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Gospodinov A, Dzhokova S, Petrova M, Ugrinova I. Chromatin regulators in DNA replication and genome stability maintenance during S-phase. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2023; 135:243-280. [PMID: 37061334 DOI: 10.1016/bs.apcsb.2023.02.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
The duplication of genetic information is central to life. The replication of genetic information is strictly controlled to ensure that each piece of genomic DNA is copied only once during a cell cycle. Factors that slow or stop replication forks cause replication stress. Replication stress is a major source of genome instability in cancer cells. Multiple control mechanisms facilitate the unimpeded fork progression, prevent fork collapse and coordinate fork repair. Chromatin alterations, caused by histone post-translational modifications and chromatin remodeling, have critical roles in normal replication and in avoiding replication stress and its consequences. This text reviews the chromatin regulators that ensure DNA replication and the proper response to replication stress. We also briefly touch on exploiting replication stress in therapeutic strategies. As chromatin regulators are frequently mutated in cancer, manipulating their activity could provide many possibilities for personalized treatment.
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Affiliation(s)
- Anastas Gospodinov
- Roumen Tsanev Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia, Bulgaria.
| | - Stefka Dzhokova
- Roumen Tsanev Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Maria Petrova
- Roumen Tsanev Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Iva Ugrinova
- Roumen Tsanev Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia, Bulgaria
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2
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Daiß JL, Pilsl M, Straub K, Bleckmann A, Höcherl M, Heiss FB, Abascal-Palacios G, Ramsay EP, Tlučková K, Mars JC, Fürtges T, Bruckmann A, Rudack T, Bernecky C, Lamour V, Panov K, Vannini A, Moss T, Engel C. The human RNA polymerase I structure reveals an HMG-like docking domain specific to metazoans. Life Sci Alliance 2022; 5:5/11/e202201568. [PMID: 36271492 PMCID: PMC9438803 DOI: 10.26508/lsa.202201568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 06/20/2022] [Accepted: 08/09/2022] [Indexed: 11/24/2022] Open
Abstract
We characterize the human RNA polymerase I by evolutionary biochemistry and cryo-EM revealing a built-in structural domain that apparently serves as transcription factor–binding platform in metazoans. Transcription of the ribosomal RNA precursor by RNA polymerase (Pol) I is a major determinant of cellular growth, and dysregulation is observed in many cancer types. Here, we present the purification of human Pol I from cells carrying a genomic GFP fusion on the largest subunit allowing the structural and functional analysis of the enzyme across species. In contrast to yeast, human Pol I carries a single-subunit stalk, and in vitro transcription indicates a reduced proofreading activity. Determination of the human Pol I cryo-EM reconstruction in a close-to-native state rationalizes the effects of disease-associated mutations and uncovers an additional domain that is built into the sequence of Pol I subunit RPA1. This “dock II” domain resembles a truncated HMG box incapable of DNA binding which may serve as a downstream transcription factor–binding platform in metazoans. Biochemical analysis, in situ modelling, and ChIP data indicate that Topoisomerase 2a can be recruited to Pol I via the domain and cooperates with the HMG box domain–containing factor UBF. These adaptations of the metazoan Pol I transcription system may allow efficient release of positive DNA supercoils accumulating downstream of the transcription bubble.
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Affiliation(s)
- Julia L Daiß
- Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
| | - Michael Pilsl
- Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
| | - Kristina Straub
- Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
| | - Andrea Bleckmann
- Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
| | - Mona Höcherl
- Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
| | - Florian B Heiss
- Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
| | - Guillermo Abascal-Palacios
- Division of Structural Biology, The Institute of Cancer Research, London, UK
- Biofisika Institute (CSIC, UPV/EHU), Leioa, Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - Ewan P Ramsay
- Division of Structural Biology, The Institute of Cancer Research, London, UK
- Fondazione Human Technopole, Structural Biology Research Centre, Milan, Italy
| | | | - Jean-Clement Mars
- Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Quebec, Canada
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Québec, Canada
- Borden Laboratory, IRIC, Université de Montréal, Montréal, Québec, Canada
| | - Torben Fürtges
- Protein Crystallography, Department of Biophysics, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Astrid Bruckmann
- Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
| | - Till Rudack
- Protein Crystallography, Department of Biophysics, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Carrie Bernecky
- Institute of Science and Technology, Klosterneuburg, Austria
| | - Valérie Lamour
- Université de Strasbourg, CNRS, INSERM, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Department of Integrated Structural Biology, Illkirch, France
- Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | - Konstantin Panov
- School of Biological Sciences and PGJCCR, Queen’s University Belfast, Belfast, UK
| | - Alessandro Vannini
- Division of Structural Biology, The Institute of Cancer Research, London, UK
- Fondazione Human Technopole, Structural Biology Research Centre, Milan, Italy
| | - Tom Moss
- Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Quebec, Canada
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Québec, Canada
| | - Christoph Engel
- Regensburg Center for Biochemistry, University of Regensburg, Regensburg, Germany
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3
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Papapietro O, Nejentsev S. Topoisomerase 2β and DNA topology during B cell development. Front Immunol 2022; 13:982870. [PMID: 36045673 PMCID: PMC9423374 DOI: 10.3389/fimmu.2022.982870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 07/25/2022] [Indexed: 11/13/2022] Open
Abstract
Topoisomerase 2β (TOP2B) introduces transient double strand breaks in the DNA helix to remove supercoiling structures and unwind entangled DNA strains. Advances in genomic technologies have enabled the discovery of novel functions for TOP2B in processes such as releasing of the paused RNA polymerase II and maintaining the genome organization through DNA loop domains. Thus, TOP2B can regulate transcription directly by acting on transcription elongation and indirectly by controlling interactions between enhancer and promoter regions through genome folding. The identification of TOP2B mutations in humans unexpectedly revealed a unique role of TOP2B in B-cell progenitors. Here we discuss the functions of TOP2B and the mechanisms leading to the B-cell development defect in patients with TOP2B deficiency.
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Affiliation(s)
- Olivier Papapietro
- Molecular Cell Biology and Immunology, Amsterdam University Medical Centers (UMC), Vrije Universiteit Amsterdam, Amsterdam, Netherlands
- Amsterdam Infection and Immunity, Infectious Diseases, Amsterdam, Netherlands
- *Correspondence: Sergey Nejentsev, ; Olivier Papapietro,
| | - Sergey Nejentsev
- Molecular Cell Biology and Immunology, Amsterdam University Medical Centers (UMC), Vrije Universiteit Amsterdam, Amsterdam, Netherlands
- Amsterdam Infection and Immunity, Infectious Diseases, Amsterdam, Netherlands
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
- *Correspondence: Sergey Nejentsev, ; Olivier Papapietro,
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4
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Kyung J, Jeon M, Lee I. Recent advances in the chromatin-based mechanism of FLOWERING LOCUS C repression through autonomous pathway genes. FRONTIERS IN PLANT SCIENCE 2022; 13:964931. [PMID: 36035698 PMCID: PMC9411803 DOI: 10.3389/fpls.2022.964931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 07/19/2022] [Indexed: 06/15/2023]
Abstract
Proper timing of flowering, a phase transition from vegetative to reproductive development, is crucial for plant fitness. The floral repressor FLOWERING LOCUS C (FLC) is the major determinant of flowering in Arabidopsis thaliana. In rapid-cycling A. thaliana accessions, which bloom rapidly, FLC is constitutively repressed by autonomous pathway (AP) genes, regardless of photoperiod. Diverse AP genes have been identified over the past two decades, and most of them repress FLC through histone modifications. However, the detailed mechanism underlying such modifications remains unclear. Several recent studies have revealed novel mechanisms to control FLC repression in concert with histone modifications. This review summarizes the latest advances in understanding the novel mechanisms by which AP proteins regulate FLC repression, including changes in chromatin architecture, RNA polymerase pausing, and liquid-liquid phase separation- and ncRNA-mediated gene silencing. Furthermore, we discuss how each mechanism is coupled with histone modifications in FLC chromatin.
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Affiliation(s)
- Jinseul Kyung
- School of Biological Sciences, Seoul National University, Seoul, South Korea
- Research Center for Plant Plasticity, Seoul National University, Seoul, South Korea
| | - Myeongjune Jeon
- School of Biological Sciences, Seoul National University, Seoul, South Korea
- Research Center for Plant Plasticity, Seoul National University, Seoul, South Korea
| | - Ilha Lee
- School of Biological Sciences, Seoul National University, Seoul, South Korea
- Research Center for Plant Plasticity, Seoul National University, Seoul, South Korea
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5
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Chen J, Huang Y, Zhang K. The DEAD-Box Protein Rok1 Coordinates Ribosomal RNA Processing in Association with Rrp5 in Drosophila. Int J Mol Sci 2022; 23:ijms23105685. [PMID: 35628496 PMCID: PMC9146779 DOI: 10.3390/ijms23105685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 05/09/2022] [Accepted: 05/17/2022] [Indexed: 02/04/2023] Open
Abstract
Ribosome biogenesis and processing involve the coordinated action of many components. The DEAD-box RNA helicase (Rok1) is essential for cell viability, and the depletion of Rok1 inhibits pre-rRNA processing. Previous research on Rok1 and its cofactor Rrp5 has been performed primarily in yeast. Few functional studies have been performed in complex multicellular eukaryotes. Here, we used a combination of genetics and developmental experiments to show that Rok1 and Rrp5, which localize to the nucleolus, play key roles in the pre-rRNA processing and ribosome assembly in D. melanogaster. The accumulation of pre-rRNAs caused by Rok1 depletion can result in developmental defects. The loss of Rok1 enlarged the nucleolus and led to stalled ribosome assembly and pre-rRNA processing in the nucleolus, thereby blocking rRNA maturation and exacerbating the inhibition of mitosis in the brain. We also discovered that rrp54-2/4-2 displayed significantly increased ITS1 signaling by fluorescence in situ hybridization, and a reduction in ITS2. Rrp5 signal was highly enriched in the core of the nucleolus in the rok1167/167 mutant, suggesting that Rok1 is required for the accurate cellular localization of Rrp5 in the nucleolus. We have thus uncovered functions of Rok1 that reveal important implications for ribosome processing in eukaryotes.
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Affiliation(s)
- Jie Chen
- Guangdong Provincial Key Laboratory of High Technology for Plant Protection, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China;
- Correspondence: (J.C.); (Y.H.); Tel.: +86-20-87597440 (J.C.)
| | - Yuantai Huang
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China;
- Correspondence: (J.C.); (Y.H.); Tel.: +86-20-87597440 (J.C.)
| | - Kang Zhang
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China;
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6
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Morovicz AP, Mazloumi Gavgani F, Jacobsen RG, Skuseth Slinning M, Turcu DC, Lewis AE. Phosphoinositide 3-kinase signalling in the nucleolus. Adv Biol Regul 2021; 83:100843. [PMID: 34920983 DOI: 10.1016/j.jbior.2021.100843] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 11/20/2021] [Indexed: 12/26/2022]
Abstract
The phosphoinositide 3-kinase (PI3K) signalling pathway plays key roles in many cellular processes and is altered in many diseases. The function and mode of action of the pathway have mostly been elucidated in the cytoplasm. However, many of the components of the PI3K pathway are also present in the nucleus at specific sub-nuclear sites including nuclear speckles, nuclear lipid islets and the nucleolus. Nucleoli are membrane-less subnuclear structures where ribosome biogenesis occurs. Processes leading to ribosome biogenesis are tightly regulated to maintain protein translation capacity of cells. This review focuses on nucleolar PI3K signalling and how it regulates rRNA synthesis, as well as on the identification of downstream phosphatidylinositol (3,4,5)trisphosphate effector proteins.
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Affiliation(s)
| | | | - Rhîan G Jacobsen
- Department of Biological Sciences, University of Bergen, 5008, Bergen, Norway
| | | | - Diana C Turcu
- Department of Biological Sciences, University of Bergen, 5008, Bergen, Norway
| | - Aurélia E Lewis
- Department of Biological Sciences, University of Bergen, 5008, Bergen, Norway.
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7
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Wang T, Li J, Yang L, Wu M, Ma Q. The Role of Long Non-coding RNAs in Human Imprinting Disorders: Prospective Therapeutic Targets. Front Cell Dev Biol 2021; 9:730014. [PMID: 34760887 PMCID: PMC8573313 DOI: 10.3389/fcell.2021.730014] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 09/23/2021] [Indexed: 12/26/2022] Open
Abstract
Genomic imprinting is a term used for an intergenerational epigenetic inheritance and involves a subset of genes expressed in a parent-of-origin-dependent way. Imprinted genes are expressed preferentially from either the paternally or maternally inherited allele. Long non-coding RNAs play essential roles in regulating this allele-specific expression. In several well-studied imprinting clusters, long non-coding RNAs have been found to be essential in regulating temporal- and spatial-specific establishment and maintenance of imprinting patterns. Furthermore, recent insights into the epigenetic pathological mechanisms underlying human genomic imprinting disorders suggest that allele-specific expressed imprinted long non-coding RNAs serve as an upstream regulator of the expression of other protein-coding or non-coding imprinted genes in the same cluster. Aberrantly expressed long non-coding RNAs result in bi-allelic expression or silencing of neighboring imprinted genes. Here, we review the emerging roles of long non-coding RNAs in regulating the expression of imprinted genes, especially in human imprinting disorders, and discuss three strategies targeting the central long non-coding RNA UBE3A-ATS for the purpose of developing therapies for the imprinting disorders Prader-Willi syndrome and Angelman syndrome. In summary, a better understanding of long non-coding RNA-related mechanisms is key to the development of potential therapeutic targets for human imprinting disorders.
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Affiliation(s)
- Tingxuan Wang
- Shenzhen Key Laboratory of Synthetic Genomics, Guangdong Provincial Key Laboratory of Synthetic Genomics, CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Jianjian Li
- Shenzhen Key Laboratory of Synthetic Genomics, Guangdong Provincial Key Laboratory of Synthetic Genomics, CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Liuyi Yang
- Shenzhen Key Laboratory of Synthetic Genomics, Guangdong Provincial Key Laboratory of Synthetic Genomics, CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Manyin Wu
- Shenzhen Key Laboratory of Synthetic Genomics, Guangdong Provincial Key Laboratory of Synthetic Genomics, CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Qing Ma
- Shenzhen Key Laboratory of Synthetic Genomics, Guangdong Provincial Key Laboratory of Synthetic Genomics, CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
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8
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The Ribosomal Gene Loci-The Power behind the Throne. Genes (Basel) 2021; 12:genes12050763. [PMID: 34069807 PMCID: PMC8157237 DOI: 10.3390/genes12050763] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 05/12/2021] [Accepted: 05/14/2021] [Indexed: 12/20/2022] Open
Abstract
Nucleoli form around actively transcribed ribosomal RNA (rRNA) genes (rDNA), and the morphology and location of nucleolus-associated genomic domains (NADs) are linked to the RNA Polymerase I (Pol I) transcription status. The number of rDNA repeats (and the proportion of actively transcribed rRNA genes) is variable between cell types, individuals and disease state. Substantial changes in nucleolar morphology and size accompanied by concomitant changes in the Pol I transcription rate have long been documented during normal cell cycle progression, development and malignant transformation. This demonstrates how dynamic the nucleolar structure can be. Here, we will discuss how the structure of the rDNA loci, the nucleolus and the rate of Pol I transcription are important for dynamic regulation of global gene expression and genome stability, e.g., through the modulation of long-range genomic interactions with the suppressive NAD environment. These observations support an emerging paradigm whereby the rDNA repeats and the nucleolus play a key regulatory role in cellular homeostasis during normal development as well as disease, independent of their role in determining ribosome capacity and cellular growth rates.
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9
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Zhou Y, Bastian IN, Long MD, Dow M, Li W, Liu T, Ngu RK, Antonucci L, Huang JY, Phung QT, Zhao XH, Banerjee S, Lin XJ, Wang H, Dang B, Choi S, Karin D, Su H, Ellisman MH, Jamieson C, Bosenberg M, Cheng Z, Haybaeck J, Kenner L, Fisch KM, Bourgon R, Hernandez G, Lill JR, Liu S, Carter H, Mellman I, Karin M, Shalapour S. Activation of NF-κB and p300/CBP potentiates cancer chemoimmunotherapy through induction of MHC-I antigen presentation. Proc Natl Acad Sci U S A 2021; 118:e2025840118. [PMID: 33602823 PMCID: PMC7923353 DOI: 10.1073/pnas.2025840118] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Many cancers evade immune rejection by suppressing major histocompatibility class I (MHC-I) antigen processing and presentation (AgPP). Such cancers do not respond to immune checkpoint inhibitor therapies (ICIT) such as PD-1/PD-L1 [PD-(L)1] blockade. Certain chemotherapeutic drugs augment tumor control by PD-(L)1 inhibitors through potentiation of T-cell priming but whether and how chemotherapy enhances MHC-I-dependent cancer cell recognition by cytotoxic T cells (CTLs) is not entirely clear. We now show that the lysine acetyl transferases p300/CREB binding protein (CBP) control MHC-I AgPPM expression and neoantigen amounts in human cancers. Moreover, we found that two distinct DNA damaging drugs, the platinoid oxaliplatin and the topoisomerase inhibitor mitoxantrone, strongly up-regulate MHC-I AgPP in a manner dependent on activation of nuclear factor kappa B (NF-κB), p300/CBP, and other transcription factors, but independently of autocrine IFNγ signaling. Accordingly, NF-κB and p300 ablations prevent chemotherapy-induced MHC-I AgPP and abrogate rejection of low MHC-I-expressing tumors by reinvigorated CD8+ CTLs. Drugs like oxaliplatin and mitoxantrone may be used to overcome resistance to PD-(L)1 inhibitors in tumors that had "epigenetically down-regulated," but had not permanently lost MHC-I AgPP activity.
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Affiliation(s)
- Yixuan Zhou
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
| | - Ingmar Niels Bastian
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
| | - Mark D Long
- Department of Biostatistics and Bioinformatics, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14263
| | - Michelle Dow
- Division of Medical Genetics, Health Sciences, Department of Biomedical Informatics, University of California San Diego, La Jolla, CA 92093
- Department of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Weihua Li
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
- Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Tao Liu
- Department of Biostatistics and Bioinformatics, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14263
| | - Rachael Katie Ngu
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
| | - Laura Antonucci
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
- Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Jian Yu Huang
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
- Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Qui T Phung
- Department of Microchemistry, Proteomics, and Lipidomics, Genentech, Inc., South San Francisco, CA 94080
| | - Xi-He Zhao
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
- Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093
- Oncology Department, China Medical University Shengjing Hospital, 110004 Shenyang City, China
| | - Sourav Banerjee
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
- Department of Cellular Medicine, Jacqui Wood Cancer Centre, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Xue-Jia Lin
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
- Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093
- Biomedical Translational Research Institute and the First Affiliated Hospital, Jinan University, 510632 Guangzhou, Guangdong, China
| | - Hongxia Wang
- State Key Laboratory of Proteomics, Institute of Basic Medical Sciences, National Center of Biomedical Analysis, 100850 Beijing, China
| | - Brian Dang
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
- Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Sylvia Choi
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
- Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Daniel Karin
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
| | - Hua Su
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093
- Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Mark H Ellisman
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, CA 92093
| | - Christina Jamieson
- Department of Urology, Moores Cancer Center, University of California San Diego, La Jolla, CA 92093
| | - Marcus Bosenberg
- Department of Immunobiology, Yale School of Medicine, New Haven, CT 06510
- Department of Dermatology, Yale School of Medicine, New Haven, CT 06510
| | - Zhang Cheng
- Center for Epigenomics, Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Johannes Haybaeck
- Institute of Pathology, Medical University of Graz, A-8036 Graz, Austria
- Department of Pathology, Neuropathology and Molecular Pathology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Lukas Kenner
- Department of Pathology, Christian Doppler Laboratory, Medical University of Vienna, 1090 Vienna, Austria
- Unit of Pathology of Laboratory Animals, University of Veterinary Medicine Vienna, 1210 Vienna, Austria
| | - Kathleen M Fisch
- Center for Computational Biology and Bioinformatics, Department of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Richard Bourgon
- Department of Cancer Immunology, Genentech, Inc., South San Francisco, CA 94080
| | - Genevive Hernandez
- Department of Cancer Immunology, Genentech, Inc., South San Francisco, CA 94080
| | - Jennie R Lill
- Department of Microchemistry, Proteomics, and Lipidomics, Genentech, Inc., South San Francisco, CA 94080
| | - Song Liu
- Department of Biostatistics and Bioinformatics, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14263
| | - Hannah Carter
- Division of Medical Genetics, Health Sciences, Department of Biomedical Informatics, University of California San Diego, La Jolla, CA 92093
- Department of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Ira Mellman
- Department of Cancer Immunology, Genentech, Inc., South San Francisco, CA 94080
| | - Michael Karin
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093;
- Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA 92093
| | - Shabnam Shalapour
- Department of Pharmacology, School of Medicine, University of California San Diego, CA 92093;
- Department of Cancer Biology, University of Texas MD Anderson Cancer Center, Houston, TX 77054
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10
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Sims J, Rabanal FA, Elgert C, von Haeseler A, Schlögelhofer P. It Is Just a Matter of Time: Balancing Homologous Recombination and Non-homologous End Joining at the rDNA Locus During Meiosis. FRONTIERS IN PLANT SCIENCE 2021; 12:773052. [PMID: 34777453 PMCID: PMC8580885 DOI: 10.3389/fpls.2021.773052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 10/04/2021] [Indexed: 05/17/2023]
Abstract
Ribosomal RNA genes (rDNAs) are located in large domains of hundreds of rDNA units organized in a head-to-tail manner. The proper and stable inheritance of rDNA clusters is of paramount importance for survival. Yet, these highly repetitive elements pose a potential risk to the genome since they can undergo non-allelic exchanges. Here, we review the current knowledge of the organization of the rDNA clusters in Arabidopsis thaliana and their stability during meiosis. Recent findings suggest that during meiosis, all rDNA loci are embedded within the nucleolus favoring non-homologous end joining (NHEJ) as a repair mechanism, while DNA repair via homologous recombination (HR) appears to be a rare event. We propose a model where (1) frequent meiotic NHEJ events generate abundant single nucleotide polymorphisms and insertions/deletions within the rDNA, resulting in a heterogeneous population of rDNA units and (2) rare HR events dynamically change rDNA unit numbers, only to be observed in large populations over many generations. Based on the latest efforts to delineate the entire rDNA sequence in A. thaliana, we discuss evidence supporting this model. The results compiled so far draw a surprising picture of rDNA sequence heterogeneity between individual units. Furthermore, rDNA cluster sizes have been recognized as relatively stable when observing less than 10 generations, yet emerged as major determinant of genome size variation between different A. thaliana ecotypes. The sequencing efforts also revealed that transcripts from the diverse rDNA units yield heterogenous ribosome populations with potential functional implications. These findings strongly motivate further research to understand the mechanisms that maintain the metastable state of rDNA loci.
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Affiliation(s)
- Jason Sims
- Department of Chromosome Biology, Max Perutz Labs, University of Vienna, Vienna BioCenter, Vienna, Austria
- *Correspondence: Jason Sims,
| | - Fernando A. Rabanal
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Christiane Elgert
- Center for Integrative Bioinformatics Vienna (CIBIV), Max Perutz Labs, University of Vienna and Medical University of Vienna, Vienna BioCenter, Vienna, Austria
| | - Arndt von Haeseler
- Center for Integrative Bioinformatics Vienna (CIBIV), Max Perutz Labs, University of Vienna and Medical University of Vienna, Vienna BioCenter, Vienna, Austria
- Bioinformatics and Computational Biology, Faculty of Computer Science, University of Vienna, Vienna, Austria
| | - Peter Schlögelhofer
- Department of Chromosome Biology, Max Perutz Labs, University of Vienna, Vienna BioCenter, Vienna, Austria
- Peter Schlögelhofer,
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11
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Al-Natour Z, Chalissery J, Hassan AH. Fun30 chromatin remodeler helps in dealing with torsional stress and camptothecin-induced DNA damage. Yeast 2020; 38:170-182. [PMID: 33141948 DOI: 10.1002/yea.3534] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Revised: 10/04/2020] [Accepted: 10/26/2020] [Indexed: 12/19/2022] Open
Abstract
Fun30 is an ATP-dependent chromatin remodeler in budding yeast that is involved in cellular processes important for maintaining genomic stability such as gene silencing and DNA damage repair. Cells lacking Fun30 are moderately sensitive to the topoisomerase inhibitor camptothecin and exhibit a delay in cell cycle progression in the presence of camptothecin. Here, we show that Fun30 is required to cope with torsional stress in the absence of Top1. Moreover, we show through genetic studies that Fun30 acts in a parallel pathway to Mus81 endonuclease but is epistatic to Tdp1 phosphodiesterase and Rad1 endonuclease in the repair of camptothecin-induced DNA damage. More importantly, we show that DNA damage sensitivity of Fun30 deficient cells is enhanced in the absence of RNase H enzymes that remove RNA:DNA hybrids. We believe that chromatin remodeling by Fun30 may be important in dealing with torsional stress and camptothecin-induced DNA damage.
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Affiliation(s)
- Zeina Al-Natour
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Jisha Chalissery
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Ahmed H Hassan
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
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12
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The RNA polymerase I transcription inhibitor CX-5461 cooperates with topoisomerase 1 inhibition by enhancing the DNA damage response in homologous recombination-proficient high-grade serous ovarian cancer. Br J Cancer 2020; 124:616-627. [PMID: 33173151 PMCID: PMC7851142 DOI: 10.1038/s41416-020-01158-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 10/05/2020] [Accepted: 10/22/2020] [Indexed: 02/08/2023] Open
Abstract
Background Intrinsic and acquired drug resistance represent fundamental barriers to the cure of high-grade serous ovarian carcinoma (HGSC), the most common histological subtype accounting for the majority of ovarian cancer deaths. Defects in homologous recombination (HR) DNA repair are key determinants of sensitivity to chemotherapy and poly-ADP ribose polymerase inhibitors. Restoration of HR is a common mechanism of acquired resistance that results in patient mortality, highlighting the need to identify new therapies targeting HR-proficient disease. We have shown promise for CX-5461, a cancer therapeutic in early phase clinical trials, in treating HR-deficient HGSC. Methods Herein, we screen the whole protein-coding genome to identify potential targets whose depletion cooperates with CX-5461 in HR-proficient HGSC. Results We demonstrate robust proliferation inhibition in cells depleted of DNA topoisomerase 1 (TOP1). Combining the clinically used TOP1 inhibitor topotecan with CX-5461 potentiates a G2/M cell cycle checkpoint arrest in multiple HR-proficient HGSC cell lines. The combination enhances a nucleolar DNA damage response and global replication stress without increasing DNA strand breakage, significantly reducing clonogenic survival and tumour growth in vivo. Conclusions Our findings highlight the possibility of exploiting TOP1 inhibition to be combined with CX-5461 as a non-genotoxic approach in targeting HR-proficient HGSC.
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13
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Cerritelli SM, El Hage A. RNases H1 and H2: guardians of the stability of the nuclear genome when supply of dNTPs is limiting for DNA synthesis. Curr Genet 2020; 66:1073-1084. [PMID: 32886170 DOI: 10.1007/s00294-020-01086-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 05/30/2020] [Accepted: 06/01/2020] [Indexed: 11/29/2022]
Abstract
RNA/DNA hybrids are processed by RNases H1 and H2, while single ribonucleoside-monophosphates (rNMPs) embedded in genomic DNA are removed by the error-free, RNase H2-dependent ribonucleotide excision repair (RER) pathway. In the absence of RER, however, topoisomerase 1 (Top1) can cleave single genomic rNMPs in a mutagenic manner. In RNase H2-deficient mice, the accumulation of genomic rNMPs above a threshold of tolerance leads to catastrophic genomic instability that causes embryonic lethality. In humans, deficiencies in RNase H2 induce the autoimmune disorders Aicardi-Goutières syndrome and systemic lupus erythematosus, and cause skin and intestinal cancers. Recently, we reported that in Saccharomyces cerevisiae, the depletion of Rnr1, the major catalytic subunit of ribonucleotide reductase (RNR), which converts ribonucleotides to deoxyribonucleotides, leads to cell lethality in absence of RNases H1 and H2. We hypothesized that under replicative stress and compromised DNA repair that are elicited by an insufficient supply of deoxyribonucleoside-triphosphates (dNTPs), cells cannot survive the accumulation of persistent RNA/DNA hybrids. Remarkably, we found that cells lacking RNase H2 accumulate ~ 5-fold more genomic rNMPs in absence than in presence of Rnr1. When the load of genomic rNMPs is further increased in the presence of a replicative DNA polymerase variant that over-incorporates rNMPs in leading or lagging strand, cells missing both Rnr1 and RNase H2 suffer from severe growth defects. These are reversed in absence of Top1. Thus, in cells lacking RNase H2 and containing a limiting supply of dNTPs, there is a threshold of tolerance for the accumulation of genomic ribonucleotides that is tightly associated with Top1-mediated DNA damage. In this mini-review, we describe the implications of the loss of RNase H2, or RNases H1 and H2, on the integrity of the nuclear genome and viability of budding yeast cells that are challenged with a critically low supply of dNTPs. We further propose that our findings in budding yeast could pave the way for the study of the potential role of mammalian RNR in RNase H2-related diseases.
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Affiliation(s)
- Susana M Cerritelli
- SFR, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Aziz El Hage
- The Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh, UK.
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14
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Bjelogrlić SK, Todorović TR, Kojić M, Senćanski M, Nikolić M, Višnjevac A, Araškov J, Miljković M, Muller CD, Filipović NR. Pd(II) complexes with N-heteroaromatic hydrazone ligands: Anticancer activity, in silico and experimental target identification. J Inorg Biochem 2019; 199:110758. [PMID: 31299379 DOI: 10.1016/j.jinorgbio.2019.110758] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 06/19/2019] [Accepted: 06/25/2019] [Indexed: 01/08/2023]
Abstract
Anticancer activity of Pd complexes 1-5 with bidentate N-heteroaromatic hydrazone ligands was investigated on human acute monocytic leukemia (THP-1; cells in a suspension) and human mammary adenocarcinoma (MCF-7; two-dimensional layer and three-dimensional spheroid tumor model) cell lines. For the Pd(II) complexes with condensation products of ethyl hydrazainoacetate and quinoline-8-carboxaldehyde (complex 1) and 2-formylpyridine (complex 3), for which apoptosis was determined as a mechanism of anticancer activity, further investigation revealed that they arrest the cell cycle in G0/G1 phase, induce generation of reactive oxygen species and inhibit Topoisomerase I in vitro. In silico studies corroborate experimental findings that these complexes show topoisomerase inhibition activity in the micromolar range and indicate binding to a DNA's minor groove as another potential target. Based on the results obtained by circular dichroism and fluorescence spectroscopy measurements, the most active complexes are suitable to be delivered to a blood stream via human serum albumin.
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Affiliation(s)
- Snežana K Bjelogrlić
- National Cancer Research Center of Serbia, Pasterova 14, 11000 Belgrade, Serbia; Institut Pluridisciplinaire Hubert Curien, UMR 7178 CNRS Université de Strasbourg, 67401 Illkirch, France
| | - Tamara R Todorović
- University of Belgrade, Faculty of Chemistry, Studentski trg 12-16, 11000 Belgrade, Serbia
| | - Milan Kojić
- Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, V. Stepe 444a, P.O. Box 23, 11010 Belgrade, Serbia
| | - Milan Senćanski
- Center for Multidisciplinary Research, Institute of Nuclear Sciences "Vinča", University of Belgrade, 11000 Belgrade, Serbia
| | - Milan Nikolić
- University of Belgrade, Faculty of Chemistry, Studentski trg 12-16, 11000 Belgrade, Serbia
| | - Aleksandar Višnjevac
- Physical Chemistry Division, Ruđer Bošković Institute, Bijenička c. 54, HR-10000 Zagreb, Croatia
| | - Jovana Araškov
- University of Belgrade, Faculty of Chemistry, Studentski trg 12-16, 11000 Belgrade, Serbia
| | - Marija Miljković
- Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, V. Stepe 444a, P.O. Box 23, 11010 Belgrade, Serbia
| | - Christian D Muller
- Institut Pluridisciplinaire Hubert Curien, UMR 7178 CNRS Université de Strasbourg, 67401 Illkirch, France
| | - Nenad R Filipović
- Faculty of Agriculture, University of Belgrade, Nemanjina 6, 11000 Belgrade, Serbia.
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15
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Hegedüs É, Kókai E, Nánási P, Imre L, Halász L, Jossé R, Antunovics Z, Webb MR, El Hage A, Pommier Y, Székvölgyi L, Dombrádi V, Szabó G. Endogenous single-strand DNA breaks at RNA polymerase II promoters in Saccharomyces cerevisiae. Nucleic Acids Res 2019; 46:10649-10668. [PMID: 30445637 PMCID: PMC6237785 DOI: 10.1093/nar/gky743] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 08/16/2018] [Indexed: 12/12/2022] Open
Abstract
Molecular combing and gel electrophoretic studies revealed endogenous nicks with free 3'OH ends at ∼100 kb intervals in the genomic DNA (gDNA) of unperturbed and G1-synchronized Saccharomyces cerevisiae cells. Analysis of the distribution of endogenous nicks by Nick ChIP-chip indicated that these breaks accumulated at active RNA polymerase II (RNAP II) promoters, reminiscent of the promoter-proximal transient DNA breaks of higher eukaryotes. Similar periodicity of endogenous nicks was found within the ribosomal rDNA cluster, involving every ∼10th of the tandemly repeated 9.1 kb units of identical sequence. Nicks were mapped by Southern blotting to a few narrow regions within the affected units. Three of them were overlapping the RNAP II promoters, while the ARS-containing IGS2 region was spared of nicks. By using a highly sensitive reverse-Southwestern blot method to map free DNA ends with 3'OH, nicks were shown to be distinct from other known rDNA breaks and linked to the regulation of rDNA silencing. Nicks in rDNA and the rest of the genome were typically found at the ends of combed DNA molecules, occasionally together with R-loops, comprising a major pool of vulnerable sites that are connected with transcriptional regulation.
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Affiliation(s)
- Éva Hegedüs
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Endre Kókai
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Péter Nánási
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - László Imre
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - László Halász
- MTA-DE Momentum Genome Architecture and Recombination Research Group, Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Rozenn Jossé
- Developmental Therapeutics Branch and Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute (CCR-NCI), NIH, Bethesda, MD, USA
| | - Zsuzsa Antunovics
- Department of Genetics and Applied Microbiology, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary
| | | | - Aziz El Hage
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, UK
| | - Yves Pommier
- Developmental Therapeutics Branch and Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute (CCR-NCI), NIH, Bethesda, MD, USA
| | - Lóránt Székvölgyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,MTA-DE Momentum Genome Architecture and Recombination Research Group, Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Viktor Dombrádi
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Gábor Szabó
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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16
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Choubey S, Kondev J, Sanchez A. Distribution of Initiation Times Reveals Mechanisms of Transcriptional Regulation in Single Cells. Biophys J 2019; 114:2072-2082. [PMID: 29742401 DOI: 10.1016/j.bpj.2018.03.031] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 03/18/2018] [Accepted: 03/29/2018] [Indexed: 11/25/2022] Open
Abstract
Transcription is the dominant point of control of gene expression. Biochemical studies have revealed key molecular components of transcription and their interactions, but the dynamics of transcription initiation in cells is still poorly understood. This state of affairs is being remedied with experiments that observe transcriptional dynamics in single cells using fluorescent reporters. Quantitative information about transcription initiation dynamics can also be extracted from experiments that use electron micrographs of RNA polymerases caught in the act of transcribing a gene (Miller spreads). Inspired by these data, we analyze a general stochastic model of transcription initiation and elongation and compute the distribution of transcription initiation times. We show that different mechanisms of initiation leave distinct signatures in the distribution of initiation times that can be compared to experiments. We analyze published data from micrographs of RNA polymerases transcribing ribosomal RNA genes in Escherichia coli and compare the observed distributions of interpolymerase distances with the predictions from previously hypothesized mechanisms for the regulation of these genes. Our analysis demonstrates the potential of measuring the distribution of time intervals between initiation events as a probe for dissecting mechanisms of transcription initiation in live cells.
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Affiliation(s)
- Sandeep Choubey
- Department of Physics, Brandeis University, Waltham, Massachusetts
| | - Jane Kondev
- Department of Physics, Brandeis University, Waltham, Massachusetts
| | - Alvaro Sanchez
- Rowland Institute at Harvard, Harvard University, Cambridge, Massachusetts; Department of Ecology and Evolutionary Biology, Microbial Sciences Institute, Yale University, New Haven, Connecticut.
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17
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Albert B, Kos-Braun IC, Henras AK, Dez C, Rueda MP, Zhang X, Gadal O, Kos M, Shore D. A ribosome assembly stress response regulates transcription to maintain proteome homeostasis. eLife 2019; 8:45002. [PMID: 31124783 PMCID: PMC6579557 DOI: 10.7554/elife.45002] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 05/23/2019] [Indexed: 12/13/2022] Open
Abstract
Ribosome biogenesis is a complex and energy-demanding process requiring tight coordination of ribosomal RNA (rRNA) and ribosomal protein (RP) production. Given the extremely high level of RP synthesis in rapidly growing cells, alteration of any step in the ribosome assembly process may impact growth by leading to proteotoxic stress. Although the transcription factor Hsf1 has emerged as a central regulator of proteostasis, how its activity is coordinated with ribosome biogenesis is unknown. Here, we show that arrest of ribosome biogenesis in the budding yeast Saccharomyces cerevisiae triggers rapid activation of a highly specific stress pathway that coordinately upregulates Hsf1 target genes and downregulates RP genes. Activation of Hsf1 target genes requires neo-synthesis of RPs, which accumulate in an insoluble fraction and presumably titrate a negative regulator of Hsf1, the Hsp70 chaperone. RP aggregation is also coincident with that of the RP gene activator Ifh1, a transcription factor that is rapidly released from RP gene promoters. Our data support a model in which the levels of newly synthetized RPs, imported into the nucleus but not yet assembled into ribosomes, work to continuously balance Hsf1 and Ifh1 activity, thus guarding against proteotoxic stress during ribosome assembly. When yeast cells are growing at top speed, they can make 2,000 new ribosomes every minute. These enormous molecular assemblies are the protein-making machines of the cell. Building new ribosomes is one of the most energy-demanding parts of cell growth and, if the process goes wrong, the results can be catastrophic. The proteins that make up the ribosomes themselves are sticky. Left unattended, they start to form toxic clumps inside the compartment that houses most of the cell’s DNA, the nucleus. A protein called Heat shock factor 1, or Hsf1 for short, plays an important role in the cell's quality control systems. It helps to manage sticky proteins by switching on genes that break down protein clumps and prevent new clumps from forming. Hsf1 levels start to rise whenever cells are struggling to keep up with protein production. If it is half-finished ribosomes that are causing the problem, cells can stop making ribosome proteins. The protein in charge of this in yeast is Ifh1. It is a transcription factor that sits at the front of the genes for ribosome proteins, switching them on. When yeast cells get stressed, Ifh1 drops away from the genes within minutes, switching them off again. Yet how this happens, and how it links to Hsf1, is a mystery. To start to provide some answers, Albert et al. disrupted the production of ribosomes in yeast cells and examined the consequences. This revealed a new rescue response, that they named the “ribosome assembly stress response”. Both Hsf1 and Ifh1 are sensitive to the build-up of unfinished ribosomes in the nucleus. As expected, Hsf1 activated when ribosome proteins started to build up, and switched on the genes needed to manage the protein clumps. The effect on Isfh1, however, was unexpected. When the unassembled ribosome proteins started to build up, it was the clumps themselves that pulled the Ifh1 proteins off the genes. The unassembled ribosomes proteins seemed to be stopping their own production. Low levels of clumped ribosome proteins in the nuclei of unstressed cells also helped to keep Hsf1 active and pull Ifh1 off the ribosome genes. It is possible that this provides continual protection against a toxic protein build-up. These findings are not only important for understanding yeast cells; cancer cells also need to produce ribosomes at a very high rate to sustain their rapid growth. They too might be prone to stresses that interrupt their ribosome assembly. As such, understanding more about this process could one day lead to new therapies to target cancer cells.
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Affiliation(s)
- Benjamin Albert
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), Geneva, Switzerland
| | | | - Anthony K Henras
- Centre de Biologie Intégrative, Université Paul Sabatier, Toulouse, France
| | - Christophe Dez
- Centre de Biologie Intégrative, Université Paul Sabatier, Toulouse, France
| | - Maria Paula Rueda
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), Geneva, Switzerland
| | - Xu Zhang
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), Geneva, Switzerland
| | - Olivier Gadal
- Centre de Biologie Intégrative, Université Paul Sabatier, Toulouse, France
| | - Martin Kos
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - David Shore
- Department of Molecular Biology, Institute of Genetics and Genomics of Geneva (iGE3), Geneva, Switzerland
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18
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Abstract
Genome replication involves dealing with obstacles that can result from DNA damage but also from chromatin alterations, topological stress, tightly bound proteins or non-B DNA structures such as R loops. Experimental evidence reveals that an engaged transcription machinery at the DNA can either enhance such obstacles or be an obstacle itself. Thus, transcription can become a potentially hazardous process promoting localized replication fork hindrance and stress, which would ultimately cause genome instability, a hallmark of cancer cells. Understanding the causes behind transcription-replication conflicts as well as how the cell resolves them to sustain genome integrity is the aim of this review.
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19
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Potapova TA, Gerton JL. Ribosomal DNA and the nucleolus in the context of genome organization. Chromosome Res 2019; 27:109-127. [PMID: 30656516 DOI: 10.1007/s10577-018-9600-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 12/13/2018] [Accepted: 12/17/2018] [Indexed: 12/12/2022]
Abstract
The nucleolus constitutes a prominent nuclear compartment, a membraneless organelle that was first documented in the 1830s. The fact that specific chromosomal regions were present in the nucleolus was recognized by Barbara McClintock in the 1930s, and these regions were termed nucleolar organizing regions, or NORs. The primary function of ribosomal DNA (rDNA) is to produce RNA components of ribosomes. Yet, ribosomal DNA also plays a pivotal role in nuclear organization by assembling the nucleolus. This review is focused on the rDNA and associated proteins in the context of genome organization. Recent advances in understanding chromatin organization suggest that chromosomes are organized into topological domains by a DNA loop extrusion process. We discuss the perspective that rDNA may also be organized in topological domains constrained by structural maintenance of chromosome protein complexes such as cohesin and condensin. Moreover, biophysical studies indicate that the nucleolar compartment may be formed by active processes as well as phase separation, a perspective that lends further insight into nucleolar organization. The application of the latest perspectives and technologies to this organelle help further elucidate its role in nuclear structure and function.
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Affiliation(s)
| | - Jennifer L Gerton
- Stowers Institute for Medical Research, Kansas City, MO, USA
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, USA
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20
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Genome-wide Map of R-Loop-Induced Damage Reveals How a Subset of R-Loops Contributes to Genomic Instability. Mol Cell 2018; 71:487-497.e3. [PMID: 30078723 DOI: 10.1016/j.molcel.2018.06.037] [Citation(s) in RCA: 99] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 05/23/2018] [Accepted: 06/22/2018] [Indexed: 01/04/2023]
Abstract
DNA-RNA hybrids associated with R-loops promote DNA damage and genomic instability. The capacity of hybrids at different genomic sites to cause DNA damage was not known, and the mechanisms leading from hybrid to damage were poorly understood. Here, we adopt a new strategy to map and characterize the sites of hybrid-induced damage genome-wide in budding yeast. We show that hybrid removal is essential for life because persistent hybrids cause irreparable DNA damage and cell death. We identify that a subset of hybrids is prone to cause damage, and the chromosomal context of hybrids dramatically impacts their ability to induce damage. Furthermore, persistent hybrids affect the repair pathway, generating large regions of single-stranded DNA (ssDNA) by two distinct mechanisms, likely resection and re-replication. These damaged regions may act as potential precursors to gross chromosomal rearrangements like deletions and duplications that are associated with R-loops and cancers.
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21
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Leung AWY, Anantha M, Dragowska WH, Wehbe M, Bally MB. Copper-CX-5461: A novel liposomal formulation for a small molecule rRNA synthesis inhibitor. J Control Release 2018; 286:1-9. [PMID: 30016731 DOI: 10.1016/j.jconrel.2018.07.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 07/04/2018] [Accepted: 07/13/2018] [Indexed: 12/23/2022]
Abstract
CX-5461 is currently in Phase I/II clinical trials for advanced hematologic malignancies and triple negative or BRCA-deficient breast cancer. The compound is currently administered to patients intravenously (i.v.) at low pH (3.5) due to solubility challenges. Reliance of low pH to enhance solubility of CX-5461 can adversely impact pharmacokinetics, biodistribution and therapeutic potential. We have addressed this solubility issue through a formulation method that relies on the interactions between CX-5461 and copper. Copper binds CX-5461 through the nitrogens of the pyrazine ring. Here, we describe synthesizing this copper-complexed CX-5461 (Cu(CX-5461)) within liposomes. CX-5461 was added to copper-containing liposomes and incubated at 60 °C for 30 min. The pharmacokinetics of CX-5461 was assessed in mice following a single i.v. injection at 30 mg/kg. Efficacy studies were completed in multiple subcutaneous mouse xenografts as well as in a bone marrow engraftment model of acute myeloid leukemia (AML). The novel Cu(CX-5461) formulation was stable at pH 7.4 and exhibited increased plasma circulation longevity, increasing the total exposure to CX5461 by an order of magnitude. Cu(CX-5461) was more active than CX-5461 in AML models in vivo. In HCT116-B46 and Capan-1 solid tumour models that are BRCA-deficient, the Cu(CX-5461) formulation engendered activity that was comparable to that of the low pH CX-5461 formulation. We have generated the first Cu(CX-5461) formulation suitable for i.v. administration that is more efficacious than the existing low-pH formulation in pre-clinical models of AML. The Cu(CX-5461) formulation may serve as an alternative formulation for CX-5461 in BRCA-deficient cancers.
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Affiliation(s)
- Ada W Y Leung
- Experimental Therapeutics, BC Cancer Research Centre, 675 West 10th Avenue, Vancouver, BC V5Z 1L3, Canada; Department of Chemistry, University of British Columbia, Vancouver, BC, Canada; Cuprous Pharmaceuticals Inc., Vancouver, BC, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.
| | - Malathi Anantha
- Experimental Therapeutics, BC Cancer Research Centre, 675 West 10th Avenue, Vancouver, BC V5Z 1L3, Canada
| | - Wieslawa H Dragowska
- Experimental Therapeutics, BC Cancer Research Centre, 675 West 10th Avenue, Vancouver, BC V5Z 1L3, Canada
| | - Mohamed Wehbe
- Experimental Therapeutics, BC Cancer Research Centre, 675 West 10th Avenue, Vancouver, BC V5Z 1L3, Canada; Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Marcel B Bally
- Experimental Therapeutics, BC Cancer Research Centre, 675 West 10th Avenue, Vancouver, BC V5Z 1L3, Canada; Cuprous Pharmaceuticals Inc., Vancouver, BC, Canada; Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada; Centre for Drug Research and Development, Vancouver, BC, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada
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22
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Zaytseva O, Quinn LM. DNA Conformation Regulates Gene Expression: The MYC Promoter and Beyond. Bioessays 2018; 40:e1700235. [PMID: 29504137 DOI: 10.1002/bies.201700235] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 01/29/2018] [Indexed: 01/07/2023]
Abstract
Emerging evidence suggests that DNA topology plays an instructive role in cell fate control through regulation of gene expression. Transcription produces torsional stress, and the resultant supercoiling of the DNA molecule generates an array of secondary structures. In turn, local DNA architecture is harnessed by the cell, acting within sensory feedback mechanisms to mediate transcriptional output. MYC is a potent oncogene, which is upregulated in the majority of cancers; thus numerous studies have focused on detailed understanding of its regulation. Dissection of regulatory regions within the MYC promoter provided the first hint that intimate feedback between DNA topology and associated DNA remodeling proteins is critical for moderating transcription. As evidence of such regulation is also found in the context of many other genes, here we expand on the prototypical example of the MYC promoter, and also explore DNA architecture in a genome-wide context as a global mechanism of transcriptional control.
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Affiliation(s)
- Olga Zaytseva
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, ACT 2600, Canberra City, Australia.,School of Biomedical Sciences, University of Melbourne, 3010, Parkville, Australia
| | - Leonie M Quinn
- ACRF Department of Cancer Biology and Therapeutics, The John Curtin School of Medical Research, The Australian National University, ACT 2600, Canberra City, Australia.,School of Biomedical Sciences, University of Melbourne, 3010, Parkville, Australia
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23
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Abstract
During transcription, the nascent transcript behind an elongating RNA polymerase (RNAP) can invade the DNA duplex and hybridize with the complementary DNA template strand, generating a three-stranded "R-loop" structure, composed of an RNA:DNA duplex and an unpaired non-template DNA strand. R-loops can be strongly associated with actively transcribed loci by all RNAPs including the mitochondrial RNA polymerase (mtRNAP). In this chapter, we describe two protocols for the detection of RNA:DNA hybrids in living budding yeast cells, one that uses conventional chromatin immunoprecipitation (ChIP-qPCR) and one that uses DNA:RNA immunoprecipitation (DRIP-qPCR). Both protocols make use of the S9.6 antibody, which is believed to recognize the intermediate A/B helical RNA:DNA duplex conformation, with no sequence specificity.
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Affiliation(s)
- Aziz El Hage
- Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, Edinburgh, EH9 3BF, UK.
| | - David Tollervey
- Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, Edinburgh, EH9 3BF, UK
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24
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Abstract
Topoisomerase I (Top1) resolves torsional stress that accumulates during transcription, replication and chromatin remodeling by introducing a transient single-strand break in DNA. The cleavage activity of Top1 has opposing roles, either promoting or destabilizing genome integrity depending on the context. Resolution of transcription-associated negative supercoils, for example, prevents pairing of the nascent RNA with the DNA template (R-loops) as well as DNA secondary structure formation. Reduced Top1 levels thus enhance CAG repeat contraction, somatic hypermutation, and class switch recombination. Actively transcribed ribosomal DNA is also destabilized in the absence of Top1, reflecting the importance of Top1 in ensuring efficient transcription. In terms of promoting genome instability, an aborted Top1 catalytic cycle stimulates deletions at short tandem repeats and the enzyme's transesterification activity supports illegitimate recombination. Finally, Top1 incision at ribonucleotides embedded in DNA generates deletions in tandem repeats, and induces gross chromosomal rearrangements and mitotic recombination.
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Affiliation(s)
- Jang-Eun Cho
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, 213 Research Drive, CARL 384, Durham, NC, 27710, USA
| | - Sue Jinks-Robertson
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, 213 Research Drive, CARL 384, Durham, NC, 27710, USA.
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25
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Khan FA, Ali SO. Physiological Roles of DNA Double-Strand Breaks. J Nucleic Acids 2017; 2017:6439169. [PMID: 29181194 PMCID: PMC5664317 DOI: 10.1155/2017/6439169] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Accepted: 09/24/2017] [Indexed: 12/20/2022] Open
Abstract
Genomic integrity is constantly threatened by sources of DNA damage, internal and external alike. Among the most cytotoxic lesions is the DNA double-strand break (DSB) which arises from the cleavage of both strands of the double helix. Cells boast a considerable set of defences to both prevent and repair these breaks and drugs which derail these processes represent an important category of anticancer therapeutics. And yet, bizarrely, cells deploy this very machinery for the intentional and calculated disruption of genomic integrity, harnessing potentially destructive DSBs in delicate genetic transactions. Under tight spatiotemporal regulation, DSBs serve as a tool for genetic modification, widely used across cellular biology to generate diverse functionalities, ranging from the fundamental upkeep of DNA replication, transcription, and the chromatin landscape to the diversification of immunity and the germline. Growing evidence points to a role of aberrant DSB physiology in human disease and an understanding of these processes may both inform the design of new therapeutic strategies and reduce off-target effects of existing drugs. Here, we review the wide-ranging roles of physiological DSBs and the emerging network of their multilateral regulation to consider how the cell is able to harness DNA breaks as a critical biochemical tool.
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Affiliation(s)
- Farhaan A. Khan
- School of Clinical Medicine, Addenbrooke's Hospital, University of Cambridge, Hills Road, Cambridge CB2 0SP, UK
| | - Syed O. Ali
- School of Clinical Medicine, Addenbrooke's Hospital, University of Cambridge, Hills Road, Cambridge CB2 0SP, UK
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26
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Abstract
Topoisomerases manage the torsional stress associated with the separation of DNA strands during transcription and DNA replication. Eukaryotic Topoisomerase I (Top1) is a Type IB enzyme that nicks and rejoins only one strand of duplex DNA, and it is especially important during transcription. By resolving transcription-associated torsional stress, Top1 reduces the accumulation of genome-destabilizing R-loops and non-B DNA structures. The DNA nicking activity of Top1, however, can also initiate genome instability in the form of illegitimate recombination, homologous recombination and mutagenesis. In this review, we focus on the diverse, and often opposing, roles of Top1 in regulating eukaryotic genome stability.
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27
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Puddu F, Salguero I, Herzog M, Geisler NJ, Costanzo V, Jackson SP. Chromatin determinants impart camptothecin sensitivity. EMBO Rep 2017; 18:1000-1012. [PMID: 28389464 PMCID: PMC5452016 DOI: 10.15252/embr.201643560] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 03/07/2017] [Accepted: 03/09/2017] [Indexed: 11/09/2022] Open
Abstract
Camptothecin-induced locking of topoisomerase 1 on DNA generates a physical barrier to replication fork progression and creates topological stress. By allowing replisome rotation, absence of the Tof1/Csm3 complex promotes the conversion of impending topological stress to DNA catenation and causes camptothecin hypersensitivity. Through synthetic viability screening, we discovered that histone H4 K16 deacetylation drives the sensitivity of yeast cells to camptothecin and that inactivation of this pathway by mutating H4 K16 or the genes SIR1-4 suppresses much of the hypersensitivity of tof1∆ strains towards this agent. We show that disruption of rDNA or telomeric silencing does not mediate camptothecin resistance but that disruption of Sir1-dependent chromatin domains is sufficient to suppress camptothecin sensitivity in wild-type and tof1∆ cells. We suggest that topoisomerase 1 inhibition in proximity of these domains causes topological stress that leads to DNA hypercatenation, especially in the absence of the Tof1/Csm3 complex. Finally, we provide evidence of the evolutionarily conservation of this mechanism.
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Affiliation(s)
- Fabio Puddu
- The Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Israel Salguero
- The Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Mareike Herzog
- The Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
- The Wellcome Trust Sanger Institute, Hinxton Cambridge, UK
| | - Nicola J Geisler
- The Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Vincenzo Costanzo
- IFOM (Fondazione Istituto FIRC di Oncologia Molecolare), Milan, Italy
| | - Stephen P Jackson
- The Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, UK
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28
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The Nuts and Bolts of Transcriptionally Silent Chromatin in Saccharomyces cerevisiae. Genetics 2017; 203:1563-99. [PMID: 27516616 DOI: 10.1534/genetics.112.145243] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 05/30/2016] [Indexed: 12/31/2022] Open
Abstract
Transcriptional silencing in Saccharomyces cerevisiae occurs at several genomic sites including the silent mating-type loci, telomeres, and the ribosomal DNA (rDNA) tandem array. Epigenetic silencing at each of these domains is characterized by the absence of nearly all histone modifications, including most prominently the lack of histone H4 lysine 16 acetylation. In all cases, silencing requires Sir2, a highly-conserved NAD(+)-dependent histone deacetylase. At locations other than the rDNA, silencing also requires additional Sir proteins, Sir1, Sir3, and Sir4 that together form a repressive heterochromatin-like structure termed silent chromatin. The mechanisms of silent chromatin establishment, maintenance, and inheritance have been investigated extensively over the last 25 years, and these studies have revealed numerous paradigms for transcriptional repression, chromatin organization, and epigenetic gene regulation. Studies of Sir2-dependent silencing at the rDNA have also contributed to understanding the mechanisms for maintaining the stability of repetitive DNA and regulating replicative cell aging. The goal of this comprehensive review is to distill a wide array of biochemical, molecular genetic, cell biological, and genomics studies down to the "nuts and bolts" of silent chromatin and the processes that yield transcriptional silencing.
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29
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Chiang SC, Meagher M, Kassouf N, Hafezparast M, McKinnon PJ, Haywood R, El-Khamisy SF. Mitochondrial protein-linked DNA breaks perturb mitochondrial gene transcription and trigger free radical-induced DNA damage. SCIENCE ADVANCES 2017; 3:e1602506. [PMID: 28508041 PMCID: PMC5409496 DOI: 10.1126/sciadv.1602506] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 03/02/2017] [Indexed: 05/06/2023]
Abstract
Breakage of one strand of DNA is the most common form of DNA damage. Most damaged DNA termini require end-processing in preparation for ligation. The importance of this step is highlighted by the association of defects in the 3'-end processing enzyme tyrosyl DNA phosphodiesterase 1 (TDP1) and neurodegeneration and by the cytotoxic induction of protein-linked DNA breaks (PDBs) and oxidized nucleic acid intermediates during chemotherapy and radiotherapy. Although much is known about the repair of PDBs in the nucleus, little is known about this process in the mitochondria. We reveal that TDP1 resolves mitochondrial PDBs (mtPDBs), thereby promoting mitochondrial gene transcription. Overexpression of a toxic form of mitochondrial topoisomerase I (TOP1mt*), which generates excessive mtPDBs, results in a TDP1-dependent compensatory up-regulation of mitochondrial gene transcription. In the absence of TDP1, the imbalance in transcription of mitochondrial- and nuclear-encoded electron transport chain (ETC) subunits results in misassembly of ETC complex III. Bioenergetics profiling further reveals that TDP1 promotes oxidative phosphorylation under both basal and high energy demands. It is known that mitochondrial dysfunction results in free radical leakage and nuclear DNA damage; however, the detection of intermediates of radical damage to DNA is yet to be shown. Consequently, we report an increased accumulation of carbon-centered radicals in cells lacking TDP1, using electron spin resonance spectroscopy. Overexpression of the antioxidant enzyme superoxide dismutase 1 (SOD1) reduces carbon-centered adducts and protects TDP1-deficient cells from oxidative stress. Conversely, overexpression of the amyotrophic lateral sclerosis-associated mutant SOD1G93A leads to marked sensitivity. Whereas Tdp1 knockout mice develop normally, overexpression of SOD1G93A suggests early embryonic lethality. Together, our data show that TDP1 resolves mtPDBs, thereby regulating mitochondrial gene transcription and oxygen consumption by oxidative phosphorylation, thus conferring cellular protection against reactive oxygen species-induced damage.
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Affiliation(s)
- Shih-Chieh Chiang
- Krebs Institute and Sheffield Institute for Nucleic Acids, Department of Molecular Biology and Biotechnology, Firth Court, University of Sheffield, S10 2TN Sheffield, U.K
| | - Martin Meagher
- Wellcome Trust Centre for Mitochondrial Research, Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, U.K
| | - Nick Kassouf
- RAFT Institute, Mount Vernon Hospital, Northwood, Middlesex HA6 2RN, U.K
| | - Majid Hafezparast
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, U.K
| | - Peter J. McKinnon
- Department of Genetics, St. Jude Children’s Research Hospital, Memphis, TN 38105–3678, USA
| | - Rachel Haywood
- RAFT Institute, Mount Vernon Hospital, Northwood, Middlesex HA6 2RN, U.K
| | - Sherif F. El-Khamisy
- Krebs Institute and Sheffield Institute for Nucleic Acids, Department of Molecular Biology and Biotechnology, Firth Court, University of Sheffield, S10 2TN Sheffield, U.K
- Center for Genomics, Helmy Institute for Medical Sciences, Zewail City of Science and Technology, Giza 12588, Egypt
- Corresponding author.
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30
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Cerritelli SM, Crouch RJ. The Balancing Act of Ribonucleotides in DNA. Trends Biochem Sci 2016; 41:434-445. [PMID: 26996833 DOI: 10.1016/j.tibs.2016.02.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 02/01/2016] [Accepted: 02/09/2016] [Indexed: 11/28/2022]
Abstract
The abundance of ribonucleotides in DNA remained undetected until recently because they are efficiently removed by the ribonucleotide excision repair (RER) pathway, a process similar to Okazaki fragment (OF) processing after incision by Ribonuclease H2 (RNase H2). All DNA polymerases incorporate ribonucleotides during DNA synthesis. How many, when, and why they are incorporated has been the focus of intense work during recent years by many labs. In this review, we discuss recent advances in ribonucleotide incorporation by eukaryotic DNA polymerases that suggest an evolutionarily conserved role for ribonucleotides in DNA. We also review the data that indicate that removal of ribonucleotides has an important role in maintaining genome stability.
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Affiliation(s)
- Susana M Cerritelli
- Section on Formation of RNA, Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Robert J Crouch
- Section on Formation of RNA, Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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31
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Chromatin remodeller SMARCA4 recruits topoisomerase 1 and suppresses transcription-associated genomic instability. Nat Commun 2016; 7:10549. [PMID: 26842758 PMCID: PMC4742980 DOI: 10.1038/ncomms10549] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 12/25/2015] [Indexed: 02/07/2023] Open
Abstract
Topoisomerase 1, an enzyme that relieves superhelical tension, is implicated in transcription-associated mutagenesis and genome instability-associated with neurodegenerative diseases as well as activation-induced cytidine deaminase. From proteomic analysis of TOP1-associated proteins, we identify SMARCA4, an ATP-dependent chromatin remodeller; FACT, a histone chaperone; and H3K4me3, a transcriptionally active chromatin marker. Here we show that SMARCA4 knockdown in a B-cell line decreases TOP1 recruitment to chromatin, and leads to increases in Igh/c-Myc chromosomal translocations, variable and switch region mutations and negative superhelicity, all of which are also observed in response to TOP1 knockdown. In contrast, FACT knockdown inhibits association of TOP1 with H3K4me3, and severely reduces DNA cleavage and Igh/c-Myc translocations, without significant effect on TOP1 recruitment to chromatin. We thus propose that SMARCA4 is involved in the TOP1 recruitment to general chromatin, whereas FACT is required for TOP1 binding to H3K4me3 at non-B DNA containing chromatin for the site-specific cleavage. Topoisomerase 1 (TOP1) relieves superhelical tension when DNA strands are unwound during transcription. Here, Husain et al. report that SMARCA4, an ATP-dependent chromatin remodeller, is associated with TOP1 and suppresses transcription-associated genomic instability.
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32
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Manville CM, Smith K, Sondka Z, Rance H, Cockell S, Cowell IG, Lee KC, Morris NJ, Padget K, Jackson GH, Austin CA. Genome-wide ChIP-seq analysis of human TOP2B occupancy in MCF7 breast cancer epithelial cells. Biol Open 2015; 4:1436-47. [PMID: 26459242 PMCID: PMC4728365 DOI: 10.1242/bio.014308] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We report the whole genome ChIP seq for human TOP2B from MCF7 cells. Using three different peak calling methods, regions of binding were identified in the presence or absence of the nuclear hormone estradiol, as TOP2B has been reported to play a role in ligand-induced transcription. TOP2B peaks were found across the whole genome, 50% of the peaks fell either within a gene or within 5 kb of a transcription start site. TOP2B peaks coincident with gene promoters were less frequently associated with epigenetic features marking active promoters in estradiol treated than in untreated cells. Significantly enriched transcription factor motifs within the DNA sequences underlying the peaks were identified. These included SP1, KLF4, TFAP2A, MYF, REST, CTCF, ESR1 and ESR2. Gene ontology analysis of genes associated with TOP2B peaks found neuronal development terms including axonogenesis and axon guidance were significantly enriched. In the absence of functional TOP2B there are errors in axon guidance in the zebrafish eye. Specific heparin sulphate structures are involved in retinal axon targeting. The glycosaminoglycan biosynthesis–heparin sulphate/heparin pathway is significantly enriched in the TOP2B gene ontology analysis, suggesting changes in this pathway in the absence of TOP2B may cause the axon guidance faults. Summary: Gene ontology enrichment analysis of genes associated with human TOP2B peaks, identified by whole genome ChIP seq used to identify regions of binding, highlighted a number of processes in neuronal development including axonogenesis and axon guidance.
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Affiliation(s)
- Catriona M Manville
- Institute for Cellular and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Kayleigh Smith
- Institute for Cellular and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Zbyslaw Sondka
- Institute for Cellular and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Holly Rance
- Institute for Cellular and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Simon Cockell
- The Bioinformatics Support Unit, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Ian G Cowell
- Institute for Cellular and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Ka Cheong Lee
- Institute for Cellular and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Nicholas J Morris
- School of Biomedical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Kay Padget
- Department of Applied Biology, Northumbria University, Newcastle upon Tyne NE1 8ST, UK
| | - Graham H Jackson
- Institute for Cellular Medicine, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Caroline A Austin
- Institute for Cellular and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
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33
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Role for RNA:DNA hybrids in origin-independent replication priming in a eukaryotic system. Proc Natl Acad Sci U S A 2015; 112:5779-84. [PMID: 25902524 DOI: 10.1073/pnas.1501769112] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
DNA replication initiates at defined replication origins along eukaryotic chromosomes, ensuring complete genome duplication within a single S-phase. A key feature of replication origins is their ability to control the onset of DNA synthesis mediated by DNA polymerase-α and its intrinsic RNA primase activity. Here, we describe a novel origin-independent replication process that is mediated by transcription. RNA polymerase I transcription constraints lead to persistent RNA:DNA hybrids (R-loops) that prime replication in the ribosomal DNA locus. Our results suggest that eukaryotic genomes have developed tools to prevent R-loop-mediated replication events that potentially contribute to copy number variation, particularly relevant to carcinogenesis.
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34
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El Hage A, Webb S, Kerr A, Tollervey D. Genome-wide distribution of RNA-DNA hybrids identifies RNase H targets in tRNA genes, retrotransposons and mitochondria. PLoS Genet 2014; 10:e1004716. [PMID: 25357144 PMCID: PMC4214602 DOI: 10.1371/journal.pgen.1004716] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2014] [Accepted: 08/27/2014] [Indexed: 01/08/2023] Open
Abstract
During transcription, the nascent RNA can invade the DNA template, forming extended RNA-DNA duplexes (R-loops). Here we employ ChIP-seq in strains expressing or lacking RNase H to map targets of RNase H activity throughout the budding yeast genome. In wild-type strains, R-loops were readily detected over the 35S rDNA region, transcribed by Pol I, and over the 5S rDNA, transcribed by Pol III. In strains lacking RNase H activity, R-loops were elevated over other Pol III genes, notably tRNAs, SCR1 and U6 snRNA, and were also associated with the cDNAs of endogenous TY1 retrotransposons, which showed increased rates of mobility to the 5′-flanking regions of tRNA genes. Unexpectedly, R-loops were also associated with mitochondrial genes in the absence of RNase H1, but not of RNase H2. Finally, R-loops were detected on actively transcribed protein-coding genes in the wild-type, particularly over the second exon of spliced ribosomal protein genes. R-loops (RNA-DNA hybrids) are potentially deleterious for gene expression and genome stability, but can be beneficial, for example, during immunoglobulin gene class-switch recombination. Here we made use of antibody S9.6, with specificity for RNA-DNA duplexes independently of their sequence. The genome-wide distribution of R-loops in wild-type yeast showed association with the highly transcribed ribosomal DNA, and protein-coding genes, particularly the second exon of spliced genes. On RNA polymerase III loci such as the highly transcribed transfer RNA genes (tRNAs), R-loop accumulation was strongly detected in the absence of both ribonucleases H1 and H2 (RNase H1 and H2), indicating that R-loops are inherently formed but rapidly cleared by RNase H. Importantly, stable R-loops lead to reduced synthesis of tRNA precursors in mutants lacking RNase H and DNA topoisomerase activities. RNA-DNA hybrids associated with TY1 cDNA retrotransposition intermediates were elevated in the absence of RNase H, and this was accompanied by increased retrotransposition, in particular to 5′-flanking regions of tRNAs. Our findings show that RNase H participates in silencing of TY1 life cycle. Surprisingly, R-loops associated with mitochondrial transcription units were suppressed specifically by RNase H1. These findings have potentially important implications for understanding human diseases caused by mutations in RNase H.
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Affiliation(s)
- Aziz El Hage
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail: (AEH); (DT)
| | - Shaun Webb
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Alastair Kerr
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - David Tollervey
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail: (AEH); (DT)
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35
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Roca J. Transcriptional inhibition by DNA torsional stress. Transcription 2014; 2:82-85. [PMID: 21468234 DOI: 10.4161/trns.2.2.14807] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 01/11/2011] [Accepted: 01/12/2011] [Indexed: 12/26/2022] Open
Abstract
Most genome transactions are favored by DNA (-) torsional stress, i.e., unconstrained unwinding or supercoiling of DNA. A question raised here is whether DNA (+) torsional stress, which precludes DNA unwinding, could also be relevant in gene regulation. Such DNA twist dynamics could be determined by chromatin architecture.
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Affiliation(s)
- Joaquim Roca
- Instituto de Biologia Molecular de Barcelona; CSIC; Barcelona, Spain
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36
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Jeppsson K, Carlborg KK, Nakato R, Berta DG, Lilienthal I, Kanno T, Lindqvist A, Brink MC, Dantuma NP, Katou Y, Shirahige K, Sjögren C. The chromosomal association of the Smc5/6 complex depends on cohesion and predicts the level of sister chromatid entanglement. PLoS Genet 2014; 10:e1004680. [PMID: 25329383 PMCID: PMC4199498 DOI: 10.1371/journal.pgen.1004680] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 08/18/2014] [Indexed: 11/24/2022] Open
Abstract
The cohesin complex, which is essential for sister chromatid cohesion and chromosome segregation, also inhibits resolution of sister chromatid intertwinings (SCIs) by the topoisomerase Top2. The cohesin-related Smc5/6 complex (Smc5/6) instead accumulates on chromosomes after Top2 inactivation, known to lead to a buildup of unresolved SCIs. This suggests that cohesin can influence the chromosomal association of Smc5/6 via its role in SCI protection. Using high-resolution ChIP-sequencing, we show that the localization of budding yeast Smc5/6 to duplicated chromosomes indeed depends on sister chromatid cohesion in wild-type and top2-4 cells. Smc5/6 is found to be enriched at cohesin binding sites in the centromere-proximal regions in both cell types, but also along chromosome arms when replication has occurred under Top2-inhibiting conditions. Reactivation of Top2 after replication causes Smc5/6 to dissociate from chromosome arms, supporting the assumption that Smc5/6 associates with a Top2 substrate. It is also demonstrated that the amount of Smc5/6 on chromosomes positively correlates with the level of missegregation in top2-4, and that Smc5/6 promotes segregation of short chromosomes in the mutant. Altogether, this shows that the chromosomal localization of Smc5/6 predicts the presence of the chromatid segregation-inhibiting entities which accumulate in top2-4 mutated cells. These are most likely SCIs, and our results thus indicate that, at least when Top2 is inhibited, Smc5/6 facilitates their resolution.
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Affiliation(s)
- Kristian Jeppsson
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Kristian K. Carlborg
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Ryuichiro Nakato
- University of Tokyo, Institute of Molecular and Cellular Biosciences, Laboratory of Genome Structure and Function Center for Epigenetic Disease, Bunkyo-ku, Tokyo, Japan
| | - Davide G. Berta
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Ingrid Lilienthal
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Takaharu Kanno
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Arne Lindqvist
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Maartje C. Brink
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Nico P. Dantuma
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
| | - Yuki Katou
- University of Tokyo, Institute of Molecular and Cellular Biosciences, Laboratory of Genome Structure and Function Center for Epigenetic Disease, Bunkyo-ku, Tokyo, Japan
| | - Katsuhiko Shirahige
- University of Tokyo, Institute of Molecular and Cellular Biosciences, Laboratory of Genome Structure and Function Center for Epigenetic Disease, Bunkyo-ku, Tokyo, Japan
| | - Camilla Sjögren
- Karolinska Institutet, Department of Cell and Molecular Biology, Stockholm, Sweden
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37
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Hamperl S, Cimprich KA. The contribution of co-transcriptional RNA:DNA hybrid structures to DNA damage and genome instability. DNA Repair (Amst) 2014; 19:84-94. [PMID: 24746923 PMCID: PMC4051866 DOI: 10.1016/j.dnarep.2014.03.023] [Citation(s) in RCA: 189] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Accurate DNA replication and DNA repair are crucial for the maintenance of genome stability, and it is generally accepted that failure of these processes is a major source of DNA damage in cells. Intriguingly, recent evidence suggests that DNA damage is more likely to occur at genomic loci with high transcriptional activity. Furthermore, loss of certain RNA processing factors in eukaryotic cells is associated with increased formation of co-transcriptional RNA:DNA hybrid structures known as R-loops, resulting in double-strand breaks (DSBs) and DNA damage. However, the molecular mechanisms by which R-loop structures ultimately lead to DNA breaks and genome instability is not well understood. In this review, we summarize the current knowledge about the formation, recognition and processing of RNA:DNA hybrids, and discuss possible mechanisms by which these structures contribute to DNA damage and genome instability in the cell.
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Affiliation(s)
- Stephan Hamperl
- Department of Chemical, Systems Biology, Stanford University School of Medicine, 318 Campus Drive, Stanford, CA 94305-5441, USA
| | - Karlene A Cimprich
- Department of Chemical, Systems Biology, Stanford University School of Medicine, 318 Campus Drive, Stanford, CA 94305-5441, USA.
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38
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Fernández X, Díaz-Ingelmo O, Martínez-García B, Roca J. Chromatin regulates DNA torsional energy via topoisomerase II-mediated relaxation of positive supercoils. EMBO J 2014; 33:1492-501. [PMID: 24859967 DOI: 10.15252/embj.201488091] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Eukaryotic topoisomerases I (topo I) and II (topo II) relax the positive (+) and negative (-) DNA torsional stress (TS) generated ahead and behind the transcription machinery. It is unknown how this DNA relaxation activity is regulated and whether (+) and (-)TS are reduced at similar rates. Here, we used yeast circular minichromosomes to conduct the first comparative analysis of topo I and topo II activities in relaxing chromatin under (+) and (-)TS. We observed that, while topo I relaxed (+) and (-)TS with similar efficiency, topo II was more proficient and relaxed (+)TS more quickly than (-)TS. Accordingly, we found that the relaxation rate of (+)TS by endogenous topoisomerases largely surpassed that of (-)TS. We propose a model of how distinct conformations of chromatin under (+) and (-)TS may produce this unbalanced relaxation of DNA. We postulate that, while quick relaxation of (+)TS may facilitate the progression of RNA and DNA polymerases, slow relaxation of (-)TS may serve to favor DNA unwinding and other structural transitions at specific regions often required for genomic transactions.
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Affiliation(s)
- Xavier Fernández
- Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Ofelia Díaz-Ingelmo
- Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Belén Martínez-García
- Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Joaquim Roca
- Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
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39
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Targeted tandem duplication of a large chromosomal segment in Aspergillus oryzae. Appl Environ Microbiol 2014; 80:4547-58. [PMID: 24837372 DOI: 10.1128/aem.00300-14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We describe here the first successful construction of a targeted tandem duplication of a large chromosomal segment in Aspergillus oryzae. The targeted tandem chromosomal duplication was achieved by using strains that had a 5'-deleted pyrG upstream of the region targeted for tandem chromosomal duplication and a 3'-deleted pyrG downstream of the target region. Consequently,strains bearing a 210-kb targeted tandem chromosomal duplication near the centromeric region of chromosome 8 and strains bearing a targeted tandem chromosomal duplication of a 700-kb region of chromosome 2 were successfully constructed. The strains bearing the tandem chromosomal duplication were efficiently obtained from the regenerated protoplast of the parental strains. However, the generation of the chromosomal duplication did not depend on the introduction of double-stranded breaks(DSBs) by I-SceI. The chromosomal duplications of these strains were stably maintained after five generations of culture under nonselective conditions. The strains bearing the tandem chromosomal duplication in the 700-kb region of chromosome 2 showed highly increased protease activity in solid-state culture, indicating that the duplication of large chromosomal segments could be a useful new breeding technology and gene analysis method.
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40
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Dalla Rosa I, Huang SYN, Agama K, Khiati S, Zhang H, Pommier Y. Mapping topoisomerase sites in mitochondrial DNA with a poisonous mitochondrial topoisomerase I (Top1mt). J Biol Chem 2014; 289:18595-602. [PMID: 24798329 DOI: 10.1074/jbc.m114.555367] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Mitochondrial topoisomerase I (Top1mt) is a type IB topoisomerase present in vertebrates and exclusively targeted to mitochondria. Top1mt relaxes mitochondrial DNA (mtDNA) supercoiling by introducing transient cleavage complexes wherein the broken DNA strand swivels around the intact strand. Top1mt cleavage complexes (Top1mtcc) can be stabilized in vitro by camptothecin (CPT). However, CPT does not trap Top1mtcc efficiently in cells and is highly cytotoxic due to nuclear Top1 targeting. To map Top1mtcc on mtDNA in vivo and to overcome the limitations of CPT, we designed two substitutions (T546A and N550H) in Top1mt to stabilize Top1mtcc. We refer to the double-mutant enzyme as Top1mt*. Using retroviral transduction and ChIP-on-chip assays with Top1mt* in Top1mt knock-out murine embryonic fibroblasts, we demonstrate that Top1mt* forms high levels of cleavage complexes preferentially in the noncoding regulatory region of mtDNA, accumulating especially at the heavy strand replication origin OH, in the ribosomal genes (12S and 16S) and at the light strand replication origin OL. Expression of Top1mt* also caused rapid mtDNA depletion without affecting mitochondria mass, suggesting the existence of specific mitochondrial pathways for the removal of damaged mtDNA.
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Affiliation(s)
- Ilaria Dalla Rosa
- From the Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Shar-Yin N Huang
- From the Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Keli Agama
- From the Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Salim Khiati
- From the Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Hongliang Zhang
- From the Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Yves Pommier
- From the Laboratory of Molecular Pharmacology, Developmental Therapeutics Branch, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
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41
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Wright RL, Vaughan ATM. A systematic description of MLL fusion gene formation. Crit Rev Oncol Hematol 2014; 91:283-91. [PMID: 24787275 DOI: 10.1016/j.critrevonc.2014.03.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 02/21/2014] [Accepted: 03/28/2014] [Indexed: 11/25/2022] Open
Abstract
Rearrangements of the MLL gene involve multiple partners and are implicated in both therapy related acute leukemia [tAL] and infant acute leukemia. For these diseases, recently compiled clinical data confirms an elevated frequency of such breakpoints within a 4 kb tract between exon 11 and a region of structural instability adjacent to exon 12. Linked primarily to cases of tAL, interference with topoisomerase II activity may either contribute to the initial DNA lesion directly or indirectly by, for example, providing a physical block to transcription progression. Alternatively, sites of fragmentation may be mis-repaired, guided by intergenic spliced transcripts of the participating genes. Co-transcription of MLL and potential fusion partners may provide the localization that enhances the probability of gene interaction. An indirect role for the leukemogenic activity of topoisomerase II inhibitors would imply that the negative consequences of their use may be separated from their therapeutic effects.
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Affiliation(s)
- Rebecca L Wright
- Department of Radiation Oncology, University of California at Davis, 4501 X Street, Sacramento, CA 95817, United States
| | - Andrew T M Vaughan
- Department of Radiation Oncology, University of California at Davis, 4501 X Street, Sacramento, CA 95817, United States.
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42
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Lavelle C. Pack, unpack, bend, twist, pull, push: the physical side of gene expression. Curr Opin Genet Dev 2014; 25:74-84. [PMID: 24576847 DOI: 10.1016/j.gde.2014.01.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 01/03/2014] [Indexed: 12/31/2022]
Abstract
Molecular motors such as polymerases produce physical constraints on DNA and chromatin. Recent techniques, in particular single-molecule micromanipulation, provide estimation of the forces and torques at stake. These biophysical approaches have improved our understanding of chromatin behaviour under physiological physical constraints and should, in conjunction with genome wide and in vivo studies, help to build more realistic mechanistic models of transcription in the context of chromatin. Here, we wish to provide a brief overview of our current knowledge in the field, and emphasize at the same time the importance of DNA supercoiling as a major parameter in gene regulation.
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Affiliation(s)
- Christophe Lavelle
- National Museum of Natural History, Paris, France; CNRS UMR7196, Paris, France; INSERM U1154, Paris, France; Nuclear Architecture and Dynamics, CNRS GDR3536, Paris, France.
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43
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Krawczyk C, Dion V, Schär P, Fritsch O. Reversible Top1 cleavage complexes are stabilized strand-specifically at the ribosomal replication fork barrier and contribute to ribosomal DNA stability. Nucleic Acids Res 2014; 42:4985-95. [PMID: 24574527 PMCID: PMC4005688 DOI: 10.1093/nar/gku148] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Various topological constraints at the ribosomal DNA (rDNA) locus impose an extra challenge for transcription and DNA replication, generating constant torsional DNA stress. The topoisomerase Top1 is known to release such torsion by single-strand nicking and re-ligation in a process involving transient covalent Top1 cleavage complexes (Top1cc) with the nicked DNA. Here we show that Top1ccs, despite their usually transient nature, are specifically targeted to and stabilized at the ribosomal replication fork barrier (rRFB) of budding yeast, establishing a link with previously reported Top1 controlled nicks. Using ectopically engineered rRFBs, we establish that the rRFB sequence itself is sufficient for induction of DNA strand-specific and replication-independent Top1ccs. These Top1ccs accumulate only in the presence of Fob1 and Tof2, they are reversible as they are not subject to repair by Tdp1- or Mus81-dependent processes, and their presence correlates with Top1 provided rDNA stability. Notably, the targeted formation of these Top1ccs accounts for the previously reported broken replication forks at the rRFB. These findings implicate a novel and physiologically regulated mode of Top1 action, suggesting a mechanism by which Top1 is recruited to the rRFB and stabilized in a reversible Top1cc configuration to preserve the integrity of the rDNA.
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Affiliation(s)
- Claudia Krawczyk
- Department of Biomedicine, University of Basel, 4058 Basel, Switzerland and Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
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44
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Peltonen K, Colis L, Liu H, Trivedi R, Moubarek MS, Moore HM, Bai B, Rudek MA, Bieberich CJ, Laiho M. A targeting modality for destruction of RNA polymerase I that possesses anticancer activity. Cancer Cell 2014; 25:77-90. [PMID: 24434211 PMCID: PMC3930145 DOI: 10.1016/j.ccr.2013.12.009] [Citation(s) in RCA: 206] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 10/03/2013] [Accepted: 12/16/2013] [Indexed: 01/07/2023]
Abstract
We define the activity and mechanisms of action of a small molecule lead compound for cancer targeting. We show that the compound, BMH-21, has wide and potent antitumorigenic activity across NCI60 cancer cell lines and represses tumor growth in vivo. BMH-21 binds GC-rich sequences, which are present at a high frequency in ribosomal DNA genes, and potently and rapidly represses RNA polymerase I (Pol I) transcription. Strikingly, we find that BMH-21 causes proteasome-dependent destruction of RPA194, the large catalytic subunit protein of Pol I holocomplex, and this correlates with cancer cell killing. Our results show that Pol I activity is under proteasome-mediated control, which reveals an unexpected therapeutic opportunity.
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Affiliation(s)
- Karita Peltonen
- Molecular Cancer Biology Program and Centre for Drug Research, University of Helsinki, Helsinki 00014, Finland
| | - Laureen Colis
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA
| | - Hester Liu
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA
| | - Rishi Trivedi
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA
| | - Michael S Moubarek
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250, USA
| | - Henna M Moore
- Molecular Cancer Biology Program and Centre for Drug Research, University of Helsinki, Helsinki 00014, Finland
| | - Baoyan Bai
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA
| | - Michelle A Rudek
- Department of Oncology and The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA
| | - Charles J Bieberich
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD 21250, USA
| | - Marikki Laiho
- Molecular Cancer Biology Program and Centre for Drug Research, University of Helsinki, Helsinki 00014, Finland; Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA; Department of Oncology and The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA.
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45
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Gilbert N, Allan J. Supercoiling in DNA and chromatin. Curr Opin Genet Dev 2013; 25:15-21. [PMID: 24584092 PMCID: PMC4042020 DOI: 10.1016/j.gde.2013.10.013] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 10/29/2013] [Accepted: 10/30/2013] [Indexed: 01/20/2023]
Abstract
Supercoiling is a fundamental property of DNA and chromatin. It is modulated by polymerase and topoisomerase activities and, through regulated constraint, by DNA/chromatin binding proteins. As a non-covalent and elusive topological modification, supercoiling has proved intractable to research despite being a crucial regulator of nuclear structure and function. Recent studies have improved our understanding of the formation, regulation and organisation of supercoiling domains in vivo, and reinforce the prospect that the propagation of supercoiling can influence local and global chromatin structure. However, to further our understanding the development of new experimental tools and models are required to better dissect the mechanics of this key topological regulator.
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Affiliation(s)
- Nick Gilbert
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh EH4 2XU, UK.
| | - James Allan
- Institute of Cell Biology, The University of Edinburgh, Edinburgh EH9 3JR, UK.
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46
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Marinello J, Chillemi G, Bueno S, Manzo SG, Capranico G. Antisense transcripts enhanced by camptothecin at divergent CpG-island promoters associated with bursts of topoisomerase I-DNA cleavage complex and R-loop formation. Nucleic Acids Res 2013; 41:10110-23. [PMID: 23999093 PMCID: PMC3905886 DOI: 10.1093/nar/gkt778] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 08/06/2013] [Accepted: 08/06/2013] [Indexed: 12/28/2022] Open
Abstract
DNA Topoisomerase I (Top1) is required to relax DNA supercoils generated by RNA polymerases (RNAPs). Top1 is inhibited with high specificity by camptothecin (CPT), an effective anticancer agent, and by oxidative base damage and ribonucleotides in DNA strands, resulting into Top1-DNA cleavage complexes (Top1ccs). To understand how Top1ccs affect genome stability, we have investigated the global transcriptional response to CPT-induced Top1ccs. Top1ccs trigger an accumulation of antisense RNAPII transcripts specifically at active divergent CpG-island promoters in a replication-independent and Top1-dependent manner. As CPT increases antisense transcript levels in the presence of 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, a transcription inhibitor, Top1ccs likely impair antisense RNA degradation. Time-course data showed a burst of Top1ccs increased by CPT at promoter sites and along transcribed regions, causing a transient block of RNAPII at the promoter. Moreover, cell immunofluorescence analyses showed that Top1ccs induce a transient increase of R-loops specifically at highly transcribed regions such as nucleoli in a Top1-dependent manner. Thus, a specific and highly dynamic transcriptional response to Top1ccs occurs at divergent active CpG-island promoters, which may include a transient stabilization of R-loops. The results clarify molecular features of a response pathway leading to transcription-dependent genome instability and altered transcription regulation.
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Affiliation(s)
- Jessica Marinello
- Department of Pharmacy and Biotechnology, University of Bologna, via Irnerio 48, 40126 Bologna, Italy and CASPUR, via dei Tizii 6, Rome 00185, Italy
| | - Giovanni Chillemi
- Department of Pharmacy and Biotechnology, University of Bologna, via Irnerio 48, 40126 Bologna, Italy and CASPUR, via dei Tizii 6, Rome 00185, Italy
| | - Susana Bueno
- Department of Pharmacy and Biotechnology, University of Bologna, via Irnerio 48, 40126 Bologna, Italy and CASPUR, via dei Tizii 6, Rome 00185, Italy
| | - Stefano G. Manzo
- Department of Pharmacy and Biotechnology, University of Bologna, via Irnerio 48, 40126 Bologna, Italy and CASPUR, via dei Tizii 6, Rome 00185, Italy
| | - Giovanni Capranico
- Department of Pharmacy and Biotechnology, University of Bologna, via Irnerio 48, 40126 Bologna, Italy and CASPUR, via dei Tizii 6, Rome 00185, Italy
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47
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Albert B, Colleran C, Léger-Silvestre I, Berger AB, Dez C, Normand C, Perez-Fernandez J, McStay B, Gadal O. Structure-function analysis of Hmo1 unveils an ancestral organization of HMG-Box factors involved in ribosomal DNA transcription from yeast to human. Nucleic Acids Res 2013; 41:10135-49. [PMID: 24021628 PMCID: PMC3905846 DOI: 10.1093/nar/gkt770] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Ribosome biogenesis is a major metabolic effort for growing cells. In Saccharomyces cerevisiae, Hmo1, an abundant high-mobility group box protein (HMGB) binds to the coding region of the RNA polymerase I transcribed ribosomal RNAs genes and the promoters of ∼70% of ribosomal protein genes. In this study, we have demonstrated the functional conservation of eukaryotic HMGB proteins involved in ribosomal DNA (rDNA) transcription. We have shown that when expressed in budding yeast, human UBF1 and a newly identified Sp-Hmo1 (Schizosaccharomyces pombe) localize to the nucleolus and suppress growth defect of the RNA polymerase I mutant rpa49-Δ. Owing to the multiple functions of both proteins, Hmo1 and UBF1 are not fully interchangeable. By deletion and domains swapping in Hmo1, we identified essential domains that stimulate rDNA transcription but are not fully required for stimulation of ribosomal protein genes expression. Hmo1 is organized in four functional domains: a dimerization module, a canonical HMGB motif followed by a conserved domain and a C-terminal nucleolar localization signal. We propose that Hmo1 has acquired species-specific functions and shares with UBF1 and Sp-Hmo1 an ancestral function to stimulate rDNA transcription.
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Affiliation(s)
- Benjamin Albert
- LBME du CNRS, Université de Toulouse, 118 route de Narbonne, F-31000 Toulouse, France, Laboratoire de Biologie Moléculaire Eucaryote, Université de Toulouse, 118 route de Narbonne, F-31000 Toulouse, France and Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, University Road, Galway, Ireland
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48
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Viktorovskaya OV, Engel KL, French SL, Cui P, Vandeventer PJ, Pavlovic EM, Beyer AL, Kaplan CD, Schneider DA. Divergent contributions of conserved active site residues to transcription by eukaryotic RNA polymerases I and II. Cell Rep 2013; 4:974-84. [PMID: 23994471 DOI: 10.1016/j.celrep.2013.07.044] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 07/10/2013] [Accepted: 07/30/2013] [Indexed: 12/29/2022] Open
Abstract
Multisubunit RNA polymerases (msRNAPs) exhibit high sequence and structural homology, especially within their active sites, which is generally thought to result in msRNAP functional conservation. However, we show that mutations in the trigger loop (TL) in the largest subunit of RNA polymerase I (Pol I) yield phenotypes unexpected from studies of Pol II. For example, a well-characterized gain-of-function mutation in Pol II results in loss of function in Pol I (Pol II: rpb1- E1103G; Pol I: rpa190-E1224G). Studies of chimeric Pol II enzymes hosting Pol I or Pol III TLs suggest that consequences of mutations that alter TL dynamics are dictated by the greater enzymatic context and not solely the TL sequence. Although the rpa190-E1224G mutation diminishes polymerase activity, when combined with mutations that perturb Pol I catalysis, it enhances polymerase function, similar to the analogous Pol II mutation. These results suggest that Pol I and Pol II have different rate-limiting steps.
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Affiliation(s)
- Olga V Viktorovskaya
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294-0024, USA
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49
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R-loop formation at Snord116 mediates topotecan inhibition of Ube3a-antisense and allele-specific chromatin decondensation. Proc Natl Acad Sci U S A 2013; 110:13938-43. [PMID: 23918391 DOI: 10.1073/pnas.1305426110] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are oppositely imprinted autism-spectrum disorders with known genetic bases, but complex epigenetic mechanisms underlie their pathogenesis. The PWS/AS locus on 15q11-q13 is regulated by an imprinting control region that is maternally methylated and silenced. The PWS imprinting control region is the promoter for a one megabase paternal transcript encoding the ubiquitous protein-coding Snrpn gene and multiple neuron-specific noncoding RNAs, including the PWS-related Snord116 repetitive locus of small nucleolar RNAs and host genes, and the antisense transcript to AS-causing ubiquitin ligase encoding Ube3a (Ube3a-ATS). Neuron-specific transcriptional progression through Ube3a-ATS correlates with paternal Ube3a silencing and chromatin decondensation. Interestingly, topoisomerase inhibitors, including topotecan, were recently identified in an unbiased drug screen for compounds that could reverse the silent paternal allele of Ube3a in neurons, but the mechanism of topotecan action on the PWS/AS locus is unknown. Here, we demonstrate that topotecan treatment stabilizes the formation of RNA:DNA hybrids (R loops) at G-skewed repeat elements within paternal Snord116, corresponding to increased chromatin decondensation and inhibition of Ube3a-ATS expression. Neural precursor cells from paternal Snord116 deletion mice exhibit increased Ube3a-ATS levels in differentiated neurons and show a reduced effect of topotecan compared with wild-type neurons. These results demonstrate that the AS candidate drug topotecan acts predominantly through stabilizing R loops and chromatin decondensation at the paternally expressed PWS Snord116 locus. Our study holds promise for targeted therapies to the Snord116 locus for both AS and PWS.
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50
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Abstract
Methods for exerting and measuring forces on single molecules have revolutionized the study of the physics of biology. However, it is often the case that biological processes involve rotation or torque generation, and these parameters have been more difficult to access experimentally. Recent advances in the single-molecule field have led to the development of techniques that add the capability of torque measurement. By combining force, displacement, torque, and rotational data, a more comprehensive description of the mechanics of a biomolecule can be achieved. In this review, we highlight a number of biological processes for which torque plays a key mechanical role. We describe the various techniques that have been developed to directly probe the torque experienced by a single molecule, and detail a variety of measurements made to date using these new technologies. We conclude by discussing a number of open questions and propose systems of study that would be well suited for analysis with torsional measurement techniques.
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Affiliation(s)
- Scott Forth
- Laboratory of Chemistry and Cell Biology, The Rockefeller University, New York, New York 10065, USA.
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