1
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Vontalge EJ, Kavlashvili T, Dahmen SN, Cranford MT, Dewar JM. Control of DNA replication in vitro using a reversible replication barrier. Nat Protoc 2024:10.1038/s41596-024-00977-1. [PMID: 38594502 DOI: 10.1038/s41596-024-00977-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 01/19/2024] [Indexed: 04/11/2024]
Abstract
A major obstacle to studying DNA replication is that it involves asynchronous and highly delocalized events. A reversible replication barrier overcomes this limitation and allows replication fork movement to be synchronized and localized, facilitating the study of replication fork function and replication coupled repair. Here we provide details on establishing a reversible replication barrier in vitro and using it to monitor different aspects of DNA replication. DNA template containing an array of lac operator (lacO) sequences is first bound to purified lac repressor (LacR). This substrate is then replicated in vitro using a biochemical replication system, which results in replication forks stalled on either side of the LacR array regardless of when or where they arise. Once replication forks are synchronized at the barrier, isopropyl-β-D-thiogalactopyranoside can be added to disrupt LacR binding so that replication forks synchronously resume synthesis. We describe how this approach can be employed to control replication fork elongation, termination, stalling and uncoupling, as well as assays that can be used to monitor these processes. We also explain how this approach can be adapted to control whether replication forks encounter a DNA lesion on the leading or lagging strand template and whether a converging fork is present. The required reagents can be prepared in 1-2 weeks and experiments using this approach are typically performed over 1-3 d. The main requirements for utilizing the LacR replication barrier are basic biochemical expertise and access to an in vitro system to study DNA replication. Investigators should also be trained in working with radioactive materials.
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Affiliation(s)
- Emma J Vontalge
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Tamar Kavlashvili
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Steven N Dahmen
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Matthew T Cranford
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - James M Dewar
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA.
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2
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Wan L, He A, Li J, Guo P, Han D. High-Resolution NMR Structures of Intrastrand Hairpins Formed by CTG Trinucleotide Repeats. ACS Chem Neurosci 2024; 15:868-876. [PMID: 38319692 DOI: 10.1021/acschemneuro.3c00769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024] Open
Abstract
The CAG and CTG trinucleotide repeat expansions cause more than 10 human neurodegenerative diseases. Intrastrand hairpins formed by trinucleotide repeats contribute to repeat expansions, establishing them as potential drug targets. High-resolution structural determination of CAG and CTG hairpins poses as a long-standing goal to aid drug development, yet it has not been realized due to the intrinsic conformational flexibility of repetitive sequences. We herein investigate the solution structures of CTG hairpins using nuclear magnetic resonance (NMR) spectroscopy and found that four CTG repeats with a clamping G-C base pair was able to form a stable hairpin structure. We determine the first solution NMR structure of dG(CTG)4C hairpin and decipher a type I folding geometry of the TGCT tetraloop, wherein the two thymine residues form a T·T loop-closing base pair and the first three loop residues continuously stack. We further reveal that the CTG hairpin can be bound and stabilized by a small-molecule ligand, and the binding interferes with replication of a DNA template containing CTG repeats. Our determined high-resolution structures lay an important foundation for studying molecular interactions between native CTG hairpins and ligands, and benefit drug development for trinucleotide repeat expansion diseases.
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Affiliation(s)
- Liqi Wan
- Institute of Molecular Medicine (IMM), Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
- Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang 310022, China
| | - Axin He
- Institute of Molecular Medicine (IMM), Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
- Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang 310022, China
| | - Jinxing Li
- ReviR Therapeutics, Shenzhen Bay Hi-Tech Ecological Park, Nanshan District, Shenzhen, Guangdong 518067, China
| | - Pei Guo
- Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang 310022, China
| | - Da Han
- Institute of Molecular Medicine (IMM), Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China
- Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang 310022, China
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3
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Kumari D, Lokanga RA, McCann C, Ried T, Usdin K. The fragile X locus is prone to spontaneous DNA damage that is preferentially repaired by nonhomologous end-joining to preserve genome integrity. iScience 2024; 27:108814. [PMID: 38303711 PMCID: PMC10831274 DOI: 10.1016/j.isci.2024.108814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 10/26/2023] [Accepted: 01/02/2024] [Indexed: 02/03/2024] Open
Abstract
A long CGG-repeat tract in the FMR1 gene induces the epigenetic silencing that causes fragile X syndrome (FXS). Epigenetic changes include H4K20 trimethylation, a heterochromatic modification frequently implicated in transcriptional silencing. Here, we report that treatment with A-196, an inhibitor of SUV420H1/H2, the enzymes responsible for H4K20 di-/trimethylation, does not affect FMR1 transcription, but does result in increased chromosomal duplications. Increased duplications were also seen in FXS cells treated with SCR7, an inhibitor of Lig4, a ligase essential for NHEJ. Our study suggests that the fragile X (FX) locus is prone to spontaneous DNA damage that is normally repaired by NHEJ. We suggest that heterochromatinization of the FX allele may be triggered, at least in part, in response to this DNA damage.
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Affiliation(s)
- Daman Kumari
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Rachel Adihe Lokanga
- Section of Cancer Genomics, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Cai McCann
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Thomas Ried
- Section of Cancer Genomics, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Karen Usdin
- Section on Gene Structure and Disease, Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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4
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Zierhut C. DNA damage and chromosomal instability. Methods Cell Biol 2024; 182:xvii-xx. [PMID: 38359991 DOI: 10.1016/s0091-679x(24)00029-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2024]
Affiliation(s)
- Christian Zierhut
- Division of Cancer Biology, The Institute of Cancer Research, London, United Kingdom
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5
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Lewis JS, van Oijen AM, Spenkelink LM. Embracing Heterogeneity: Challenging the Paradigm of Replisomes as Deterministic Machines. Chem Rev 2023; 123:13419-13440. [PMID: 37971892 PMCID: PMC10790245 DOI: 10.1021/acs.chemrev.3c00436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Revised: 10/15/2023] [Accepted: 10/20/2023] [Indexed: 11/19/2023]
Abstract
The paradigm of cellular systems as deterministic machines has long guided our understanding of biology. Advancements in technology and methodology, however, have revealed a world of stochasticity, challenging the notion of determinism. Here, we explore the stochastic behavior of multi-protein complexes, using the DNA replication system (replisome) as a prime example. The faithful and timely copying of DNA depends on the simultaneous action of a large set of enzymes and scaffolding factors. This fundamental cellular process is underpinned by dynamic protein-nucleic acid assemblies that must transition between distinct conformations and compositional states. Traditionally viewed as a well-orchestrated molecular machine, recent experimental evidence has unveiled significant variability and heterogeneity in the replication process. In this review, we discuss recent advances in single-molecule approaches and single-particle cryo-EM, which have provided insights into the dynamic processes of DNA replication. We comment on the new challenges faced by structural biologists and biophysicists as they attempt to describe the dynamic cascade of events leading to replisome assembly, activation, and progression. The fundamental principles uncovered and yet to be discovered through the study of DNA replication will inform on similar operating principles for other multi-protein complexes.
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Affiliation(s)
- Jacob S. Lewis
- Macromolecular
Machines Laboratory, The Francis Crick Institute, London NW1 1AT, United Kingdom
| | - Antoine M. van Oijen
- Molecular
Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Lisanne M. Spenkelink
- Molecular
Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
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6
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Williams SL, Casas‐Delucchi CS, Raguseo F, Guneri D, Li Y, Minamino M, Fletcher EE, Yeeles JTP, Keyser UF, Waller ZAE, Di Antonio M, Coster G. Replication-induced DNA secondary structures drive fork uncoupling and breakage. EMBO J 2023; 42:e114334. [PMID: 37781931 PMCID: PMC10646557 DOI: 10.15252/embj.2023114334] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 09/20/2023] [Accepted: 09/21/2023] [Indexed: 10/03/2023] Open
Abstract
Sequences that form DNA secondary structures, such as G-quadruplexes (G4s) and intercalated-Motifs (iMs), are abundant in the human genome and play various physiological roles. However, they can also interfere with replication and threaten genome stability. Multiple lines of evidence suggest G4s inhibit replication, but the underlying mechanism remains unclear. Moreover, evidence of how iMs affect the replisome is lacking. Here, we reconstitute replication of physiologically derived structure-forming sequences to find that a single G4 or iM arrest DNA replication. Direct single-molecule structure detection within solid-state nanopores reveals structures form as a consequence of replication. Combined genetic and biophysical characterisation establishes that structure stability and probability of structure formation are key determinants of replisome arrest. Mechanistically, replication arrest is caused by impaired synthesis, resulting in helicase-polymerase uncoupling. Significantly, iMs also induce breakage of nascent DNA. Finally, stalled forks are only rescued by a specialised helicase, Pif1, but not Rrm3, Sgs1, Chl1 or Hrq1. Altogether, we provide a mechanism for quadruplex structure formation and resolution during replication and highlight G4s and iMs as endogenous sources of replication stress.
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Affiliation(s)
- Sophie L Williams
- Genome Replication Lab, Division of Cancer Biology, Institute of Cancer ResearchChester Beatty LaboratoriesLondonUK
| | - Corella S Casas‐Delucchi
- Genome Replication Lab, Division of Cancer Biology, Institute of Cancer ResearchChester Beatty LaboratoriesLondonUK
| | - Federica Raguseo
- Chemistry DepartmentImperial College London, MSRHLondonUK
- Institute of Chemical Biology, MSRHLondonUK
| | | | - Yunxuan Li
- Cavendish LaboratoryUniversity of CambridgeCambridgeUK
| | | | | | | | | | | | - Marco Di Antonio
- Chemistry DepartmentImperial College London, MSRHLondonUK
- Institute of Chemical Biology, MSRHLondonUK
- Francis Crick InstituteLondonUK
| | - Gideon Coster
- Genome Replication Lab, Division of Cancer Biology, Institute of Cancer ResearchChester Beatty LaboratoriesLondonUK
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7
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Sato K, Knipscheer P. G-quadruplex resolution: From molecular mechanisms to physiological relevance. DNA Repair (Amst) 2023; 130:103552. [PMID: 37572578 DOI: 10.1016/j.dnarep.2023.103552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 07/29/2023] [Accepted: 08/01/2023] [Indexed: 08/14/2023]
Abstract
Guanine-rich DNA sequences can fold into stable four-stranded structures called G-quadruplexes or G4s. Research in the past decade demonstrated that G4 structures are widespread in the genome and prevalent in regulatory regions of actively transcribed genes. The formation of G4s has been tightly linked to important biological processes including regulation of gene expression and genome maintenance. However, they can also pose a serious threat to genome integrity especially by impeding DNA replication, and G4-associated somatic mutations have been found accumulated in the cancer genomes. Specialised DNA helicases and single stranded DNA binding proteins that can resolve G4 structures play a crucial role in preventing genome instability. The large variety of G4 unfolding proteins suggest the presence of multiple G4 resolution mechanisms in cells. Recently, there has been considerable progress in our detailed understanding of how G4s are resolved, especially during DNA replication. In this review, we first discuss the current knowledge of the genomic G4 landscapes and the impact of G4 structures on DNA replication and genome integrity. We then describe the recent progress on the mechanisms that resolve G4 structures and their physiological relevance. Finally, we discuss therapeutic opportunities to target G4 structures.
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Affiliation(s)
- Koichi Sato
- Oncode Institute, Hubrecht Institute-KNAW & University Medical Center Utrecht, Utrecht, the Netherlands.
| | - Puck Knipscheer
- Oncode Institute, Hubrecht Institute-KNAW & University Medical Center Utrecht, Utrecht, the Netherlands; Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands.
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8
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Jones ML, Aria V, Baris Y, Yeeles JTP. How Pol α-primase is targeted to replisomes to prime eukaryotic DNA replication. Mol Cell 2023; 83:2911-2924.e16. [PMID: 37506699 PMCID: PMC10501992 DOI: 10.1016/j.molcel.2023.06.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 06/16/2023] [Accepted: 06/28/2023] [Indexed: 07/30/2023]
Abstract
During eukaryotic DNA replication, Pol α-primase generates primers at replication origins to start leading-strand synthesis and every few hundred nucleotides during discontinuous lagging-strand replication. How Pol α-primase is targeted to replication forks to prime DNA synthesis is not fully understood. Here, by determining cryoelectron microscopy (cryo-EM) structures of budding yeast and human replisomes containing Pol α-primase, we reveal a conserved mechanism for the coordination of priming by the replisome. Pol α-primase binds directly to the leading edge of the CMG (CDC45-MCM-GINS) replicative helicase via a complex interaction network. The non-catalytic PRIM2/Pri2 subunit forms two interfaces with CMG that are critical for in vitro DNA replication and yeast cell growth. These interactions position the primase catalytic subunit PRIM1/Pri1 directly above the exit channel for lagging-strand template single-stranded DNA (ssDNA), revealing why priming occurs efficiently only on the lagging-strand template and elucidating a mechanism for Pol α-primase to overcome competition from RPA to initiate primer synthesis.
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Affiliation(s)
- Morgan L Jones
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Valentina Aria
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Yasemin Baris
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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9
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Deiana M, Andrés Castán J, Josse P, Kahsay A, Sánchez D, Morice K, Gillet N, Ravindranath R, Patel A, Sengupta P, Obi I, Rodriguez-Marquez E, Khrouz L, Dumont E, Abad Galán L, Allain M, Walker B, Ahn HS, Maury O, Blanchard P, Le Bahers T, Öhlund D, von Hofsten J, Monnereau C, Cabanetos C, Sabouri N. A new G-quadruplex-specific photosensitizer inducing genome instability in cancer cells by triggering oxidative DNA damage and impeding replication fork progression. Nucleic Acids Res 2023; 51:6264-6285. [PMID: 37191066 PMCID: PMC10325911 DOI: 10.1093/nar/gkad365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 03/31/2023] [Accepted: 04/26/2023] [Indexed: 05/17/2023] Open
Abstract
Photodynamic therapy (PDT) ideally relies on the administration, selective accumulation and photoactivation of a photosensitizer (PS) into diseased tissues. In this context, we report a new heavy-atom-free fluorescent G-quadruplex (G4) DNA-binding PS, named DBI. We reveal by fluorescence microscopy that DBI preferentially localizes in intraluminal vesicles (ILVs), precursors of exosomes, which are key components of cancer cell proliferation. Moreover, purified exosomal DNA was recognized by a G4-specific antibody, thus highlighting the presence of such G4-forming sequences in the vesicles. Despite the absence of fluorescence signal from DBI in nuclei, light-irradiated DBI-treated cells generated reactive oxygen species (ROS), triggering a 3-fold increase of nuclear G4 foci, slowing fork progression and elevated levels of both DNA base damage, 8-oxoguanine, and double-stranded DNA breaks. Consequently, DBI was found to exert significant phototoxic effects (at nanomolar scale) toward cancer cell lines and tumor organoids. Furthermore, in vivo testing reveals that photoactivation of DBI induces not only G4 formation and DNA damage but also apoptosis in zebrafish, specifically in the area where DBI had accumulated. Collectively, this approach shows significant promise for image-guided PDT.
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Affiliation(s)
- Marco Deiana
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87, Umeå, Sweden
| | | | - Pierre Josse
- Univ Angers, CNRS, MOLTECH-ANJOU, SFR MATRIX, F-49000 Angers, France
| | - Abraha Kahsay
- Department of Integrative Medical Biology, Umeå University, SE-901 87, Umeå, Sweden
| | | | - Korentin Morice
- Univ Angers, CNRS, MOLTECH-ANJOU, SFR MATRIX, F-49000 Angers, France
| | - Natacha Gillet
- ENS de Lyon, CNRS, Université Claude Bernard Lyon 1, Laboratoire de Chimie UMR 5182, F-69342 Lyon, France
| | - Ranjitha Ravindranath
- ENS de Lyon, CNRS, Université Claude Bernard Lyon 1, Laboratoire de Chimie UMR 5182, F-69342 Lyon, France
- Indian Institute for Science Education and Research (IISER), Tirupati-517507, India
| | - Ankit Kumar Patel
- Department of Radiation Sciences/Oncology, Umeå University, SE-901 87, Umeå, Sweden
- Wallenberg Centre for Molecular Medicine (WCMM), Umeå University, SE-901 87, Umeå, Sweden
| | - Pallabi Sengupta
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87, Umeå, Sweden
| | - Ikenna Obi
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87, Umeå, Sweden
| | | | - Lhoussain Khrouz
- ENS de Lyon, CNRS, Université Claude Bernard Lyon 1, Laboratoire de Chimie UMR 5182, F-69342 Lyon, France
| | - Elise Dumont
- ENS de Lyon, CNRS, Université Claude Bernard Lyon 1, Laboratoire de Chimie UMR 5182, F-69342 Lyon, France
- Institut Universitaire de France, 5 rue Descartes, 75005 Paris, France
| | - Laura Abad Galán
- ENS de Lyon, CNRS, Université Claude Bernard Lyon 1, Laboratoire de Chimie UMR 5182, F-69342 Lyon, France
| | - Magali Allain
- Univ Angers, CNRS, MOLTECH-ANJOU, SFR MATRIX, F-49000 Angers, France
| | - Bright Walker
- Department of Chemistry, Kyung Hee University, Seoul, 02447, South Korea
| | - Hyun Seo Ahn
- Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, South Korea
| | - Olivier Maury
- ENS de Lyon, CNRS, Université Claude Bernard Lyon 1, Laboratoire de Chimie UMR 5182, F-69342 Lyon, France
| | | | - Tangui Le Bahers
- ENS de Lyon, CNRS, Université Claude Bernard Lyon 1, Laboratoire de Chimie UMR 5182, F-69342 Lyon, France
- Institut Universitaire de France, 5 rue Descartes, 75005 Paris, France
| | - Daniel Öhlund
- Department of Radiation Sciences/Oncology, Umeå University, SE-901 87, Umeå, Sweden
- Wallenberg Centre for Molecular Medicine (WCMM), Umeå University, SE-901 87, Umeå, Sweden
| | - Jonas von Hofsten
- Department of Integrative Medical Biology, Umeå University, SE-901 87, Umeå, Sweden
| | - Cyrille Monnereau
- ENS de Lyon, CNRS, Université Claude Bernard Lyon 1, Laboratoire de Chimie UMR 5182, F-69342 Lyon, France
| | - Clément Cabanetos
- Univ Angers, CNRS, MOLTECH-ANJOU, SFR MATRIX, F-49000 Angers, France
- Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, South Korea
- Building Blocks for FUture Electronics Laboratory (2BFUEL), IRL CNRS 2002, Yonsei University, Seoul, South Korea
| | - Nasim Sabouri
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87, Umeå, Sweden
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10
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Williams SL, Coster G. Cloning and expansion of repetitive DNA sequences. Methods Cell Biol 2022; 182:167-185. [PMID: 38359975 DOI: 10.1016/bs.mcb.2022.10.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Repeat and structure-prone DNA sequences comprise a large proportion of the human genome. The instability of these sequences has been implicated in a range of diseases, including cancers and neurodegenerative disorders. However, the mechanism of pathogenicity is poorly understood. As such, further studies on repetitive DNA are required. Cloning and maintaining repeat-containing substrates is challenging due to their inherent ability to form non-B DNA secondary structures which are refractory to DNA polymerases and prone to undergo rearrangements. Here, we describe an approach to clone and expand tandem-repeat DNA without interruptions, thereby allowing for its manipulation and subsequent investigation.
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Affiliation(s)
- Sophie L Williams
- Genome Replication lab, Division of Cancer Biology, Institute of Cancer Research, Chester Beatty Laboratories, London, United Kingdom
| | - Gideon Coster
- Genome Replication lab, Division of Cancer Biology, Institute of Cancer Research, Chester Beatty Laboratories, London, United Kingdom.
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11
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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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