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Lee S, Lee S, Choi N, Kim J, Kweon J, Miller K, Kim J. PCAF promotes R-loop resolution via histone acetylation. Nucleic Acids Res 2024; 52:8643-8660. [PMID: 38936834 PMCID: PMC11347145 DOI: 10.1093/nar/gkae558] [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: 03/05/2024] [Revised: 06/04/2024] [Accepted: 06/19/2024] [Indexed: 06/29/2024] Open
Abstract
R-loops cause genome instability, disrupting normal cellular functions. Histone acetylation, particularly by p300/CBP-associated factor (PCAF), is essential for maintaining genome stability and regulating cellular processes. Understanding how R-loop formation and resolution are regulated is important because dysregulation of these processes can lead to multiple diseases, including cancer. This study explores the role of PCAF in maintaining genome stability, specifically for R-loop resolution. We found that PCAF depletion promotes the generation of R-loop structures, especially during ongoing transcription, thereby compromising genome stability. Mechanistically, we found that PCAF facilitates histone H4K8 acetylation, leading to recruitment of the a double-strand break repair protein (MRE11) and exonuclease 1 (EXO1) to R-loop sites. These in turn recruit Fanconi anemia (FA) proteins, including FANCM and BLM, to resolve the R-loop structure. Our findings suggest that PCAF, histone acetylation, and FA proteins collaborate to resolve R-loops and ensure genome stability. This study therefore provides novel mechanistic insights into the dynamics of R-loops as well as the role of PCAF in preserving genome stability. These results may help develop therapeutic strategies to target diseases associated with genome instability.
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Affiliation(s)
- Seo Yun Lee
- Department of Life Science and Multidisciplinary Genome Institute, Hallym University, Chuncheon 24252, Republic of Korea
| | - Soo Hyeon Lee
- Department of Life Science and Multidisciplinary Genome Institute, Hallym University, Chuncheon 24252, Republic of Korea
| | - Nak Hun Choi
- Department of Life Science and Multidisciplinary Genome Institute, Hallym University, Chuncheon 24252, Republic of Korea
| | - Ja Young Kim
- Department of Life Science and Multidisciplinary Genome Institute, Hallym University, Chuncheon 24252, Republic of Korea
| | - Jun Hee Kweon
- Department of Life Science and Multidisciplinary Genome Institute, Hallym University, Chuncheon 24252, Republic of Korea
| | - Kyle M Miller
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Jae Jin Kim
- Department of Life Science and Multidisciplinary Genome Institute, Hallym University, Chuncheon 24252, Republic of Korea
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2
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Wang JX, Wang XD, Hu MH. Novel quinoxaline analogs as telomeric G-quadruplex ligands exert antitumor effects related to enhanced immunomodulation. Eur J Med Chem 2024; 274:116536. [PMID: 38805936 DOI: 10.1016/j.ejmech.2024.116536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 05/21/2024] [Accepted: 05/25/2024] [Indexed: 05/30/2024]
Abstract
G-quadruplexes (G4s) are commonly formed in the G-rich strand of telomeric DNA. Ligands targeting telomeric G4 induce DNA damage and telomere dysfunction, which makes them potential antitumor drugs. New telomeric G4 ligands with drug-likeness are still needed to be exploited, especially with their antitumor mechanisms thoroughly discussed. In this study, a novel series of quinoxaline analogs were rationally designed and synthesized. Among them, R1 was the most promising ligand for its cytotoxic effects on tumor cells and stabilizing ability with telomeric G4. Cellular assays illustrated that R1 stabilized G4 and induced R-loop accumulation in the telomeric regions, subsequently triggering DNA damage responses, cell cycle arrest in G2/M phase, apoptosis and antiproliferation. Moreover, R1 evoked immunogenic cell death (ICD) in tumor cells, which promoted the maturation of bone marrow derived dendritic cells (BMDCs). In breast cancer mouse model, R1 exhibited a significant decrease in tumor burden through the immunomodulatory effects, including the increase of CD4+ and CD8+ T cells in tumors and cytokine levels in sera. Our research provides a new idea that targeting telomeric G4 induces DNA damage responses, causing antitumor effects both in vitro and in vivo, partially due to the enhancement of immunomodulation.
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Affiliation(s)
- Jia-Xin Wang
- Nation-Regional Engineering Lab for Synthetic Biology of Medicine, International Cancer Center, School of Pharmacy, Shenzhen University Medical School, Shenzhen, 518060, China
| | - Xiao-Dong Wang
- Nation-Regional Engineering Lab for Synthetic Biology of Medicine, International Cancer Center, School of Pharmacy, Shenzhen University Medical School, Shenzhen, 518060, China
| | - Ming-Hao Hu
- Nation-Regional Engineering Lab for Synthetic Biology of Medicine, International Cancer Center, School of Pharmacy, Shenzhen University Medical School, Shenzhen, 518060, China.
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3
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Li F, Zafar A, Luo L, Denning AM, Gu J, Bennett A, Yuan F, Zhang Y. R-Loops in Genome Instability and Cancer. Cancers (Basel) 2023; 15:4986. [PMID: 37894353 PMCID: PMC10605827 DOI: 10.3390/cancers15204986] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 10/04/2023] [Accepted: 10/11/2023] [Indexed: 10/29/2023] Open
Abstract
R-loops are unique, three-stranded nucleic acid structures that primarily form when an RNA molecule displaces one DNA strand and anneals to the complementary DNA strand in a double-stranded DNA molecule. R-loop formation can occur during natural processes, such as transcription, in which the nascent RNA molecule remains hybridized with the template DNA strand, while the non-template DNA strand is displaced. However, R-loops can also arise due to many non-natural processes, including DNA damage, dysregulation of RNA degradation pathways, and defects in RNA processing. Despite their prevalence throughout the whole genome, R-loops are predominantly found in actively transcribed gene regions, enabling R-loops to serve seemingly controversial roles. On one hand, the pathological accumulation of R-loops contributes to genome instability, a hallmark of cancer development that plays a role in tumorigenesis, cancer progression, and therapeutic resistance. On the other hand, R-loops play critical roles in regulating essential processes, such as gene expression, chromatin organization, class-switch recombination, mitochondrial DNA replication, and DNA repair. In this review, we summarize discoveries related to the formation, suppression, and removal of R-loops and their influence on genome instability, DNA repair, and oncogenic events. We have also discussed therapeutical opportunities by targeting pathological R-loops.
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Affiliation(s)
- Fang Li
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Alyan Zafar
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Liang Luo
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Ariana Maria Denning
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Jun Gu
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Ansley Bennett
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Fenghua Yuan
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | - Yanbin Zhang
- Department of Biochemistry & Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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4
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LaMarca EA, Saito A, Plaza-Jennings A, Espeso-Gil S, Hellmich A, Fernando MB, Javidfar B, Liao W, Estill M, Townsley K, Florio A, Ethridge JE, Do C, Tycko B, Shen L, Kamiya A, Tsankova NM, Brennand KJ, Akbarian S. R-loop landscapes in the developing human brain are linked to neural differentiation and cell-type specific transcription. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.18.549494. [PMID: 37503149 PMCID: PMC10370098 DOI: 10.1101/2023.07.18.549494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Here, we construct genome-scale maps for R-loops, three-stranded nucleic acid structures comprised of a DNA/RNA hybrid and a displaced single strand of DNA, in the proliferative and differentiated zones of the human prenatal brain. We show that R-loops are abundant in the progenitor-rich germinal matrix, with preferential formation at promoters slated for upregulated expression at later stages of differentiation, including numerous neurodevelopmental risk genes. RNase H1-mediated contraction of the genomic R-loop space in neural progenitors shifted differentiation toward the neuronal lineage and was associated with transcriptomic alterations and defective functional and structural neuronal connectivity in vivo and in vitro. Therefore, R-loops are important for fine-tuning differentiation-sensitive gene expression programs of neural progenitor cells.
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Affiliation(s)
- Elizabeth A LaMarca
- Graduate School of Biomedical Science, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Pamela Sklar Division of Psychiatric Genomics, Department of Genetics and Genomics, Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Atsushi Saito
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21218, USA
| | - Amara Plaza-Jennings
- Graduate School of Biomedical Science, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Sergio Espeso-Gil
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Allyse Hellmich
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Michael B Fernando
- Graduate School of Biomedical Science, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Pamela Sklar Division of Psychiatric Genomics, Department of Genetics and Genomics, Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Behnam Javidfar
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Will Liao
- New York Genome Center, New York, NY 10013, USA
| | - Molly Estill
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Kayla Townsley
- Graduate School of Biomedical Science, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Pamela Sklar Division of Psychiatric Genomics, Department of Genetics and Genomics, Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Anna Florio
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21218, USA
| | - James E Ethridge
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Catherine Do
- Center for Discovery and Innovation, Hackensack Meridian Health, 111 Ideation Way, Nutley, NJ 07110, USA
| | - Benjamin Tycko
- Center for Discovery and Innovation, Hackensack Meridian Health, 111 Ideation Way, Nutley, NJ 07110, USA
| | - Li Shen
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Atsushi Kamiya
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21218, USA
| | - Nadejda M Tsankova
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Kristen J Brennand
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Pamela Sklar Division of Psychiatric Genomics, Department of Genetics and Genomics, Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Current affiliation: Department of Psychiatry, Yale University, New Haven, CT 06511, USA
| | - Schahram Akbarian
- Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
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5
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Kannan A, Cuartas J, Gangwani P, Branzei D, Gangwani L. Mutation in senataxin alters the mechanism of R-loop resolution in amyotrophic lateral sclerosis 4. Brain 2022; 145:3072-3094. [PMID: 35045161 PMCID: PMC9536298 DOI: 10.1093/brain/awab464] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 11/08/2021] [Accepted: 12/03/2021] [Indexed: 11/22/2022] Open
Abstract
Mutation in the senataxin (SETX) gene causes an autosomal dominant neuromuscular disorder, amyotrophic lateral sclerosis 4 (ALS4), characterized by degeneration of motor neurons, muscle weakness and atrophy. SETX is an RNA-DNA helicase that mediates resolution of co-transcriptional RNA:DNA hybrids (R-loops). The process of R-loop resolution is essential for the normal functioning of cells, including neurons. The molecular basis of ALS4 pathogenesis and the mechanism of R-loop resolution are unclear. We report that the zinc finger protein ZPR1 binds to RNA:DNA hybrids, recruits SETX onto R-loops and is critical for R-loop resolution. ZPR1 deficiency disrupts the integrity of R-loop resolution complexes containing SETX and causes increased R-loop accumulation throughout gene transcription. We uncover that SETX is a downstream target of ZPR1 and that overexpression of ZPR1 can rescue R-loop resolution complexe assembly in SETX-deficient cells but not vice versa. To uncover the mechanism of R-loop resolution, we examined the function of SETX-ZPR1 complexes using two genetic motor neuron disease models with altered R-loop resolution. Notably, chronic low levels of SETX-ZPR1 complexes onto R-loops result in a decrease of R-loop resolution activity causing an increase in R-loop levels in spinal muscular atrophy. ZPR1 overexpression increases recruitment of SETX onto R-loops, decreases R-loops and rescues the spinal muscular atrophy phenotype in motor neurons and patient cells. Strikingly, interaction of SETX with ZPR1 is disrupted in ALS4 patients that have heterozygous SETX (L389S) mutation. ZPR1 fails to recruit the mutant SETX homodimer but recruits the heterodimer with partially disrupted interaction between SETX and ZPR1. Interestingly, disruption of SETX-ZPR1 complexes causes increase in R-loop resolution activity leading to fewer R-loops in ALS4. Modulation of ZPR1 levels regulates R-loop accumulation and rescues the pathogenic R-loop phenotype in ALS4 patient cells. These findings originate a new concept, ‘opposite alterations in a cell biological activity (R-loop resolution) result in similar pathogenesis (neurodegeneration) in different genetic motor neuron disorders’. We propose that ZPR1 collaborates with SETX and may function as a molecular brake to regulate SETX-dependent R-loop resolution activity critical for the normal functioning of motor neurons.
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Affiliation(s)
- Annapoorna Kannan
- Center of Emphasis in Neurosciences, Texas Tech University Health Sciences Center El Paso, El Paso, Texas 79905, USA
- Department of Molecular and Translational Medicine, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, El Paso, Texas 79905, USA
| | - Juliana Cuartas
- Center of Emphasis in Neurosciences, Texas Tech University Health Sciences Center El Paso, El Paso, Texas 79905, USA
- Department of Molecular and Translational Medicine, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, El Paso, Texas 79905, USA
| | - Pratik Gangwani
- Automated Driving Compute System Architecture, GM Global Technical Center - Sloan Engineering Center, Warren, Michigan 48092, USA
| | - Dana Branzei
- The FIRC Institute of Molecular Oncology Foundation, IFOM Foundation, Via Adamello 16, Milan 20139, Italy
- Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche (IGM-CNR), Via Abbiategrasso 207, 27100, Pavia, Italy
| | - Laxman Gangwani
- Center of Emphasis in Neurosciences, Texas Tech University Health Sciences Center El Paso, El Paso, Texas 79905, USA
- Department of Molecular and Translational Medicine, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, El Paso, Texas 79905, USA
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6
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Bohálová N, Dobrovolná M, Brázda V, Bidula S. Conservation and over-representation of G-quadruplex sequences in regulatory regions of mitochondrial DNA across distinct taxonomic sub-groups. Biochimie 2021; 194:28-34. [PMID: 34942301 DOI: 10.1016/j.biochi.2021.12.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 11/22/2021] [Accepted: 12/14/2021] [Indexed: 11/02/2022]
Abstract
G-quadruplexes have important regulatory roles in the nuclear genome but their distribution and potential roles in mitochondrial DNA (mtDNA) are poorly understood. We analysed 11883 mtDNA sequences from 18 taxonomic sub-groups and identified their frequency and location within mtDNA. Large differences in both the frequency and number of putative quadruplex-forming sequences (PQS) were observed amongst all the organisms and PQS frequency was negatively correlated with an increase in evolutionary age. PQS were over-represented in the 3'UTRs, D-loops, replication origins, and stem loops, indicating regulatory roles for quadruplexes in mtDNA. Variations of the G-quadruplex-forming sequence in the conserved sequence block II (CSBII) region of the human D-loop were conserved amongst other mammals, amphibians, birds, reptiles, and fishes. This D-loop PQS was conserved in the duplicated control regions of some birds and reptiles, indicating its importance to mitochondrial function. The guanine tracts in these PQS also displayed significant length heterogeneity and the length of these guanine tracts were generally longest in bird mtDNA. This information provides further insights into how G4s may contribute to the regulation and function of mtDNA and acts as a database of information for future studies investigating mitochondrial G4s in organisms other than humans.
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Affiliation(s)
- Natália Bohálová
- Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic; Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Michaela Dobrovolná
- Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic; Department of Food Chemistry and Biotechnology, Faculty of Chemistry, Brno University of Technology, Purkyňova 118, 61200, Brno, Czech Republic
| | - Václav Brázda
- Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic; Department of Food Chemistry and Biotechnology, Faculty of Chemistry, Brno University of Technology, Purkyňova 118, 61200, Brno, Czech Republic
| | - Stefan Bidula
- School of Biological Sciences, University of East Anglia, Norwich, UK.
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7
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Gao J, Zhang P, Li X, Wu W, Wei H, Zhang W. Toward an understanding of the detection and function of R-loops in plants. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:6110-6122. [PMID: 34115858 DOI: 10.1093/jxb/erab280] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 06/10/2021] [Indexed: 06/12/2023]
Abstract
Although lagging behind studies in humans and other mammals, studies of R-loops in plants have recently entered an exciting stage in which the roles of R-loops in gene expression, genome stability, epigenomic signatures, and plant development and stress responses are being elucidated. Here, we review the strengths and weaknesses of existing methodologies, which were largely developed for R-loop studies in mammals, and then discuss the potential challenges of applying these methodologies to R-loop studies in plants. We then focus on recent advances in the functional characterization of R-loops in Arabidopsis thaliana and rice. Recent studies in plants indicate that there are coordinated relationships between R-loops and gene expression, and between R-loops and epigenomic signatures that depend, in part, on the types of R-loops involved. Finally, we discuss the emerging roles of R-loops in plants and directions for future research.
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Affiliation(s)
- Jingjing Gao
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, JCIC-MCP, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing, Jiangsu 210095, China
| | - Pengyue Zhang
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, JCIC-MCP, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing, Jiangsu 210095, China
| | - Xinxu Li
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, JCIC-MCP, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing, Jiangsu 210095, China
| | - Wenqi Wu
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing 100083, China
| | - Hairong Wei
- College of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI 49931, USA
| | - Wenli Zhang
- State Key Laboratory for Crop Genetics and Germplasm Enhancement, JCIC-MCP, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing, Jiangsu 210095, China
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8
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Yan P, Liu Z, Song M, Wu Z, Xu W, Li K, Ji Q, Wang S, Liu X, Yan K, Esteban CR, Ci W, Belmonte JCI, Xie W, Ren J, Zhang W, Sun Q, Qu J, Liu GH. Genome-wide R-loop Landscapes during Cell Differentiation and Reprogramming. Cell Rep 2021; 32:107870. [PMID: 32640235 DOI: 10.1016/j.celrep.2020.107870] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 06/01/2020] [Accepted: 06/15/2020] [Indexed: 12/14/2022] Open
Abstract
DNA:RNA hybrids play key roles in both physiological and disease states by regulating chromatin and genome organization. Their homeostasis during cell differentiation and cell plasticity remains elusive. Using an isogenic human stem cell platform, we systematically characterize R-loops, DNA methylation, histone modifications, and chromatin accessibility in pluripotent cells and their lineage-differentiated derivatives. We confirm that a portion of R-loops formed co-transcriptionally at pluripotency genes in pluripotent stem cells and at lineage-controlling genes in differentiated lineages. Notably, a subset of R-loops maintained after differentiation are associated with repressive chromatin marks on silent pluripotency genes and undesired lineage genes. Moreover, in reprogrammed pluripotent cells, cell-of-origin-specific R-loops are initially present but are resolved with serial passaging. Our analysis suggests a multifaceted role of R-loops in cell fate determination that may serve as an additional layer of modulation on cell fate memory and cell plasticity.
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Affiliation(s)
- Pengze Yan
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zunpeng Liu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Moshi Song
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China
| | - Zeming Wu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wei Xu
- Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Kuan Li
- Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Qianzhao Ji
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Si Wang
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China
| | - Xiaoqian Liu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kaowen Yan
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China
| | | | - Weimin Ci
- China National Center for Bioinformation, Beijing 100101, China; CAS Key Laboratory of Genomic and Precision Medicine, Collaborative Innovation Center of Genetics and Development, School of Future Technology, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China
| | | | - Wei Xie
- Center for Stem Cell Biology and Regenerative Medicine, MOE Key Laboratory of Bioinformatics, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jie Ren
- China National Center for Bioinformation, Beijing 100101, China; CAS Key Laboratory of Genomic and Precision Medicine, Collaborative Innovation Center of Genetics and Development, School of Future Technology, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China
| | - Weiqi Zhang
- China National Center for Bioinformation, Beijing 100101, China; CAS Key Laboratory of Genomic and Precision Medicine, Collaborative Innovation Center of Genetics and Development, School of Future Technology, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China.
| | - Qianwen Sun
- Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing 100084, China.
| | - Jing Qu
- State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China.
| | - Guang-Hui Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; Beijing Institute for Brain Disorders, Advanced Innovation Center for Human Brain Protection, National Clinical Research Center for Geriatric Disorders, Xuanwu Hospital Capital Medical University, Beijing 100053, China; University of Chinese Academy of Sciences, Beijing 100049, China; Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing 100101, China.
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9
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Lam FC, Kong YW, Huang Q, Vu Han TL, Maffa AD, Kasper EM, Yaffe MB. BRD4 prevents the accumulation of R-loops and protects against transcription-replication collision events and DNA damage. Nat Commun 2020; 11:4083. [PMID: 32796829 PMCID: PMC7428008 DOI: 10.1038/s41467-020-17503-y] [Citation(s) in RCA: 78] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 06/17/2020] [Indexed: 12/20/2022] Open
Abstract
Proper chromatin function and maintenance of genomic stability depends on spatiotemporal coordination between the transcription and replication machinery. Loss of this coordination can lead to DNA damage from increased transcription-replication collision events. We report that deregulated transcription following BRD4 loss in cancer cells leads to the accumulation of RNA:DNA hybrids (R-loops) and collisions with the replication machinery causing replication stress and DNA damage. Whole genome BRD4 and γH2AX ChIP-Seq with R-loop IP qPCR reveals that BRD4 inhibition leads to accumulation of R-loops and DNA damage at a subset of known BDR4, JMJD6, and CHD4 co-regulated genes. Interference with BRD4 function causes transcriptional downregulation of the DNA damage response protein TopBP1, resulting in failure to activate the ATR-Chk1 pathway despite increased replication stress, leading to apoptotic cell death in S-phase and mitotic catastrophe. These findings demonstrate that inhibition of BRD4 induces transcription-replication conflicts, DNA damage, and cell death in oncogenic cells.
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Affiliation(s)
- Fred C Lam
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge, MA, 02139, USA.
- Center for Precision Cancer Medicine, Massachusetts Institute of Technology, 500 Main Street, Cambridge, MA, 02139, USA.
- Faculty of Health Sciences, Division of Neurosurgery, Hamilton General Hospital, McMaster University, 237 Barton St E, Hamilton, ON, L8L 2X2, Canada.
| | - Yi Wen Kong
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge, MA, 02139, USA
- Center for Precision Cancer Medicine, Massachusetts Institute of Technology, 500 Main Street, Cambridge, MA, 02139, USA
| | - Qiuying Huang
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge, MA, 02139, USA
| | - Tu-Lan Vu Han
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge, MA, 02139, USA
| | - Amanda D Maffa
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge, MA, 02139, USA
| | - Ekkehard M Kasper
- Faculty of Health Sciences, Division of Neurosurgery, Hamilton General Hospital, McMaster University, 237 Barton St E, Hamilton, ON, L8L 2X2, Canada
| | - Michael B Yaffe
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, 500 Main Street, Cambridge, MA, 02139, USA.
- Center for Precision Cancer Medicine, Massachusetts Institute of Technology, 500 Main Street, Cambridge, MA, 02139, USA.
- Departments of Biology and Bioengineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
- Beth Israel Deaconess Medical Center, Department of Surgery, Harvard Medical School, Boston, MA, 02215, USA.
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10
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Reyes A, Rusecka J, Tońska K, Zeviani M. RNase H1 Regulates Mitochondrial Transcription and Translation via the Degradation of 7S RNA. Front Genet 2020; 10:1393. [PMID: 32082360 PMCID: PMC7006045 DOI: 10.3389/fgene.2019.01393] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 12/19/2019] [Indexed: 02/02/2023] Open
Abstract
RNase H1 is able to recognize DNA/RNA heteroduplexes and to degrade their RNA component. As a consequence, it has been implicated in different aspects of mtDNA replication such as primer formation, primer removal, and replication termination, and significant differences have been reported between control and mutant RNASEH1 skin fibroblasts from patients. However, neither mtDNA depletion nor the presence of deletions have been described in skin fibroblasts while still presenting signs of mitochondrial dysfunction (lower mitochondrial membrane potential, reduced oxygen consumption, slow growth in galactose). Here, we show that RNase H1 has an effect on mtDNA transcripts, most likely through the regulation of 7S RNA and other R-loops. The observed effect on both mitochondrial mRNAs and 16S rRNA results in decreased mitochondrial translation and subsequently mitochondrial dysfunction in cells carrying mutations in RNASEH1.
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Affiliation(s)
- Aurelio Reyes
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, United Kingdom,*Correspondence: Aurelio Reyes, ; Massimo Zeviani,
| | - Joanna Rusecka
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, United Kingdom,Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Katarzyna Tońska
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Massimo Zeviani
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, United Kingdom,*Correspondence: Aurelio Reyes, ; Massimo Zeviani,
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11
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Choi J, Hwang SY, Ahn K. Interplay between RNASEH2 and MOV10 controls LINE-1 retrotransposition. Nucleic Acids Res 2019; 46:1912-1926. [PMID: 29315404 PMCID: PMC5829647 DOI: 10.1093/nar/gkx1312] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 12/23/2017] [Indexed: 01/22/2023] Open
Abstract
Long interspersed nuclear element 1 is an autonomous non-long terminal repeat retrotransposon that comprises ∼17% of the human genome. Its spontaneous retrotransposition and the accumulation of heritable L1 insertions can potentially result in genome instability and sporadic disorders. Moloney leukemia virus 10 homolog (MOV10), a putative RNA helicase, has been implicated in inhibiting L1 replication, although its underlying mechanism of action remains obscure. Moreover, the physiological relevance of MOV10-mediated L1 regulation in human disease has not yet been examined. Using a proteomic approach, we identified RNASEH2 as a binding partner of MOV10. We show that MOV10 interacts with RNASEH2, and their interplay is crucial for restricting L1 retrotransposition. RNASEH2 and MOV10 co-localize in the nucleus, and RNASEH2 binds to L1 RNAs in a MOV10-dependent manner. Small hairpin RNA-mediated depletion of either RNASEH2A or MOV10 results in an accumulation of L1-specific RNA-DNA hybrids, suggesting they contribute to prevent formation of vital L1 heteroduplexes during retrotransposition. Furthermore, we show that RNASEH2-MOV10-mediated L1 restriction downregulates expression of the rheumatoid arthritis-associated inflammatory cytokines and matrix-degrading proteinases in synovial cells, implicating a potential causal relationship between them and disease development in terms of disease predisposition.
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Affiliation(s)
- Jongsu Choi
- Center for RNA Research, Institute for Basic Science, Seoul 08826, Republic of Korea.,School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Sung-Yeon Hwang
- Center for RNA Research, Institute for Basic Science, Seoul 08826, Republic of Korea.,School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Kwangseog Ahn
- Center for RNA Research, Institute for Basic Science, Seoul 08826, Republic of Korea.,School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
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12
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Kannan A, Bhatia K, Branzei D, Gangwani L. Combined deficiency of Senataxin and DNA-PKcs causes DNA damage accumulation and neurodegeneration in spinal muscular atrophy. Nucleic Acids Res 2019; 46:8326-8346. [PMID: 30010942 PMCID: PMC6144794 DOI: 10.1093/nar/gky641] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 07/05/2018] [Indexed: 12/12/2022] Open
Abstract
Chronic low levels of survival motor neuron (SMN) protein cause spinal muscular atrophy (SMA). SMN is ubiquitously expressed, but the mechanisms underlying predominant neuron degeneration in SMA are poorly understood. We report that chronic low levels of SMN cause Senataxin (SETX)-deficiency, which results in increased RNA–DNA hybrids (R-loops) and DNA double-strand breaks (DSBs), and deficiency of DNA-activated protein kinase-catalytic subunit (DNA-PKcs), which impairs DSB repair. Consequently, DNA damage accumulates in patient cells, SMA mice neurons and patient spinal cord tissues. In dividing cells, DSBs are repaired by homologous recombination (HR) and non-homologous end joining (NHEJ) pathways, but neurons predominantly use NHEJ, which relies on DNA-PKcs activity. In SMA dividing cells, HR repairs DSBs and supports cellular proliferation. In SMA neurons, DNA-PKcs-deficiency causes defects in NHEJ-mediated repair leading to DNA damage accumulation and neurodegeneration. Restoration of SMN levels rescues SETX and DNA-PKcs deficiencies and DSB accumulation in SMA neurons and patient cells. Moreover, SETX overexpression in SMA neurons reduces R-loops and DNA damage, and rescues neurodegeneration. Our findings identify combined deficiency of SETX and DNA-PKcs stemming downstream of SMN as an underlying cause of DSBs accumulation, genomic instability and neurodegeneration in SMA and suggest SETX as a potential therapeutic target for SMA.
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Affiliation(s)
- Annapoorna Kannan
- Center of Emphasis in Neurosciences, Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, El Paso, TX 79905.,Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, El Paso, TX 79905
| | - Kanchan Bhatia
- Center of Emphasis in Neurosciences, Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, El Paso, TX 79905.,Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, El Paso, TX 79905
| | - Dana Branzei
- The FIRC Institute of Molecular Oncology Foundation, IFOM Foundation, Via Adamello 16, Milan 20139, Italy.,Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche (IGM-CNR), Via Abbiategrasso 207, Pavia 27100, Italy
| | - Laxman Gangwani
- Center of Emphasis in Neurosciences, Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, El Paso, TX 79905.,Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, El Paso, TX 79905.,Graduate School of Biomedical Sciences, Texas Tech University Health Sciences Center El Paso, El Paso, TX 79905, USA
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13
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Winkler C, Rouget R, Wu D, Beullens M, Van Eynde A, Bollen M. Overexpression of PP1-NIPP1 limits the capacity of cells to repair DNA double-strand breaks. J Cell Sci 2018; 131:jcs.214932. [PMID: 29898919 DOI: 10.1242/jcs.214932] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 05/29/2018] [Indexed: 12/20/2022] Open
Abstract
The ubiquitously expressed nuclear protein NIPP1 (also known as PPP1R8) recruits phosphoproteins for regulated dephosphorylation by the associated protein phosphatase PP1. To bypass the PP1 titration artifacts seen upon NIPP1 overexpression, we have engineered covalently linked fusions of PP1 and NIPP1, and demonstrate their potential to selectively explore the function of the PP1:NIPP1 holoenzyme. By using inducible stable cell lines, we show that PP1-NIPP1 fusions cause replication stress in a manner that requires both PP1 activity and substrate recruitment via the ForkHead Associated domain of NIPP1. More specifically, PP1-NIPP1 expression resulted in the build up of RNA-DNA hybrids (R-loops), enhanced chromatin compaction and a diminished repair of DNA double-strand breaks (DSBs), culminating in the accumulation of DSBs. These effects were associated with a reduced expression of DNA damage signaling and repair proteins. Our data disclose a key role for dephosphorylation of PP1:NIPP1 substrates in setting the threshold for DNA repair, and indicate that activators of this phosphatase hold therapeutic potential as sensitizers for DNA-damaging agents.
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Affiliation(s)
- Claudia Winkler
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Raphael Rouget
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Dan Wu
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Monique Beullens
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Aleyde Van Eynde
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Mathieu Bollen
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
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14
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Impact of spliceosome mutations on RNA splicing in myelodysplasia: dysregulated genes/pathways and clinical associations. Blood 2018; 132:1225-1240. [PMID: 29930011 DOI: 10.1182/blood-2018-04-843771] [Citation(s) in RCA: 152] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 06/11/2018] [Indexed: 12/14/2022] Open
Abstract
SF3B1, SRSF2, and U2AF1 are the most frequently mutated splicing factor genes in the myelodysplastic syndromes (MDS). We have performed a comprehensive and systematic analysis to determine the effect of these commonly mutated splicing factors on pre-mRNA splicing in the bone marrow stem/progenitor cells and in the erythroid and myeloid precursors in splicing factor mutant MDS. Using RNA-seq, we determined the aberrantly spliced genes and dysregulated pathways in CD34+ cells of 84 patients with MDS. Splicing factor mutations result in different alterations in splicing and largely affect different genes, but these converge in common dysregulated pathways and cellular processes, focused on RNA splicing, protein synthesis, and mitochondrial dysfunction, suggesting common mechanisms of action in MDS. Many of these dysregulated pathways and cellular processes can be linked to the known disease pathophysiology associated with splicing factor mutations in MDS, whereas several others have not been previously associated with MDS, such as sirtuin signaling. We identified aberrantly spliced events associated with clinical variables, and isoforms that independently predict survival in MDS and implicate dysregulation of focal adhesion and extracellular exosomes as drivers of poor survival. Aberrantly spliced genes and dysregulated pathways were identified in the MDS-affected lineages in splicing factor mutant MDS. Functional studies demonstrated that knockdown of the mitosis regulators SEPT2 and AKAP8, aberrantly spliced target genes of SF3B1 and SRSF2 mutations, respectively, led to impaired erythroid cell growth and differentiation. This study illuminates the effect of the common spliceosome mutations on the MDS phenotype and provides novel insights into disease pathophysiology.
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15
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Abstract
During transcription, the nascent transcript behind an elongating RNA polymerase (RNAP) can invade the DNA duplex and hybridize with the complementary DNA template strand, generating a three-stranded "R-loop" structure, composed of an RNA:DNA duplex and an unpaired non-template DNA strand. R-loops can be strongly associated with actively transcribed loci by all RNAPs including the mitochondrial RNA polymerase (mtRNAP). In this chapter, we describe two protocols for the detection of RNA:DNA hybrids in living budding yeast cells, one that uses conventional chromatin immunoprecipitation (ChIP-qPCR) and one that uses DNA:RNA immunoprecipitation (DRIP-qPCR). Both protocols make use of the S9.6 antibody, which is believed to recognize the intermediate A/B helical RNA:DNA duplex conformation, with no sequence specificity.
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Affiliation(s)
- Aziz El Hage
- Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, Edinburgh, EH9 3BF, UK.
| | - David Tollervey
- Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, Edinburgh, EH9 3BF, UK
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16
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Halász L, Karányi Z, Boros-Oláh B, Kuik-Rózsa T, Sipos É, Nagy É, Mosolygó-L Á, Mázló A, Rajnavölgyi É, Halmos G, Székvölgyi L. RNA-DNA hybrid (R-loop) immunoprecipitation mapping: an analytical workflow to evaluate inherent biases. Genome Res 2017; 27:1063-1073. [PMID: 28341774 PMCID: PMC5453320 DOI: 10.1101/gr.219394.116] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 03/23/2017] [Indexed: 12/16/2022]
Abstract
The impact of R-loops on the physiology and pathology of chromosomes has been demonstrated extensively by chromatin biology research. The progress in this field has been driven by technological advancement of R-loop mapping methods that largely relied on a single approach, DNA-RNA immunoprecipitation (DRIP). Most of the DRIP protocols use the experimental design that was developed by a few laboratories, without paying attention to the potential caveats that might affect the outcome of RNA-DNA hybrid mapping. To assess the accuracy and utility of this technology, we pursued an analytical approach to estimate inherent biases and errors in the DRIP protocol. By performing DRIP-sequencing, qPCR, and receiver operator characteristic (ROC) analysis, we tested the effect of formaldehyde fixation, cell lysis temperature, mode of genome fragmentation, and removal of free RNA on the efficacy of RNA-DNA hybrid detection and implemented workflows that were able to distinguish complex and weak DRIP signals in a noisy background with high confidence. We also show that some of the workflows perform poorly and generate random answers. Furthermore, we found that the most commonly used genome fragmentation method (restriction enzyme digestion) led to the overrepresentation of lengthy DRIP fragments over coding ORFs, and this bias was enhanced at the first exons. Biased genome sampling severely compromised mapping resolution and prevented the assignment of precise biological function to a significant fraction of R-loops. The revised workflow presented herein is established and optimized using objective ROC analyses and provides reproducible and highly specific RNA-DNA hybrid detection.
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Affiliation(s)
- László Halász
- MTA-DE Momentum, Genome Architecture and Recombination Research Group, Research Centre for Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
- Department of Biochemistry and Molecular Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - Zsolt Karányi
- MTA-DE Momentum, Genome Architecture and Recombination Research Group, Research Centre for Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
- Department of Internal Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Beáta Boros-Oláh
- MTA-DE Momentum, Genome Architecture and Recombination Research Group, Research Centre for Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
- Department of Biochemistry and Molecular Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - Tímea Kuik-Rózsa
- MTA-DE Momentum, Genome Architecture and Recombination Research Group, Research Centre for Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
- Department of Biochemistry and Molecular Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - Éva Sipos
- MTA-DE Momentum, Genome Architecture and Recombination Research Group, Research Centre for Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
- Department of Biopharmacy, University of Debrecen, 4032 Debrecen, Hungary
| | - Éva Nagy
- MTA-DE Momentum, Genome Architecture and Recombination Research Group, Research Centre for Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Ágnes Mosolygó-L
- MTA-DE Momentum, Genome Architecture and Recombination Research Group, Research Centre for Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
- Department of Biochemistry and Molecular Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - Anett Mázló
- Department of Immunology, University of Debrecen, 4032 Debrecen, Hungary
| | - Éva Rajnavölgyi
- Department of Immunology, University of Debrecen, 4032 Debrecen, Hungary
| | - Gábor Halmos
- Department of Biopharmacy, University of Debrecen, 4032 Debrecen, Hungary
| | - Lóránt Székvölgyi
- MTA-DE Momentum, Genome Architecture and Recombination Research Group, Research Centre for Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
- Department of Biochemistry and Molecular Biology, University of Debrecen, 4032 Debrecen, Hungary
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17
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Mitochondrial DNA replication: a PrimPol perspective. Biochem Soc Trans 2017; 45:513-529. [PMID: 28408491 PMCID: PMC5390496 DOI: 10.1042/bst20160162] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 02/20/2017] [Accepted: 02/21/2017] [Indexed: 12/20/2022]
Abstract
PrimPol, (primase-polymerase), the most recently identified eukaryotic polymerase, has roles in both nuclear and mitochondrial DNA maintenance. PrimPol is capable of acting as a DNA polymerase, with the ability to extend primers and also bypass a variety of oxidative and photolesions. In addition, PrimPol also functions as a primase, catalysing the preferential formation of DNA primers in a zinc finger-dependent manner. Although PrimPol's catalytic activities have been uncovered in vitro, we still know little about how and why it is targeted to the mitochondrion and what its key roles are in the maintenance of this multicopy DNA molecule. Unlike nuclear DNA, the mammalian mitochondrial genome is circular and the organelle has many unique proteins essential for its maintenance, presenting a differing environment within which PrimPol must function. Here, we discuss what is currently known about the mechanisms of DNA replication in the mitochondrion, the proteins that carry out these processes and how PrimPol is likely to be involved in assisting this vital cellular process.
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18
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Lyonnais S, Tarrés-Solé A, Rubio-Cosials A, Cuppari A, Brito R, Jaumot J, Gargallo R, Vilaseca M, Silva C, Granzhan A, Teulade-Fichou MP, Eritja R, Solà M. The human mitochondrial transcription factor A is a versatile G-quadruplex binding protein. Sci Rep 2017; 7:43992. [PMID: 28276514 PMCID: PMC5343656 DOI: 10.1038/srep43992] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 02/02/2017] [Indexed: 01/07/2023] Open
Abstract
The ability of the guanine-rich strand of the human mitochondrial DNA (mtDNA) to form G-quadruplex structures (G4s) has been recently highlighted, suggesting potential functions in mtDNA replication initiation and mtDNA stability. G4 structures in mtDNA raise the question of their recognition by factors associated with the mitochondrial nucleoid. The mitochondrial transcription factor A (TFAM), a high-mobility group (HMG)-box protein, is the major binding protein of human mtDNA and plays a critical role in its expression and maintenance. HMG-box proteins are pleiotropic sensors of DNA structural alterations. Thus, we investigated and uncovered a surprising ability of TFAM to bind to DNA or RNA G4 with great versatility, showing an affinity similar than to double-stranded DNA. The recognition of G4s by endogenous TFAM was detected in mitochondrial extracts by pull-down experiments using a G4-DNA from the mtDNA conserved sequence block II (CSBII). Biochemical characterization shows that TFAM binding to G4 depends on both the G-quartets core and flanking single-stranded overhangs. Additionally, it shows a structure-specific binding mode that differs from B-DNA, including G4-dependent TFAM multimerization. These TFAM-G4 interactions suggest functional recognition of G4s in the mitochondria.
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Affiliation(s)
- Sébastien Lyonnais
- Structural MitoLab, Structural Biology Unit, Molecular Biology Institute of Barcelona (CSIC), Barcelona, 08028, Spain
| | - Aleix Tarrés-Solé
- Structural MitoLab, Structural Biology Unit, Molecular Biology Institute of Barcelona (CSIC), Barcelona, 08028, Spain
| | - Anna Rubio-Cosials
- Structural MitoLab, Structural Biology Unit, Molecular Biology Institute of Barcelona (CSIC), Barcelona, 08028, Spain
| | - Anna Cuppari
- Structural MitoLab, Structural Biology Unit, Molecular Biology Institute of Barcelona (CSIC), Barcelona, 08028, Spain
| | - Reicy Brito
- Structural MitoLab, Structural Biology Unit, Molecular Biology Institute of Barcelona (CSIC), Barcelona, 08028, Spain
| | - Joaquim Jaumot
- Department of Chemical Engineering and Analytical Chemistry, University of Barcelona, Barcelona, 08028, Spain
| | - Raimundo Gargallo
- Department of Chemical Engineering and Analytical Chemistry, University of Barcelona, Barcelona, 08028, Spain
| | - Marta Vilaseca
- Mass Spectrometry Core Facility, Institute for Research in Biomedicine, IRB Barcelona, 08028 Barcelona, Spain
| | - Cristina Silva
- Structural MitoLab, Structural Biology Unit, Molecular Biology Institute of Barcelona (CSIC), Barcelona, 08028, Spain
| | - Anton Granzhan
- CNRS UMR9187, INSERM U1196, Institut Curie, Université Paris-Sud, 91405 Orsay, France
| | | | | | - Maria Solà
- Structural MitoLab, Structural Biology Unit, Molecular Biology Institute of Barcelona (CSIC), Barcelona, 08028, Spain
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19
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Sridhara SC, Carvalho S, Grosso AR, Gallego-Paez LM, Carmo-Fonseca M, de Almeida SF. Transcription Dynamics Prevent RNA-Mediated Genomic Instability through SRPK2-Dependent DDX23 Phosphorylation. Cell Rep 2017; 18:334-343. [DOI: 10.1016/j.celrep.2016.12.050] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 11/13/2016] [Accepted: 12/14/2016] [Indexed: 10/20/2022] Open
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20
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Nascent Connections: R-Loops and Chromatin Patterning. Trends Genet 2016; 32:828-838. [PMID: 27793359 DOI: 10.1016/j.tig.2016.10.002] [Citation(s) in RCA: 148] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 10/03/2016] [Accepted: 10/06/2016] [Indexed: 11/22/2022]
Abstract
RNA molecules, such as long noncoding RNAs (lncRNAs), have critical roles in regulating gene expression, chromosome architecture, and the modification states of chromatin. Recent developments suggest that RNA also influences gene expression and chromatin patterns through the interaction of nascent transcripts with their DNA template via the formation of co-transcriptional R-loop structures. R-loop formation over specific, conserved, hotspots occurs at thousands of genes in mammalian genomes and represents an important and dynamic feature of mammalian chromatin. Here, focusing primarily on mammalian systems, I describe the accumulating connections and possible mechanisms linking R-loop formation and chromatin patterning. The possible contribution of aberrant R-loops to pathological conditions is also discussed.
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21
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Tan BG, Wellesley FC, Savery NJ, Szczelkun MD. Length heterogeneity at conserved sequence block 2 in human mitochondrial DNA acts as a rheostat for RNA polymerase POLRMT activity. Nucleic Acids Res 2016; 44:7817-29. [PMID: 27436287 PMCID: PMC5027508 DOI: 10.1093/nar/gkw648] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 07/10/2016] [Indexed: 01/21/2023] Open
Abstract
The guanine (G)-tract of conserved sequence block 2 (CSB 2) in human mitochondrial DNA can result in transcription termination due to formation of a hybrid G-quadruplex between the nascent RNA and the nontemplate DNA strand. This structure can then influence genome replication, stability and localization. Here we surveyed the frequency of variation in sequence identity and length at CSB 2 amongst human mitochondrial genomes and used in vitro transcription to assess the effects of this length heterogeneity on the activity of the mitochondrial RNA polymerase, POLRMT. In general, increased G-tract length correlated with increased termination levels. However, variation in the population favoured CSB 2 sequences which produced efficient termination while particularly weak or strong signals were avoided. For all variants examined, the 3′ end of the transcripts mapped to the same downstream sequences and were prevented from terminating by addition of the transcription factor TEFM. We propose that CSB 2 length heterogeneity allows variation in the efficiency of transcription termination without affecting the position of the products or the capacity for regulation by TEFM.
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Affiliation(s)
- Benedict G Tan
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | - Frederick C Wellesley
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | - Nigel J Savery
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| | - Mark D Szczelkun
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
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Davis RR, Shaban NM, Perrino FW, Hollis T. Crystal structure of RNA-DNA duplex provides insight into conformational changes induced by RNase H binding. Cell Cycle 2015; 14:668-73. [PMID: 25664393 DOI: 10.4161/15384101.2014.994996] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
RNA-DNA hybrids play essential roles in a variety of biological processes, including DNA replication, transcription, and viral integration. Ribonucleotides incorporated within DNA are hydrolyzed by RNase H enzymes in a removal process that is necessary for maintaining genomic stability. In order to understand the structural determinants involved in recognition of a hybrid substrate by RNase H we have determined the crystal structure of a dodecameric non-polypurine/polypyrimidine tract RNA-DNA duplex. A comparison to the same sequence bound to RNase H, reveals structural changes to the duplex that include widening of the major groove to 12.5 Å from 4.2 Å and decreasing the degree of bending along the axis which may play a crucial role in the ribonucleotide recognition and cleavage mechanism within RNase H. This structure allows a direct comparison to be made about the conformational changes induced in RNA-DNA hybrids upon binding to RNase H and may provide insight into how dysfunction in the endonuclease causes disease.
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Affiliation(s)
- Ryan R Davis
- a Department of Biochemistry; Center for Structural Biology ; Wake Forest School of Medicine ; Winston-Salem , NC USA
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23
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Nadel J, Athanasiadou R, Lemetre C, Wijetunga NA, Ó Broin P, Sato H, Zhang Z, Jeddeloh J, Montagna C, Golden A, Seoighe C, Greally JM. RNA:DNA hybrids in the human genome have distinctive nucleotide characteristics, chromatin composition, and transcriptional relationships. Epigenetics Chromatin 2015; 8:46. [PMID: 26579211 PMCID: PMC4647656 DOI: 10.1186/s13072-015-0040-6] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 10/29/2015] [Indexed: 01/01/2023] Open
Abstract
Background RNA:DNA hybrids represent a non-canonical nucleic acid structure that has been associated with a range of human diseases and potential transcriptional regulatory functions. Mapping of RNA:DNA hybrids in human cells reveals them to have a number of characteristics that give insights into their functions. Results We find RNA:DNA hybrids to occupy millions of base pairs in the human genome. A directional sequencing approach shows the RNA component of the RNA:DNA hybrid to be purine-rich, indicating a thermodynamic contribution to their in vivo stability. The RNA:DNA hybrids are enriched at loci with decreased DNA methylation and increased DNase hypersensitivity, and within larger domains with characteristics of heterochromatin formation, indicating potential transcriptional regulatory properties. Mass spectrometry studies of chromatin at RNA:DNA hybrids shows the presence of the ILF2 and ILF3 transcription factors, supporting a model of certain transcription factors binding preferentially to the RNA:DNA conformation. Conclusions Overall, there is little to indicate a dependence for RNA:DNA hybrids forming co-transcriptionally, with results from the ribosomal DNA repeat unit instead supporting the intriguing model of RNA generating these structures intrans. The results of the study indicate heterogeneous functions of these genomic elements and new insights into their formation and stability in vivo. Electronic supplementary material The online version of this article (doi:10.1186/s13072-015-0040-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Julie Nadel
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA
| | - Rodoniki Athanasiadou
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA ; Department of Biology, Center for Genomics and Systems Biology, New York University, 12 Waverly Place, New York, NY 10003 USA
| | - Christophe Lemetre
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA ; Integrated Genomics Operation, Memorial Sloan-Kettering Cancer Center, New York, NY 10065 USA
| | - N Ari Wijetunga
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA
| | - Pilib Ó Broin
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA
| | - Hanae Sato
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA
| | - Zhengdong Zhang
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA
| | | | - Cristina Montagna
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA
| | - Aaron Golden
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA
| | - Cathal Seoighe
- School of Mathematics, Statistics and Applied Mathematics, National University of Ireland Galway, Galway, Ireland
| | - John M Greally
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA ; Department of Genetics, Center for Epigenomics and Division of Computational Genetics, Albert Einstein College of Medicine, 1301 Morris Park Avenue, Bronx, NY 10461 USA
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24
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Brown TA, Tkachuk AN, Clayton DA. Mitochondrial Transcription Factor A (TFAM) Binds to RNA Containing 4-Way Junctions and Mitochondrial tRNA. PLoS One 2015; 10:e0142436. [PMID: 26545237 PMCID: PMC4636309 DOI: 10.1371/journal.pone.0142436] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 10/21/2015] [Indexed: 11/26/2022] Open
Abstract
Mitochondrial DNA (mtDNA) is maintained within nucleoprotein complexes known as nucleoids. These structures are highly condensed by the DNA packaging protein, mitochondrial Transcription Factor A (TFAM). Nucleoids also include RNA, RNA:DNA hybrids, and are associated with proteins involved with RNA processing and mitochondrial ribosome biogenesis. Here we characterize the ability of TFAM to bind various RNA containing substrates in order to determine their role in TFAM distribution and function within the nucleoid. We find that TFAM binds to RNA-containing 4-way junctions but does not bind appreciably to RNA hairpins, internal loops, or linear RNA:DNA hybrids. Therefore the RNA within nucleoids largely excludes TFAM, and its distribution is not grossly altered with removal of RNA. Within the cell, TFAM binds to mitochondrial tRNAs, consistent with our RNA 4-way junction data. Kinetic binding assays and RNase-insensitive TFAM distribution indicate that DNA remains the preferred substrate within the nucleoid. However, TFAM binds to tRNA with nanomolar affinity and these complexes are not rare. TFAM-immunoprecipitated tRNAs have processed ends, suggesting that binding is not specific to RNA precursors. The amount of each immunoprecipitated tRNA is not well correlated with tRNA celluar abundance, indicating unequal TFAM binding preferences. TFAM-mt-tRNA interaction suggests potentially new functions for this protein.
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Affiliation(s)
- Timothy A. Brown
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
- * E-mail:
| | - Ariana N. Tkachuk
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - David A. Clayton
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
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25
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Koo CX, Kobiyama K, Shen YJ, LeBert N, Ahmad S, Khatoo M, Aoshi T, Gasser S, Ishii KJ. RNA polymerase III regulates cytosolic RNA:DNA hybrids and intracellular microRNA expression. J Biol Chem 2015; 290:7463-73. [PMID: 25623070 PMCID: PMC4367256 DOI: 10.1074/jbc.m115.636365] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
RNA:DNA hybrids form in the nuclei and mitochondria of cells as transcription-induced R-loops or G-quadruplexes, but exist only in the cytosol of virus-infected cells. Little is known about the existence of RNA:DNA hybrids in the cytosol of virus-free cells, in particular cancer or transformed cells. Here, we show that cytosolic RNA:DNA hybrids are present in various human cell lines, including transformed cells. Inhibition of RNA polymerase III (Pol III), but not DNA polymerase, abrogated cytosolic RNA:DNA hybrids. Cytosolic RNA:DNA hybrids bind to several components of the microRNA (miRNA) machinery-related proteins, including AGO2 and DDX17. Furthermore, we identified miRNAs that are specifically regulated by Pol III, providing a potential link between RNA:DNA hybrids and the miRNA machinery. One of the target genes, exportin-1, is shown to regulate cytosolic RNA:DNA hybrids. Taken together, we reveal previously unknown mechanism by which Pol III regulates the presence of cytosolic RNA:DNA hybrids and miRNA biogenesis in various human cells.
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Affiliation(s)
- Christine Xing'er Koo
- From the Immunology Programme and Department of Microbiology, Centre for Life Sciences, and the NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456, the Laboratory of Adjuvant Innovation and
| | - Kouji Kobiyama
- the Laboratory of Adjuvant Innovation and the Laboratory of Vaccine Science, World Premier International Immunology Frontier Research Center (iFREC), Osaka University, Suita, Osaka 565-0871, Japan
| | - Yu J Shen
- From the Immunology Programme and Department of Microbiology, Centre for Life Sciences, and the NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456
| | - Nina LeBert
- From the Immunology Programme and Department of Microbiology, Centre for Life Sciences, and
| | - Shandar Ahmad
- the Laboratory of Bioinformatics, National Institute of Biomedical Innovation (NIBIO), Ibaraki, Osaka 567-0085, Japan, and
| | - Muznah Khatoo
- From the Immunology Programme and Department of Microbiology, Centre for Life Sciences, and
| | - Taiki Aoshi
- the Laboratory of Adjuvant Innovation and the Laboratory of Vaccine Science, World Premier International Immunology Frontier Research Center (iFREC), Osaka University, Suita, Osaka 565-0871, Japan
| | - Stephan Gasser
- From the Immunology Programme and Department of Microbiology, Centre for Life Sciences, and the NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456,
| | - Ken J Ishii
- the Laboratory of Adjuvant Innovation and the Laboratory of Vaccine Science, World Premier International Immunology Frontier Research Center (iFREC), Osaka University, Suita, Osaka 565-0871, Japan
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26
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El Hage A, Webb S, Kerr A, Tollervey D. Genome-wide distribution of RNA-DNA hybrids identifies RNase H targets in tRNA genes, retrotransposons and mitochondria. PLoS Genet 2014; 10:e1004716. [PMID: 25357144 PMCID: PMC4214602 DOI: 10.1371/journal.pgen.1004716] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2014] [Accepted: 08/27/2014] [Indexed: 01/08/2023] Open
Abstract
During transcription, the nascent RNA can invade the DNA template, forming extended RNA-DNA duplexes (R-loops). Here we employ ChIP-seq in strains expressing or lacking RNase H to map targets of RNase H activity throughout the budding yeast genome. In wild-type strains, R-loops were readily detected over the 35S rDNA region, transcribed by Pol I, and over the 5S rDNA, transcribed by Pol III. In strains lacking RNase H activity, R-loops were elevated over other Pol III genes, notably tRNAs, SCR1 and U6 snRNA, and were also associated with the cDNAs of endogenous TY1 retrotransposons, which showed increased rates of mobility to the 5′-flanking regions of tRNA genes. Unexpectedly, R-loops were also associated with mitochondrial genes in the absence of RNase H1, but not of RNase H2. Finally, R-loops were detected on actively transcribed protein-coding genes in the wild-type, particularly over the second exon of spliced ribosomal protein genes. R-loops (RNA-DNA hybrids) are potentially deleterious for gene expression and genome stability, but can be beneficial, for example, during immunoglobulin gene class-switch recombination. Here we made use of antibody S9.6, with specificity for RNA-DNA duplexes independently of their sequence. The genome-wide distribution of R-loops in wild-type yeast showed association with the highly transcribed ribosomal DNA, and protein-coding genes, particularly the second exon of spliced genes. On RNA polymerase III loci such as the highly transcribed transfer RNA genes (tRNAs), R-loop accumulation was strongly detected in the absence of both ribonucleases H1 and H2 (RNase H1 and H2), indicating that R-loops are inherently formed but rapidly cleared by RNase H. Importantly, stable R-loops lead to reduced synthesis of tRNA precursors in mutants lacking RNase H and DNA topoisomerase activities. RNA-DNA hybrids associated with TY1 cDNA retrotransposition intermediates were elevated in the absence of RNase H, and this was accompanied by increased retrotransposition, in particular to 5′-flanking regions of tRNAs. Our findings show that RNase H participates in silencing of TY1 life cycle. Surprisingly, R-loops associated with mitochondrial transcription units were suppressed specifically by RNase H1. These findings have potentially important implications for understanding human diseases caused by mutations in RNase H.
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Affiliation(s)
- Aziz El Hage
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail: (AEH); (DT)
| | - Shaun Webb
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Alastair Kerr
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - David Tollervey
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail: (AEH); (DT)
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27
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Shi W, Miao XG, Kong XY. A novel model of double replications and random loss accounts for rearrangements in the Mitogenome of Samariscus latus (Teleostei: Pleuronectiformes). BMC Genomics 2014; 15:352. [PMID: 24885702 PMCID: PMC4035078 DOI: 10.1186/1471-2164-15-352] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 04/25/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Although more than one thousand complete mitochondrial DNA (mtDNA) sequences have been determined in teleostean fishes, only a few gene rearrangements have been observed, and genome-scale rearrangements are even rarer. However, flatfishes (Pleuronectiformes) have been identified as having diverse types of mitochondrial gene rearrangements. It has been reported that tongue soles and the blue flounder mitogenomes exhibit different types of large-scale gene rearrangements. RESULTS In the present study, the complete mitochondrial genome of another flatfish, Samariscus latus, was sequenced, and genome-scale rearrangements were observed. The genomic features of this flounder are different from those of any other studied vertebrates, including flatfish species too. The mitogenome of S. latus is characterized by the duplication and translocation of the control region (CR). The genes located between the two CRs are divided into two clusters in which their relative orders are maintained. CONCLUSIONS We propose a "Double Replications and Random Loss" model to explain the rearrangement events in S. latus mitogenome. This model consists of the following steps. First, the CR was duplicated and translocated. Subsequently, double replications of the mitogenome were successively initiated from the two CRs, leading to the duplication of the genes between the two CRs. Finally, one of each pair of duplicated genes was lost in a random event.
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Affiliation(s)
| | | | - Xiao-Yu Kong
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, People's Republic of China.
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28
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In D-loop: 40 years of mitochondrial 7S DNA. Exp Gerontol 2014; 56:175-81. [PMID: 24709344 DOI: 10.1016/j.exger.2014.03.027] [Citation(s) in RCA: 172] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 03/27/2014] [Accepted: 03/28/2014] [Indexed: 11/23/2022]
Abstract
Given the tiny size of the mammalian mitochondrial genome, at only 16.5 kb, it is often surprising how little we know about some of its molecular features, and the molecular mechanisms governing its maintenance. One such conundrum is the biogenesis and function of the mitochondrial displacement loop (D-loop). The mitochondrial D-loop is a triple-stranded region found in the major non-coding region (NCR) of many mitochondrial genomes, and is formed by stable incorporation of a third, short DNA strand known as 7S DNA. In this article we review the current affairs regarding the main features of the D-loop structure, the diverse frequency of D-loops in the mtDNAs of various species and tissues, and also the mechanisms of its synthesis and turnover. This is followed by an account of the possible functions of the mitochondrial D-loop that have been proposed over the last four decades. In the last section, we discuss the potential links of the D-loop with mammalian ageing.
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29
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Friedman JR, Nunnari J. Mitochondrial form and function. Nature 2014; 505:335-43. [PMID: 24429632 DOI: 10.1038/nature12985] [Citation(s) in RCA: 1167] [Impact Index Per Article: 116.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 11/22/2013] [Indexed: 02/08/2023]
Abstract
Mitochondria are one of the major ancient endomembrane systems in eukaryotic cells. Owing to their ability to produce ATP through respiration, they became a driving force in evolution. As an essential step in the process of eukaryotic evolution, the size of the mitochondrial chromosome was drastically reduced, and the behaviour of mitochondria within eukaryotic cells radically changed. Recent advances have revealed how the organelle's behaviour has evolved to allow the accurate transmission of its genome and to become responsive to the needs of the cell and its own dysfunction.
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Affiliation(s)
- Jonathan R Friedman
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616, USA
| | - Jodi Nunnari
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California 95616, USA
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30
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Szczesny RJ, Hejnowicz MS, Steczkiewicz K, Muszewska A, Borowski LS, Ginalski K, Dziembowski A. Identification of a novel human mitochondrial endo-/exonuclease Ddk1/c20orf72 necessary for maintenance of proper 7S DNA levels. Nucleic Acids Res 2013; 41:3144-61. [PMID: 23358826 PMCID: PMC3597694 DOI: 10.1093/nar/gkt029] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Although the human mitochondrial genome has been investigated for several decades, the proteins responsible for its replication and expression, especially nucleolytic enzymes, are poorly described. Here, we characterized a novel putative PD-(D/E)XK nuclease encoded by the human C20orf72 gene named Ddk1 for its predicted catalytic residues. We show that Ddk1 is a mitochondrially localized metal-dependent DNase lacking detectable ribonuclease activity. Ddk1 degrades DNA mainly in a 3'-5' direction with a strong preference for single-stranded DNA. Interestingly, Ddk1 requires free ends for its activity and does not degrade circular substrates. In addition, when a chimeric RNA-DNA substrate is provided, Ddk1 can slide over the RNA fragment and digest DNA endonucleolytically. Although the levels of the mitochondrial DNA are unchanged on RNAi-mediated depletion of Ddk1, the mitochondrial single-stranded DNA molecule (7S DNA) accumulates. On the other hand, overexperssion of Ddk1 decreases the levels of 7S DNA, suggesting an important role of the protein in 7S DNA regulation. We propose a structural model of Ddk1 and discuss its similarity to other PD-(D/E)XK superfamily members.
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Affiliation(s)
- Roman J Szczesny
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
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31
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Kazak L, Reyes A, Duncan AL, Rorbach J, Wood SR, Brea-Calvo G, Gammage PA, Robinson AJ, Minczuk M, Holt IJ. Alternative translation initiation augments the human mitochondrial proteome. Nucleic Acids Res 2012; 41:2354-69. [PMID: 23275553 PMCID: PMC3575844 DOI: 10.1093/nar/gks1347] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Alternative translation initiation (ATI) is a mechanism of producing multiple proteins from a single transcript, which in some cases regulates trafficking of proteins to different cellular compartments, including mitochondria. Application of a genome-wide computational screen predicts a cryptic mitochondrial targeting signal for 126 proteins in mouse and man that is revealed when an AUG codon located downstream from the canonical initiator methionine codon is used as a translation start site, which we term downstream ATI (dATI). Experimental evidence in support of dATI is provided by immunoblotting of endogenous truncated proteins enriched in mitochondrial cell fractions or of co-localization with mitochondria using immunocytochemistry. More detailed cellular localization studies establish mitochondrial targeting of a member of the cytosolic poly(A) binding protein family, PABPC5, and of the RNA/DNA helicase PIF1α. The mitochondrial isoform of PABPC5 co-immunoprecipitates with the mitochondrial poly(A) polymerase, and is markedly reduced in abundance when mitochondrial DNA and RNA are depleted, suggesting it plays a role in RNA metabolism in the organelle. Like PABPC5 and PIF1α, most of the candidates identified by the screen are not currently annotated as mitochondrial proteins, and so dATI expands the human mitochondrial proteome.
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Affiliation(s)
- Lawrence Kazak
- MRC-Mitochondrial Biology Unit, Wellcome Trust-MRC Building, Cambridge CB2 0XY, UK
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32
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Kolesar JE, Wang CY, Taguchi YV, Chou SH, Kaufman BA. Two-dimensional intact mitochondrial DNA agarose electrophoresis reveals the structural complexity of the mammalian mitochondrial genome. Nucleic Acids Res 2012; 41:e58. [PMID: 23275548 PMCID: PMC3575812 DOI: 10.1093/nar/gks1324] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The mitochondrial genome exists in numerous structural conformations, complicating the study of mitochondrial DNA (mtDNA) metabolism. Here, we describe the development of 2D intact mtDNA agarose gel electrophoresis (2D-IMAGE) for the separation and detection of approximately two-dozen distinct topoisomers. Although the major topoisomers were well conserved across many cell and tissue types, unique differences in certain cells and tissues were also observed. RNase treatment revealed that partially hybridized RNAs associated primarily with covalently closed circular DNA, consistent with this structure being the template for transcription. Circular structures composed of RNA:DNA hybrids contained only heavy-strand DNA sequences, implicating them as lagging-strand replication intermediates. During recovery from replicative arrest, 2D-IMAGE showed changes in both template selection and replication products. These studies suggest that discrete topoisomers are associated with specific mtDNA-directed processes. Because of the increased resolution, 2D-IMAGE has the potential to identify novel mtDNA intermediates involved in replication or transcription, or pathology including oxidative linearization, deletions or depletion.
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Affiliation(s)
- Jill E Kolesar
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street VET220E, Philadelphia, PA 19104, USA
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33
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Chatre L, Ricchetti M. Large heterogeneity of mitochondrial DNA transcription and initiation of replication exposed by single-cell imaging. J Cell Sci 2012; 126:914-26. [PMID: 23239030 DOI: 10.1242/jcs.114322] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Mitochondrial DNA (mtDNA) replication and transcription are crucial for cell function, but these processes are poorly understood at the single-cell level. We describe a novel fluorescence in situ hybridization protocol, called mTRIP (mitochondrial transcription and replication imaging protocol), that reveals simultaneously mtDNA and RNA, and that can also be coupled to immunofluorescence for in situ protein examination. mTRIP reveals mitochondrial structures engaged in initiation of DNA replication by identification of a specific sequence in the regulatory D-loop, as well as unique transcription profiles in single human cells. We observe and quantify at least three classes of mitochondrial structures: (i) replication initiation active and transcript-positive (Ia-Tp); (ii) replication initiation silent and transcript-positive (Is-Tp); and (iii) replication initiation silent and transcript-negative (Is-Tn). Thus, individual mitochondria are dramatically heterogeneous within the same cell. Moreover, mTRIP exposes a mosaic of distinct nucleic acid patterns in the D-loop, including H-strand versus L-strand transcripts, and uncoupled rRNA transcription and mtDNA initiation of replication, which might have functional consequences in the regulation of the mtDNA. Finally, mTRIP identifies altered mtDNA processing in cells with unbalanced mtDNA content and function, including in human mitochondrial disorders. Thus, mTRIP reveals qualitative and quantitative alterations that provide additional tools for elucidating the dynamics of mtDNA processing in single cells and mitochondrial dysfunction in diseases.
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Affiliation(s)
- Laurent Chatre
- Institut Pasteur, Unité de Génétique Moléculaire des Levures, CNRS UMR 3525, 25 rue du Dr. Roux, 75724 Paris, France
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Abstract
Mammalian mitochondria contain their own genome that encodes mRNAs for thirteen essential subunits of the complexes performing oxidative phosphorylation as well as the RNA components (two rRNAs and 22 tRNAs) needed for their translation in mitochondria. All RNA species are produced from single polycistronic precursor RNAs, yet the relative concentrations of various RNAs differ significantly. This underscores the essential role of post-transcriptional mechanisms that control the maturation, stability and translation of mitochondrial RNAs. The present review provides a detailed summary on the role of RNA maturation in the regulation of mitochondrial gene expression, focusing mainly on messenger RNA polyadenylation and stability control. Furthermore, the role of mitochondrial ribosomal RNA stability, processing and modifications in the biogenesis of the mitochondrial ribosome is discussed.
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35
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Damas J, Carneiro J, Gonçalves J, Stewart JB, Samuels DC, Amorim A, Pereira F. Mitochondrial DNA deletions are associated with non-B DNA conformations. Nucleic Acids Res 2012; 40:7606-21. [PMID: 22661583 PMCID: PMC3439893 DOI: 10.1093/nar/gks500] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mitochondrial DNA (mtDNA) deletions are a primary cause of mitochondrial disease and are believed to contribute to the aging process and to various neurodegenerative diseases. Despite strong observational and experimental evidence, the molecular basis of the deletion process remains obscure. In this study, we test the hypothesis that the primary cause of mtDNA vulnerability to breakage resides in the formation of non-B DNA conformations, namely hairpin, cruciform and cloverleaf-like elements. Using the largest database of human mtDNA deletions built thus far (753 different cases), we show that site-specific breakage hotspots exist in the mtDNA. Furthermore, we discover that the most frequent deletion breakpoints occur within or near predicted structures, a result that is supported by data from transgenic mice with mitochondrial disease. There is also a significant association between the folding energy of an mtDNA region and the number of breakpoints that it harbours. In particular, two clusters of hairpins (near the D-loop 3′-terminus and the L-strand origin of replication) are hotspots for mtDNA breakage. Consistent with our hypothesis, the highest number of 5′- and 3′-breakpoints per base is found in the highly structured tRNA genes. Overall, the data presented in this study suggest that non-B DNA conformations are a key element of the mtDNA deletion process.
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Affiliation(s)
- Joana Damas
- Institute of Molecular Pathology and Immunology, University of Porto (IPATIMUP), Rua Dr Roberto Frias s/n, 4200-465 Porto, Portugal
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36
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R-loop formation is a distinctive characteristic of unmethylated human CpG island promoters. Mol Cell 2012; 45:814-25. [PMID: 22387027 DOI: 10.1016/j.molcel.2012.01.017] [Citation(s) in RCA: 588] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 12/08/2011] [Accepted: 01/10/2012] [Indexed: 12/31/2022]
Abstract
CpG islands (CGIs) function as promoters for approximately 60% of human genes. Most of these elements remain protected from CpG methylation, a prevalent epigenetic modification associated with transcriptional silencing. Here, we report that methylation-resistant CGI promoters are characterized by significant strand asymmetry in the distribution of guanines and cytosines (GC skew) immediately downstream from their transcription start sites. Using innovative genomics methodologies, we show that transcription through regions of GC skew leads to the formation of long R loop structures. Furthermore, we show that GC skew and R loop formation potential is correlated with and predictive of the unmethylated state of CGIs. Finally, we provide evidence that R loop formation protects from DNMT3B1, the primary de novo DNA methyltransferase in early development. Altogether, these results suggest that protection from DNA methylation is a built-in characteristic of the DNA sequence of CGI promoters that is revealed by the cotranscriptional formation of R loop structures.
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37
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Nakama M, Kawakami K, Kajitani T, Urano T, Murakami Y. DNA-RNA hybrid formation mediates RNAi-directed heterochromatin formation. Genes Cells 2012; 17:218-33. [PMID: 22280061 DOI: 10.1111/j.1365-2443.2012.01583.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Certain noncoding RNAs (ncRNAs) implicated in the regulation of chromatin structure associate with chromatin. During the formation of RNAi-directed heterochromatin in fission yeast, ncRNAs transcribed from heterochromatin are thought to recruit the RNAi machinery to chromatin for the formation of heterochromatin; however, the molecular details of this association are not clear. Here, using RNA immunoprecipitation assay, we showed that the heterochromatic ncRNA was associated with chromatin via the formation of a DNA-RNA hybrid and bound to the RNA-induced transcriptional silencing (RITS) complex. The presence of DNA-RNA hybrid in the cell was also confirmed by immunofluorescence analysis using anti-DNA-RNA hybrid antibody. Over-expression and depletion of RNase H in vivo decreased and increased the amount of DNA-RNA hybrid formed, respectively, and both disturbed heterochromatin. Moreover, DNA-RNA hybrid was formed on, and over-expression of RNase H inhibited the formation of, artificial heterochromatin induced by tethering of RITS to mRNA. These results indicate that heterochromatic ncRNAs are retained on chromatin via the formation of DNA-RNA hybrids and provide a platform for the RNAi-directed heterochromatin assembly and suggest that DNA-RNA hybrid formation plays a role in chromatic ncRNA function.
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Affiliation(s)
- Mina Nakama
- Laboratory of Cell Regulation and Molecular Network, Division of Systemic Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, Kyoto 606-8501, Japan
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38
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Kasiviswanathan R, Collins TRL, Copeland WC. The interface of transcription and DNA replication in the mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1819:970-8. [PMID: 22207204 DOI: 10.1016/j.bbagrm.2011.12.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2011] [Revised: 12/09/2011] [Accepted: 12/12/2011] [Indexed: 11/30/2022]
Abstract
DNA replication of the mitochondrial genome is unique in that replication is not primed by RNA derived from dedicated primases, but instead by extension of processed RNA transcripts laid down by the mitochondrial RNA polymerase. Thus, the RNA polymerase serves not only to generate the transcripts but also the primers needed for mitochondrial DNA replication. The interface between this transcription and DNA replication is not well understood but must be highly regulated and coordinated to carry out both mitochondrial DNA replication and transcription. This review focuses on the extension of RNA primers for DNA replication by the replication machinery and summarizes the current models of DNA replication in mitochondria as well as the proteins involved in mitochondrial DNA replication, namely, the DNA polymerase γ and its accessory subunit, the mitochondrial DNA helicase, the single-stranded DNA binding protein, topoisomerase I and IIIα and RNaseH1. This article is part of a Special Issue entitled: Mitochondrial Gene Expression.
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Affiliation(s)
- Rajesh Kasiviswanathan
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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39
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Helicase dissociation and annealing of RNA-DNA hybrids by Escherichia coli Cas3 protein. Biochem J 2011; 439:85-95. [PMID: 21699496 DOI: 10.1042/bj20110901] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
CRISPR (clustered regularly interspaced short palindromic repeat)/Cas (CRISPR-associated) is a nucleic acid processing system in bacteria and archaea that interacts with mobile genetic elements. CRISPR DNA and RNA sequences are processed by Cas proteins: in Escherichia coli K-12, one CRISPR locus links to eight cas genes (cas1, 2, 3 and casABCDE), whose protein products promote protection against phage. In the present paper, we report that purified E. coli Cas3 catalyses ATP-independent annealing of RNA with DNA forming R-loops, hybrids of RNA base-paired into duplex DNA. ATP abolishes Cas3 R-loop formation and instead powers Cas3 helicase unwinding of the invading RNA strand of a model R-loop substrate. R-loop formation by Cas3 requires magnesium as a co-factor and is inactivated by mutagenesis of a conserved amino acid motif. Cells expressing the mutant Cas3 protein are more sensitive to plaque formation by the phage λvir. A complex of CasABCDE ('Cascade') also promotes R-loop formation and we discuss possible overlapping roles of Cas3 and Cascade in E. coli, and the apparently antagonistic roles of Cas3 catalysing RNA-DNA annealing and ATP-dependent helicase unwinding.
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40
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Mileshina D, Koulintchenko M, Konstantinov Y, Dietrich A. Transfection of plant mitochondria and in organello gene integration. Nucleic Acids Res 2011; 39:e115. [PMID: 21715377 PMCID: PMC3177224 DOI: 10.1093/nar/gkr517] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Investigation and manipulation of mitochondrial genetics in animal and plant cells remains restricted by the lack of an efficient in vivo transformation methodology. Mitochondrial transfection in whole cells and maintenance of the transfected DNA are main issues on this track. We showed earlier that isolated mitochondria from different organisms can import DNA. Exploiting this mechanism, we assessed the possibility to maintain exogenous DNA in plant organelles. Whereas homologous recombination is scarce in the higher plant nuclear compartment, recombination between large repeats generates the multipartite structure of the plant mitochondrial genome. These processes are under strict surveillance to avoid extensive genomic rearrangements. Nevertheless, following transfection of isolated organelles with constructs composed of a partial gfp gene flanked by fragments of mitochondrial DNA, we demonstrated in organello homologous recombination of the imported DNA with the resident DNA and integration of the reporter gene. Recombination yielded insertion of a continuous exogenous DNA fragment including the gfp sequence and at least 0.5 kb of flanking sequence on each side. According to our observations, transfection constructs carrying multiple sequences homologous to the mitochondrial DNA should be suitable and targeting of most regions in the organelle genome should be feasible, making the approach of general interest.
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41
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Rorbach J, Nicholls TJJ, Minczuk M. PDE12 removes mitochondrial RNA poly(A) tails and controls translation in human mitochondria. Nucleic Acids Res 2011; 39:7750-63. [PMID: 21666256 PMCID: PMC3177208 DOI: 10.1093/nar/gkr470] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Polyadenylation of mRNA in human mitochondria is crucial for gene expression and perturbation of poly(A) tail length has been linked to a human neurodegenerative disease. Here we show that 2′-phosphodiesterase (2′-PDE), (hereafter PDE12), is a mitochondrial protein that specifically removes poly(A) extensions from mitochondrial mRNAs both in vitro and in mitochondria of cultured cells. In eukaryotes, poly(A) tails generally stabilize mature mRNAs, whereas in bacteria they increase mRNA turnover. In human mitochondria, the effects of increased PDE12 expression were transcript dependent. An excess of PDE12 led to an increase in the level of three mt-mRNAs (ND1, ND2 and CytB) and two (CO1 and CO2) were less abundant than in mitochondria of control cells and there was no appreciable effect on the steady-state level of the remainder of the mitochondrial transcripts. The alterations in poly(A) tail length accompanying elevated PDE12 expression were associated with severe inhibition of mitochondrial protein synthesis, and consequently respiratory incompetence. Therefore, we propose that mRNA poly(A) tails are important in regulating protein synthesis in human mitochondria, as it is the case for nuclear-encoded eukaryotic mRNA.
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Affiliation(s)
- Joanna Rorbach
- MRC Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Cambridge CB2 0XY, UK
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42
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Pohjoismäki JLO, Goffart S. Of circles, forks and humanity: Topological organisation and replication of mammalian mitochondrial DNA. Bioessays 2011; 33:290-9. [PMID: 21290399 DOI: 10.1002/bies.201000137] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The organisation of mammalian mitochondrial DNA (mtDNA) is more complex than usually assumed. Despite often being depicted as a simple circle, the topology of mtDNA can vary from supercoiled monomeric circles over catenanes and oligomers to complex multimeric networks. Replication of mtDNA is also not clear cut. Two different mechanisms of replication have been found in cultured cells and in most tissues: a strand-asynchronous mode involving temporary RNA coverage of one strand, and a strand-coupled mode rather resembling conventional nuclear DNA replication. In addition, a recombination-initiated replication mechanism is likely to be associated with the multimeric mtDNA networks found in human heart. Although an insight into the general principles and key factors of mtDNA organisation and maintenance has been gained over the last few years, there are many open questions regarding replication initiation, termination and physiological factors determining mtDNA organisation and replication mode. However, common themes in mtDNA maintenance across eukaryotic kingdoms can provide valuable lessons for future work.
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Affiliation(s)
- Jaakko L O Pohjoismäki
- Department of Cardiac Development and Remodelling, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany.
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43
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Mitochondrial DNA replication and disease: insights from DNA polymerase γ mutations. Cell Mol Life Sci 2010; 68:219-33. [PMID: 20927567 DOI: 10.1007/s00018-010-0530-4] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 08/31/2010] [Accepted: 09/02/2010] [Indexed: 10/19/2022]
Abstract
DNA polymerase γ (pol γ), encoded by POLG, is responsible for replicating human mitochondrial DNA. About 150 mutations in the human POLG have been identified in patients with mitochondrial diseases such as Alpers syndrome, progressive external ophthalmoplegia, and ataxia-neuropathy syndromes. Because many of the mutations are described in single citations with no genotypic family history, it is important to ascertain which mutations cause or contribute to mitochondrial disease. The vast majority of data about POLG mutations has been generated from biochemical characterizations of recombinant pol γ. However, recently, the study of mitochondrial dysfunction in Saccharomyces cerevisiae and mouse models provides important in vivo evidence for the role of POLG mutations in disease. Also, the published 3D-structure of the human pol γ assists in explaining some of the biochemical and genetic properties of the mutants. This review summarizes the current evidence that identifies and explains disease-causing POLG mutations.
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Freyer C, Park CB, Ekstrand MI, Shi Y, Khvorostova J, Wibom R, Falkenberg M, Gustafsson CM, Larsson NG. Maintenance of respiratory chain function in mouse hearts with severely impaired mtDNA transcription. Nucleic Acids Res 2010; 38:6577-88. [PMID: 20566479 PMCID: PMC2965244 DOI: 10.1093/nar/gkq527] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The basal mitochondrial transcription machinery is essential for biogenesis of the respiratory chain and consists of mitochondrial RNA polymerase, mitochondrial transcription factor A (TFAM) and mitochondrial transcription factor B2. This triad of proteins is sufficient and necessary for mtDNA transcription initiation. Abolished mtDNA transcription caused by tissue-specific knockout of TFAM in the mouse heart leads to early onset of a severe mitochondrial cardiomyopathy with lethality within the first post-natal weeks. Here, we describe a mouse model expressing human TFAM instead of the endogenous mouse TFAM in heart. These rescue mice have severe reduction in mtDNA transcription initiation, but, surprisingly, are healthy at the age of 52 weeks with near-normal steady-state levels of transcripts. In addition, we demonstrate that heavy-strand mtDNA transcription normally terminates at the termination-associated sequence in the control region. This termination is abolished in rescue animals resulting in heavy (H)-strand transcription of the entire control region. In conclusion, we demonstrate here the existence of an unexpected mtDNA transcript stabilization mechanism that almost completely compensates for the severely reduced transcription initiation in rescue hearts. Future elucidation of the underlying molecular mechanism may provide a novel pathway to treat mitochondrial dysfunction in human pathology.
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Affiliation(s)
- Christoph Freyer
- Department of Laboratory Medicine, Karolinska Institutet, Retzius väg 8, 171 65 Solna, Sweden
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45
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Lubitz I, Zikich D, Kotlyar A. Specific high-affinity binding of thiazole orange to triplex and G-quadruplex DNA. Biochemistry 2010; 49:3567-74. [PMID: 20329708 DOI: 10.1021/bi1000849] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Interaction of Thiazole Orange (TO) with double-, triple-, and quadruple-stranded forms of DNA was studied. We have demonstrated by UV-vis absorption, circular dichroism (CD), and fluorescence spectroscopy that TO binds with much higher affinity to triplex and G-quadruplex DNA structures compared to double-stranded (ds) DNA. Complexes of the dye with DNA triplexes and G-quadruplexes are very stable and do not dissociate during chromatography and gel electrophoresis. TO binding to either triple- or quadruple-stranded DNA structures results in a >1000-fold increase in dye fluorescence. The fluorescence titration data showed that TO to triad and tetrad ratios, in tight complexes with the triplex and the G-quadruplex, are equal to 0.5 and 1, respectively. Preferential binding of TO to triplexes and G-quadruplexes enables selective detection of only these DNA forms in gels in the absence of free TO in electrophoresis running buffer. We have also demonstrated that incubation of U2OS cells with submicromolar concentrations of TO results in preferential staining of certain areas in the nucleus in contrast to DAPI which binds to dsDNA and efficiently stains regions that are unstained with TO. We suggest that TO staining may be useful for the detection of noncanonical structural motifs in genomic DNA.
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Affiliation(s)
- Irit Lubitz
- Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, 69978 Israel
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46
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Wanrooij S, Falkenberg M. The human mitochondrial replication fork in health and disease. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1378-88. [PMID: 20417176 DOI: 10.1016/j.bbabio.2010.04.015] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 04/13/2010] [Accepted: 04/15/2010] [Indexed: 11/16/2022]
Abstract
Mitochondria are organelles whose main function is to generate power by oxidative phosphorylation. Some of the essential genes required for this energy production are encoded by the mitochondrial genome, a small circular double stranded DNA molecule. Human mtDNA is replicated by a specialized machinery distinct from the nuclear replisome. Defects in the mitochondrial replication machinery can lead to loss of genetic information by deletion and/or depletion of the mtDNA, which subsequently may cause disturbed oxidative phosphorylation and neuromuscular symptoms in patients. We discuss here the different components of the mitochondrial replication machinery and their role in disease. We also review the mode of mammalian mtDNA replication.
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Affiliation(s)
- Sjoerd Wanrooij
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-40530 Gothenburg, Sweden.
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47
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Fusté JM, Wanrooij S, Jemt E, Granycome CE, Cluett TJ, Shi Y, Atanassova N, Holt IJ, Gustafsson CM, Falkenberg M. Mitochondrial RNA polymerase is needed for activation of the origin of light-strand DNA replication. Mol Cell 2010; 37:67-78. [PMID: 20129056 DOI: 10.1016/j.molcel.2009.12.021] [Citation(s) in RCA: 148] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 07/21/2009] [Accepted: 10/14/2009] [Indexed: 11/19/2022]
Abstract
Mitochondrial DNA is replicated by a unique enzymatic machinery, which is distinct from the replication apparatus used for copying the nuclear genome. We examine here the mechanisms of origin-specific initiation of lagging-strand DNA synthesis in human mitochondria. We demonstrate that the mitochondrial RNA polymerase (POLRMT) is the primase required for initiation of DNA synthesis from the light-strand origin of DNA replication (OriL). Using only purified POLRMT and DNA replication factors, we can faithfully reconstitute OriL-dependent initiation in vitro. Leading-strand DNA synthesis is initiated from the heavy-strand origin of DNA replication and passes OriL. The single-stranded OriL is exposed and adopts a stem-loop structure. At this stage, POLRMT initiates primer synthesis from a poly-dT stretch in the single-stranded loop region. After about 25 nt, POLRMT is replaced by DNA polymerase gamma, and DNA synthesis commences. Our findings demonstrate that POLRMT can function as an origin-specific primase in mammalian mitochondria.
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Affiliation(s)
- Javier Miralles Fusté
- Division of Metabolic Diseases, Karolinska Institutet, Novum, SE-141 86 Stockholm, Sweden
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48
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Mammalian mitochondrial DNA replication intermediates are essentially duplex but contain extensive tracts of RNA/DNA hybrid. J Mol Biol 2010; 397:1144-55. [PMID: 20184890 DOI: 10.1016/j.jmb.2010.02.029] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Revised: 02/11/2010] [Accepted: 02/16/2010] [Indexed: 11/21/2022]
Abstract
We demonstrate, using transmission electron microscopy and immunopurification with an antibody specific for RNA/DNA hybrid, that intact mitochondrial DNA replication intermediates are essentially duplex throughout their length but contain extensive RNA tracts on one strand. However, the extent of preservation of RNA in such molecules is highly dependent on the preparative method used. These findings strongly support the strand-coupled model of mitochondrial DNA replication involving RNA incorporation throughout the lagging strand.
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49
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Shaban NM, Harvey S, Perrino FW, Hollis T. The structure of the mammalian RNase H2 complex provides insight into RNA.NA hybrid processing to prevent immune dysfunction. J Biol Chem 2009; 285:3617-3624. [PMID: 19923215 DOI: 10.1074/jbc.m109.059048] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The mammalian RNase H2 ribonuclease complex has a critical function in nucleic acid metabolism to prevent immune activation with likely roles in processing of RNA primers in Okazaki fragments during DNA replication, in removing ribonucleotides misinserted by DNA polymerases, and in eliminating RNA.DNA hybrids during cell death. Mammalian RNase H2 is a heterotrimeric complex of the RNase H2A, RNase H2B, and RNase H2C proteins that are all required for proper function and activity. Mutations in the human RNase H2 genes cause Aicardi-Goutières syndrome. We have determined the crystal structure of the three-protein mouse RNase H2 enzyme complex to better understand the molecular basis of RNase H2 dysfunction in human autoimmunity. The structure reveals the intimately interwoven architecture of RNase H2B and RNase H2C that interface with RNase H2A in a complex ideally suited for nucleic acid binding and hydrolysis coupled to protein-protein interaction motifs that could allow for efficient participation in multiple cellular functions. We have identified four conserved acidic residues in the active site that are necessary for activity and suggest a two-metal ion mechanism of catalysis for RNase H2. An Okazaki fragment has been modeled into the RNase H2 nucleic acid binding site providing insight into the recognition of RNA.DNA junctions by the RNase H2. Further structural and biochemical analyses show that some RNase H2 disease-causing mutations likely result in aberrant protein-protein interactions while the RNase H2A subunit-G37S mutation appears to distort the active site accounting for the demonstrated substrate specificity modification.
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Affiliation(s)
- Nadine M Shaban
- From the Department of Biochemistry, Center for Structural Biology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157
| | - Scott Harvey
- From the Department of Biochemistry, Center for Structural Biology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157
| | - Fred W Perrino
- From the Department of Biochemistry, Center for Structural Biology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157
| | - Thomas Hollis
- From the Department of Biochemistry, Center for Structural Biology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157.
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50
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Neaves KJ, Huppert JL, Henderson RM, Edwardson JM. Direct visualization of G-quadruplexes in DNA using atomic force microscopy. Nucleic Acids Res 2009; 37:6269-75. [PMID: 19696072 PMCID: PMC2764456 DOI: 10.1093/nar/gkp679] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Revised: 07/14/2009] [Accepted: 08/01/2009] [Indexed: 12/11/2022] Open
Abstract
The formation of G-quadruplexes in G-rich regions of DNA is believed to affect DNA transcription and replication. However, it is currently unclear how this formation occurs in the presence of a complementary strand. We have used atomic force microscopy (AFM) to image stable RNA/DNA hybrid loops generated by transcription of the plasmid pPH600, which contains a 604-bp fragment of the murine immunoglobulin Sgamma3 switch region. We show that the non-RNA-containing portion folds into G-quadruplexes, consistent with computational predictions. We also show that hybrid formation prevents further transcription from occurring, implying a regulatory role. After in vitro transcription, almost all (93%) of the plasmids had an asymmetric loop, a large asymmetric blob or a spur-like projection at the appropriate position on the DNA contour. The loops disappeared following treatment of the transcribed plasmid with RNase H, which removes mRNA hybridized with the template strand. Replacement of K+ in the transcription buffer with either Na+ or Li+ caused a reduction in the percentage of plasmids containing loops, blobs or spurs, consistent with the known effects of monovalent cations on G-quadruplex stability. The minimal sample preparation required for AFM imaging has permitted direct observation of the structural changes resulting from G-quadruplex formation.
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Affiliation(s)
- Kelly J. Neaves
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD and Physics of Medicine, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - Julian L. Huppert
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD and Physics of Medicine, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - Robert M. Henderson
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD and Physics of Medicine, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - J. Michael Edwardson
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD and Physics of Medicine, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
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