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Bader AS, Bushell M. iMUT-seq: high-resolution DSB-induced mutation profiling reveals prevalent homologous-recombination dependent mutagenesis. Nat Commun 2023; 14:8419. [PMID: 38110444 PMCID: PMC10728174 DOI: 10.1038/s41467-023-44167-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 12/04/2023] [Indexed: 12/20/2023] Open
Abstract
DNA double-strand breaks (DSBs) are the most mutagenic form of DNA damage, and play a significant role in cancer biology, neurodegeneration and aging. However, studying DSB-induced mutagenesis is limited by our current approaches. Here, we describe iMUT-seq, a technique that profiles DSB-induced mutations at high-sensitivity and single-nucleotide resolution around endogenous DSBs. By depleting or inhibiting 20 DSB-repair factors we define their mutational signatures in detail, revealing insights into the mechanisms of DSB-induced mutagenesis. Notably, we find that homologous-recombination (HR) is more mutagenic than previously thought, inducing prevalent base substitutions and mononucleotide deletions at distance from the break due to DNA-polymerase errors. Simultaneously, HR reduces translocations, suggesting a primary role of HR is specifically the prevention of genomic rearrangements. The results presented here offer fundamental insights into DSB-induced mutagenesis and have significant implications for our understanding of cancer biology and the development of DDR-targeting chemotherapeutics.
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Affiliation(s)
- Aldo S Bader
- Cancer Research UK Beatson Institute, Glasgow, G61 1BD, UK.
- Cancer Research UK/CI, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK.
- The Gurdon Institute, University of Cambridge, Biochemistry, Cambridge, UK.
| | - Martin Bushell
- Cancer Research UK Beatson Institute, Glasgow, G61 1BD, UK.
- Institute of Cancer Sciences, University of Glasgow, Glasgow, G61 1QH, UK.
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2
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Vogt A, He Y. Structure and mechanism in non-homologous end joining. DNA Repair (Amst) 2023; 130:103547. [PMID: 37556875 PMCID: PMC10528545 DOI: 10.1016/j.dnarep.2023.103547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 07/26/2023] [Accepted: 07/27/2023] [Indexed: 08/11/2023]
Abstract
DNA double-stranded breaks (DSBs) are a particularly challenging form of DNA damage to repair because the damaged DNA must not only undergo the chemical reactions responsible for returning it to its original state, but, additionally, the two free ends can become physically separated in the nucleus and must be bridged prior to repair. In nonhomologous end joining (NHEJ), one of the major pathways of DSB repair, repair is carried out by a number of repair factors capable of binding to and directly joining DNA ends. It has been unclear how these processes are carried out at a molecular level, owing in part to the lack of structural evidence describing the coordination of the NHEJ factors with each other and a DNA substrate. Advances in cryo-Electron Microscopy (cryo-EM), allowing for the structural characterization of large protein complexes that would be intractable using other techniques, have led to the visualization several key steps of the NHEJ process, which support a model of sequential assembly of repair factors at the DSB, followed by end-bridging mediated by protein-protein complexes and transition to full synapsis. Here we examine the structural evidence for these models, devoting particular attention to recent work identifying a new NHEJ intermediate state and incorporating new NHEJ factors into the general mechanism. We also discuss the evolving understanding of end-bridging mechanisms in NHEJ and DNA-PKcs's role in mediating DSB repair.
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Affiliation(s)
- Alex Vogt
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA; Interdisciplinary Biological Sciences Program, Northwestern University, Evanston, USA
| | - Yuan He
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA; Interdisciplinary Biological Sciences Program, Northwestern University, Evanston, USA; Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, USA; Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Northwestern University, Chicago, USA.
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3
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Liu Y, Cottle WT, Ha T. Mapping cellular responses to DNA double-strand breaks using CRISPR technologies. Trends Genet 2023; 39:560-574. [PMID: 36967246 PMCID: PMC11062594 DOI: 10.1016/j.tig.2023.02.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 02/23/2023] [Accepted: 02/24/2023] [Indexed: 06/15/2023]
Abstract
DNA double-strand breaks (DSBs) are one of the most genotoxic DNA lesions, driving a range of pathological defects from cancers to immunodeficiencies. To combat genomic instability caused by DSBs, evolution has outfitted cells with an intricate protein network dedicated to the rapid and accurate repair of these lesions. Pioneering studies have identified and characterized many crucial repair factors in this network, while the advent of genome manipulation tools like clustered regularly interspersed short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) has reinvigorated interest in DSB repair mechanisms. This review surveys the latest methodological advances and biological insights gained by utilizing Cas9 as a precise 'damage inducer' for the study of DSB repair. We highlight rapidly inducible Cas9 systems that enable synchronized and efficient break induction. When combined with sequencing and genome-specific imaging approaches, inducible Cas9 systems greatly expand our capability to spatiotemporally characterize cellular responses to DSB at specific genomic coordinates, providing mechanistic insights that were previously unobtainable.
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Affiliation(s)
- Yang Liu
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD, USA
| | - W Taylor Cottle
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD, USA
| | - Taekjip Ha
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD, USA; Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA; Department of Biophysics, Johns Hopkins University, Baltimore, MD, USA; Howard Hughes Medical Institute, Baltimore, MD, USA.
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4
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Uusküla-Reimand L, Wilson MD. Untangling the roles of TOP2A and TOP2B in transcription and cancer. SCIENCE ADVANCES 2022; 8:eadd4920. [PMID: 36322662 PMCID: PMC9629710 DOI: 10.1126/sciadv.add4920] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 09/12/2022] [Indexed: 06/09/2023]
Abstract
Type II topoisomerases (TOP2) are conserved regulators of chromatin topology that catalyze reversible DNA double-strand breaks (DSBs) and are essential for maintaining genomic integrity in diverse dynamic processes such as transcription, replication, and cell division. While controlled TOP2-mediated DSBs are an elegant solution to topological constraints of DNA, DSBs also contribute to the emergence of chromosomal translocations and mutations that drive cancer. The central importance of TOP2 enzymes as frontline chemotherapeutic targets is well known; however, their precise biological functions and impact in cancer development are still poorly understood. In this review, we provide an updated overview of TOP2A and TOP2B in the regulation of chromatin topology and transcription, and discuss the recent discoveries linking TOP2 activities with cancer pathogenesis.
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Affiliation(s)
- Liis Uusküla-Reimand
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, ON, Canada
| | - Michael D. Wilson
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, ON, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
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5
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Zhao H, Hartono SR, de Vera KMF, Yu Z, Satchi K, Zhao T, Sciammas R, Sanz L, Chédin F, Barlow J. Senataxin and RNase H2 act redundantly to suppress genome instability during class switch recombination. eLife 2022; 11:78917. [PMID: 36542058 PMCID: PMC9771370 DOI: 10.7554/elife.78917] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 11/17/2022] [Indexed: 12/24/2022] Open
Abstract
Class switch recombination generates distinct antibody isotypes critical to a robust adaptive immune system, and defects are associated with autoimmune disorders and lymphomagenesis. Transcription is required during class switch recombination to recruit the cytidine deaminase AID-an essential step for the formation of DNA double-strand breaks-and strongly induces the formation of R loops within the immunoglobulin heavy-chain locus. However, the impact of R loops on double-strand break formation and repair during class switch recombination remains unclear. Here, we report that cells lacking two enzymes involved in R loop removal-senataxin and RNase H2-exhibit increased R loop formation and genome instability at the immunoglobulin heavy-chain locus without impacting its transcriptional activity, AID recruitment, or class switch recombination efficiency. Senataxin and RNase H2-deficient cells also exhibit increased insertion mutations at switch junctions, a hallmark of alternative end joining. Importantly, these phenotypes were not observed in cells lacking senataxin or RNase H2B alone. We propose that senataxin acts redundantly with RNase H2 to mediate timely R loop removal, promoting efficient repair while suppressing AID-dependent genome instability and insertional mutagenesis.
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Affiliation(s)
- Hongchang Zhao
- Department of Microbiology and Molecular Genetics, University of California, DavisDavisUnited States
| | - Stella R Hartono
- Department of Molecular and Cellular Biology, University of California, DavisDavisUnited States
| | | | - Zheyuan Yu
- Department of Microbiology and Molecular Genetics, University of California, DavisDavisUnited States,Graduate Group in Biostatistics, University of California, DavisDavisUnited States
| | - Krishni Satchi
- Department of Microbiology and Molecular Genetics, University of California, DavisDavisUnited States
| | - Tracy Zhao
- Department of Microbiology and Molecular Genetics, University of California, DavisDavisUnited States
| | - Roger Sciammas
- Center for Immunology and Infectious Diseases, University of California, DavisDavisUnited States
| | - Lionel Sanz
- Department of Molecular and Cellular Biology, University of California, DavisDavisUnited States
| | - Frédéric Chédin
- Department of Molecular and Cellular Biology, University of California, DavisDavisUnited States
| | - Jacqueline Barlow
- Department of Microbiology and Molecular Genetics, University of California, DavisDavisUnited States
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6
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Qu W, Liu C, Xu YT, Xu YM, Luo MC. The formation and repair of DNA double-strand breaks in mammalian meiosis. Asian J Androl 2021; 23:572-579. [PMID: 34708719 PMCID: PMC8577251 DOI: 10.4103/aja202191] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Programmed DNA double-strand breaks (DSBs) are necessary for meiosis in mammals. A sufficient number of DSBs ensure the normal pairing/synapsis of homologous chromosomes. Abnormal DSB repair undermines meiosis, leading to sterility in mammals. The DSBs that initiate recombination are repaired as crossovers and noncrossovers, and crossovers are required for correct chromosome separation. Thus, the placement, timing, and frequency of crossover formation must be tightly controlled. Importantly, mutations in many genes related to the formation and repair of DSB result in infertility in humans. These mutations cause nonobstructive azoospermia in men, premature ovarian insufficiency and ovarian dysgenesis in women. Here, we have illustrated the formation and repair of DSB in mammals, summarized major factors influencing the formation of DSB and the theories of crossover regulation.
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Affiliation(s)
- Wei Qu
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, School of Basic Medical Sciences, Wuhan University, Wuhan 430072, China
| | - Cong Liu
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, School of Basic Medical Sciences, Wuhan University, Wuhan 430072, China
| | - Ya-Ting Xu
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, School of Basic Medical Sciences, Wuhan University, Wuhan 430072, China
| | - Yu-Min Xu
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, School of Basic Medical Sciences, Wuhan University, Wuhan 430072, China
| | - Meng-Cheng Luo
- Hubei Provincial Key Laboratory of Developmentally Originated Disease, School of Basic Medical Sciences, Wuhan University, Wuhan 430072, China
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7
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St Germain C, Zhao H, Barlow JH. Transcription-Replication Collisions-A Series of Unfortunate Events. Biomolecules 2021; 11:1249. [PMID: 34439915 PMCID: PMC8391903 DOI: 10.3390/biom11081249] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 08/12/2021] [Accepted: 08/17/2021] [Indexed: 02/07/2023] Open
Abstract
Transcription-replication interactions occur when DNA replication encounters genomic regions undergoing transcription. Both replication and transcription are essential for life and use the same DNA template making conflicts unavoidable. R-loops, DNA supercoiling, DNA secondary structure, and chromatin-binding proteins are all potential obstacles for processive replication or transcription and pose an even more potent threat to genome integrity when these processes co-occur. It is critical to maintaining high fidelity and processivity of transcription and replication while navigating through a complex chromatin environment, highlighting the importance of defining cellular pathways regulating transcription-replication interaction formation, evasion, and resolution. Here we discuss how transcription influences replication fork stability, and the safeguards that have evolved to navigate transcription-replication interactions and maintain genome integrity in mammalian cells.
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Affiliation(s)
- Commodore St Germain
- School of Mathematics and Science, Solano Community College, 4000 Suisun Valley Road, Fairfield, CA 94534, USA
- Department of Microbiology and Molecular Genetics, University of California Davis, One Shields Avenue, Davis, CA 95616, USA;
| | - Hongchang Zhao
- Department of Microbiology and Molecular Genetics, University of California Davis, One Shields Avenue, Davis, CA 95616, USA;
| | - Jacqueline H. Barlow
- Department of Microbiology and Molecular Genetics, University of California Davis, One Shields Avenue, Davis, CA 95616, USA;
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8
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Activation of DNA damage response signaling in mammalian cells by ionizing radiation. Free Radic Res 2021; 55:581-594. [PMID: 33455476 DOI: 10.1080/10715762.2021.1876853] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Cellular responses to DNA damage are fundamental to preserve genomic integrity during various endogenous and exogenous stresses. Following radiation therapy and chemotherapy, this DNA damage response (DDR) also determines development of carcinogenesis and therapeutic outcome. In humans, DNA damage activates a robust network of signal transduction cascades, driven primarily through phosphorylation events. These responses primarily involve two key non-redundant signal transducing proteins of phosphatidylinositol 3-kinase-like (PIKK) family - ATR and ATM, and their downstream kinases (hChk1 and hChk2). They further phosphorylate effectors proteins such as p53, Cdc25A and Cdc25C which function either to activate the DNA damage checkpoints and cell death mechanisms, or DNA repair pathways. Identification of molecular pathways that determine signaling after DNA damage and trigger DNA repair in response to differing types of DNA lesions allows for a far better understanding of the consequences of radiation and chemotherapy on normal and tumor cells. Here we highlight the network of DNA damage response pathways that are activated after treatment with different types of radiation. Further, we discuss regulation of cell cycle checkpoint and DNA repair processes in the context of DDR in response to radiation.
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9
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Hepburn M, Saltzberg DJ, Lee L, Fang S, Atkinson C, Strynadka NCJ, Sali A, Lees-Miller SP, Schriemer DC. The active DNA-PK holoenzyme occupies a tensed state in a staggered synaptic complex. Structure 2021; 29:467-478.e6. [PMID: 33412091 DOI: 10.1016/j.str.2020.12.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 11/14/2020] [Accepted: 12/09/2020] [Indexed: 01/06/2023]
Abstract
In the non-homologous end-joining (NHEJ) of a DNA double-strand break, DNA ends are bound and protected by DNA-PK, which synapses across the break to tether the broken ends and initiate repair. There is little clarity surrounding the nature of the synaptic complex and the mechanism governing the transition to repair. We report an integrative structure of the synaptic complex at a precision of 13.5 Å, revealing a symmetric head-to-head arrangement with a large offset in the DNA ends and an extensive end-protection mechanism involving a previously uncharacterized plug domain. Hydrogen/deuterium exchange mass spectrometry identifies an allosteric pathway connecting DNA end-binding with the kinase domain that places DNA-PK under tension in the kinase-active state. We present a model for the transition from end-protection to repair, where the synaptic complex supports hierarchical processing of the ends and scaffold assembly, requiring displacement of the catalytic subunit and tension release through kinase activity.
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Affiliation(s)
- Morgan Hepburn
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB, Canada
| | - Daniel J Saltzberg
- Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Sciences, and California Institute for Quantitative Biomedical Sciences, University of California, San Francisco, CA 94158, USA
| | - Linda Lee
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB, Canada
| | - Shujuan Fang
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB, Canada
| | - Claire Atkinson
- Department of Biochemistry and Molecular Biology and High-Resolution Macromolecular Electron Microscopy Facility, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Natalie C J Strynadka
- Department of Biochemistry and Molecular Biology and High-Resolution Macromolecular Electron Microscopy Facility, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Sciences, and California Institute for Quantitative Biomedical Sciences, University of California, San Francisco, CA 94158, USA
| | - Susan P Lees-Miller
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB, Canada; Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, University of Calgary, Calgary, AB, Canada
| | - David C Schriemer
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB, Canada; Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, University of Calgary, Calgary, AB, Canada; Department of Chemistry, University of Calgary, Calgary, AB, Canada.
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10
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Gavande NS, VanderVere-Carozza PS, Pawelczak KS, Mendoza-Munoz P, Vernon TL, Hanakahi LA, Summerlin M, Dynlacht JR, Farmer AH, Sears CR, Nasrallah NA, Garrett J, Turchi JJ. Discovery and development of novel DNA-PK inhibitors by targeting the unique Ku-DNA interaction. Nucleic Acids Res 2020; 48:11536-11550. [PMID: 33119767 PMCID: PMC7672428 DOI: 10.1093/nar/gkaa934] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 10/02/2020] [Accepted: 10/09/2020] [Indexed: 01/05/2023] Open
Abstract
DNA-dependent protein kinase (DNA-PK) plays a critical role in the non-homologous end joining (NHEJ) repair pathway and the DNA damage response (DDR). DNA-PK has therefore been pursued for the development of anti-cancer therapeutics in combination with ionizing radiation (IR). We report the discovery of a new class of DNA-PK inhibitors that act via a novel mechanism of action, inhibition of the Ku-DNA interaction. We have developed a series of highly potent and specific Ku-DNA binding inhibitors (Ku-DBi's) that block the Ku-DNA interaction and inhibit DNA-PK kinase activity. Ku-DBi's directly interact with the Ku and inhibit in vitro NHEJ, cellular NHEJ, and potentiate the cellular activity of radiomimetic agents and IR. Analysis of Ku-null cells demonstrates that Ku-DBi's cellular activity is a direct result of Ku inhibition, as Ku-null cells are insensitive to Ku-DBi's. The utility of Ku-DBi's was also revealed in a CRISPR gene-editing model where we demonstrate that the efficiency of gene insertion events was increased in cells pre-treated with Ku-DBi's, consistent with inhibition of NHEJ and activation of homologous recombination to facilitate gene insertion. These data demonstrate the discovery and application of new series of compounds that modulate DNA repair pathways via a unique mechanism of action.
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Affiliation(s)
- Navnath S Gavande
- Department of Medicine, Indiana University School of Medicine, Indianapolis IN 46202, USA
- Department of Pharmaceutical Sciences, Wayne State University College of Pharmacy and Health Sciences, Detroit, MI 48201, USA
| | | | | | - Pamela Mendoza-Munoz
- Department of Medicine, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Tyler L Vernon
- Department of Medicine, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Leslyn A Hanakahi
- Department of Biopharmaceutical Sciences, University of Illinois College of Pharmacy, Rockford, IL 61107, USA
| | - Matthew Summerlin
- Department of Biopharmaceutical Sciences, University of Illinois College of Pharmacy, Rockford, IL 61107, USA
| | - Joseph R Dynlacht
- Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Annabelle H Farmer
- Department of Medicine, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Catherine R Sears
- Department of Medicine, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Nawar Al Nasrallah
- Department of Medicine, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Joy Garrett
- Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - John J Turchi
- Department of Medicine, Indiana University School of Medicine, Indianapolis IN 46202, USA
- NERx Biosciences, 212 W 10th St. Suite A480, Indianapolis, IN 46202, USA
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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