1
|
Clement PC, Sapam T, Nair DT. A conserved polar residue plays a critical role in mismatch detection in A-family DNA polymerases. Int J Biol Macromol 2024; 269:131965. [PMID: 38697428 DOI: 10.1016/j.ijbiomac.2024.131965] [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: 01/29/2024] [Revised: 04/26/2024] [Accepted: 04/27/2024] [Indexed: 05/05/2024]
Abstract
In A-family DNA polymerases (dPols), a functional 3'-5' exonuclease activity is known to proofread newly synthesized DNA. The identification of a mismatch in substrate DNA leads to transfer of the primer strand from the polymerase active site to the exonuclease active site. To shed more light regarding the mechanism responsible for the detection of mismatches, we have utilized DNA polymerase 1 from Aquifex pyrophilus (ApPol1). The enzyme synthesized DNA with high fidelity and exhibited maximal exonuclease activity with DNA substrates bearing mismatches at the -2 and - 3 positions. The crystal structure of apo-ApPol1 was utilized to generate a computational model of the functional ternary complex of this enzyme. The analysis of the model showed that N332 forms interactions with minor groove atoms of the base pairs at the -2 and - 3 positions. The majority of known A-family dPols show the presence of Asn at a position equivalent to N332. The N332L mutation led to a decrease in the exonuclease activity for representative purine-pyrimidine, and pyrimidine-pyrimidine mismatches at -2 and - 3 positions, respectively. Overall, our findings suggest that conserved polar residues located towards the minor groove may facilitate the detection of position-specific mismatches to enhance the fidelity of DNA synthesis.
Collapse
Affiliation(s)
- Patterson C Clement
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121 001, Haryana (NCR Delhi), India
| | - Tuleshwori Sapam
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121 001, Haryana (NCR Delhi), India
| | - Deepak T Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121 001, Haryana (NCR Delhi), India.
| |
Collapse
|
2
|
Buchel G, Nayak AR, Herbine K, Sarfallah A, Sokolova VO, Zamudio-Ochoa A, Temiakov D. Structural basis for DNA proofreading. Nat Commun 2023; 14:8501. [PMID: 38151585 PMCID: PMC10752894 DOI: 10.1038/s41467-023-44198-8] [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: 08/03/2023] [Accepted: 12/04/2023] [Indexed: 12/29/2023] Open
Abstract
DNA polymerase (DNAP) can correct errors in DNA during replication by proofreading, a process critical for cell viability. However, the mechanism by which an erroneously incorporated base translocates from the polymerase to the exonuclease site and the corrected DNA terminus returns has remained elusive. Here, we present an ensemble of nine high-resolution structures representing human mitochondrial DNA polymerase Gamma, Polγ, captured during consecutive proofreading steps. The structures reveal key events, including mismatched base recognition, its dissociation from the polymerase site, forward translocation of DNAP, alterations in DNA trajectory, repositioning and refolding of elements for primer separation, DNAP backtracking, and displacement of the mismatched base into the exonuclease site. Altogether, our findings suggest a conserved 'bolt-action' mechanism of proofreading based on iterative cycles of DNAP translocation without dissociation from the DNA, facilitating primer transfer between catalytic sites. Functional assays and mutagenesis corroborate this mechanism, connecting pathogenic mutations to crucial structural elements in proofreading steps.
Collapse
Affiliation(s)
- Gina Buchel
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Ashok R Nayak
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Karl Herbine
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Azadeh Sarfallah
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Viktoriia O Sokolova
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Angelica Zamudio-Ochoa
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA
| | - Dmitry Temiakov
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 1020 Locust St, Philadelphia, PA, 19107, USA.
| |
Collapse
|
3
|
Betancurt-Anzola L, Martínez-Carranza M, Delarue M, Zatopek KM, Gardner AF, Sauguet L. Molecular basis for proofreading by the unique exonuclease domain of Family-D DNA polymerases. Nat Commun 2023; 14:8306. [PMID: 38097591 PMCID: PMC10721889 DOI: 10.1038/s41467-023-44125-x] [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: 08/09/2023] [Accepted: 11/30/2023] [Indexed: 12/17/2023] Open
Abstract
Replicative DNA polymerases duplicate entire genomes at high fidelity. This feature is shared among the three domains of life and is facilitated by their dual polymerase and exonuclease activities. Family D replicative DNA polymerases (PolD), found exclusively in Archaea, contain an unusual RNA polymerase-like catalytic core, and a unique Mre11-like proofreading active site. Here, we present cryo-EM structures of PolD trapped in a proofreading mode, revealing an unanticipated correction mechanism that extends the repertoire of protein domains known to be involved in DNA proofreading. Based on our experimental structures, mutants of PolD were designed and their contribution to mismatch bypass and exonuclease kinetics was determined. This study sheds light on the convergent evolution of structurally distinct families of DNA polymerases, and the domain acquisition and exchange mechanism that occurred during the evolution of the replisome in the three domains of life.
Collapse
Affiliation(s)
- Leonardo Betancurt-Anzola
- Architecture and Dynamics of Biological Macromolecules, Institut Pasteur, Université Paris Cité, CNRS, UMR 3528, Paris, France
- New England Biolabs Inc., 240 County Road, Ipswich, MA, 01938, USA
- New England Biolabs France, 5 Rue Henri Auguste Desbruères, 91000, Évry-Courcouronnes, France
- Sorbonne Université, Collège Doctoral, ED 515, Paris, France
| | - Markel Martínez-Carranza
- Architecture and Dynamics of Biological Macromolecules, Institut Pasteur, Université Paris Cité, CNRS, UMR 3528, Paris, France
| | - Marc Delarue
- Architecture and Dynamics of Biological Macromolecules, Institut Pasteur, Université Paris Cité, CNRS, UMR 3528, Paris, France
| | - Kelly M Zatopek
- New England Biolabs Inc., 240 County Road, Ipswich, MA, 01938, USA.
| | - Andrew F Gardner
- New England Biolabs Inc., 240 County Road, Ipswich, MA, 01938, USA.
| | - Ludovic Sauguet
- Architecture and Dynamics of Biological Macromolecules, Institut Pasteur, Université Paris Cité, CNRS, UMR 3528, Paris, France.
| |
Collapse
|
4
|
Park J, Herrmann GK, Mitchell PG, Sherman MB, Yin YW. Polγ coordinates DNA synthesis and proofreading to ensure mitochondrial genome integrity. Nat Struct Mol Biol 2023; 30:812-823. [PMID: 37202477 PMCID: PMC10920075 DOI: 10.1038/s41594-023-00980-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 03/28/2023] [Indexed: 05/20/2023]
Abstract
Accurate replication of mitochondrial DNA (mtDNA) by DNA polymerase γ (Polγ) is essential for maintaining cellular energy supplies, metabolism, and cell cycle control. To illustrate the structural mechanism for Polγ coordinating polymerase (pol) and exonuclease (exo) activities to ensure rapid and accurate DNA synthesis, we determined four cryo-EM structures of Polγ captured after accurate or erroneous incorporation to a resolution of 2.4-3.0 Å. The structures show that Polγ employs a dual-checkpoint mechanism to sense nucleotide misincorporation and initiate proofreading. The transition from replication to error editing is accompanied by increased dynamics in both DNA and enzyme, in which the polymerase relaxes its processivity and the primer-template DNA unwinds, rotates, and backtracks to shuttle the mismatch-containing primer terminus 32 Å to the exo site for editing. Our structural and functional studies also provide a foundation for analyses of Polγ mutation-induced human diseases and aging.
Collapse
Affiliation(s)
- Joon Park
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA
| | - Geoffrey K Herrmann
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA
| | - Patrick G Mitchell
- Division of CryoEM and Bioimaging, Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center National Accelerator Laboratory, Stanford University, Menlo Park, CA, USA
| | - Michael B Sherman
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA
| | - Y Whitney Yin
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA.
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA.
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA.
| |
Collapse
|
5
|
Plaza-G A I, Lemishko KM, Crespo R, Truong TQ, Kaguni LS, Cao-García FJ, Ciesielski GL, Ibarra B. Mechanism of strand displacement DNA synthesis by the coordinated activities of human mitochondrial DNA polymerase and SSB. Nucleic Acids Res 2023; 51:1750-1765. [PMID: 36744436 PMCID: PMC9976888 DOI: 10.1093/nar/gkad037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 12/16/2022] [Accepted: 01/12/2023] [Indexed: 02/07/2023] Open
Abstract
Many replicative DNA polymerases couple DNA replication and unwinding activities to perform strand displacement DNA synthesis, a critical ability for DNA metabolism. Strand displacement is tightly regulated by partner proteins, such as single-stranded DNA (ssDNA) binding proteins (SSBs) by a poorly understood mechanism. Here, we use single-molecule optical tweezers and biochemical assays to elucidate the molecular mechanism of strand displacement DNA synthesis by the human mitochondrial DNA polymerase, Polγ, and its modulation by cognate and noncognate SSBs. We show that Polγ exhibits a robust DNA unwinding mechanism, which entails lowering the energy barrier for unwinding of the first base pair of the DNA fork junction, by ∼55%. However, the polymerase cannot prevent the reannealing of the parental strands efficiently, which limits by ∼30-fold its strand displacement activity. We demonstrate that SSBs stimulate the Polγ strand displacement activity through several mechanisms. SSB binding energy to ssDNA additionally increases the destabilization energy at the DNA junction, by ∼25%. Furthermore, SSB interactions with the displaced ssDNA reduce the DNA fork reannealing pressure on Polγ, in turn promoting the productive polymerization state by ∼3-fold. These stimulatory effects are enhanced by species-specific functional interactions and have significant implications in the replication of the human mitochondrial DNA.
Collapse
Affiliation(s)
- Ismael Plaza-G A
- Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia, Faraday 9, 28049 Madrid, Spain
| | - Kateryna M Lemishko
- Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia, Faraday 9, 28049 Madrid, Spain
| | - Rodrigo Crespo
- Departamento de Estructura de la Materia, Física Térmica y Electrónica, Universidad Complutense de Madrid, Pza. de Ciencias, 1, 28040 Madrid, Spain
| | - Thinh Q Truong
- Department of Chemistry, Auburn University at Montgomery, Montgomery, AL 36117, USA
| | - Laurie S Kaguni
- Department of Biochemistry and Molecular Biology and Center for Mitochondrial Science and Medicine, Michigan State University, East Lansing, MI 48823, USA
| | - Francisco J Cao-García
- Departamento de Estructura de la Materia, Física Térmica y Electrónica, Universidad Complutense de Madrid, Pza. de Ciencias, 1, 28040 Madrid, Spain
| | - Grzegorz L Ciesielski
- Department of Chemistry, Auburn University at Montgomery, Montgomery, AL 36117, USA.,Department of Biochemistry and Molecular Biology and Center for Mitochondrial Science and Medicine, Michigan State University, East Lansing, MI 48823, USA
| | - Borja Ibarra
- Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia, Faraday 9, 28049 Madrid, Spain.,Nanobiotecnología (IMDEA-Nanociencia), Unidad Asociada al Centro Nacional de Biotecnología (CSIC), 28049 Madrid, Spain
| |
Collapse
|
6
|
Park J, Baruch-Torres N, Yin YW. Structural and Molecular Basis for Mitochondrial DNA Replication and Transcription in Health and Antiviral Drug Toxicity. Molecules 2023; 28:1796. [PMID: 36838782 PMCID: PMC9961925 DOI: 10.3390/molecules28041796] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 02/06/2023] [Accepted: 02/09/2023] [Indexed: 02/17/2023] Open
Abstract
Human mitochondrial DNA (mtDNA) is a 16.9 kbp double-stranded, circular DNA, encoding subunits of the oxidative phosphorylation electron transfer chain and essential RNAs for mitochondrial protein translation. The minimal human mtDNA replisome is composed of the DNA helicase Twinkle, DNA polymerase γ, and mitochondrial single-stranded DNA-binding protein. While the mitochondrial RNA transcription is carried out by mitochondrial RNA polymerase, mitochondrial transcription factors TFAM and TFB2M, and a transcription elongation factor, TEFM, both RNA transcriptions, and DNA replication machineries are intertwined and control mtDNA copy numbers, cellular energy supplies, and cellular metabolism. In this review, we discuss the mechanisms governing these main pathways and the mtDNA diseases that arise from mutations in transcription and replication machineries from a structural point of view. We also address the adverse effect of antiviral drugs mediated by mitochondrial DNA and RNA polymerases as well as possible structural approaches to develop nucleoside reverse transcriptase inhibitor and ribonucleosides analogs with reduced toxicity.
Collapse
Affiliation(s)
- Joon Park
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
- Department of Pharmacology and Toxicology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Noe Baruch-Torres
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
- Department of Pharmacology and Toxicology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Y. Whitney Yin
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
- Department of Pharmacology and Toxicology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
| |
Collapse
|
7
|
Delzell S, Nelson SW, Frost MP, Klingbeil MM. Trypanosoma brucei Mitochondrial DNA Polymerase POLIB Contains a Novel Polymerase Domain Insertion That Confers Dominant Exonuclease Activity. Biochemistry 2022; 61:2751-2765. [PMID: 36399653 PMCID: PMC9731263 DOI: 10.1021/acs.biochem.2c00392] [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: 07/01/2022] [Revised: 10/31/2022] [Indexed: 11/19/2022]
Abstract
Trypanosoma brucei and related parasites contain an unusual catenated mitochondrial genome known as kinetoplast DNA (kDNA) composed of maxicircles and minicircles. The kDNA structure and replication mechanism are divergent and essential for parasite survival. POLIB is one of three Family A DNA polymerases independently essential to maintain the kDNA network. However, the division of labor among the paralogs, particularly which might be a replicative, proofreading enzyme, remains enigmatic. De novo modeling of POLIB suggested a structure that is divergent from all other Family A polymerases, in which the thumb subdomain contains a 369 amino acid insertion with homology to DEDDh DnaQ family 3'-5' exonucleases. Here we demonstrate recombinant POLIB 3'-5' exonuclease prefers DNA vs RNA substrates and degrades single- and double-stranded DNA nonprocessively. Exonuclease activity prevails over polymerase activity on DNA substrates at pH 8.0, while DNA primer extension is favored at pH 6.0. Mutations that ablate POLIB polymerase activity slow the exonuclease rate suggesting crosstalk between the domains. We show that POLIB extends an RNA primer more efficiently than a DNA primer in the presence of dNTPs but does not incorporate rNTPs efficiently using either primer. Immunoprecipitation of Pol I-like paralogs from T. brucei corroborates the pH selectivity and RNA primer preferences of POLIB and revealed that the other paralogs efficiently extend a DNA primer. The enzymatic properties of POLIB suggest this paralog is not a replicative kDNA polymerase, and the noncanonical polymerase domain provides another example of exquisite diversity among DNA polymerases for specialized function.
Collapse
Affiliation(s)
- Stephanie
B. Delzell
- Department
of Microbiology, University of Massachusetts, Amherst, Massachusetts01003, United States
| | - Scott W. Nelson
- Roy
J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa50011, United States
| | - Matthew P. Frost
- Department
of Microbiology, University of Massachusetts, Amherst, Massachusetts01003, United States
| | - Michele M. Klingbeil
- Department
of Microbiology, University of Massachusetts, Amherst, Massachusetts01003, United States
- The
Institute for Applied Life Sciences, University
of Massachusetts, Amherst, Massachusetts01003, United States
| |
Collapse
|
8
|
Kinetics of DNA strand transfer between polymerase and proofreading exonuclease active sites regulates error correction during high-fidelity replication. J Biol Chem 2022; 299:102744. [PMID: 36436560 PMCID: PMC9800556 DOI: 10.1016/j.jbc.2022.102744] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 11/18/2022] [Accepted: 11/20/2022] [Indexed: 11/25/2022] Open
Abstract
We show that T7 DNA polymerase (pol) and exonuclease (exo) domains contribute to selective error correction during DNA replication by regulating bidirectional strand transfer between the two active sites. To explore the kinetic basis for selective removal of mismatches, we used a fluorescent cytosine analog (1,3-diaza-2-oxophenoxazine) to monitor the kinetics of DNA transfer between the exo and pol sites. We globally fit stopped-flow fluorescence and base excision kinetic data and compared results obtained with ssDNA versus duplex DNA to resolve how DNA transfer governs exo specificity. We performed parallel studies using hydrolysis-resistant phosphorothioate oligonucleotides to monitor DNA transfer to the exo site without hydrolysis. ssDNA binds to the exo site at the diffusion limit (109 M-1 s-1, Kd = 40 nM) followed by fast hydrolysis of the 3'-terminal nucleotide (>5000 s-1). Analysis using duplex DNA with a 3'-terminal mismatch or a buried mismatch exposed a unique intermediate state between pol and exo active sites and revealed that transfer via the intermediate to the exo site is stimulated by free nucleoside triphosphates. Transfer from the exo site back to the pol site after cleavage is fast and efficient. We propose a model to explain why buried mismatches are removed faster than single 3'-terminal mismatches and thereby provide an additional opportunity for error correction. Our data provide the first comprehensive model to explain how DNA transfer from pol to exo active sites and back again after base excision allow efficient selective mismatch removal during DNA replication to improve fidelity by more than 1000-fold.
Collapse
|
9
|
Desquiret-Dumas V, D’Ottavi M, Monnin A, Goudenège D, Méda N, Vizeneux A, Kankasa C, Tylleskar T, Bris C, Procaccio V, Nagot N, Van de Perre P, Reynier P, Molès JP. Long-Term Persistence of Mitochondrial DNA Instability in HIV-Exposed Uninfected Children during and after Exposure to Antiretroviral Drugs and HIV. Biomedicines 2022; 10:biomedicines10081786. [PMID: 35892686 PMCID: PMC9331317 DOI: 10.3390/biomedicines10081786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/18/2022] [Accepted: 07/20/2022] [Indexed: 11/16/2022] Open
Abstract
HIV-exposed uninfected (HEU) children show impaired health outcomes during childhood. A high rate of mitochondrial DNA (mtDNA) instability was reported in the blood of HEU at birth. We aimed to explore the relationship between these health outcomes and mtDNA deletions over time in a case series of 24 HEU children. MtDNA instability was assessed by deep sequencing and analyzed by eKLIPse-v2 algorithm at three time points, namely birth, 1 year, and 6 years of age. Association between mtDNA deletion and health outcomes, including growth, clinical, and neurodevelopmental parameters, were explored using univariate statistical analyses and after stratification with relevant variables. HEU children were selected with an equal male:female ratio. An elevated number of mtDNA deletions and duplications events was observed at 7 days’ post-partum. Median heteroplasmy increased at one year of life and then returned to baseline by six years of age. The mtDNA instability was acquired and was not transmitted by the mother. No risk factors were significantly associated with mtDNA instability. In this small case series, we did not detect any association between any health outcome at 6 years and mtDNA instability measures. A significant effect modification of the association between the duration of maternal prophylaxis and child growth was observed after stratification with heteroplasmy rate. Genomic instability persists over time among HEU children but, despite its extension, stays subclinical at six years.
Collapse
Affiliation(s)
- Valérie Desquiret-Dumas
- Department of Biochemistry and Genetics, University Hospital of Angers, F-49000 Angers, France; (V.D.-D.); (D.G.); (C.B.); (V.P.); (P.R.)
- UMR MITOVASC, CNRS 6015, INSERM U1083, University of Angers, F-49000 Angers, France
| | - Morgana D’Ottavi
- Pathogenesis and Control of Chronic and Emerging Infections, INSERM, Etablissement Français du Sang, University of Montpellier, University of Antilles, F-34394 Montpellier, France; (M.D.); (A.M.); (A.V.); (N.N.); (P.V.d.P.)
| | - Audrey Monnin
- Pathogenesis and Control of Chronic and Emerging Infections, INSERM, Etablissement Français du Sang, University of Montpellier, University of Antilles, F-34394 Montpellier, France; (M.D.); (A.M.); (A.V.); (N.N.); (P.V.d.P.)
| | - David Goudenège
- Department of Biochemistry and Genetics, University Hospital of Angers, F-49000 Angers, France; (V.D.-D.); (D.G.); (C.B.); (V.P.); (P.R.)
- UMR MITOVASC, CNRS 6015, INSERM U1083, University of Angers, F-49000 Angers, France
| | - Nicolas Méda
- Centre MURAZ, Bobo-Dioulasso 01 B.P. 390, Burkina Faso;
| | - Amélie Vizeneux
- Pathogenesis and Control of Chronic and Emerging Infections, INSERM, Etablissement Français du Sang, University of Montpellier, University of Antilles, F-34394 Montpellier, France; (M.D.); (A.M.); (A.V.); (N.N.); (P.V.d.P.)
| | - Chipepo Kankasa
- Department of Paediatrics and Child Health, University Teaching Hospital, Lusaka P.O. Box 50001, Zambia;
| | - Thorkild Tylleskar
- Centre for International Health, University of Bergen, N-5020 Bergen, Norway;
| | - Céline Bris
- Department of Biochemistry and Genetics, University Hospital of Angers, F-49000 Angers, France; (V.D.-D.); (D.G.); (C.B.); (V.P.); (P.R.)
- UMR MITOVASC, CNRS 6015, INSERM U1083, University of Angers, F-49000 Angers, France
| | - Vincent Procaccio
- Department of Biochemistry and Genetics, University Hospital of Angers, F-49000 Angers, France; (V.D.-D.); (D.G.); (C.B.); (V.P.); (P.R.)
- UMR MITOVASC, CNRS 6015, INSERM U1083, University of Angers, F-49000 Angers, France
| | - Nicolas Nagot
- Pathogenesis and Control of Chronic and Emerging Infections, INSERM, Etablissement Français du Sang, University of Montpellier, University of Antilles, F-34394 Montpellier, France; (M.D.); (A.M.); (A.V.); (N.N.); (P.V.d.P.)
| | - Philippe Van de Perre
- Pathogenesis and Control of Chronic and Emerging Infections, INSERM, Etablissement Français du Sang, University of Montpellier, University of Antilles, F-34394 Montpellier, France; (M.D.); (A.M.); (A.V.); (N.N.); (P.V.d.P.)
| | - Pascal Reynier
- Department of Biochemistry and Genetics, University Hospital of Angers, F-49000 Angers, France; (V.D.-D.); (D.G.); (C.B.); (V.P.); (P.R.)
- UMR MITOVASC, CNRS 6015, INSERM U1083, University of Angers, F-49000 Angers, France
| | - Jean-Pierre Molès
- Pathogenesis and Control of Chronic and Emerging Infections, INSERM, Etablissement Français du Sang, University of Montpellier, University of Antilles, F-34394 Montpellier, France; (M.D.); (A.M.); (A.V.); (N.N.); (P.V.d.P.)
- Correspondence: ; Tel.: +33-434-35-91-07
| |
Collapse
|
10
|
Wu Q, Tsai HI, Zhu H, Wang D. The Entanglement between Mitochondrial DNA and Tumor Metastasis. Cancers (Basel) 2022; 14:cancers14081862. [PMID: 35454769 PMCID: PMC9028275 DOI: 10.3390/cancers14081862] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Revised: 03/31/2022] [Accepted: 04/01/2022] [Indexed: 02/04/2023] Open
Abstract
Simple Summary Mitochondrial dysfunction is one of the main features of cancer cells. As genetic material in mitochondria, mitochondrial DNA (mtDNA) variations and dysregulation of mitochondria-encoded genes have been shown to correlate with survival outcomes in cancer patients. Cancer metastasis is often a major cause of treatment failure, which is a multi-step cascade process. With the development of gene sequencing and in vivo modeling technology, the role of mtDNA in cancer metastasis has been continuously explored. Our review systematically provides a summary of the multiple roles of mtDNA in cancer metastasis and presents the broad prospects for mtDNA in cancer prediction and therapy. Abstract Mitochondrial DNA, the genetic material in mitochondria, encodes essential oxidative phosphorylation proteins and plays an important role in mitochondrial respiration and energy transfer. With the development of genome sequencing and the emergence of novel in vivo modeling techniques, the role of mtDNA in cancer biology is gaining more attention. Abnormalities of mtDNA result in not only mitochondrial dysfunction of the the cancer cells and malignant behaviors, but regulation of the tumor microenvironment, which becomes more aggressive. Here, we review the recent progress in the regulation of cancer metastasis using mtDNA and the underlying mechanisms, which may identify opportunities for finding novel cancer prediction and therapeutic targets.
Collapse
Affiliation(s)
- Qiwei Wu
- 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;
| | - 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;
- Correspondence: (H.Z.); (D.W.); Tel.: +86-138-6139-0259 (D.W.)
| | - Dongqing Wang
- Department of Medical Imaging, The Affiliated Hospital of Jiangsu University, Zhenjiang 212001, China;
- Correspondence: (H.Z.); (D.W.); Tel.: +86-138-6139-0259 (D.W.)
| |
Collapse
|
11
|
Park J, Baruch-Torres N, Iwai S, Herrmann GK, Brieba LG, Yin YW. Human Mitochondrial DNA Polymerase Metal Dependent UV Lesion Bypassing Ability. Front Mol Biosci 2022; 9:808036. [PMID: 35355510 PMCID: PMC8959595 DOI: 10.3389/fmolb.2022.808036] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 01/11/2022] [Indexed: 12/11/2022] Open
Abstract
Human mitochondrial DNA contains more UV-induced lesions than the nuclear DNA due to lack of mechanism to remove bulky photoproducts. Human DNA polymerase gamma (Pol γ) is the sole DNA replicase in mitochondria, which contains a polymerase (pol) and an exonuclease (exo) active site. Previous studies showed that Pol γ only displays UV lesion bypassing when its exonuclease activity is obliterated. To investigate the reaction environment on Pol γ translesion activity, we tested Pol γ DNA activity in the presence of different metal ions. While Pol γ is unable to replicate through UV lesions on DNA templates in the presence of Mg2+, it exhibits robust translesion DNA synthesis (TLS) on cyclobutane pyrimidine dimer (CPD)-containing template when Mg2+ was mixed with or completely replaced by Mn2+. Under these conditions, the efficiency of Pol γ′s TLS opposite CPD is near to that on a non-damaged template and is 800-fold higher than that of exonuclease-deficient Pol γ. Interestingly, Pol γ exhibits higher exonuclease activity in the presence of Mn2+ than with Mg2+, suggesting Mn2+-stimulated Pol γ TLS is not via suppressing its exonuclease activity. We suggest that Mn2+ ion expands Pol γ′s pol active site relative to Mg2+ so that a UV lesion can be accommodated and blocks the communication between pol and exo active sites to execute translesion DNA synthesis.
Collapse
Affiliation(s)
- Joon Park
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, United States
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, United States
| | - Noe Baruch-Torres
- Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Mexico
| | - Shigenori Iwai
- Division of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Japan
| | - Geoffrey K. Herrmann
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, United States
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, United States
| | - Luis G. Brieba
- Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Mexico
- *Correspondence: Luis G. Brieba, ; Y. Whitney Yin,
| | - Y. Whitney Yin
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, United States
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, United States
- *Correspondence: Luis G. Brieba, ; Y. Whitney Yin,
| |
Collapse
|
12
|
Dangerfield TL, Kirmizialtin S, Johnson KA. Substrate specificity and proposed structure of the proofreading complex of T7 DNA polymerase. J Biol Chem 2022; 298:101627. [PMID: 35074426 PMCID: PMC8867116 DOI: 10.1016/j.jbc.2022.101627] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 01/18/2022] [Accepted: 01/19/2022] [Indexed: 11/25/2022] Open
Abstract
Faithful replication of genomic DNA by high-fidelity DNA polymerases is crucial for the survival of most living organisms. While high-fidelity DNA polymerases favor canonical base pairs over mismatches by a factor of ∼1 × 105, fidelity is further enhanced several orders of magnitude by a 3′–5′ proofreading exonuclease that selectively removes mispaired bases in the primer strand. Despite the importance of proofreading to maintaining genome stability, it remains much less studied than the fidelity mechanisms employed at the polymerase active site. Here we characterize the substrate specificity for the proofreading exonuclease of a high-fidelity DNA polymerase by investigating the proofreading kinetics on various DNA substrates. The contribution of the exonuclease to net fidelity is a function of the kinetic partitioning between extension and excision. We show that while proofreading of a terminal mismatch is efficient, proofreading a mismatch buried by one or two correct bases is even more efficient. Because the polymerase stalls after incorporation of a mismatch and after incorporation of one or two correct bases on top of a mismatch, the net contribution of the exonuclease is a function of multiple opportunities to correct mistakes. We also characterize the exonuclease stereospecificity using phosphorothioate-modified DNA, provide a homology model for the DNA primer strand in the exonuclease active site, and propose a dynamic structural model for the transfer of DNA from the polymerase to the exonuclease active site based on MD simulations.
Collapse
Affiliation(s)
- Tyler L Dangerfield
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas, USA
| | - Serdal Kirmizialtin
- Chemistry Program, Science Division, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
| | - Kenneth A Johnson
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas, USA.
| |
Collapse
|
13
|
Duan K, Gu Q, Petralia RS, Wang YX, Panja D, Liu X, Lehmann ML, Zhu H, Zhu J, Li Z. Mitophagy in the basolateral amygdala mediates increased anxiety induced by aversive social experience. Neuron 2021; 109:3793-3809.e8. [PMID: 34614419 PMCID: PMC8639775 DOI: 10.1016/j.neuron.2021.09.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 06/09/2021] [Accepted: 09/08/2021] [Indexed: 01/16/2023]
Abstract
Psychosocial stress is a common risk factor for anxiety disorders. The cellular mechanism for the anxiogenic effect of psychosocial stress is largely unclear. Here, we show that chronic social defeat (CSD) stress in mice causes mitochondrial impairment, which triggers the PINK1-Parkin mitophagy pathway selectively in the amygdala. This mitophagy elevation causes excessive mitochondrial elimination and consequent mitochondrial deficiency. Mitochondrial deficiency in the basolateral amygdalae (BLA) causes weakening of synaptic transmission in the BLA-BNST (bed nucleus of the stria terminalis) anxiolytic pathway and increased anxiety. The CSD-induced increase in anxiety-like behaviors is abolished in Pink1-/- and Park2-/- mice and alleviated by optogenetic activation of the BLA-BNST synapse. This study identifies an unsuspected role of mitophagy in psychogenetic-stress-induced anxiety elevation and reveals that mitochondrial deficiency is sufficient to increase anxiety and underlies the psychosocial-stress-induced anxiety increase. Mitochondria and mitophagy, therefore, can be potentially targeted to ameliorate anxiety.
Collapse
Affiliation(s)
- Kaizheng Duan
- Section on Synapse Development Plasticity, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Qinhua Gu
- Section on Synapse Development Plasticity, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ronald S Petralia
- Advanced Imaging Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ya-Xian Wang
- Advanced Imaging Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Debabrata Panja
- Section on Synapse Development Plasticity, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Xing Liu
- Section on Synapse Development Plasticity, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Michael L Lehmann
- Section on Functional Neuroanatomy, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Huiwen Zhu
- Section on Synapse Development Plasticity, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jun Zhu
- Systems Biology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Zheng Li
- Section on Synapse Development Plasticity, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA.
| |
Collapse
|
14
|
Ciesielska EJ, Kim S, Bisimwa HGM, Grier C, Rahman MM, Young CKJ, Young MJ, Oliveira MT, Ciesielski GL. Remdesivir triphosphate blocks DNA synthesis and increases exonucleolysis by the replicative mitochondrial DNA polymerase, Pol γ. Mitochondrion 2021; 61:147-158. [PMID: 34619353 PMCID: PMC8595818 DOI: 10.1016/j.mito.2021.09.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 09/16/2021] [Accepted: 09/22/2021] [Indexed: 01/18/2023]
Abstract
The COVID-19 pandemic prompted the FDA to authorize a new nucleoside analogue, remdesivir, for emergency use in affected individuals. We examined the effects of its active metabolite, remdesivir triphosphate (RTP), on the activity of the replicative mitochondrial DNA polymerase, Pol γ. We found that while RTP is not incorporated by Pol γ into a nascent DNA strand, it remains associated with the enzyme impeding its synthetic activity and stimulating exonucleolysis. In spite of that, we found no evidence for deleterious effects of remdesivir treatment on the integrity of the mitochondrial genome in human cells in culture.
Collapse
Affiliation(s)
- Elena J Ciesielska
- Department of Chemistry, Auburn University at Montgomery, Montgomery, AL 36117, United States
| | - Shalom Kim
- Department of Chemistry, Auburn University at Montgomery, Montgomery, AL 36117, United States
| | | | - Cody Grier
- Department of Chemistry, Auburn University at Montgomery, Montgomery, AL 36117, United States
| | - Md Mostafijur Rahman
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, IL 62901, United States
| | - Carolyn K J Young
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, IL 62901, United States
| | - Matthew J Young
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, IL 62901, United States
| | - Marcos T Oliveira
- Departamento de Tecnologia, Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista "Júlio de Mesquita Filho", Jaboticabal, SP, Brazil
| | - Grzegorz L Ciesielski
- Department of Chemistry, Auburn University at Montgomery, Montgomery, AL 36117, United States.
| |
Collapse
|
15
|
Lim EW, Handzlik MK, Trefts E, Gengatharan JM, Pondevida CM, Shaw RJ, Metallo CM. Progressive alterations in amino acid and lipid metabolism correlate with peripheral neuropathy in PolgD257A mice. SCIENCE ADVANCES 2021; 7:eabj4077. [PMID: 34652935 PMCID: PMC8519573 DOI: 10.1126/sciadv.abj4077] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 08/24/2021] [Indexed: 05/03/2023]
Abstract
Mitochondria are central to metabolic homeostasis, and progressive mitochondrial defects have diverse metabolic consequences that could drive distinct pathophysiological states. Here, we comprehensively characterized metabolic alterations in PolgD257A mice. Plasma alanine increased markedly with time, with other organic acids accumulating to a lesser extent. These changes were reflective of increased Cori and Cahill cycling in PolgD257A mice and subsequent hypoglycemia, which did not occur during normal mouse aging. Tracing with [15N]ammonium further supported this shift in amino acid metabolism with mild impairment of the urea cycle. We also measured alterations in the lipidome, observing a reduction in canonical lipids and accumulation of 1-deoxysphingolipids, which are synthesized from alanine via promiscuous serine palmitoyltransferase activity and correlate with peripheral neuropathy. Consistent with this metabolic link, PolgD257A mice exhibited thermal hypoalgesia. These results highlight the longitudinal changes that occur in intermediary metabolism upon mitochondrial impairment and identify a contributing mechanism to mitochondria-associated neuropathy.
Collapse
Affiliation(s)
- Esther W. Lim
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093, USA
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
| | - Michal K. Handzlik
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093, USA
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
| | - Elijah Trefts
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
| | - Jivani M. Gengatharan
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093, USA
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
| | - Carlos M. Pondevida
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093, USA
| | - Reuben J. Shaw
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
| | - Christian M. Metallo
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093, USA
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
| |
Collapse
|
16
|
Li QS, Shu YG, Ou-Yang ZC, Li M. Kinetic assays of DNA polymerase fidelity: A theoretical perspective beyond Michaelis-Menten kinetics. Phys Rev E 2021; 104:014408. [PMID: 34412358 DOI: 10.1103/physreve.104.014408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 06/23/2021] [Indexed: 11/07/2022]
Abstract
The high fidelity of DNA polymerase (DNAP) is critical for the faithful replication of DNA. There are several quantitative approaches to measure DNAP fidelity. Directly counting the error frequency in the replication products gives the true fidelity but it turns out very hard to implement in practice. Two biochemical kinetic approaches, the steady-state assay and the transient-state assay, were then suggested and widely adopted. In these assays, the error frequency is indirectly estimated by using kinetic theories combined with the measured apparent kinetic rates. However, whether it is equivalent to the true fidelity has never been clarified theoretically, and in particular there are different strategies using these assays to quantify the proofreading efficiency of DNAP but often lead to inconsistent results. In this paper, we make a comprehensive examination on the theoretical foundation of the two kinetic assays, based on the theory of DNAP fidelity recently proposed by us. Our studies show that while the conventional kinetic assays are generally valid to quantify the discrimination efficiency of DNAP, they are valid to quantify the proofreading efficiency of DNAP only when the kinetic parameters satisfy some constraints which will be given explicitly in this paper. These results may inspire more carefully-designed experiments to quantify DNAP fidelity.
Collapse
Affiliation(s)
- Qiu-Shi Li
- School of Physical Science, University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Shijingshan District, Beijing 101400, People's Republic of China
| | - Yao-Gen Shu
- Wenzhou Institute, University of Chinese Academy of Sciences, No 1, Jinlian Road, Longwan District, Wenzhou, Zhejiang 325000, People's Republic of China
| | - Zhong-Can Ou-Yang
- Institute of Theoretical Physics, Chinese Academy of Sciences, Zhong Guan Cun East Street 55, P. O. Box 2735, Beijing 100190, People's Republic of China
| | - Ming Li
- School of Physical Science, University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Shijingshan District, Beijing 101400, People's Republic of China
| |
Collapse
|
17
|
Mitochondrial DNA Instability Is Common in HIV-Exposed Uninfected Newborns. J Clin Med 2021; 10:jcm10112399. [PMID: 34071681 PMCID: PMC8197798 DOI: 10.3390/jcm10112399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 05/25/2021] [Indexed: 01/13/2023] Open
Abstract
Worldwide, one million HIV-exposed uninfected (HEU) children are born yearly, and chronic health impairments have been reported in these children. Mitochondrial DNA (mtDNA) instability and altered mtDNA content have been evidenced in these children, but an exhaustive characterization of altered mitochondrial genomes has never been reported. We applied deep mtDNA sequencing coupled to the deletion identification algorithm eKLIPse to the blood of HEU neonates (n = 32), which was compared with healthy controls (n = 15). Dried blood spots (DBS) from African HEU children were collected seven days after birth between November 2009 and May 2012. DBS from French healthy controls were collected at birth (or <3 days of life) in 2012 and in 2019. In contrast to the absence of mtDNA instability observed at the nucleotide level, we identified significant amounts of heteroplasmic mtDNA deletions in 75% of HEU children and in none of controls. The heteroplasmy rate of the 62 mtDNA deletions identified varied from 0.01% to up to 50%, the highest rates being broadly compatible with bioenergetic defect and clinical expression. mtDNA integrity is commonly affected in HEU neonates. The nature of the deletions suggests a mechanism related to aging or tumor-associated mtDNA instability. This child population may be at risk of additional mtDNA genetic alterations considering that they will be exposed to other mitotoxic drugs including antiretroviral or anti-tuberculosis treatment.
Collapse
|
18
|
Bravo JPK, Dangerfield TL, Taylor DW, Johnson KA. Remdesivir is a delayed translocation inhibitor of SARS-CoV-2 replication. Mol Cell 2021; 81:1548-1552.e4. [PMID: 33631104 PMCID: PMC7843106 DOI: 10.1016/j.molcel.2021.01.035] [Citation(s) in RCA: 89] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 01/16/2021] [Accepted: 01/22/2021] [Indexed: 01/18/2023]
Abstract
Remdesivir is a nucleoside analog approved by the US FDA for treatment of COVID-19. Here, we present a 3.9-Å-resolution cryo-EM reconstruction of a remdesivir-stalled RNA-dependent RNA polymerase complex, revealing full incorporation of 3 copies of remdesivir monophosphate (RMP) and a partially incorporated fourth RMP in the active site. The structure reveals that RMP blocks RNA translocation after incorporation of 3 bases following RMP, resulting in delayed chain termination, which can guide the rational design of improved antiviral drugs.
Collapse
Affiliation(s)
- Jack P K Bravo
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA
| | - Tyler L Dangerfield
- Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - David W Taylor
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA; Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA; Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, TX 78712, USA; LIVESTRONG Cancer Institutes, Dell Medical School, Austin, TX 78712, USA.
| | - Kenneth A Johnson
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA; Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
| |
Collapse
|
19
|
MITOL-dependent ubiquitylation negatively regulates the entry of PolγA into mitochondria. PLoS Biol 2021; 19:e3001139. [PMID: 33657094 PMCID: PMC7959396 DOI: 10.1371/journal.pbio.3001139] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 03/15/2021] [Accepted: 02/04/2021] [Indexed: 02/01/2023] Open
Abstract
Mutations in mitochondrial replicative polymerase PolγA lead to progressive external ophthalmoplegia (PEO). While PolγA is the known central player in mitochondrial DNA (mtDNA) replication, it is unknown whether a regulatory process exists on the mitochondrial outer membrane which controlled its entry into the mitochondria. We now demonstrate that PolγA is ubiquitylated by mitochondrial E3 ligase, MITOL (or MARCH5, RNF153). Ubiquitylation in wild-type (WT) PolγA occurs at Lysine 1060 residue via K6 linkage. Ubiquitylation of PolγA negatively regulates its binding to Tom20 and thereby its mitochondrial entry. While screening different PEO patients for mitochondrial entry, we found that a subset of the PolγA mutants is hyperubiquitylated by MITOL and interact less with Tom20. These PolγA variants cannot enter into mitochondria, instead becomes enriched in the insoluble fraction and undergo enhanced degradation. Hence, mtDNA replication, as observed via BrdU incorporation into the mtDNA, was compromised in these PEO mutants. However, by manipulating their ubiquitylation status by 2 independent techniques, these PEO mutants were reactivated, which allowed the incorporation of BrdU into mtDNA. Thus, regulated entry of non-ubiquitylated PolγA may have beneficial consequences for certain PEO patients. This study shows that mitochondrial entry of the replicative polymerase PolgA is regulated by ubiquitylation by the E3 ligase MITOL; however, by manipulating their ubiquitylation status, some progressive external ophthalmoplegia mutants whose PolgA is polyubiquitylated and cannot enter the mitochondrion can be reactivated and hence become functionally active.
Collapse
|
20
|
Lechuga-Vieco AV, Justo-Méndez R, Enríquez JA. Not all mitochondrial DNAs are made equal and the nucleus knows it. IUBMB Life 2020; 73:511-529. [PMID: 33369015 PMCID: PMC7985871 DOI: 10.1002/iub.2434] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 12/06/2020] [Accepted: 12/09/2020] [Indexed: 12/13/2022]
Abstract
The oxidative phosphorylation (OXPHOS) system is the only structure in animal cells with components encoded by two genomes, maternally transmitted mitochondrial DNA (mtDNA), and biparentally transmitted nuclear DNA (nDNA). MtDNA‐encoded genes have to physically assemble with their counterparts encoded in the nucleus to build together the functional respiratory complexes. Therefore, structural and functional matching requirements between the protein subunits of these molecular complexes are rigorous. The crosstalk between nDNA and mtDNA needs to overcome some challenges, as the nuclear‐encoded factors have to be imported into the mitochondria in a correct quantity and match the high number of organelles and genomes per mitochondria that encode and synthesize their own components locally. The cell is able to sense the mito‐nuclear match through changes in the activity of the OXPHOS system, modulation of the mitochondrial biogenesis, or reactive oxygen species production. This implies that a complex signaling cascade should optimize OXPHOS performance to the cellular‐specific requirements, which will depend on cell type, environmental conditions, and life stage. Therefore, the mitochondria would function as a cellular metabolic information hub integrating critical information that would feedback the nucleus for it to respond accordingly. Here, we review the current understanding of the complex interaction between mtDNA and nDNA.
Collapse
Affiliation(s)
- Ana Victoria Lechuga-Vieco
- Centro Nacional de Investigaciones Cardiovasculares Carlos III, Madrid, Spain.,MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| | - Raquel Justo-Méndez
- Centro Nacional de Investigaciones Cardiovasculares Carlos III, Madrid, Spain
| | | |
Collapse
|
21
|
Zahurancik WJ, Suo Z. Kinetic investigation of the polymerase and exonuclease activities of human DNA polymerase ε holoenzyme. J Biol Chem 2020; 295:17251-17264. [PMID: 33051204 PMCID: PMC7863874 DOI: 10.1074/jbc.ra120.013903] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 10/09/2020] [Indexed: 12/31/2022] Open
Abstract
In eukaryotic DNA replication, DNA polymerase ε (Polε) is responsible for leading strand synthesis, whereas DNA polymerases α and δ synthesize the lagging strand. The human Polε (hPolε) holoenzyme is comprised of the catalytic p261 subunit and the noncatalytic p59, p17, and p12 small subunits. So far, the contribution of the noncatalytic subunits to hPolε function is not well understood. Using pre-steady-state kinetic methods, we established a minimal kinetic mechanism for DNA polymerization and editing catalyzed by the hPolε holoenzyme. Compared with the 140-kDa N-terminal catalytic fragment of p261 (p261N), which we kinetically characterized in our earlier studies, the presence of the p261 C-terminal domain (p261C) and the three small subunits increased the DNA binding affinity and the base substitution fidelity. Although the small subunits enhanced correct nucleotide incorporation efficiency, there was a wide range of rate constants when incorporating a correct nucleotide over a single-base mismatch. Surprisingly, the 3'→5' exonuclease activity of the hPolε holoenzyme was significantly slower than that of p261N when editing both matched and mismatched DNA substrates. This suggests that the presence of p261C and the three small subunits regulates the 3'→5' exonuclease activity of the hPolε holoenzyme. Together, the 3'→5' exonuclease activity and the variable mismatch extension activity modulate the overall fidelity of the hPolε holoenzyme by up to 3 orders of magnitude. Thus, the presence of p261C and the three noncatalytic subunits optimizes the dual enzymatic activities of the catalytic p261 subunit and makes the hPolε holoenzyme an efficient and faithful replicative DNA polymerase.
Collapse
Affiliation(s)
- Walter J Zahurancik
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio, USA
| | - Zucai Suo
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio, USA; Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida, USA.
| |
Collapse
|
22
|
Dangerfield TL, Johnson KA. Conformational dynamics during high-fidelity DNA replication and translocation defined using a DNA polymerase with a fluorescent artificial amino acid. J Biol Chem 2020; 296:100143. [PMID: 33273013 PMCID: PMC7857513 DOI: 10.1074/jbc.ra120.016617] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 12/02/2020] [Accepted: 12/03/2020] [Indexed: 12/21/2022] Open
Abstract
We address the role of enzyme conformational dynamics in specificity for a high-fidelity DNA polymerase responsible for genome replication. We present the complete characterization of the conformational dynamics during the correct nucleotide incorporation forward and reverse reactions using stopped-flow and rapid-quench methods with a T7 DNA polymerase variant containing a fluorescent unnatural amino acid, (7-hydroxy-4-coumarin-yl) ethylglycine, which provides a signal for enzyme conformational changes. We show that the forward conformational change (>6000 s−1) is much faster than chemistry (300 s−1) while the enzyme opening to allow release of bound nucleotide (1.7 s−1) is much slower than chemistry. These parameters show that the conformational change selects a correct nucleotide for incorporation through an induced-fit mechanism. We also measured conformational changes occurring after chemistry and during pyrophosphorolysis, providing new insights into processive polymerization. Pyrophosphorolysis occurs via a conformational selection mechanism as the pyrophosphate binds to a rare pretranslocation state of the enzyme–DNA complex. Global data fitting was achieved by including experiments in the forward and reverse directions to correlate conformational changes with chemical reaction steps. This analysis provided well-constrained values for nine rate constants to establish a complete free-energy profile including the rates of DNA translocation during processive synthesis. Translocation does not follow Brownian ratchet or power stroke models invoking nucleotide binding as the driving force. Rather, translocation is rapid and thermodynamically favorable after enzyme opening and pyrophosphate release, and it appears to limit the rate of processive synthesis at 4 °C.
Collapse
Affiliation(s)
- Tyler L Dangerfield
- Institute for Cellular and Molecular Biology, Department of Molecular Biosciences, University of Texas, Austin, Texas, USA
| | - Kenneth A Johnson
- Institute for Cellular and Molecular Biology, Department of Molecular Biosciences, University of Texas, Austin, Texas, USA.
| |
Collapse
|
23
|
Chiaratti MR, Macabelli CH, Augusto Neto JD, Grejo MP, Pandey AK, Perecin F, Collado MD. Maternal transmission of mitochondrial diseases. Genet Mol Biol 2020; 43:e20190095. [PMID: 32141474 PMCID: PMC7197987 DOI: 10.1590/1678-4685-gmb-2019-0095] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 11/01/2019] [Indexed: 12/19/2022] Open
Abstract
Given the major role of the mitochondrion in cellular homeostasis, dysfunctions of this organelle may lead to several common diseases in humans. Among these, maternal diseases linked to mitochondrial DNA (mtDNA) mutations are of special interest due to the unclear pattern of mitochondrial inheritance. Multiple copies of mtDNA are present in a cell, each encoding for 37 genes essential for mitochondrial function. In cases of mtDNA mutations, mitochondrial malfunctioning relies on mutation load, as mutant and wild-type molecules may co-exist within the cell. Since the mutation load associated with disease manifestation varies for different mutations and tissues, it is hard to predict the progeny phenotype based on mutation load in the progenitor. In addition, poorly understood mechanisms act in the female germline to prevent the accumulation of deleterious mtDNA in the following generations. In this review, we outline basic aspects of mitochondrial inheritance in mammals and how they may lead to maternally-inherited diseases. Furthermore, we discuss potential therapeutic strategies for these diseases, which may be used in the future to prevent their transmission.
Collapse
Affiliation(s)
- Marcos R Chiaratti
- Universidade Federal de São Carlos, Departamento de Genética e Evolução, Laboratório de Genética e Biotecnologia, São Carlos, SP, Brazil
| | - Carolina H Macabelli
- Universidade Federal de São Carlos, Departamento de Genética e Evolução, Laboratório de Genética e Biotecnologia, São Carlos, SP, Brazil
| | - José Djaci Augusto Neto
- Universidade Federal de São Carlos, Departamento de Genética e Evolução, Laboratório de Genética e Biotecnologia, São Carlos, SP, Brazil
| | - Mateus Priolo Grejo
- Universidade Federal de São Carlos, Departamento de Genética e Evolução, Laboratório de Genética e Biotecnologia, São Carlos, SP, Brazil
| | - Anand Kumar Pandey
- Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar, Haryana, India
| | - Felipe Perecin
- Universidade de São Paulo, Faculdade de Zootecnia e Engenharia de Alimentos, Departamento de Medicina Veterinária, Laboratório de Morfofisiologia Molecular e Desenvolvimento, Pirassununga, SP, Brazil
| | - Maite Del Collado
- Universidade de São Paulo, Faculdade de Zootecnia e Engenharia de Alimentos, Departamento de Medicina Veterinária, Laboratório de Morfofisiologia Molecular e Desenvolvimento, Pirassununga, SP, Brazil
| |
Collapse
|
24
|
Anderson AP, Luo X, Russell W, Yin YW. Oxidative damage diminishes mitochondrial DNA polymerase replication fidelity. Nucleic Acids Res 2020; 48:817-829. [PMID: 31799610 PMCID: PMC6954441 DOI: 10.1093/nar/gkz1018] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 10/12/2019] [Accepted: 11/22/2019] [Indexed: 12/20/2022] Open
Abstract
Mitochondrial DNA (mtDNA) resides in a high ROS environment and suffers more mutations than its nuclear counterpart. Increasing evidence suggests that mtDNA mutations are not the results of direct oxidative damage, rather are caused, at least in part, by DNA replication errors. To understand how the mtDNA replicase, Pol γ, can give rise to elevated mutations, we studied the effect of oxidation of Pol γ on replication errors. Pol γ is a high fidelity polymerase with polymerase (pol) and proofreading exonuclease (exo) activities. We show that Pol γ exo domain is far more sensitive to oxidation than pol; under oxidative conditions, exonuclease activity therefore declines more rapidly than polymerase. The oxidized Pol γ becomes editing-deficient, displaying a 20-fold elevated mutations than the unoxidized enzyme. Mass spectrometry analysis reveals that Pol γ exo domain is a hotspot for oxidation. The oxidized exo residues increase the net negative charge around the active site that should reduce the affinity to mismatched primer/template DNA. Our results suggest that the oxidative stress induced high mutation frequency on mtDNA can be indirectly caused by oxidation of the mitochondrial replicase.
Collapse
Affiliation(s)
- Andrew P Anderson
- Quantitative and Computational Biosciences, Baylor College of Medicine, Houston, TX 77030, USA
- Sealy Center for Structural Biology, University of Texas Medical Branch, Galveston, TX 77550, USA
| | - Xuemei Luo
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77550, USA
| | - William Russell
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77550, USA
| | - Y Whitney Yin
- Sealy Center for Structural Biology, University of Texas Medical Branch, Galveston, TX 77550, USA
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX 77550, USA
| |
Collapse
|
25
|
Hoitsma NM, Whitaker AM, Schaich MA, Smith MR, Fairlamb MS, Freudenthal BD. Structure and function relationships in mammalian DNA polymerases. Cell Mol Life Sci 2020; 77:35-59. [PMID: 31722068 PMCID: PMC7050493 DOI: 10.1007/s00018-019-03368-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 10/11/2019] [Accepted: 10/31/2019] [Indexed: 12/19/2022]
Abstract
DNA polymerases are vital for the synthesis of new DNA strands. Since the discovery of DNA polymerase I in Escherichia coli, a diverse library of mammalian DNA polymerases involved in DNA replication, DNA repair, antibody generation, and cell checkpoint signaling has emerged. While the unique functions of these DNA polymerases are differentiated by their association with accessory factors and/or the presence of distinctive catalytic domains, atomic resolution structures of DNA polymerases in complex with their DNA substrates have revealed mechanistic subtleties that contribute to their specialization. In this review, the structure and function of all 15 mammalian DNA polymerases from families B, Y, X, and A will be reviewed and discussed with special emphasis on the insights gleaned from recently published atomic resolution structures.
Collapse
Affiliation(s)
- Nicole M Hoitsma
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Amy M Whitaker
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Matthew A Schaich
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Mallory R Smith
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Max S Fairlamb
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA
| | - Bret D Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA.
| |
Collapse
|
26
|
Sutherland JE, Hettinger JL, Chan A, Gilbert J, Warner GL, Davis WP. Nonclinical Safety Profile of Revusiran, a 1st-Generation GalNAc-siRNA Conjugate for Treatment of Hereditary Transthyretin-Mediated Amyloidosis. Nucleic Acid Ther 2019; 30:33-49. [PMID: 31821125 PMCID: PMC6987735 DOI: 10.1089/nat.2019.0796] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Revusiran is a 1st-generation short interfering RNA targeting transthyretin conjugated to an N-acetylgalactosamine ligand to facilitate delivery to hepatocytes via uptake by the asialoglycoprotein receptors. Revusiran, in development for the treatment of hereditary transthyretin-mediated amyloidosis, was discontinued after an imbalance in deaths in the “ENDEAVOUR” phase 3 clinical trial. Nonclinical safety assessments included safety pharmacology, acute and repeat-dose toxicity, genotoxicity, and carcinogenicity. There were no effects on cardiovascular or respiratory function in monkeys after single doses of up to 100 mg/kg. No neurological effects were noted in monkeys in repeat-dose studies up to 300 mg/kg. Revusiran was well tolerated in repeat-dose mouse (weekly doses) and rat and monkey (five daily doses followed by weekly doses) toxicity studies. The no observed adverse effect level (NOAEL) in rats was 30 mg/kg based on reversible microscopic changes in liver that were accompanied by correlating elevations in clinical chemistry at higher doses. Dose-limiting toxicity was absent in monkeys, and the NOAEL was 200 mg/kg. There was no evidence of genotoxicity in vitro or in vivo at limit doses or carcinogenicity in a 2-year study in rats at doses up to 100 mg/kg. Overall, these results demonstrate that revusiran had a favorable nonclinical safety profile.
Collapse
Affiliation(s)
| | | | - Amy Chan
- Alnylam Pharmaceuticals, Inc., Cambridge, Massachusetts
| | - Jason Gilbert
- Alnylam Pharmaceuticals, Inc., Cambridge, Massachusetts
| | | | | |
Collapse
|
27
|
Cerrón F, de Lorenzo S, Lemishko KM, Ciesielski GL, Kaguni LS, Cao FJ, Ibarra B. Replicative DNA polymerases promote active displacement of SSB proteins during lagging strand synthesis. Nucleic Acids Res 2019; 47:5723-5734. [PMID: 30968132 PMCID: PMC6582349 DOI: 10.1093/nar/gkz249] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 03/22/2019] [Accepted: 03/29/2019] [Indexed: 11/23/2022] Open
Abstract
Genome replication induces the generation of large stretches of single-stranded DNA (ssDNA) intermediates that are rapidly protected by single-stranded DNA-binding (SSB) proteins. To date, the mechanism by which tightly bound SSBs are removed from ssDNA by the lagging strand DNA polymerase without compromising the advance of the replication fork remains unresolved. Here, we aimed to address this question by measuring, with optical tweezers, the real-time replication kinetics of the human mitochondrial and bacteriophage T7 DNA polymerases on free-ssDNA, in comparison with ssDNA covered with homologous and non-homologous SSBs under mechanical tension. We find important differences between the force dependencies of the instantaneous replication rates of each polymerase on different substrates. Modeling of the data supports a mechanism in which strong, specific polymerase-SSB interactions, up to ∼12 kBT, are required for the polymerase to dislodge SSB from the template without compromising its instantaneous replication rate, even under stress conditions that may affect SSB–DNA organization and/or polymerase–SSB communication. Upon interaction, the elimination of template secondary structure by SSB binding facilitates the maximum replication rate of the lagging strand polymerase. In contrast, in the absence of polymerase–SSB interactions, SSB poses an effective barrier for the advance of the polymerase, slowing down DNA synthesis.
Collapse
Affiliation(s)
- Fernando Cerrón
- Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia. 28049 Madrid, Spain.,Departamento Estructura de la Materia, Física Térmica y Electrónica. Universidad Complutense. 28040 Madrid, Spain
| | - Sara de Lorenzo
- Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia. 28049 Madrid, Spain
| | - Kateryna M Lemishko
- Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia. 28049 Madrid, Spain.,Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia) & CNB-CSIC-IMDEA Nanociencia Associated Unit "Unidad de Nanobiotecnología". 28049 Madrid, Spain
| | - Grzegorz L Ciesielski
- Department of Biochemistry and Molecular Biology and Center for Mitochondrial Science and Medicine, Michigan State University, East Lansing, MI 48823, USA
| | - Laurie S Kaguni
- Department of Biochemistry and Molecular Biology and Center for Mitochondrial Science and Medicine, Michigan State University, East Lansing, MI 48823, USA
| | - Francisco J Cao
- Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia. 28049 Madrid, Spain.,Departamento Estructura de la Materia, Física Térmica y Electrónica. Universidad Complutense. 28040 Madrid, Spain
| | - Borja Ibarra
- Instituto Madrileño de Estudios Avanzados en Nanociencia, IMDEA Nanociencia. 28049 Madrid, Spain.,Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia) & CNB-CSIC-IMDEA Nanociencia Associated Unit "Unidad de Nanobiotecnología". 28049 Madrid, Spain
| |
Collapse
|
28
|
Janas MM, Zlatev I, Liu J, Jiang Y, Barros SA, Sutherland JE, Davis WP, Liu J, Brown CR, Liu X, Schlegel MK, Blair L, Zhang X, Das B, Tran C, Aluri K, Li J, Agarwal S, Indrakanti R, Charisse K, Nair J, Matsuda S, Rajeev KG, Zimmermann T, Sepp-Lorenzino L, Xu Y, Akinc A, Fitzgerald K, Vaishnaw AK, Smith PF, Manoharan M, Jadhav V, Wu JT, Maier MA. Safety evaluation of 2'-deoxy-2'-fluoro nucleotides in GalNAc-siRNA conjugates. Nucleic Acids Res 2019; 47:3306-3320. [PMID: 30820542 PMCID: PMC6468299 DOI: 10.1093/nar/gkz140] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Revised: 02/07/2019] [Accepted: 02/19/2019] [Indexed: 11/29/2022] Open
Abstract
For oligonucleotide therapeutics, chemical modifications of the sugar-phosphate backbone are frequently used to confer drug-like properties. Because 2′-deoxy-2′-fluoro (2′-F) nucleotides are not known to occur naturally, their safety profile was assessed when used in revusiran and ALN-TTRSC02, two short interfering RNAs (siRNAs), of the same sequence but different chemical modification pattern and metabolic stability, conjugated to an N-acetylgalactosamine (GalNAc) ligand for targeted delivery to hepatocytes. Exposure to 2′-F-monomer metabolites was low and transient in rats and humans. In vitro, 2′-F-nucleoside 5′-triphosphates were neither inhibitors nor preferred substrates for human polymerases, and no obligate or non-obligate chain termination was observed. Modest effects on cell viability and mitochondrial DNA were observed in vitro in a subset of cell types at high concentrations of 2′-F-nucleosides, typically not attained in vivo. No apparent functional impact on mitochondria and no significant accumulation of 2′-F-monomers were observed after weekly administration of two GalNAc–siRNA conjugates in rats for ∼2 years. Taken together, the results support the conclusion that 2′-F nucleotides can be safely applied for the design of metabolically stabilized therapeutic GalNAc–siRNAs with favorable potency and prolonged duration of activity allowing for low dose and infrequent dosing.
Collapse
Affiliation(s)
- Maja M Janas
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | - Ivan Zlatev
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | - Ju Liu
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | | | | | | | | | - Jingxuan Liu
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | | | - Xiumin Liu
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | | | - Lauren Blair
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | - Xuemei Zhang
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | - Biplab Das
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | - Chris Tran
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | - Krishna Aluri
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | - Jing Li
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | - Saket Agarwal
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | | | | | | | | | | | | | | | - Yuanxin Xu
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | - Akin Akinc
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | | | | | - Peter F Smith
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | | | - Vasant Jadhav
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | - Jing-Tao Wu
- Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA
| | | |
Collapse
|
29
|
Sowers ML, Anderson APP, Wrabl JO, Yin YW. Networked Communication between Polymerase and Exonuclease Active Sites in Human Mitochondrial DNA Polymerase. J Am Chem Soc 2019; 141:10821-10829. [PMID: 31251605 PMCID: PMC7119269 DOI: 10.1021/jacs.9b04655] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
High fidelity human mitochondrial DNA polymerase (Pol γ) contains two active sites, a DNA polymerization site (pol) and a 3'-5' exonuclease site (exo) for proofreading. Although separated by 35 Å, coordination between the pol and exo sites is crucial to high fidelity replication. The biophysical mechanisms for this coordination are not completely understood. To understand the communication between the two active sites, we used a statistical-mechanical model of the protein ensemble to calculate the energetic landscape and local stability. We compared a series of structures of Pol γ, complexed with primer/template DNA, and either a nucleotide substrate or a series of nucleotide analogues, which are differentially incorporated and excised by pol and exo activity. Despite the nucleotide or its analogues being bound in the pol, Pol γ residue stability varied across the protein, particularly in the exo domain. This suggests that substrate presence in the pol can be "sensed" in the exo domain. Consistent with this hypothesis, in silico mutations made in one active site mutually perturbed the energetics of the other. To identify specific regions of the polymerase that contributed to this communication, we constructed an allosteric network connectivity map that further demonstrates specific pol-exo cooperativity. Thus, a cooperative network underlies energetic connectivity. We propose that Pol γ and other dual-function polymerases exploit an energetic coupling network that facilitates domain-domain communication to enhance discrimination between correct and incorrect nucleotides.
Collapse
Affiliation(s)
- Mark L. Sowers
- MD-PhD Combined Degree Program, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Andrew P. P. Anderson
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Program of Quantitative and Computational Biosciences, Baylor College of Medicine, Houston, Texas 71115, United States
| | - James O. Wrabl
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Y. Whitney Yin
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Sealy Center for Structural Biology, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Program of Quantitative and Computational Biosciences, Baylor College of Medicine, Houston, Texas 71115, United States
| |
Collapse
|
30
|
Park VS, Pursell ZF. POLE proofreading defects: Contributions to mutagenesis and cancer. DNA Repair (Amst) 2019; 76:50-59. [PMID: 30818169 PMCID: PMC6467506 DOI: 10.1016/j.dnarep.2019.02.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 02/14/2019] [Accepted: 02/15/2019] [Indexed: 12/14/2022]
Abstract
DNA polymerases are uniquely poised to contribute to the elevated mutation burdens seen in many human tumors. These mutations can arise through a number of different polymerase-dependent mechanisms, including intrinsic errors made using template DNA and precursor dNTPs free from chemical modifications, misinsertion events opposite chemically damaged template DNA or insertion events using modified nucleotides. While specific DNA repair polymerases have been known to contribute to tumorigenesis, the role of replication polymerases in mutagenesis in human disease has come into sharp focus over the last decade. This review describes how mutations in these replication DNA polymerases help to drive mutagenesis and tumor development, with particular attention to DNA polymerase epsilon. Recent studies using cancer genome sequencing, mutational signature analyses, yeast and mouse models, and the influence of mismatch repair on tumors with DNA polymerase mutations are discussed.
Collapse
Affiliation(s)
- Vivian S Park
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA, USA
| | - Zachary F Pursell
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA, USA; Tulane Cancer Center, Tulane University School of Medicine, 1430 Tulane Ave., New Orleans, LA, USA.
| |
Collapse
|
31
|
Weerts MJA, Smid M, Foekens JA, Sleijfer S, Martens JWM. Mitochondrial RNA Expression and Single Nucleotide Variants in Association with Clinical Parameters in Primary Breast Cancers. Cancers (Basel) 2018; 10:cancers10120500. [PMID: 30544876 PMCID: PMC6318759 DOI: 10.3390/cancers10120500] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2018] [Revised: 12/06/2018] [Accepted: 12/07/2018] [Indexed: 12/21/2022] Open
Abstract
The human mitochondrial DNA (mtDNA) encodes 37 genes, including thirteen proteins essential for the respiratory chain, and RNAs functioning in the mitochondrial translation apparatus. The total number of mtDNA molecules per cell (mtDNA content) is variable between tissue types and also between tumors and their normal counterparts. For breast cancer, tumors tend to be depleted in their mtDNA content compared to adjacent normal mammary tissue. Various studies have shown that primary breast tumors harbor somatic mtDNA variants. A decrease in mtDNA content or the presence of somatic variants could indicate a reduced mitochondrial function within breast cancer. In this explorative study we aimed to further understand genomic changes and expression of the mitochondrial genome within breast cancer, by analyzing RNA sequencing data of primary breast tumor specimens of 344 cases. We demonstrate that somatic variants detected at the mtRNA level are representative for somatic variants in the mtDNA. Also, the number of somatic variants within the mitochondrial transcriptome is not associated with mutational processes impacting the nuclear genome, but is positively associated with age at diagnosis. Finally, we observe that mitochondrial expression is related to ER status. We conclude that there is a large heterogeneity in somatic mutations of the mitochondrial genome within primary breast tumors, and differences in mitochondrial expression among breast cancer subtypes. The exact impact on metabolic differences and clinical relevance deserves further study.
Collapse
Affiliation(s)
- Marjolein J A Weerts
- Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus University Medical Center, 3015 CE Rotterdam, The Netherlands.
| | - Marcel Smid
- Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus University Medical Center, 3015 CE Rotterdam, The Netherlands.
| | - John A Foekens
- Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus University Medical Center, 3015 CE Rotterdam, The Netherlands.
| | - Stefan Sleijfer
- Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus University Medical Center, 3015 CE Rotterdam, The Netherlands.
| | - John W M Martens
- Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus University Medical Center, 3015 CE Rotterdam, The Netherlands.
| |
Collapse
|
32
|
Levinstein Hallak K, Tzur S, Rosset S. Big data analysis of human mitochondrial DNA substitution models: a regression approach. BMC Genomics 2018; 19:759. [PMID: 30340456 PMCID: PMC6195736 DOI: 10.1186/s12864-018-5123-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 09/27/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND We study Phylotree, a comprehensive representation of the phylogeny of global human mitochondrial DNA (mtDNA) variations, to better understand the mtDNA substitution mechanism and its most influential factors. We consider a substitution model, where a set of genetic features may predict the rate at which mtDNA substitutions occur. To find an appropriate model, an exhaustive analysis on the effect of multiple factors on the substitution rate is performed through Negative Binomial and Poisson regressions. We examine three different inclusion options for each categorical factor: omission, inclusion as an explanatory variable, and by-value partitioning. The examined factors include genes, codon position, a CpG indicator, directionality, nucleotide, amino acid, codon, and context (neighboring nucleotides), in addition to other site based factors. Partitioning a model by a factor's value results in several sub-models (one for each value), where the likelihoods of the sub-models can be combined to form a score for the entire model. Eventually, the leading models are considered as viable candidates for explaining mtDNA substitution rates. RESULTS Initially, we introduce a novel clustering technique on genes, based on three similarity tests between pairs of genes, supporting previous results regarding gene functionalities in the mtDNA. These clusters are then used as a factor in our models. We present leading models for the protein coding genes, rRNA and tRNA genes and the control region, showing it is disadvantageous to separate the models of transitions/transversions, or synonymous/non-synonymous substitutions. We identify a context effect that cannot be attributed solely to protein level constraints or CpG pairs. For protein-coding genes, we show that the substitution model should be partitioned into sub-models according to the codon position and input codon; additionally we confirm that gene identity and cluster have no significant effect once the above factors are accounted for. CONCLUSIONS We leverage the large, high-confidence Phylotree mtDNA phylogeny to develop a new statistical approach. We model the substitution rates using regressions, allowing consideration of many factors simultaneously. This admits the use of model selection tools helping to identify the set of factors best explaining the mutational dynamics when considered in tandem.
Collapse
Affiliation(s)
- Keren Levinstein Hallak
- Department of Statistics and Operations Research, School of Mathematical Sciences, Tel-Aviv University, 6997801, Tel-Aviv, Israel
| | - Shay Tzur
- Braun School of Public Health and Community Medicine, The Hebrew University of Jerusalem, 9112102, Jerusalem, Israel
| | - Saharon Rosset
- Department of Statistics and Operations Research, School of Mathematical Sciences, Tel-Aviv University, 6997801, Tel-Aviv, Israel.
| |
Collapse
|
33
|
Raper AT, Reed AJ, Suo Z. Kinetic Mechanism of DNA Polymerases: Contributions of Conformational Dynamics and a Third Divalent Metal Ion. Chem Rev 2018; 118:6000-6025. [DOI: 10.1021/acs.chemrev.7b00685] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Austin T. Raper
- Department of Chemistry and Biochemistry, Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio 43210, United States
| | - Andrew J. Reed
- Department of Chemistry and Biochemistry, Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio 43210, United States
| | - Zucai Suo
- Department of Chemistry and Biochemistry, Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio 43210, United States
| |
Collapse
|
34
|
Nuclear genes involved in mitochondrial diseases caused by instability of mitochondrial DNA. J Appl Genet 2018; 59:43-57. [PMID: 29344903 PMCID: PMC5799321 DOI: 10.1007/s13353-017-0424-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 12/20/2017] [Indexed: 02/07/2023]
Abstract
Mitochondrial diseases are defined by a respiratory chain dysfunction and in most of the cases manifest as multisystem disorders with predominant expression in muscles and nerves and may be caused by mutations in mitochondrial (mtDNA) or nuclear (nDNA) genomes. Most of the proteins involved in respiratory chain function are nuclear encoded, although 13 subunits of respiratory chain complexes (together with 2 rRNAs and 22 tRNAs necessary for their translation) encoded by mtDNA are essential for cell function. nDNA encodes not only respiratory chain subunits but also all the proteins responsible for mtDNA maintenance, especially those involved in replication, as well as other proteins necessary for the transcription and copy number control of this multicopy genome. Mutations in these genes can cause secondary instability of the mitochondrial genome in the form of depletion (decreased number of mtDNA molecules in the cell), vast multiple deletions or accumulation of point mutations which in turn leads to mitochondrial diseases inherited in a Mendelian fashion. The list of genes involved in mitochondrial DNA maintenance is long, and still incomplete.
Collapse
|
35
|
Baruch-Torres N, Brieba LG. Plant organellar DNA polymerases are replicative and translesion DNA synthesis polymerases. Nucleic Acids Res 2017; 45:10751-10763. [PMID: 28977655 PMCID: PMC5737093 DOI: 10.1093/nar/gkx744] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 08/14/2017] [Indexed: 02/01/2023] Open
Abstract
Genomes acquire lesions that can block the replication fork and some lesions must be bypassed to allow survival. The nuclear genome of flowering plants encodes two family-A DNA polymerases (DNAPs), the result of a duplication event, that are the sole DNAPs in plant organelles. These DNAPs, dubbed Plant Organellar Polymerases (POPs), resemble the Klenow fragment of bacterial DNAP I and are not related to metazoan and fungal mitochondrial DNAPs. Herein we report that replicative POPs from the plant model Arabidopsis thaliana (AtPolI) efficiently bypass one the most insidious DNA lesions, an apurinic/apyrimidinic (AP) site. AtPolIs accomplish lesion bypass with high catalytic efficiency during nucleotide insertion and extension. Lesion bypass depends on two unique polymerization domain insertions evolutionarily unrelated to the insertions responsible for lesion bypass by DNAP θ, an analogous lesion bypass polymerase. AtPolIs exhibit an insertion fidelity that ranks between the fidelity of replicative and lesion bypass DNAPs, moderate 3′-5′ exonuclease activity and strong strand-displacement. AtPolIs are the first known example of a family-A DNAP evolved to function in both DNA replication and lesion bypass. The lesion bypass capabilities of POPs may be required to prevent replication fork collapse in plant organelles.
Collapse
Affiliation(s)
- Noe Baruch-Torres
- Langebio-Cinvestav Sede Irapuato, Km. 9.6 Libramiento Norte Carretera. Irapuato-León, 36821 Irapuato Guanajuato, México
| | - Luis G Brieba
- Langebio-Cinvestav Sede Irapuato, Km. 9.6 Libramiento Norte Carretera. Irapuato-León, 36821 Irapuato Guanajuato, México
| |
Collapse
|
36
|
Abstract
The kinetic equations of DNA replication are shown to be exactly solved in terms of iterated function systems, running along the template sequence and giving the statistical properties of the copy sequences, as well as the kinetic and thermodynamic properties of the replication process. With this method, different effects due to sequence heterogeneity can be studied, in particular, a transition between linear and sublinear growths in time of the copies, and a transition between continuous and fractal distributions of the local velocities of the DNA polymerase along the template. The method is applied to the human mitochondrial DNA polymerase γ without and with exonuclease proofreading.
Collapse
Affiliation(s)
- Pierre Gaspard
- Center for Nonlinear Phenomena and Complex Systems, Université libre de Bruxelles (ULB), Code Postal 231, Campus Plaine, B-1050 Brussels, Belgium
| |
Collapse
|
37
|
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.
Collapse
|
38
|
Identification and characterization of a heterotrimeric archaeal DNA polymerase holoenzyme. Nat Commun 2017; 8:15075. [PMID: 28462924 PMCID: PMC5418573 DOI: 10.1038/ncomms15075] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 02/27/2017] [Indexed: 11/26/2022] Open
Abstract
Since their initial characterization over 30 years ago, it has been believed that the archaeal B-family DNA polymerases are single-subunit enzymes. This contrasts with the multi-subunit B-family replicative polymerases of eukaryotes. Here we reveal that the highly studied PolB1 from Sulfolobus solfataricus exists as a heterotrimeric complex in cell extracts. Two small subunits, PBP1 and PBP2, associate with distinct surfaces of the larger catalytic subunit and influence the enzymatic properties of the DNA polymerase. Thus, multi-subunit replicative DNA polymerase holoenzymes are present in all three domains of life. We reveal the architecture of the assembly by a combination of cross-linking coupled with mass spectrometry, X-ray crystallography and single-particle electron microscopy. The small subunits stabilize the holoenzyme assembly and the acidic tail of one small subunit mitigates the ability of the enzyme to perform strand-displacement synthesis, with important implications for lagging strand DNA synthesis. The current model for B-family DNA polymerases in archaea is one of single-subunit enzymes in contrast to the multi-subunit complexes in eukaryotes. Here the authors show that PolB1 from Sulfolobus solfataricus exists as a heterotrimeric complex in cell extracts.
Collapse
|
39
|
Kim E, Baaske MD, Schuldes I, Wilsch PS, Vollmer F. Label-free optical detection of single enzyme-reactant reactions and associated conformational changes. SCIENCE ADVANCES 2017; 3:e1603044. [PMID: 28435868 PMCID: PMC5371424 DOI: 10.1126/sciadv.1603044] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 03/09/2017] [Indexed: 05/21/2023]
Abstract
Monitoring the kinetics and conformational dynamics of single enzymes is crucial to better understand their biological functions because these motions and structural dynamics are usually unsynchronized among the molecules. However, detecting the enzyme-reactant interactions and associated conformational changes of the enzyme on a single-molecule basis remains as a challenge to established optical techniques because of the commonly required labeling of the reactants or the enzyme itself. The labeling process is usually nontrivial, and the labels themselves might skew the physical properties of the enzyme. We demonstrate an optical, label-free method capable of observing enzymatic interactions and associated conformational changes on a single-molecule level. We monitor polymerase/DNA interactions via the strong near-field enhancement provided by plasmonic nanorods resonantly coupled to whispering gallery modes in microcavities. Specifically, we use two different recognition schemes: one in which the kinetics of polymerase/DNA interactions are probed in the vicinity of DNA-functionalized nanorods, and the other in which these interactions are probed via the magnitude of conformational changes in the polymerase molecules immobilized on nanorods. In both approaches, we find that low and high polymerase activities can be clearly discerned through their characteristic signal amplitude and signal length distributions. Furthermore, the thermodynamic study of the monitored interactions suggests the occurrence of DNA polymerization. This work constitutes a proof-of-concept study of enzymatic activities using plasmonically enhanced microcavities and establishes an alternative and label-free method capable of investigating structural changes in single molecules.
Collapse
Affiliation(s)
- Eugene Kim
- Corresponding author. (E.K.); (M.D.B.); (F.V.)
| | | | | | | | | |
Collapse
|
40
|
Song YS, Shu YG, Zhou X, Ou-Yang ZC, Li M. Proofreading of DNA polymerase: a new kinetic model with higher-order terminal effects. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:025101. [PMID: 27842005 DOI: 10.1088/0953-8984/29/2/025101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The fidelity of DNA replication by DNA polymerase (DNAP) has long been an important issue in biology. While numerous experiments have revealed details of the molecular structure and working mechanism of DNAP which consists of both a polymerase site and an exonuclease (proofreading) site, there were quite a few theoretical studies on the fidelity issue. The first model which explicitly considered both sites was proposed in the 1970s and the basic idea was widely accepted by later models. However, all these models did not systematically investigate the dominant factor on DNAP fidelity, i.e. the higher-order terminal effects through which the polymerization pathway and the proofreading pathway coordinate to achieve high fidelity. In this paper, we propose a new and comprehensive kinetic model of DNAP based on some recent experimental observations, which includes previous models as special cases. We present a rigorous and unified treatment of the corresponding steady-state kinetic equations of any-order terminal effects, and derive analytical expressions for fidelity in terms of kinetic parameters under bio-relevant conditions. These expressions offer new insights on how the higher-order terminal effects contribute substantially to the fidelity in an order-by-order way, and also show that the polymerization-and-proofreading mechanism is dominated only by very few key parameters. We then apply these results to calculate the fidelity of some real DNAPs, which are in good agreements with previous intuitive estimates given by experimentalists.
Collapse
Affiliation(s)
- Yong-Shun Song
- School of Physical Sciences, University of Chinese Academy of Sciences, No 19A Yuquan Road, Beijing 100049, People's Republic of China
| | | | | | | | | |
Collapse
|
41
|
Valente WJ, Ericson NG, Long AS, White PA, Marchetti F, Bielas JH. Mitochondrial DNA exhibits resistance to induced point and deletion mutations. Nucleic Acids Res 2016; 44:8513-8524. [PMID: 27550180 PMCID: PMC5062989 DOI: 10.1093/nar/gkw716] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 08/04/2016] [Indexed: 12/17/2022] Open
Abstract
The accumulation of somatic mitochondrial DNA (mtDNA) mutations contributes to the pathogenesis of human disease. Currently, mitochondrial mutations are largely considered results of inaccurate processing of its heavily damaged genome. However, mainly from a lack of methods to monitor mtDNA mutations with sufficient sensitivity and accuracy, a link between mtDNA damage and mutation has not been established. To test the hypothesis that mtDNA-damaging agents induce mtDNA mutations, we exposed MutaTMMouse mice to benzo[a]pyrene (B[a]P) or N-ethyl-N-nitrosourea (ENU), daily for 28 consecutive days, and quantified mtDNA point and deletion mutations in bone marrow and liver using our newly developed Digital Random Mutation Capture (dRMC) and Digital Deletion Detection (3D) assays. Surprisingly, our results demonstrate mutagen treatment did not increase mitochondrial point or deletion mutation frequencies, despite evidence both compounds increase nuclear DNA mutations and demonstrated B[a]P adduct formation in mtDNA. These findings contradict models of mtDNA mutagenesis that assert the elevated rate of mtDNA mutation stems from damage sensitivity and abridged repair capacity. Rather, our results demonstrate induced mtDNA damage does not readily convert into mutation. These findings suggest robust mitochondrial damage responses repress induced mutations after mutagen exposure.
Collapse
Affiliation(s)
- William J Valente
- Translational Research Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA Medical Scientist Training Program, University of Washington School of Medicine, Seattle, WA 98195, USA Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA 98195, USA
| | - Nolan G Ericson
- Translational Research Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Alexandra S Long
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON K1A 0K9, Canada
| | - Paul A White
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON K1A 0K9, Canada
| | - Francesco Marchetti
- Environmental Health Science and Research Bureau, Health Canada, Ottawa, ON K1A 0K9, Canada
| | - Jason H Bielas
- Translational Research Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA 98195, USA Department of Pathology, University of Washington, Seattle, WA 98195, USA Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| |
Collapse
|
42
|
Gaspard P. Kinetics and thermodynamics of exonuclease-deficient DNA polymerases. Phys Rev E 2016; 93:042419. [PMID: 27176340 DOI: 10.1103/physreve.93.042419] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Indexed: 05/02/2023]
Abstract
A kinetic theory is developed for exonuclease-deficient DNA polymerases, based on the experimental observation that the rates depend not only on the newly incorporated nucleotide, but also on the previous one, leading to the growth of Markovian DNA sequences from a Bernoullian template. The dependencies on nucleotide concentrations and template sequence are explicitly taken into account. In this framework, the kinetic and thermodynamic properties of DNA replication, in particular, the mean growth velocity, the error probability, and the entropy production are calculated analytically in terms of the rate constants and the concentrations. Theory is compared with numerical simulations for the DNA polymerases of T7 viruses and human mitochondria.
Collapse
Affiliation(s)
- Pierre Gaspard
- Center for Nonlinear Phenomena and Complex Systems, Université Libre de Bruxelles, Code Postal 231, Campus Plaine, B-1050 Brussels, Belgium
| |
Collapse
|
43
|
Gaspard P. Kinetics and thermodynamics of DNA polymerases with exonuclease proofreading. Phys Rev E 2016; 93:042420. [PMID: 27176341 DOI: 10.1103/physreve.93.042420] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Indexed: 05/02/2023]
Abstract
Kinetic theory and thermodynamics are applied to DNA polymerases with exonuclease activity, taking into account the dependence of the rates on the previously incorporated nucleotide. The replication fidelity is shown to increase significantly thanks to this dependence at the basis of the mechanism of exonuclease proofreading. In particular, this dependence can provide up to a 100-fold lowering of the error probability under physiological conditions. Theory is compared with numerical simulations for the DNA polymerases of T7 viruses and human mitochondria.
Collapse
Affiliation(s)
- Pierre Gaspard
- Center for Nonlinear Phenomena and Complex Systems, Université Libre de Bruxelles, Code Postal 231, Campus Plaine, B-1050 Brussels, Belgium
| |
Collapse
|
44
|
Barrera G, Gentile F, Pizzimenti S, Canuto RA, Daga M, Arcaro A, Cetrangolo GP, Lepore A, Ferretti C, Dianzani C, Muzio G. Mitochondrial Dysfunction in Cancer and Neurodegenerative Diseases: Spotlight on Fatty Acid Oxidation and Lipoperoxidation Products. Antioxidants (Basel) 2016; 5:antiox5010007. [PMID: 26907355 PMCID: PMC4808756 DOI: 10.3390/antiox5010007] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 01/22/2016] [Accepted: 02/05/2016] [Indexed: 12/21/2022] Open
Abstract
In several human diseases, such as cancer and neurodegenerative diseases, the levels of reactive oxygen species (ROS), produced mainly by mitochondrial oxidative phosphorylation, is increased. In cancer cells, the increase of ROS production has been associated with mtDNA mutations that, in turn, seem to be functional in the alterations of the bioenergetics and the biosynthetic state of cancer cells. Moreover, ROS overproduction can enhance the peroxidation of fatty acids in mitochondrial membranes. In particular, the peroxidation of mitochondrial phospholipid cardiolipin leads to the formation of reactive aldehydes, such as 4-hydroxynonenal (HNE) and malondialdehyde (MDA), which are able to react with proteins and DNA. Covalent modifications of mitochondrial proteins by the products of lipid peroxidation (LPO) in the course of oxidative cell stress are involved in the mitochondrial dysfunctions observed in cancer and neurodegenerative diseases. Such modifications appear to affect negatively mitochondrial integrity and function, in particular energy metabolism, adenosine triphosphate (ATP) production, antioxidant defenses and stress responses. In neurodegenerative diseases, indirect confirmation for the pathogenetic relevance of LPO-dependent modifications of mitochondrial proteins comes from the disease phenotypes associated with their genetic alterations.
Collapse
Affiliation(s)
- Giuseppina Barrera
- Dipartimento di Scienze Cliniche e Biologiche, Università di Torino, Torino 10125, Italy.
| | - Fabrizio Gentile
- Dipartimento di Medicina e Scienze della Salute "V. Tiberio", Università del Molise, Campobasso 86100, Italy.
| | - Stefania Pizzimenti
- Dipartimento di Scienze Cliniche e Biologiche, Università di Torino, Torino 10125, Italy.
| | - Rosa Angela Canuto
- Dipartimento di Scienze Cliniche e Biologiche, Università di Torino, Torino 10125, Italy.
| | - Martina Daga
- Dipartimento di Scienze Cliniche e Biologiche, Università di Torino, Torino 10125, Italy.
| | - Alessia Arcaro
- Dipartimento di Medicina e Scienze della Salute "V. Tiberio", Università del Molise, Campobasso 86100, Italy.
| | - Giovanni Paolo Cetrangolo
- Dipartimento di Medicina e Scienze della Salute "V. Tiberio", Università del Molise, Campobasso 86100, Italy.
| | - Alessio Lepore
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II, Napoli 80131, Italy.
| | - Carlo Ferretti
- Dipartimento di Scienze e Tecnologia del Farmaco, Università di Torino, Torino 10125, Italy.
| | - Chiara Dianzani
- Dipartimento di Scienze e Tecnologia del Farmaco, Università di Torino, Torino 10125, Italy.
| | - Giuliana Muzio
- Dipartimento di Scienze Cliniche e Biologiche, Università di Torino, Torino 10125, Italy.
| |
Collapse
|
45
|
Clark-Matott J, Saleem A, Dai Y, Shurubor Y, Ma X, Safdar A, Beal MF, Tarnopolsky M, Simon DK. Metabolomic analysis of exercise effects in the POLG mitochondrial DNA mutator mouse brain. Neurobiol Aging 2015; 36:2972-2983. [PMID: 26294258 DOI: 10.1016/j.neurobiolaging.2015.07.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 06/12/2015] [Accepted: 07/13/2015] [Indexed: 01/09/2023]
Abstract
Mitochondrial DNA (mtDNA) mutator mice express a mutated form of mtDNA polymerase gamma that results an accelerated accumulation of somatic mtDNA mutations in association with a premature aging phenotype. An exploratory metabolomic analysis of cortical metabolites in sedentary and exercised mtDNA mutator mice and wild-type littermate controls at 9-10 months of age was performed. Pathway analysis revealed deficits in the neurotransmitters acetylcholine, glutamate, and aspartate that were ameliorated by exercise. Nicotinamide adenine dinucleotide (NAD) depletion and evidence of increased poly(adenosine diphosphate-ribose) polymerase 1 (PARP1)activity were apparent in sedentary mtDNA mutator mouse cortex, along with deficits in carnitine metabolites and an upregulated antioxidant response that largely normalized with exercise. These data highlight specific pathways that are altered in the brain in association with an accelerated age-related accumulation of somatic mtDNA mutations. These results may have relevance to age-related neurodegenerative diseases associated with mitochondrial dysfunction, such as Alzheimer's disease and Parkinson's disease and provide insights into potential mechanisms of beneficial effects of exercise on brain function.
Collapse
Affiliation(s)
- Joanne Clark-Matott
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA.
| | - Ayesha Saleem
- Department of Pediatrics, McMaster University Medical Center, Hamilton, Ontario, Canada; Department of Medicine, McMaster University Medical Center, Hamilton, Ontario, Canada
| | - Ying Dai
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Yevgeniya Shurubor
- Brain and Mind Institute, Weill Medical College, Cornell University, New York, NY, USA
| | - Xiaoxing Ma
- Department of Pediatrics, McMaster University Medical Center, Hamilton, Ontario, Canada; Department of Medicine, McMaster University Medical Center, Hamilton, Ontario, Canada
| | - Adeel Safdar
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| | - Myron Flint Beal
- Brain and Mind Institute, Weill Medical College, Cornell University, New York, NY, USA
| | - Mark Tarnopolsky
- Department of Pediatrics, McMaster University Medical Center, Hamilton, Ontario, Canada; Department of Medicine, McMaster University Medical Center, Hamilton, Ontario, Canada
| | - David K Simon
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA
| |
Collapse
|
46
|
How do changes in the mtDNA and mitochondrial dysfunction influence cancer and cancer therapy? Challenges, opportunities and models. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2015; 764:16-30. [DOI: 10.1016/j.mrrev.2015.01.001] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 01/11/2015] [Accepted: 01/12/2015] [Indexed: 12/28/2022]
|
47
|
Vashishtha AK, Kuchta RD. Polymerase and exonuclease activities in herpes simplex virus type 1 DNA polymerase are not highly coordinated. Biochemistry 2015; 54:240-9. [PMID: 25517265 PMCID: PMC4303300 DOI: 10.1021/bi500840v] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
The
herpes polymerase–processivity factor complex consists
of the catalytic UL30 subunit containing both polymerase and proofreading
exonuclease activities and the UL42 subunit that acts as a processivity
factor. Curiously, the highly active exonuclease has minimal impact
on the accumulation of mismatches generated by the polymerase activity.
We utilized a series of oligonucleotides of defined sequence to define
the interactions between the polymerase and exonuclease active sites.
Exonuclease activity requires unwinding of two nucleotides of the
duplex primer–template. Surprisingly, even though the exonuclease
rate is much higher than the rate of DNA dissociation, the exonuclease
degrades both single- and double-stranded DNA in a nonprocessive manner.
Efficient proofreading of incorrect nucleotides incorporated by the
polymerase would seem to require efficient translocation of DNA between
the exonuclease and polymerase active sites. However, we found that translocation of
DNA from the exonuclease to polymerase active site is remarkably inefficient.
Consistent with inefficient translocation, the DNA binding sites for
the exonuclease and polymerase active sites appear to be largely independent,
such that the two activities appear noncoordinated. Finally, the presence
or absence of UL42 did not impact the coordination of the polymerase
and exonuclease activities. In addition to providing fundamental insights
into how the polymerase and exonuclease function together, these activities
provide a rationale for understanding why the exonuclease minimally
impacts accumulation of mismatches by the purified polymerase and
raise the question of how these two activities function together in
vivo.
Collapse
Affiliation(s)
- Ashwani Kumar Vashishtha
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States
| | | |
Collapse
|
48
|
Zahurancik WJ, Klein SJ, Suo Z. Significant contribution of the 3'→5' exonuclease activity to the high fidelity of nucleotide incorporation catalyzed by human DNA polymerase ϵ. Nucleic Acids Res 2014; 42:13853-60. [PMID: 25414327 PMCID: PMC4267634 DOI: 10.1093/nar/gku1184] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 11/02/2014] [Accepted: 11/03/2014] [Indexed: 11/30/2022] Open
Abstract
Most eukaryotic DNA replication is performed by A- and B-family DNA polymerases which possess a faithful polymerase activity that preferentially incorporates correct over incorrect nucleotides. Additionally, many replicative polymerases have an efficient 3'→5' exonuclease activity that excises misincorporated nucleotides. Together, these activities contribute to overall low polymerase error frequency (one error per 10(6)-10(8) incorporations) and support faithful eukaryotic genome replication. Eukaryotic DNA polymerase ϵ (Polϵ) is one of three main replicative DNA polymerases for nuclear genomic replication and is responsible for leading strand synthesis. Here, we employed pre-steady-state kinetic methods and determined the overall fidelity of human Polϵ (hPolϵ) by measuring the individual contributions of its polymerase and 3'→5' exonuclease activities. The polymerase activity of hPolϵ has a high base substitution fidelity (10(-4)-10(-7)) resulting from large decreases in both nucleotide incorporation rate constants and ground-state binding affinities for incorrect relative to correct nucleotides. The 3'→5' exonuclease activity of hPolϵ further enhances polymerization fidelity by an unprecedented 3.5 × 10(2) to 1.2 × 10(4)-fold. The resulting overall fidelity of hPolϵ (10(-6)-10(-11)) justifies hPolϵ to be a primary enzyme to replicate human nuclear genome (0.1-1.0 error per round). Consistently, somatic mutations in hPolϵ, which decrease its exonuclease activity, are connected with mutator phenotypes and cancer formation.
Collapse
Affiliation(s)
- Walter J Zahurancik
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
| | - Seth J Klein
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
| | - Zucai Suo
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
| |
Collapse
|
49
|
Stumpf JD, Copeland WC. MMS exposure promotes increased MtDNA mutagenesis in the presence of replication-defective disease-associated DNA polymerase γ variants. PLoS Genet 2014; 10:e1004748. [PMID: 25340760 PMCID: PMC4207668 DOI: 10.1371/journal.pgen.1004748] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 09/11/2014] [Indexed: 11/18/2022] Open
Abstract
Mitochondrial DNA (mtDNA) encodes proteins essential for ATP production. Mutant variants of the mtDNA polymerase cause mutagenesis that contributes to aging, genetic diseases, and sensitivity to environmental agents. We interrogated mtDNA replication in Saccharomyces cerevisiae strains with disease-associated mutations affecting conserved regions of the mtDNA polymerase, Mip1, in the presence of the wild type Mip1. Mutant frequency arising from mtDNA base substitutions that confer erythromycin resistance and deletions between 21-nucleotide direct repeats was determined. Previously, increased mutagenesis was observed in strains encoding mutant variants that were insufficient to maintain mtDNA and that were not expected to reduce polymerase fidelity or exonuclease proofreading. Increased mutagenesis could be explained by mutant variants stalling the replication fork, thereby predisposing the template DNA to irreparable damage that is bypassed with poor fidelity. This hypothesis suggests that the exogenous base-alkylating agent, methyl methanesulfonate (MMS), would further increase mtDNA mutagenesis. Mitochondrial mutagenesis associated with MMS exposure was increased up to 30-fold in mip1 mutants containing disease-associated alterations that affect polymerase activity. Disrupting exonuclease activity of mutant variants was not associated with increased spontaneous mutagenesis compared with exonuclease-proficient alleles, suggesting that most or all of the mtDNA was replicated by wild type Mip1. A novel subset of C to G transversions was responsible for about half of the mutants arising after MMS exposure implicating error-prone bypass of methylated cytosines as the predominant mutational mechanism. Exposure to MMS does not disrupt exonuclease activity that suppresses deletions between 21-nucleotide direct repeats, suggesting the MMS-induce mutagenesis is not explained by inactivated exonuclease activity. Further, trace amounts of CdCl2 inhibit mtDNA replication but suppresses MMS-induced mutagenesis. These results suggest a novel mechanism wherein mutations that lead to hypermutation by DNA base-damaging agents and associate with mitochondrial disease may contribute to previously unexplained phenomena, such as the wide variation of age of disease onset and acquired mitochondrial toxicities. Thousands of mitochondrial DNA (mtDNA) per cell are necessary to maintain energy required for cellular survival in humans. Interfering with the mtDNA polymerase can result in mitochondrial diseases and mitochondrial toxicity. Therefore, it is important to explore new genetic and environmental mechanisms that alter the effectiveness and accuracy of mtDNA replication. This genetic study uses the budding yeast to demonstrate that heterozygous strains harboring disease-associated mutations in the mtDNA polymerase gene in the presence of a wild type copy of the mtDNA polymerase are associated with increased mtDNA point mutagenesis in the presence of methane methylsulfonate, a known base damaging agent. Further observations suggest that the inability of disease-associated variants to replicate mtDNA resulted in increased vulnerability to irreparable base damage that was likely to result in mutations when replicated. Also, this study showed that trace amounts of the environmental contaminant cadmium chloride impairs mtDNA replication but eliminates damage-induced mutagenesis in the remaining functional mitochondria. This interplay between disease-associated variant and wild type polymerase offers new insights on possible disease variation and implicates novel environmental consequences for compound heterozygous patients.
Collapse
Affiliation(s)
- Jeffrey D. Stumpf
- Mitochondrial DNA Replication Group, Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, North Carolina, United States of America
| | - William C. Copeland
- Mitochondrial DNA Replication Group, Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, North Carolina, United States of America
- * E-mail:
| |
Collapse
|
50
|
Maxwell BA, Suo Z. Recent insight into the kinetic mechanisms and conformational dynamics of Y-Family DNA polymerases. Biochemistry 2014; 53:2804-14. [PMID: 24716482 PMCID: PMC4018064 DOI: 10.1021/bi5000405] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
![]()
The
kinetic mechanisms by which DNA polymerases catalyze DNA replication
and repair have long been areas of active research. Recently discovered
Y-family DNA polymerases catalyze the bypass of damaged DNA bases
that would otherwise block replicative DNA polymerases and stall replication
forks. Unlike DNA polymerases from the five other families, the Y-family
DNA polymerases have flexible, solvent-accessible active sites that
are able to tolerate various types of damaged template bases and allow
for efficient lesion bypass. Their promiscuous active sites, however,
also lead to fidelities that are much lower than those observed for
other DNA polymerases and give rise to interesting mechanistic properties.
Additionally, the Y-family DNA polymerases have several other unique
structural features and undergo a set of conformational changes during
substrate binding and catalysis different from those observed for
replicative DNA polymerases. In recent years, pre-steady-state kinetic
methods have been extensively employed to reveal a wealth of information
about the catalytic properties of these fascinating noncanonical DNA
polymerases. Here, we review many of the recent findings on the kinetic
mechanisms of DNA polymerization with undamaged and damaged DNA substrates
by the Y-family DNA polymerases, and the conformational dynamics employed
by these error-prone enzymes during catalysis.
Collapse
Affiliation(s)
- Brian A Maxwell
- Ohio State Biophysics Program and ‡Department of Chemistry and Biochemistry, The Ohio State University , Columbus, Ohio 43210, United States
| | | |
Collapse
|