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Fragkoulis G, Hangas A, Fekete Z, Michell C, Moraes C, Willcox S, Griffith JD, Goffart S, Pohjoismäki JO. Linear DNA-driven recombination in mammalian mitochondria. Nucleic Acids Res 2024; 52:3088-3105. [PMID: 38300793 PMCID: PMC11014290 DOI: 10.1093/nar/gkae040] [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: 02/01/2023] [Accepted: 01/11/2024] [Indexed: 02/03/2024] Open
Abstract
Mitochondrial DNA (mtDNA) recombination in animals has remained enigmatic due to its uniparental inheritance and subsequent homoplasmic state, which excludes the biological need for genetic recombination, as well as limits tools to study it. However, molecular recombination is an important genome maintenance mechanism for all organisms, most notably being required for double-strand break repair. To demonstrate the existence of mtDNA recombination, we took advantage of a cell model with two different types of mitochondrial genomes and impaired its ability to degrade broken mtDNA. The resulting excess of linear DNA fragments caused increased formation of cruciform mtDNA, appearance of heterodimeric mtDNA complexes and recombinant mtDNA genomes, detectable by Southern blot and by long range PacBio® HiFi sequencing approach. Besides utilizing different electrophoretic methods, we also directly observed molecular complexes between different mtDNA haplotypes and recombination intermediates using transmission electron microscopy. We propose that the known copy-choice recombination by mitochondrial replisome could be sufficient for the needs of the small genome, thus removing the requirement for a specialized mitochondrial recombinase. The error-proneness of this system is likely to contribute to the formation of pathological mtDNA rearrangements.
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Affiliation(s)
- Georgios Fragkoulis
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Anu Hangas
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Zsófia Fekete
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
- Department of Genetics and Genomics, Institute of Genetics and Biotechnology, Hungarian University of Agriculture and Life Sciences, Gödöllő, Hungary
- Doctoral School of Animal Biotechnology and Animal Science, Hungarian University of Agriculture and Life Sciences, Gödöllő, Hungary
| | - Craig Michell
- Red Sea Research Center, Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Carlos T Moraes
- Department of Neurology, University of Miami Miller School of Medicine, Miami,FL, USA
| | - Smaranda Willcox
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, USA
| | - Jack D Griffith
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, USA
| | - Steffi Goffart
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Jaakko L O Pohjoismäki
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
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2
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Sillamaa S, Piljukov VJ, Vaask I, Sedman T, Jõers P, Sedman J. UvrD-like helicase Hmi1 Has an ATP independent role in yeast mitochondrial DNA maintenance. DNA Repair (Amst) 2023; 132:103582. [PMID: 37839213 DOI: 10.1016/j.dnarep.2023.103582] [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: 07/07/2023] [Revised: 09/28/2023] [Accepted: 10/03/2023] [Indexed: 10/17/2023]
Abstract
Hmi1 is a UvrD-like DNA helicase required for the maintenance of the yeast Saccharomyces cerevisiae mitochondrial DNA (mtDNA). Deletion of the HMI1 ORF leads to the formation of respiration-deficient petite mutants, which either contain a short fragment of mtDNA arranged in tandem repeats or lack mtDNA completely. Here we characterize point mutants of the helicase designed to target the ATPase or ssDNA binding activity and show that these mutations do not separately lead to complete loss of the Hmi1 function. The mutant strains support ATP production via oxidative phosphorylation and enable us to directly analyze the impact of both activities on the stability of wild-type mtDNA in this petite-positive yeast. Our data reveal that Hmi1 mutants affecting ssDNA binding display a stronger defect in the maintenance of mtDNA compared to the mutants of ATP binding/hydrolysis. Hmi1 mutants impaired in ssDNA binding demonstrate sensitivity to UV irradiation and lower levels of Cox2 encoded by the mitochondrial genome. This suggests a complex and multifarious role for Hmi1 in mtDNA maintenance-linked transactions, some of which do not require the ATP-dependent helicase activity.
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Affiliation(s)
- Sirelin Sillamaa
- Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia
| | - Vlad-Julian Piljukov
- Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia
| | - Iris Vaask
- Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia
| | - Tiina Sedman
- Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia
| | - Priit Jõers
- Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia
| | - Juhan Sedman
- Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia.
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3
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Fontana GA, Gahlon HL. Detection of UV-Induced Deletions in Mitochondrial DNA. Methods Mol Biol 2023; 2615:281-292. [PMID: 36807799 DOI: 10.1007/978-1-0716-2922-2_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Mitochondrial DNA (mtDNA) mutations are found in several human pathologies and are associated with aging. Deletion mutations in mtDNA result in the loss of essential genes for mitochondrial function. Over 250 deletion mutations have been reported and the common deletion is the most frequent mtDNA deletion linked to disease. This deletion removes 4977 base pairs of mtDNA. It has previously been shown that exposure to UVA radiation can promote the formation of the common deletion. Furthermore, aberrations in mtDNA replication and repair are associated with formation of the common deletion. However, molecular mechanisms describing the formation of this deletion are poorly characterized. This chapter describes a method to irradiate human skin fibroblasts with physiological doses of UVA and the subsequent detection of the common deletion by quantitative PCR analysis.
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Affiliation(s)
- Gabriele A Fontana
- Department of Health Sciences and Technology, ETH Zurich, Zurich, Switzerland
| | - Hailey L Gahlon
- Department of Health Sciences and Technology, ETH Zurich, Zurich, Switzerland.
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4
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De Santis I, Zanoni M, Pignatta S, Longobardi P, Tesei A, Bevilacqua A. Pro-inflammatory RNA:DNA Hybrids Are p53 Independently Boosted by Hyperbaric Oxygen: a Subcellular Distribution Analysis by Automated Quantitative Imaging. Mol Imaging Biol 2022; 25:504-512. [PMID: 36261778 PMCID: PMC10172224 DOI: 10.1007/s11307-022-01778-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 09/29/2022] [Accepted: 10/03/2022] [Indexed: 11/24/2022]
Abstract
PURPOSE RNA:DNA hybrids are co-transcriptional products with acknowledged cytoplasmic pro-inflammatory role as activators of the cGAS-STING pathway. We recently proved them also as radiation-induced senescence messages for the abscopal effect mediation, demonstrating the need for a functional p53 for their production and release in A549 and H1299 tumour cells. However, little is known about their role under different stress conditions, especially in cancer cells. METHODS In this work, we open the investigation making use of automated quantitative imaging to characterize the hybrid subcellular distribution in HeLa cells grown under different oxygen pressures or exposed to different ionizing radiation doses. After cell imaging by confocal fluorescent microscopy, we apply automated imaging methods developed on purpose to quantify hybrid foci and nuclear cluster intensity, regional and local density and dimension. RESULTS We show that alteration of culture oxygenation increases hybrid cytoplasmic presence, especially when caused by an hyperoxic environment, with evident hybrid gathering at the cell membrane. Ionizing radiations always fail to increase hybrids, in accordance with the absence of functional p53 in HeLa cells. However, dose-dependent effects are still evident and suggest a threshold dose of 7.5 Gy for remarkable hybrid reduction. CONCLUSION Together with our previous results, these data demonstrate for the first time that different types of stress can increase hybrid production in cancer cells and by at least two different pathways, one p53-dependent triggerable by ionizing radiations and one p53-independent triggerable by oxidative stress. Together, our findings provide a starting point for understanding hybrid role in tumour stress response.
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Affiliation(s)
- Ilaria De Santis
- Interdepartmental Centre Alma Mater Research Institute on Global Challenges and Climate Change (Alma Climate), University of Bologna, I-40126, Bologna, Italy
| | - Michele Zanoni
- Biosciences Laboratory, IRCCS Istituto Romagnolo per lo Studio dei Tumori (IRST) "Dino Amadori", I-47014, Meldola, Italy
| | - Sara Pignatta
- Biosciences Laboratory, IRCCS Istituto Romagnolo per lo Studio dei Tumori (IRST) "Dino Amadori", I-47014, Meldola, Italy
| | | | - Anna Tesei
- Biosciences Laboratory, IRCCS Istituto Romagnolo per lo Studio dei Tumori (IRST) "Dino Amadori", I-47014, Meldola, Italy.
| | - Alessandro Bevilacqua
- Advanced Research Center on Electronic Systems (ARCES) for Information and Communication Technologies "E. De Castro", University of Bologna, I-40125, Bologna, Italy.
- Department of Computer Science and Engineering (DISI), University of Bologna, I-40136, Bologna, Italy.
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5
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Bowater RP, Bohálová N, Brázda V. Interaction of Proteins with Inverted Repeats and Cruciform Structures in Nucleic Acids. Int J Mol Sci 2022; 23:ijms23116171. [PMID: 35682854 PMCID: PMC9180970 DOI: 10.3390/ijms23116171] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 05/26/2022] [Accepted: 05/30/2022] [Indexed: 01/27/2023] Open
Abstract
Cruciforms occur when inverted repeat sequences in double-stranded DNA adopt intra-strand hairpins on opposing strands. Biophysical and molecular studies of these structures confirm their characterization as four-way junctions and have demonstrated that several factors influence their stability, including overall chromatin structure and DNA supercoiling. Here, we review our understanding of processes that influence the formation and stability of cruciforms in genomes, covering the range of sequences shown to have biological significance. It is challenging to accurately sequence repetitive DNA sequences, but recent advances in sequencing methods have deepened understanding about the amounts of inverted repeats in genomes from all forms of life. We highlight that, in the majority of genomes, inverted repeats are present in higher numbers than is expected from a random occurrence. It is, therefore, becoming clear that inverted repeats play important roles in regulating many aspects of DNA metabolism, including replication, gene expression, and recombination. Cruciforms are targets for many architectural and regulatory proteins, including topoisomerases, p53, Rif1, and others. Notably, some of these proteins can induce the formation of cruciform structures when they bind to DNA. Inverted repeat sequences also influence the evolution of genomes, and growing evidence highlights their significance in several human diseases, suggesting that the inverted repeat sequences and/or DNA cruciforms could be useful therapeutic targets in some cases.
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Affiliation(s)
- Richard P. Bowater
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK;
| | - Natália Bohálová
- Department of Biophysical Chemistry and Molecular Oncology, Institute of Biophysics of the Czech Academy of Sciences, 61265 Brno, Czech Republic;
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
| | - Václav Brázda
- Department of Biophysical Chemistry and Molecular Oncology, Institute of Biophysics of the Czech Academy of Sciences, 61265 Brno, Czech Republic;
- Correspondence:
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6
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Carvalho G, Repolês BM, Mendes I, Wanrooij PH. Mitochondrial DNA Instability in Mammalian Cells. Antioxid Redox Signal 2022; 36:885-905. [PMID: 34015960 PMCID: PMC9127837 DOI: 10.1089/ars.2021.0091] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 05/11/2021] [Indexed: 02/06/2023]
Abstract
Significance: The small, multicopy mitochondrial genome (mitochondrial DNA [mtDNA]) is essential for efficient energy production, as alterations in its coding information or a decrease in its copy number disrupt mitochondrial ATP synthesis. However, the mitochondrial replication machinery encounters numerous challenges that may limit its ability to duplicate this important genome and that jeopardize mtDNA stability, including various lesions in the DNA template, topological stress, and an insufficient nucleotide supply. Recent Advances: An ever-growing array of DNA repair or maintenance factors are being reported to localize to the mitochondria. We review current knowledge regarding the mitochondrial factors that may contribute to the tolerance or repair of various types of changes in the mitochondrial genome, such as base damage, incorporated ribonucleotides, and strand breaks. We also discuss the newly discovered link between mtDNA instability and activation of the innate immune response. Critical Issues: By which mechanisms do mitochondria respond to challenges that threaten mtDNA maintenance? What types of mtDNA damage are repaired, and when are the affected molecules degraded instead? And, finally, which forms of mtDNA instability trigger an immune response, and how? Future Directions: Further work is required to understand the contribution of the DNA repair and damage-tolerance factors present in the mitochondrial compartment, as well as the balance between mtDNA repair and degradation. Finally, efforts to understand the events underlying mtDNA release into the cytosol are warranted. Pursuing these and many related avenues can improve our understanding of what goes wrong in mitochondrial disease. Antioxid. Redox Signal. 36, 885-905.
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Affiliation(s)
- Gustavo Carvalho
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Bruno Marçal Repolês
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Isabela Mendes
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Paulina H. Wanrooij
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
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7
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Kuthethur R, Shukla V, Mallya S, Adiga D, Kabekkodu SP, Ramachandra L, Saxena Pu P, Satyamoorthy K, Chakrabarty S. Expression analysis and function of mitochondrial genome-encoded microRNAs. J Cell Sci 2022; 135:274749. [PMID: 35297485 DOI: 10.1242/jcs.258937] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 03/11/2022] [Indexed: 11/20/2022] Open
Abstract
MicroRNAs play a significant role in nuclear and mitochondrial anterograde and retrograde signaling. Most of the miRNAs found inside mitochondria are nuclear genome encoded, with few mitochondrial genome encoded non-coding RNAs have been reported. In this study, we have identified 13 mitochondrial genome-encoded microRNAs (mitomiRs), which were differentially expressed in breast cancer cell lines (MCF-7, MDA-MB-468, and MDA-MB-231), non-malignant breast epithelial cell line (MCF-10A), and normal and breast cancer tissue specimens. We found that mitochondrial DNA depletion and inhibition of mitochondrial transcription leads to reduced expression of mitomiRs in breast cancer cells. MitomiRs physically interact with Ago2, an RNA-induced silencing complex (RISC) protein, in the cytoplasm and inside mitochondria. MitomiRs regulate the expression of both nuclear and mitochondrial transcripts in breast cancer cells. We showed that mitomiR-5 targets PPARGC1A and regulates mtDNA copy number in breast cancer cells. MitomiRs identified in the present study may be a promising tool for expression and functional analysis in patients with a defective mitochondrial phenotype, including cancer and metabolic syndromes.
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Affiliation(s)
- Raviprasad Kuthethur
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Vaibhav Shukla
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Sandeep Mallya
- Department of Bioinformatics, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Divya Adiga
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Shama Prasada Kabekkodu
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Lingadakai Ramachandra
- Department of Surgery, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Prakash Saxena Pu
- Department of Radiation Oncology, Kasturba Medical College, Manipal Academy of Higher Education, Mangalore, Karnataka, India
| | - Kapaettu Satyamoorthy
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Sanjiban Chakrabarty
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, India
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8
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Guo Y, Tsai HI, Zhang L, Zhu H. Mitochondrial DNA on Tumor-Associated Macrophages Polarization and Immunity. Cancers (Basel) 2022; 14:1452. [PMID: 35326602 PMCID: PMC8946090 DOI: 10.3390/cancers14061452] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 02/26/2022] [Accepted: 03/09/2022] [Indexed: 12/04/2022] Open
Abstract
As the richest immune cells in most tumor microenvironments (TMEs), tumor-associated macrophages (TAMs) play an important role in tumor development and treatment sensitivity. The phenotypes and functions of TAMs vary according to their sources and tumor progression. Different TAM phenotypes display distinct behaviors in terms of tumor immunity and are regulated by intracellular and exogenous molecules. Additionally, dysfunctional and oxidatively stressed mitochondrial-derived mitochondrial DNA (mtDNA) plays an important role in remodeling the phenotypes and functions of TAMs. This article reviews the interactions between mtDNA and TAMs in the TME and further discusses the influence of their performance on tumor genesis and development.
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Affiliation(s)
- Yaxin Guo
- Department of Medical Imaging, The Affiliated Hospital of Jiangsu University, Zhenjiang 212001, China;
| | - Hsiang-i Tsai
- Laboratory of Radiology, The Affiliated Hospital of Jiangsu University, Zhenjiang 212001, China;
| | - Lirong Zhang
- Department of Medical Imaging, The Affiliated Hospital of Jiangsu University, Zhenjiang 212001, China;
| | - Haitao Zhu
- Department of Medical Imaging, The Affiliated Hospital of Jiangsu University, Zhenjiang 212001, China;
- Laboratory of Radiology, The Affiliated Hospital of Jiangsu University, Zhenjiang 212001, China;
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9
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Huo H, He Y, Chen W, Wu L, Yi X, Wang J. Simultaneously monitoring UVC-induced DNA damage and photoenzymatic repair of cyclobutane pyrimidine dimers by electrochemical impedance spectroscopy. Talanta 2021; 239:123081. [PMID: 34823862 DOI: 10.1016/j.talanta.2021.123081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 11/13/2021] [Accepted: 11/17/2021] [Indexed: 10/19/2022]
Abstract
Cyclobutane pyrimidine dimers (CPDs) are the major DNA photoproducts of thymine-thymine dinucleotides upon ultraviolet (UV) irradiation. Failure in the repair of damaged DNA may lead to DNA replication errors, DNA mutations, and even cell death. Photoreactivation can mediate the repair of UV-induced DNA lesions by photolyases upon UVA (315-400 nm) or blue light (400-500 nm) irradiation. Herein, the UVC (254 nm)-induced DNA damage and photoenzymatic repair of the CPD products were simultaneously monitored by electrochemical impedance spectroscopy (EIS). The UVC-damaged dT20 was first immobilized on the gold electrode, and the specific recognition by the anti-CPD antibody leads to significantly increased EIS signals. The electron transfer resistance (Ret) values were linearly proportional to the concentrations of damaged dT20 ranging from 0.005 to 0.1 μM, and a detection limit of 3.06 nM was achieved. Using surface plasmon resonance, the equilibrium dissociation constant (KD) between the CPDs in dT20 and anti-CPD antibody was estimated to be (3.32 ± 0.31) × 10-12 M, indicating the strong binding affinity. Evidenced by EIS, the CPDs in the damaged dT20 could be repaired by the attached DNA photolyase under UVA (365 nm) photoexcitation, and the detachment of the photolyase from the DNA strand was accomplished after completion of the repair process. The repair efficiency was calculated to be 70.0% by EIS, being consistent with that of 71.4% by UV spectroscopy. The electrochemical method is simple, sensitive and straightforward, holding great potential for assaying other types of DNA lesions and their repair processes.
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Affiliation(s)
- Huan Huo
- Hunan Provincial Key Laboratory of Micro & Nano Materials Interface Science, College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, PR China
| | - Yuhan He
- Hunan Provincial Key Laboratory of Micro & Nano Materials Interface Science, College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, PR China
| | - Wenchao Chen
- Hunan Provincial Key Laboratory of Micro & Nano Materials Interface Science, College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, PR China
| | - Ling Wu
- Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation, School of Chemistry and Biological Engineering, Changsha University of Science and Technology, Changsha, Hunan, 410004, PR China
| | - Xinyao Yi
- Hunan Provincial Key Laboratory of Micro & Nano Materials Interface Science, College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, PR China.
| | - Jianxiu Wang
- Hunan Provincial Key Laboratory of Micro & Nano Materials Interface Science, College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, PR China.
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10
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Emerging methods for and novel insights gained by absolute quantification of mitochondrial DNA copy number and its clinical applications. Pharmacol Ther 2021; 232:107995. [PMID: 34592204 DOI: 10.1016/j.pharmthera.2021.107995] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 08/26/2021] [Accepted: 09/01/2021] [Indexed: 02/07/2023]
Abstract
The past thirty years have seen a surge in interest in pathophysiological roles of mitochondria, and the accurate quantification of mitochondrial DNA copy number (mCN) in cells and tissue samples is a fundamental aspect of assessing changes in mitochondrial health and biogenesis. Quantification of mCN between studies is surprisingly variable due to a combination of physiological variability and diverse protocols being used to measure this endpoint. The advent of novel methods to quantify nucleic acids like digital polymerase chain reaction (dPCR) and high throughput sequencing offer the ability to measure absolute values of mCN. We conducted an in-depth survey of articles published between 1969 -- 2020 to create an overview of mCN values, to assess consensus values of tissue-specific mCN, and to evaluate consistency between methods of assessing mCN. We identify best practices for methods used to assess mCN, and we address the impact of using specific loci on the mitochondrial genome to determine mCN. Current data suggest that clinical measurement of mCN can provide diagnostic and prognostic value in a range of diseases and health conditions, with emphasis on cancer and cardiovascular disease, and the advent of means to measure absolute mCN should improve future clinical applications of mCN measurements.
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11
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Human PrimPol Discrimination against Dideoxynucleotides during Primer Synthesis. Genes (Basel) 2021; 12:genes12101487. [PMID: 34680882 PMCID: PMC8535229 DOI: 10.3390/genes12101487] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 09/17/2021] [Accepted: 09/22/2021] [Indexed: 12/02/2022] Open
Abstract
PrimPol is required to re-prime DNA replication at both nucleus and mitochondria, thus facilitating fork progression during replicative stress. ddC is a chain-terminating nucleotide that has been widely used to block mitochondrial DNA replication because it is efficiently incorporated by the replicative polymerase Polγ. Here, we show that human PrimPol discriminates against dideoxynucleotides (ddNTP) when elongating a primer across 8oxoG lesions in the template, but also when starting de novo synthesis of DNA primers, and especially when selecting the 3′nucleotide of the initial dimer. PrimPol incorporates ddNTPs with a very low efficiency compared to dNTPs even in the presence of activating manganese ions, and only a 40-fold excess of ddNTP would significantly disturb PrimPol primase activity. This discrimination against ddNTPs prevents premature termination of the primers, warranting their use for elongation. The crystal structure of human PrimPol highlights Arg291 residue as responsible for the strong dNTP/ddNTP selectivity, since it interacts with the 3′-OH group of the incoming deoxynucleotide, absent in ddNTPs. Arg291, shown here to be critical for both primase and polymerase activities of human PrimPol, would contribute to the preferred binding of dNTPs versus ddNTPs at the 3′elongation site, thus avoiding synthesis of abortive primers.
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12
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Kam JH, Hogg C, Fosbury R, Shinhmar H, Jeffery G. Mitochondria are specifically vulnerable to 420nm light in drosophila which undermines their function and is associated with reduced fly mobility. PLoS One 2021; 16:e0257149. [PMID: 34478469 PMCID: PMC8415596 DOI: 10.1371/journal.pone.0257149] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 08/24/2021] [Indexed: 01/05/2023] Open
Abstract
Increased blue light exposure has become a matter of concern as it has a range of detrimental effects, but the mechanisms remain unclear. Mitochondria absorb short wavelength light but have a specific absorbance at 420nm at the lower end of the human visual range. This 420nm absorption is probably due to the presence of porphyrin. We examine the impact of 420nm exposure on drosophila melanogaster mitochondria and its impact on fly mobility. Daily 15 mins exposures for a week significantly reduced mitochondrial complex activities and increased mitochondrial inner membrane permeability, which is a key metric of mitochondrial health. Adenosine triphosphate (ATP) levels were not significantly reduced and mobility was unchanged. There are multiple options for energy/time exposure combinations, but we then applied single 420nm exposure of 3h to increase the probability of an effect on ATP and mobility, and both were significantly reduced. ATP and mitochondrial membrane permeability recovered and over corrected at 72h post exposure. However, despite this, normal mobility did not return. Hence, the effect of short wavelengths on mitochondrial function is to reduce complex activity and increasing membrane permeability, but light exposure to reduce ATP and to translate into reduced mobility needs to be sustained.
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Affiliation(s)
- Jaimie Hoh Kam
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Chris Hogg
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Robert Fosbury
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Harpreet Shinhmar
- Institute of Ophthalmology, University College London, London, United Kingdom
| | - Glen Jeffery
- Institute of Ophthalmology, University College London, London, United Kingdom
- * E-mail:
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13
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The Type and Source of Reactive Oxygen Species Influences the Outcome of Oxidative Stress in Cultured Cells. Cells 2021; 10:cells10051075. [PMID: 33946545 PMCID: PMC8147180 DOI: 10.3390/cells10051075] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 04/26/2021] [Accepted: 04/28/2021] [Indexed: 01/21/2023] Open
Abstract
Oxidative stress can be modeled using various different experimental approaches, such as exposing the cells or organisms to oxidative chemicals. However, the actual effects of these chemicals, outside of the immediate measured effect, have attracted relatively little attention. We show here that three commonly used oxidants, menadione, potassium bromate, and hydrogen peroxide, while known to function differently, also elicit different types of responses in HEK293T cells. Menadione and bromate exposure mainly trigger an integrated stress response, whereas hydrogen peroxide affects cellular processes more diversely. Interestingly, acute oxidative stress does not universally cause notable induction of DNA repair or antioxidant defense mechanisms. We also provide evidence that cells with previous experience of oxidative stress show adaptive changes in their responses when the stress is renewed. Our results urge caution when comparing studies where different sources of oxidative stress have been used or when generalizing the findings of these studies to other oxidant types or tissues.
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14
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Kciuk M, Marciniak B, Mojzych M, Kontek R. Focus on UV-Induced DNA Damage and Repair-Disease Relevance and Protective Strategies. Int J Mol Sci 2020; 21:ijms21197264. [PMID: 33019598 PMCID: PMC7582305 DOI: 10.3390/ijms21197264] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/28/2020] [Accepted: 09/29/2020] [Indexed: 02/06/2023] Open
Abstract
The protective ozone layer is continually depleting due to the release of deteriorating environmental pollutants. The diminished ozone layer contributes to excessive exposure of cells to ultraviolet (UV) radiation. This leads to various cellular responses utilized to restore the homeostasis of exposed cells. DNA is the primary chromophore of the cells that absorbs sunlight energy. Exposure of genomic DNA to UV light leads to the formation of multitude of types of damage (depending on wavelength and exposure time) that are removed by effectively working repair pathways. The aim of this review is to summarize current knowledge considering cellular response to UV radiation with special focus on DNA damage and repair and to give a comprehensive insight for new researchers in this field. We also highlight most important future prospects considering application of the progressing knowledge of UV response for the clinical control of diverse pathologies.
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Affiliation(s)
- Mateusz Kciuk
- Doctoral School of Exact and Natural Sciences, University of Lodz, Banacha Street 12/16, 90-237 Lodz, Poland
- Department of Molecular Biotechnology and Genetics, Faculty of Biology and Environmental Protection, University of Lodz, 12/16 Banacha St., 90-237 Lodz, Poland; (B.M.); (R.K.)
- Correspondence:
| | - Beata Marciniak
- Department of Molecular Biotechnology and Genetics, Faculty of Biology and Environmental Protection, University of Lodz, 12/16 Banacha St., 90-237 Lodz, Poland; (B.M.); (R.K.)
| | - Mariusz Mojzych
- Department of Chemistry, Siedlce University of Natural Sciences and Humanities, 3 Maja 54, 08-110 Siedlce, Poland;
| | - Renata Kontek
- Department of Molecular Biotechnology and Genetics, Faculty of Biology and Environmental Protection, University of Lodz, 12/16 Banacha St., 90-237 Lodz, Poland; (B.M.); (R.K.)
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15
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Ouyang X, Li X, Liu J, Liu Y, Xie Y, Du Z, Xie H, Chen B, Lu W, Chen D. Structure-activity relationship and mechanism of four monostilbenes with respect to ferroptosis inhibition. RSC Adv 2020; 10:31171-31179. [PMID: 35520676 PMCID: PMC9056428 DOI: 10.1039/d0ra04896h] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 08/08/2020] [Indexed: 12/20/2022] Open
Abstract
Erastin-treated bone marrow-derived mesenchymal stem cells (bmMSCs) were prepared and used to compare the ferroptosis inhibitory bioactivities of four monostilbenes, including rhapontigenin (1a), isorhapontigenin (1b), piceatannol-3'-O-glucoside (1c), and rhapontin (1d). Their relative levels were 1c ≈ 1b > 1a ≈ 1d in 4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid (C11-BODIPY), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and flow cytometric assays. The comparison highlighted two 4'-OH-containing monostilbenes (1c and 1b) in ferroptosis inhibitory bioactivity. Similar structure-activity relationships were also observed in antioxidant assays, including 1,1-diphenyl-2-picryl-hydrazl radical (DPPH˙)-trapping, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO˙)-trapping, and Fe3+-reducing assays. UPLC-ESI-Q-TOF-MS analysis of the DPPH˙-trapping reaction of the monostilbenes revealed that they can inhibit ferroptosis in erastin-treated bmMSCs through a hydrogen donation-based antioxidant pathway. After hydrogen donation, these monostilbenes usually produce the corresponding stable dimers; additionally, the hydrogen donation potential was enhanced by the 4'-OH. The enhancement by 4'-OH can be attributed to the transannular resonance effect. This effect can be used to predict the inhibition potential of other π-π conjugative phenolics.
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Affiliation(s)
- Xiaojian Ouyang
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine Guangzhou 510006 China
| | - Xican Li
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine Guangzhou 510006 China
| | - Jie Liu
- School of Basic Medical Science, Guangzhou University of Chinese Medicine Guangzhou 510006 China
- The Research Center of Basic Integrative Medicine, Guangzhou University of Chinese Medicine Guangzhou 510006 China
| | - Yangping Liu
- School of Basic Medical Science, Guangzhou University of Chinese Medicine Guangzhou 510006 China
- The Research Center of Basic Integrative Medicine, Guangzhou University of Chinese Medicine Guangzhou 510006 China
| | - Yulu Xie
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine Guangzhou 510006 China
| | - Zhongcun Du
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine Guangzhou 510006 China
| | - Hong Xie
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine Guangzhou 510006 China
| | - Ban Chen
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine Guangzhou 510006 China
| | - Wenbiao Lu
- School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine Guangzhou 510006 China
| | - Dongfeng Chen
- School of Basic Medical Science, Guangzhou University of Chinese Medicine Guangzhou 510006 China
- The Research Center of Basic Integrative Medicine, Guangzhou University of Chinese Medicine Guangzhou 510006 China
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Matkarimov BT, Saparbaev MK. DNA Repair and Mutagenesis in Vertebrate Mitochondria: Evidence for Asymmetric DNA Strand Inheritance. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1241:77-100. [DOI: 10.1007/978-3-030-41283-8_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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17
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Bailey LJ, Bianchi J, Doherty AJ. PrimPol is required for the maintenance of efficient nuclear and mitochondrial DNA replication in human cells. Nucleic Acids Res 2019; 47:4026-4038. [PMID: 30715459 PMCID: PMC6486543 DOI: 10.1093/nar/gkz056] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 01/14/2019] [Accepted: 01/28/2019] [Indexed: 12/14/2022] Open
Abstract
Eukaryotic Primase-Polymerase (PrimPol) is an enzyme that maintains efficient DNA duplication by repriming replication restart downstream of replicase stalling lesions and structures. To elucidate the cellular requirements for PrimPol in human cells, we generated PrimPol-deleted cell lines and show that it plays key roles in maintaining active replication in both the nucleus and mitochondrion, even in the absence of exogenous damage. Human cells lacking PrimPol exhibit delayed recovery after UV-C damage and increased mutation frequency, micronuclei and sister chromatin exchanges but are not sensitive to genotoxins. PrimPol is also required during mitochondrial replication, with PrimPol-deficient cells having increased mtDNA copy number but displaying a significant decrease in replication. Deletion of PrimPol in XPV cells, lacking functional polymerase Eta, causes an increase in DNA damage sensitivity and pronounced fork stalling after UV-C treatment. We show that, unlike canonical TLS polymerases, PrimPol is important for allowing active replication to proceed, even in the absence of exogenous damage, thus preventing the accumulation of excessive fork stalling and genetic mutations. Together, these findings highlight the importance of PrimPol for maintaining efficient DNA replication in unperturbed cells and its complementary roles, with Pol Eta, in damage tolerance in human cells.
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Affiliation(s)
- Laura J Bailey
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, UK
| | - Julie Bianchi
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, UK
| | - Aidan J Doherty
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RQ, UK
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18
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Hämäläinen RH, Landoni JC, Ahlqvist KJ, Goffart S, Ryytty S, Rahman MO, Brilhante V, Icay K, Hautaniemi S, Wang L, Laiho M, Suomalainen A. Defects in mtDNA replication challenge nuclear genome stability through nucleotide depletion and provide a unifying mechanism for mouse progerias. Nat Metab 2019; 1:958-965. [PMID: 32694840 DOI: 10.1038/s42255-019-0120-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 09/04/2019] [Indexed: 01/07/2023]
Abstract
Mitochondrial DNA (mtDNA) mutagenesis and nuclear DNA repair defects are considered cellular mechanisms of ageing. mtDNA mutator mice with increased mtDNA mutagenesis show signs of premature ageing. However, why patients with mitochondrial diseases, or mice with other forms of mitochondrial dysfunction, do not age prematurely remains unknown. Here, we show that cells from mutator mice display challenged nuclear genome maintenance similar to that observed in progeric cells with defects in nuclear DNA repair. Cells from mutator mice show slow nuclear DNA replication fork progression, cell cycle stalling and chronic DNA replication stress, leading to double-strand DNA breaks in proliferating progenitor or stem cells. The underlying mechanism involves increased mtDNA replication frequency, sequestering of nucleotides to mitochondria, depletion of total cellular nucleotide pools, decreased deoxynucleoside 5'-triphosphate (dNTP) availability for nuclear genome replication and compromised nuclear genome maintenance. Our data indicate that defects in mtDNA replication can challenge nuclear genome stability. We suggest that defects in nuclear genome maintenance, particularly in the stem cell compartment, represent a unified mechanism for mouse progerias. Therefore, through their destabilizing effects on the nuclear genome, mtDNA mutations are indirect contributors to organismal ageing, suggesting that the direct role of mtDNA mutations in driving ageing-like symptoms might need to be revisited.
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Affiliation(s)
- Riikka H Hämäläinen
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.
- Research Program in Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland.
| | - Juan C Landoni
- Research Program in Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland
| | - Kati J Ahlqvist
- Research Program in Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland
| | - Steffi Goffart
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Sanna Ryytty
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - M Obaidur Rahman
- A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Virginia Brilhante
- Research Program in Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland
| | - Katherine Icay
- Research Program in Systems Oncology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Sampsa Hautaniemi
- Research Program in Systems Oncology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Liya Wang
- Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Marikki Laiho
- Department of Radiation Oncology and Molecular Radiation Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Anu Suomalainen
- Research Program in Stem Cells and Metabolism, University of Helsinki, Helsinki, Finland.
- Helsinki University Hospital, Department of Neurosciences, Helsinki, Finland.
- Neuroscience Center, University of Helsinki, Helsinki, Finland.
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19
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Ciesielski GL, Nadalutti CA, Oliveira MT, Jacobs HT, Griffith JD, Kaguni LS. Structural rearrangements in the mitochondrial genome of Drosophila melanogaster induced by elevated levels of the replicative DNA helicase. Nucleic Acids Res 2019; 46:3034-3046. [PMID: 29432582 PMCID: PMC5887560 DOI: 10.1093/nar/gky094] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 02/02/2018] [Indexed: 01/10/2023] Open
Abstract
Pathological conditions impairing functions of mitochondria often lead to compensatory upregulation of the mitochondrial DNA (mtDNA) replisome machinery, and the replicative DNA helicase appears to be a key factor in regulating mtDNA copy number. Moreover, mtDNA helicase mutations have been associated with structural rearrangements of the mitochondrial genome. To evaluate the effects of elevated levels of the mtDNA helicase on the integrity and replication of the mitochondrial genome, we overexpressed the helicase in Drosophila melanogaster Schneider cells and analyzed the mtDNA by two-dimensional neutral agarose gel electrophoresis and electron microscopy. We found that elevation of mtDNA helicase levels increases the quantity of replication intermediates and alleviates pausing at the replication slow zones. Though we did not observe a concomitant alteration in mtDNA copy number, we observed deletions specific to the segment of repeated elements in the immediate vicinity of the origin of replication, and an accumulation of species characteristic of replication fork stalling. We also found elevated levels of RNA that are retained in the replication intermediates. Together, our results suggest that upregulation of mtDNA helicase promotes the process of mtDNA replication but also results in genome destabilization.
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Affiliation(s)
- Grzegorz L Ciesielski
- Department of Biochemistry and Molecular Biology and Center for Mitochondrial Science and Medicine, Michigan State University, East Lansing, MI, USA.,Institute of Biosciences and Medical Technology, University of Tampere, FI-33014 Tampere, Finland
| | - Cristina A Nadalutti
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Marcos T Oliveira
- Department of Biochemistry and Molecular Biology and Center for Mitochondrial Science and Medicine, Michigan State University, East Lansing, MI, USA
| | - Howard T Jacobs
- Institute of Biosciences and Medical Technology, University of Tampere, FI-33014 Tampere, Finland.,Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland
| | - Jack D Griffith
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Laurie S Kaguni
- Department of Biochemistry and Molecular Biology and Center for Mitochondrial Science and Medicine, Michigan State University, East Lansing, MI, USA.,Institute of Biosciences and Medical Technology, University of Tampere, FI-33014 Tampere, Finland
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20
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Cabrera F, Ortega M, Velarde F, Parra E, Gallardo S, Barba D, Soto L, Peña G, Pedroza LA, Jorgensen C, Khoury M, Caicedo A. Primary allogeneic mitochondrial mix (PAMM) transfer/transplant by MitoCeption to address damage in PBMCs caused by ultraviolet radiation. BMC Biotechnol 2019; 19:42. [PMID: 31253149 PMCID: PMC6599354 DOI: 10.1186/s12896-019-0534-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 06/14/2019] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Artificial Mitochondrial Transfer or Transplant (AMT/T) can be used to reduce the stress and loss of viability of damaged cells. In MitoCeption, a type of AMT/T, the isolated mitochondria and recipient cells are centrifuged together at 4 °C and then co-incubated at 37 °C in normal culture conditions, inducing the transfer. Ultraviolet radiation (UVR) can affect mitochondria and other cell structures, resulting in tissue stress, aging, and immunosuppression. AMT/T could be used to repair UVR cellular and mitochondrial damage. We studied if a mitochondrial mix from different donors (Primary Allogeneic Mitochondrial Mix, PAMM) can repair UVR damage and promote cell survival. RESULTS Using a simplified adaption of the MitoCeption protocol, we used peripheral blood mononuclear cells (PBMCs) as the recipient cell model of the PAMM in order to determine if this protocol could repair UVR damage. Our results showed that when PBMCs are exposed to UVR, there is a decrease in metabolic activity, mitochondrial mass, and mtDNA sequence stability as well as an increase in p53 expression and the percentage of dead cells. When PAMM MitoCeption was used on UVR-damaged cells, it successfully transferred mitochondria from different donors to distinct PBMCs populations and repaired the observed UVR damage. CONCLUSION Our results represent an advancement in the applications of MitoCeption and other AMT/T. We showed that PBMCs could be used as a PAMM source of mitochondria. We also showed that these mitochondria can be transferred in a mix from different donors (PAMM) to UVR-damaged, non-adherent primary cells. Additionally, we decreased the duration of the MitoCeption protocol.
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Affiliation(s)
- Francisco Cabrera
- Colegio de Ciencias de la Salud, Escuela de Medicina Veterinaria, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
- IRMB CHU Saint Eloi, University of Montpellier, France, 80 rue Augustin Fliche, 34295 Montpellier, cedex 5 France
- Instituto de Investigaciones en Biomedicina, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
- Mito-Act Research Consortium, Quito, Ecuador
| | - Mayra Ortega
- Colegio de Ciencias Biológicas y Ambientales, Escuela de Biotecnología, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
- Instituto de Investigaciones en Biomedicina, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
- Mito-Act Research Consortium, Quito, Ecuador
| | - Francesca Velarde
- Instituto de Investigaciones en Biomedicina, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
- Mito-Act Research Consortium, Quito, Ecuador
| | - Eliseo Parra
- Laboratory of Nano-Regenerative Medicine, Faculty of Medicine, Universidad de Los Andes, Santiago, Chile
- Consorcio Regenero, Chilean Consortium for Regenerative Medicine, Santiago, Chile
- Cells for Cells, Santiago, Chile
| | - Stephany Gallardo
- Colegio de Ciencias Biológicas y Ambientales, Escuela de Biotecnología, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
| | - Diego Barba
- Colegio de Ciencias de la Salud, Escuela de Medicina, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
| | - Lina Soto
- Colegio de Ciencias de la Salud, Escuela de Medicina, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
| | - Gabriela Peña
- Colegio de Ciencias de la Salud, Escuela de Medicina, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
| | - Luis Alberto Pedroza
- Colegio de Ciencias de la Salud, Escuela de Medicina, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
- Baylor College of Medicine: Department of Pediatrics, Section of Immunology, Allergy, and Rheumatology, Baylor College of Medicine, Houston, TX USA
| | - Christian Jorgensen
- IRMB CHU Saint Eloi, University of Montpellier, France, 80 rue Augustin Fliche, 34295 Montpellier, cedex 5 France
- Mito-Act Research Consortium, Quito, Ecuador
| | - Maroun Khoury
- Laboratory of Nano-Regenerative Medicine, Faculty of Medicine, Universidad de Los Andes, Santiago, Chile
- Consorcio Regenero, Chilean Consortium for Regenerative Medicine, Santiago, Chile
- Cells for Cells, Santiago, Chile
- Mito-Act Research Consortium, Quito, Ecuador
| | - Andrés Caicedo
- Colegio de Ciencias de la Salud, Escuela de Medicina, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
- Instituto de Investigaciones en Biomedicina, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
- Mito-Act Research Consortium, Quito, Ecuador
- Sistemas Médicos, SIME, Universidad San Francisco de Quito, 17-12-841 Quito, Ecuador
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Abstract
Replication stalling has been associated with the formation of pathological mitochondrial DNA (mtDNA) rearrangements. Yet, almost nothing is known about the fate of stalled replication intermediates in mitochondria. We show here that replication stalling in mitochondria leads to replication fork regression and mtDNA double-strand breaks. The resulting mtDNA fragments are normally degraded by a mechanism involving the mitochondrial exonuclease MGME1, and the loss of this enzyme results in accumulation of linear and recombining mtDNA species. Additionally, replication stress promotes the initiation of alternative replication origins as an apparent means of rescue by fork convergence. Besides demonstrating an interplay between two major mechanisms rescuing stalled replication forks – mtDNA degradation and homology-dependent repair – our data provide evidence that mitochondria employ similar mechanisms to cope with replication stress as known from other genetic systems.
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22
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Raman spectroscopy on live mouse early embryo while it continues to develop into blastocyst in vitro. Sci Rep 2019; 9:6636. [PMID: 31036868 PMCID: PMC6488652 DOI: 10.1038/s41598-019-42958-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 03/27/2019] [Indexed: 12/18/2022] Open
Abstract
Laser based spectroscopic methods can be versatile tools in investigating early stage mammalian embryo structure and biochemical processes in live oocytes and embryos. The limiting factor for using the laser methods in embryological studies is the effect of laser irradiation on the ova. The aim of this work is to explore the optimal parameters of the laser exposure in Raman spectroscopic measurements applicable for studying live early embryos in vitro without impacting their developmental capability. Raman spectra from different areas of mouse oocytes and 2-cells embryos were measured and analyzed. The laser power and exposure time were varied and further embryo development was evaluated to select optimal conditions of the measurements. This work demonstrates safe laser irradiation parameters can be selected, which allow acquisition of Raman spectra suitable for further analysis without affecting the early mouse embryo development in vitro up to morphologically normal blastocyst. The estimation of living embryo state is demonstrated via analysis and comparison of the spectra from fertilized embryo with the spectra from unfertilized oocytes or embryos subjected to UV laser irradiation. These results demonstrate the possibility of investigating preimplantation mammalian embryo development and estimating its state/quality. It will have potential in developing prognosis of mammalian embryos in assisted reproductive technologies.
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23
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Hangas A, Aasumets K, Kekäläinen NJ, Paloheinä M, Pohjoismäki JL, Gerhold JM, Goffart S. Ciprofloxacin impairs mitochondrial DNA replication initiation through inhibition of Topoisomerase 2. Nucleic Acids Res 2018; 46:9625-9636. [PMID: 30169847 PMCID: PMC6182158 DOI: 10.1093/nar/gky793] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 08/21/2018] [Accepted: 08/23/2018] [Indexed: 11/17/2022] Open
Abstract
Maintenance of topological homeostasis is vital for gene expression and genome replication in all organisms. Similar to other circular genomes, also mitochondrial DNA (mtDNA) is known to exist in various different topological forms, although their functional significance remains unknown. We report here that both known type II topoisomerases Top2α and Top2β are present in mammalian mitochondria, with especially Top2β regulating the supercoiling state of mtDNA. Loss of Top2β or its inhibition by ciprofloxacin results in accumulation of positively supercoiled mtDNA, followed by cessation of mitochondrial transcription and replication initiation, causing depletion of mtDNA copy number. These mitochondrial effects block both cell proliferation and differentiation, possibly explaining some of the side effects associated with fluoroquinolone antibiotics. Our results show for the first time the importance of topology for maintenance of mtDNA homeostasis and provide novel insight into the mitochondrial effects of fluoroquinolones.
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Affiliation(s)
- Anu Hangas
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
| | - Koit Aasumets
- Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia
| | - Nina J Kekäläinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
| | - Mika Paloheinä
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
| | - Jaakko L Pohjoismäki
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
| | - Joachim M Gerhold
- Institute of Technology, University of Tartu, Nooruse 1, 50411 Tartu, Estonia
| | - Steffi Goffart
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
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24
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Abstract
Mitochondrial DNA (mtDNA), which is essential for mitochondrial and cell function, is replicated and transcribed in the organelle by proteins that are entirely coded in the nucleus. Replication of mtDNA is challenged not only by threats related to the replication machinery and orchestration of DNA synthesis, but also by factors linked to the peculiarity of this genome. Indeed the architecture, organization, copy number, and location of mtDNA, which are markedly distinct from the nuclear genome, require ad hoc and complex regulation to ensure coordinated replication. As a consequence sub-optimal mtDNA replication, which results from compromised regulation of these factors, is generally associated with mitochondrial dysfunction and disease. Mitochondrial DNA replication should be considered in the context of the organelle and the whole cell, and not just a single genome or a single replication event. Major threats to mtDNA replication are linked to its dependence on both mitochondrial and nuclear factors, which require exquisite coordination of these crucial subcellular compartments. Moreover, regulation of replication events deals with a dynamic population of multiple mtDNA molecules rather than with a fixed number of genome copies, as it is the case for nuclear DNA. Importantly, the mechanistic aspects of mtDNA replication are still debated. We describe here major challenges for human mtDNA replication, the mechanistic aspects of the process that are to a large extent original, and their consequences on disease.
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Affiliation(s)
- Miria Ricchetti
- Institut Pasteur, Department of Developmental and Stem Cell Biology, Stem Cells and Development, 75724 Cedex15, Paris, France; Team Stability of Nuclear and Mitochondrial DNA, CNRS UMR 3738, 75724, Cedex15, Paris, France.
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25
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Herbers E, Kekäläinen NJ, Hangas A, Pohjoismäki JL, Goffart S. Tissue specific differences in mitochondrial DNA maintenance and expression. Mitochondrion 2018; 44:85-92. [PMID: 29339192 DOI: 10.1016/j.mito.2018.01.004] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 01/05/2018] [Accepted: 01/11/2018] [Indexed: 01/17/2023]
Abstract
The different cell types of multicellular organisms have specialized physiological requirements, affecting also their mitochondrial energy production and metabolism. The genome of mitochondria is essential for mitochondrial oxidative phosphorylation (OXHPOS) and thus plays a central role in many human mitochondrial pathologies. Disorders affecting mitochondrial DNA (mtDNA) maintenance are typically resulting in a tissue-specific pattern of mtDNA deletions and rearrangements. Despite this role in disease as well as a biomarker of mitochondrial biogenesis, the tissue-specific parameters of mitochondrial DNA maintenance have been virtually unexplored. In the presented study, we investigated mtDNA replication, topology, gene expression and damage in six different tissues of adult mice and sought to correlate these with the levels of known protein factors involved in mtDNA replication and transcription. Our results show that while liver and kidney cells replicate their mtDNA using the asynchronous mechanism known from cultured cells, tissues with high OXPHOS activity, such as heart, brain, skeletal muscle and brown fat, employ a strand-coupled replication mode, combined with increased levels of recombination. The strand-coupled replication mode correlated also with mtDNA damage levels, indicating that the replication mechanism represents a tissue-specific strategy to deal with intrinsic oxidative stress. While the preferred replication mode did not correlate with mtDNA transcription or the levels of most known mtDNA maintenance proteins, mtSSB was most abundant in tissues using strand-asynchronous mechanism. Although mitochondrial transcripts were most abundant in tissues with high metabolic rate, the mtDNA copy number per tissue mass was remarkably similar in all tissues. We propose that the tissue-specific features of mtDNA maintenance are primarily driven by the intrinsic reactive oxygen species exposure, mediated by DNA repair factors, whose identity remains to be elucidated.
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Affiliation(s)
- Elena Herbers
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FI 80101, Joensuu, Finland
| | - Nina J Kekäläinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FI 80101, Joensuu, Finland
| | - Anu Hangas
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FI 80101, Joensuu, Finland
| | - Jaakko L Pohjoismäki
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FI 80101, Joensuu, Finland
| | - Steffi Goffart
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, FI 80101, Joensuu, Finland.
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Enhanced Repair of UV-Induced DNA Damage by 1,25-Dihydroxyvitamin D 3 in Skin Is Linked to Pathways that Control Cellular Energy. J Invest Dermatol 2017; 138:1146-1156. [PMID: 29258892 DOI: 10.1016/j.jid.2017.11.037] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 11/03/2017] [Accepted: 11/13/2017] [Indexed: 01/22/2023]
Abstract
Inadequately repaired post-UV DNA damage results in skin cancers. DNA repair requires energy but skin cells have limited capacity to produce energy after UV insult. We examined whether energy supply is important for DNA repair after UV exposure, in the presence of 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3), which reduces UV-induced DNA damage and photocarcinogenesis in a variety of models. After UV exposure of primary human keratinocytes, the addition of 1,25(OH)2D3 increased unscheduled DNA synthesis, a measure of DNA repair. Oxidative phosphorylation was depleted in UV-irradiated keratinocytes to undetectable levels within an hour of UV irradiation. Treatment with 1,25(OH)2D3 but not vehicle increased glycolysis after UV. 2-Deoxyglucose-dependent inhibition of glycolysis abolished the reduction in cyclobutane pyrimidine dimers by 1,25(OH)2D3, whereas inhibition of oxidative phosphorylation had no effect. 1,25(OH)2D3 increased autophagy and modulated PINK1/Parkin consistent with enhanced mitophagy. These data confirm that energy availability is limited in keratinocytes after exposure to UV. In the presence of 1,25(OH)2D3, glycolysis is enhanced along with energy-conserving processes such as autophagy and mitophagy, resulting in increased repair of cyclobutane pyrimidine dimers and decreased oxidative DNA damage. Increased energy availability in the presence of 1,25(OH)2D3 is an important contributor to DNA repair in skin after UV exposure.
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Abstract
Eukaryotic PrimPol is a recently discovered DNA-dependent DNA primase and translesion synthesis DNA polymerase found in the nucleus and mitochondria. Although PrimPol has been shown to be required for repriming of stalled replication forks in the nucleus, its role in mitochondria has remained unresolved. Here we demonstrate in vivo and in vitro that PrimPol can reinitiate stalled mtDNA replication and can prime mtDNA replication from nonconventional origins. Our results not only help in the understanding of how mitochondria cope with replicative stress but can also explain some controversial features of the lagging-strand replication.
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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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Pohjoismäki JL, Goffart S. The role of mitochondria in cardiac development and protection. Free Radic Biol Med 2017; 106:345-354. [PMID: 28216385 DOI: 10.1016/j.freeradbiomed.2017.02.032] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 01/27/2017] [Accepted: 02/14/2017] [Indexed: 12/31/2022]
Abstract
Mitochondria are essential for the development as well as maintenance of the myocardium, the most energy consuming tissue in the human body. Mitochondria are not only a source of ATP energy but also generators of reactive oxygen species (ROS), that cause oxidative damage, but also regulate physiological processes such as the switch from hyperplastic to hypertrophic growth after birth. As excess ROS production and oxidative damage are associated with cardiac pathology, it is not surprising that much of the research focused on the deleterious aspects of free radicals. However, cardiomyocytes are naturally highly adapted against repeating oxidative insults, with evidence suggesting that moderate and acute ROS exposure has beneficial consequences for mitochondrial maintenance and cardiac health. Antioxidant defenses, mitochondrial quality control, mtDNA maintenance mechanisms as well as mitochondrial fusion and fission improve mitochondrial function and cardiomyocyte survival under stress conditions. As these adaptive processes can be induced, promoting mitohormesis or mitochondrial biogenesis using controlled ROS exposure could provide a promising strategy to increase cardiomyocyte survival and prevent pathological remodeling of the myocardium.
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Affiliation(s)
- Jaakko L Pohjoismäki
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland.
| | - Steffi Goffart
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland
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Workalemahu T, Enquobahrie DA, Tadesse MG, Hevner K, Gelaye B, Sanchez SE, Williams MA. Genetic variations related to maternal whole blood mitochondrial DNA copy number: a genome-wide and candidate gene study. J Matern Fetal Neonatal Med 2017; 30:2433-2439. [PMID: 27806667 DOI: 10.1080/14767058.2016.1252747] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
We conducted genome-wide (GWAS) and candidate gene association studies of maternal mitochondrial DNA copy number. Maternal peripheral blood was collected during labor and delivery admission from 471 participants of a placental abruption case-control study conducted in Lima, Peru. Single nucleotide polymorphism (SNP) genotyping was performed using the Illumina Cardio-Metabo Chip. Whole blood mitochondrial DNA (mtDNA) copy number was measured using qRT-PCR techniques. We evaluated 119,629 SNPs in the GWAS and 161 SNPs (in 29 mitochondrial biogenesis and oxidative phosphorylation genes) in the candidate association study. Top hits from GWAS and the candidate gene study were selected to compute weighted genetic risk scores (wGRS). Linear regression models were used to calculate effect size estimates and related nominal p values. The top hit in our GWAS was chr19:51063065 in FOXA3 (empirical p values = 2.20e - 6). A total of 134 SNPs had p values < 0.001 including rs17111633 in CNNM1 (p values = 6.32e - 6) and chr19:51083059 in MYPOP (p values = 3.23e - 5). In the candidate association study, several SNPs in PPARG, PRKCA, SP1 and THRB were associated with mtDNA copy number (p values < 0.05). mtDNA copy number was significantly associated with wGRS based on top GWAS hits (β = 0.49, 95% CI:0.38-0.60, p < 0.001). Variations in nuclear DNA are potentially associated with maternal mtDNA copy number.
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Affiliation(s)
| | - Daniel A Enquobahrie
- a Department of Epidemiology, School of Public Health, University of Washington , Seattle, WA , USA.,b Center for Perinatal Studies, Swedish Medical Center , Seattle, WA , USA
| | - Mahlet G Tadesse
- c Department of Mathematics and Statistics, Georgetown University , Washington, DC , USA
| | - Karin Hevner
- b Center for Perinatal Studies, Swedish Medical Center , Seattle, WA , USA
| | - Bizu Gelaye
- d Department of Epidemiology, Harvard T.H. Chan School of Public Health , Boston, MA , USA
| | - Sixto E Sanchez
- e Asociación Civil PROESA, Lima, Peru; Universidad Peruana de Ciencias Aplicados , Lima , Peru
| | - Michelle A Williams
- d Department of Epidemiology, Harvard T.H. Chan School of Public Health , Boston, MA , USA
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Kleszczyński K, Zillikens D, Fischer TW. Melatonin enhances mitochondrial ATP synthesis, reduces reactive oxygen species formation, and mediates translocation of the nuclear erythroid 2-related factor 2 resulting in activation of phase-2 antioxidant enzymes (γ-GCS, HO-1, NQO1) in ultraviolet radiation-treated normal human epidermal keratinocytes (NHEK). J Pineal Res 2016; 61:187-97. [PMID: 27117941 DOI: 10.1111/jpi.12338] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 04/21/2016] [Indexed: 12/20/2022]
Abstract
Melatonin is an ubiquitous molecule with a variety of functions including potent antioxidative properties. Due to its lipophilic character, it easily crosses cellular and intracellular membranes and reaches all subcellular organelles. Because of its ability to scavenge free radicals, melatonin protects against oxidative stress, for example, induced by ultraviolet radiation (UVR). Here, we investigated, in a dose-dependent (0, 10, 25, and 50 mJ/cm(2) ) and time-dependent (0, 4, 24, 48 hr post-UVR) manner, whether melatonin prevents the UVR-mediated alterations in ATP synthesis and the generation of reactive oxygen species (ROS) in normal human epidermal keratinocytes (NHEK). Additionally, we evaluated the molecular mechanism of action of melatonin with regard to activation of phase-2 antioxidative enzymes via nuclear erythroid 2-related factor (Nrf2). We found that (i) melatonin counteracted UVR-induced alterations in the ATP synthesis and reduced free radical formation; (ii) melatonin induced the translocation of Nrf2 transcription factor from the cytosol into the nucleus resulting in, (iii) melatonin enhanced gene expression of phase-2 antioxidative enzymes including γ-glutamylcysteine synthetase (γ-GCS), heme oxygenase-1 (HO-1), and NADPH: quinone dehydrogenase-1 (NQO1) representing an elevated antioxidative response of keratinocytes. These results suggest that melatonin not only directly scavenges ROS, but also significantly induces the activation of phase-2 antioxidative enzymes via the Nrf2 pathway uncovering a new action mechanism that supports the ability of keratinocytes to protect themselves from UVR-mediated oxidative stress.
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Affiliation(s)
| | - Detlef Zillikens
- Department of Dermatology, University of Lübeck, Lübeck, Germany
| | - Tobias W Fischer
- Department of Dermatology, University of Lübeck, Lübeck, Germany
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Sen D, Patel G, Patel SS. Homologous DNA strand exchange activity of the human mitochondrial DNA helicase TWINKLE. Nucleic Acids Res 2016; 44:4200-10. [PMID: 26887820 PMCID: PMC4872091 DOI: 10.1093/nar/gkw098] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 02/08/2016] [Indexed: 01/03/2023] Open
Abstract
A crucial component of the human mitochondrial DNA replisome is the ring-shaped helicase TWINKLE-a phage T7-gene 4-like protein expressed in the nucleus and localized in the human mitochondria. Our previous studies showed that despite being a helicase, TWINKLE has unique DNA annealing activity. At the time, the implications of DNA annealing by TWINKLE were unclear. Herein, we report that TWINKLE uses DNA annealing function to actively catalyze strand-exchange reaction between the unwinding substrate and a homologous single-stranded DNA. Using various biochemical experiments, we demonstrate that the mechanism of strand-exchange involves active coupling of unwinding and annealing reactions by the TWINKLE. Unlike strand-annealing, the strand-exchange reaction requires nucleotide hydrolysis and greatly stimulated by short region of homology between the recombining DNA strands that promote joint molecule formation to initiate strand-exchange. Furthermore, we show that TWINKLE catalyzes branch migration by resolving homologous four-way junction DNA. These four DNA modifying activities of TWINKLE: strand-separation, strand-annealing, strand-exchange and branch migration suggest a dual role of TWINKLE in mitochondrial DNA maintenance. In addition to playing a major role in fork progression during leading strand DNA synthesis, we propose that TWINKLE is involved in recombinational repair of the human mitochondrial DNA.
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Affiliation(s)
- Doyel Sen
- Rutgers University, Robert Wood Johnson Medical School, Department of Biochemistry and Molecular Biology, NJ 08854, USA
| | - Gayatri Patel
- Rutgers University, Robert Wood Johnson Medical School, Department of Biochemistry and Molecular Biology, NJ 08854, USA
| | - Smita S Patel
- Rutgers University, Robert Wood Johnson Medical School, Department of Biochemistry and Molecular Biology, NJ 08854, USA
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