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An Z, Jiang A, Chen J. Toward understanding the role of genomic repeat elements in neurodegenerative diseases. Neural Regen Res 2025; 20:646-659. [PMID: 38886931 DOI: 10.4103/nrr.nrr-d-23-01568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 03/02/2024] [Indexed: 06/20/2024] Open
Abstract
Neurodegenerative diseases cause great medical and economic burdens for both patients and society; however, the complex molecular mechanisms thereof are not yet well understood. With the development of high-coverage sequencing technology, researchers have started to notice that genomic repeat regions, previously neglected in search of disease culprits, are active contributors to multiple neurodegenerative diseases. In this review, we describe the association between repeat element variants and multiple degenerative diseases through genome-wide association studies and targeted sequencing. We discuss the identification of disease-relevant repeat element variants, further powered by the advancement of long-read sequencing technologies and their related tools, and summarize recent findings in the molecular mechanisms of repeat element variants in brain degeneration, such as those causing transcriptional silencing or RNA-mediated gain of toxic function. Furthermore, we describe how in silico predictions using innovative computational models, such as deep learning language models, could enhance and accelerate our understanding of the functional impact of repeat element variants. Finally, we discuss future directions to advance current findings for a better understanding of neurodegenerative diseases and the clinical applications of genomic repeat elements.
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Affiliation(s)
- Zhengyu An
- Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China
| | - Aidi Jiang
- Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China
| | - Jingqi Chen
- Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China
- MOE Frontiers Center for Brain Science, Fudan University, Shanghai, China
- MOE Key Laboratory of Computational Neuroscience and Brain-Inspired Intelligence, Fudan University, Shanghai, China
- Zhangjiang Fudan International Innovation Center, Shanghai, China
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2
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Wang N, Zhang S, Langfelder P, Ramanathan L, Plascencia M, Gao F, Vaca R, Gu X, Deng L, Dionisio LE, Prasad BC, Vogt T, Horvath S, Aaronson JS, Rosinski J, Yang XW. Msh3 and Pms1 Set Neuronal CAG-repeat Migration Rate to Drive Selective Striatal and Cortical Pathogenesis in HD Mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.09.602815. [PMID: 39026894 PMCID: PMC11257559 DOI: 10.1101/2024.07.09.602815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
Modifiers of Huntington's disease (HD) include mismatch repair (MMR) genes; however, their underlying disease-altering mechanisms remain unresolved. Knockout (KO) alleles for 9 HD GWAS modifiers/MMR genes were crossed to the Q140 Huntingtin (mHtt) knock-in mice to probe such mechanisms. Four KO mice strongly ( Msh3 and Pms1 ) or moderately ( Msh2 and Mlh1 ) rescue a triad of adult-onset, striatal medium-spiny-neuron (MSN)-selective phenotypes: somatic Htt DNA CAG-repeat expansion, transcriptionopathy, and mHtt protein aggregation. Comparatively, Q140 cortex also exhibits an analogous, but later-onset, pathogenic triad that is Msh3 -dependent. Remarkably, Q140/homozygous Msh3-KO lacks visible mHtt aggregates in the brain, even at advanced ages (20-months). Moreover, Msh3 -deficiency prevents striatal synaptic marker loss, astrogliosis, and locomotor impairment in HD mice. Purified Q140 MSN nuclei exhibit highly linear age-dependent mHtt DNA repeat expansion (i.e. repeat migration), with modal-CAG increasing at +8.8 repeats/month (R 2 =0.98). This linear rate is reduced to 2.3 and 0.3 repeats/month in Q140 with Msh3 heterozygous and homozygous alleles, respectively. Our study defines somatic Htt CAG-repeat thresholds below which there are no detectable mHtt nuclear or neuropil aggregates. Mild transcriptionopathy can still occur in Q140 mice with stabilized Htt 140-CAG repeats, but the majority of transcriptomic changes are due to somatic repeat expansion. Our analysis reveals 479 genes with expression levels highly correlated with modal-CAG length in MSNs. Thus, our study mechanistically connects HD GWAS genes to selective neuronal vulnerability in HD, in which Msh3 and Pms1 set the linear rate of neuronal mHtt CAG-repeat migration to drive repeat-length dependent pathogenesis; and provides a preclinical platform for targeting these genes for HD suppression across brain regions. One Sentence Summary Msh3 and Pms1 are genetic drivers of sequential striatal and cortical pathogenesis in Q140 mice by mediating selective CAG-repeat migration in HD vulnerable neurons.
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3
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Provasek VE, Bacolla A, Rangaswamy S, Mitra J, Kodavati M, Yusuf IO, Malojirao VH, Vasquez V, Britz GW, Li GM, Xu Z, Mitra S, Garruto RM, Tainer JA, Hegde ML. RNA/DNA Binding Protein TDP43 Regulates DNA Mismatch Repair Genes with Implications for Genome Stability. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.16.594552. [PMID: 38798341 PMCID: PMC11118483 DOI: 10.1101/2024.05.16.594552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
TDP43 is an RNA/DNA binding protein increasingly recognized for its role in neurodegenerative conditions including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). As characterized by its aberrant nuclear export and cytoplasmic aggregation, TDP43 proteinopathy is a hallmark feature in over 95% of ALS/FTD cases, leading to the formation of detrimental cytosolic aggregates and a reduction in nuclear functionality within neurons. Building on our prior work linking TDP43 proteinopathy to the accumulation of DNA double-strand breaks (DSBs) in neurons, the present investigation uncovers a novel regulatory relationship between TDP43 and DNA mismatch repair (MMR) gene expressions. Here, we show that TDP43 depletion or overexpression directly affects the expression of key MMR genes. Alterations include MLH1, MSH2, MSH3, MSH6, and PMS2 levels across various primary cell lines, independent of their proliferative status. Our results specifically establish that TDP43 selectively influences the expression of MLH1 and MSH6 by influencing their alternative transcript splicing patterns and stability. We furthermore find aberrant MMR gene expression is linked to TDP43 proteinopathy in two distinct ALS mouse models and post-mortem brain and spinal cord tissues of ALS patients. Notably, MMR depletion resulted in the partial rescue of TDP43 proteinopathy-induced DNA damage and signaling. Moreover, bioinformatics analysis of the TCGA cancer database reveals significant associations between TDP43 expression, MMR gene expression, and mutational burden across multiple cancers. Collectively, our findings implicate TDP43 as a critical regulator of the MMR pathway and unveil its broad impact on the etiology of both neurodegenerative and neoplastic pathologies.
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Affiliation(s)
- Vincent E Provasek
- Division of DNA Repair Research within the Center for Neuroregeneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston, TX 77030, USA
- School of Medicine, Texas A&M University, College Station, TX 77843, USA
| | - Albino Bacolla
- Department of Molecular and Cellular Oncology, Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Suganya Rangaswamy
- Division of DNA Repair Research within the Center for Neuroregeneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Joy Mitra
- Division of DNA Repair Research within the Center for Neuroregeneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Manohar Kodavati
- Division of DNA Repair Research within the Center for Neuroregeneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Issa O Yusuf
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, MA, 01655, USA
| | - Vikas H Malojirao
- Division of DNA Repair Research within the Center for Neuroregeneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Velmarini Vasquez
- Division of DNA Repair Research within the Center for Neuroregeneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Gavin W Britz
- Division of DNA Repair Research within the Center for Neuroregeneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston, TX 77030, USA
- Department of Neurosurgery and Department of Neuroscience, Weill Cornell Medical College, New York, NY 10065, USA
| | - Guo-Min Li
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Zuoshang Xu
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, MA, 01655, USA
| | - Sankar Mitra
- Division of DNA Repair Research within the Center for Neuroregeneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Ralph M Garruto
- Department of Biological Sciences, Binghamton University, State University of New York, Binghamton, NY 13902
| | - John A Tainer
- Department of Molecular and Cellular Oncology, Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Muralidhar L Hegde
- Division of DNA Repair Research within the Center for Neuroregeneration, Department of Neurosurgery, Houston Methodist Research Institute, Houston, TX 77030, USA
- Department of Neuroscience, Weill Cornell Medical College, New York, NY 10065, USA
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4
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Alanazi AFR, Parkinson GN, Haider S. Structural Motifs at the Telomeres and Their Role in Regulatory Pathways. Biochemistry 2024; 63:827-842. [PMID: 38481135 PMCID: PMC10993422 DOI: 10.1021/acs.biochem.4c00023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Telomeres are specialized structures, found at the ends of linear chromosomes in eukaryotic cells, that play a crucial role in maintaining the stability and integrity of genomes. They are composed of repetitive DNA sequences, ssDNA overhangs, and several associated proteins. The length of telomeres is linked to cellular aging in humans, and deficiencies in their maintenance are associated with various diseases. Key structural motifs at the telomeres serve to protect vulnerable chromosomal ends. Telomeric DNA also has the ability to form diverse complex DNA higher-order structures, including T-loops, D-loops, R-loops, G-loops, G-quadruplexes, and i-motifs, in the complementary C-rich strand. While many essential proteins at telomeres have been identified, the intricacies of their interactions and structural details are still not fully understood. This Perspective highlights recent advancements in comprehending the structures associated with human telomeres. It emphasizes the significance of telomeres, explores various telomeric structural motifs, and delves into the structural biology surrounding telomeres and telomerase. Furthermore, telomeric loops, their topologies, and the associated proteins that contribute to the safeguarding of telomeres are discussed.
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Affiliation(s)
- Abeer F R Alanazi
- UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - Gary N Parkinson
- UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - Shozeb Haider
- UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
- UCL Centre for Advanced Research Computing, University College London, London WC1H 9RN, United Kingdom
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5
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Westover KR, Jin P, Yao B. Bridging the gap: R-loop mediated genomic instability and its implications in neurological diseases. Epigenomics 2024; 16:589-608. [PMID: 38530068 PMCID: PMC11160457 DOI: 10.2217/epi-2023-0379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 03/12/2024] [Indexed: 03/27/2024] Open
Abstract
R-loops, intricate three-stranded structures formed by RNA-DNA hybrids and an exposed non-template DNA strand, are fundamental to various biological phenomena. They carry out essential and contrasting functions within cellular mechanisms, underlining their critical role in maintaining cellular homeostasis. The specific cellular context that dictates R-loop formation determines their function, particularly emphasizing the necessity for their meticulous genomic regulation. Notably, the aberrant formation or misregulation of R-loops is implicated in numerous neurological disorders. This review focuses on the complex interactions between R-loops and double-strand DNA breaks, exploring how R-loop dysregulation potentially contributes to the pathogenesis of various brain disorders, which could provide novel insights into the molecular mechanisms underpinning neurological disease progression and identify potential therapeutic targets by highlighting these aspects.
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Affiliation(s)
- Katherine R Westover
- Department of Human Genetics, Emory University, School of Medicine, Atlanta, GA 30322, USA
| | - Peng Jin
- Department of Human Genetics, Emory University, School of Medicine, Atlanta, GA 30322, USA
| | - Bing Yao
- Department of Human Genetics, Emory University, School of Medicine, Atlanta, GA 30322, USA
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6
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Margoliash J, Fuchs S, Li Y, Zhang X, Massarat A, Goren A, Gymrek M. Polymorphic short tandem repeats make widespread contributions to blood and serum traits. CELL GENOMICS 2023; 3:100458. [PMID: 38116119 PMCID: PMC10726533 DOI: 10.1016/j.xgen.2023.100458] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 09/09/2023] [Accepted: 11/07/2023] [Indexed: 12/21/2023]
Abstract
Short tandem repeats (STRs) are genomic regions consisting of repeated sequences of 1-6 bp in succession. Single-nucleotide polymorphism (SNP)-based genome-wide association studies (GWASs) do not fully capture STR effects. To study these effects, we imputed 445,720 STRs into genotype arrays from 408,153 White British UK Biobank participants and tested for association with 44 blood phenotypes. Using two fine-mapping methods, we identify 119 candidate causal STR-trait associations and estimate that STRs account for 5.2%-7.6% of causal variants identifiable from GWASs for these traits. These are among the strongest associations for multiple phenotypes, including a coding CTG repeat associated with apolipoprotein B levels, a promoter CGG repeat with platelet traits, and an intronic poly(A) repeat with mean platelet volume. Our study suggests that STRs make widespread contributions to complex traits, provides stringently selected candidate causal STRs, and demonstrates the need to consider a more complete view of genetic variation in GWASs.
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Affiliation(s)
- Jonathan Margoliash
- Department of Computer Science and Engineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Shai Fuchs
- Pediatric Endocrine and Diabetes Unit, Edmond and Lily Safra Children’s Hospital, Sheba Medical Center, Ramat Gan, Israel
| | - Yang Li
- Department of Computer Science and Engineering, University of California, San Diego, La Jolla, CA 92093, USA
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Xuan Zhang
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Arya Massarat
- Bioinformatics and Systems Biology Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Alon Goren
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Melissa Gymrek
- Department of Computer Science and Engineering, University of California, San Diego, La Jolla, CA 92093, USA
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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7
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Suzuki MM, Iijima K, Ogami K, Shinjo K, Murofushi Y, Xie J, Wang X, Kitano Y, Mamiya A, Kibe Y, Nishimura T, Ohka F, Saito R, Sato S, Kobayashi J, Yao R, Miyata K, Kataoka K, Suzuki HI, Kondo Y. TUG1-mediated R-loop resolution at microsatellite loci as a prerequisite for cancer cell proliferation. Nat Commun 2023; 14:4521. [PMID: 37607907 PMCID: PMC10444773 DOI: 10.1038/s41467-023-40243-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 07/19/2023] [Indexed: 08/24/2023] Open
Abstract
Oncogene-induced DNA replication stress (RS) and consequent pathogenic R-loop formation are known to impede S phase progression. Nonetheless, cancer cells continuously proliferate under such high-stressed conditions through incompletely understood mechanisms. Here, we report taurine upregulated gene 1 (TUG1) long noncoding RNA (lncRNA), which is highly expressed in many types of cancers, as an important regulator of intrinsic R-loop in cancer cells. Under RS conditions, TUG1 is rapidly upregulated via activation of the ATR-CHK1 signaling pathway, interacts with RPA and DHX9, and engages in resolving R-loops at certain loci, particularly at the CA repeat microsatellite loci. Depletion of TUG1 leads to overabundant R-loops and enhanced RS, leading to substantial inhibition of tumor growth. Our data reveal a role of TUG1 as molecule important for resolving R-loop accumulation in cancer cells and suggest targeting TUG1 as a potent therapeutic approach for cancer treatment.
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Affiliation(s)
- Miho M Suzuki
- Division of Cancer Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Kenta Iijima
- Division of Cancer Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
- Laboratory Animal Facilities and Services, Preeminent Medical Photonics Education and Research Center, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, Shizuoka, 431-3192, Japan
| | - Koichi Ogami
- Division of Molecular Oncology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Keiko Shinjo
- Division of Cancer Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Yoshiteru Murofushi
- Division of Cancer Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Jingqi Xie
- Division of Cancer Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Xuebing Wang
- Division of Cancer Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Yotaro Kitano
- Department of Neurosurgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Akira Mamiya
- Division of Cancer Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Yuji Kibe
- Division of Cancer Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
- Department of Neurosurgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Tatsunori Nishimura
- Division of Cancer Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Fumiharu Ohka
- Department of Neurosurgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Ryuta Saito
- Department of Neurosurgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
| | - Shinya Sato
- Molecular Pathology and Genetics Division, Kanagawa Cancer Center Research Institute, 2-3-2 Nakao, Asahi-ku, Yokohama, Kanagawa, 241-8515, Japan
| | - Junya Kobayashi
- School of Health Sciences at Narita, International University of Health and Welfare, 4-3 Kozunomori, Narita, Chiba, 286-8686, Japan
| | - Ryoji Yao
- Department of Cell Biology, Japanese Foundation for Cancer Research, 3-8-31 Ariake, Koto-ku, Tokyo, 135-8550, Japan
| | - Kanjiro Miyata
- Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Kazunori Kataoka
- Innovation Center of NanoMedicine, Kawasaki Institute of Industrial Promotion, 3-25-14 Tono-machi, Kawasaki-ku, Kanagawa, 210-0821, Japan
- Institute for Future Initiatives, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Hiroshi I Suzuki
- Division of Molecular Oncology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan
- Institute for Glyco-core Research (iGCORE), Tokai National Higher Education and Research System, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan
| | - Yutaka Kondo
- Division of Cancer Biology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan.
- Institute for Glyco-core Research (iGCORE), Tokai National Higher Education and Research System, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan.
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8
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Lee HG, Imaichi S, Kraeutler E, Aguilar R, Lee YW, Sheridan SD, Lee JT. Site-specific R-loops induce CGG repeat contraction and fragile X gene reactivation. Cell 2023; 186:2593-2609.e18. [PMID: 37209683 DOI: 10.1016/j.cell.2023.04.035] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 01/15/2023] [Accepted: 04/26/2023] [Indexed: 05/22/2023]
Abstract
Here, we describe an approach to correct the genetic defect in fragile X syndrome (FXS) via recruitment of endogenous repair mechanisms. A leading cause of autism spectrum disorders, FXS results from epigenetic silencing of FMR1 due to a congenital trinucleotide (CGG) repeat expansion. By investigating conditions favorable to FMR1 reactivation, we find MEK and BRAF inhibitors that induce a strong repeat contraction and full FMR1 reactivation in cellular models. We trace the mechanism to DNA demethylation and site-specific R-loops, which are necessary and sufficient for repeat contraction. A positive feedback cycle comprising demethylation, de novo FMR1 transcription, and R-loop formation results in the recruitment of endogenous DNA repair mechanisms that then drive excision of the long CGG repeat. Repeat contraction is specific to FMR1 and restores the production of FMRP protein. Our study therefore identifies a potential method of treating FXS in the future.
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Affiliation(s)
- Hun-Goo Lee
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Sachiko Imaichi
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Elizabeth Kraeutler
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Rodrigo Aguilar
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Yong-Woo Lee
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA
| | - Steven D Sheridan
- Center for Quantitative Health Center for Genomic Medicine and Department of Psychiatry, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Psychiatry, Harvard Medical School, Boston, MA 02114, USA
| | - Jeannie T Lee
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02114, USA.
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9
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Laspata N, Kaur P, Mersaoui S, Muoio D, Liu Z, Bannister MH, Nguyen H, Curry C, Pascal J, Poirier G, Wang H, Masson JY, Fouquerel E. PARP1 associates with R-loops to promote their resolution and genome stability. Nucleic Acids Res 2023; 51:2215-2237. [PMID: 36794853 PMCID: PMC10018367 DOI: 10.1093/nar/gkad066] [Citation(s) in RCA: 25] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 01/19/2023] [Accepted: 02/09/2023] [Indexed: 02/17/2023] Open
Abstract
PARP1 is a DNA-dependent ADP-Ribose transferase with ADP-ribosylation activity that is triggered by DNA breaks and non-B DNA structures to mediate their resolution. PARP1 was also recently identified as a component of the R-loop-associated protein-protein interaction network, suggesting a potential role for PARP1 in resolving this structure. R-loops are three-stranded nucleic acid structures that consist of a RNA-DNA hybrid and a displaced non-template DNA strand. R-loops are involved in crucial physiological processes but can also be a source of genome instability if persistently unresolved. In this study, we demonstrate that PARP1 binds R-loops in vitro and associates with R-loop formation sites in cells which activates its ADP-ribosylation activity. Conversely, PARP1 inhibition or genetic depletion causes an accumulation of unresolved R-loops which promotes genomic instability. Our study reveals that PARP1 is a novel sensor for R-loops and highlights that PARP1 is a suppressor of R-loop-associated genomic instability.
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Affiliation(s)
- Natalie Laspata
- UPMC Hillman Cancer Center, University of Pittsburgh Cancer Institute, Department of Pharmacology and Chemical Biology, Pittsburgh, PA 15213, USA
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Parminder Kaur
- Physics Department, Raleigh, NC 27695, USA
- Center for Human Health and the Environment, Raleigh, NC 27695, USA
| | - Sofiane Yacine Mersaoui
- CHU de Québec Research Centre, HDQ Pavilion, Oncology Division, Laval University Cancer Research Center, McMahon, Québec City, Québec G1R 3S3, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Université Laval, Quebec, Canada
| | - Daniela Muoio
- UPMC Hillman Cancer Center, University of Pittsburgh Cancer Institute, Department of Pharmacology and Chemical Biology, Pittsburgh, PA 15213, USA
| | - Zhiyan Silvia Liu
- Department of Pharmacology, The Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA
| | - Maxwell Henry Bannister
- Department of Pharmacology, The Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA
| | - Hai Dang Nguyen
- Department of Pharmacology, The Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA
| | - Caroline Curry
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - John M Pascal
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Guy G Poirier
- Department of Molecular Biology, Medical Biochemistry and Pathology, Université Laval, Quebec, Canada
- CHU de Québec Research Centre, CHUL Pavilion, Oncology Division, Quebec, Canada
| | - Hong Wang
- Physics Department, Raleigh, NC 27695, USA
- Center for Human Health and the Environment, Raleigh, NC 27695, USA
- Toxicology Program, North Carolina State University, Raleigh, NC, USA
| | - Jean-Yves Masson
- CHU de Québec Research Centre, HDQ Pavilion, Oncology Division, Laval University Cancer Research Center, McMahon, Québec City, Québec G1R 3S3, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Université Laval, Quebec, Canada
| | - Elise Fouquerel
- UPMC Hillman Cancer Center, University of Pittsburgh Cancer Institute, Department of Pharmacology and Chemical Biology, Pittsburgh, PA 15213, USA
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10
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Fan C, Chen K, Wang Y, Ball EV, Stenson PD, Mort M, Bacolla A, Kehrer-Sawatzki H, Tainer JA, Cooper DN, Zhao H. Profiling human pathogenic repeat expansion regions by synergistic and multi-level impacts on molecular connections. Hum Genet 2023; 142:245-274. [PMID: 36344696 PMCID: PMC10290229 DOI: 10.1007/s00439-022-02500-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 10/24/2022] [Indexed: 11/09/2022]
Abstract
Whilst DNA repeat expansions cause numerous heritable human disorders, their origins and underlying pathological mechanisms are often unclear. We collated a dataset comprising 224 human repeat expansions encompassing 203 different genes, and performed a systematic analysis with respect to key topological features at the DNA, RNA and protein levels. Comparison with controls without known pathogenicity and genomic regions lacking repeats, allowed the construction of the first tool to discriminate repeat regions harboring pathogenic repeat expansions (DPREx). At the DNA level, pathogenic repeat expansions exhibited stronger signals for DNA regulatory factors (e.g. H3K4me3, transcription factor-binding sites) in exons, promoters, 5'UTRs and 5'genes but were not significantly different from controls in introns, 3'UTRs and 3'genes. Additionally, pathogenic repeat expansions were also found to be enriched in non-B DNA structures. At the RNA level, pathogenic repeat expansions were characterized by lower free energy for forming RNA secondary structure and were closer to splice sites in introns, exons, promoters and 5'genes than controls. At the protein level, pathogenic repeat expansions exhibited a preference to form coil rather than other types of secondary structure, and tended to encode surface-located protein domains. Guided by these features, DPREx ( http://biomed.nscc-gz.cn/zhaolab/geneprediction/# ) achieved an Area Under the Curve (AUC) value of 0.88 in a test on an independent dataset. Pathogenic repeat expansions are thus located such that they exert a synergistic influence on the gene expression pathway involving inter-molecular connections at the DNA, RNA and protein levels.
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Affiliation(s)
- Cong Fan
- Department of Medical Research Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, 107 Yan Jiang West Road, Guangzhou, 500001, People's Republic of China
| | - Ken Chen
- School of Computer Science and Engineering, Sun Yat-Sen University, Guangzhou, 500001, China
| | - Yukai Wang
- School of Life Science, Sun Yat-Sen University, Guangzhou, 500001, China
| | - Edward V Ball
- Institute of Medical Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK
| | - Peter D Stenson
- Institute of Medical Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK
| | - Matthew Mort
- Institute of Medical Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK
| | - Albino Bacolla
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, 6767 Bertner Avenue, Houston, TX, 77030, USA
| | | | - John A Tainer
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, 6767 Bertner Avenue, Houston, TX, 77030, USA
| | - David N Cooper
- Institute of Medical Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK
| | - Huiying Zhao
- Department of Medical Research Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, 107 Yan Jiang West Road, Guangzhou, 500001, People's Republic of China.
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11
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The length of uninterrupted CAG repeats in stem regions of repeat disease associated hairpins determines the amount of short CAG oligonucleotides that are toxic to cells through RNA interference. Cell Death Dis 2022; 13:1078. [PMID: 36585400 PMCID: PMC9803637 DOI: 10.1038/s41419-022-05494-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 11/30/2022] [Accepted: 12/05/2022] [Indexed: 12/31/2022]
Abstract
Extended CAG trinucleotide repeats (TNR) in the genes huntingtin (HTT) and androgen receptor (AR) are the cause of two progressive neurodegenerative disorders: Huntington's disease (HD) and Spinal and Bulbar Muscular Atrophy (SBMA), respectively. Anyone who inherits the mutant gene in the complete penetrance range (>39 repeats for HD and 44 for SBMA) will develop the disease. An inverse correlation exists between the length of the CAG repeat and the severity and age of onset of the diseases. Growing evidence suggests that it is the length of uninterrupted CAG repeats in the mRNA rather than the length of poly glutamine (polyQ) in mutant (m)HTT protein that determines disease progression. One variant of mHTT (loss of inhibition; LOI) causes a 25 year earlier onset of HD when compared to a reference sequence, despite both coding for a protein that contains an identical number of glutamines. Short 21-22 nt CAG repeat (sCAGs)-containing RNAs can cause disease through RNA interference (RNAi). RNA hairpins (HPs) forming at the CAG TNRs are stabilized by adjacent CCG (in HD) or CUG repeats (in SBMA) making them better substrates for Dicer, the enzyme that processes CAG HPs into sCAGs. We now show that cells deficient in Dicer or unable to mediate RNAi are resistant to the toxicity of the HTT and AR derived HPs. Expression of a small HP that mimics the HD LOI variant is more stable and more toxic than a reference HP. We report that the LOI HP is processed by Dicer, loaded into the RISC more efficiently, and gives rise to a higher quantity of RISC-bound 22 nt sCAGs. Our data support the notion that RNAi contributes to the cell death seen in HD and SBMA and provide an explanation for the dramatically reduced onset of disease in HD patients that carry the LOI variant.
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12
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Mirceta M, Shum N, Schmidt MHM, Pearson CE. Fragile sites, chromosomal lesions, tandem repeats, and disease. Front Genet 2022; 13:985975. [PMID: 36468036 PMCID: PMC9714581 DOI: 10.3389/fgene.2022.985975] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 09/02/2022] [Indexed: 09/16/2023] Open
Abstract
Expanded tandem repeat DNAs are associated with various unusual chromosomal lesions, despiralizations, multi-branched inter-chromosomal associations, and fragile sites. Fragile sites cytogenetically manifest as localized gaps or discontinuities in chromosome structure and are an important genetic, biological, and health-related phenomena. Common fragile sites (∼230), present in most individuals, are induced by aphidicolin and can be associated with cancer; of the 27 molecularly-mapped common sites, none are associated with a particular DNA sequence motif. Rare fragile sites ( ≳ 40 known), ≤ 5% of the population (may be as few as a single individual), can be associated with neurodevelopmental disease. All 10 molecularly-mapped folate-sensitive fragile sites, the largest category of rare fragile sites, are caused by gene-specific CGG/CCG tandem repeat expansions that are aberrantly CpG methylated and include FRAXA, FRAXE, FRAXF, FRA2A, FRA7A, FRA10A, FRA11A, FRA11B, FRA12A, and FRA16A. The minisatellite-associated rare fragile sites, FRA10B, FRA16B, can be induced by AT-rich DNA-ligands or nucleotide analogs. Despiralized lesions and multi-branched inter-chromosomal associations at the heterochromatic satellite repeats of chromosomes 1, 9, 16 are inducible by de-methylating agents like 5-azadeoxycytidine and can spontaneously arise in patients with ICF syndrome (Immunodeficiency Centromeric instability and Facial anomalies) with mutations in genes regulating DNA methylation. ICF individuals have hypomethylated satellites I-III, alpha-satellites, and subtelomeric repeats. Ribosomal repeats and subtelomeric D4Z4 megasatellites/macrosatellites, are associated with chromosome location, fragility, and disease. Telomere repeats can also assume fragile sites. Dietary deficiencies of folate or vitamin B12, or drug insults are associated with megaloblastic and/or pernicious anemia, that display chromosomes with fragile sites. The recent discovery of many new tandem repeat expansion loci, with varied repeat motifs, where motif lengths can range from mono-nucleotides to megabase units, could be the molecular cause of new fragile sites, or other chromosomal lesions. This review focuses on repeat-associated fragility, covering their induction, cytogenetics, epigenetics, cell type specificity, genetic instability (repeat instability, micronuclei, deletions/rearrangements, and sister chromatid exchange), unusual heritability, disease association, and penetrance. Understanding tandem repeat-associated chromosomal fragile sites provides insight to chromosome structure, genome packaging, genetic instability, and disease.
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Affiliation(s)
- Mila Mirceta
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Natalie Shum
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Monika H. M. Schmidt
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Christopher E. Pearson
- Program of Genetics and Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, ON, Canada
- Program of Molecular Genetics, University of Toronto, Toronto, ON, Canada
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13
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Masnovo C, Lobo AF, Mirkin SM. Replication dependent and independent mechanisms of GAA repeat instability. DNA Repair (Amst) 2022; 118:103385. [PMID: 35952488 PMCID: PMC9675320 DOI: 10.1016/j.dnarep.2022.103385] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 07/28/2022] [Accepted: 07/30/2022] [Indexed: 11/20/2022]
Abstract
Trinucleotide repeat instability is a driver of human disease. Large expansions of (GAA)n repeats in the first intron of the FXN gene are the cause Friedreich's ataxia (FRDA), a progressive degenerative disorder which cannot yet be prevented or treated. (GAA)n repeat instability arises during both replication-dependent processes, such as cell division and intergenerational transmission, as well as in terminally differentiated somatic tissues. Here, we provide a brief historical overview on the discovery of (GAA)n repeat expansions and their association to FRDA, followed by recent advances in the identification of triplex H-DNA formation and replication fork stalling. The main body of this review focuses on the last decade of progress in understanding the mechanism of (GAA)n repeat instability during DNA replication and/or DNA repair. We propose that the discovery of additional mechanisms of (GAA)n repeat instability can be achieved via both comparative approaches to other repeat expansion diseases and genome-wide association studies. Finally, we discuss the advances towards FRDA prevention or amelioration that specifically target (GAA)n repeat expansions.
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Affiliation(s)
- Chiara Masnovo
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Ayesha F Lobo
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, MA 02155, USA.
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14
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Belotserkovskii BP, Hanawalt PC. Topology and kinetics of R-loop formation. Biophys J 2022; 121:3345-3357. [PMID: 36004778 PMCID: PMC9515371 DOI: 10.1016/j.bpj.2022.08.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 07/06/2022] [Accepted: 08/18/2022] [Indexed: 11/19/2022] Open
Abstract
R-loops are structures containing an RNA-DNA duplex and an unpaired DNA strand. They can be formed upon "invasion" of an RNA strand into a DNA duplex, during which the RNA displaces the homologous DNA strand and binds the complementary strand. R-loops have many significant beneficial or deleterious biological effects, so it is important to understand the mechanisms for their generation and processing. We propose a model for co-transcriptional R-loop formation, in which their generation requires passage of the nascent RNA "tail" through the gap between the separated DNA strands. This passage becomes increasingly difficult with lengthening of the RNA tail. The length of the tail increases upon increasing distance between the transcription start site and the site of R-loop initiation. This causes reduced yields of R-loops with greater distance from the transcription start site. However, alternative pathways for R-loop formation are possible, involving either transient disruption of the transcription complex or the hypothetical formation of a triple-stranded structure, as a "collapsed R-loop." These alternative pathways could account for the fact that in many systems R-loops are observed very far from the transcription start site. Our model is consistent with experimental data and makes general predictions about the kinetics of R-loop formation.
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15
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Lobanov SV, McAllister B, McDade-Kumar M, Landwehrmeyer GB, Orth M, Rosser AE, Paulsen JS, Lee JM, MacDonald ME, Gusella JF, Long JD, Ryten M, Williams NM, Holmans P, Massey TH, Jones L. Huntington's disease age at motor onset is modified by the tandem hexamer repeat in TCERG1. NPJ Genom Med 2022; 7:53. [PMID: 36064847 PMCID: PMC9445028 DOI: 10.1038/s41525-022-00317-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 07/15/2022] [Indexed: 01/29/2023] Open
Abstract
Huntington's disease is caused by an expanded CAG tract in HTT. The length of the CAG tract accounts for over half the variance in age at onset of disease, and is influenced by other genetic factors, mostly implicating the DNA maintenance machinery. We examined a single nucleotide variant, rs79727797, on chromosome 5 in the TCERG1 gene, previously reported to be associated with Huntington's disease and a quasi-tandem repeat (QTR) hexamer in exon 4 of TCERG1 with a central pure repeat. We developed a method for calling perfect and imperfect repeats from exome-sequencing data, and tested association between the QTR in TCERG1 and residual age at motor onset (after correcting for the effects of CAG length in the HTT gene) in 610 individuals with Huntington's disease via regression analysis. We found a significant association between age at onset and the sum of the repeat lengths from both alleles of the QTR (p = 2.1 × 10-9), with each added repeat hexamer reducing age at onset by one year (95% confidence interval [0.7, 1.4]). This association explained that previously observed with rs79727797. The association with age at onset in the genome-wide association study is due to a QTR hexamer in TCERG1, translated to a glutamine/alanine tract in the protein. We could not distinguish whether this was due to cis-effects of the hexamer repeat on gene expression or of the encoded glutamine/alanine tract in the protein. These results motivate further study of the mechanisms by which TCERG1 modifies onset of HD.
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Affiliation(s)
- Sergey V Lobanov
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, UK
| | - Branduff McAllister
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, UK
| | - Mia McDade-Kumar
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, UK
| | | | - Michael Orth
- Department of Old Age Psychiatry and Psychotherapy, Bern University, Bern, Switzerland
- Swiss Huntington's Disease Centre, Siloah, Gümligen, Switzerland
| | - Anne E Rosser
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, UK
- School of Biosciences, Cardiff University, Cardiff, CF10 3AX, UK
| | - Jane S Paulsen
- Department of Neurology, University of Wisconsin, Madison, WI53705, USA
| | - Jong-Min Lee
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA, 02115, USA
- Medical and Population Genetics Program, Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA
| | - Marcy E MacDonald
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Neurology, Harvard Medical School, Boston, MA, 02115, USA
- Medical and Population Genetics Program, Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA
| | - James F Gusella
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Medical and Population Genetics Program, Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, 02115, USA
| | - Jeffrey D Long
- Departments of Psychiatry and Biostatistics, University of Iowa, Iowa City, IA, USA
| | - Mina Ryten
- Great Ormond Street Institute of Child Health, Genetics and Genomic Medicine, University, College London, London, UK
- NIHR Great Ormond Street Hospital Biomedical Research Centre, University College London, London, UK
| | - Nigel M Williams
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, UK
| | - Peter Holmans
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, UK
| | - Thomas H Massey
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, UK.
| | - Lesley Jones
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, UK
- UK Dementia Research Institute at Cardiff, Cardiff University, Cardiff, UK
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16
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Nickoloff JA. Targeting Replication Stress Response Pathways to Enhance Genotoxic Chemo- and Radiotherapy. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27154736. [PMID: 35897913 PMCID: PMC9330692 DOI: 10.3390/molecules27154736] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 07/20/2022] [Accepted: 07/22/2022] [Indexed: 12/12/2022]
Abstract
Proliferating cells regularly experience replication stress caused by spontaneous DNA damage that results from endogenous reactive oxygen species (ROS), DNA sequences that can assume secondary and tertiary structures, and collisions between opposing transcription and replication machineries. Cancer cells face additional replication stress, including oncogenic stress that results from the dysregulation of fork progression and origin firing, and from DNA damage induced by radiotherapy and most cancer chemotherapeutic agents. Cells respond to such stress by activating a complex network of sensor, signaling and effector pathways that protect genome integrity. These responses include slowing or stopping active replication forks, protecting stalled replication forks from collapse, preventing late origin replication firing, stimulating DNA repair pathways that promote the repair and restart of stalled or collapsed replication forks, and activating dormant origins to rescue adjacent stressed forks. Currently, most cancer patients are treated with genotoxic chemotherapeutics and/or ionizing radiation, and cancer cells can gain resistance to the resulting replication stress by activating pro-survival replication stress pathways. Thus, there has been substantial effort to develop small molecule inhibitors of key replication stress proteins to enhance tumor cell killing by these agents. Replication stress targets include ATR, the master kinase that regulates both normal replication and replication stress responses; the downstream signaling kinase Chk1; nucleases that process stressed replication forks (MUS81, EEPD1, Metnase); the homologous recombination catalyst RAD51; and other factors including ATM, DNA-PKcs, and PARP1. This review provides an overview of replication stress response pathways and discusses recent pre-clinical studies and clinical trials aimed at improving cancer therapy by targeting replication stress response factors.
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Affiliation(s)
- Jac A Nickoloff
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO 80523, USA
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17
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Nickoloff JA, Sharma N, Taylor L, Allen SJ, Hromas R. Nucleases and Co-Factors in DNA Replication Stress Responses. DNA 2022; 2:68-85. [PMID: 36203968 PMCID: PMC9534323 DOI: 10.3390/dna2010006] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
DNA replication stress is a constant threat that cells must manage to proliferate and maintain genome integrity. DNA replication stress responses, a subset of the broader DNA damage response (DDR), operate when the DNA replication machinery (replisome) is blocked or replication forks collapse during S phase. There are many sources of replication stress, such as DNA lesions caused by endogenous and exogenous agents including commonly used cancer therapeutics, and difficult-to-replicate DNA sequences comprising fragile sites, G-quadraplex DNA, hairpins at trinucleotide repeats, and telomeres. Replication stress is also a consequence of conflicts between opposing transcription and replication, and oncogenic stress which dysregulates replication origin firing and fork progression. Cells initially respond to replication stress by protecting blocked replisomes, but if the offending problem (e.g., DNA damage) is not bypassed or resolved in a timely manner, forks may be cleaved by nucleases, inducing a DNA double-strand break (DSB) and providing a means to accurately restart stalled forks via homologous recombination. However, DSBs pose their own risks to genome stability if left unrepaired or misrepaired. Here we focus on replication stress response systems, comprising DDR signaling, fork protection, and fork processing by nucleases that promote fork repair and restart. Replication stress nucleases include MUS81, EEPD1, Metnase, CtIP, MRE11, EXO1, DNA2-BLM, SLX1-SLX4, XPF-ERCC1-SLX4, Artemis, XPG, and FEN1. Replication stress factors are important in cancer etiology as suppressors of genome instability associated with oncogenic mutations, and as potential cancer therapy targets to enhance the efficacy of chemo- and radiotherapeutics.
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Affiliation(s)
- Jac A. Nickoloff
- Department of Environmental and Radiological Health Sciences, Colorado State University, Ft. Collins, CO 80523, USA
| | - Neelam Sharma
- Department of Environmental and Radiological Health Sciences, Colorado State University, Ft. Collins, CO 80523, USA
| | - Lynn Taylor
- Department of Environmental and Radiological Health Sciences, Colorado State University, Ft. Collins, CO 80523, USA
| | - Sage J. Allen
- Department of Environmental and Radiological Health Sciences, Colorado State University, Ft. Collins, CO 80523, USA
| | - Robert Hromas
- Division of Hematology and Medical Oncology, Department of Medicine and the Mays Cancer Center, University of Texas Health Science Center, San Antonio, TX 78229, USA
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18
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Abstract
The XPG/ERCC5 endonuclease was originally identified as the causative gene for Xeroderma Pigmentosum complementation group G. Ever since its discovery, in depth biochemical, structural and cell biological studies have provided detailed mechanistic insight into its function in excising DNA damage in nucleotide excision repair, together with the ERCC1–XPF endonuclease. In recent years, it has become evident that XPG has additional important roles in genome maintenance that are independent of its function in NER, as XPG has been implicated in protecting replication forks by promoting homologous recombination as well as in resolving R-loops. Here, we provide an overview of the multitasking of XPG in genome maintenance, by describing in detail how its activity in NER is regulated and the evidence that points to important functions outside of NER. Furthermore, we present the various disease phenotypes associated with inherited XPG deficiency and discuss current ideas on how XPG deficiency leads to these different types of disease.
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19
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Zardoni L, Nardini E, Brambati A, Lucca C, Choudhary R, Loperfido F, Sabbioneda S, Liberi G. Elongating RNA polymerase II and RNA:DNA hybrids hinder fork progression and gene expression at sites of head-on replication-transcription collisions. Nucleic Acids Res 2021; 49:12769-12784. [PMID: 34878142 PMCID: PMC8682787 DOI: 10.1093/nar/gkab1146] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 10/26/2021] [Accepted: 11/02/2021] [Indexed: 11/20/2022] Open
Abstract
Uncoordinated clashes between replication forks and transcription cause replication stress and genome instability, which are hallmarks of cancer and neurodegeneration. Here, we investigate the outcomes of head-on replication-transcription collisions, using as a model system budding yeast mutants for the helicase Sen1, the ortholog of human Senataxin. We found that RNA Polymerase II accumulates together with RNA:DNA hybrids at sites of head-on collisions. The replication fork and RNA Polymerase II are both arrested during the clash, leading to DNA damage and, in the long run, the inhibition of gene expression. The inactivation of RNA Polymerase II elongation factors, such as the HMG-like protein Spt2 and the DISF and PAF complexes, but not alterations in chromatin structure, allows replication fork progression through transcribed regions. Attenuation of RNA Polymerase II elongation rescues RNA:DNA hybrid accumulation and DNA damage sensitivity caused by the absence of Sen1, but not of RNase H proteins, suggesting that such enzymes counteract toxic RNA:DNA hybrids at different stages of the cell cycle with Sen1 mainly acting in replication. We suggest that the main obstacle to replication fork progression is the elongating RNA Polymerase II engaged in an R-loop, rather than RNA:DNA hybrids per se or hybrid-associated chromatin modifications.
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Affiliation(s)
- Luca Zardoni
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", CNR, 27100 Pavia, Italy.,Scuola Universitaria Superiore IUSS, 27100 Pavia, Italy
| | - Eleonora Nardini
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", CNR, 27100 Pavia, Italy
| | - Alessandra Brambati
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", CNR, 27100 Pavia, Italy
| | | | | | - Federica Loperfido
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", CNR, 27100 Pavia, Italy
| | - Simone Sabbioneda
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", CNR, 27100 Pavia, Italy
| | - Giordano Liberi
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", CNR, 27100 Pavia, Italy.,IFOM Foundation, 20139 Milan, Italy
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20
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Paull TT. DNA damage and regulation of protein homeostasis. DNA Repair (Amst) 2021; 105:103155. [PMID: 34116476 DOI: 10.1016/j.dnarep.2021.103155] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 06/01/2021] [Accepted: 06/02/2021] [Indexed: 10/21/2022]
Abstract
The accumulation of unrepaired DNA lesions is associated with many pathological outcomes in humans, particularly in neurodegenerative diseases and in normal aging. Evidence supporting a causal role for DNA damage in the onset and progression of neurodegenerative disease has come from rare human patients with mutations in DNA damage response genes as well as from model organisms; however, the generality of this relationship in the normal population is unclear. In addition, the relevance of DNA damage in the context of proteotoxic stress-the widely accepted paradigm for pathology during neurodegeneration-is not well understood. Here, observations supporting intertwined roles of DNA damage and proteotoxicity in aging-related neurological outcomes are reviewed, with particular emphasis on recent insights into the relationships between DNA repair and autophagy, the ubiquitin proteasome system, formation of protein aggregates, poly-ADP-ribose polymerization, and transcription-driven DNA lesions.
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Affiliation(s)
- Tanya T Paull
- The University of Texas at Austin, Department of Molecular Biosciences, Austin, TX, 78712, United States.
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21
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Deshmukh AL, Porro A, Mohiuddin M, Lanni S, Panigrahi GB, Caron MC, Masson JY, Sartori AA, Pearson CE. FAN1, a DNA Repair Nuclease, as a Modifier of Repeat Expansion Disorders. J Huntingtons Dis 2021; 10:95-122. [PMID: 33579867 PMCID: PMC7990447 DOI: 10.3233/jhd-200448] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
FAN1 encodes a DNA repair nuclease. Genetic deficiencies, copy number variants, and single nucleotide variants of FAN1 have been linked to karyomegalic interstitial nephritis, 15q13.3 microdeletion/microduplication syndrome (autism, schizophrenia, and epilepsy), cancer, and most recently repeat expansion diseases. For seven CAG repeat expansion diseases (Huntington's disease (HD) and certain spinocerebellar ataxias), modification of age of onset is linked to variants of specific DNA repair proteins. FAN1 variants are the strongest modifiers. Non-coding disease-delaying FAN1 variants and coding disease-hastening variants (p.R507H and p.R377W) are known, where the former may lead to increased FAN1 levels and the latter have unknown effects upon FAN1 functions. Current thoughts are that ongoing repeat expansions in disease-vulnerable tissues, as individuals age, promote disease onset. Fan1 is required to suppress against high levels of ongoing somatic CAG and CGG repeat expansions in tissues of HD and FMR1 transgenic mice respectively, in addition to participating in DNA interstrand crosslink repair. FAN1 is also a modifier of autism, schizophrenia, and epilepsy. Coupled with the association of these diseases with repeat expansions, this suggests a common mechanism, by which FAN1 modifies repeat diseases. Yet how any of the FAN1 variants modify disease is unknown. Here, we review FAN1 variants, associated clinical effects, protein structure, and the enzyme's attributed functional roles. We highlight how variants may alter its activities in DNA damage response and/or repeat instability. A thorough awareness of the FAN1 gene and FAN1 protein functions will reveal if and how it may be targeted for clinical benefit.
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Affiliation(s)
- Amit L Deshmukh
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
| | - Antonio Porro
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Mohiuddin Mohiuddin
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
| | - Stella Lanni
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
| | - Gagan B Panigrahi
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada
| | - Marie-Christine Caron
- Department of Molecular Biology, Medical Biochemistry and Pathology; Laval University Cancer Research Center, Québec City, Quebec, Canada.,Genome Stability Laboratory, CHU de Québec Research Center, HDQ Pavilion, Oncology Division, Québec City, Quebec, Canada
| | - Jean-Yves Masson
- Department of Molecular Biology, Medical Biochemistry and Pathology; Laval University Cancer Research Center, Québec City, Quebec, Canada.,Genome Stability Laboratory, CHU de Québec Research Center, HDQ Pavilion, Oncology Division, Québec City, Quebec, Canada
| | - Alessandro A Sartori
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Christopher E Pearson
- Program of Genetics & Genome Biology, The Hospital for Sick Children, The Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada.,University of Toronto, Program of Molecular Genetics, Toronto, Ontario, Canada
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22
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Transcription Inhibition by PNA-Induced R-Loops. Methods Mol Biol 2021; 2105:141-155. [PMID: 32088868 DOI: 10.1007/978-1-0716-0243-0_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
R-loops are structures consisting of an RNA-DNA duplex and an unpaired DNA strand. They can form during transcription upon nascent RNA "threadback" invasion into the DNA duplex to displace the non-template DNA strand. R-loops occur naturally in all kingdoms of life, and they have multiple biological effects. Therefore, it is of interest to study the artificial induction of R-loops and to monitor their effects in model in vitro systems to learn mechanisms. Here we describe transcription blockage in vitro by R-loop formation induced by peptide nucleic acid (PNA) binding to the non-template DNA strand.
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23
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Rinaldi C, Pizzul P, Longhese MP, Bonetti D. Sensing R-Loop-Associated DNA Damage to Safeguard Genome Stability. Front Cell Dev Biol 2021; 8:618157. [PMID: 33505970 PMCID: PMC7829580 DOI: 10.3389/fcell.2020.618157] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 12/02/2020] [Indexed: 12/14/2022] Open
Abstract
DNA transcription and replication are two essential physiological processes that can turn into a threat for genome integrity when they compete for the same DNA substrate. During transcription, the nascent RNA strongly binds the template DNA strand, leading to the formation of a peculiar RNA-DNA hybrid structure that displaces the non-template single-stranded DNA. This three-stranded nucleic acid transition is called R-loop. Although a programed formation of R-loops plays important physiological functions, these structures can turn into sources of DNA damage and genome instability when their homeostasis is altered. Indeed, both R-loop level and distribution in the genome are tightly controlled, and the list of factors involved in these regulatory mechanisms is continuously growing. Over the last years, our knowledge of R-loop homeostasis regulation (formation, stabilization, and resolution) has definitely increased. However, how R-loops affect genome stability and how the cellular response to their unscheduled formation is orchestrated are still not fully understood. In this review, we will report and discuss recent findings about these questions and we will focus on the role of ATM- and Rad3-related (ATR) and Ataxia-telangiectasia-mutated (ATM) kinases in the activation of an R-loop-dependent DNA damage response.
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Affiliation(s)
- Carlo Rinaldi
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Milan, Italy
| | - Paolo Pizzul
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Milan, Italy
| | - Maria Pia Longhese
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Milan, Italy
| | - Diego Bonetti
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Milan, Italy
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24
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Giannini M, Bayona-Feliu A, Sproviero D, Barroso SI, Cereda C, Aguilera A. TDP-43 mutations link Amyotrophic Lateral Sclerosis with R-loop homeostasis and R loop-mediated DNA damage. PLoS Genet 2020; 16:e1009260. [PMID: 33301444 PMCID: PMC7755276 DOI: 10.1371/journal.pgen.1009260] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 12/22/2020] [Accepted: 11/08/2020] [Indexed: 12/16/2022] Open
Abstract
TDP-43 is a DNA and RNA binding protein involved in RNA processing and with structural resemblance to heterogeneous ribonucleoproteins (hnRNPs), whose depletion sensitizes neurons to double strand DNA breaks (DSBs). Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disorder, in which 97% of patients are familial and sporadic cases associated with TDP-43 proteinopathies and conditions clearing TDP-43 from the nucleus, but we know little about the molecular basis of the disease. After showing with the non-neuronal model of HeLa cells that TDP-43 depletion increases R loops and associated genome instability, we prove that mislocalization of mutated TDP-43 (A382T) in transfected neuronal SH-SY5Y and lymphoblastoid cell lines (LCLs) from an ALS patient cause R-loop accumulation, R loop-dependent increased DSBs and Fanconi Anemia repair centers. These results uncover a new role of TDP-43 in the control of co-transcriptional R loops and the maintenance of genome integrity by preventing harmful R-loop accumulation. Our findings thus link TDP-43 pathology to increased R loops and R loop-mediated DNA damage opening the possibility that R-loop modulation in TDP-43-defective cells might help develop ALS therapies. Amyotrophic Lateral Sclerosis (ALS) is an adult onset, progressive neurodegenerative disease, caused by the selective loss of upper and lower motor neurons in the cerebral cortex, brainstem and spinal cord. The nuclear TDP-43 RNA binding protein, is encoded by a major gene for ALS susceptibility whose mutations are found in 3% of familial and 2% of sporadic ALS cases. Thanks to its ability to recognize DNA and RNA, TDP-43 is involved in different steps of mRNA metabolism and in several mechanisms of genome integrity. This, together with the fact that R loops or DNA-RNA hybrids are a common source of genome instability, prompted us to investigate whether TDP-43 deficiency has any role in R loop homeostasis that could explain previously described DNA damage response defects of ALS cells. We show that TDP-43 plays a role in preventing R loop-accumulation and associated genome instability in neuronal and non-neuronal cells, as well as in patient cell lines. Thus, our study opens the possibility that R loop-modulation in TDP-43-defective cells might help develop ALS therapies.
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Affiliation(s)
- Marta Giannini
- Genomic and Post-Genomic Center, IRCCS Mondino Foundation, Pavia, Italy
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
| | - Aleix Bayona-Feliu
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Daisy Sproviero
- Genomic and Post-Genomic Center, IRCCS Mondino Foundation, Pavia, Italy
| | - Sonia I. Barroso
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
| | - Cristina Cereda
- Genomic and Post-Genomic Center, IRCCS Mondino Foundation, Pavia, Italy
- * E-mail: (CC); (AA)
| | - Andrés Aguilera
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
- * E-mail: (CC); (AA)
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25
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Brown RE, Freudenreich CH. Structure-forming repeats and their impact on genome stability. Curr Opin Genet Dev 2020; 67:41-51. [PMID: 33279816 DOI: 10.1016/j.gde.2020.10.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 10/22/2020] [Accepted: 10/24/2020] [Indexed: 12/12/2022]
Abstract
Repetitive sequences throughout the genome are a major source of endogenous DNA damage, due to the propensity of many of them to form alternative non-B DNA structures that can interfere with replication, transcription, and DNA repair. These repetitive sequences are prone to breakage (fragility) and instability (changes in repeat number). Repeat fragility and expansions are linked to several diseases, including many cancers and neurodegenerative diseases, hence the importance of understanding the mechanisms that cause genome instability and contribute to these diseases. This review focuses on recent findings of mechanisms causing repeat fragility and instability, new associations between repeat expansions and genetic diseases, and potential therapeutic options to target repeat expansions.
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Affiliation(s)
- Rebecca E Brown
- Program in Genetics, Tufts University Graduate School of Biomedical Sciences, Boston, MA 02111, USA
| | - Catherine H Freudenreich
- Department of Biology, Tufts University, Medford, MA 02155, USA; Program in Genetics, Tufts University Graduate School of Biomedical Sciences, Boston, MA 02111, USA.
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26
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Linthorst J, Meert W, Hestand MS, Korlach J, Vermeesch JR, Reinders MJT, Holstege H. Extreme enrichment of VNTR-associated polymorphicity in human subtelomeres: genes with most VNTRs are predominantly expressed in the brain. Transl Psychiatry 2020; 10:369. [PMID: 33139705 PMCID: PMC7608644 DOI: 10.1038/s41398-020-01060-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 08/27/2020] [Accepted: 09/22/2020] [Indexed: 12/13/2022] Open
Abstract
The human genome harbors numerous structural variants (SVs) which, due to their repetitive nature, are currently underexplored in short-read whole-genome sequencing approaches. Using single-molecule, real-time (SMRT) long-read sequencing technology in combination with FALCON-Unzip, we generated a de novo assembly of the diploid genome of a 115-year-old Dutch cognitively healthy woman. We combined this assembly with two previously published haploid assemblies (CHM1 and CHM13) and the GRCh38 reference genome to create a compendium of SVs that occur across five independent human haplotypes using the graph-based multi-genome aligner REVEAL. Across these five haplotypes, we detected 31,680 euchromatic SVs (>50 bp). Of these, ~62% were comprised of repetitive sequences with 'variable number tandem repeats' (VNTRs), ~10% were mobile elements (Alu, L1, and SVA), while the remaining variants were inversions and indels. We observed that VNTRs with GC-content >60% and repeat patterns longer than 15 bp were 21-fold enriched in the subtelomeric regions (within 5 Mb of the ends of chromosome arms). VNTR lengths can expand to exceed a critical length which is associated with impaired gene transcription. The genes that contained most VNTRs, of which PTPRN2 and DLGAP2 are the most prominent examples, were found to be predominantly expressed in the brain and associated with a wide variety of neurological disorders. Repeat-induced variation represents a sizeable fraction of the genetic variation in human genomes and should be included in investigations of genetic factors associated with phenotypic traits, specifically those associated with neurological disorders. We make available the long and short-read sequence data of the supercentenarian genome, and a compendium of SVs as identified across 5 human haplotypes.
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Affiliation(s)
- Jasper Linthorst
- grid.484519.5Department of Clinical Genetics, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, Amsterdam UMC, Amsterdam, The Netherlands ,grid.5292.c0000 0001 2097 4740Delft Bioinformatics Lab, Delft University of Technology, Delft, The Netherlands
| | - Wim Meert
- grid.5596.f0000 0001 0668 7884Department of Human Genetics, KU Leuven, Leuven, Belgium
| | - Matthew S. Hestand
- grid.5596.f0000 0001 0668 7884Department of Human Genetics, KU Leuven, Leuven, Belgium
| | - Jonas Korlach
- grid.423340.20000 0004 0640 9878Pacific Biosciences, Menlo Park, CA USA
| | | | - Marcel J. T. Reinders
- grid.5292.c0000 0001 2097 4740Delft Bioinformatics Lab, Delft University of Technology, Delft, The Netherlands
| | - Henne Holstege
- Department of Clinical Genetics, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, Amsterdam UMC, Amsterdam, The Netherlands. .,Delft Bioinformatics Lab, Delft University of Technology, Delft, The Netherlands. .,Alzheimer Center Amsterdam, Department of Neurology, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, Amsterdam UMC, Amsterdam, The Netherlands.
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27
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Abstract
Systematics is described for annotation of variations in RNA molecules. The conceptual framework is part of Variation Ontology (VariO) and facilitates depiction of types of variations, their functional and structural effects and other consequences in any RNA molecule in any organism. There are more than 150 RNA related VariO terms in seven levels, which can be further combined to generate even more complicated and detailed annotations. The terms are described together with examples, usually for variations and effects in human and in diseases. RNA variation type has two subcategories: variation classification and origin with subterms. Altogether six terms are available for function description. Several terms are available for affected RNA properties. The ontology contains also terms for structural description for affected RNA type, post-transcriptional RNA modifications, secondary and tertiary structure effects and RNA sugar variations. Together with the DNA and protein concepts and annotations, RNA terms allow comprehensive description of variations of genetic and non-genetic origin at all possible levels. The VariO annotations are readable both for humans and computer programs for advanced data integration and mining.
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Affiliation(s)
- Mauno Vihinen
- Department of Experimental Medical Science, Lund University, Lund, Sweden
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28
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Meers C, Keskin H, Banyai G, Mazina O, Yang T, Gombolay AL, Mukherjee K, Kaparos EI, Newnam G, Mazin A, Storici F. Genetic Characterization of Three Distinct Mechanisms Supporting RNA-Driven DNA Repair and Modification Reveals Major Role of DNA Polymerase ζ. Mol Cell 2020; 79:1037-1050.e5. [PMID: 32882183 DOI: 10.1016/j.molcel.2020.08.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 06/30/2020] [Accepted: 08/12/2020] [Indexed: 01/08/2023]
Abstract
DNA double-stranded breaks (DSBs) are dangerous lesions threatening genomic stability. Fidelity of DSB repair is best achieved by recombination with a homologous template sequence. In yeast, transcript RNA was shown to template DSB repair of DNA. However, molecular pathways of RNA-driven repair processes remain obscure. Utilizing assays of RNA-DNA recombination with and without an induced DSB in yeast DNA, we characterize three forms of RNA-mediated genomic modifications: RNA- and cDNA-templated DSB repair (R-TDR and c-TDR) using an RNA transcript or a DNA copy of the RNA transcript for DSB repair, respectively, and a new mechanism of RNA-templated DNA modification (R-TDM) induced by spontaneous or mutagen-induced breaks. While c-TDR requires reverse transcriptase, translesion DNA polymerase ζ (Pol ζ) plays a major role in R-TDR, and it is essential for R-TDM. This study characterizes mechanisms of RNA-DNA recombination, uncovering a role of Pol ζ in transferring genetic information from transcript RNA to DNA.
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Affiliation(s)
- Chance Meers
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Havva Keskin
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Gabor Banyai
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Olga Mazina
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Taehwan Yang
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Alli L Gombolay
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Kuntal Mukherjee
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Efiyenia I Kaparos
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Gary Newnam
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Alexander Mazin
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - Francesca Storici
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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29
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30
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Structures and stability of simple DNA repeats from bacteria. Biochem J 2020; 477:325-339. [PMID: 31967649 PMCID: PMC7015867 DOI: 10.1042/bcj20190703] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 12/20/2019] [Accepted: 01/03/2020] [Indexed: 01/12/2023]
Abstract
DNA is a fundamentally important molecule for all cellular organisms due to its biological role as the store of hereditary, genetic information. On the one hand, genomic DNA is very stable, both in chemical and biological contexts, and this assists its genetic functions. On the other hand, it is also a dynamic molecule, and constant changes in its structure and sequence drive many biological processes, including adaptation and evolution of organisms. DNA genomes contain significant amounts of repetitive sequences, which have divergent functions in the complex processes that involve DNA, including replication, recombination, repair, and transcription. Through their involvement in these processes, repetitive DNA sequences influence the genetic instability and evolution of DNA molecules and they are located non-randomly in all genomes. Mechanisms that influence such genetic instability have been studied in many organisms, including within human genomes where they are linked to various human diseases. Here, we review our understanding of short, simple DNA repeats across a diverse range of bacteria, comparing the prevalence of repetitive DNA sequences in different genomes. We describe the range of DNA structures that have been observed in such repeats, focusing on their propensity to form local, non-B-DNA structures. Finally, we discuss the biological significance of such unusual DNA structures and relate this to studies where the impacts of DNA metabolism on genetic stability are linked to human diseases. Overall, we show that simple DNA repeats in bacteria serve as excellent and tractable experimental models for biochemical studies of their cellular functions and influences.
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31
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Lai Y, Lei R, Ren Y, Liu Y. Methods to Study Trinucleotide Repeat Instability Induced by DNA Damage and Repair. Methods Mol Biol 2020; 1999:87-101. [PMID: 31127571 DOI: 10.1007/978-1-4939-9500-4_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Trinucleotide repeat (TNR) instability (expansion and deletion) is associated with more than 42 human neurodegenerative diseases and cancer and mediated by DNA replication, repair, recombination, and gene transcription. Somatic TNR instability is involved in the progression of TNR expansion diseases and can be modulated by DNA damage repair and gene transcription. Recent studies from our group and others have shown that DNA base damage and its repair play an active role in modulating TNR instability and are responsible for somatic age-dependent CAG repeat expansion in neurons of Huntington's disease mice induced by oxidative DNA damage. However, it remains to be elucidated how DNA damage, non-B form DNA structures, and DNA repair enzymes and cofactors can coordinate to regulate somatic TNR instability. Understanding the molecular mechanisms underlying DNA damage and repair-mediated somatic TNR instability is critically important for identification of new therapeutic targets for treatment and prevention of TNR-related diseases. Here we describe the methods to study the locations and distribution of DNA base lesions and their effects on TNR instability through DNA base excision repair in in vitro reconstituted human systems.
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Affiliation(s)
- Yanhao Lai
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL, USA
| | - Ruipeng Lei
- Biochemistry Ph.D. Program, Florida International University, Miami, FL, USA
| | - Yaou Ren
- Biochemistry Ph.D. Program, Florida International University, Miami, FL, USA
| | - Yuan Liu
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL, USA. .,Biochemistry Ph.D. Program, Florida International University, Miami, FL, USA. .,Biomolecular Sciences Institute, Florida International University, Miami, FL, USA.
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32
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Brambati A, Zardoni L, Nardini E, Pellicioli A, Liberi G. The dark side of RNA:DNA hybrids. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2020; 784:108300. [PMID: 32430097 DOI: 10.1016/j.mrrev.2020.108300] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 02/07/2020] [Accepted: 02/23/2020] [Indexed: 12/15/2022]
Abstract
RNA:DNA hybrids form when nascent transcripts anneal to the DNA template strand or any homologous DNA region. Co-transcriptional RNA:DNA hybrids, organized in R-loop structures together with the displaced non-transcribed strand, assist gene expression, DNA repair and other physiological cellular functions. A dark side of the matter is that RNA:DNA hybrids are also a cause of DNA damage and human diseases. In this review, we summarize recent advances in the understanding of the mechanisms by which the impairment of hybrid turnover promotes DNA damage and genome instability via the interference with DNA replication and DNA double-strand break repair. We also discuss how hybrids could contribute to cancer, neurodegeneration and susceptibility to viral infections, focusing on dysfunctions associated with the anti-R-loop helicase Senataxin.
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Affiliation(s)
- Alessandra Brambati
- Istituto di Genetica Molecolare Luigi Luca Cavalli-Sforza, CNR, Via Abbiategrasso 207, 27100, Pavia, Italy.
| | - Luca Zardoni
- Istituto di Genetica Molecolare Luigi Luca Cavalli-Sforza, CNR, Via Abbiategrasso 207, 27100, Pavia, Italy; Scuola Universitaria Superiore, IUSS, 27100, Pavia, Italy
| | - Eleonora Nardini
- Istituto di Genetica Molecolare Luigi Luca Cavalli-Sforza, CNR, Via Abbiategrasso 207, 27100, Pavia, Italy
| | - Achille Pellicioli
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milan, Italy
| | - Giordano Liberi
- Istituto di Genetica Molecolare Luigi Luca Cavalli-Sforza, CNR, Via Abbiategrasso 207, 27100, Pavia, Italy; IFOM Foundation, Via Adamello 16, 20139, Milan, Italy.
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33
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Regulatory R-loops as facilitators of gene expression and genome stability. Nat Rev Mol Cell Biol 2020; 21:167-178. [PMID: 32005969 DOI: 10.1038/s41580-019-0206-3] [Citation(s) in RCA: 258] [Impact Index Per Article: 64.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/17/2019] [Indexed: 12/23/2022]
Abstract
R-loops are three-stranded structures that harbour an RNA-DNA hybrid and frequently form during transcription. R-loop misregulation is associated with DNA damage, transcription elongation defects, hyper-recombination and genome instability. In contrast to such 'unscheduled' R-loops, evidence is mounting that cells harness the presence of RNA-DNA hybrids in scheduled, 'regulatory' R-loops to promote DNA transactions, including transcription termination and other steps of gene regulation, telomere stability and DNA repair. R-loops formed by cellular RNAs can regulate histone post-translational modification and may be recognized by dedicated reader proteins. The two-faced nature of R-loops implies that their formation, location and timely removal must be tightly regulated. In this Perspective, we discuss the cellular processes that regulatory R-loops modulate, the regulation of R-loops and the potential differences that may exist between regulatory R-loops and unscheduled R-loops.
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34
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Cinesi C, Yang B, Dion V. GFP Reporters to Monitor Instability and Expression of Expanded CAG/CTG Repeats. Methods Mol Biol 2020; 2056:255-268. [PMID: 31586353 DOI: 10.1007/978-1-4939-9784-8_16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Expanded CAG/CTG repeats are genetically unstable and, upon expression, cause neurological and neuromuscular diseases. The molecular mechanisms of repeat instability and expression remain poorly understood despite their importance for the pathogenesis of a family of 14 devastating human diseases. This is in part because conventional assays are tedious and time-consuming. Recently, however, GFP-based reporters have been designed to provide a rapid and reliable means of assessing these parameters. Here we provide protocols for quantifying repeat instability and expression using a GFP-based chromosomal reporter and the newly developed ParB/ANCHOR-mediated Inducible Targeting (PInT) and how to validate the results.
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Affiliation(s)
- Cinzia Cinesi
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Bin Yang
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Vincent Dion
- Dementia Research Institute, Cardiff University, Cardiff, UK.
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35
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Maizels N, Davis L. Initiation of homologous recombination at DNA nicks. Nucleic Acids Res 2019; 46:6962-6973. [PMID: 29986051 PMCID: PMC6101574 DOI: 10.1093/nar/gky588] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 07/04/2018] [Indexed: 12/14/2022] Open
Abstract
Discontinuities in only a single strand of the DNA duplex occur frequently, as a result of DNA damage or as intermediates in essential nuclear processes and DNA repair. Nicks are the simplest of these lesions: they carry clean ends bearing 3′-hydroxyl groups that can undergo ligation or prime new DNA synthesis. In contrast, single-strand breaks also interrupt only one DNA strand, but they carry damaged ends that require clean-up before subsequent steps in repair. Despite their apparent simplicity, nicks can have significant consequences for genome stability. The availability of enzymes that can introduce a nick almost anywhere in a large genome now makes it possible to systematically analyze repair of nicks. Recent experiments demonstrate that nicks can initiate recombination via pathways distinct from those active at double-strand breaks (DSBs). Recombination at targeted DNA nicks can be very efficient, and because nicks are intrinsically less mutagenic than DSBs, nick-initiated gene correction is useful for genome engineering and gene therapy. This review revisits some physiological examples of recombination at nicks, and outlines experiments that have demonstrated that nicks initiate homology-directed repair by distinctive pathways, emphasizing research that has contributed to our current mechanistic understanding of recombination at nicks in mammalian cells.
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Affiliation(s)
- Nancy Maizels
- Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195, USA.,Department of Biochemistry, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Luther Davis
- Department of Immunology, University of Washington School of Medicine, Seattle, WA 98195, USA
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36
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Infantino V, Stutz F. The functional complexity of the RNA-binding protein Yra1: mRNA biogenesis, genome stability and DSB repair. Curr Genet 2019; 66:63-71. [PMID: 31292684 DOI: 10.1007/s00294-019-01011-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 06/27/2019] [Accepted: 06/28/2019] [Indexed: 12/21/2022]
Abstract
The mRNA export adaptor Yra1 is essential in S. cerevisiae, and conserved from yeast to human (ALY/REF). It is well characterized for its function during transcription elongation, 3' processing and mRNA export. Recently, different studies linked Yra1 to genome stability showing that Yra1 overexpression causes DNA Double Strand Breaks through DNA:RNA hybrids stabilization, and that Yra1 depletion affects DSB repair. However, the mechanisms through which Yra1 contributes to genome stability maintenance are not fully understood. Interestingly, our results showed that the Yra1 C-box domain is required for Yra1 recruitment to an HO-induced irreparable DSB following extensive resection, and that it is essential to repair an HO-induced reparable DSB. Furthermore, we defined that the C-box domain of Yra1 plays a crucial role in DSB repair through homologous recombination but not through non-homologous end joining. Future studies aim at deciphering the mechanism by which Yra1 contributes to DSB repair by searching for Yra1 partners important for this process. This review focuses on the functional complexity of the Yra1 protein, not only summarizing its role in mRNA biogenesis but also emphasizing its auto-regulation and implication in genome integrity either through DNA:RNA hybrids stabilization or DNA double strand break repair in S. cerevisiae.
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Affiliation(s)
- Valentina Infantino
- Department of Cell Biology, University of Geneva, 30 Quai E. Ansermet, 1211, Geneva, Switzerland
| | - Françoise Stutz
- Department of Cell Biology, University of Geneva, 30 Quai E. Ansermet, 1211, Geneva, Switzerland.
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37
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Non-canonical DNA/RNA structures during Transcription-Coupled Double-Strand Break Repair: Roadblocks or Bona fide repair intermediates? DNA Repair (Amst) 2019; 81:102661. [PMID: 31331819 DOI: 10.1016/j.dnarep.2019.102661] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Although long overlooked, it is now well understood that DNA does not systematically assemble into a canonical double helix, known as B-DNA, throughout the entire genome but can also accommodate other structures including DNA hairpins, G-quadruplexes and RNA:DNA hybrids. Notably, these non-canonical DNA structures form preferentially at transcriptionally active loci. Acting as replication roadblocks and being targeted by multiple machineries, these structures weaken the genome and render it prone to damage, including DNA double-strand breaks (DSB). In addition, secondary structures also further accumulate upon DSB formation. Here we discuss the potential functions of pre-existing or de novo formed nucleic acid structures, as bona fide repair intermediates or repair roadblocks, especially during Transcription-Coupled DNA Double-Strand Break repair (TC-DSBR), and provide an update on the specialized protein complexes displaying the ability to remove these structures to safeguard genome integrity.
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38
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Goodman LD, Prudencio M, Kramer NJ, Martinez-Ramirez LF, Srinivasan AR, Lan M, Parisi MJ, Zhu Y, Chew J, Cook CN, Berson A, Gitler AD, Petrucelli L, Bonini NM. Toxic expanded GGGGCC repeat transcription is mediated by the PAF1 complex in C9orf72-associated FTD. Nat Neurosci 2019; 22:863-874. [PMID: 31110321 PMCID: PMC6535128 DOI: 10.1038/s41593-019-0396-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Accepted: 03/26/2019] [Indexed: 02/06/2023]
Abstract
An expanded GGGGCC hexanucleotide of more than 30 repeats (termed (G4C2)30+) within C9orf72 is the most prominent mutation in familial frontotemporal degeneration (FTD) and amyotrophic lateral sclerosis (ALS) (termed C9+). Through an unbiased large-scale screen of (G4C2)49-expressing Drosophila we identify the CDC73/PAF1 complex (PAF1C), a transcriptional regulator of RNA polymerase II, as a suppressor of G4C2-associated toxicity when knocked-down. Depletion of PAF1C reduces RNA and GR dipeptide production from (G4C2)30+ transgenes. Notably, in Drosophila, the PAF1C components Paf1 and Leo1 appear to be selective for the transcription of long, toxic repeat expansions, but not shorter, nontoxic expansions. In yeast, PAF1C components regulate the expression of both sense and antisense repeats. PAF1C is upregulated following (G4C2)30+ expression in flies and mice. In humans, PAF1 is also upregulated in C9+-derived cells, and its heterodimer partner, LEO1, binds C9+ repeat chromatin. In C9+ FTD, PAF1 and LEO1 are upregulated and their expression positively correlates with the expression of repeat-containing C9orf72 transcripts. These data indicate that PAF1C activity is an important factor for transcription of the long, toxic repeat in C9+ FTD.
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Affiliation(s)
- Lindsey D Goodman
- Neuroscience Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Nicholas J Kramer
- Neuroscience Graduate Program, Stanford University School of Medicine, Stanford, CA, USA
| | | | | | - Matthews Lan
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Michael J Parisi
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Yongqing Zhu
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Jeannie Chew
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
| | - Casey N Cook
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
| | - Amit Berson
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Aaron D Gitler
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | | | - Nancy M Bonini
- Neuroscience Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA.
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Myka KK, Gottesman ME. DksA and DNA double-strand break repair. Curr Genet 2019; 65:1297-1300. [PMID: 31076845 DOI: 10.1007/s00294-019-00983-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 04/24/2019] [Accepted: 04/25/2019] [Indexed: 12/19/2022]
Abstract
We use genetic assays to suggest that transcription-coupled repair or new origin formation in Escherichia coli involves removal of RNAP to create an RNA primer for DNA synthesis. Transcription factor DksA was shown to play a role in numerous reactions involving RNA polymerase. Some, but not all, of the activities of DksA at promoters or during transcription elongation require (p)ppGpp. In addition to its role during transcription, DksA is also involved in maintaining genome integrity. Cells lacking DksA are sensitive to multiple DNA damaging agents including UV light, ionizing radiation, mitomycin C, and nalidixic acid. Here, we focus on two recent studies addressing the importance of DksA in the repair of double-strand breaks (DSBs), one by Sivaramakrishnan et al. (Nature 550:214-218, 2017) and one originating in our laboratory, Myka et al. (Mol Microbiol 111:1382-1397. https://doi.org/10.1111/mmi.14227 , 2019). It appears that depending on the type and possibly location of DNA damage, DksA can play either a passive or an active role in DSB repair. The passive role relies on exclusion of anti-backtracking factors from the RNAP secondary channel. The exact mechanism of active DksA-mediated DNA repair is unknown. However, DksA was proposed to destabilize transcription complexes, thus clearing the way for recombination and DNA repair. Based on the requirement for DksA, both in repair of DSBs and the R-loop-dependent formation of new origins of DNA replication, we propose that DksA may allow for removal of RNAP without unwinding of the RNA:DNA hybrid, which can then be extended by a DNA polymerase. This mechanism obviates the need for RNAP backtracking to repair damaged DNA.
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Affiliation(s)
- Kamila K Myka
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA.,Molecular Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Max E Gottesman
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA.
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40
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Kaushal S, Freudenreich CH. The role of fork stalling and DNA structures in causing chromosome fragility. Genes Chromosomes Cancer 2019; 58:270-283. [PMID: 30536896 DOI: 10.1002/gcc.22721] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 11/13/2018] [Accepted: 12/03/2018] [Indexed: 12/19/2022] Open
Abstract
Alternative non-B form DNA structures, also called secondary structures, can form in certain DNA sequences under conditions that produce single-stranded DNA, such as during replication, transcription, and repair. Direct links between secondary structure formation, replication fork stalling, and genomic instability have been found for many repeated DNA sequences that cause disease when they expand. Common fragile sites (CFSs) are known to be AT-rich and break under replication stress, yet the molecular basis for their fragility is still being investigated. Over the past several years, new evidence has linked both the formation of secondary structures and transcription to fork stalling and fragility of CFSs. How these two events may synergize to cause fragility and the role of nuclease cleavage at secondary structures in rare and CFSs are discussed here. We also highlight evidence for a new hypothesis that secondary structures at CFSs not only initiate fragility but also inhibit healing, resulting in their characteristic appearance.
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Affiliation(s)
- Simran Kaushal
- Department of Biology, Tufts University, Medford, Massachusetts
| | - Catherine H Freudenreich
- Department of Biology, Tufts University, Medford, Massachusetts.,Program in Genetics, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, Massachusetts
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41
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Abstract
Exposure of genomic, single-stranded DNA (ssDNA) during transcription and replication creates opportunities for the formation of inappropriate secondary structures. Cells manage this exposure by using topoisomerases and helicases to reduce the inherent topological stress that arises from unwinding the double helix and by coating ssDNA with protective protein complexes. Interestingly, specific DNA-RNA hybrids, known as R-loops, form during transcription and exist in homeostasis throughout the genomes of prokaryotes and eukaryotes. These hybrids nucleate from guanine rich clusters in the template strand and extend across GC rich spans of transcribed genes. In vivo regulatory functions have evolved from R-loops, including regulation of gene expression and telomere lengthening. However, they also exist as a form of stress, particularly when replication forks collide with the transcription machinery. New methodologies and models are being developed to delineate the biology of R-loops, including those related to cell stress-based diseases like cancer. As accumulation of R-loops is associated with disease, targeting molecular pathways that regulate their formation or removal could provide new avenues for therapeutic intervention. This review covers recent understandings of the molecular basis for R-loop formation, removal, and biological outcomes in the context of cellular stress.
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Affiliation(s)
- David F Allison
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
| | - Gang Greg Wang
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
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42
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Abstract
BACKGROUND Numerous different types of variations can occur in DNA and have diverse effects and consequences. The Variation Ontology (VariO) was developed for systematic descriptions of variations and their effects at DNA, RNA and protein levels. RESULTS VariO use and terms for DNA variations are described in depth. VariO provides systematic names for variation types and detailed descriptions for changes in DNA function, structure and properties. The principles of VariO are presented along with examples from published articles or databases, most often in relation to human diseases. VariO terms describe local DNA changes, chromosome number and structure variants, chromatin alterations, as well as genomic changes, whether of genetic or non-genetic origin. CONCLUSIONS DNA variation systematics facilitates unambiguous descriptions of variations and their effects and further reuse and integration of data from different sources by both human and computers.
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Affiliation(s)
- Mauno Vihinen
- Department of Experimental Medical Science, Lund University, BMC B13, SE-22184, Lund, Sweden.
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43
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Voutsinos V, Munk SHN, Oestergaard VH. Common Chromosomal Fragile Sites-Conserved Failure Stories. Genes (Basel) 2018; 9:E580. [PMID: 30486458 PMCID: PMC6315858 DOI: 10.3390/genes9120580] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 11/19/2018] [Accepted: 11/21/2018] [Indexed: 12/17/2022] Open
Abstract
In order to pass on an intact copy of the genome during cell division, complete and faithful DNA replication is crucial. Yet, certain areas of the genome are intrinsically challenging to replicate, which manifests as high local mutation propensity. Such regions include trinucleotide repeat sequences, common chromosomal fragile sites (CFSs), and early replicating fragile sites (ERFSs). Despite their genomic instability CFSs are conserved, suggesting that they have a biological function. To shed light on the potential function of CFSs, this review summarizes the similarities and differences of the regions that challenge DNA replication with main focus on CFSs. Moreover, we review the mechanisms that operate when CFSs fail to complete replication before entry into mitosis. Finally, evolutionary perspectives and potential physiological roles of CFSs are discussed with emphasis on their potential role in neurogenesis.
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Affiliation(s)
- Vasileios Voutsinos
- Department of Biology, University of Copenhagen, 2200 Copenhagen N, Denmark.
| | - Sebastian H N Munk
- Department of Biology, University of Copenhagen, 2200 Copenhagen N, Denmark.
| | - Vibe H Oestergaard
- Department of Biology, University of Copenhagen, 2200 Copenhagen N, Denmark.
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44
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Belotserkovskii BP, Tornaletti S, D'Souza AD, Hanawalt PC. R-loop generation during transcription: Formation, processing and cellular outcomes. DNA Repair (Amst) 2018; 71:69-81. [PMID: 30190235 PMCID: PMC6340742 DOI: 10.1016/j.dnarep.2018.08.009] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
R-loops are structures consisting of an RNA-DNA duplex and an unpaired DNA strand. They can form during transcription upon nascent RNA "threadback" invasion into the DNA duplex to displace the non-template strand. Although R-loops occur naturally in all kingdoms of life and serve regulatory roles, they are often deleterious and can cause genomic instability. Of particular importance are the disastrous consequences when replication forks or transcription complexes collide with R-loops. The appropriate processing of R-loops is essential to avoid a number of human neurodegenerative and other clinical disorders. We provide a perspective on mechanistic aspects of R-loop formation and their resolution learned from studies in model systems. This should contribute to improved understanding of R-loop biological functions and enable their practical applications. We propose the novel employment of artificially-generated stable R-loops to selectively inactivate tumor cells.
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Affiliation(s)
- Boris P Belotserkovskii
- Department of Biology, Stanford University, 371 Serra Mall, Stanford, CA, 94305-5020, United States
| | - Silvia Tornaletti
- Department of Biology, Stanford University, 371 Serra Mall, Stanford, CA, 94305-5020, United States
| | - Alicia D D'Souza
- Department of Biology, Stanford University, 371 Serra Mall, Stanford, CA, 94305-5020, United States
| | - Philip C Hanawalt
- Department of Biology, Stanford University, 371 Serra Mall, Stanford, CA, 94305-5020, United States.
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45
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The etiology of uracil residues in the Saccharomyces cerevisiae genomic DNA. Curr Genet 2018; 65:393-399. [PMID: 30328489 PMCID: PMC6420880 DOI: 10.1007/s00294-018-0895-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 10/11/2018] [Accepted: 10/13/2018] [Indexed: 11/29/2022]
Abstract
Non-canonical residue in DNA is a major and conserved source of genome instability. The appearance of uracil residues in DNA accompanies a significant mutagenic consequence and is regulated at multiple levels, from the concentration of available dUTP in the nucleotide pool to the excision repair for removal from DNA. Recently, an interesting phenomenon of transcription-associated elevation in uracil-derived mutations was described in Saccharomyces cerevisiae genome. While trying to understand the variability in mutagenesis, we uncovered that the frequency of uracil incorporation into DNA can vary depending on the transcription rate and that the non-replicative, repair-associated DNA synthesis underlies the higher uracil density of the actively transcribed genomic loci. This novel mechanism brings together the chemical vulnerability of DNA under transcription and the uracil-associated mutagenesis, and has the potential to apply to other non-canonical residues of mutagenic importance.
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46
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Gorgoulis VG, Pefani D, Pateras IS, Trougakos IP. Integrating the DNA damage and protein stress responses during cancer development and treatment. J Pathol 2018; 246:12-40. [PMID: 29756349 PMCID: PMC6120562 DOI: 10.1002/path.5097] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Revised: 04/16/2018] [Accepted: 05/08/2018] [Indexed: 12/11/2022]
Abstract
During evolution, cells have developed a wide spectrum of stress response modules to ensure homeostasis. The genome and proteome damage response pathways constitute the pillars of this interwoven 'defensive' network. Consequently, the deregulation of these pathways correlates with ageing and various pathophysiological states, including cancer. In the present review, we highlight: (1) the structure of the genome and proteome damage response pathways; (2) their functional crosstalk; and (3) the conditions under which they predispose to cancer. Within this context, we emphasize the role of oncogene-induced DNA damage as a driving force that shapes the cellular landscape for the emergence of the various hallmarks of cancer. We also discuss potential means to exploit key cancer-related alterations of the genome and proteome damage response pathways in order to develop novel efficient therapeutic modalities. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.
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Affiliation(s)
- Vassilis G Gorgoulis
- Molecular Carcinogenesis Group, Department of Histology and Embryology, School of MedicineNational and Kapodistrian University of AthensAthensGreece
- Biomedical Research Foundation of the Academy of AthensAthensGreece
- Faculty of Biology, Medicine and HealthUniversity of Manchester, Manchester Academic Health Science CentreManchesterUK
| | - Dafni‐Eleftheria Pefani
- CRUK/MRC Institute for Radiation Oncology, Department of OncologyUniversity of OxfordOxfordUK
| | - Ioannis S Pateras
- Molecular Carcinogenesis Group, Department of Histology and Embryology, School of MedicineNational and Kapodistrian University of AthensAthensGreece
| | - Ioannis P Trougakos
- Department of Cell Biology and Biophysics, Faculty of BiologyNational and Kapodistrian University of AthensAthensGreece
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47
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Abstract
R loops are transient three-stranded nucleic acid structures that form physiologically during transcription when a nascent RNA transcript hybridizes with the DNA template strand, leaving a single strand of displaced nontemplate DNA. However, aberrant persistence of R-loops can cause DNA damage by inducing genomic instability. Indeed, evidence has emerged that R-loops might represent a key element in the pathogenesis of human diseases, including cancer, neurodegeneration, and motor neuron disorders. Mutations in genes directly involved in R-loop biology, such as SETX (senataxin), or unstable DNA expansion eliciting R-loop generation, such as C9ORF72 HRE, can cause DNA damage and ultimately result in motor neuron cell death. In this review, we discuss current advancements in this field with a specific focus on motor neuron diseases associated with deregulation of R-loop structures. These mechanisms can represent novel therapeutic targets for these devastating, incurable diseases.
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48
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Abstract
Mediator Complex Subunit 12 (MED12) is part of the transcriptional preinitiation machinery. Mutations of its gene predominantly occur in two types of highly frequent benign tumors, uterine leiomyomas and fibroadenomas of the breast, where they apparently act as driver mutations. Nevertheless, their presence is not restricted to benign tumors having been found at considerable frequencies in uterine leiomyosarcomas, malignant phyllodes tumors, and chronic lymphocytic leukemia also. Most of the mutations are located within exon 2 of the gene but in rare cases the intron 1/exon 2 boundary or exon 1 are affected. As to their type, predominantly single nucleotide exchanges with a hotspot in one codon are found, but small deletions clustering around that hotspot also are not uncommon. These latter deletions are leaving the open reading frame intact. As to the types of mutations, so far no apparent differences between the tumor entities affected have emerged. Interestingly, this pattern with small deletions clustered around the hotspot of single nucleotide exchanges resembles that seen as a result of targeted gene editing. In contrast to other driver mutations the percentage of
MED12-mutation positive tumors of independent clonal origin increases with the number of tumors per patient suggesting unknown etiological factors supporting site specific mutagenesis. These factors may act by inducing simultaneous site-specific double strand breaks the erroneous repair of which may lead to corresponding mutations. As inducers of DNA damage and its repair such as foreign nucleic acids of the microbiome displaying sequence homology to the putative target site might play a role. Interestingly, a 16 base pair homology of the hotspot to a putative terminator base-paired hairpin sequence of a Staphylococcus aureus tRNA gene cluster has been noted which might form R-loop like structures with its target sequence thus inducing said changes.
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Affiliation(s)
- Jörn Bullerdiek
- Institute of Medical Genetics, Medical Center, University of Rostock, Rostock, D-18057, Germany.,Human Genetics, University of Bremen, Bremen, D-28359 , Germany
| | - Birgit Rommel
- Human Genetics, University of Bremen, Bremen, D-28359 , Germany
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