biomedical Technologies, Agenzia Nazionale per le Nuove Tecnologie, l’Energia e lo Sviluppo Economico Sostenibile (ENEA), CR-Casaccia, Rome, Italy
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466
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Hromas R, Kim HS, Sidhu G, Williamson E, Jaiswal A, Totterdale TA, Nole J, Lee SH, Nickoloff JA, Kong KY. The endonuclease EEPD1 mediates synthetic lethality in RAD52-depleted BRCA1 mutant breast cancer cells. Breast Cancer Res 2017; 19:122. [PMID: 29145865 PMCID: PMC5693420 DOI: 10.1186/s13058-017-0912-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Accepted: 10/30/2017] [Indexed: 02/06/2023] Open
Abstract
Background Proper repair and restart of stressed replication forks requires intact homologous recombination (HR). HR at stressed replication forks can be initiated by the 5′ endonuclease EEPD1, which cleaves the stalled replication fork. Inherited or acquired defects in HR, such as mutations in breast cancer susceptibility protein-1 (BRCA1) or BRCA2, predispose to cancer, including breast and ovarian cancers. In order for these HR-deficient tumor cells to proliferate, they become addicted to a bypass replication fork repair pathway mediated by radiation repair protein 52 (RAD52). Depleting RAD52 can cause synthetic lethality in BRCA1/2 mutant cancers by an unknown molecular mechanism. Methods We hypothesized that cleavage of stressed replication forks by EEPD1 generates a fork repair intermediate that is toxic when HR-deficient cells cannot complete repair with the RAD52 bypass pathway. To test this hypothesis, we applied cell survival assays, immunofluorescence staining, DNA fiber and western blot analyses to look at the correlation between cell survival and genome integrity in control, EEPD1, RAD52 and EEPD1/RAD52 co-depletion BRCA1-deficient breast cancer cells. Results Our data show that depletion of EEPD1 suppresses synthetic lethality, genome instability, mitotic catastrophe, and hypersensitivity to stress of replication of RAD52-depleted, BRCA1 mutant breast cancer cells. Without HR and the RAD52-dependent backup pathway, the BRCA1 mutant cancer cells depleted of EEPD1 skew to the alternative non-homologous end-joining DNA repair pathway for survival. Conclusion This study indicates that the mechanism of synthetic lethality in RAD52-depleted BRCA1 mutant cancer cells depends on the endonuclease EEPD1. The data imply that EEPD1 cleavage of stressed replication forks may result in a toxic intermediate when replication fork repair cannot be completed. Electronic supplementary material The online version of this article (doi:10.1186/s13058-017-0912-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Robert Hromas
- Department of Medicine and the Cancer Center, University of Florida Health, 1600 SW Archer Rd, Gainesville, FL, 32610, USA.
| | - Hyun-Suk Kim
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Gurjit Sidhu
- Department of Medicine and the Cancer Center, University of Florida Health, 1600 SW Archer Rd, Gainesville, FL, 32610, USA
| | - Elizabeth Williamson
- Department of Medicine and the Cancer Center, University of Florida Health, 1600 SW Archer Rd, Gainesville, FL, 32610, USA
| | - Aruna Jaiswal
- Department of Medicine and the Cancer Center, University of Florida Health, 1600 SW Archer Rd, Gainesville, FL, 32610, USA
| | - Taylor A Totterdale
- Department of Medicine and the Cancer Center, University of Florida Health, 1600 SW Archer Rd, Gainesville, FL, 32610, USA
| | - Jocelyn Nole
- Department of Medicine and the Cancer Center, University of Florida Health, 1600 SW Archer Rd, Gainesville, FL, 32610, USA
| | - Suk-Hee Lee
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Jac A Nickoloff
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, 80523, USA
| | - Kimi Y Kong
- Department of Medicine and the Cancer Center, University of Florida Health, 1600 SW Archer Rd, Gainesville, FL, 32610, USA.
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467
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Han J, Ruan C, Huen MSY, Wang J, Xie A, Fu C, Liu T, Huang J. BRCA2 antagonizes classical and alternative nonhomologous end-joining to prevent gross genomic instability. Nat Commun 2017; 8:1470. [PMID: 29133916 PMCID: PMC5684403 DOI: 10.1038/s41467-017-01759-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 10/13/2017] [Indexed: 12/27/2022] Open
Abstract
BRCA2-deficient cells exhibit gross genomic instability, but the underlying mechanisms are not fully understood. Here we report that inactivation of BRCA2 but not RAD51 destabilizes RPA-coated single-stranded DNA (ssDNA) structures at resected DNA double-strand breaks (DSBs) and greatly enhances the frequency of nuclear fragmentation following cell exposure to DNA damage. Importantly, these BRCA2-associated deficits are fueled by the aberrant activation of classical (c)- and alternative (alt)- nonhomologous end-joining (NHEJ), and rely on the well-defined DNA damage signaling pathway involving the pro-c-NHEJ factor 53BP1 and its downstream effector RIF1. We further show that the 53BP1–RIF1 axis promotes toxic end-joining events via the retention of Artemis at DNA damage sites. Accordingly, loss of 53BP1, RIF1, or Artemis prolongs the stability of RPA-coated DSB intermediates in BRCA2-deficient cells and restores nuclear integrity. We propose that BRCA2 antagonizes 53BP1, RIF1, and Artemis-dependent c-NHEJ and alt-NHEJ to prevent gross genomic instability in a RAD51-independent manner. The genomic instability phenotype characteristic of BRCA2-deficient cells is not fully mechanistically understood. Here the authors show BRCA2 inactivation destabilizes RPA-coated single-stranded DNA and leads to toxic non homologous end-joining events.
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Affiliation(s)
- Jinhua Han
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Chunyan Ruan
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Michael S Y Huen
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pok Fu Lam, Hong Kong, China
| | - Jiadong Wang
- Institute of Systems Biomedicine, Department of Radiation Medicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, China
| | - Anyong Xie
- Institute of Translational Medicine, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Chun Fu
- Department of Obstetrics and Gynecology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, 410011, China
| | - Ting Liu
- Department of Cell Biology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310058, China
| | - Jun Huang
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
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468
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Anomalies de la réparation de l’ADN et cancers gynécologiques. Bull Cancer 2017; 104:971-980. [DOI: 10.1016/j.bulcan.2017.09.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 09/21/2017] [Indexed: 11/17/2022]
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469
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FAN1 interaction with ubiquitylated PCNA alleviates replication stress and preserves genomic integrity independently of BRCA2. Nat Commun 2017; 8:1073. [PMID: 29051491 PMCID: PMC5648898 DOI: 10.1038/s41467-017-01074-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Accepted: 08/16/2017] [Indexed: 11/08/2022] Open
Abstract
Interstrand cross-link (ICL) hypersensitivity is a characteristic trait of Fanconi anemia (FA). Although FANCD2-associated nuclease 1 (FAN1) contributes to ICL repair, FAN1 mutations predispose to karyomegalic interstitial nephritis (KIN) and cancer rather than to FA. Thus, the biological role of FAN1 remains unclear. Because fork stalling in FAN1-deficient cells causes chromosomal instability, we reasoned that the key function of FAN1 might lie in the processing of halted replication forks. Here, we show that FAN1 contains a previously-uncharacterized PCNA interacting peptide (PIP) motif that, together with its ubiquitin-binding zinc finger (UBZ) domain, helps recruit FAN1 to ubiquitylated PCNA accumulated at stalled forks. This prevents replication fork collapse and controls their progression. Furthermore, we show that FAN1 preserves replication fork integrity by a mechanism that is distinct from BRCA2-dependent homologous recombination. Thus, targeting FAN1 activities and its interaction with ubiquitylated PCNA may offer therapeutic opportunities for treatment of BRCA-deficient tumors.
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470
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EZH2 promotes degradation of stalled replication forks by recruiting MUS81 through histone H3 trimethylation. Nat Cell Biol 2017; 19:1371-1378. [PMID: 29035360 DOI: 10.1038/ncb3626] [Citation(s) in RCA: 240] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 09/13/2017] [Indexed: 12/14/2022]
Abstract
The emergence of resistance to poly-ADP-ribose polymerase inhibitors (PARPi) poses a threat to the treatment of BRCA1 and BRCA2 (BRCA1/2)-deficient tumours. Stabilization of stalled DNA replication forks is a recently identified PARPi-resistance mechanism that promotes genomic stability in BRCA1/2-deficient cancers. Dissecting the molecular pathways controlling genomic stability at stalled forks is critical. Here we show that EZH2 localizes at stalled forks where it methylates Lys27 on histone 3 (H3K27me3), mediating recruitment of the MUS81 nuclease. Low EZH2 levels reduce H3K27 methylation, prevent MUS81 recruitment at stalled forks and cause fork stabilization. As a consequence, loss of function of the EZH2/MUS81 axis promotes PARPi resistance in BRCA2-deficient cells. Accordingly, low EZH2 or MUS81 expression levels predict chemoresistance and poor outcome in patients with BRCA2-mutated tumours. Moreover, inhibition of Ezh2 in a murine Brca2-/- breast tumour model is associated with acquired PARPi resistance. Our findings identify EZH2 as a critical regulator of genomic stability at stalled forks that couples histone modifications to nuclease recruitment. Our data identify EZH2 expression as a biomarker of BRCA2-deficient tumour response to chemotherapy.
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471
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Polak P, Kim J, Braunstein LZ, Tiao G, Karlic R, Rosebrock D, Livitz D, Kübler K, Mouw KW, Haradhvala NJ, Kamburov A, Maruvka YE, Leshchiner I, Lander ES, Golub T, Zick A, Orthwein A, Lawrence MS, Batra RN, Caldas C, Haber DA, Laird PW, Shen H, Ellisen LW, D’Andrea A, Chanock SJ, Foulkes WD, Getz G. A mutational signature reveals alterations underlying deficient homologous recombination repair in breast cancer. Nat Genet 2017; 49:1476-1486. [PMID: 28825726 PMCID: PMC7376751 DOI: 10.1038/ng.3934] [Citation(s) in RCA: 335] [Impact Index Per Article: 47.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 07/21/2017] [Indexed: 12/16/2022]
Abstract
Biallelic inactivation of BRCA1 or BRCA2 is associated with a pattern of genome-wide mutations known as signature 3. By analyzing ∼1,000 breast cancer samples, we confirmed this association and established that germline nonsense and frameshift variants in PALB2, but not in ATM or CHEK2, can also give rise to the same signature. We were able to accurately classify missense BRCA1 or BRCA2 variants known to impair homologous recombination (HR) on the basis of this signature. Finally, we show that epigenetic silencing of RAD51C and BRCA1 by promoter methylation is strongly associated with signature 3 and, in our data set, was highly enriched in basal-like breast cancers in young individuals of African descent.
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Affiliation(s)
- Paz Polak
- Broad Institute of MIT and Harvard, Cambridge, MA
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA
- Harvard Medical School, Boston, MA
| | - Jaegil Kim
- Broad Institute of MIT and Harvard, Cambridge, MA
| | - Lior Z. Braunstein
- Broad Institute of MIT and Harvard, Cambridge, MA
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY
| | - Grace Tiao
- Broad Institute of MIT and Harvard, Cambridge, MA
| | - Rosa Karlic
- Department of Molecular Biology, University of Zagreb, Zagreb, Croatia
| | | | | | - Kirsten Kübler
- Broad Institute of MIT and Harvard, Cambridge, MA
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA
- Harvard Medical School, Boston, MA
| | - Kent W. Mouw
- Harvard Medical School, Boston, MA
- Departments of Radiation Oncology, Brigham & Women’s Hospital and Dana-Farber Cancer Institute, Boston, MA
| | - Nicholas J. Haradhvala
- Broad Institute of MIT and Harvard, Cambridge, MA
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA
| | - Atanas Kamburov
- Broad Institute of MIT and Harvard, Cambridge, MA
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA
- Harvard Medical School, Boston, MA
| | - Yosef E. Maruvka
- Broad Institute of MIT and Harvard, Cambridge, MA
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA
- Harvard Medical School, Boston, MA
| | | | - Eric S. Lander
- Broad Institute of MIT and Harvard, Cambridge, MA
- Department of Biology, MIT, Cambridge, Massachusetts 02139, USA
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Todd Golub
- Broad Institute of MIT and Harvard, Cambridge, MA
- Harvard Medical School, Boston, MA
- Departments of Medical Oncology, Pathology, and Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA
| | - Aviad Zick
- Department of Oncology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | | | - Michael S. Lawrence
- Broad Institute of MIT and Harvard, Cambridge, MA
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA
- Harvard Medical School, Boston, MA
| | - Rajbir N. Batra
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, UK
- Cancer Research UK Cambridge Centre, Cambridge CB2 0RE, UK
- Department of Oncology, University of Cambridge Hutchison-MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge CB2 0XZ, UK
| | - Carlos Caldas
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, UK
- Cancer Research UK Cambridge Centre, Cambridge CB2 0RE, UK
- Department of Oncology, University of Cambridge Hutchison-MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge CB2 0XZ, UK
| | - Daniel A. Haber
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA
- Harvard Medical School, Boston, MA
| | | | - Hui Shen
- Van Andel Research Institute, Grand Rapids, MI
| | - Leif W. Ellisen
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA
- Harvard Medical School, Boston, MA
| | - Alan D’Andrea
- Center for DNA Damage and Repair, Dana-Farber Cancer Institute, Boston, MA
- Ludwig Center at Harvard, Boston, MA
| | - Stephen J. Chanock
- National Cancer Institute Division of Cancer Epidemiology and Genetics, 272131, Bethesda, Maryland, United States
| | - William D. Foulkes
- Department of Human Genetics, Lady Davis Institute for Medical Research and Research Institute McGill University Health Centre, McGill University, Montreal, QC, Canada
| | - Gad Getz
- Broad Institute of MIT and Harvard, Cambridge, MA
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA
- Harvard Medical School, Boston, MA
- Massachusetts General Hospital, Department of Pathology, Boston, Massachusetts 02114, USA
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472
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Kolb AL, Gunn AR, Lakin ND. Redundancy between nucleases required for homologous recombination promotes PARP inhibitor resistance in the eukaryotic model organism Dictyostelium. Nucleic Acids Res 2017; 45:10056-10067. [PMID: 28973445 PMCID: PMC5622368 DOI: 10.1093/nar/gkx639] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 07/14/2017] [Indexed: 12/21/2022] Open
Abstract
ADP-ribosyltransferases promote repair of DNA single strand breaks and disruption of this pathway by Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) is toxic to cells with defects in homologous recombination (HR). Here, we show that this relationship is conserved in the simple eukaryote Dictyostelium and exploit this organism to define mechanisms that drive resistance of the HR-deficient cells to PARPi. Dictyostelium cells disrupted in exonuclease I, a critical factor for HR, are sensitive to PARPi. Deletion of exo1 prevents the accumulation of Rad51 in chromatin induced by PARPi, resulting in DNA damage being channelled through repair by non-homologous end-joining (NHEJ). Inactivation of NHEJ supresses the sensitivity of exo1− cells to PARPi, indicating this pathway drives synthetic lethality and that in its absence alternative repair mechanisms promote cell survival. This resistance is independent of alternate-NHEJ and is instead achieved by re-activation of HR. Moreover, inhibitors of Mre11 restore sensitivity of dnapkcs−exo1− cells to PARPi, indicating redundancy between nucleases that initiate HR can drive PARPi resistance. These data inform on mechanism of PARPi resistance in HR-deficient cells and present Dictyostelium as a convenient genetic model to characterize these pathways.
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Affiliation(s)
- Anna-Lena Kolb
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Alasdair R Gunn
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Nicholas D Lakin
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
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473
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Federico MB, Campodónico P, Paviolo NS, Gottifredi V. ACCIDENTAL DUPLICATION: Beyond interstrand crosslinks repair: Contribution of FANCD2 and other Fanconi Anemia proteins to the replication of DNA. Mutat Res 2017:S0027-5107(17)30167-7. [PMID: 28966006 DOI: 10.1016/j.mrfmmm.2017.09.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 09/24/2017] [Indexed: 11/30/2022]
Abstract
The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/ 10.1016/j.mrfmmm.2017.09.006. This duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.
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Affiliation(s)
- Maria B Federico
- Cell Cycle and Genomic Stability Laboratory, Fundación Instituto Leloir-Instituto de Investigaciones Bioquímicas de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina
| | - Paola Campodónico
- Cell Cycle and Genomic Stability Laboratory, Fundación Instituto Leloir-Instituto de Investigaciones Bioquímicas de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina
| | - Natalia S Paviolo
- Cell Cycle and Genomic Stability Laboratory, Fundación Instituto Leloir-Instituto de Investigaciones Bioquímicas de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina
| | - Vanesa Gottifredi
- Cell Cycle and Genomic Stability Laboratory, Fundación Instituto Leloir-Instituto de Investigaciones Bioquímicas de Buenos Aires-Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.
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474
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Vanderstichele A, Busschaert P, Olbrecht S, Lambrechts D, Vergote I. Genomic signatures as predictive biomarkers of homologous recombination deficiency in ovarian cancer. Eur J Cancer 2017; 86:5-14. [PMID: 28950147 DOI: 10.1016/j.ejca.2017.08.029] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 08/24/2017] [Indexed: 12/22/2022]
Abstract
DNA repair deficiency is a common hallmark of many cancers and is increasingly recognised as a target for cancer therapeutics. Selecting patients for these treatments requires a functional assessment of multiple redundant DNA repair pathways. With the advent of whole-genome sequencing of cancer genomes, it is increasingly recognised that multiple signatures of mutational and chromosomal alterations can be correlated with specific DNA repair defects. The clinical relevance of this approach is underlined by the use of poly-(ADP-ribose) polymerase inhibitors (PARPi) in homologous recombination (HR) deficient high-grade serous ovarian cancers. Beyond deleterious mutations in HR-related genes such as BRCA1/2, it is recognised that HR deficiency endows ovarian cancers with specific signatures of base substitutions and structural chromosomal variation. Multiple metrics quantifying loss-of-heterozygosity (LOH) events were proposed and implemented in trials with PARPi. However, it was shown that some of the HR-deficient cases, i.e. CDK12-mutated tumours, were not associated with high LOH-based scores, but with distinct patterns of genomic alterations such as tandem duplication. Therefore, more complex signatures of structural genomic variation were identified and quantified. Ultimately, optimal prediction models for treatments targeting DNA repair will need to integrate multiples of these genomic signatures and will also need to assess multiple resistance mechanisms such as genomic reversion events that partially or fully re-activate DNA repair.
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Affiliation(s)
- Adriaan Vanderstichele
- Department of Gynaecology and Obstetrics, University Hospitals Leuven, Belgium; Division of Gynaecological Oncology, Leuven Cancer Institute, KU Leuven, Leuven, Belgium.
| | - Pieter Busschaert
- Department of Gynaecology and Obstetrics, University Hospitals Leuven, Belgium; Division of Gynaecological Oncology, Leuven Cancer Institute, KU Leuven, Leuven, Belgium
| | - Siel Olbrecht
- Department of Gynaecology and Obstetrics, University Hospitals Leuven, Belgium; Division of Gynaecological Oncology, Leuven Cancer Institute, KU Leuven, Leuven, Belgium
| | - Diether Lambrechts
- Center for Cancer Biology, VIB, Leuven, Belgium; Laboratory for Translational Genetics, Department of Oncology, KU Leuven, Leuven, Belgium
| | - Ignace Vergote
- Department of Gynaecology and Obstetrics, University Hospitals Leuven, Belgium; Division of Gynaecological Oncology, Leuven Cancer Institute, KU Leuven, Leuven, Belgium
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475
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Patel DS, Misenko SM, Her J, Bunting SF. BLM helicase regulates DNA repair by counteracting RAD51 loading at DNA double-strand break sites. J Cell Biol 2017; 216:3521-3534. [PMID: 28912125 PMCID: PMC5674892 DOI: 10.1083/jcb.201703144] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 06/28/2017] [Accepted: 08/04/2017] [Indexed: 11/22/2022] Open
Abstract
The BLM gene product, BLM, is a RECQ helicase that is involved in DNA replication and repair of DNA double-strand breaks by the homologous recombination (HR) pathway. During HR, BLM has both pro- and anti-recombinogenic activities, either of which may contribute to maintenance of genomic integrity. We find that in cells expressing a mutant version of BRCA1, an essential HR factor, ablation of BLM rescues genomic integrity and cell survival in the presence of DNA double-strand breaks. Improved genomic integrity in these cells is linked to a substantial increase in the stability of RAD51 at DNA double-strand break sites and in the overall efficiency of HR. Ablation of BLM also rescues RAD51 foci and HR in cells lacking BRCA2 or XRCC2. These results indicate that the anti-recombinase activity of BLM is of general importance for normal retention of RAD51 at DNA break sites and regulation of HR.
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Affiliation(s)
- Dharm S Patel
- Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, Piscataway, NJ
| | - Sarah M Misenko
- Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, Piscataway, NJ
| | - Joonyoung Her
- Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, Piscataway, NJ
| | - Samuel F Bunting
- Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, Piscataway, NJ
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476
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Ventriglia J, Paciolla I, Pisano C, Cecere SC, Di Napoli M, Tambaro R, Califano D, Losito S, Scognamiglio G, Setola SV, Arenare L, Pignata S, Della Pepa C. Immunotherapy in ovarian, endometrial and cervical cancer: State of the art and future perspectives. Cancer Treat Rev 2017; 59:109-116. [DOI: 10.1016/j.ctrv.2017.07.008] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 07/21/2017] [Accepted: 07/23/2017] [Indexed: 12/14/2022]
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477
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Sabari JK, Lok BH, Laird JH, Poirier JT, Rudin CM. Unravelling the biology of SCLC: implications for therapy. Nat Rev Clin Oncol 2017; 14:549-561. [PMID: 28534531 PMCID: PMC5843484 DOI: 10.1038/nrclinonc.2017.71] [Citation(s) in RCA: 292] [Impact Index Per Article: 41.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Small-cell lung cancer (SCLC) is an aggressive malignancy associated with a poor prognosis. First-line treatment has remained unchanged for decades, and a paucity of effective treatment options exists for recurrent disease. Nonetheless, advances in our understanding of SCLC biology have led to the development of novel experimental therapies. Poly [ADP-ribose] polymerase (PARP) inhibitors have shown promise in preclinical models, and are under clinical investigation in combination with cytotoxic therapies and inhibitors of cell-cycle checkpoints.Preclinical data indicate that targeting of histone-lysine N-methyltransferase EZH2, a regulator of chromatin remodelling implicated in acquired therapeutic resistance, might augment and prolong chemotherapy responses. High expression of the inhibitory Notch ligand Delta-like protein 3 (DLL3) in most SCLCs has been linked to expression of Achaete-scute homologue 1 (ASCL1; also known as ASH-1), a key transcription factor driving SCLC oncogenesis; encouraging preclinical and clinical activity has been demonstrated for an anti-DLL3-antibody-drug conjugate. The immune microenvironment of SCLC seems to be distinct from that of other solid tumours, with few tumour-infiltrating lymphocytes and low levels of the immune-checkpoint protein programmed cell death 1 ligand 1 (PD-L1). Nonetheless, immunotherapy with immune-checkpoint inhibitors holds promise for patients with this disease, independent of PD-L1 status. Herein, we review the progress made in uncovering aspects of the biology of SCLC and its microenvironment that are defining new therapeutic strategies and offering renewed hope for patients.
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Affiliation(s)
- Joshua K Sabari
- Department of Medicine, Memorial Sloan Kettering Cancer Center
| | - Benjamin H Lok
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, 300 East 66th Street, New York, New York 10065, USA
| | - James H Laird
- New York University School of Medicine, 550 1st Avenue, New York, New York 10016, USA
| | - John T Poirier
- Department of Medicine, Memorial Sloan Kettering Cancer Center
- Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center
| | - Charles M Rudin
- Department of Medicine, Memorial Sloan Kettering Cancer Center
- Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center
- Weill Cornell Medical College, 1300 York Avenue, New York, New York 10065, USA
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478
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Yang Y, Gao Y, Mutter-Rottmayer L, Zlatanou A, Durando M, Ding W, Wyatt D, Ramsden D, Tanoue Y, Tateishi S, Vaziri C. DNA repair factor RAD18 and DNA polymerase Polκ confer tolerance of oncogenic DNA replication stress. J Cell Biol 2017; 216:3097-3115. [PMID: 28835467 PMCID: PMC5626543 DOI: 10.1083/jcb.201702006] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 06/27/2017] [Accepted: 07/21/2017] [Indexed: 12/30/2022] Open
Abstract
The elevated CDK2 activity of oncogene-expressing cells induces DNA replication stress. Yang et al. show that the DNA repair protein RAD18 facilitates damage-tolerant DNA synthesis via the DNA polymerase κ in cells with aberrantly high CDK2 activity, suggesting an important new role for RAD18 in sustaining neoplastic cell survival. The mechanisms by which neoplastic cells tolerate oncogene-induced DNA replication stress are poorly understood. Cyclin-dependent kinase 2 (CDK2) is a major mediator of oncogenic DNA replication stress. In this study, we show that CDK2-inducing stimuli (including Cyclin E overexpression, oncogenic RAS, and WEE1 inhibition) activate the DNA repair protein RAD18. CDK2-induced RAD18 activation required initiation of DNA synthesis and was repressed by p53. RAD18 and its effector, DNA polymerase κ (Polκ), sustained ongoing DNA synthesis in cells harboring elevated CDK2 activity. RAD18-deficient cells aberrantly accumulated single-stranded DNA (ssDNA) after CDK2 activation. In RAD18-depleted cells, the G2/M checkpoint was necessary to prevent mitotic entry with persistent ssDNA. Rad18−/− and Polκ−/− cells were highly sensitive to the WEE1 inhibitor MK-1775 (which simultaneously activates CDK2 and abrogates the G2/M checkpoint). Collectively, our results show that the RAD18–Polκ signaling axis allows tolerance of CDK2-mediated oncogenic stress and may allow neoplastic cells to breach tumorigenic barriers.
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Affiliation(s)
- Yang Yang
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Yanzhe Gao
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Liz Mutter-Rottmayer
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Anastasia Zlatanou
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Michael Durando
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Weimin Ding
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC.,Oncology Center, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - David Wyatt
- Lineberger Comprehensive Cancer Center, Curriculumin Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Dale Ramsden
- Lineberger Comprehensive Cancer Center, Curriculumin Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Yuki Tanoue
- Division of Cell Maintenance, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto, Japan
| | - Satoshi Tateishi
- Division of Cell Maintenance, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto, Japan
| | - Cyrus Vaziri
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC .,Lineberger Comprehensive Cancer Center, Curriculumin Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC
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479
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Bournique E, Dall'Osto M, Hoffmann JS, Bergoglio V. Role of specialized DNA polymerases in the limitation of replicative stress and DNA damage transmission. Mutat Res 2017; 808:62-73. [PMID: 28843435 DOI: 10.1016/j.mrfmmm.2017.08.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 08/08/2017] [Accepted: 08/09/2017] [Indexed: 01/31/2023]
Abstract
Replication stress is a strong and early driving force for genomic instability and tumor development. Beside replicative DNA polymerases, an emerging group of specialized DNA polymerases is involved in the technical assistance of the replication machinery in order to prevent replicative stress and its deleterious consequences. During S-phase, altered progression of the replication fork by endogenous or exogenous impediments induces replicative stress, causing cells to reach mitosis with genomic regions not fully duplicated. Recently, specific mechanisms to resolve replication intermediates during mitosis with the aim of limiting DNA damage transmission to daughter cells have been identified. In this review, we detail the two major actions of specialized DNA polymerases that limit DNA damage transmission: the prevention of replicative stress by non-B DNA replication and the recovery of stalled replication forks.
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Affiliation(s)
- Elodie Bournique
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037, Toulouse, France
| | - Marina Dall'Osto
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037, Toulouse, France
| | - Jean-Sébastien Hoffmann
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037, Toulouse, France
| | - Valérie Bergoglio
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037, Toulouse, France.
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480
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Abstract
Genetic abnormalities are present in all tumor types, although the frequency and type can vary. Chromosome abnormalities include highly aberrant structures, particularly chromothriptic chromosomes. The generation of massive sequencing data has illuminated the scope of the mutational burden in cancer genomes, identifying patterns of mutations (mutation signatures), which have the potential to shed light on the relatedness and etiologies of cancers and impact therapy response. Some mutation patterns are clearly attributable to disruptions in pathways that maintain genomic integrity. Here we review recent advances in our understanding of genetic changes occurring in cancers and the roles of genome maintenance pathways.
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Affiliation(s)
- Elizabeth M Kass
- Developmental Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Mary Ellen Moynahan
- Department of Medicine, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Maria Jasin
- Developmental Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
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481
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Dutta A, Eckelmann B, Adhikari S, Ahmed KM, Sengupta S, Pandey A, Hegde PM, Tsai MS, Tainer JA, Weinfeld M, Hegde ML, Mitra S. Microhomology-mediated end joining is activated in irradiated human cells due to phosphorylation-dependent formation of the XRCC1 repair complex. Nucleic Acids Res 2017; 45:2585-2599. [PMID: 27994036 PMCID: PMC5389627 DOI: 10.1093/nar/gkw1262] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 12/15/2016] [Indexed: 02/06/2023] Open
Abstract
Microhomology-mediated end joining (MMEJ), an error-prone pathway for DNA double-strand break (DSB) repair, is implicated in genomic rearrangement and oncogenic transformation; however, its contribution to repair of radiation-induced DSBs has not been characterized. We used recircularization of a linearized plasmid with 3΄-P-blocked termini, mimicking those at X-ray-induced strand breaks, to recapitulate DSB repair via MMEJ or nonhomologous end-joining (NHEJ). Sequence analysis of the circularized plasmids allowed measurement of relative activity of MMEJ versus NHEJ. While we predictably observed NHEJ to be the predominant pathway for DSB repair in our assay, MMEJ was significantly enhanced in preirradiated cells, independent of their radiation-induced arrest in the G2/M phase. MMEJ activation was dependent on XRCC1 phosphorylation by casein kinase 2 (CK2), enhancing XRCC1's interaction with the end resection enzymes MRE11 and CtIP. Both endonuclease and exonuclease activities of MRE11 were required for MMEJ, as has been observed for homology-directed DSB repair (HDR). Furthermore, the XRCC1 co-immunoprecipitate complex (IP) displayed MMEJ activity in vitro, which was significantly elevated after irradiation. Our studies thus suggest that radiation-mediated enhancement of MMEJ in cells surviving radiation therapy may contribute to their radioresistance and could be therapeutically targeted.
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Affiliation(s)
- Arijit Dutta
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA.,Department of Biochemistry and Molecular Biology, University of Texas Medical Branch (UTMB), Galveston, TX 77555, USA
| | - Bradley Eckelmann
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA.,Texas A&M Health Science Center, College of Medicine, Bryan, TX 77807, USA
| | | | - Kazi Mokim Ahmed
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Shiladitya Sengupta
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA.,Weill Cornell Medical College, New York, NY 10065, USA
| | - Arvind Pandey
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Pavana M Hegde
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Miaw-Sheue Tsai
- Department of Cell and Molecular Biology, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA
| | - John A Tainer
- Department of Cell and Molecular Biology, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA.,Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Michael Weinfeld
- Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, Alberta T6G 1Z2, Canada
| | - Muralidhar L Hegde
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA.,Weill Cornell Medical College, New York, NY 10065, USA.,Houston Methodist Neurological Institute, Houston, TX 77030, USA
| | - Sankar Mitra
- Department of Radiation Oncology, Houston Methodist Research Institute, Houston, TX 77030, USA.,Department of Biochemistry and Molecular Biology, University of Texas Medical Branch (UTMB), Galveston, TX 77555, USA.,Texas A&M Health Science Center, College of Medicine, Bryan, TX 77807, USA.,Weill Cornell Medical College, New York, NY 10065, USA
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482
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Klemm T, Mannuß A, Kobbe D, Knoll A, Trapp O, Dorn A, Puchta H. The DNA translocase RAD5A acts independently of the other main DNA repair pathways, and requires both its ATPase and RING domain for activity in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 91:725-740. [PMID: 28509359 DOI: 10.1111/tpj.13602] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 04/27/2017] [Accepted: 05/09/2017] [Indexed: 06/07/2023]
Abstract
Multiple pathways exist to repair DNA damage induced by methylating and crosslinking agents in Arabidopsis thaliana. The SWI2/SNF2 translocase RAD5A, the functional homolog of budding yeast Rad5 that is required for the error-free branch of post-replicative repair, plays a surprisingly prominent role in the repair of both kinds of lesions in Arabidopsis. Here we show that both the ATPase domain and the ubiquitination function of the RING domain of the Arabidopsis protein are essential for the cellular response to different forms of DNA damage. To define the exact role of RAD5A within the complex network of DNA repair pathways, we crossed the rad5a mutant line with mutants of different known repair factors of Arabidopsis. We had previously shown that RAD5A acts independently of two main pathways of replication-associated DNA repair defined by the helicase RECQ4A and the endonuclease MUS81. The enhanced sensitivity of all double mutants tested in this study indicates that the repair of damaged DNA by RAD5A also occurs independently of nucleotide excision repair (AtRAD1), single-strand break repair (AtPARP1), as well as microhomology-mediated double-strand break repair (AtTEB). Moreover, RAD5A can partially complement for a deficient AtATM-mediated DNA damage response in plants, as the double mutant shows phenotypic growth defects.
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Affiliation(s)
- Tobias Klemm
- Botanical Institute, Karlsruhe Institute of Technology, Kaiserstr. 12, 76131, Karlsruhe, Germany
| | | | - Daniela Kobbe
- Botanical Institute, Karlsruhe Institute of Technology, Kaiserstr. 12, 76131, Karlsruhe, Germany
| | - Alexander Knoll
- Botanical Institute, Karlsruhe Institute of Technology, Kaiserstr. 12, 76131, Karlsruhe, Germany
| | | | - Annika Dorn
- Botanical Institute, Karlsruhe Institute of Technology, Kaiserstr. 12, 76131, Karlsruhe, Germany
| | - Holger Puchta
- Botanical Institute, Karlsruhe Institute of Technology, Kaiserstr. 12, 76131, Karlsruhe, Germany
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483
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González-Huici V, Wang B, Gartner A. A Role for the Nonsense-Mediated mRNA Decay Pathway in Maintaining Genome Stability in Caenorhabditis elegans. Genetics 2017; 206:1853-1864. [PMID: 28634159 PMCID: PMC5560793 DOI: 10.1534/genetics.117.203414] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 06/05/2017] [Indexed: 12/31/2022] Open
Abstract
Ionizing radiation (IR) is commonly used in cancer therapy and is a main source of DNA double-strand breaks (DSBs), one of the most toxic forms of DNA damage. We have used Caenorhabditis elegans as an invertebrate model to identify novel factors required for repair of DNA damage inflicted by IR. We have performed an unbiased genetic screen, finding that smg-1 mutations confer strong hyper-sensitivity to IR. SMG-1 is a phosphoinositide-3 kinase (PI3K) involved in mediating nonsense-mediated mRNA decay (NMD) of transcripts containing premature stop codons and related to the ATM and ATR kinases which are at the apex of DNA damage signaling pathways. Hyper-sensitivity to IR also occurs when other genes mediating NMD are mutated. The hyper-sensitivity to bleomycin, a drug known to induce DSBs, further supports that NMD pathway mutants are defective in DSB repair. Hyper-sensitivity was not observed upon treatment with alkylating agents or UV irradiation. We show that SMG-1 mainly acts in mitotically dividing germ cells, and during late embryonic and larval development. Based on epistasis experiments, SMG-1 does not appear to act in any of the three major pathways known to mend DNA DSBs, namely homologous recombination (HR), nonhomologous end-joining (NHEJ), and microhomology-mediated end-joining (MMEJ). We speculate that SMG-1 kinase activity could be activated following DNA damage to phosphorylate specific DNA repair proteins and/or that NMD inactivation may lead to aberrant mRNAs leading to synthesis of malfunctioning DNA repair proteins.
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Affiliation(s)
- Víctor González-Huici
- School of Life Sciences, Centre for Gene Regulation and Expression, University of Dundee, DD1 5EH, UK
| | - Bin Wang
- School of Life Sciences, Centre for Gene Regulation and Expression, University of Dundee, DD1 5EH, UK
| | - Anton Gartner
- School of Life Sciences, Centre for Gene Regulation and Expression, University of Dundee, DD1 5EH, UK
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484
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Nickoloff JA, Jones D, Lee SH, Williamson EA, Hromas R. Drugging the Cancers Addicted to DNA Repair. J Natl Cancer Inst 2017; 109:3832892. [PMID: 28521333 PMCID: PMC5436301 DOI: 10.1093/jnci/djx059] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 03/10/2017] [Indexed: 12/29/2022] Open
Abstract
Defects in DNA repair can result in oncogenic genomic instability. Cancers occurring from DNA repair defects were once thought to be limited to rare inherited mutations (such as BRCA1 or 2). It now appears that a clinically significant fraction of cancers have acquired DNA repair defects. DNA repair pathways operate in related networks, and cancers arising from loss of one DNA repair component typically become addicted to other repair pathways to survive and proliferate. Drug inhibition of the rescue repair pathway prevents the repair-deficient cancer cell from replicating, causing apoptosis (termed synthetic lethality). However, the selective pressure of inhibiting the rescue repair pathway can generate further mutations that confer resistance to the synthetic lethal drugs. Many such drugs currently in clinical use inhibit PARP1, a repair component to which cancers arising from inherited BRCA1 or 2 mutations become addicted. It is now clear that drugs inducing synthetic lethality may also be therapeutic in cancers with acquired DNA repair defects, which would markedly broaden their applicability beyond treatment of cancers with inherited DNA repair defects. Here we review how each DNA repair pathway can be attacked therapeutically and evaluate DNA repair components as potential drug targets to induce synthetic lethality. Clinical use of drugs targeting DNA repair will markedly increase when functional and genetic loss of repair components are consistently identified. In addition, future therapies will exploit artificial synthetic lethality, where complementary DNA repair pathways are targeted simultaneously in cancers without DNA repair defects.
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Affiliation(s)
- Jac A Nickoloff
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, USA
| | - Dennie Jones
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, FL, USA
| | - Suk-Hee Lee
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Elizabeth A Williamson
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, FL, USA
| | - Robert Hromas
- Department of Medicine and the Cancer Center, University of Florida Health, Gainesville, FL, USA
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485
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Yang L, Zhang Y, Shan W, Hu Z, Yuan J, Pi J, Wang Y, Fan L, Tang Z, Li C, Hu X, Tanyi JL, Fan Y, Huang Q, Montone K, Dang CV, Zhang L. Repression of BET activity sensitizes homologous recombination-proficient cancers to PARP inhibition. Sci Transl Med 2017; 9:eaal1645. [PMID: 28747513 PMCID: PMC5705017 DOI: 10.1126/scitranslmed.aal1645] [Citation(s) in RCA: 167] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 04/12/2017] [Accepted: 07/05/2017] [Indexed: 12/15/2022]
Abstract
Strategies to enhance response to poly(adenosine diphosphate-ribose) polymerase inhibitor (PARPi) in primary and acquired homologous recombination (HR)-proficient tumors would be a major advance in cancer care. We used a drug synergy screen that combined a PARPi, olaparib, with 20 well-characterized epigenetic drugs and identified bromodomain and extraterminal domain inhibitors (BETis; JQ1, I-BET762, and OTX015) as drugs that acted synergistically with olaparib in HR-proficient cancer cells. Functional assays demonstrated that repressed BET activity reduces HR and thus enhances PARPi-induced DNA damage in cancer cells. We also found that inhibition or depletion of BET proteins impairs transcription of BRCA1 and RAD51, two genes essential for HR. Moreover, BETi treatment sensitized tumors to PARP inhibition in preclinical animal models of HR-proficient breast and ovarian cancers. Finally, we showed that the BRD4 gene was focally amplified across 20 types of common cancers. Combination with BETi could greatly expand the utility of PARP inhibition to patients with HR-proficient cancer.
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Affiliation(s)
- Lu Yang
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Obstetrics and Gynecology, West China Medical School, Sichuan University, Chengdu 610041, China
| | - Youyou Zhang
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Weiwei Shan
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA
- Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, Obstetrics and Gynecology Hospital, Fudan University, Shanghai 200011, China
| | - Zhongyi Hu
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jiao Yuan
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jingjiang Pi
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Yueying Wang
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Lingling Fan
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA
- Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, Obstetrics and Gynecology Hospital, Fudan University, Shanghai 200011, China
| | - Zhaoqing Tang
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Chunsheng Li
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Obstetrics and Gynecology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Xiaowen Hu
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Obstetrics and Gynecology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Janos L Tanyi
- Department of Obstetrics and Gynecology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Yi Fan
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | - Kathleen Montone
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Chi V Dang
- Abramson Cancer Center, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Lin Zhang
- Center for Research on Reproduction and Women's Health, University of Pennsylvania, Philadelphia, PA 19104, USA.
- Department of Obstetrics and Gynecology, University of Pennsylvania, Philadelphia, PA 19104, USA
- Abramson Cancer Center, University of Pennsylvania, Philadelphia, PA 19104, USA
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486
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Mittempergher L. Genomic Characterization of High-Grade Serous Ovarian Cancer: Dissecting Its Molecular Heterogeneity as a Road Towards Effective Therapeutic Strategies. Curr Oncol Rep 2017; 18:44. [PMID: 27241520 DOI: 10.1007/s11912-016-0526-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
High-grade serous ovarian carcinoma (HGSOC) accounts for the majority of the ovarian cancer deaths, but over the last years little improvement in overall survival has been achieved. HGSOC is a molecularly and clinically heterogeneous disease. At genomic level, it represents a C-class malignancy having frequent gene losses (NF1, RB1, PTEN) and gains (CCNE1, MYC). HGSOC shows a simple mutational profile with TP53 nearly always mutated and with other genes mutated at low frequency. Importantly, 50 % of all HGSOCs have genetic features indicating a homologous recombination (HR) deficiency. HR deficient tumors are highly sensitive to PARP inhibitor anticancer agents, which exhibit synthetic lethality with a defective HR pathway. Transcriptionally, HGSOCs can be grouped into different molecular subtypes with distinct biology and prognosis. Molecular stratification of HGSOC based on these genomic features may result in improved therapeutic strategies.
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Affiliation(s)
- Lorenza Mittempergher
- Division of Molecular Carcinogenesis, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands.
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487
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Di Sante G, Di Rocco A, Pupo C, Casimiro MC, Pestell RG. Hormone-induced DNA damage response and repair mediated by cyclin D1 in breast and prostate cancer. Oncotarget 2017; 8:81803-81812. [PMID: 29137223 PMCID: PMC5669849 DOI: 10.18632/oncotarget.19413] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 06/26/2017] [Indexed: 11/25/2022] Open
Abstract
Cell cycle control proteins govern events that leads to the production of two identical daughter cells. Distinct sequential temporal phases, Gap 1 (G1), Gap 0 (G0), Synthesis (S), Gap 2 (G2) and Mitosis (M) are negotiated through a series of check points during which the favorability of the local cellular environment is assessed, prior to replicating DNA [1]. Cyclin D1 has been characterized as a key regulatory subunit of the holoenzyme that promotes the G1/S-phase transition through phosphorylating the pRB protein. Cyclin D1 overexpression is considered a driving force in several types of cancers and cdk inhibitors are being used effectively in the clinic for treatment of ERα+ breast cancer [1, 2]. Genomic DNA is assaulted by damaging ionizing radiation, chemical carcinogens, and reactive oxygen species (ROS) which are generated by cellular metabolism. Furthermore, specific hormones including estrogens [3, 4] and androgens [5] govern pathways that damage DNA. Defects in the DNA Damage Response (DDR) pathway can lead to genomic instability and cancer. Evidence is emerging that cyclin D1 bind proteins involved in DNA repair including BRCA1 [6], RAD51 [7], BRCA2 [8] and is involved in the DNA damage and DNA repair processes [7, 8]. Because the repair of damaged DNA appears to be an important and unexpected role for cyclin D1, and inhibitors of cyclin D1-dependent kinase activity are being used in the clinic, the latest findings on the role of cyclin D1 in mediating the DDR including the DDR induced by the hormones estrogen [9] and androgen [10, 11] is reviewed.
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Affiliation(s)
- Gabriele Di Sante
- Pennsylvania Cancer and Regenerative Medicine Research Center, Baruch S. Blumberg Institute, Pennsylvania Biotechnology Center, PA, USA
| | - Agnese Di Rocco
- Pennsylvania Cancer and Regenerative Medicine Research Center, Baruch S. Blumberg Institute, Pennsylvania Biotechnology Center, PA, USA
| | - Claudia Pupo
- Pennsylvania Cancer and Regenerative Medicine Research Center, Baruch S. Blumberg Institute, Pennsylvania Biotechnology Center, PA, USA
| | - Mathew C Casimiro
- Pennsylvania Cancer and Regenerative Medicine Research Center, Baruch S. Blumberg Institute, Pennsylvania Biotechnology Center, PA, USA
| | - Richard G Pestell
- Pennsylvania Cancer and Regenerative Medicine Research Center, Baruch S. Blumberg Institute, Pennsylvania Biotechnology Center, PA, USA.,Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore
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488
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Abstract
PURPOSE OF REVIEW The proven activity of poly ADP ribose polymerase (PARP) inhibitors in BRCA-mutated homologous recombination deficient (HRD) ovarian cancer has led to the availability to patients with ovarian cancer of the first targeted therapy with an associated predictive biomarker. Our focus has recently turned towards expanding the clinical utility of PARP inhibitors beyond BRCA mutated ovarian cancer, and to a search for novel targets within DNA damage response (DDR). RECENT FINDINGS Early trials in unselected patients with ovarian cancer showed responses to PARP inhibition in BRCA-wildtype ovarian cancer, and recent genomic studies have demonstrated that germline or somatic aberrations in other homologous recombination genes are present in a significant proportion of ovarian cancers. In addition, PARP inhibition may be of value in molecularly defined subsets of endometrial or cervical cancers. Novel DDR inhibitors such as ATR, ATM, WEE1 or DNA-PK inhibitors are also being tested in patients. Finally, combinatorial strategies of DDR inhibitors with antiangiogenic agents, phosphoinositide 3-kinase inhibitors or immunotherapies may further increase therapeutic efficacy. SUMMARY In the future, patients with gynaecological malignancies may be rationally selected for PARP inhibition on the basis of comprehensive evaluation of homologous recombination genomic alterations, or HRD assays. Furthermore, novel DDR inhibitors have the potential to expand the repertoire of therapeutic options available to these patients.
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489
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Lai X, Broderick R, Bergoglio V, Zimmer J, Badie S, Niedzwiedz W, Hoffmann JS, Tarsounas M. MUS81 nuclease activity is essential for replication stress tolerance and chromosome segregation in BRCA2-deficient cells. Nat Commun 2017; 8:15983. [PMID: 28714477 PMCID: PMC5520020 DOI: 10.1038/ncomms15983] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 05/17/2017] [Indexed: 11/28/2022] Open
Abstract
Failure to restart replication forks stalled at genomic regions that are difficult to replicate or contain endogenous DNA lesions is a hallmark of BRCA2 deficiency. The nucleolytic activity of MUS81 endonuclease is required for replication fork restart under replication stress elicited by exogenous treatments. Here we investigate whether MUS81 could similarly facilitate DNA replication in the context of BRCA2 abrogation. Our results demonstrate that replication fork progression in BRCA2-deficient cells requires MUS81. Failure to complete genome replication and defective checkpoint surveillance enables BRCA2-deficient cells to progress through mitosis with under-replicated DNA, which elicits severe chromosome interlinking in anaphase. MUS81 nucleolytic activity is required to activate compensatory DNA synthesis during mitosis and to resolve mitotic interlinks, thus facilitating chromosome segregation. We propose that MUS81 provides a mechanism of replication stress tolerance, which sustains survival of BRCA2-deficient cells and can be exploited therapeutically through development of specific inhibitors of MUS81 nuclease activity.
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Affiliation(s)
- Xianning Lai
- Genome Stability and Tumourigenesis Group, Department of Oncology, The CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, UK
| | - Ronan Broderick
- Division of Cancer Biology, Institute of Cancer Research, 123 Old Brompton Road, London SW7 3RP, UK
| | - Valérie Bergoglio
- Cancer Research Center of Toulouse, Université de Toulouse, Inserm, CNRS, UPS, Equipe labellisée Ligue Contre le Cancer, Laboratoire d’excellence Toulouse Cancer, 2 Avenue Hubert Curien, Toulouse 31037, France
| | - Jutta Zimmer
- Genome Stability and Tumourigenesis Group, Department of Oncology, The CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, UK
| | - Sophie Badie
- Genome Stability and Tumourigenesis Group, Department of Oncology, The CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, UK
| | - Wojciech Niedzwiedz
- Division of Cancer Biology, Institute of Cancer Research, 123 Old Brompton Road, London SW7 3RP, UK
| | - Jean-Sébastien Hoffmann
- Cancer Research Center of Toulouse, Université de Toulouse, Inserm, CNRS, UPS, Equipe labellisée Ligue Contre le Cancer, Laboratoire d’excellence Toulouse Cancer, 2 Avenue Hubert Curien, Toulouse 31037, France
| | - Madalena Tarsounas
- Genome Stability and Tumourigenesis Group, Department of Oncology, The CR-UK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, UK
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490
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Seol JH, Shim EY, Lee SE. Microhomology-mediated end joining: Good, bad and ugly. Mutat Res 2017; 809:81-87. [PMID: 28754468 DOI: 10.1016/j.mrfmmm.2017.07.002] [Citation(s) in RCA: 149] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 06/21/2017] [Accepted: 07/03/2017] [Indexed: 01/06/2023]
Abstract
DNA double-strand breaks (DSBs) are induced by a variety of genotoxic agents, including ionizing radiation and chemotherapy drugs for treating cancers. The elimination of DSBs proceeds via distinctive error-free and error-prone pathways. Repair by homologous recombination (HR) is largely error-free and mediated by RAD51/BRCA2 gene products. Classical non-homologous end joining (C-NHEJ) requires the Ku heterodimer and can efficiently rejoin breaks, with occasional loss or gain of DNA information. Recently, evidence has unveiled another DNA end-joining mechanism that is independent of recombination factors and Ku proteins, termed alternative non-homologous end joining (A-NHEJ). While A-NHEJ-mediated repair does not require homology, in a subtype of A-NHEJ, DSB breaks are sealed by microhomology (MH)-mediated base-pairing of DNA single strands, followed by nucleolytic trimming of DNA flaps, DNA gap filling, and DNA ligation, yielding products that are always associated with DNA deletion. This highly error-prone DSB repair pathway is termed microhomology-mediated end joining (MMEJ). Dissecting the mechanisms of MMEJ is of great interest because of its potential to destabilize the genome through gene deletions and chromosomal rearrangements in cells deficient in canonical repair pathways, including HR and C-NHEJ. In addition, evidence now suggests that MMEJ plays a physiological role in normal cells.
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Affiliation(s)
- Ja-Hwan Seol
- Department of Molecular Medicine, Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, United States
| | - Eun Yong Shim
- Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, United States
| | - Sang Eun Lee
- Department of Molecular Medicine, Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, United States; Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, United States.
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491
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Saito S, Maeda R, Adachi N. Dual loss of human POLQ and LIG4 abolishes random integration. Nat Commun 2017; 8:16112. [PMID: 28695890 PMCID: PMC5508229 DOI: 10.1038/ncomms16112] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 05/30/2017] [Indexed: 12/16/2022] Open
Abstract
Homologous recombination-mediated gene targeting has greatly contributed to genetic analysis in a wide range of species, but is highly inefficient in human cells because of overwhelmingly frequent random integration events, whose molecular mechanism remains elusive. Here we show that DNA polymerase θ, despite its minor role in chromosomal DNA repair, substantially contributes to random integration, and that cells lacking both DNA polymerase θ and DNA ligase IV, which is essential for non-homologous end joining (NHEJ), exhibit 100% efficiency of spontaneous gene targeting by virtue of undetectable levels of random integration. Thus, DNA polymerase θ-mediated end joining is the sole homology-independent repair route in the absence of NHEJ and, intriguingly, their combined absence reveals rare Alu-Alu recombination events utilizing a stretch of homology. Our findings provide new insights into the mechanics of foreign DNA integration and the role of DNA polymerase θ in human genome maintenance.
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Affiliation(s)
- Shinta Saito
- Department of Life and Environmental System Science, Graduate School of Nanobioscience, Yokohama City University, Yokohama 236-0027, Japan
| | - Ryo Maeda
- Department of Biology, Graduate School of Science, Chiba University, Chiba 263-8522, Japan
| | - Noritaka Adachi
- Department of Life and Environmental System Science, Graduate School of Nanobioscience, Yokohama City University, Yokohama 236-0027, Japan
- Advanced Medical Research Center, Yokohama City University, Yokohama 236-0004, Japan
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492
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Zelensky AN, Schimmel J, Kool H, Kanaar R, Tijsterman M. Inactivation of Pol θ and C-NHEJ eliminates off-target integration of exogenous DNA. Nat Commun 2017; 8:66. [PMID: 28687761 PMCID: PMC5501794 DOI: 10.1038/s41467-017-00124-3] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 06/01/2017] [Indexed: 11/09/2022] Open
Abstract
Off-target or random integration of exogenous DNA hampers precise genomic engineering and presents a safety risk in clinical gene therapy strategies. Genetic definition of random integration has been lacking for decades. Here, we show that the A-family DNA polymerase θ (Pol θ) promotes random integration, while canonical non-homologous DNA end joining plays a secondary role; cells double deficient for polymerase θ and canonical non-homologous DNA end joining are devoid of any integration events, demonstrating that these two mechanisms define random integration. In contrast, homologous recombination is not reduced in these cells and gene targeting is improved to 100% efficiency. Such complete reversal of integration outcome, from predominately random integration to exclusively gene targeting, provides a rational way forward to improve the efficacy and safety of DNA delivery and gene correction approaches.Random off-target integration events can impair precise gene targeting and poses a safety risk for gene therapy. Here the authors show that repression of polymerase θ and classical non-homologous recombination eliminates random integration.
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Affiliation(s)
- Alex N Zelensky
- Department of Molecular Genetics, Cancer Genomics Netherlands, Erasmus University Medical Centre, Rotterdam,, 3000 CA, The Netherlands
| | - Joost Schimmel
- Department of Human Genetics, Leiden University Medical Centre, PO Box 9600, Leiden,, 2300 RC, The Netherlands
| | - Hanneke Kool
- Department of Human Genetics, Leiden University Medical Centre, PO Box 9600, Leiden,, 2300 RC, The Netherlands
| | - Roland Kanaar
- Department of Molecular Genetics, Cancer Genomics Netherlands, Erasmus University Medical Centre, Rotterdam,, 3000 CA, The Netherlands.
| | - Marcel Tijsterman
- Department of Human Genetics, Leiden University Medical Centre, PO Box 9600, Leiden,, 2300 RC, The Netherlands.
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493
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Abstract
Cells are exposed to various endogenous and exogenous insults that induce DNA damage, which, if unrepaired, impairs genome integrity and leads to the development of various diseases, including cancer. Recent evidence has implicated poly(ADP-ribose) polymerase 1 (PARP1) in various DNA repair pathways and in the maintenance of genomic stability. The inhibition of PARP1 is therefore being exploited clinically for the treatment of various cancers, which include DNA repair-deficient ovarian, breast and prostate cancers. Understanding the role of PARP1 in maintaining genome integrity is not only important for the design of novel chemotherapeutic agents, but is also crucial for gaining insights into the mechanisms of chemoresistance in cancer cells. In this Review, we discuss the roles of PARP1 in mediating various aspects of DNA metabolism, such as single-strand break repair, nucleotide excision repair, double-strand break repair and the stabilization of replication forks, and in modulating chromatin structure.
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494
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Chatterjee N, Walker GC. Mechanisms of DNA damage, repair, and mutagenesis. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2017; 58:235-263. [PMID: 28485537 PMCID: PMC5474181 DOI: 10.1002/em.22087] [Citation(s) in RCA: 987] [Impact Index Per Article: 141.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 03/16/2017] [Indexed: 05/08/2023]
Abstract
Living organisms are continuously exposed to a myriad of DNA damaging agents that can impact health and modulate disease-states. However, robust DNA repair and damage-bypass mechanisms faithfully protect the DNA by either removing or tolerating the damage to ensure an overall survival. Deviations in this fine-tuning are known to destabilize cellular metabolic homeostasis, as exemplified in diverse cancers where disruption or deregulation of DNA repair pathways results in genome instability. Because routinely used biological, physical and chemical agents impact human health, testing their genotoxicity and regulating their use have become important. In this introductory review, we will delineate mechanisms of DNA damage and the counteracting repair/tolerance pathways to provide insights into the molecular basis of genotoxicity in cells that lays the foundation for subsequent articles in this issue. Environ. Mol. Mutagen. 58:235-263, 2017. © 2017 Wiley Periodicals, Inc.
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495
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Abstract
The correct duplication and transmission of genetic material to daughter cells is the primary objective of the cell division cycle. DNA replication and chromosome segregation present both challenges and opportunities for DNA repair pathways that safeguard genetic information. As a consequence, there is a profound, two-way connection between DNA repair and cell cycle control. Here, we review how DNA repair processes, and DNA double-strand break repair in particular, are regulated during the cell cycle to optimize genomic integrity.
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496
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Beagan K, Armstrong RL, Witsell A, Roy U, Renedo N, Baker AE, Schärer OD, McVey M. Drosophila DNA polymerase theta utilizes both helicase-like and polymerase domains during microhomology-mediated end joining and interstrand crosslink repair. PLoS Genet 2017; 13:e1006813. [PMID: 28542210 PMCID: PMC5466332 DOI: 10.1371/journal.pgen.1006813] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 06/09/2017] [Accepted: 05/12/2017] [Indexed: 11/20/2022] Open
Abstract
Double strand breaks (DSBs) and interstrand crosslinks (ICLs) are toxic DNA lesions that can be repaired through multiple pathways, some of which involve shared proteins. One of these proteins, DNA Polymerase θ (Pol θ), coordinates a mutagenic DSB repair pathway named microhomology-mediated end joining (MMEJ) and is also a critical component for bypass or repair of ICLs in several organisms. Pol θ contains both polymerase and helicase-like domains that are tethered by an unstructured central region. While the role of the polymerase domain in promoting MMEJ has been studied extensively both in vitro and in vivo, a function for the helicase-like domain, which possesses DNA-dependent ATPase activity, remains unclear. Here, we utilize genetic and biochemical analyses to examine the roles of the helicase-like and polymerase domains of Drosophila Pol θ. We demonstrate an absolute requirement for both polymerase and ATPase activities during ICL repair in vivo. However, similar to mammalian systems, polymerase activity, but not ATPase activity, is required for ionizing radiation-induced DSB repair. Using a site-specific break repair assay, we show that overall end-joining efficiency is not affected in ATPase-dead mutants, but there is a significant decrease in templated insertion events. In vitro, Pol θ can efficiently bypass a model unhooked nitrogen mustard crosslink and promote DNA synthesis following microhomology annealing, although ATPase activity is not required for these functions. Together, our data illustrate the functional importance of the helicase-like domain of Pol θ and suggest that its tethering to the polymerase domain is important for its multiple functions in DNA repair and damage tolerance. Error-prone DNA Polymerase θ (Pol θ) plays a conserved role in a mutagenic DNA double-strand break repair mechanism called microhomology-mediated end joining (MMEJ). In many organisms, it also participates in a process crucial to the removal/repair of DNA interstrand crosslinks. The exact mechanism by which Pol θ promotes these processes is unclear, but a clue may lie in its dual-domain structure. While the role of its polymerase domain has been well-studied, the function of its helicase-like domain remains an open question. Here we report an absolute requirement for ATPase activity of the helicase-like domain during interstrand crosslink repair in Drosophila melanogaster. We also find that although end joining frequency does not decrease in ATPase-dead mutants, ATPase activity is critical for generating templated insertions. Using purified Pol θ protein, we show that it can bypass synthetic substrates mimicking interstrand crosslink intermediates and can promote MMEJ-like reactions with partial double-stranded and single-stranded DNA. Together, these data demonstrate a novel function for the helicase-like domain of Pol θ in both interstrand crosslink repair and MMEJ and provide insight into why the dual-domain structure has been conserved throughout evolution.
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Affiliation(s)
- Kelly Beagan
- Department of Biology, Tufts University, Medford, Massachusetts
| | | | - Alice Witsell
- Department of Biology, Tufts University, Medford, Massachusetts
| | - Upasana Roy
- Department of Chemistry and Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York, United States of America
| | - Nikolai Renedo
- Department of Biology, Tufts University, Medford, Massachusetts
| | - Amy E. Baker
- Department of Biology, Tufts University, Medford, Massachusetts
| | - Orlando D. Schärer
- Department of Chemistry and Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York, United States of America
- Center for Genomic Integrity, Institute for Basic Science, Ulsan, Korea and Department of Biological Sciences, School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Korea
| | - Mitch McVey
- Department of Biology, Tufts University, Medford, Massachusetts
- * E-mail:
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497
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Malaby AW, Martin SK, Wood RD, Doublié S. Expression and Structural Analyses of Human DNA Polymerase θ (POLQ). Methods Enzymol 2017; 592:103-121. [PMID: 28668117 PMCID: PMC5624038 DOI: 10.1016/bs.mie.2017.03.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
DNA polymerase theta (pol θ) is an evolutionarily conserved protein encoded by the POLQ gene in mammalian genomes. Pol θ is the defining enzyme for a pathway of DSB repair termed "alternative end-joining" (altEJ) or "theta-mediated end-joining." This pathway contributes significantly to the radiation resistance of mammalian cells. It also modulates accuracy in repair of breaks that occur at stalled DNA replication forks, during diversification steps of the mammalian immune system, during repair of CRISPR-Cas9, and in many DNA integration events. Pol θ is a potentially important clinical target, particularly for cancers deficient in other break repair strategies. The enzyme is uniquely able to mediate joining of single-stranded 3' ends. Because of these unusual biochemical properties and its therapeutic importance, it is essential to study structures of pol θ bound to DNA. However, challenges for expression and purification are presented by the large size of pol θ (2590 residues in humans) and unusual juxtaposition of domains (a helicase-like domain and distinct DNA polymerase, separated by a region predicted to be largely disordered). Here we summarize work on the expression and purification of the full-length protein, and then focus on the design, expression, and purification of an active C-terminal polymerase fragment. The generation of this active construct was nontrivial and time consuming. Almost all published biochemical work to date has been performed with this domain fragment. Strategies to obtain and improve crystals of a ternary pol θ complex (enzyme:DNA:nucleotide) are also presented, along with key elements of the structure.
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Affiliation(s)
| | - Sara K Martin
- The University of Texas MD Anderson Cancer Center, Smithville, TX, United States; MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
| | - Richard D Wood
- The University of Texas MD Anderson Cancer Center, Smithville, TX, United States; MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
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498
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Janssen A, Breuer GA, Brinkman EK, van der Meulen AI, Borden SV, van Steensel B, Bindra RS, LaRocque JR, Karpen GH. A single double-strand break system reveals repair dynamics and mechanisms in heterochromatin and euchromatin. Genes Dev 2017; 30:1645-57. [PMID: 27474442 PMCID: PMC4973294 DOI: 10.1101/gad.283028.116] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 07/05/2016] [Indexed: 01/04/2023]
Abstract
Janssen et al. developed an in vivo single double-strand break (DSB) system for both heterochromatic and euchromatic loci in Drosophila melanogaster. Live imaging and sequence analysis of repair products reveal that DSBs in euchromatin and heterochromatin are repaired with similar kinetics, employ both NHEJ and HR, and can use homologous chromosomes as an HR template. Repair of DNA double-strand breaks (DSBs) must be properly orchestrated in diverse chromatin regions to maintain genome stability. The choice between two main DSB repair pathways, nonhomologous end-joining (NHEJ) and homologous recombination (HR), is regulated by the cell cycle as well as chromatin context. Pericentromeric heterochromatin forms a distinct nuclear domain that is enriched for repetitive DNA sequences that pose significant challenges for genome stability. Heterochromatic DSBs display specialized temporal and spatial dynamics that differ from euchromatic DSBs. Although HR is thought to be the main pathway used to repair heterochromatic DSBs, direct tests of this hypothesis are lacking. Here, we developed an in vivo single DSB system for both heterochromatic and euchromatic loci in Drosophila melanogaster. Live imaging of single DSBs in larval imaginal discs recapitulates the spatio–temporal dynamics observed for irradiation (IR)-induced breaks in cell culture. Importantly, live imaging and sequence analysis of repair products reveal that DSBs in euchromatin and heterochromatin are repaired with similar kinetics, employ both NHEJ and HR, and can use homologous chromosomes as an HR template. This direct analysis reveals important insights into heterochromatin DSB repair in animal tissues and provides a foundation for further explorations of repair mechanisms in different chromatin domains.
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Affiliation(s)
- Aniek Janssen
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Gregory A Breuer
- Department of Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut 06510, USA; Department of Experimental Pathology, Yale School of Medicine, New Haven, Connecticut 06510, USA
| | - Eva K Brinkman
- Division of Gene Regulation, Netherlands Cancer Institute, Amsterdam 1066 CX, the Netherlands
| | - Annelot I van der Meulen
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Sean V Borden
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Bas van Steensel
- Division of Gene Regulation, Netherlands Cancer Institute, Amsterdam 1066 CX, the Netherlands
| | - Ranjit S Bindra
- Department of Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut 06510, USA; Department of Experimental Pathology, Yale School of Medicine, New Haven, Connecticut 06510, USA
| | - Jeannine R LaRocque
- Department of Human Science, School of Nursing and Health Studies, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Gary H Karpen
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA; Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA
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499
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van de Ven AL, Tangutoori S, Baldwin P, Qiao J, Gharagouzloo C, Seitzer N, Clohessy JG, Makrigiorgos GM, Cormack R, Pandolfi PP, Sridhar S. Nanoformulation of Olaparib Amplifies PARP Inhibition and Sensitizes PTEN/TP53-Deficient Prostate Cancer to Radiation. Mol Cancer Ther 2017; 16:1279-1289. [PMID: 28500233 DOI: 10.1158/1535-7163.mct-16-0740] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 03/09/2017] [Accepted: 04/28/2017] [Indexed: 12/17/2022]
Abstract
The use of PARP inhibitors in combination with radiotherapy is a promising strategy to locally enhance DNA damage in tumors. Here we show that radiation-resistant cells and tumors derived from a Pten/Trp53-deficient mouse model of advanced prostate cancer are rendered radiation sensitive following treatment with NanoOlaparib, a lipid-based injectable nanoformulation of olaparib. This enhancement in radiosensitivity is accompanied by radiation dose-dependent changes in γ-H2AX expression and is specific to NanoOlaparib alone. In animals, twice-weekly intravenous administration of NanoOlaparib results in significant tumor growth inhibition, whereas previous studies of oral olaparib as monotherapy have shown no therapeutic efficacy. When NanoOlaparib is administered prior to radiation, a single dose of radiation is sufficient to triple the median mouse survival time compared to radiation only controls. Half of mice treated with NanoOlaparib + radiation achieved a complete response over the 13-week study duration. Using ferumoxytol as a surrogate nanoparticle, MRI studies revealed that NanoOlaparib enhances the intratumoral accumulation of systemically administered nanoparticles. NanoOlaparib-treated tumors showed up to 19-fold higher nanoparticle accumulation compared to untreated and radiation-only controls, suggesting that the in vivo efficacy of NanoOlaparib may be potentiated by its ability to enhance its own accumulation. Together, these data suggest that NanoOlaparib may be a promising new strategy for enhancing the radiosensitivity of radiation-resistant tumors lacking BRCA mutations, such as those with PTEN and TP53 deletions. Mol Cancer Ther; 16(7); 1279-89. ©2017 AACR.
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Affiliation(s)
- Anne L van de Ven
- Department of Physics, Northeastern University, Boston, Massachusetts.,Nanomedicine Science & Technology Center, Northeastern University, Boston, Massachusetts
| | - Shifalika Tangutoori
- Nanomedicine Science & Technology Center, Northeastern University, Boston, Massachusetts.,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Paige Baldwin
- Nanomedicine Science & Technology Center, Northeastern University, Boston, Massachusetts.,Department of Bioengineering, Northeastern University, Boston, Massachusetts
| | - Ju Qiao
- Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts
| | - Codi Gharagouzloo
- Department of Bioengineering, Northeastern University, Boston, Massachusetts
| | - Nina Seitzer
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Boston, Massachusetts
| | - John G Clohessy
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Boston, Massachusetts
| | - G Mike Makrigiorgos
- Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Robert Cormack
- Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Pier Paolo Pandolfi
- Cancer Research Institute, Beth Israel Deaconess Cancer Center, Boston, Massachusetts
| | - Srinivas Sridhar
- Department of Physics, Northeastern University, Boston, Massachusetts. .,Nanomedicine Science & Technology Center, Northeastern University, Boston, Massachusetts.,Department of Radiation Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
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500
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Talens F, Jalving M, Gietema JA, Van Vugt MA. Therapeutic targeting and patient selection for cancers with homologous recombination defects. Expert Opin Drug Discov 2017; 12:565-581. [PMID: 28425306 DOI: 10.1080/17460441.2017.1322061] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
INTRODUCTION DNA double-strand breaks (DSBs) are toxic DNA lesions that can be repaired by non-homologous end-joining (NHEJ) or homologous recombination (HR). Mutations in HR genes elicit a predisposition to cancer; yet, they also result in increased sensitivity to certain DNA damaging agents and poly (ADP-ribose) polymerase (PARP) inhibitors. To optimally implement PARP inhibitor treatment, it is important that patients with HR-deficient tumors are adequately selected. Areas covered: Herein, the authors describe the HR pathway mechanistically and review the treatment of HR-deficient cancers, with a specific focus on PARP inhibition for BRCA1/2-mutated breast and ovarian cancer. In addition, mechanisms of acquired PARP inhibitor resistance are discussed. Furthermore, combination therapies with PARP inhibitors are reviewed, in the context of both HR-deficient and HR-proficient tumors and methods for proper patient selection are also discussed. Expert opinion: Currently, only patients with germline or somatic BRCA1/2 mutations are eligible for PARP inhibitor treatment and only a proportion of patients respond. Patients with HR-deficient tumors caused by other (epi)genetic events may also benefit from PARP inhibitor treatment. Ideally, selection of eligible patients for PARP inhibitor treatment include a functional HR read-out, in which cancer cells are interrogated for their ability to perform HR repair and maintain replication fork stability.
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Affiliation(s)
- Francien Talens
- a Department of Medical Oncology , University Medical Center Groningen, University of Groningen , Groningen , The Netherlands
| | - Mathilde Jalving
- a Department of Medical Oncology , University Medical Center Groningen, University of Groningen , Groningen , The Netherlands
| | - Jourik A Gietema
- a Department of Medical Oncology , University Medical Center Groningen, University of Groningen , Groningen , The Netherlands
| | - Marcel A Van Vugt
- a Department of Medical Oncology , University Medical Center Groningen, University of Groningen , Groningen , The Netherlands
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