1
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Kelliher JL, Folkerts ML, Shen KV, Song W, Tengler K, Stiefel CM, Lee SO, Dray E, Zhao W, Koss B, Pannunzio NR, Leung JW. Evolved histone tail regulates 53BP1 recruitment at damaged chromatin. Nat Commun 2024; 15:4634. [PMID: 38821984 PMCID: PMC11143218 DOI: 10.1038/s41467-024-49071-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 05/22/2024] [Indexed: 06/02/2024] Open
Abstract
The master DNA damage repair histone protein, H2AX, is essential for orchestrating the recruitment of downstream mediator and effector proteins at damaged chromatin. The phosphorylation of H2AX at S139, γH2AX, is well-studied for its DNA repair function. However, the extended C-terminal tail is not characterized. Here, we define the minimal motif on H2AX for the canonical function in activating the MDC1-RNF8-RNF168 phosphorylation-ubiquitination pathway that is important for recruiting repair proteins, such as 53BP1 and BRCA1. Interestingly, H2AX recruits 53BP1 independently from the MDC1-RNF8-RNF168 pathway through its evolved C-terminal linker region with S139 phosphorylation. Mechanistically, 53BP1 recruitment to damaged chromatin is mediated by the interaction between the H2AX C-terminal tail and the 53BP1 Oligomerization-Tudor domains. Moreover, γH2AX-linker mediated 53BP1 recruitment leads to camptothecin resistance in H2AX knockout cells. Overall, our study uncovers an evolved mechanism within the H2AX C-terminal tail for regulating DNA repair proteins at damaged chromatin.
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Affiliation(s)
- Jessica L Kelliher
- Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Melissa L Folkerts
- Department of Medicine, Division of Hematology/Oncology, University of California, Irvine, Irvine, CA, 92697, USA
- Department of Biological Chemistry, University of California, Irvine, Irvine, CA, 92626, USA
| | - Kaiyuan V Shen
- Department of Medicine, Division of Hematology/Oncology, University of California, Irvine, Irvine, CA, 92697, USA
- Department of Biological Chemistry, University of California, Irvine, Irvine, CA, 92626, USA
| | - Wan Song
- Department of Radiation Oncology, University of Texas Health and Science Center, San Antonio, TX, 78229, USA
| | - Kyle Tengler
- Department of Radiation Oncology, University of Texas Health and Science Center, San Antonio, TX, 78229, USA
| | - Clara M Stiefel
- Department of Radiation Oncology, University of Texas Health and Science Center, San Antonio, TX, 78229, USA
| | - Seong-Ok Lee
- Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Eloise Dray
- Department of Biochemistry and Structural Biology, University of Texas Health and Science Center, San Antonio, TX, 78229, USA
| | - Weixing Zhao
- Department of Biochemistry and Structural Biology, University of Texas Health and Science Center, San Antonio, TX, 78229, USA
| | - Brian Koss
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Nicholas R Pannunzio
- Department of Medicine, Division of Hematology/Oncology, University of California, Irvine, Irvine, CA, 92697, USA.
| | - Justin W Leung
- Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA.
- Department of Radiation Oncology, University of Texas Health and Science Center, San Antonio, TX, 78229, USA.
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2
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Liu D, Hsieh CL, Lieber MR. The RNA tether model for human chromosomal translocation fragile zones. Trends Biochem Sci 2024; 49:391-400. [PMID: 38490833 PMCID: PMC11069435 DOI: 10.1016/j.tibs.2024.02.003] [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: 12/04/2023] [Revised: 02/06/2024] [Accepted: 02/16/2024] [Indexed: 03/17/2024]
Abstract
One of the two chromosomal breakage events in recurring translocations in B cell neoplasms is often due to the recombination-activating gene complex (RAG complex) releasing DNA ends before end joining. The other break occurs in a fragile zone of 20-600 bp in a non-antigen receptor gene locus, with a more complex and intriguing set of mechanistic factors underlying such narrow fragile zones. These factors include activation-induced deaminase (AID), which acts only at regions of single-stranded DNA (ssDNA). Recent work leads to a model involving the tethering of AID to the nascent RNA as it emerges from the RNA polymerase. This mechanism may have relevance in class switch recombination (CSR) and somatic hypermutation (SHM), as well as broader relevance for other DNA enzymes.
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Affiliation(s)
- Di Liu
- Institute of Molecular and Translational Medicine (IMTM), and Department of Biochemistry and Molecular Biology, Xi'an Jiaotong University Health Science Center, and Key Laboratory of Environment and Genes Related to Diseases, Xi'an Jiaotong University, Ministry of Education, Xi'an, Shaanxi 710061, China
| | - Chih-Lin Hsieh
- USC Norris Comprehensive Cancer Center, Department of Urology, University of Southern California, Los Angeles, CA 90089-9176, USA
| | - Michael R Lieber
- USC Norris Comprehensive Cancer Center, Departments of Pathology and Laboratory Medicine, of Molecular Microbiology and Immunology, of Biochemistry and Molecular Medicine, and in the Section of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089-9176, USA.
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3
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Benada J, Alsowaida D, Megeney LA, Sørensen CS. Self-inflicted DNA breaks in cell differentiation and cancer. Trends Cell Biol 2023; 33:850-859. [PMID: 36997393 DOI: 10.1016/j.tcb.2023.03.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 03/05/2023] [Accepted: 03/08/2023] [Indexed: 03/30/2023]
Abstract
Self-inflicted DNA strand breaks are canonically linked with cell death pathways and the establishment of genetic diversity in immune and germline cells. Moreover, this form of DNA damage is an established source of genome instability in cancer development. However, recent studies indicate that nonlethal self-inflicted DNA strand breaks play an indispensable but underappreciated role in a variety of cell processes, including differentiation and cancer therapy responses. Mechanistically, these physiological DNA breaks originate from the activation of nucleases, which are best characterized for inducing DNA fragmentation in apoptotic cell death. In this review, we outline the emerging biology of one critical nuclease, caspase-activated DNase (CAD), and how directed activation or deployment of this enzyme can lead to divergent cell fate outcomes.
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Affiliation(s)
- Jan Benada
- Biotech Research and Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen 2200 N, Denmark
| | - Dalal Alsowaida
- Sprott Centre for Stem Cell Research, Ottawa Hospital Research Institute and the Departments of Medicine and Cellular and Molecular Medicine, University of Ottawa, Ottawa, K1H 8L6, Canada; Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Lynn A Megeney
- Sprott Centre for Stem Cell Research, Ottawa Hospital Research Institute and the Departments of Medicine and Cellular and Molecular Medicine, University of Ottawa, Ottawa, K1H 8L6, Canada.
| | - Claus S Sørensen
- Biotech Research and Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen 2200 N, Denmark.
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4
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Sterrenberg JN, Folkerts ML, Rangel V, Lee SE, Pannunzio NR. Diversity upon diversity: linking DNA double-strand break repair to blood cancer health disparities. Trends Cancer 2022; 8:328-343. [PMID: 35094960 PMCID: PMC9248772 DOI: 10.1016/j.trecan.2022.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 12/20/2021] [Accepted: 01/03/2022] [Indexed: 10/19/2022]
Abstract
Chromosomal translocations arising from aberrant repair of multiple DNA double-strand breaks (DSBs) are a defining characteristic of many cancers. DSBs are an essential part of physiological processes in antibody-producing B cells. The B cell environment is poised to generate genome instability leading to translocations relevant to the pathology of blood cancers. These are a diverse set of cancers, but limited data from under-represented groups have pointed to health disparities associated with each. We focus on the DSBs that occur in developing B cells and propose the most likely mechanism behind the formation of translocations. We also highlight specific cancers in which these rearrangements occur and address the growing concern of health disparities associated with them.
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5
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Liu D, Lieber MR. The mechanisms of human lymphoid chromosomal translocations and their medical relevance. Crit Rev Biochem Mol Biol 2021; 57:227-243. [PMID: 34875186 DOI: 10.1080/10409238.2021.2004576] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The most common human lymphoid chromosomal translocations involve concurrent failures of the recombination activating gene (RAG) complex and Activation-Induced Deaminase (AID). These are two enzymes that are normally expressed for purposes of the two site-specific DNA recombination processes: V(D)J recombination and class switch recombination (CSR). First, though it is rare, a low level of expression of AID can introduce long-lived T:G mismatch lesions at 20-600 bp fragile zones. Second, the V(D)J recombination process can occasionally fail to rejoin coding ends, and this failure may permit an opportunity for Artemis:DNA-dependent kinase catalytic subunit (DNA-PKcs) to convert the T:G mismatch sites at the fragile zones into double-strand breaks. The 20-600 bp fragile zones must be, at least transiently, in a single-stranded DNA (ssDNA) state for the first step to occur, because AID only acts on ssDNA. Here we discuss the key DNA sequence features that lead to AID action at a fragile zone, which are (a) the proximity and density of strings of cytosine nucleotides (C-strings) that cause a B/A-intermediate DNA conformation; (b) overlapping AID hotspots that contain a methyl CpG (WRCG), which AID converts to a long-lived T:G mismatch; and (c) transcription, which, though not essential, favors increased ssDNA in the fragile zone. We also summarize chromosomal features of the focal fragile zones in lymphoid malignancies and discuss the clinical relevance of understanding the translocation mechanisms. Many of the key principles covered here are also relevant to chromosomal translocations in non-lymphoid somatic cells as well.
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Affiliation(s)
- Di Liu
- Department of Pathology & Laboratory Medicine, Department of Biochemistry & Molecular Biology, Department of Molecular Microbiology and Immunology, and Section of Computational Biology in the Department of Biological Sciences, USC Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Michael R Lieber
- Department of Pathology & Laboratory Medicine, Department of Biochemistry & Molecular Biology, Department of Molecular Microbiology and Immunology, and Section of Computational Biology in the Department of Biological Sciences, USC Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
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6
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Liu D, Loh YHE, Hsieh CL, Lieber MR. Mechanistic basis for chromosomal translocations at the E2A gene and its broader relevance to human B cell malignancies. Cell Rep 2021; 36:109387. [PMID: 34260910 PMCID: PMC8327686 DOI: 10.1016/j.celrep.2021.109387] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 03/31/2021] [Accepted: 06/21/2021] [Indexed: 11/22/2022] Open
Abstract
Analysis of translocation breakpoints in human B cell malignancies reveals that DNA double-strand breaks at oncogenes most frequently occur at CpG sites located within 20-600 bp fragile zones and depend on activation-induced deaminase (AID). AID requires single-stranded DNA (ssDNA) to act, but it has been unclear why or how this region transiently acquires a ssDNA state. Here, we demonstrate the ssDNA state in the 23 bp E2A fragile zone using several methods, including native bisulfite DNA structural analysis in live human pre-B cells. AID deamination within the E2A fragile zone does not require but is increased upon transcription. High C-string density, nascent RNA tails, and direct DNA sequence repeats prolong the ssDNA state of the E2A fragile zone and increase AID deamination at overlapping AID hotspots that contain the CpG sites at which breaks occur in patients. These features provide key insights into lymphoid fragile zones generally.
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Affiliation(s)
- Di Liu
- Departments of Pathology, Biochemistry & Molecular Biology, and Molecular Microbiology & Immunology, and Section of Molecular & Computational Biology (Department of Biological Sciences), USC Norris Comprehensive Cancer Center, University of Southern California and USC Keck School of Medicine, Los Angeles, CA, USA
| | - Yong-Hwee Eddie Loh
- USC Libraries Bioinformatics Services, University of Southern California and USC Keck School of Medicine, Los Angeles, CA, USA
| | - Chih-Lin Hsieh
- Department of Urology, USC Norris Comprehensive Cancer Center, University of Southern California and USC Keck School of Medicine, Los Angeles, CA, USA
| | - Michael R Lieber
- Departments of Pathology, Biochemistry & Molecular Biology, and Molecular Microbiology & Immunology, and Section of Molecular & Computational Biology (Department of Biological Sciences), USC Norris Comprehensive Cancer Center, University of Southern California and USC Keck School of Medicine, Los Angeles, CA, USA.
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7
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Chen Z, Vong CT, Gao C, Chen S, Wu X, Wang S, Wang Y. Bilirubin Nanomedicines for the Treatment of Reactive Oxygen Species (ROS)-Mediated Diseases. Mol Pharm 2020; 17:2260-2274. [PMID: 32433886 DOI: 10.1021/acs.molpharmaceut.0c00337] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Reactive oxygen species (ROS) are chemically reactive species that are produced in cellular aerobic metabolism. They mainly include superoxide anion, hydrogen peroxide, hydroxyl radicals, singlet oxygen, ozone, and nitric oxide and are implicated in many physiological and pathological processes. Bilirubin, a cardinal pigment in the bile, has been increasingly investigated to treat cancer, diabetes, ischemia-reperfusion injury, asthma, and inflammatory bowel diseases (IBD). Indeed, bilirubin has been shown to eliminate ROS production, so it is now considered as a promising therapeutic agent for ROS-mediated diseases and can be used for the development of antioxidative nanomedicines. This review summarizes the current knowledge of the physiological mechanisms of ROS production and its role in pathological changes and focuses on discussing the antioxidative effects of bilirubin and its application in the experimental studies of nanomedicines. Previous studies have shown that bilirubin was mainly used as a responsive molecule in the microenvironment of ROS overproduction in neoplastic tissues for the development of anticancer nanodrugs; however, it could also exert powerful ROS scavenging activity in chronic inflammation and ischemia-reperfusion injury. Therefore, bilirubin, as an inartificial ROS scavenger, is expected to be used for the development of nanomedicines against more diseases due to the universality of ROS involvement in human pathological conditions.
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Affiliation(s)
- Zhejie Chen
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao 999087, China
| | - Chi Teng Vong
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao 999087, China
| | - Caifang Gao
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao 999087, China
| | - Shiyun Chen
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao 999087, China
| | - Xu Wu
- Laboratory of Molecular Pharmacology, Department of Pharmacology, School of Pharmacy, Southwest Medical University, Luzhou, Sichuan 646000, China
| | - Shengpeng Wang
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao 999087, China
| | - Yitao Wang
- State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao 999087, China
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8
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Branton SA, Ghorbani A, Bolt BN, Fifield H, Berghuis LM, Larijani M. Activation-induced cytidine deaminase can target multiple topologies of double-stranded DNA in a transcription-independent manner. FASEB J 2020; 34:9245-9268. [PMID: 32437054 DOI: 10.1096/fj.201903036rr] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 04/20/2020] [Accepted: 04/24/2020] [Indexed: 12/30/2022]
Abstract
Activation-induced cytidine deaminase (AID) mutates immunoglobulin genes and acts genome-wide. AID targets robustly transcribed genes, and purified AID acts on single-stranded (ss) but not double-stranded (ds) DNA oligonucleotides. Thus, it is believed that transcription is the generator of ssDNA for AID. Previous cell-free studies examining the relationship between transcription and AID targeting have employed a bacterial colony count assay wherein AID reverts an antibiotic resistance stop codon in plasmid substrates, leading to colony formation. Here, we established a novel assay where kb-long dsDNA of varying topologies is incubated with AID, with or without transcription, followed by direct sequencing. This assay allows for an unselected and in-depth comparison of mutation frequency and pattern of AID targeting in the absence of transcription or across a range of transcription dynamics. We found that without transcription, AID targets breathing ssDNA in supercoiled and, to a lesser extent, in relaxed dsDNA. The most optimal transcription only modestly enhanced AID action on supercoiled dsDNA in a manner dependent on RNA polymerase speed. These data suggest that the correlation between transcription and AID targeting may reflect transcription leading to AID-accessible breathing ssDNA patches naturally occurring in de-chromatinized dsDNA, as much as being due to transcription directly generating ssDNA.
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Affiliation(s)
- Sarah A Branton
- Program in Immunology and Infectious Diseases, Department of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Atefeh Ghorbani
- Program in Immunology and Infectious Diseases, Department of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Brittany N Bolt
- Program in Immunology and Infectious Diseases, Department of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Heather Fifield
- Program in Immunology and Infectious Diseases, Department of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Lesley M Berghuis
- Program in Immunology and Infectious Diseases, Department of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Mani Larijani
- Program in Immunology and Infectious Diseases, Department of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, NL, Canada.,Department of Molecular Biology and Biochemistry, Faculty of Science, Simon Fraser University, Burnaby, BC, Canada
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9
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Santaus TM, Greenberg K, Suri P, Geddes CD. Elucidation of a non-thermal mechanism for DNA/RNA fragmentation and protein degradation when using Lyse-It. PLoS One 2019; 14:e0225475. [PMID: 31790434 PMCID: PMC6886747 DOI: 10.1371/journal.pone.0225475] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 11/05/2019] [Indexed: 01/11/2023] Open
Abstract
Rapid sample preparation is one of the leading bottlenecks to low-cost and efficient sample component detection. To overcome this setback, a technology known as Lyse-It has been developed to rapidly (less than 60 seconds) lyse Gram-positive and-negative bacteria alike, while simultaneously fragmenting DNA/RNA and proteins into tunable sizes. This technology has been used with a variety of organisms, but the underlying mechanism behind how the technology actually works to fragment DNA/RNA and proteins has hitherto been studied. It is generally understood how temperature affects cellular lysing, but for DNA/RNA and protein degradation, the temperature and amount of energy introduced by microwave irradiation of the sample, cannot explain the degradation of the biomolecules to the extent that was being observed. Thus, an investigation into the microwave generation of reactive oxygen species, in particular singlet oxygen, hydroxyl radicals, and superoxide anion radicals, was undertaken. Herein, we probe one aspect, the generation of reactive oxygen species (ROS), which is thought to contribute to a non-thermal mechanism behind biomolecule fragmentation with the Lyse-It technology. By utilizing off/on (Photoinduced electron transfer) PET fluorescent-based probes highly specific for reactive oxygen species, it was found that as oxygen concentration in the sample and/or microwave irradiation power increases, more reactive oxygen species are generated and ultimately, more oxidation and biomolecule fragmentation occurs within the microwave cavity.
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Affiliation(s)
- Tonya M. Santaus
- Chemistry and Biochemistry Department, University of Maryland, Baltimore County, Baltimore, Maryland, United States of America
- Institute of Fluorescence, University of Maryland, Baltimore County, Baltimore, Maryland, United States of America
| | - Ken Greenberg
- Chemistry and Biochemistry Department, University of Maryland, Baltimore County, Baltimore, Maryland, United States of America
| | - Prabhdeep Suri
- Chemistry and Biochemistry Department, University of Maryland, Baltimore County, Baltimore, Maryland, United States of America
| | - Chris D. Geddes
- Chemistry and Biochemistry Department, University of Maryland, Baltimore County, Baltimore, Maryland, United States of America
- Institute of Fluorescence, University of Maryland, Baltimore County, Baltimore, Maryland, United States of America
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10
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Pannunzio NR, Lieber MR. Constitutively active Artemis nuclease recognizes structures containing single-stranded DNA configurations. DNA Repair (Amst) 2019; 83:102676. [PMID: 31377101 DOI: 10.1016/j.dnarep.2019.102676] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 07/24/2019] [Accepted: 07/25/2019] [Indexed: 01/03/2023]
Abstract
The Artemis nuclease recognizes and endonucleolytically cleaves at single-stranded to double-stranded DNA (ss/dsDNA) boundaries. It is also a key enzyme in the non-homologous end joining (NHEJ) DNA double-strand break repair pathway. Previously, a truncated form, Artemis-413, was developed that is constitutively active both in vitro and in vivo. Here, we use this constitutively active form of Artemis to detect DNA structures with ss/dsDNA boundaries that arise under topological stress. Topoisomerases prevent abnormal levels of torsional stress through modulation of positive and negative supercoiling. We show that overexpression of Artemis-413 in yeast cells carrying genetic mutations that ablate topoisomerase activity have an increased frequency of DNA double-strand breaks (DSBs). Based on the biochemical activity of Artemis, this suggests an increase in ss/dsDNA-containing structures upon increased torsional stress, with DSBs arising due to Artemis cutting at these ss/dsDNA structures. Camptothecin targets topoisomerase IB (Top1), and cells treated with camptothecin show increased DSBs. We find that expression of Artemis-413 in camptothecin-treated cells leads to a reduction in DSBs, the opposite of what we find with topoisomerase genetic mutations. This contrast between outcomes not only confirms that topoisomerase mutation and topoisomerase poisoning have distinct effects on cells, but also demonstrates the usefulness of Artemis-413 to study changes in DNA structure.
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Affiliation(s)
- Nicholas R Pannunzio
- Department of Pathology, Keck School of Medicine of University of Southern California, Los Angeles, CA, 90089, USA; Norris Comprehensive Cancer Center, Keck School of Medicine of University of Southern California, Los Angeles, CA, 90089, USA.
| | - Michael R Lieber
- Department of Pathology, Keck School of Medicine of University of Southern California, Los Angeles, CA, 90089, USA; Norris Comprehensive Cancer Center, Keck School of Medicine of University of Southern California, Los Angeles, CA, 90089, USA; Department of Biological Sciences, Molecular and Computational Biology Section, University of Southern California, Los Angeles, CA, 90089, USA.
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11
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Kaushal S, Freudenreich CH. The role of fork stalling and DNA structures in causing chromosome fragility. Genes Chromosomes Cancer 2019; 58:270-283. [PMID: 30536896 DOI: 10.1002/gcc.22721] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 11/13/2018] [Accepted: 12/03/2018] [Indexed: 12/19/2022] Open
Abstract
Alternative non-B form DNA structures, also called secondary structures, can form in certain DNA sequences under conditions that produce single-stranded DNA, such as during replication, transcription, and repair. Direct links between secondary structure formation, replication fork stalling, and genomic instability have been found for many repeated DNA sequences that cause disease when they expand. Common fragile sites (CFSs) are known to be AT-rich and break under replication stress, yet the molecular basis for their fragility is still being investigated. Over the past several years, new evidence has linked both the formation of secondary structures and transcription to fork stalling and fragility of CFSs. How these two events may synergize to cause fragility and the role of nuclease cleavage at secondary structures in rare and CFSs are discussed here. We also highlight evidence for a new hypothesis that secondary structures at CFSs not only initiate fragility but also inhibit healing, resulting in their characteristic appearance.
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Affiliation(s)
- Simran Kaushal
- Department of Biology, Tufts University, Medford, Massachusetts
| | - Catherine H Freudenreich
- Department of Biology, Tufts University, Medford, Massachusetts.,Program in Genetics, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, Massachusetts
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12
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Thioredoxin and Glutaredoxin Systems Required for Oxidative Stress Resistance, Fungicide Sensitivity, and Virulence of Alternaria alternata. Appl Environ Microbiol 2018; 84:AEM.00086-18. [PMID: 29752269 DOI: 10.1128/aem.00086-18] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 05/04/2018] [Indexed: 01/07/2023] Open
Abstract
This study determined the function of thioredoxin and glutaredoxin systems in the phytopathogenic fungus Alternaria alternata via analyzing mutants obtained from the targeted deletion of genes encoding thioredoxin peroxidase (Tsa1), thioredoxin reductase (Trr1), and glutathione reductase (Glr1). Trr1 and Glr1, but not Tsa1, are required for growth and conidiation. The reduced growth and conidiation seen in the Trr1 or Glr1 deletion mutant can be restored by glutathione. Deletion mutants showing growth inhibition by oxidants are defective for H2O2 detoxification and induce smaller lesions on citrus leaves. Trr1 and Glr1, but not Tsa1, also contribute to NaCl resistance. Glr1 is required for sorbitol resistance and is responsible for resistance to mancozeb and boscalid but not chlorothalonil fungicides, a novel phenotype that has not been reported in fungi. Trr1 is required for resistance to boscalid and chlorothalonil fungicides but confers susceptibility to mancozeb. The Tsa1 deletion mutant displays wild-type sensitivity to the tested fungicides. The expression of Tsa1 and Trr1 is regulated by the oxidative stress responsive regulators Yap1, Hog1, and Skn7. The expression of Tsa1, but not Trr1, is also regulated indirectly by the NADPH oxidase. The results indicate that the capability to resist oxidative stress is required for virulence of A. alternataIMPORTANCE The thioredoxin and glutaredoxin systems are important thiol antioxidant systems in cells, and knowledge of these two systems in the plant-pathogenic fungus A. alternata is useful for finding new strategies to reduce the virulence of this pathogen. In this study, we demonstrated that thiol antioxidant system-related genes (Tsa1, Trr1, and Glr1) are required for H2O2 detoxification and virulence in A. alternata Moreover, deletion of Trr1 results in hypersensitivity to the fungicides chlorothalonil and boscalid, and Glr1 deletion mutants are highly sensitive to mancozeb, which is the fungicide mostly used in citrus fields. Therefore, our findings demonstrate that the ability to detoxify reactive oxygen species (ROS) plays a critical role in pathogenesis on citrus and provide novel insights into the physiological functions of thiol-containing systems in fungicide sensitivity for A. alternata.
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13
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Pannunzio NR, Lieber MR. Concept of DNA Lesion Longevity and Chromosomal Translocations. Trends Biochem Sci 2018; 43:490-498. [PMID: 29735400 DOI: 10.1016/j.tibs.2018.04.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 04/07/2018] [Accepted: 04/08/2018] [Indexed: 01/11/2023]
Abstract
A subset of chromosomal translocations related to B cell malignancy in human patients arises due to DNA breaks occurring within defined 20-600 base pair (bp) zones. Several factors influence the breakage rate at these sites including transcription, DNA sequence, and topological tension. These factors favor non-B DNA structures that permit formation of transient single-stranded DNA (ssDNA), making the DNA more vulnerable to agents such as the enzyme activation-induced cytidine deaminase (AID) and reactive oxygen species (ROS). Certain DNA lesions created during the ssDNA state persist after the DNA resumes its normal duplex structure. We propose that factors favoring both formation of transient ssDNA and persistent DNA lesions are key in determining the DNA breakage mechanism.
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Affiliation(s)
- Nicholas R Pannunzio
- University of Southern California Keck School of Medicine, Norris Comprehensive Cancer Center, Los Angeles, CA 90033, USA
| | - Michael R Lieber
- University of Southern California Keck School of Medicine, Norris Comprehensive Cancer Center, Los Angeles, CA 90033, USA; Department of Pathology, Keck School of Medicine of USC, Los Angeles, CA 90033, USA; Department of Molecular Microbiology and Immunology, Keck School of Medicine of USC, Los Angeles, CA 90033, USA; Department of Biochemistry and Molecular Biology, Keck School of Medicine of USC, Los Angeles, CA 90033, USA; Section of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA.
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14
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Strengths and Weaknesses of the Current Strategies to Map and Characterize R-Loops. Noncoding RNA 2018; 4:ncrna4020009. [PMID: 29657305 PMCID: PMC6027298 DOI: 10.3390/ncrna4020009] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 03/22/2018] [Accepted: 03/23/2018] [Indexed: 12/26/2022] Open
Abstract
R-loops are evolutionarily conserved three-stranded structures that result from the formation of stable DNA:RNA hybrids in the genome. R-loops have attracted increasing interest in recent years as potent regulators of gene expression and genome stability. In particular, their strong association with severe replication stress makes them potential oncogenic structures. Despite their importance, the rules that govern their formation and their dynamics are still controversial and an in-depth description of their direct impact on chromatin organization and DNA transactions is still lacking. To better understand the diversity of R-loop functions, reliable, accurate, and quantitative mapping techniques, as well as functional assays are required. Here, I review the different approaches that are currently used to do so and to highlight their individual strengths and weaknesses. In particular, I review the advantages and disadvantages of using the S9.6 antibody to map R-loops in vivo in an attempt to propose guidelines for best practices.
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15
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Sallmyr A, Tomkinson AE. Repair of DNA double-strand breaks by mammalian alternative end-joining pathways. J Biol Chem 2018. [PMID: 29530982 DOI: 10.1074/jbc.tm117.000375] [Citation(s) in RCA: 161] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alternative end-joining (a-EJ) pathways, which repair DNA double-strand breaks (DSBs), are initiated by end resection that generates 3' single strands. This reaction is shared, at least in part, with homologous recombination but distinguishes a-EJ from the major nonhomologous end-joining pathway. Although the a-EJ pathways make only a minor and poorly understood contribution to DSB repair in nonmalignant cells, there is growing interest in these pathways, as they generate genomic rearrangements that are hallmarks of cancer cells. Here, we review and discuss the current understanding of the mechanisms and regulation of a-EJ pathways, the role of a-EJ in human disease, and the potential utility of a-EJ as a therapeutic target in cancer.
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Affiliation(s)
- Annahita Sallmyr
- From the Departments of Internal Medicine and Molecular Genetics and Microbiology, University of New Mexico Comprehensive Cancer Center, University of New Mexico, Albuquerque, New Mexico 87131
| | - Alan E Tomkinson
- From the Departments of Internal Medicine and Molecular Genetics and Microbiology, University of New Mexico Comprehensive Cancer Center, University of New Mexico, Albuquerque, New Mexico 87131
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