| 1. |
- Boldinova, Elizaveta O., et al.
(author)
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DNA Damage Tolerance by Eukaryotic DNA Polymerase and Primase PrimPol
- 2017
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In: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 18:7
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Research review (peer-reviewed)abstract
- PrimPol is a human deoxyribonucleic acid (DNA) polymerase that also possesses primase activity and is involved in DNA damage tolerance, the prevention of genome instability and mitochondrial DNA maintenance. In this review, we focus on recent advances in biochemical and crystallographic studies of PrimPol, as well as in identification of new protein-protein interaction partners. Furthermore, we discuss the possible functions of PrimPol in both the nucleus and the mitochondria.
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| 2. |
- Doimo, Mara, et al.
(author)
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MtDNA replication, maintenance, and nucleoid organization
- 2020
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In: The human mitochondrial genome. - : Academic Press. - 9780128196564 ; , s. 3-33
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Book chapter (peer-reviewed)abstract
- Part of the genetic information in human cells resides in the mitochondria. Faithful maintenance of mitochondrial deoxyribonucleic acid (mtDNA) is crucial for the oxidative phosphorylation system that produces the majority of the cellular ATP, and therefore to life. This chapter provides an introduction into the characteristics of human mtDNA and summarizes the processes and factors required for the replication and maintenance of this small but essential genome. We also describe the organization of mtDNA in specialized nucleoprotein structures called nucleoids. Where applicable, we refer to human disease states that are caused by defects in the described factors or processes.
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| 3. |
- Stojkovic, Gorazd, et al.
(author)
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Oxidative DNA damage stalls the human mitochondrial replisome
- 2016
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Journal article (peer-reviewed)abstract
- Oxidative stress is capable of causing damage to various cellular constituents, including DNA. There is however limited knowledge on how oxidative stress influences mitochondrial DNA and its replication. Here, we have used purified mtDNA replication proteins, i.e. DNA polymerase. holoenzyme, the mitochondrial single-stranded DNA binding protein mtSSB, the replicative helicase Twinkle and the proposed mitochondrial translesion synthesis polymerase PrimPol to study lesion bypass synthesis on oxidative damage-containing DNA templates. Our studies were carried out at dNTP levels representative of those prevailing either in cycling or in non-dividing cells. At dNTP concentrations that mimic those in cycling cells, the replication machinery showed substantial stalling at sites of damage, and these problems were further exacerbated at the lower dNTP concentrations present in resting cells. PrimPol, the translesion synthesis polymerase identified inside mammalian mitochondria, did not promote mtDNA replication fork bypass of the damage. This argues against a conventional role for PrimPol as a mitochondrial translesion synthesis DNA polymerase for oxidative DNA damage; however, we show that Twinkle, the mtDNA replicative helicase, is able to stimulate PrimPol DNA synthesis in vitro, suggestive of an as yet unidentified role of PrimPol in mtDNA metabolism.
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| 4. |
- Wanrooij, Paulina H., et al.
(author)
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Ribonucleotides incorporated by the yeast mitochondrial DNA polymerase are not repaired
- 2017
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 114:47, s. 12466-12471
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Journal article (peer-reviewed)abstract
- Incorporation of ribonucleotides into DNA during genome replication is a significant source of genomic instability. The frequency of ribonucleotides in DNA is determined by deoxyribonucleoside triphosphate/ribonucleoside triphosphate (dNTP/rNTP) ratios, by the ability of DNA polymerases to discriminate against ribonucleotides, and by the capacity of repair mechanisms to remove incorporated ribonucleotides. To simultaneously compare how the nuclear and mitochondrial genomes incorporate and remove ribonucleotides, we challenged these processes by changing the balance of cellular dNTPs. Using a collection of yeast strains with altered dNTP pools, we discovered an inverse relationship between the concentration of individual dNTPs and the amount of the corresponding ribonucleotides incorporated in mitochondrial DNA, while in nuclear DNA the ribonucleotide pattern was only altered in the absence of ribonucleotide excision repair. Our analysis uncovers major differences in ribonucleotide repair between the two genomes and provides concrete evidence that yeast mitochondria lack mechanisms for removal of ribonucleotides incorporated by the mtDNA polymerase. Furthermore, as cytosolic dNTP pool imbalances were transmitted equally well into the nucleus and the mitochondria, our results support a view of the cytosolic and mitochondrial dNTP pools in frequent exchange. © 2017, National Academy of Sciences. All rights reserved.
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| 5. |
- Wanrooij, Sjoerd, et al.
(author)
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In vivo mutagenesis reveals that OriL is essential for mitochondrial DNA replication.
- 2012
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In: EMBO reports. - : EMBO. - 1469-3178 .- 1469-221X. ; 13:12, s. 1130-7
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Journal article (peer-reviewed)abstract
- The mechanisms of mitochondrial DNA replication have been hotly debated for a decade. The strand-displacement model states that lagging-strand DNA synthesis is initiated from the origin of light-strand DNA replication (OriL), whereas the strand-coupled model implies that OriL is dispensable. Mammalian mitochondria cannot be transfected and the requirements of OriL in vivo have therefore not been addressed. We here use in vivo saturation mutagenesis to demonstrate that OriL is essential for mtDNA maintenance in the mouse. Biochemical and bioinformatic analyses show that OriL is functionally conserved in vertebrates. Our findings strongly support the strand-displacement model for mtDNA replication.
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| 6. |
- Breidenstein, Annika, et al.
(author)
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PrgE: an OB-fold protein from plasmid pCF10 with striking differences to prototypical bacterial SSBs
- 2024
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In: Life Science Alliance. - : Life Science Alliance. - 2575-1077. ; 7:8
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Journal article (peer-reviewed)abstract
- A major pathway for horizontal gene transfer is the transmission of DNA from donor to recipient cells via plasmid-encoded type IV secretion systems (T4SSs). Many conjugative plasmids encode for a single-stranded DNA-binding protein (SSB) together with their T4SS. Some of these SSBs have been suggested to aid in establishing the plasmid in the recipient cell, but for many, their function remains unclear. Here, we characterize PrgE, a proposed SSB from the Enterococcus faecalis plasmid pCF10. We show that PrgE is not essential for conjugation. Structurally, it has the characteristic OB-fold of SSBs, but it has very unusual DNA-binding properties. Our DNA-bound structure shows that PrgE binds ssDNA like beads on a string supported by its N-terminal tail. In vitro studies highlight the plasticity of PrgE oligomerization and confirm the importance of the N-terminus. Unlike other SSBs, PrgE binds both double- and single-stranded DNA equally well. This shows that PrgE has a quaternary assembly and DNA-binding properties that are very different from the prototypical bacterial SSB, but also different from eukaryotic SSBs.
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| 7. |
- Carvalho, Gustavo, et al.
(author)
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Mitochondrial DNA Instability in Mammalian Cells
- 2022
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In: Antioxidants and Redox Signaling. - : Mary Ann Liebert. - 1523-0864 .- 1557-7716. ; 36:13-15, s. 885-905
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Research review (peer-reviewed)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.
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| 8. |
- Gorospe, Choco Michael, et al.
(author)
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Determination of the ribonucleotide content of mtDNA using alkaline gels
- 2023
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In: Mitochondrial DNA. - New York : Humana Press. - 9781071629215 - 9781071629222 ; , s. 293-314
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Book chapter (peer-reviewed)abstract
- Impaired mitochondrial DNA (mtDNA) maintenance, due to, e.g., defects in the replication machinery or an insufficient dNTP supply, underlies a number of mitochondrial disorders. The normal process of mtDNA replication leads to the incorporation of multiple single ribonucleotides (rNMPs) per mtDNA molecule. Given that embedded rNMPs alter the stability and properties of the DNA, they may have consequences for mtDNA maintenance and thereby for mitochondrial disease. They also serve as a readout of the intramitochondrial NTP/dNTP ratios. In this chapter, we describe a method for the determination of mtDNA rNMP content using alkaline gel electrophoresis and Southern blotting. This procedure is suited for the analysis of mtDNA in total genomic DNA preparations as well as in purified form. Moreover, it can be performed using equipment found in most biomedical laboratories, allows the simultaneous analysis of 10-20 samples depending on the gel system employed, and can be modified for the analysis of other mtDNA modifications.
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| 9. |
- Gorospe, Choco Michael, et al.
(author)
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Mitochondrial membrane potential acts as a retrograde signal to regulate cell cycle progression
- 2023
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In: Life Science Alliance. - : Life Science Alliance, LLC. - 2575-1077. ; 6:12
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Journal article (peer-reviewed)abstract
- Mitochondria are central to numerous metabolic pathways whereby mitochondrial dysfunction has a profound impact and can manifest in disease. The consequences of mitochondrial dysfunction can be ameliorated by adaptive responses that rely on crosstalk from the mitochondria to the rest of the cell. Such mito-cellular signalling slows cell cycle progression in mitochondrial DNA-deficient (ρ0) Saccharomyces cerevisiae cells, but the initial trigger of the response has not been thoroughly studied. Here, we show that decreased mitochondrial membrane potential (ΔΨm) acts as the initial signal of mitochondrial stress that delays G1-to-S phase transition in both ρ0 and control cells containing mtDNA. Accordingly, experimentally increasing ΔΨm was sufficient to restore timely cell cycle progression in ρ0 cells. In contrast, cellular levels of oxidative stress did not correlate with the G1-to-S delay. Restored G1-to-S transition in ρ0 cells with a recovered ΔΨm is likely attributable to larger cell size, whereas the timing of G1/S transcription remained delayed. The identification of ΔΨm as a regulator of cell cycle progression may have implications for disease states involving mitochondrial dysfunction.
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| 10. |
- Nystrom, K., et al.
(author)
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Inosine triphosphate pyrophosphatase enhances the effect of ribavirin on hepatitis C virus cell culture infection
- 2017
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In: Journal of Hepatology. - : ELSEVIER SCIENCE BV. - 0168-8278 .- 1600-0641. ; 66:1, s. S321-S321
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Journal article (peer-reviewed)abstract
- Genetic variants of the inosine triphosphate pyrophosphatase gene (ITPA), resulting in decreased enzymatic activity of the corresponding enzyme, ITPase, are known to correlate with a decreased risk of ribavirin-induced anemia, but are also associated with an increased SVR in patients treated with peginterferon-alpha and ribavirin. As both ITPase and ribavirin are involved in the nucleotide salvage pathway and reduced risk of relapse after treatment of hepatitis C, we have investigated the effect of ITPase activity and ribavirin treatment of HCVcc infection of hepatocytes
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