1
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Kojak N, Kuno J, Fittipaldi KE, Khan A, Wenger D, Glasser M, Donnianni RA, Tang Y, Zhang J, Huling K, Ally R, Mujica AO, Turner T, Magardino G, Huang PY, Kerk SY, Droguett G, Prissette M, Rojas J, Gomez T, Gagliardi A, Hunt C, Rabinowitz JS, Gong G, Poueymirou W, Chiao E, Zambrowicz B, Siao CJ, Kajimura D. Somatic and intergenerational G4C2 hexanucleotide repeat instability in a human C9orf72 knock-in mouse model. Nucleic Acids Res 2024; 52:5732-5755. [PMID: 38597682 PMCID: PMC11162798 DOI: 10.1093/nar/gkae250] [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: 06/12/2023] [Revised: 03/19/2024] [Accepted: 03/28/2024] [Indexed: 04/11/2024] Open
Abstract
Expansion of a G4C2 repeat in the C9orf72 gene is associated with familial Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD). To investigate the underlying mechanisms of repeat instability, which occurs both somatically and intergenerationally, we created a novel mouse model of familial ALS/FTD that harbors 96 copies of G4C2 repeats at a humanized C9orf72 locus. In mouse embryonic stem cells, we observed two modes of repeat expansion. First, we noted minor increases in repeat length per expansion event, which was dependent on a mismatch repair pathway protein Msh2. Second, we found major increases in repeat length per event when a DNA double- or single-strand break (DSB/SSB) was artificially introduced proximal to the repeats, and which was dependent on the homology-directed repair (HDR) pathway. In mice, the first mode primarily drove somatic repeat expansion. Major changes in repeat length, including expansion, were observed when SSB was introduced in one-cell embryos, or intergenerationally without DSB/SSB introduction if G4C2 repeats exceeded 400 copies, although spontaneous HDR-mediated expansion has yet to be identified. These findings provide a novel strategy to model repeat expansion in a non-human genome and offer insights into the mechanism behind C9orf72 G4C2 repeat instability.
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Affiliation(s)
- Nada Kojak
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | - Junko Kuno
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | | | - David Wenger
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | | | - Yajun Tang
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | - Jade Zhang
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | - Katie Huling
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | - Roxanne Ally
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | | | | | - Pei Yi Huang
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | - Sze Yen Kerk
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | | | - Jose Rojas
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | | | | | | | - Guochun Gong
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
| | | | - Eric Chiao
- Regeneron Pharmaceuticals, Tarrytown, NY 10591, USA
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2
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Zhang Y, Liu X, Li Z, Li H, Miao Z, Wan B, Xu X. Advances on the Mechanisms and Therapeutic Strategies in Non-coding CGG Repeat Expansion Diseases. Mol Neurobiol 2024:10.1007/s12035-024-04239-9. [PMID: 38780719 DOI: 10.1007/s12035-024-04239-9] [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: 11/20/2023] [Accepted: 05/02/2024] [Indexed: 05/25/2024]
Abstract
Non-coding CGG repeat expansions within the 5' untranslated region are implicated in a range of neurological disorders, including fragile X-associated tremor/ataxia syndrome, oculopharyngeal myopathy with leukodystrophy, and oculopharyngodistal myopathy. This review outlined the general characteristics of diseases associated with non-coding CGG repeat expansions, detailing their clinical manifestations and neuroimaging patterns, which often overlap and indicate shared pathophysiological traits. We summarized the underlying molecular mechanisms of these disorders, providing new insights into the roles that DNA, RNA, and toxic proteins play. Understanding these mechanisms is crucial for the development of targeted therapeutic strategies. These strategies include a range of approaches, such as antisense oligonucleotides, RNA interference, genomic DNA editing, small molecule interventions, and other treatments aimed at correcting the dysregulated processes inherent in these disorders. A deeper understanding of the shared mechanisms among non-coding CGG repeat expansion disorders may hold the potential to catalyze the development of innovative therapies, ultimately offering relief to individuals grappling with these debilitating neurological conditions.
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Affiliation(s)
- Yutong Zhang
- Departments of Neurology, The First Affiliated Hospital of Soochow University, Suzhou City, China
| | - Xuan Liu
- Departments of Neurology, The First Affiliated Hospital of Soochow University, Suzhou City, China
| | - Zeheng Li
- Departments of Neurology, The First Affiliated Hospital of Soochow University, Suzhou City, China
| | - Hao Li
- Departments of Neurology, The First Affiliated Hospital of Soochow University, Suzhou City, China
- Department of Neurology, The Fourth Affiliated Hospital of Soochow University, Suzhou, 215124, China
| | - Zhigang Miao
- The Institute of Neuroscience, Soochow University, Suzhou City, China
| | - Bo Wan
- The Institute of Neuroscience, Soochow University, Suzhou City, China
| | - Xingshun Xu
- Departments of Neurology, The First Affiliated Hospital of Soochow University, Suzhou City, China.
- The Institute of Neuroscience, Soochow University, Suzhou City, China.
- Department of Neurology, The First Affiliated Hospital of Soochow University, Suzhou, 215000, China.
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3
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Reed JM, Wolfe BE, Romero LM. Is resilience a unifying concept for the biological sciences? iScience 2024; 27:109478. [PMID: 38660410 PMCID: PMC11039332 DOI: 10.1016/j.isci.2024.109478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024] Open
Abstract
There is increasing interest in applying resilience concepts at different scales of biological organization to address major interdisciplinary challenges from cancer to climate change. It is unclear, however, whether resilience can be a unifying concept consistently applied across the breadth of the biological sciences, or whether there is limited capacity for integration. In this review, we draw on literature from molecular biology to community ecology to ascertain commonalities and shortcomings in how resilience is measured and interpreted. Resilience is studied at all levels of biological organization, although the term is often not used. There is a suite of resilience mechanisms conserved across biological scales, and there are tradeoffs that affect resilience. Resilience is conceptually useful to help diverse researchers think about how biological systems respond to perturbations, but we need a richer lexicon to describe the diversity of perturbations, and we lack widely applicable metrics of resilience.
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Affiliation(s)
- J. Michael Reed
- Department of Biology, Tufts University, Medford 02155, MA, USA
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4
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Hu Y, Chen W, Wei C, Jiang S, Li S, Wang X, Xu R. Pathological mechanisms of amyotrophic lateral Sclerosis. Neural Regen Res 2024; 19:1036-1044. [PMID: 37862206 PMCID: PMC10749610 DOI: 10.4103/1673-5374.382985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Revised: 05/12/2023] [Accepted: 07/06/2023] [Indexed: 10/22/2023] Open
Abstract
Amyotrophic lateral sclerosis refers to a neurodegenerative disease involving the motor system, the cause of which remains unexplained despite several years of research. Thus, the journey to understanding or treating amyotrophic lateral sclerosis is still a long one. According to current research, amyotrophic lateral sclerosis is likely not due to a single factor but rather to a combination of mechanisms mediated by complex interactions between molecular and genetic pathways. The progression of the disease involves multiple cellular processes and the interaction between different complex mechanisms makes it difficult to identify the causative factors of amyotrophic lateral sclerosis. Here, we review the most common amyotrophic lateral sclerosis-associated pathogenic genes and the pathways involved in amyotrophic lateral sclerosis, as well as summarize currently proposed potential mechanisms responsible for amyotrophic lateral sclerosis disease and their evidence for involvement in amyotrophic lateral sclerosis. In addition, we discuss current emerging strategies for the treatment of amyotrophic lateral sclerosis. Studying the emergence of these new therapies may help to further our understanding of the pathogenic mechanisms of the disease.
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Affiliation(s)
- Yushu Hu
- Department of Clinical Medicine, Nanchang University, Nanchang, Jiangxi Province, China
- Department of Neurology, Jiangxi Provincial People’s Hospital, Nanchang, Jiangxi Province, China
| | - Wenzhi Chen
- Department of Clinical Medicine, Nanchang University, Nanchang, Jiangxi Province, China
- Department of Neurology, Jiangxi Provincial People’s Hospital, Nanchang, Jiangxi Province, China
| | - Caihui Wei
- Department of Clinical Medicine, Nanchang University, Nanchang, Jiangxi Province, China
- Department of Neurology, Jiangxi Provincial People’s Hospital, Nanchang, Jiangxi Province, China
| | - Shishi Jiang
- Department of Clinical Medicine, Nanchang University, Nanchang, Jiangxi Province, China
- Department of Neurology, Jiangxi Provincial People’s Hospital, Nanchang, Jiangxi Province, China
| | - Shu Li
- Department of Clinical Medicine, Nanchang University, Nanchang, Jiangxi Province, China
- Department of Neurology, Jiangxi Provincial People’s Hospital, Nanchang, Jiangxi Province, China
| | - Xinxin Wang
- Department of Clinical Medicine, Nanchang University, Nanchang, Jiangxi Province, China
- Department of Neurology, Jiangxi Provincial People’s Hospital, Nanchang, Jiangxi Province, China
| | - Renshi Xu
- Department of Clinical Medicine, Nanchang University, Nanchang, Jiangxi Province, China
- Department of Neurology, Jiangxi Provincial People’s Hospital, Nanchang, Jiangxi Province, China
- Department of Neurology, The First Affiliated Hospital of Nanchang Medical College; The Clinical College of Nanchang Medical College, Nanchang, Jiangxi Province, China
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5
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Lee KH, Kim J, Kim JH. 3D epigenomics and 3D epigenopathies. BMB Rep 2024; 57:216-231. [PMID: 38627948 PMCID: PMC11139681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 01/15/2024] [Accepted: 03/18/2024] [Indexed: 05/25/2024] Open
Abstract
Mammalian genomes are intricately compacted to form sophisticated 3-dimensional structures within the tiny nucleus, so called 3D genome folding. Despite their shapes reminiscent of an entangled yarn, the rapid development of molecular and next-generation sequencing technologies (NGS) has revealed that mammalian genomes are highly organized in a hierarchical order that delicately affects transcription activities. An increasing amount of evidence suggests that 3D genome folding is implicated in diseases, giving us a clue on how to identify novel therapeutic approaches. In this review, we will study what 3D genome folding means in epigenetics, what types of 3D genome structures there are, how they are formed, and how the technologies have developed to explore them. We will also discuss the pathological implications of 3D genome folding. Finally, we will discuss how to leverage 3D genome folding and engineering for future studies. [BMB Reports 2024; 57(5): 216-231].
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Affiliation(s)
- Kyung-Hwan Lee
- Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Jungyu Kim
- Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Ji Hun Kim
- Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
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6
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Papp D, Hernandez LA, Mai TA, Haanen TJ, O’Donnell MA, Duran AT, Hernandez SM, Narvanto JE, Arguello B, Onwukwe MO, Mirkin SM, Kim JC. Massive contractions of myotonic dystrophy type 2-associated CCTG tetranucleotide repeats occur via double-strand break repair with distinct requirements for DNA helicases. G3 (BETHESDA, MD.) 2024; 14:jkad257. [PMID: 37950892 PMCID: PMC10849350 DOI: 10.1093/g3journal/jkad257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 07/06/2023] [Accepted: 10/19/2023] [Indexed: 11/13/2023]
Abstract
Myotonic dystrophy type 2 (DM2) is a genetic disease caused by expanded CCTG DNA repeats in the first intron of CNBP. The number of CCTG repeats in DM2 patients ranges from 75 to 11,000, yet little is known about the molecular mechanisms responsible for repeat expansions or contractions. We developed an experimental system in Saccharomyces cerevisiae that enables the selection of large-scale contractions of (CCTG)100 within the intron of a reporter gene and subsequent genetic analysis. Contractions exceeded 80 repeat units, causing the final repetitive tract to be well below the threshold for disease. We found that Rad51 and Rad52 are involved in these massive contractions, indicating a mechanism that uses homologous recombination. Srs2 helicase was shown previously to stabilize CTG, CAG, and CGG repeats. Loss of Srs2 did not significantly affect CCTG contraction rates in unperturbed conditions. In contrast, loss of the RecQ helicase Sgs1 resulted in a 6-fold decrease in contraction rate with specific evidence that helicase activity is required for large-scale contractions. Using a genetic assay to evaluate chromosome arm loss, we determined that CCTG and reverse complementary CAGG repeats elevate the rate of chromosomal fragility compared to a short-track control. Overall, our results demonstrate that the genetic control of CCTG repeat contractions is notably distinct among disease-causing microsatellite repeat sequences.
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Affiliation(s)
- David Papp
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078, USA
| | - Luis A Hernandez
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078, USA
| | - Theresa A Mai
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078, USA
| | - Terrance J Haanen
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078, USA
| | - Meghan A O’Donnell
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078, USA
| | - Ariel T Duran
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078, USA
| | - Sophia M Hernandez
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078, USA
| | - Jenni E Narvanto
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078, USA
| | - Berenice Arguello
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078, USA
| | - Marvin O Onwukwe
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078, USA
| | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Jane C Kim
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078, USA
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7
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Medina-Rivera M, Phelps S, Sridharan M, Becker J, Lamb N, Kumar C, Sutton M, Bielinsky A, Balakrishnan L, Surtees J. Elevated MSH2 MSH3 expression interferes with DNA metabolism in vivo. Nucleic Acids Res 2023; 51:12185-12206. [PMID: 37930834 PMCID: PMC10711559 DOI: 10.1093/nar/gkad934] [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: 08/01/2023] [Revised: 09/30/2023] [Accepted: 10/10/2023] [Indexed: 11/08/2023] Open
Abstract
The Msh2-Msh3 mismatch repair (MMR) complex in Saccharomyces cerevisiae recognizes and directs repair of insertion/deletion loops (IDLs) up to ∼17 nucleotides. Msh2-Msh3 also recognizes and binds distinct looped and branched DNA structures with varying affinities, thereby contributing to genome stability outside post-replicative MMR through homologous recombination, double-strand break repair (DSBR) and the DNA damage response. In contrast, Msh2-Msh3 promotes genome instability through trinucleotide repeat (TNR) expansions, presumably by binding structures that form from single-stranded (ss) TNR sequences. We previously demonstrated that Msh2-Msh3 binding to 5' ssDNA flap structures interfered with Rad27 (Fen1 in humans)-mediated Okazaki fragment maturation (OFM) in vitro. Here we demonstrate that elevated Msh2-Msh3 levels interfere with DNA replication and base excision repair in vivo. Elevated Msh2-Msh3 also induced a cell cycle arrest that was dependent on RAD9 and ELG1 and led to PCNA modification. These phenotypes also required Msh2-Msh3 ATPase activity and downstream MMR proteins, indicating an active mechanism that is not simply a result of Msh2-Msh3 DNA-binding activity. This study provides new mechanistic details regarding how excess Msh2-Msh3 can disrupt DNA replication and repair and highlights the role of Msh2-Msh3 protein abundance in Msh2-Msh3-mediated genomic instability.
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Affiliation(s)
- Melisa Medina-Rivera
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Samantha Phelps
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Madhumita Sridharan
- Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN, 46202, USA
| | - Jordan Becker
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Natalie A Lamb
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Charanya Kumar
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Mark D Sutton
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Anja Bielinsky
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Lata Balakrishnan
- Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN, 46202, USA
| | - Jennifer A Surtees
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
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8
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Stormo BM, McLaughlin GA, Frederick LK, Jalihal AP, Cole SJ, Seim I, Dietrich FS, Gladfelter AS. Biomolecular condensates in fungi are tuned to function at specific temperatures. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.27.568884. [PMID: 38076832 PMCID: PMC10705276 DOI: 10.1101/2023.11.27.568884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/24/2023]
Abstract
Temperature can impact every reaction and molecular interaction essential to a cell. For organisms that cannot regulate their own temperature, a major challenge is how to adapt to temperatures that fluctuate unpredictability and on variable timescales. Biomolecular condensation offers a possible mechanism for encoding temperature-responsiveness and robustness into cell biochemistry and organization. To explore this idea, we examined temperature adaptation in a filamentous-growing fungus called Ashbya gossypii that engages biomolecular condensates containing the RNA-binding protein Whi3 to regulate mitosis and morphogenesis. We collected wild isolates of Ashbya that originate in different climates and found that mitotic asynchrony and polarized growth, which are known to be controlled by the condensation of Whi3, are temperature sensitive. Sequence analysis in the wild strains revealed changes to specific domains within Whi3 known to be important in condensate formation. Using an in vitro condensate reconstitution assay we found that temperature impacts the relative abundance of protein to RNA within condensates and that this directly impacts the material properties of the droplets. Finally, we found that exchanging Whi3 genes between warm and cold isolates was sufficient to rescue some, but not all, condensate-related phenotypes. Together these data demonstrate that material properties of Whi3 condensates are temperature sensitive, that these properties are important for function, and that sequence optimizes properties for a given climate.
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Affiliation(s)
| | - Grace A. McLaughlin
- Duke University, Department of Cell Biology, Durham, NC
- University of North Carolina, Chapel Hill, Department of Biology
| | | | | | - Sierra J Cole
- Duke University, Department of Cell Biology, Durham, NC
- University of North Carolina, Chapel Hill, Department of Biochemistry and Biophysics
| | - Ian Seim
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Fred S. Dietrich
- Duke University, Department of Molecular Genetics and Microbiology, Durham, NC
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9
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Rastokina A, Cebrián J, Mozafari N, Mandel NH, Smith CI, Lopes M, Zain R, Mirkin S. Large-scale expansions of Friedreich's ataxia GAA•TTC repeats in an experimental human system: role of DNA replication and prevention by LNA-DNA oligonucleotides and PNA oligomers. Nucleic Acids Res 2023; 51:8532-8549. [PMID: 37216608 PMCID: PMC10484681 DOI: 10.1093/nar/gkad441] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 05/02/2023] [Accepted: 05/20/2023] [Indexed: 05/24/2023] Open
Abstract
Friedreich's ataxia (FRDA) is caused by expansions of GAA•TTC repeats in the first intron of the human FXN gene that occur during both intergenerational transmissions and in somatic cells. Here we describe an experimental system to analyze large-scale repeat expansions in cultured human cells. It employs a shuttle plasmid that can replicate from the SV40 origin in human cells or be stably maintained in S. cerevisiae utilizing ARS4-CEN6. It also contains a selectable cassette allowing us to detect repeat expansions that accumulated in human cells upon plasmid transformation into yeast. We indeed observed massive expansions of GAA•TTC repeats, making it the first genetically tractable experimental system to study large-scale repeat expansions in human cells. Further, GAA•TTC repeats stall replication fork progression, while the frequency of repeat expansions appears to depend on proteins implicated in replication fork stalling, reversal, and restart. Locked nucleic acid (LNA)-DNA mixmer oligonucleotides and peptide nucleic acid (PNA) oligomers, which interfere with triplex formation at GAA•TTC repeats in vitro, prevented the expansion of these repeats in human cells. We hypothesize, therefore, that triplex formation by GAA•TTC repeats stall replication fork progression, ultimately leading to repeat expansions during replication fork restart.
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Affiliation(s)
| | - Jorge Cebrián
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Negin Mozafari
- Department of Laboratory Medicine, Translational Research Center Karolinska (TRACK), Karolinska Institutet, Karolinska University Hospital, SE-171 77 Stockholm, Sweden
| | | | - C I Edvard Smith
- Department of Laboratory Medicine, Translational Research Center Karolinska (TRACK), Karolinska Institutet, Karolinska University Hospital, SE-171 77 Stockholm, Sweden
| | - Massimo Lopes
- Institute of Molecular Cancer Research, University of Zurich, Zurich 8057, Switzerland
| | - Rula Zain
- Department of Laboratory Medicine, Translational Research Center Karolinska (TRACK), Karolinska Institutet, Karolinska University Hospital, SE-171 77 Stockholm, Sweden
- Center for Rare Diseases, Karolinska University Hospital, SE-17176 Stockholm, Sweden
| | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, MA 02155, USA
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10
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Papp D, Hernandez LA, Mai TA, Haanen TJ, O’Donnell MA, Duran AT, Hernandez SM, Narvanto JE, Arguello B, Onwukwe MO, Kolar K, Mirkin SM, Kim JC. Massive contractions of Myotonic Dystrophy Type 2-associated CCTG tetranucleotide repeats occur via double strand break repair with distinct requirements for helicases. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.06.548036. [PMID: 37461657 PMCID: PMC10350092 DOI: 10.1101/2023.07.06.548036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/22/2023]
Abstract
Myotonic Dystrophy Type 2 (DM2) is a genetic disease caused by expanded CCTG DNA repeats in the first intron of CNBP. The number of CCTG repeats in DM2 patients ranges from 75-11,000, yet little is known about the molecular mechanisms responsible for repeat expansions or contractions. We developed an experimental system in Saccharomyces cerevisiae that enables selection of large-scale contractions of (CCTG)100 within the intron of a reporter gene and subsequent genetic analysis. Contractions exceeded 80 repeat units, causing the final repetitive tract to be well below the threshold for disease. We found that Rad51 and Rad52 are required for these massive contractions, indicating a mechanism that involves homologous recombination. Srs2 helicase was shown previously to stabilize CTG, CAG, and CGG repeats. Loss of Srs2 did not significantly affect CCTG contraction rates in unperturbed conditions. In contrast, loss of the RecQ helicase Sgs1 resulted in a 6-fold decrease in contraction rate with specific evidence that helicase activity is required for large-scale contractions. Using a genetic assay to evaluate chromosome arm loss, we determined that CCTG and reverse complementary CAGG repeats elevate the rate of chromosomal fragility compared to a low-repeat control. Overall, our results demonstrate that the genetic control of CCTG repeat contractions is notably distinct among disease-causing microsatellite repeat sequences.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Kara Kolar
- Department of Biology, Tufts University, Medford, MA 02155
| | | | - Jane C. Kim
- Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92078
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11
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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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12
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Xu P, Zhang J, Pan F, Mahn C, Roland C, Sagui C, Weninger K. Frustration Between Preferred States of Complementary Trinucleotide Repeat DNA Hairpins Anticorrelates with Expansion Disease Propensity. J Mol Biol 2023; 435:168086. [PMID: 37024008 PMCID: PMC10191799 DOI: 10.1016/j.jmb.2023.168086] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 03/21/2023] [Accepted: 03/30/2023] [Indexed: 04/08/2023]
Abstract
DNA trinucleotide repeat (TRs) expansion beyond a threshold often results in human neurodegenerative diseases. The mechanisms causing expansions remain unknown, although the tendency of TR ssDNA to self-associate into hairpins that slip along their length is widely presumed related. Here we apply single molecule FRET (smFRET) experiments and molecular dynamics simulations to determine conformational stabilities and slipping dynamics for CAG, CTG, GAC and GTC hairpins. Tetraloops are favored in CAG (89%), CTG (89%) and GTC (69%) while GAC favors triloops. We also determined that TTG interrupts near the loop in the CTG hairpin stabilize the hairpin against slipping. The different loop stabilities have implications for intermediate structures that may form when TR-containing duplex DNA opens. Opposing hairpins in the (CAG) ∙ (CTG) duplex would have matched stability whereas opposing hairpins in a (GAC) ∙ (GTC) duplex would have unmatched stability, introducing frustration in the (GAC) ∙ (GTC) opposing hairpins that could encourage their resolution to duplex DNA more rapidly than in (CAG) ∙ (CTG) structures. Given that the CAG and CTG TR can undergo large, disease-related expansion whereas the GAC and GTC sequences do not, these stability differences can inform and constrain models of expansion mechanisms of TR regions.
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Affiliation(s)
- Pengning Xu
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA. https://twitter.com/@XPengning
| | - Jiahui Zhang
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
| | - Feng Pan
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
| | - Chelsea Mahn
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
| | - Christopher Roland
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
| | - Celeste Sagui
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA.
| | - Keith Weninger
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA.
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13
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Maksimov MO, Wu C, Ashbrook DG, Villani F, Colonna V, Mousavi N, Ma N, Lu L, Pritchard JK, Goren A, Williams RW, Palmer AA, Gymrek M. A novel quantitative trait locus implicates Msh3 in the propensity for genome-wide short tandem repeat expansions in mice. Genome Res 2023; 33:689-702. [PMID: 37127331 PMCID: PMC10317118 DOI: 10.1101/gr.277576.122] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 04/26/2023] [Indexed: 05/03/2023]
Abstract
Short tandem repeats (STRs) are a class of rapidly mutating genetic elements typically characterized by repeated units of 1-6 bp. We leveraged whole-genome sequencing data for 152 recombinant inbred (RI) strains from the BXD family of mice to map loci that modulate genome-wide patterns of new mutations arising during parent-to-offspring transmission at STRs. We defined quantitative phenotypes describing the numbers and types of germline STR mutations in each strain and performed quantitative trait locus (QTL) analyses for each of these phenotypes. We identified a locus on Chromosome 13 at which strains inheriting the C57BL/6J (B) haplotype have a higher rate of STR expansions than those inheriting the DBA/2J (D) haplotype. The strongest candidate gene in this locus is Msh3, a known modifier of STR stability in cancer and at pathogenic repeat expansions in mice and humans, as well as a current drug target against Huntington's disease. The D haplotype at this locus harbors a cluster of variants near the 5' end of Msh3, including multiple missense variants near the DNA mismatch recognition domain. In contrast, the B haplotype contains a unique retrotransposon insertion. The rate of expansion covaries positively with Msh3 expression-with higher expression from the B haplotype. Finally, detailed analysis of mutation patterns showed that strains carrying the B allele have higher expansion rates, but slightly lower overall total mutation rates, compared with those with the D allele, particularly at tetranucleotide repeats. Our results suggest an important role for inherited variants in Msh3 in modulating genome-wide patterns of germline mutations at STRs.
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Affiliation(s)
- Mikhail O Maksimov
- Department of Medicine, University of California San Diego, La Jolla, California 92093, USA
- Department of Computer Science and Engineering, University of California San Diego, La Jolla, California 92093, USA
| | - Cynthia Wu
- Bioinformatics and Systems Biology Program, University of California San Diego, La Jolla, California 92093, USA
| | - David G Ashbrook
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
| | - Flavia Villani
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
| | - Vincenza Colonna
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
- Institute of Genetics and Biophysics, National Research Council, Naples 80111, Italy
| | - Nima Mousavi
- Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, California 92093, USA
| | - Nichole Ma
- Department of Medicine, University of California San Diego, La Jolla, California 92093, USA
| | - Lu Lu
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
| | - Jonathan K Pritchard
- Department of Genetics, Stanford University, Stanford, California 94305, USA
- Department of Biology, Stanford University, Stanford, California 94305, USA
| | - Alon Goren
- Department of Medicine, University of California San Diego, La Jolla, California 92093, USA
- Institute for Genomic Medicine, University of California San Diego, La Jolla, California 92093, USA
| | - Robert W Williams
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
| | - Abraham A Palmer
- Institute for Genomic Medicine, University of California San Diego, La Jolla, California 92093, USA
- Department of Psychiatry, Department of Medicine, University of California San Diego, La Jolla, California 92093, USA
| | - Melissa Gymrek
- Department of Medicine, University of California San Diego, La Jolla, California 92093, USA;
- Department of Computer Science and Engineering, University of California San Diego, La Jolla, California 92093, USA
- Institute for Genomic Medicine, University of California San Diego, La Jolla, California 92093, USA
- Department of Biomedical Informatics
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14
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Verbiest M, Maksimov M, Jin Y, Anisimova M, Gymrek M, Bilgin Sonay T. Mutation and selection processes regulating short tandem repeats give rise to genetic and phenotypic diversity across species. J Evol Biol 2023; 36:321-336. [PMID: 36289560 PMCID: PMC9990875 DOI: 10.1111/jeb.14106] [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: 02/08/2022] [Revised: 06/29/2022] [Accepted: 08/01/2022] [Indexed: 02/03/2023]
Abstract
Short tandem repeats (STRs) are units of 1-6 bp that repeat in a tandem fashion in DNA. Along with single nucleotide polymorphisms and large structural variations, they are among the major genomic variants underlying genetic, and likely phenotypic, divergence. STRs experience mutation rates that are orders of magnitude higher than other well-studied genotypic variants. Frequent copy number changes result in a wide range of alleles, and provide unique opportunities for modulating complex phenotypes through variation in repeat length. While classical studies have identified key roles of individual STR loci, the advent of improved sequencing technology, high-quality genome assemblies for diverse species, and bioinformatics methods for genome-wide STR analysis now enable more systematic study of STR variation across wide evolutionary ranges. In this review, we explore mutation and selection processes that affect STR copy number evolution, and how these processes give rise to varying STR patterns both within and across species. Finally, we review recent examples of functional and adaptive changes linked to STRs.
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Affiliation(s)
- Max Verbiest
- Institute of Computational Life Sciences, School of Life Sciences and Facility ManagementZürich University of Applied SciencesWädenswilSwitzerland
- Department of Molecular Life SciencesUniversity of ZurichZurichSwitzerland
- Swiss Institute of BioinformaticsLausanneSwitzerland
| | - Mikhail Maksimov
- Department of Computer Science & EngineeringUniversity of California San DiegoLa JollaCaliforniaUSA
- Department of MedicineUniversity of California San DiegoLa JollaCaliforniaUSA
| | - Ye Jin
- Department of MedicineUniversity of California San DiegoLa JollaCaliforniaUSA
- Department of BioengineeringUniversity of California San DiegoLa JollaCaliforniaUSA
| | - Maria Anisimova
- Institute of Computational Life Sciences, School of Life Sciences and Facility ManagementZürich University of Applied SciencesWädenswilSwitzerland
- Swiss Institute of BioinformaticsLausanneSwitzerland
| | - Melissa Gymrek
- Department of Computer Science & EngineeringUniversity of California San DiegoLa JollaCaliforniaUSA
- Department of MedicineUniversity of California San DiegoLa JollaCaliforniaUSA
| | - Tugce Bilgin Sonay
- Institute of Ecology, Evolution and Environmental BiologyColumbia UniversityNew YorkNew YorkUSA
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15
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Brown RE, Su XA, Fair S, Wu K, Verra L, Jong R, Andrykovich K, Freudenreich CH. The RNA export and RNA decay complexes THO and TRAMP prevent transcription-replication conflicts, DNA breaks, and CAG repeat contractions. PLoS Biol 2022; 20:e3001940. [PMID: 36574440 PMCID: PMC9829180 DOI: 10.1371/journal.pbio.3001940] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 01/09/2023] [Accepted: 12/01/2022] [Indexed: 12/28/2022] Open
Abstract
Expansion of structure-forming CAG/CTG repetitive sequences is the cause of several neurodegenerative disorders and deletion of repeats is a potential therapeutic strategy. Transcription-associated mechanisms are known to cause CAG repeat instability. In this study, we discovered that Thp2, an RNA export factor and member of the THO (suppressors of transcriptional defects of hpr1Δ by overexpression) complex, and Trf4, a key component of the TRAMP (Trf4/5-Air1/2-Mtr4 polyadenylation) complex involved in nuclear RNA polyadenylation and degradation, are necessary to prevent CAG fragility and repeat contractions in a Saccharomyces cerevisiae model system. Depletion of both Thp2 and Trf4 proteins causes a highly synergistic increase in CAG repeat fragility, indicating a complementary role of the THO and TRAMP complexes in preventing genome instability. Loss of either Thp2 or Trf4 causes an increase in RNA polymerase stalling at the CAG repeats and other genomic loci, as well as genome-wide transcription-replication conflicts (TRCs), implicating TRCs as a cause of CAG fragility and instability in their absence. Analysis of the effect of RNase H1 overexpression on CAG fragility, RNAPII stalling, and TRCs suggests that RNAPII stalling with associated R-loops are the main cause of CAG fragility in the thp2Δ mutants. In contrast, CAG fragility and TRCs in the trf4Δ mutant can be compensated for by RPA overexpression, suggesting that excess unprocessed RNA in TRAMP4 mutants leads to reduced RPA availability and high levels of TRCs. Our results show the importance of RNA surveillance pathways in preventing RNAPII stalling, TRCs, and DNA breaks, and show that RNA export and RNA decay factors work collaboratively to maintain genome stability.
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Affiliation(s)
- Rebecca E. Brown
- Program in Genetics, Tufts University School of Graduate Biomedical Sciences, Boston, Massachusetts, United States of America
| | - Xiaofeng A. Su
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
- David H. Koch Institute for Integrative Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Stacey Fair
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Katherine Wu
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Lauren Verra
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Robyn Jong
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Kristin Andrykovich
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Catherine H. Freudenreich
- Program in Genetics, Tufts University School of Graduate Biomedical Sciences, Boston, Massachusetts, United States of America
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
- * E-mail:
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16
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Khan ES, Danckwardt S. Pathophysiological Role and Diagnostic Potential of R-Loops in Cancer and Beyond. Genes (Basel) 2022; 13:genes13122181. [PMID: 36553448 PMCID: PMC9777984 DOI: 10.3390/genes13122181] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/07/2022] [Accepted: 11/14/2022] [Indexed: 11/24/2022] Open
Abstract
R-loops are DNA-RNA hybrids that play multifunctional roles in gene regulation, including replication, transcription, transcription-replication collision, epigenetics, and preserving the integrity of the genome. The aberrant formation and accumulation of unscheduled R-loops can disrupt gene expression and damage DNA, thereby causing genome instability. Recent links between unscheduled R-loop accumulation and the abundance of proteins that modulate R-loop biogenesis have been associated with numerous human diseases, including various cancers. Although R-loops are not necessarily causative for all disease entities described to date, they can perpetuate and even exacerbate the initially disease-eliciting pathophysiology, making them structures of interest for molecular diagnostics. In this review, we discuss the (patho) physiological role of R-loops in health and disease, their surprising diagnostic potential, and state-of-the-art techniques for their detection.
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Affiliation(s)
- Essak S. Khan
- Posttranscriptional Gene Regulation, Cancer Research and Experimental Hemostasis, University Medical Center Mainz, 55131 Mainz, Germany
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- Center for Thrombosis and Hemostasis (CTH), University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- German Consortium for Translational Cancer Research (DKTK), DKFZ Frankfurt-Mainz, 60590 Frankfurt am Main, Germany
| | - Sven Danckwardt
- Posttranscriptional Gene Regulation, Cancer Research and Experimental Hemostasis, University Medical Center Mainz, 55131 Mainz, Germany
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- Center for Thrombosis and Hemostasis (CTH), University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- German Center for Cardiovascular Research (DZHK), Rhine-Main, 55131 Mainz, Germany
- Correspondence:
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17
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Zhang J, Fakharzadeh A, Roland C, Sagui C. RNA as a Major-Groove Ligand: RNA-RNA and RNA-DNA Triplexes Formed by GAA and UUC or TTC Sequences. ACS OMEGA 2022; 7:38728-38743. [PMID: 36340174 PMCID: PMC9631886 DOI: 10.1021/acsomega.2c04358] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Accepted: 10/04/2022] [Indexed: 06/16/2023]
Abstract
Friedreich's ataxia is associated with noncanonical nucleic acid structures that emerge when GAA:TTC repeats in the first intron of the FXN gene expand beyond a critical number of repeats. Specifically, the noncanonical repeats are associated with both triplexes and R-loops. Here, we present an in silico investigation of all possible triplexes that form by attaching a third RNA strand to an RNA:RNA or DNA:DNA duplex, complementing previous DNA-based triplex studies. For both new triplexes results are similar. For a pyridimine UUC+ third strand, the parallel orientation is stable while its antiparallel counterpart is unstable. For a neutral GAA third strand, the parallel conformation is stable. A protonated GA+A third strand is stable in both parallel and antiparallel orientations. We have also investigated Na+ and Mg2+ ion distributions around the triplexes. The presence of Mg2+ ions helps stabilize neutral, antiparallel GAA triplexes. These results (along with previous DNA-based studies) allow for the emergence of a complete picture of the stability and structural characteristics of triplexes based on the GAA and TTC/UUC sequences, thereby contributing to the field of trinucleotide repeats and the associated unusual structures that trigger expansion.
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18
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Thada V, Greenberg RA. Unpaved roads: How the DNA damage response navigates endogenous genotoxins. DNA Repair (Amst) 2022; 118:103383. [PMID: 35939975 PMCID: PMC9703833 DOI: 10.1016/j.dnarep.2022.103383] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 07/28/2022] [Accepted: 07/28/2022] [Indexed: 02/03/2023]
Abstract
Accurate DNA repair is essential for cellular and organismal homeostasis, and DNA repair defects result in genetic diseases and cancer predisposition. Several environmental factors, such as ultraviolet light, damage DNA, but many other molecules with DNA damaging potential are byproducts of normal cellular processes. In this review, we highlight some of the prominent sources of endogenous DNA damage as well as their mechanisms of repair, with a special focus on repair by the homologous recombination and Fanconi anemia pathways. We also discuss how modulating DNA damage caused by endogenous factors may augment current approaches used to treat BRCA-deficient cancers. Finally, we describe how synthetic lethal interactions may be exploited to exacerbate DNA repair deficiencies and cause selective toxicity in additional types of cancers.
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19
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Cho IK, Easley CA, Chan AWS. Suppression of trinucleotide repeat expansion in spermatogenic cells in Huntington's disease. J Assist Reprod Genet 2022; 39:2413-2430. [PMID: 36066723 PMCID: PMC9596677 DOI: 10.1007/s10815-022-02594-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 08/09/2022] [Indexed: 11/16/2022] Open
Abstract
Trinucleotide repeats (TNRs) are dispersed throughout the human genome. About 20 loci are related to human diseases, such as Huntington's disease (HD). A larger TNR instability is predominantly observed in the paternal germ cells in some TNR disorders. Suppressing the expansion during spermatogenesis can provide a unique opportunity to end the vicious cycle of genetic anticipation. Here, using an in vitro differentiation method to derive advanced spermatogenic cells, we investigated the efficacy of two therapeutic agents, araC (cytarabine) and aspirin, on stabilizing TNRs in spermatogenic cells. Two WT patient-derived induced pluripotent stem cell (iPSC) lines and two HD hiPSC lines, with 44 Q and 180 Q, were differentiated into spermatogonial stem cell-like cells (SSCLCs). Both HD cell lines showed CAG tract expansion in SSCLC. When treated with araC and aspirin, HD1 showed moderate but not statistically significant stabilization of TNR. In HD2, 10 nM of aspirin and araC showed significant stabilization of TNR. All cell lines showed increased DNA damage response (DDR) gene expression in SSCLCs while more genes were significantly induced in HD SSCLC. In HD1, araC and aspirin treatment showed general suppression of DNA damage response genes. In HD2, only FAN1, OGG1, and PCNA showed significant suppression. When the methylation profile of HD cells was analyzed, FAN1 and OGG1 showed significant hypermethylation after the aspirin and araC treatment in SSCLC compared to the control. This study underscores the utility of our in vitro spermatogenesis model to study and develop therapies for TNR disorders such as HD.
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Affiliation(s)
- In K Cho
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA.
- Division of Neuropharmacology and Neurologic Diseases, Emory National Primate Research Center, Emory University, Atlanta, GA, USA.
- Department of Environmental Health Sciences, College of Public Health, University of Georgia, Athens, GA, USA.
- Regenerative Bioscience Center, University of Georgia, Athens, GA, USA.
- Environmental Health Science and Regenerative Bioscience Center, College of Public Health, University of Georgia, Edgar L. Rhodes Center for Animal and Dairy Science RM 432, 425 River Rd, Athens, GA, 30602, USA.
| | - Charles A Easley
- Division of Neuropharmacology and Neurologic Diseases, Emory National Primate Research Center, Emory University, Atlanta, GA, USA
- Department of Environmental Health Sciences, College of Public Health, University of Georgia, Athens, GA, USA
- Regenerative Bioscience Center, University of Georgia, Athens, GA, USA
| | - Anthony W S Chan
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA
- Division of Neuropharmacology and Neurologic Diseases, Emory National Primate Research Center, Emory University, Atlanta, GA, USA
- Center of Scientific Review (CSR), National Institutes of Health, Bethesda, USA
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20
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Detection of repeat expansions in large next generation DNA and RNA sequencing data without alignment. Sci Rep 2022; 12:13124. [PMID: 35907931 PMCID: PMC9338934 DOI: 10.1038/s41598-022-17267-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 07/22/2022] [Indexed: 11/10/2022] Open
Abstract
Bioinformatic methods for detecting short tandem repeat expansions in short-read sequencing have identified new repeat expansions in humans, but require alignment information to identify repetitive motif enrichment at genomic locations. We present superSTR, an ultrafast method that does not require alignment. superSTR is used to process whole-genome and whole-exome sequencing data, and perform the first STR analysis of the UK Biobank, efficiently screening and identifying known and potential disease-associated STRs in the exomes of 49,953 biobank participants. We demonstrate the first bioinformatic screening of RNA sequencing data to detect repeat expansions in humans and mouse models of ataxia and dystrophy.
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21
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Lawlor M, Zigo M, Kerns K, Cho IK, Easley IV CA, Sutovsky P. Spermatozoan Metabolism as a Non-Traditional Model for the Study of Huntington’s Disease. Int J Mol Sci 2022; 23:ijms23137163. [PMID: 35806166 PMCID: PMC9266437 DOI: 10.3390/ijms23137163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 06/22/2022] [Accepted: 06/27/2022] [Indexed: 12/10/2022] Open
Abstract
Huntington’s Disease (HD) is a fatal autosomal dominant neurodegenerative disease manifested through motor dysfunction and cognitive deficits. Decreased fertility is also observed in HD animal models and HD male patients, due to altered spermatogenesis and sperm function, thus resulting in reduced fertilization potential. Although some pharmaceuticals are currently utilized to mitigate HD symptoms, an effective treatment that remedies the pathogenesis of the disease is yet to be approved by the FDA. Identification of genes and relevant diagnostic biomarkers and therapeutic target pathways including glycolysis and mitochondrial complex-I-dependent respiration may be advantageous for early diagnosis, management, and treatment of the disease. This review addresses the HD pathway in neuronal and sperm metabolism, including relevant gene and protein expression in both neurons and spermatozoa, indicated in the pathogenesis of HD. Furthermore, zinc-containing and zinc-interacting proteins regulate and/or are regulated by zinc ion homeostasis in both neurons and spermatozoa. Therefore, this review also aims to explore the comparative role of zinc in both neuronal and sperm function. Ongoing studies aim to characterize the products of genes implicated in HD pathogenesis that are expressed in both neurons and spermatozoa to facilitate studies of future treatment avenues in HD and HD-related male infertility. The emerging link between zinc homeostasis and the HD pathway could lead to new treatments and diagnostic methods linking genetic sperm defects with somatic comorbidities.
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Affiliation(s)
- Meghan Lawlor
- Division of Animal Science, University of Missouri, Columbia, MO 65211, USA; (M.L.); (M.Z.); (K.K.)
| | - Michal Zigo
- Division of Animal Science, University of Missouri, Columbia, MO 65211, USA; (M.L.); (M.Z.); (K.K.)
| | - Karl Kerns
- Division of Animal Science, University of Missouri, Columbia, MO 65211, USA; (M.L.); (M.Z.); (K.K.)
- Department of Animal Science, Iowa State University, Ames, IA 50011, USA
| | - In Ki Cho
- Department of Environmental Health Science, College of Public Health, University of Georgia, Athens, GA 30602, USA; (I.K.C.); (C.A.E.IV)
- Regenerative Bioscience Center, University of Georgia, Athens, GA 30602, USA
| | - Charles A. Easley IV
- Department of Environmental Health Science, College of Public Health, University of Georgia, Athens, GA 30602, USA; (I.K.C.); (C.A.E.IV)
- Regenerative Bioscience Center, University of Georgia, Athens, GA 30602, USA
| | - Peter Sutovsky
- Division of Animal Science, University of Missouri, Columbia, MO 65211, USA; (M.L.); (M.Z.); (K.K.)
- Department of Obstetrics, Gynecology and Women’s Health, University of Missouri, Columbia, MO 65211, USA
- Correspondence: ; Tel.: +1-(573)-882-3329
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22
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Fakharzadeh A, Zhang J, Roland C, Sagui C. Novel eGZ-motif formed by regularly extruded guanine bases in a left-handed Z-DNA helix as a major motif behind CGG trinucleotide repeats. Nucleic Acids Res 2022; 50:4860-4876. [PMID: 35536254 PMCID: PMC9122592 DOI: 10.1093/nar/gkac339] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 04/19/2022] [Accepted: 05/05/2022] [Indexed: 12/19/2022] Open
Abstract
The expansion of d(CGG) trinucleotide repeats (TRs) lies behind several important neurodegenerative diseases. Atypical DNA secondary structures have been shown to trigger TR expansion: their characterization is important for a molecular understanding of TR disease. CD spectroscopy experiments in the last decade have unequivocally demonstrated that CGG runs adopt a left-handed Z-DNA conformation, whose features remain uncertain because it entails accommodating GG mismatches. In order to find this missing motif, we have carried out molecular dynamics (MD) simulations to explore all the possible Z-DNA helices that potentially form after the transition from B- to Z-DNA. Such helices combine either CpG or GpC Watson-Crick steps in Z-DNA form with GG-mismatch conformations set as either intrahelical or extrahelical; and participating in BZ or ZZ junctions or in alternately extruded conformations. Characterization of the stability and structural features (especially overall left-handedness, higher-temperature and steered MD simulations) identified two novel Z-DNA helices: the most stable one displays alternately extruded Gs, and is followed by a helix with symmetrically extruded ZZ junctions. The G-extrusion favors a seamless stacking of the Watson-Crick base pairs; extruded Gs favor syn conformations and display hydrogen-bonding and stacking interactions. Such conformations could have the potential to hijack the MMR complex, thus triggering further expansion.
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Affiliation(s)
- Ashkan Fakharzadeh
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Jiahui Zhang
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Christopher Roland
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Celeste Sagui
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
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23
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Barbé L, Finkbeiner S. Genetic and Epigenetic Interplay Define Disease Onset and Severity in Repeat Diseases. Front Aging Neurosci 2022; 14:750629. [PMID: 35592702 PMCID: PMC9110800 DOI: 10.3389/fnagi.2022.750629] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 03/01/2022] [Indexed: 11/13/2022] Open
Abstract
Repeat diseases, such as fragile X syndrome, myotonic dystrophy, Friedreich ataxia, Huntington disease, spinocerebellar ataxias, and some forms of amyotrophic lateral sclerosis, are caused by repetitive DNA sequences that are expanded in affected individuals. The age at which an individual begins to experience symptoms, and the severity of disease, are partially determined by the size of the repeat. However, the epigenetic state of the area in and around the repeat also plays an important role in determining the age of disease onset and the rate of disease progression. Many repeat diseases share a common epigenetic pattern of increased methylation at CpG islands near the repeat region. CpG islands are CG-rich sequences that are tightly regulated by methylation and are often found at gene enhancer or insulator elements in the genome. Methylation of CpG islands can inhibit binding of the transcriptional regulator CTCF, resulting in a closed chromatin state and gene down regulation. The downregulation of these genes leads to some disease-specific symptoms. Additionally, a genetic and epigenetic interplay is suggested by an effect of methylation on repeat instability, a hallmark of large repeat expansions that leads to increasing disease severity in successive generations. In this review, we will discuss the common epigenetic patterns shared across repeat diseases, how the genetics and epigenetics interact, and how this could be involved in disease manifestation. We also discuss the currently available stem cell and mouse models, which frequently do not recapitulate epigenetic patterns observed in human disease, and propose alternative strategies to study the role of epigenetics in repeat diseases.
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Affiliation(s)
- Lise Barbé
- Center for Systems and Therapeutics, Gladstone Institutes, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
- Department of Physiology, University of California, San Francisco, San Francisco, CA, United States
| | - Steve Finkbeiner
- Center for Systems and Therapeutics, Gladstone Institutes, San Francisco, CA, United States
- Department of Neurology, University of California, San Francisco, San Francisco, CA, United States
- Department of Physiology, University of California, San Francisco, San Francisco, CA, United States
- *Correspondence: Steve Finkbeiner,
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Rider SD, Gadgil RY, Hitch DC, Damewood FJ, Zavada N, Shanahan M, Alhawach V, Shrestha R, Shin-Ya K, Leffak M. Stable G-quadruplex DNA structures promote replication-dependent genome instability. J Biol Chem 2022; 298:101947. [PMID: 35447109 PMCID: PMC9142560 DOI: 10.1016/j.jbc.2022.101947] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 04/12/2022] [Accepted: 04/13/2022] [Indexed: 10/27/2022] Open
Abstract
G-quadruplex (G4)-prone structures are abundant in mammalian genomes, where they have been shown to influence DNA replication, transcription, and genome stability. In this article, we constructed cells with a single ectopic homopurine/homopyrimidine repeat tract derived from the polycystic kidney disease type 1 (PKD1) locus, which is capable of forming triplex (H3) and G4 DNA structures. We show that ligand stabilization of these G4 structures results in deletions of the G4 consensus sequence, as well as kilobase deletions spanning the G4 and ectopic sites. Furthermore, we show that DNA double-strand breaks at the ectopic site are dependent on the nuclease Mus81. Hypermutagenesis during sister chromatid repair extends several kilobases from the G4 site and breaks at the G4 site resulting in microhomology-mediated translocations. To determine whether H3 or G4 structures are responsible for homopurine/homopyrimidine tract instability, we derived constructs and cell lines from the PKD1 repeat, which can only form H3 or G4 structures. Under normal growth conditions, we found that G4 cell lines lost the G4 consensus sequence early during clonal outgrowth, whereas H3 cells showed DNA instability early during outgrowth but only lost reporter gene expression after prolonged growth. Thus, both the H3 and G4 non-B conformation DNAs exhibit genomic instability, but they respond differently to endogenous replication stress. Our results show that the outcomes of replication-dependent double-strand breaks at non-B-DNAs model the instability observed in microhomology-mediated break-induced replication (BIR). Marked variability in the frequency of mutagenesis during BIR suggests possible dynamic heterogeneity in the BIR replisome.
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Affiliation(s)
- S Dean Rider
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio, USA
| | - Rujuta Yashodhan Gadgil
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio, USA
| | - David C Hitch
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio, USA
| | - French J Damewood
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio, USA
| | - Nathen Zavada
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio, USA
| | - Matilyn Shanahan
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio, USA
| | - Venicia Alhawach
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio, USA
| | - Resha Shrestha
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio, USA
| | - Kazuo Shin-Ya
- Biomedical Information Research Center, National Institute of Advanced Industrial Science and Technology, Koto-ku, Tokyo, Japan
| | - Michael Leffak
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, Ohio, USA.
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25
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Goswami R, Bello AI, Bean J, Costanzo KM, Omer B, Cornelio-Parra D, Odah R, Ahluwalia A, Allan SK, Nguyen N, Shores T, Aziz NA, Mohan RD. The Molecular Basis of Spinocerebellar Ataxia Type 7. Front Neurosci 2022; 16:818757. [PMID: 35401096 PMCID: PMC8987156 DOI: 10.3389/fnins.2022.818757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 02/07/2022] [Indexed: 11/19/2022] Open
Abstract
Spinocerebellar ataxia (SCA) type 7 (SCA7) is caused by a CAG trinucleotide repeat expansion in the ataxin 7 (ATXN7) gene, which results in polyglutamine expansion at the amino terminus of the ATXN7 protein. Although ATXN7 is expressed widely, the best characterized symptoms of SCA7 are remarkably tissue specific, including blindness and degeneration of the brain and spinal cord. While it is well established that ATXN7 functions as a subunit of the Spt Ada Gcn5 acetyltransferase (SAGA) chromatin modifying complex, the mechanisms underlying SCA7 remain elusive. Here, we review the symptoms of SCA7 and examine functions of ATXN7 that may provide further insights into its pathogenesis. We also examine phenotypes associated with polyglutamine expanded ATXN7 that are not considered symptoms of SCA7.
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Affiliation(s)
- Rituparna Goswami
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
| | - Abudu I. Bello
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
| | - Joe Bean
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
| | - Kara M. Costanzo
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
| | - Bwaar Omer
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
| | - Dayanne Cornelio-Parra
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
| | - Revan Odah
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
| | - Amit Ahluwalia
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
| | - Shefaa K. Allan
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
| | - Nghi Nguyen
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
| | - Taylor Shores
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
| | - N. Ahmad Aziz
- Population Health Sciences, German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Ryan D. Mohan
- Division of Biological and Biomedical Systems, School of Science and Engineering, University of Missouri-Kansas City, Kansas City, MO, United States
- *Correspondence: Ryan D. Mohan,
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27
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Abstract
At fifteen different genomic locations, the expansion of a CAG/CTG repeat causes a neurodegenerative or neuromuscular disease, the most common being Huntington's disease and myotonic dystrophy type 1. These disorders are characterized by germline and somatic instability of the causative CAG/CTG repeat mutations. Repeat lengthening, or expansion, in the germline leads to an earlier age of onset or more severe symptoms in the next generation. In somatic cells, repeat expansion is thought to precipitate the rate of disease. The mechanisms underlying repeat instability are not well understood. Here we review the mammalian model systems that have been used to study CAG/CTG repeat instability, and the modifiers identified in these systems. Mouse models have demonstrated prominent roles for proteins in the mismatch repair pathway as critical drivers of CAG/CTG instability, which is also suggested by recent genome-wide association studies in humans. We draw attention to a network of connections between modifiers identified across several systems that might indicate pathway crosstalk in the context of repeat instability, and which could provide hypotheses for further validation or discovery. Overall, the data indicate that repeat dynamics might be modulated by altering the levels of DNA metabolic proteins, their regulation, their interaction with chromatin, or by direct perturbation of the repeat tract. Applying novel methodologies and technologies to this exciting area of research will be needed to gain deeper mechanistic insight that can be harnessed for therapies aimed at preventing repeat expansion or promoting repeat contraction.
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Affiliation(s)
- Vanessa C. Wheeler
- Molecular Neurogenetics Unit, Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA,Department of Neurology, Harvard Medical School, Boston, MA, USA,Correspondence to: Vanessa C. Wheeler, Center for Genomic Medicine, Massachusetts Hospital, Boston MAA 02115, USA. E-mail: . and Vincent Dion, UK Dementia Research Institute at Cardiff University, Hadyn Ellis Building, Maindy Road, CF24 4HQ Cardiff, UK. E-mail:
| | - Vincent Dion
- UK Dementia Research Institute at Cardiff University, Hadyn Ellis Building, Maindy Road, Cardiff, UK,Correspondence to: Vanessa C. Wheeler, Center for Genomic Medicine, Massachusetts Hospital, Boston MAA 02115, USA. E-mail: . and Vincent Dion, UK Dementia Research Institute at Cardiff University, Hadyn Ellis Building, Maindy Road, CF24 4HQ Cardiff, UK. E-mail:
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28
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Gold MA, Whalen JM, Freon K, Hong Z, Iraqui I, Lambert SAE, Freudenreich CH. Restarted replication forks are error-prone and cause CAG repeat expansions and contractions. PLoS Genet 2021; 17:e1009863. [PMID: 34673780 PMCID: PMC8562783 DOI: 10.1371/journal.pgen.1009863] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 11/02/2021] [Accepted: 10/06/2021] [Indexed: 12/16/2022] Open
Abstract
Disease-associated trinucleotide repeats form secondary DNA structures that interfere with replication and repair. Replication has been implicated as a mechanism that can cause repeat expansions and contractions. However, because structure-forming repeats are also replication barriers, it has been unclear whether the instability occurs due to slippage during normal replication progression through the repeat, slippage or misalignment at a replication stall caused by the repeat, or during subsequent replication of the repeat by a restarted fork that has altered properties. In this study, we have specifically addressed the fidelity of a restarted fork as it replicates through a CAG/CTG repeat tract and its effect on repeat instability. To do this, we used a well-characterized site-specific replication fork barrier (RFB) system in fission yeast that creates an inducible and highly efficient stall that is known to restart by recombination-dependent replication (RDR), in combination with long CAG repeat tracts inserted at various distances and orientations with respect to the RFB. We find that replication by the restarted fork exhibits low fidelity through repeat sequences placed 2–7 kb from the RFB, exhibiting elevated levels of Rad52- and Rad8ScRad5/HsHLTF-dependent instability. CAG expansions and contractions are not elevated to the same degree when the tract is just in front or behind the barrier, suggesting that the long-traveling Polδ-Polδ restarted fork, rather than fork reversal or initial D-loop synthesis through the repeat during stalling and restart, is the greatest source of repeat instability. The switch in replication direction that occurs due to replication from a converging fork while the stalled fork is held at the barrier is also a significant contributor to the repeat instability profile. Our results shed light on a long-standing question of how fork stalling and RDR contribute to expansions and contractions of structure-forming trinucleotide repeats, and reveal that tolerance to replication stress by fork restart comes at the cost of increased instability of repetitive sequences. Trinucleotide repeat expansions are the cause of several muscular- and neuro-degenerative diseases, and further expansions during intergenerational inheritance often leads to an earlier age-of-onset in the offspring. Some intergenerational expansions appear to occur during germ cell replication, but how those replication-associated expansions arise is incompletely understood. Because there are many replication barriers in genomes, including the structure-forming repeats themselves, we investigated whether a repeat placed after such a barrier had altered instability. We discovered that a restarted replication fork traversing a CAG repeat tract is highly error prone and repeat expansions and contractions are more prevalent in this case compared to normal replication. These results reveal a mechanism for replication-associated repeat instability relevant to disease-associated trinucleotide repeat expansions.
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Affiliation(s)
- Michaela A. Gold
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Jenna M. Whalen
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Karine Freon
- Institut Curie, Université PSL, Orsay, France
- Université Paris-Saclay, Orsay, France
| | - Zixin Hong
- Department of Biology, Tufts University, Medford, Massachusetts, United States of America
| | - Ismail Iraqui
- Institut Curie, Université PSL, Orsay, France
- Université Paris-Saclay, Orsay, France
| | - Sarah A. E. Lambert
- Institut Curie, Université PSL, Orsay, France
- Université Paris-Saclay, Orsay, France
- Equipes Labélisées Ligue Nationale Contre Le Cancer, Orsay, France
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29
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Polleys EJ, Freudenreich CH. Homologous recombination within repetitive DNA. Curr Opin Genet Dev 2021; 71:143-153. [PMID: 34464817 DOI: 10.1016/j.gde.2021.08.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Revised: 08/06/2021] [Accepted: 08/12/2021] [Indexed: 12/16/2022]
Abstract
Many microsatellite DNA sequences are able to form non-B form DNA secondary structures, such as hairpin loops, cruciforms, triplex DNA or G-quadruplexes. These DNA structures can form a significant impediment to DNA replication and repair, leading to DNA nicks, gaps, and breaks, which can be repaired by homologous recombination (HR). Recent work understanding HR at structure-forming repeats has focused on genetic requirements for replication fork restart, break induced replication (BIR) at broken forks, recombination during and after relocalization of breaks or stalled forks to the nuclear periphery, and how repair pathway choice and kinetics are navigated in the presence of a repeat tract. In this review, we summarize recent developments that illuminate the role of recombination in repairing DNA damage or causing tract length changes within repetitive DNA and its role in maintaining genome stability.
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Affiliation(s)
- Erica J Polleys
- Department of Biology, Tufts University, Medford MA 02155, United States
| | - Catherine H Freudenreich
- Department of Biology, Tufts University, Medford MA 02155, United States; Program in Genetics, Tufts University, Boston MA 02111, United States.
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30
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APOBECs orchestrate genomic and epigenomic editing across health and disease. Trends Genet 2021; 37:1028-1043. [PMID: 34353635 DOI: 10.1016/j.tig.2021.07.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 07/03/2021] [Accepted: 07/05/2021] [Indexed: 12/17/2022]
Abstract
APOBEC proteins can deaminate cytosine residues in DNA and RNA. This can lead to somatic mutations, DNA breaks, RNA modifications, or DNA demethylation in a selective manner. APOBECs function in various cellular compartments and recognize different nucleic acid motifs and structures. They orchestrate a wide array of genomic and epigenomic modifications, thereby affecting various cellular functions positively or negatively, including immune editing, viral and retroelement restriction, DNA damage responses, DNA demethylation, gene expression, and tissue homeostasis. Furthermore, the cumulative increase in genomic and epigenomic editing with aging could also, at least in part, be attributed to APOBEC function. We synthesize our cumulative understanding of APOBEC activity in a unifying overview and discuss their genomic and epigenomic impact in physiological, pathological, and technological contexts.
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31
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Kok JR, Palminha NM, Dos Santos Souza C, El-Khamisy SF, Ferraiuolo L. DNA damage as a mechanism of neurodegeneration in ALS and a contributor to astrocyte toxicity. Cell Mol Life Sci 2021; 78:5707-5729. [PMID: 34173837 PMCID: PMC8316199 DOI: 10.1007/s00018-021-03872-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 04/27/2021] [Accepted: 06/05/2021] [Indexed: 12/11/2022]
Abstract
Increasing evidence supports the involvement of DNA damage in several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Elevated levels of DNA damage are consistently observed in both sporadic and familial forms of ALS and may also play a role in Western Pacific ALS, which is thought to have an environmental cause. The cause of DNA damage in ALS remains unclear but likely differs between genetic subgroups. Repeat expansion in the C9ORF72 gene is the most common genetic cause of familial ALS and responsible for about 10% of sporadic cases. These genetic mutations are known to cause R-loops, thus increasing genomic instability and DNA damage, and generate dipeptide repeat proteins, which have been shown to lead to DNA damage and impairment of the DNA damage response. Similarly, several genes associated with ALS including TARDBP, FUS, NEK1, SQSTM1 and SETX are known to play a role in DNA repair and the DNA damage response, and thus may contribute to neuronal death via these pathways. Another consistent feature present in both sporadic and familial ALS is the ability of astrocytes to induce motor neuron death, although the factors causing this toxicity remain largely unknown. In this review, we summarise the evidence for DNA damage playing a causative or secondary role in the pathogenesis of ALS as well as discuss the possible mechanisms involved in different genetic subtypes with particular focus on the role of astrocytes initiating or perpetuating DNA damage in neurons.
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Affiliation(s)
- Jannigje Rachel Kok
- University of Sheffield, Sheffield Institute for Translational Neuroscience (SITraN), Sheffield, UK
| | - Nelma M Palminha
- Department of Molecular Biology and Biotechnology, The Healthy Lifespan Institute, Sheffield, UK
- The Institute of Neuroscience, University of Sheffield, Sheffield, UK
| | - Cleide Dos Santos Souza
- University of Sheffield, Sheffield Institute for Translational Neuroscience (SITraN), Sheffield, UK
| | - Sherif F El-Khamisy
- Department of Molecular Biology and Biotechnology, The Healthy Lifespan Institute, Sheffield, UK.
- The Institute of Neuroscience, University of Sheffield, Sheffield, UK.
- The Institute of Cancer Therapeutics, West Yorkshire, UK.
| | - Laura Ferraiuolo
- University of Sheffield, Sheffield Institute for Translational Neuroscience (SITraN), Sheffield, UK.
- The Institute of Neuroscience, University of Sheffield, Sheffield, UK.
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32
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Chatain J, Blond A, Phan AT, Saintomé C, Alberti P. GGGCTA repeats can fold into hairpins poorly unfolded by replication protein A: a possible origin of the length-dependent instability of GGGCTA variant repeats in human telomeres. Nucleic Acids Res 2021; 49:7588-7601. [PMID: 34214172 PMCID: PMC8287962 DOI: 10.1093/nar/gkab518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 06/01/2021] [Accepted: 06/30/2021] [Indexed: 11/19/2022] Open
Abstract
Human telomeres are composed of GGGTTA repeats and interspersed with variant repeats. The GGGCTA variant motif was identified in the proximal regions of human telomeres about 10 years ago and was shown to display a length-dependent instability. In parallel, a structural study showed that four GGGCTA repeats folded into a non-canonical G-quadruplex (G4) comprising a Watson-Crick GCGC tetrad. It was proposed that this non-canonical G4 might be an additional obstacle for telomere replication. In the present study, we demonstrate that longer GGGCTA arrays fold into G4 and into hairpins. We also demonstrate that replication protein A (RPA) efficiently binds to GGGCTA repeats structured into G4 but poorly binds to GGGCTA repeats structured into hairpins. Our results (along with results obtained with a more stable variant motif) suggest that GGGCTA hairpins are at the origin of GGGCTA length-dependent instability. They also suggest, as working hypothesis, that failure of efficient binding of RPA to GGGCTA structured into hairpins might be involved in the mechanism of GGGCTA array instability. On the basis of our present and past studies about telomeric G4 and their interaction with RPA, we propose an original point of view about telomeric G4 and the evolution of telomeric motifs.
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Affiliation(s)
- Jean Chatain
- Laboratoire Structure et Instabilité des Génomes (StrInG), Muséum national d’Histoire naturelle, CNRS, Inserm, Paris 75005, France
| | - Alain Blond
- Laboratoire Molécules de Communication et Adaptation des Microorganismes (MCAM), Muséum national d’Histoire naturelle, CNRS, Paris 75005, France
| | - Anh Tuân Phan
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
- NTU Institute of Structural Biology, Nanyang Technological University, Singapore 636921, Singapore
| | - Carole Saintomé
- Laboratoire Structure et Instabilité des Génomes (StrInG), Muséum national d’Histoire naturelle, CNRS, Inserm, Paris 75005, France
- Sorbonne Université, UFR927, Paris 75005, France
| | - Patrizia Alberti
- Laboratoire Structure et Instabilité des Génomes (StrInG), Muséum national d’Histoire naturelle, CNRS, Inserm, Paris 75005, France
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33
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Poggi L, Emmenegger L, Descorps-Declère S, Dumas B, Richard GF. Differential efficacies of Cas nucleases on microsatellites involved in human disorders and associated off-target mutations. Nucleic Acids Res 2021; 49:8120-8134. [PMID: 34233005 PMCID: PMC8373144 DOI: 10.1093/nar/gkab569] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 06/11/2021] [Accepted: 07/06/2021] [Indexed: 11/13/2022] Open
Abstract
Microsatellite expansions are the cause of >20 neurological or developmental human disorders. Shortening expanded repeats using specific DNA endonucleases may be envisioned as a gene editing approach. Here, we measured the efficacy of several CRISPR-Cas nucleases to induce recombination within disease-related microsatellites, in Saccharomyces cerevisiae. Broad variations in nuclease performances were detected on all repeat tracts. Wild-type Streptococcus pyogenes Cas9 (SpCas9) was more efficient than Staphylococcus aureus Cas9 on all repeats tested, except (CAG)33. Cas12a (Cpf1) was the most efficient on GAA trinucleotide repeats, whereas GC-rich repeats were more efficiently cut by SpCas9. The main genetic factor underlying Cas efficacy was the propensity of the recognition part of the sgRNA to form a stable secondary structure, independently of its structural part. This suggests that such structures form in vivo and interfere with sgRNA metabolism. The yeast genome contains 221 natural CAG/CTG and GAA/CTT trinucleotide repeats. Deep sequencing after nuclease induction identified three of them as carrying statistically significant low frequency mutations, corresponding to SpCas9 off-target double-strand breaks.
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Affiliation(s)
- Lucie Poggi
- Institut Pasteur, CNRS, UMR3525, 25 rue du Dr Roux, F-75015 Paris, France.,Sorbonne Université, Collège Doctoral, 4 Place Jussieu, F-75005 Paris, France.,Biologics Research, Sanofi R&D, 13 Quai Jules Guesde, 94403 Vitry sur Seine, France
| | - Lisa Emmenegger
- Institut Pasteur, CNRS, UMR3525, 25 rue du Dr Roux, F-75015 Paris, France
| | - Stéphane Descorps-Declère
- Institut Pasteur, CNRS, UMR3525, 25 rue du Dr Roux, F-75015 Paris, France.,Institut Pasteur, Bioinformatics and Biostatistics Hub, Department of Computational Biology, USR3756 CNRS, F-75015 Paris, France
| | - Bruno Dumas
- Biologics Research, Sanofi R&D, 13 Quai Jules Guesde, 94403 Vitry sur Seine, France
| | - Guy-Franck Richard
- Institut Pasteur, CNRS, UMR3525, 25 rue du Dr Roux, F-75015 Paris, France.,Sorbonne Université, Collège Doctoral, 4 Place Jussieu, F-75005 Paris, France
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34
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Porro A, Mohiuddin M, Zurfluh C, Spegg V, Dai J, Iehl F, Ropars V, Collotta G, Fishwick KM, Mozaffari NL, Guérois R, Jiricny J, Altmeyer M, Charbonnier JB, Pearson CE, Sartori AA. FAN1-MLH1 interaction affects repair of DNA interstrand cross-links and slipped-CAG/CTG repeats. SCIENCE ADVANCES 2021; 7:7/31/eabf7906. [PMID: 34330701 PMCID: PMC8324060 DOI: 10.1126/sciadv.abf7906] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 06/15/2021] [Indexed: 05/05/2023]
Abstract
FAN1, a DNA structure-specific nuclease, interacts with MLH1, but the repair pathways in which this complex acts are unknown. FAN1 processes DNA interstrand crosslinks (ICLs) and FAN1 variants are modifiers of the neurodegenerative Huntington's disease (HD), presumably by regulating HD-causing CAG repeat expansions. Here, we identify specific amino acid residues in two adjacent FAN1 motifs that are critical for MLH1 binding. Disruption of the FAN1-MLH1 interaction confers cellular hypersensitivity to ICL damage and defective repair of CAG/CTG slip-outs, intermediates of repeat expansion mutations. FAN1-S126 phosphorylation, which hinders FAN1-MLH1 association, is cell cycle-regulated by cyclin-dependent kinase activity and attenuated upon ICL induction. Our data highlight the FAN1-MLH1 complex as a phosphorylation-regulated determinant of ICL response and repeat stability, opening novel paths to modify cancer and neurodegeneration.
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Affiliation(s)
- Antonio Porro
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Mohiuddin Mohiuddin
- Program of Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Christina Zurfluh
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Vincent Spegg
- Department of Molecular Mechanisms of Disease, University of Zurich, Zurich, Switzerland
| | - Jingqi Dai
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Florence Iehl
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Virginie Ropars
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Giulio Collotta
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Keri M Fishwick
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Nour L Mozaffari
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Raphaël Guérois
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Josef Jiricny
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Matthias Altmeyer
- Department of Molecular Mechanisms of Disease, University of Zurich, Zurich, Switzerland
| | - Jean-Baptiste Charbonnier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Christopher E Pearson
- Program of Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.
- Program of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Alessandro A Sartori
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland.
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35
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Whalen JM, Dhingra N, Wei L, Zhao X, Freudenreich CH. Relocation of Collapsed Forks to the Nuclear Pore Complex Depends on Sumoylation of DNA Repair Proteins and Permits Rad51 Association. Cell Rep 2021; 31:107635. [PMID: 32402281 DOI: 10.1016/j.celrep.2020.107635] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 01/07/2020] [Accepted: 04/21/2020] [Indexed: 10/24/2022] Open
Abstract
Expanded CAG repeats form stem-loop secondary structures that lead to fork stalling and collapse. Previous work has shown that these collapsed forks relocalize to nuclear pore complexes (NPCs) in late S phase in a manner dependent on replication, the nucleoporin Nup84, and the Slx5 protein, which prevents repeat fragility and instability. Here, we show that binding of the Smc5/6 complex to the collapsed fork triggers Mms21-dependent sumoylation of fork-associated DNA repair proteins, and that RPA, Rad52, and Rad59 are the key sumoylation targets that mediate relocation. The SUMO interacting motifs of Slx5 target collapsed forks to the NPC. Notably, Rad51 foci only co-localize with the repeat after it is anchored to the nuclear periphery and Rad51 exclusion from the early collapsed fork is dependent on RPA sumoylation. This pathway may provide a mechanism to constrain recombination at stalled or collapsed forks until it is required for fork restart.
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Affiliation(s)
- Jenna M Whalen
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Nalini Dhingra
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Lei Wei
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Xiaolan Zhao
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Catherine H Freudenreich
- Department of Biology, Tufts University, Medford, MA 02155, USA; Program in Genetics, Tufts University, Boston, MA 02111, USA.
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36
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Richard GF. The Startling Role of Mismatch Repair in Trinucleotide Repeat Expansions. Cells 2021; 10:cells10051019. [PMID: 33925919 PMCID: PMC8145212 DOI: 10.3390/cells10051019] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 04/20/2021] [Accepted: 04/21/2021] [Indexed: 12/26/2022] Open
Abstract
Trinucleotide repeats are a peculiar class of microsatellites whose expansions are responsible for approximately 30 human neurological or developmental disorders. The molecular mechanisms responsible for these expansions in humans are not totally understood, but experiments in model systems such as yeast, transgenic mice, and human cells have brought evidence that the mismatch repair machinery is involved in generating these expansions. The present review summarizes, in the first part, the role of mismatch repair in detecting and fixing the DNA strand slippage occurring during microsatellite replication. In the second part, key molecular differences between normal microsatellites and those that show a bias toward expansions are extensively presented. The effect of mismatch repair mutants on microsatellite expansions is detailed in model systems, and in vitro experiments on mismatched DNA substrates are described. Finally, a model presenting the possible roles of the mismatch repair machinery in microsatellite expansions is proposed.
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Affiliation(s)
- Guy-Franck Richard
- Institut Pasteur, CNRS UMR3525, 25 rue du Docteur Roux, 75015 Paris, France
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37
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Khampang S, Parnpai R, Mahikul W, Easley CA, Cho IK, Chan AWS. CAG repeat instability in embryonic stem cells and derivative spermatogenic cells of transgenic Huntington's disease monkey. J Assist Reprod Genet 2021; 38:1215-1229. [PMID: 33611676 DOI: 10.1007/s10815-021-02106-3] [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: 12/07/2020] [Accepted: 02/08/2021] [Indexed: 12/16/2022] Open
Abstract
PURPOSE The expansion of CAG (glutamine; Q) trinucleotide repeats (TNRs) predominantly occurs through male lineage in Huntington's disease (HD). As a result, offspring will have larger CAG repeats compared to their fathers, which causes an earlier onset of the disease called genetic anticipation. This study aims to develop a novel in vitro model to replicate CAG repeat instability in early spermatogenesis and demonstrate the biological process of genetic anticipation by using the HD stem cell model for the first time. METHODS HD rhesus monkey embryonic stem cells (rESCs) were cultured in vitro for an extended period. Male rESCs were used to derive spermatogenic cells in vitro with a 10-day differentiation. The assessment of CAG repeat instability was performed by GeneScan and curve fit analysis. RESULTS Spermatogenic cells derived from rESCs exhibit progressive expansion of CAG repeats with high daily expansion rates compared to the extended culture of rESCs. The expansion of CAG repeats is cell type-specific and size-dependent. CONCLUSIONS Here, we report a novel stem cell model that replicates genome instability and CAG repeat expansion in in vitro derived HD monkey spermatogenic cells. The in vitro spermatogenic cell model opens a new opportunity for studying TNR instability and the underlying mechanism of genetic anticipation, not only in HD but also in other TNR diseases.
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Affiliation(s)
- Sujittra Khampang
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA.,Embryo Technology and Stem Cell Research Center, School of Biotechnology, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Rangsun Parnpai
- Embryo Technology and Stem Cell Research Center, School of Biotechnology, Suranaree University of Technology, Nakhon Ratchasima, Thailand
| | - Wiriya Mahikul
- Faculty of Medicine and Public Health, HRH Princess Chulabhorn College of Medical Science, Chulabhorn Royal Academy, Bangkok, Thailand
| | - Charles A Easley
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA.,Department of Environmental Health Science, College of Public Health, University of Georgia, Athens, GA, USA.,Regenerative Bioscience Center, University of Georgia, Athens, GA, USA
| | - In Ki Cho
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA. .,Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA.
| | - Anthony W S Chan
- Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA. .,Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA.
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38
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Gomes-Pereira M, Monckton DG. Chronic Exposure to Cadmium and Antioxidants Does Not Affect the Dynamics of Expanded CAG•CTG Trinucleotide Repeats in a Mouse Cell Culture System of Unstable DNA. Front Cell Neurosci 2021; 14:606331. [PMID: 33603644 PMCID: PMC7884634 DOI: 10.3389/fncel.2020.606331] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 12/29/2020] [Indexed: 12/02/2022] Open
Abstract
More than 30 human disorders are caused by the expansion of simple sequence DNA repeats, among which triplet repeats remain the most frequent. Most trinucleotide repeat expansion disorders affect primarily the nervous system, through mechanisms of neurodysfunction and/or neurodegeneration. While trinucleotide repeat tracts are short and stably transmitted in unaffected individuals, disease-associated expansions are highly dynamic in the germline and in somatic cells, with a tendency toward further expansion. Since longer repeats are associated with increasing disease severity and earlier onset of symptoms, intergenerational repeat size gains account for the phenomenon of anticipation. In turn, higher levels of age-dependent somatic expansion have been linked with increased disease severity and earlier age of onset, implicating somatic instability in the onset and progression of disease symptoms. Hence, tackling the root cause of symptoms through the control of repeat dynamics may provide therapeutic modulation of clinical manifestations. DNA repair pathways have been firmly implicated in the molecular mechanism of repeat length mutation. The demonstration that repeat expansion depends on functional DNA mismatch repair (MMR) proteins, points to MMR as a potential therapeutic target. Similarly, a role of DNA base excision repair (BER) in repeat expansion has also been suggested, particularly during the removal of oxidative lesions. Using a well-characterized mouse cell model system of an unstable CAG•CTG trinucleotide repeat, we tested if expanded repeat tracts can be stabilized by small molecules with reported roles in both pathways: cadmium (an inhibitor of MMR activity) and a variety of antioxidants (capable of neutralizing oxidative species). We found that chronic exposure to sublethal doses of cadmium and antioxidants did not result in significant reduction of the rate of trinucleotide repeat expansion. Surprisingly, manganese yielded a significant stabilization of the triplet repeat tract. We conclude that treatment with cadmium and antioxidants, at doses that do not interfere with cell survival and cell culture dynamics, is not sufficient to modify trinucleotide repeat dynamics in cell culture.
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Affiliation(s)
| | - Darren G Monckton
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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39
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Waisertreiger I, Barlow J. Fragile site instability: measuring more than breaks. Oncoscience 2020; 7:60-67. [PMID: 33195735 PMCID: PMC7640903 DOI: 10.18632/oncoscience.513] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 05/17/2020] [Indexed: 12/23/2022] Open
Abstract
Genome instability is not only a hallmark of cancer, it is necessary for its initiation and evolution, and naturally accumulates as cells age. Replication stress is a potent source of genome instability found in many tumor types [1]. Chromosomal fragile sites are genomic loci highly prone to DNA damage specifically from replication stress and are frequently mutated in cancer [2-4]2-4]. While tracking the origin of individual mutations has proved challenging, measuring DNA damage and repair at endogenous sites can offer key insights into understanding the etiology of cancer. In the past 15 years, the causal link between replication stress, oncogene activation, and tumor initiation and evolution has become increasingly clear [1, 5-9]. Replication-associated damage accumulates at early stages of tumorigenesis and may promote further transformation. Studying the causes and consequences of fragile site instability can offer a window into the earliest stages of carcinogenesis [10-13]. In particular, fragile site studies will help us understand the molecular underpinnings influencing the frequency of DNA breakage, successful repair processes suppressing genome instability, and unsuccessful repair leading to mutations and chromosome rearrangements. Of these, measuring successful repair is the most challenging as it leaves little evidence behind.
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Affiliation(s)
- Irina Waisertreiger
- Department of Microbiology and Molecular Genetics, University of California, Davis, CA, USA
| | - Jacqueline Barlow
- Department of Microbiology and Molecular Genetics & Genome Center, University of California, Davis, CA, USA
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40
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Zhang J, Fakharzadeh A, Pan F, Roland C, Sagui C. Atypical structures of GAA/TTC trinucleotide repeats underlying Friedreich's ataxia: DNA triplexes and RNA/DNA hybrids. Nucleic Acids Res 2020; 48:9899-9917. [PMID: 32821947 PMCID: PMC7515735 DOI: 10.1093/nar/gkaa665] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/27/2020] [Accepted: 08/04/2020] [Indexed: 11/13/2022] Open
Abstract
Expansion of the GAA/TTC repeats in the first intron of the FXN gene causes Friedreich's ataxia. Non-canonical structures are linked to this expansion. DNA triplexes and R-loops are believed to arrest transcription, which results in frataxin deficiency and eventual neurodegeneration. We present a systematic in silico characterization of the possible DNA triplexes that could be assembled with GAA and TTC strands; the two hybrid duplexes [r(GAA):d(TTC) and d(GAA):r(UUC)] in an R-loop; and three hybrid triplexes that could form during bidirectional transcription when the non-template DNA strand bonds with the hybrid duplex (collapsed R-loops, where the two DNA strands remain antiparallel). For both Y·R:Y and R·R:Y DNA triplexes, the parallel third strand orientation is more stable; both parallel and antiparallel protonated d(GA+A)·d(GAA):d(TTC) triplexes are stable. Apparent contradictions in the literature about the R·R:Y triplex stability is probably due to lack of molecular resolution, since shifting the third strand by a single nucleotide alters the stability ranking. In the collapsed R-loops, antiparallel d(TTC+)·d(GAA):r(UUC) is unstable, while parallel d(GAA)·r(GAA):d(TTC) and d(GA+A)·r(GAA):d(TTC) are stable. In addition to providing new structural perspectives for specific therapeutic aims, our results contribute to a systematic structural basis for the emerging field of quantitative R-loop biology.
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Affiliation(s)
- Jiahui Zhang
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Ashkan Fakharzadeh
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Feng Pan
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA.,Department of Statistics, Florida State University, Tallahassee, FL 32306, USA
| | - Christopher Roland
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
| | - Celeste Sagui
- Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA
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41
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Gaughran SK, Rickman JM, Haaga J, Gunton JD. Monte Carlo simulations of patch models with applications to soft matter. SOFT MATTER 2020; 16:8628-8638. [PMID: 32844865 DOI: 10.1039/d0sm01110j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Patch models have been employed to describe anisotropic interactions in disparate soft matter systems. In this work, we present a unified study of a patch model to explore particle self-assembly in both monodisperse and polydisperse systems, with applications to both proteins and colloids. In the first case, we obtained a temperature-density phase diagram for a model of the protein polyglutamine from Monte Carlo simulations. These simulations evinced clusters in the gas phase and, via a comparison with the corresponding coarse-grained PLUM model for this system, we verified that dense clustering in the gas phase falls into the supersaturation region of the saturation curve. In the second case, we have investigated the effect of size polydispersity on the phase behavior of binary colloidal mixtures. It was found that the width of gas-liquid phase coexistence increases with increasing polydispersity and that, in addition to the aforementioned particle clustering, small particles decorate patches on large particles, thereby creating large-particle bridges. Our aim is to compare and contrast self-assembly in these two prototypical systems.
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Affiliation(s)
- S K Gaughran
- Department of Physics, Lehigh University, Bethlehem, PA 18015, USA.
| | - J M Rickman
- Department of Physics, Lehigh University, Bethlehem, PA 18015, USA. and Department of Materials Science and Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - J Haaga
- Department of Physics, Lehigh University, Bethlehem, PA 18015, USA.
| | - J D Gunton
- Department of Physics, Lehigh University, Bethlehem, PA 18015, USA.
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42
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Hayward BE, Steinbach PJ, Usdin K. A point mutation in the nuclease domain of MLH3 eliminates repeat expansions in a mouse stem cell model of the Fragile X-related disorders. Nucleic Acids Res 2020; 48:7856-7863. [PMID: 32619224 DOI: 10.1093/nar/gkaa573] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 06/23/2020] [Accepted: 07/02/2020] [Indexed: 12/17/2022] Open
Abstract
The Fragile X-related disorders (FXDs) are Repeat Expansion Diseases, genetic disorders that result from the expansion of a disease-specific microsatellite. In those Repeat Expansion Disease models where it has been examined, expansion is dependent on functional mismatch repair (MMR) factors, including MutLγ, a heterodimer of MLH1/MLH3, one of the three MutL complexes found in mammals and a minor player in MMR. In contrast, MutLα, a much more abundant MutL complex that is the major contributor to MMR, is either not required for expansion or plays a limited role in expansion in many model systems. How MutLγ acts to generate expansions is unclear given its normal role in protecting against microsatellite instability and while MLH3 does have an associated endonuclease activity, whether that contributes to repeat expansion is uncertain. We show here, using a gene-editing approach, that a point mutation that eliminates the endonuclease activity of MLH3 eliminates expansions in an FXD mouse embryonic stem cell model. This restricts the number of possible models for repeat expansion and supports the idea that MutLγ may be a useful druggable target to reduce somatic expansion in those disorders where it contributes to disease pathology.
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Affiliation(s)
- Bruce E Hayward
- 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
| | - Peter J Steinbach
- Center for Molecular Modeling, Center for Information Technology, 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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43
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Long L, Li X, Wei H, Li W. Features of the Influence of a DNA Sequence on Its Adjacent Sequence. ACS OMEGA 2020; 5:23631-23644. [PMID: 32984683 PMCID: PMC7512436 DOI: 10.1021/acsomega.0c02264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 08/14/2020] [Indexed: 06/11/2023]
Abstract
To explore the features of the influence of a DNA sequence (here called sequence A) on its adjacent sequence (here called sequence B), we linked some DNA repeated sequences to the 5'-end of the T7 promoter in the plasmid pET-42a (+) or the 5'- and/or 3'-end(s) of the EcoRI site in some DNA fragments using PCR and other molecular cloning methods. As a result, we found that the efficiency of the T7 promoter and EcoRI could be impacted by some flanking sequences, indicating that sequence B could be impacted by sequence A. The features of such influence include the following: (i) sequence A can directly impact sequence B without changing/modifying the base composition of sequence B or destroying the inherent connection between sequence B and its function-related sequences; (ii) such influence does not need the participation of trans-acting factors or products of sequence A (if any); (iii) such an influence might be undetectable when the activities of trans-acting factors of sequence B are normal but might become detectable when those are lower than the normal one; (iv) such an influence might be enhancive, inhibitory, or unobvious; (v) the influence of sequence A linked to the 5'-end of sequence B might be the same as or opposite to that of sequence A linked to the 3'-end; and (vi) the influences of sequence A linked to different ends of sequence B could enhance or partially offset each other when sequence A is linked to both 5'- and 3'-ends of sequence B. These findings might give us a further understanding of the interaction of two adjacent DNA sequences.
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Affiliation(s)
- Lijuan Long
- Department
of Pediatrics, First Affiliated Hospital
of Guangxi Medical University, #6, Shuangyong Road, Nanning, 530021 Guangxi, China
| | - Xinxin Li
- Department
of Nuclear Medicine, First Affiliated Hospital
of Guangxi Medical University, #6, Shuangyong Road, Nanning, 530021 Guangxi, China
| | - Hailang Wei
- Medical
Scientific Research Center, Guangxi Medical
University, #22, Shuangyong Road, Nanning, 530021 Guangxi, China
| | - Wei Li
- Medical
Scientific Research Center, Guangxi Medical
University, #22, Shuangyong Road, Nanning, 530021 Guangxi, China
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44
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HDAC3 deacetylates the DNA mismatch repair factor MutSβ to stimulate triplet repeat expansions. Proc Natl Acad Sci U S A 2020; 117:23597-23605. [PMID: 32900932 PMCID: PMC7519323 DOI: 10.1073/pnas.2013223117] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Trinucleotide repeat (TNR) expansions cause nearly 20 severe human neurological diseases which are currently untreatable. For some of these diseases, ongoing somatic expansions accelerate disease progression and may influence age of onset. This new knowledge emphasizes the importance of understanding the protein factors that drive expansions. Recent genetic evidence indicates that the mismatch repair factor MutSβ (Msh2-Msh3 complex) and the histone deacetylase HDAC3 function in the same pathway to drive triplet repeat expansions. Here we tested the hypothesis that HDAC3 deacetylates MutSβ and thereby activates it to drive expansions. The HDAC3-selective inhibitor RGFP966 was used to examine its biological and biochemical consequences in human tissue culture cells. HDAC3 inhibition efficiently suppresses repeat expansion without impeding canonical mismatch repair activity. Five key lysine residues in Msh3 are direct targets of HDAC3 deacetylation. In cells expressing Msh3 in which these lysine residues are mutated to arginine, the inhibitory effect of RGFP966 on expansions is largely bypassed, consistent with the direct deacetylation hypothesis. RGFP966 treatment does not alter MutSβ subunit abundance or complex formation but does partially control its subcellular localization. Deacetylation sites in Msh3 overlap a nuclear localization signal, and we show that localization of MutSβ is partially dependent on HDAC3 activity. Together, these results indicate that MutSβ is a key target of HDAC3 deacetylation and provide insights into an innovative regulatory mechanism for triplet repeat expansions. The results suggest expansion activity may be druggable and support HDAC3-selective inhibition as an attractive therapy in some triplet repeat expansion diseases.
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45
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Gadgil RY, Romer EJ, Goodman CC, Rider SD, Damewood FJ, Barthelemy JR, Shin-Ya K, Hanenberg H, Leffak M. Replication stress at microsatellites causes DNA double-strand breaks and break-induced replication. J Biol Chem 2020; 295:15378-15397. [PMID: 32873711 DOI: 10.1074/jbc.ra120.013495] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 08/23/2020] [Indexed: 12/12/2022] Open
Abstract
Short tandemly repeated DNA sequences, termed microsatellites, are abundant in the human genome. These microsatellites exhibit length instability and susceptibility to DNA double-strand breaks (DSBs) due to their tendency to form stable non-B DNA structures. Replication-dependent microsatellite DSBs are linked to genome instability signatures in human developmental diseases and cancers. To probe the causes and consequences of microsatellite DSBs, we designed a dual-fluorescence reporter system to detect DSBs at expanded (CTG/CAG) n and polypurine/polypyrimidine (Pu/Py) mirror repeat structures alongside the c-myc replication origin integrated at a single ectopic chromosomal site. Restriction cleavage near the (CTG/CAG)100 microsatellite leads to homology-directed single-strand annealing between flanking AluY elements and reporter gene deletion that can be detected by flow cytometry. However, in the absence of restriction cleavage, endogenous and exogenous replication stressors induce DSBs at the (CTG/CAG)100 and Pu/Py microsatellites. DSBs map to a narrow region at the downstream edge of the (CTG)100 lagging-strand template. (CTG/CAG) n chromosome fragility is repeat length-dependent, whereas instability at the (Pu/Py) microsatellites depends on replication polarity. Strikingly, restriction-generated DSBs and replication-dependent DSBs are not repaired by the same mechanism. Knockdown of DNA damage response proteins increases (Rad18, polymerase (Pol) η, Pol κ) or decreases (Mus81) the sensitivity of the (CTG/CAG)100 microsatellites to replication stress. Replication stress and DSBs at the ectopic (CTG/CAG)100 microsatellite lead to break-induced replication and high-frequency mutagenesis at a flanking thymidine kinase gene. Our results show that non-B structure-prone microsatellites are susceptible to replication-dependent DSBs that cause genome instability.
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Affiliation(s)
- Rujuta Yashodhan Gadgil
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Eric J Romer
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Caitlin C Goodman
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - S Dean Rider
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - French J Damewood
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Joanna R Barthelemy
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA
| | - Kazuo Shin-Ya
- Biomedical Information Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo, Japan
| | - Helmut Hanenberg
- Department of Otorhinolaryngology and Head/Neck Surgery, Heinrich Heine University, Düsseldorf, Germany; Department of Pediatrics III, University Children's Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Michael Leffak
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio, USA.
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46
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Murat P, Guilbaud G, Sale JE. DNA polymerase stalling at structured DNA constrains the expansion of short tandem repeats. Genome Biol 2020; 21:209. [PMID: 32819438 PMCID: PMC7441554 DOI: 10.1186/s13059-020-02124-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 07/28/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Short tandem repeats (STRs) contribute significantly to de novo mutagenesis, driving phenotypic diversity and genetic disease. Although highly diverse, their repetitive sequences induce DNA polymerase slippage and stalling, leading to length and sequence variation. However, current studies of DNA synthesis through STRs are restricted to a handful of selected sequences, limiting our broader understanding of their evolutionary behaviour and hampering the characterisation of the determinants of their abundance and stability in eukaryotic genomes. RESULTS We perform a comprehensive analysis of DNA synthesis at all STR permutations and interrogate the impact of STR sequence and secondary structure on their genomic representation and mutability. To do this, we developed a high-throughput primer extension assay that allows monitoring of the kinetics and fidelity of DNA synthesis through 20,000 sequences comprising all STR permutations in different lengths. By combining these measurements with population-scale genomic data, we show that the response of a model replicative DNA polymerase to variously structured DNA is sufficient to predict the complex genomic behaviour of STRs, including abundance and mutational constraints. We demonstrate that DNA polymerase stalling at DNA structures induces error-prone DNA synthesis, which constrains STR expansion. CONCLUSIONS Our data support a model in which STR length in eukaryotic genomes results from a balance between expansion due to polymerase slippage at repeated DNA sequences and point mutations caused by error-prone DNA synthesis at DNA structures.
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Affiliation(s)
- Pierre Murat
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK.
| | - Guillaume Guilbaud
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Julian E Sale
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK.
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47
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Contractions of the C-Terminal Domain of Saccharomyces cerevisiae Rpb1p Are Mediated by Rad5p. G3-GENES GENOMES GENETICS 2020; 10:2543-2551. [PMID: 32467128 PMCID: PMC7341143 DOI: 10.1534/g3.120.401409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The C-terminal domain (CTD) is an essential domain of the largest subunit of RNA polymerase II, Rpb1p, and is composed of 26 tandem repeats of a seven-amino acid sequence, YSPTSPS. Despite being an essential domain within an essential gene, we have previously demonstrated that the CTD coding region is genetically unstable. Furthermore, yeast with a truncated or mutated CTD sequence are capable of promoting spontaneous genetic expansion or contraction of this coding region to improve fitness. We investigated the mechanism by which the CTD contracts using a tet-off reporter system for RPB1 to monitor genetic instability within the CTD coding region. We report that contractions require the post-replication repair factor Rad5p but, unlike expansions, not the homologous recombination factors Rad51p and Rad52p. Sequence analysis of contraction events reveals that deleted regions are flanked by microhomologies. We also find that G-quadruplex forming sequences predicted by the QGRS Mapper are enriched on the noncoding strand of the CTD compared to the body of RPB1. Formation of G-quadruplexes in the CTD coding region could block the replication fork, necessitating post-replication repair. We propose that contractions of the CTD result when microhomologies misalign during Rad5p-dependent template switching via fork reversal.
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Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS): Pathophysiology and Clinical Implications. Int J Mol Sci 2020; 21:ijms21124391. [PMID: 32575683 PMCID: PMC7352421 DOI: 10.3390/ijms21124391] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 05/23/2020] [Accepted: 05/28/2020] [Indexed: 02/06/2023] Open
Abstract
The fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder seen in older premutation (55-200 CGG repeats) carriers of FMR1. The premutation has excessive levels of FMR1 mRNA that lead to toxicity and mitochondrial dysfunction. The clinical features usually begin in the 60 s with an action or intention tremor followed by cerebellar ataxia, although 20% have only ataxia. MRI features include brain atrophy and white matter disease, especially in the middle cerebellar peduncles, periventricular areas, and splenium of the corpus callosum. Neurocognitive problems include memory and executive function deficits, although 50% of males can develop dementia. Females can be less affected by FXTAS because of a second X chromosome that does not carry the premutation. Approximately 40% of males and 16% of female carriers develop FXTAS. Since the premutation can occur in less than 1 in 200 women and 1 in 400 men, the FXTAS diagnosis should be considered in patients that present with tremor, ataxia, parkinsonian symptoms, neuropathy, and psychiatric problems. If a family history of a fragile X mutation is known, then FMR1 DNA testing is essential in patients with these symptoms.
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Lee D, Lee YI, Lee YS, Lee SB. The Mechanisms of Nuclear Proteotoxicity in Polyglutamine Spinocerebellar Ataxias. Front Neurosci 2020; 14:489. [PMID: 32581673 PMCID: PMC7289180 DOI: 10.3389/fnins.2020.00489] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Accepted: 04/20/2020] [Indexed: 12/29/2022] Open
Abstract
Polyglutamine (polyQ) spinocerebellar ataxias (SCAs) are the most prevalent subset of SCAs and share the aberrant expansion of Q-encoding CAG repeats within the coding sequences of disease-responsible genes as their common genetic cause. These polyQ SCAs (SCA1, SCA2, SCA3, SCA6, SCA7, and SCA17) are inherited neurodegenerative diseases characterized by the progressive atrophy of the cerebellum and connected regions of the nervous system, which leads to loss of fine muscle movement coordination. Upon the expansion of polyQ repeats, the mutated proteins typically accumulate disproportionately in the neuronal nucleus, where they sequester various target molecules, including transcription factors and other nuclear proteins. However, it is not yet clearly understood how CAG repeat expansion takes place or how expanded polyQ proteins accumulate in the nucleus. In this article, we review the current knowledge on the molecular and cellular bases of nuclear proteotoxicity of polyQ proteins in SCAs and present our perspectives on the remaining issues surrounding these diseases.
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Affiliation(s)
- Davin Lee
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea
| | - Yun-Il Lee
- Well Aging Research Center, Division of Biotechnology, Daegu Gyeongbuk Institute of Science and Technology, Daegu, South Korea
| | - Young-Sam Lee
- Well Aging Research Center, Division of Biotechnology, Daegu Gyeongbuk Institute of Science and Technology, Daegu, South Korea.,Department of New Biology, Daegu Gyeongbuk Institute of Science and Technology, Daegu, South Korea
| | - Sung Bae Lee
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, South Korea
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Daunay A, Duval A, Baudrin LG, Buhard O, Renault V, Deleuze JF, How-Kit A. Low temperature isothermal amplification of microsatellites drastically reduces stutter artifact formation and improves microsatellite instability detection in cancer. Nucleic Acids Res 2020; 47:e141. [PMID: 31584085 PMCID: PMC6868440 DOI: 10.1093/nar/gkz811] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 09/03/2019] [Accepted: 09/11/2019] [Indexed: 12/28/2022] Open
Abstract
Microsatellites are polymorphic short tandem repeats of 1–6 nucleotides ubiquitously present in the genome that are extensively used in living organisms as genetic markers and in oncology to detect microsatellite instability (MSI). While the standard analysis method of microsatellites is based on PCR followed by capillary electrophoresis, it generates undesirable frameshift products known as ‘stutter peaks’ caused by the polymerase slippage that can greatly complicate the analysis and interpretation of the data. Here we present an easy multiplexable approach replacing PCR that is based on low temperature isothermal amplification using recombinase polymerase amplification (LT-RPA) that drastically reduces and sometimes completely abolishes the formation of stutter artifacts, thus greatly simplifying the calling of the alleles. Using HT17, a mononucleotide DNA repeat that was previously proposed as an optimal marker to detect MSI in tumor DNA, we showed that LT-RPA improves the limit of detection of MSI compared to PCR up to four times, notably for small deletions, and simplifies the identification of the mutant alleles. It was successfully applied to clinical colorectal cancer samples and enabled detection of MSI. This easy-to-handle, rapid and cost-effective approach may deeply improve the analysis of microsatellites in several biological and clinical applications.
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Affiliation(s)
- Antoine Daunay
- Laboratory for Genomics, Foundation Jean Dausset - CEPH (Centre d'Etude du Polymorphisme Humain), Paris, France
| | - Alex Duval
- Sorbonne-Université, Université Pierre et Marie Curie - Paris 6, Paris, France, INSERM, UMRS 938-Centre de Recherche Saint-Antoine, Equipe 'Instabilité des Microsatellites et Cancers', Equipe labellisée par la Ligue Nationale contre le Cancer, and SIRIC CURAMUS, Paris, France Université Pierre et Marie Curie, Paris, France
| | - Laura G Baudrin
- Laboratory for Genomics, Foundation Jean Dausset - CEPH (Centre d'Etude du Polymorphisme Humain), Paris, France.,Laboratory of Excellence GenMed, Paris, France
| | - Olivier Buhard
- Sorbonne-Université, Université Pierre et Marie Curie - Paris 6, Paris, France, INSERM, UMRS 938-Centre de Recherche Saint-Antoine, Equipe 'Instabilité des Microsatellites et Cancers', Equipe labellisée par la Ligue Nationale contre le Cancer, and SIRIC CURAMUS, Paris, France Université Pierre et Marie Curie, Paris, France
| | - Victor Renault
- Laboratory for Bioinformatics, Foundation Jean Dausset - CEPH (Centre d'Etude du Polymorphisme Humain), Paris, France
| | - Jean-François Deleuze
- Laboratory for Genomics, Foundation Jean Dausset - CEPH (Centre d'Etude du Polymorphisme Humain), Paris, France.,Centre National de Recherche en Génomique Humaine, CEA-Institut François Jacob, Evry, France
| | - Alexandre How-Kit
- Laboratory for Genomics, Foundation Jean Dausset - CEPH (Centre d'Etude du Polymorphisme Humain), Paris, France
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