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Amodeo S, Bregy I, Ochsenreiter T. Mitochondrial genome maintenance-the kinetoplast story. FEMS Microbiol Rev 2023; 47:fuac047. [PMID: 36449697 PMCID: PMC10719067 DOI: 10.1093/femsre/fuac047] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 08/13/2022] [Accepted: 11/24/2022] [Indexed: 12/17/2023] Open
Abstract
Mitochondrial DNA replication is an essential process in most eukaryotes. Similar to the diversity in mitochondrial genome size and organization in the different eukaryotic supergroups, there is considerable diversity in the replication process of the mitochondrial DNA. In this review, we summarize the current knowledge of mitochondrial DNA replication and the associated factors in trypanosomes with a focus on Trypanosoma brucei, and provide a new model of minicircle replication for this protozoan parasite. The model assumes the mitochondrial DNA (kinetoplast DNA, kDNA) of T. brucei to be loosely diploid in nature and the replication of the genome to occur at two replication centers at the opposing ends of the kDNA disc (also known as antipodal sites, APS). The new model is consistent with the localization of most replication factors and in contrast to the current model, it does not require the assumption of an unknown sorting and transport complex moving freshly replicated DNA to the APS. In combination with the previously proposed sexual stages of the parasite in the insect vector, the new model provides a mechanism for maintenance of the mitochondrial genetic diversity.
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Affiliation(s)
- Simona Amodeo
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Hochschulstrasse 6, 3012 Bern, Switzerland
| | - Irina Bregy
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Hochschulstrasse 6, 3012 Bern, Switzerland
| | - Torsten Ochsenreiter
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
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2
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Gonçalves CS, Catta-Preta CMC, Repolês B, Mottram JC, De Souza W, Machado CR, Motta MCM. Importance of Angomonas deanei KAP4 for kDNA arrangement, cell division and maintenance of the host-bacterium relationship. Sci Rep 2021; 11:9210. [PMID: 33911164 PMCID: PMC8080567 DOI: 10.1038/s41598-021-88685-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Accepted: 04/13/2021] [Indexed: 11/29/2022] Open
Abstract
Angomonas deanei coevolves in a mutualistic relationship with a symbiotic bacterium that divides in synchronicity with other host cell structures. Trypanosomatid mitochondrial DNA is contained in the kinetoplast and is composed of thousands of interlocked DNA circles (kDNA). The arrangement of kDNA is related to the presence of histone-like proteins, known as KAPs (kinetoplast-associated proteins), that neutralize the negatively charged kDNA, thereby affecting the activity of mitochondrial enzymes involved in replication, transcription and repair. In this study, CRISPR-Cas9 was used to delete both alleles of the A. deanei KAP4 gene. Gene-deficient mutants exhibited high compaction of the kDNA network and displayed atypical phenotypes, such as the appearance of a filamentous symbionts, cells containing two nuclei and one kinetoplast, and division blocks. Treatment with cisplatin and UV showed that Δkap4 null mutants were not more sensitive to DNA damage and repair than wild-type cells. Notably, lesions caused by these genotoxic agents in the mitochondrial DNA could be repaired, suggesting that the kDNA in the kinetoplast of trypanosomatids has unique repair mechanisms. Taken together, our data indicate that although KAP4 is not an essential protein, it plays important roles in kDNA arrangement and replication, as well as in the maintenance of symbiosis.
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Affiliation(s)
- Camila Silva Gonçalves
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, IBCCF, CCS, UFRJ, Cidade Universitária, Rio de Janeiro, RJ, CEP 21941-590, Brazil
- Centro Nacional de Biologia Estrutural e Bioimagem, Rio de Janeiro, RJ, Brazil
| | | | - Bruno Repolês
- Laboratório de Genética Bioquímica, Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Jeremy C Mottram
- Department of Biology, York Biomedical Research Institute, University of York, Wentworth Way, Heslington, York, YO10 5DD, UK
| | - Wanderley De Souza
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, IBCCF, CCS, UFRJ, Cidade Universitária, Rio de Janeiro, RJ, CEP 21941-590, Brazil
- Centro Nacional de Biologia Estrutural e Bioimagem, Rio de Janeiro, RJ, Brazil
| | - Carlos Renato Machado
- Laboratório de Genética Bioquímica, Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
| | - Maria Cristina M Motta
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, IBCCF, CCS, UFRJ, Cidade Universitária, Rio de Janeiro, RJ, CEP 21941-590, Brazil.
- Centro Nacional de Biologia Estrutural e Bioimagem, Rio de Janeiro, RJ, Brazil.
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3
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Gibson W. The sexual side of parasitic protists. Mol Biochem Parasitol 2021; 243:111371. [PMID: 33872659 DOI: 10.1016/j.molbiopara.2021.111371] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 03/26/2021] [Accepted: 04/13/2021] [Indexed: 01/09/2023]
Abstract
Much of the vast evolutionary landscape occupied by Eukaryotes is dominated by protists. Though parasitism has arisen in many lineages, there are three main groups of parasitic protists of relevance to human and livestock health: the Apicomplexa, including the malaria parasite Plasmodium and coccidian pathogens of livestock such as Eimeria; the excavate flagellates, encompassing a diverse range of protist pathogens including trypanosomes, Leishmania, Giardia and Trichomonas; and the Amoebozoa, including pathogenic amoebae such as Entamoeba. These three groups represent separate, deep branches of the eukaryote tree, underlining their divergent evolutionary histories. Here, I explore what is known about sex in these three main groups of parasitic protists.
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Affiliation(s)
- Wendy Gibson
- School of Biological Sciences, Life Sciences Building, University of Bristol, Bristol, BS8 1TQ, United Kingdom.
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4
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Dofuor AK, Djameh GI, Ayertey F, Bolah P, Amoa-Bosompem M, Kyeremeh K, Okine LK, Gwira TM, Ohashi M. Antitrypanosomal Effects of Zanthoxylum zanthoxyloides (Lam.) Zepern. & Timler Extracts on African Trypanosomes. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE : ECAM 2019; 2019:1730452. [PMID: 31354849 PMCID: PMC6637693 DOI: 10.1155/2019/1730452] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 06/15/2019] [Indexed: 12/19/2022]
Abstract
African trypanosomiasis is a disease caused by the parasitic protozoa of the Trypanosoma genus. Despite several efforts at chemotherapeutic interventions, the disease poses serious health and economic concerns to humans and livestock of many sub-Saharan African countries. Zanthoxylum zanthoxyloides (Lam.) Zepern. & Timler (Z. zanthoxyloides LZT) is a plant species of important phytochemical and pharmacological relevance in the subtropical zones of the African continent. However, the mechanisms of its antitrypanosomal effects in African trypanosomes remain to be elucidated. The aim of the study was to determine the in vitro effects and mechanisms of action of Z. zanthoxyloides LZT (root) fractions against Trypanosoma brucei. T. brucei (GUTat 3.1 strain), L. donovani (D10 strain), P. falciparum (3D 7 strain), Jurkat cells, and Chang liver cells were cultivated in vitro to the log phase in their respective media at 37°C. Crude extracts and fractions were prepared from air-dried pulverized plant material of Z. zanthoxyloides LZT (root) using the modified Kupchan method of solvent partitioning. Half-maximal inhibitory concentrations (IC50) were determined through the alamar blue cell viability assay. Effects of fractions on cell death and cell cycle of T. brucei were determined using flow cytometry. Fluorescence microscopy was used to investigate the effects of fractions on the morphology and distribution of T. brucei. Antitrypanosomal compounds of fractions were characterized using high-performance liquid chromatography (HPLC) and attenuated total reflectance infrared (ATR-IR) spectroscopy. Methanol, butanol, and dichloromethane fractions were selectively active against T. brucei with respective IC50 values of 3.89, 4.02, and 5.70 μg/ml. Moreover, methanol, butanol, and dichloromethane fractions significantly induced apoptosis-like cell death with remarkable alteration in the cell cycle of T. brucei. Furthermore, dichloromethane and methanol fractions altered the morphology, induced aggregation, and altered the ratio of nuclei to kinetoplasts in the parasite. The HPLC chromatograms and ATR-IR spectra of the active fractions suggested the presence of aromatic hydrocarbons with hydroxyl, carbonyl, amine, or amide functional groups. The results suggest that Z. zanthoxyloides LZT have potential chemotherapeutic effects on African trypanosomes with implications for novel therapeutic interventions in African trypanosomiasis.
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Affiliation(s)
- Aboagye Kwarteng Dofuor
- West African Center for Cell Biology of Infectious Pathogens, University of Ghana, Legon, Ghana
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, Legon, Ghana
| | - Georgina Isabella Djameh
- Department of Parasitology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | | | - Peter Bolah
- Center for Plant Medicine Research, Mampong-Akuapem, Ghana
| | - Michael Amoa-Bosompem
- Department of Parasitology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Kwaku Kyeremeh
- Department of Chemistry, University of Ghana, Legon, Ghana
| | - Laud Kenneth Okine
- West African Center for Cell Biology of Infectious Pathogens, University of Ghana, Legon, Ghana
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, Legon, Ghana
| | - Theresa Manful Gwira
- West African Center for Cell Biology of Infectious Pathogens, University of Ghana, Legon, Ghana
- Department of Biochemistry, Cell and Molecular Biology, University of Ghana, Legon, Ghana
| | - Mitsuko Ohashi
- Department of Parasitology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
- Department of Environmental Parasitology, Tokyo Medical and Dental University, Tokyo, Japan
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5
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dos Santos Rodrigues FH, Firczuk H, Breeze AL, Cameron AD, Walko M, Wilson AJ, Zanchin NIT, McCarthy JEG. The Leishmania PABP1-eIF4E4 interface: a novel 5'-3' interaction architecture for trans-spliced mRNAs. Nucleic Acids Res 2019; 47:1493-1504. [PMID: 30476241 PMCID: PMC6379680 DOI: 10.1093/nar/gky1187] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 10/15/2018] [Accepted: 11/07/2018] [Indexed: 11/18/2022] Open
Abstract
Trans-splicing of trypanosomatid polycistronic transcripts produces polyadenylated monocistronic mRNAs modified to form the 5' cap4 structure (m7Gpppm36,6,2'Apm2'Apm2'Cpm23,2'U). NMR and X-ray crystallography reveal that Leishmania has a unique type of N-terminally-extended cap-binding protein (eIF4E4) that binds via a PAM2 motif to PABP1. This relies on the interactions of a combination of polar and charged amino acid side-chains together with multiple hydrophobic interactions, and underpins a novel architecture in the Leishmania cap4-binding translation factor complex. Measurements using microscale thermophoresis, fluorescence anisotropy and surface plasmon resonance characterize the key interactions driving assembly of the Leishmania translation initiation complex. We demonstrate that this complex can accommodate Leishmania eIF4G3 which, unlike the standard eukaryotic initiation complex paradigm, binds tightly to eIF4E4, but not to PABP1. Thus, in Leishmania, the chain of interactions 5'cap4-eIF4E4-PABP1-poly(A) bridges the mRNA 5' and 3' ends. Exceptionally, therefore, by binding tightly to two protein ligands and to the mRNA 5' cap4 structure, the trypanosomatid N-terminally extended form of eIF4E acts as the core molecular scaffold for the mRNA-cap-binding complex. Finally, the eIF4E4 N-terminal extension is an intrinsically disordered region that transitions to a partly folded form upon binding to PABP1, whereby this interaction is not modulated by poly(A) binding to PABP1.
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Affiliation(s)
| | - Helena Firczuk
- Warwick Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Gibbet Hill, Coventry CV4 7AL, UK
| | - Alexander L Breeze
- Astbury Centre for Structural Molecular Biology, University of Leeds, LS2 9JT, UK
- Faculty of Biological Sciences, University of Leeds, LS2 9JT, UK
| | - Alexander D Cameron
- Warwick Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Gibbet Hill, Coventry CV4 7AL, UK
| | - Martin Walko
- Astbury Centre for Structural Molecular Biology, University of Leeds, LS2 9JT, UK
- School of Chemistry, University of Leeds, LS2 9JT, UK
| | - Andrew J Wilson
- Astbury Centre for Structural Molecular Biology, University of Leeds, LS2 9JT, UK
- School of Chemistry, University of Leeds, LS2 9JT, UK
| | - Nilson I T Zanchin
- Instituto Carlos Chagas, FIOCRUZ-Paraná, Rua Professor Algacyr Munhoz Mader 3775, Curitiba, PR 81350-010, Brazil
| | - John E G McCarthy
- Warwick Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Gibbet Hill, Coventry CV4 7AL, UK
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Cavalcanti DP, de Souza W. The Kinetoplast of Trypanosomatids: From Early Studies of Electron Microscopy to Recent Advances in Atomic Force Microscopy. SCANNING 2018; 2018:9603051. [PMID: 30018700 PMCID: PMC6029474 DOI: 10.1155/2018/9603051] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 05/07/2018] [Accepted: 05/15/2018] [Indexed: 06/08/2023]
Abstract
The kinetoplast is a specialized region of the mitochondria of trypanosomatids that harbors the most complex and unusual mitochondrial DNA found in nature. Kinetoplast DNA (kDNA) is composed of thousands of circular molecules topologically interlocked to form a single network. Two types of DNA circles are present in the kinetoplast: minicircles (0.5-10 kb) and maxicircles (20-40 kb). Knowledge of kinetoplast architecture is crucial to understanding the replication and segregation of kDNA circles because the molecules involved in these processes are precisely positioned in functional domains throughout the kinetoplast. The fine structure of the kinetoplast was revealed in early electron microscopy (EM) studies. However, an understanding of the topological organization of kDNA was only demonstrated after the development of protocols to separate kDNA from nuclear DNA, followed by EM observations. Electron microscopy analysis of thin sections of trypanosomatids, spreading of isolated kDNA networks onto EM grids, deep-etching studies, and cytochemical and immunocytochemical approaches are examples of techniques that were useful for elucidating the structure and replication of the kinetoplast. Recently, atomic force microscopy has joined this set of techniques and improved our knowledge about the kDNA network and revealed new details about kDNA topology in trypanosomatids.
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Affiliation(s)
- Danielle Pereira Cavalcanti
- Laboratório de Microbiologia, Diretoria de Metrologia Aplicada às Ciências da Vida, Instituto Nacional de Metrologia, Qualidade e Tecnologia-Inmetro, Rio de Janeiro, RJ, Brazil
- Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem and Centro Nacional de Biologia Estrutural e Bioimagem (CENABIO), Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Wanderley de Souza
- Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem and Centro Nacional de Biologia Estrutural e Bioimagem (CENABIO), Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
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7
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In-Phase Assembly of Slim DNA Lattices with Small Circular DNA Motifs via Short Connections of 11 and 16 Base Pairs. Chembiochem 2016; 17:1132-7. [DOI: 10.1002/cbic.201600054] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Indexed: 12/14/2022]
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8
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Vologodskii A. Disentangling DNA molecules. Phys Life Rev 2016; 18:118-134. [PMID: 27173054 DOI: 10.1016/j.plrev.2016.05.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2016] [Revised: 04/29/2016] [Accepted: 05/02/2016] [Indexed: 01/12/2023]
Abstract
The widespread circular form of DNA molecules inside cells creates very serious topological problems during replication. Due to the helical structure of the double helix the parental strands of circular DNA form a link of very high order, and yet they have to be unlinked before the cell division. DNA topoisomerases, the enzymes that catalyze passing of one DNA segment through another, solve this problem in principle. However, it is very difficult to remove all entanglements between the replicated DNA molecules due to huge length of DNA comparing to the cell size. One strategy that nature uses to overcome this problem is to create the topoisomerases that can dramatically reduce the fraction of linked circular DNA molecules relative to the corresponding fraction at thermodynamic equilibrium. This striking property of the enzymes means that the enzymes that interact with DNA only locally can access their topology, a global property of circular DNA molecules. This review considers the experimental studies of the phenomenon and analyzes the theoretical models that have been suggested in attempts to explain it. We describe here how various models of enzyme action can be investigated computationally. There is no doubt at the moment that we understand basic principles governing enzyme action. Still, there are essential quantitative discrepancies between the experimental data and the theoretical predictions. We consider how these discrepancies can be overcome.
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Abstract
I knew nothing and had thought nothing about parasites until 1971. In fact, if you had asked me before then, I might have commented that parasites were rather disgusting. I had been at the Johns Hopkins School of Medicine for three years, and I was on the lookout for a new project. In 1971, I came across a paper in the Journal of Molecular Biology by Larry Simpson, a classmate of mine in graduate school. Larry's paper described a remarkable DNA structure known as kinetoplast DNA (kDNA), isolated from a parasite. kDNA, the mitochondrial genome of trypanosomatids, is a DNA network composed of several thousand interlocked DNA rings. Almost nothing was known about it. I was looking for a project on DNA replication, and I wanted it to be both challenging and important. I had no doubt that working with kDNA would be a challenge, as I would be exploring uncharted territory. I was also sure that the project would be important when I learned that parasites with kDNA threaten huge populations in underdeveloped tropical countries. Looking again at Larry's paper, I found the electron micrographs of the kDNA networks to be rather beautiful. I decided to take a chance on kDNA. Little did I know then that I would devote the next forty years of my life to studying kDNA replication.
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Affiliation(s)
- Paul T Englund
- From the Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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10
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Povelones ML. Beyond replication: division and segregation of mitochondrial DNA in kinetoplastids. Mol Biochem Parasitol 2014; 196:53-60. [PMID: 24704441 DOI: 10.1016/j.molbiopara.2014.03.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Revised: 03/18/2014] [Accepted: 03/25/2014] [Indexed: 11/29/2022]
Abstract
The mitochondrial genome of kinetoplastids, called kinetoplast DNA (kDNA) is a complex structure that must be faithfully duplicated exactly once per cell cycle. Despite many years of thorough investigation into the kDNA replication mechanism, many of the molecular details of the later stages of the process, particularly kDNA division and segregation, remain mysterious. In addition, perturbation of several cellular activities, some only indirectly related to kDNA, can lead to asymmetric kDNA division and other segregation defects. This review will examine unifying features and possible explanations for these phenotypes in the context of current models for kDNA division and segregation.
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11
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Rodrigues JCF, Godinho JLP, de Souza W. Biology of human pathogenic trypanosomatids: epidemiology, lifecycle and ultrastructure. Subcell Biochem 2014; 74:1-42. [PMID: 24264239 DOI: 10.1007/978-94-007-7305-9_1] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Leishmania and Trypanosoma belong to the Trypanosomatidae family and cause important human infections such as leishmaniasis, Chagas disease, and sleeping sickness. Leishmaniasis, caused by protozoa belonging to Leishmania, affects about 12 million people worldwide and can present different clinical manifestations, i.e., visceral leishmaniasis (VL), cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (MCL), diffuse cutaneous leishmaniasis (DCL), and post-kala-azar dermal leishmaniasis (PKDL). Chagas disease, also known as American trypanosomiasis, is caused by Trypanosoma cruzi and is mainly prevalent in Latin America but is increasingly occurring in the United States, Canada, and Europe. Sleeping sickness or human African trypanosomiasis (HAT), caused by two sub-species of Trypanosoma brucei (i.e., T. b. rhodesiense and T. b. gambiense), occurs only in sub-Saharan Africa countries. These pathogenic trypanosomatids alternate between invertebrate and vertebrate hosts throughout their lifecycles, and different developmental stages can live inside the host cells and circulate in the bloodstream or in the insect gut. Trypanosomatids have a classical eukaryotic ultrastructural organization with some of the same main organelles found in mammalian host cells, while also containing special structures and organelles that are absent in other eukaryotic organisms. For example, the mitochondrion is ramified and contains a region known as the kinetoplast, which houses the mitochondrial DNA. Also, the glycosomes are specialized peroxisomes containing glycolytic pathway enzymes. Moreover, a layer of subpellicular microtubules confers mechanic rigidity to the cell. Some of these structures have been investigated to determine their function and identify potential enzymes and metabolic pathways that may constitute targets for new chemotherapeutic drugs.
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Affiliation(s)
- Juliany Cola Fernandes Rodrigues
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil,
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12
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Acriflavine treatment promotes dyskinetoplasty in Trypanosoma cruzi as revealed by ultrastructural analysis. Parasitology 2013; 140:1422-31. [DOI: 10.1017/s0031182013001029] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
SUMMARYTrypanosomatid mitochondrial DNA is structured as a giant network of thousands of interlocked DNA molecules enclosed within the kinetoplast. The structure and replication mechanism of kinetoplast DNA (kDNA) is unique, thereby making it an excellent chemotherapeutic target. Alteration in the structural organization of kDNA can give rise to dyskinetoplastic (Dk) strains. In Dk cells, the kDNA is dispersed in clumps throughout the mitochondrial matrix and not organized into a network. In this work, Trypanosoma cruzi epimastigotes were treated with acriflavine, a DNA intercalating drug, which promoted a decrease in cell proliferation and induced the appearance of Dk protozoa. In treated cells, the kinetoplast lost its normal disc-shaped structure because the fibrillar arrangement was reduced to a compact, amorphous mass within the mitochondrion. Moreover, basic proteins associated with kDNA were redistributed throughout the Dk protozoal kinetoplast. We sought to understand how the disruption of the kDNA leads to the emergence of the Dk phenotype with atomic force microscopy (AFM) analysis of isolated networks. Our results demonstrate that the detachment of minicircles from the kDNA disk promotes the disassembly of the network, thereby generating Dk cells. Our data strongly suggest that acriflavine inhibits T. cruzi multiplication by interfering with kDNA replication.
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13
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Abstract
One of the most fascinating and unusual features of trypanosomatids, parasites that cause disease in many tropical countries, is their mitochondrial DNA. This genome, known as kinetoplast DNA (kDNA), is organized as a single, massive DNA network formed of interlocked DNA rings. In this review, we discuss recent studies on kDNA structure and replication, emphasizing recent developments on replication enzymes, how the timing of kDNA synthesis is controlled during the cell cycle, and the machinery for segregating daughter networks after replication.
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Affiliation(s)
- Robert E Jensen
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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14
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Schamber-Reis BLF, Nardelli S, Régis-Silva CG, Campos PC, Cerqueira PG, Lima SA, Franco GR, Macedo AM, Pena SDJ, Cazaux C, Hoffmann JS, Motta MCM, Schenkman S, Teixeira SMR, Machado CR. DNA polymerase beta from Trypanosoma cruzi is involved in kinetoplast DNA replication and repair of oxidative lesions. Mol Biochem Parasitol 2012; 183:122-31. [PMID: 22369885 DOI: 10.1016/j.molbiopara.2012.02.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Revised: 02/09/2012] [Accepted: 02/14/2012] [Indexed: 12/18/2022]
Abstract
Specific DNA repair pathways from Trypanosoma cruzi are believed to protect genomic DNA and kinetoplast DNA (kDNA) from mutations. Particular pathways are supposed to operate in order to repair nucleotides oxidized by reactive oxygen species (ROS) during parasite infection, being 7,8-dihydro-8-oxoguanine (8oxoG) a frequent and highly mutagenic base alteration. If unrepaired, 8oxoG can lead to cytotoxic base transversions during DNA replication. In mammals, DNA polymerase beta (Polβ) is mainly involved in base excision repair (BER) of oxidative damage. However its biological role in T. cruzi is still unknown. We show, by immunofluorescence localization, that T. cruzi DNA polymerase beta (Tcpolβ) is restricted to the antipodal sites of kDNA in replicative epimastigote and amastigote developmental stages, being strictly localized to kDNA antipodal sites between G1/S and early G2 phase in replicative epimastigotes. Nevertheless, this polymerase was detected inside the mitochondrial matrix of trypomastigote forms, which are not able to replicate in culture. Parasites over expressing Tcpolβ showed reduced levels of 8oxoG in kDNA and an increased survival after treatment with hydrogen peroxide when compared to control cells. However, this resistance was lost after treating Tcpolβ overexpressors with methoxiamine, a potent BER inhibitor. Curiously, a presumed DNA repair focus containing Tcpolβ was identified in the vicinity of kDNA of cultured wild type epimastigotes after treatment with hydrogen peroxide. Taken together our data suggest participation of Tcpolβ during kDNA replication and repair of oxidative DNA damage induced by genotoxic stress in this organelle.
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Affiliation(s)
- Bruno Luiz Fonseca Schamber-Reis
- Department of Biochemistry and Immunology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil
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15
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Wang J, Englund PT, Jensen RE. TbPIF8, a Trypanosoma brucei protein related to the yeast Pif1 helicase, is essential for cell viability and mitochondrial genome maintenance. Mol Microbiol 2012; 83:471-85. [PMID: 22220754 DOI: 10.1111/j.1365-2958.2011.07938.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The trypanosome mitochondrial genome, kinetoplast DNA (kDNA), is a massive network of interlocked DNA rings, including several thousand minicircles and dozens of maxicircles. The unusual complexity of kDNA would indicate that numerous proteins must be involved in its condensation, replication, segregation and gene expression. During our investigation of trypanosome mitochondrial PIF1-like helicases, we found that TbPIF8 is the smallest and most divergent. It lacks some conserved helicase domains, thus implying that unlike other mitochondrial PIF1-like helicases, this protein may have no enzymatic activity. TbPIF8 is positioned on the distal face of kDNA disk and its localization patterns vary with different kDNA replication stages. Stem-loop RNAi of TbPIF8 arrests cell growth and causes defects in kDNA segregation. RNAi of TbPIF8 causes only limited kDNA shrinkage but the networks become disorganized. Electron microcopy of thin sections of TbPIF8-depleted cells shows heterogeneous electron densities in the kinetoplast disk. Although we do not yet know its exact function, we conclude that TbPIF8 is essential for cell viability and is important for maintenance of kDNA.
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Affiliation(s)
- Jianyang Wang
- Departments of Biological Chemistry Cell Biology, Johns Hopkins Medical School, Baltimore, MD 21205, USA
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The kinetoplast duplication cycle in Trypanosoma brucei is orchestrated by cytoskeleton-mediated cell morphogenesis. Mol Cell Biol 2010; 31:1012-21. [PMID: 21173163 DOI: 10.1128/mcb.01176-10] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mitochondrial DNA of Trypanosoma brucei is organized in a complex structure called the kinetoplast. In this study, we define the complete kinetoplast duplication cycle in T. brucei based on three-dimensional reconstructions from serial-section electron micrographs. This structural model was enhanced by analyses of the replication process of DNA maxi- and minicircles. Novel insights were obtained about the earliest and latest stages of kinetoplast duplication. We show that kinetoplast S phase occurs concurrently with the repositioning of the new basal body from the anterior to the posterior side of the old flagellum. This emphasizes the role of basal body segregation in kinetoplast division and suggests a possible mechanism for driving the rotational movement of the kinetoplast during minicircle replication. Fluorescence in situ hybridization with minicircle- and maxicircle-specific probes showed that maxicircle DNA is stretched out between segregated minicircle networks, indicating that maxicircle segregation is a late event in the kinetoplast duplication cycle. This new view of the complexities of kinetoplast duplication emphasizes the dependencies between the dynamic remodelling of the cytoskeleton and the inheritance of the mitochondrial genome.
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17
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The killing of African trypanosomes by ethidium bromide. PLoS Pathog 2010; 6:e1001226. [PMID: 21187912 PMCID: PMC3002999 DOI: 10.1371/journal.ppat.1001226] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Accepted: 11/11/2010] [Indexed: 11/19/2022] Open
Abstract
Introduced in the 1950s, ethidium bromide (EB) is still used as an anti-trypanosomal drug for African cattle although its mechanism of killing has been unclear and controversial. EB has long been known to cause loss of the mitochondrial genome, named kinetoplast DNA (kDNA), a giant network of interlocked minicircles and maxicircles. However, the existence of viable parasites lacking kDNA (dyskinetoplastic) led many to think that kDNA loss could not be the mechanism of killing. When recent studies indicated that kDNA is indeed essential in bloodstream trypanosomes and that dyskinetoplastic cells survive only if they have a compensating mutation in the nuclear genome, we investigated the effect of EB on kDNA and its replication. We here report some remarkable effects of EB. Using EM and other techniques, we found that binding of EB to network minicircles is low, probably because of their association with proteins that prevent helix unwinding. In contrast, covalently-closed minicircles that had been released from the network for replication bind EB extensively, causing them, after isolation, to become highly supertwisted and to develop regions of left-handed Z-DNA (without EB, these circles are fully relaxed). In vivo, EB causes helix distortion of free minicircles, preventing replication initiation and resulting in kDNA loss and cell death. Unexpectedly, EB also kills dyskinetoplastic trypanosomes, lacking kDNA, by inhibiting nuclear replication. Since the effect on kDNA occurs at a >10-fold lower EB concentration than that on nuclear DNA, we conclude that minicircle replication initiation is likely EB's most vulnerable target, but the effect on nuclear replication may also contribute to cell killing.
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Lacomble S, Vaughan S, Gadelha C, Morphew MK, Shaw MK, McIntosh JR, Gull K. Basal body movements orchestrate membrane organelle division and cell morphogenesis in Trypanosoma brucei. J Cell Sci 2010; 123:2884-91. [PMID: 20682637 DOI: 10.1242/jcs.074161] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The defined shape and single-copy organelles of Trypanosoma brucei mean that it provides an excellent model in which to study how duplication and segregation of organelles is interfaced with morphogenesis of overall cell shape and form. The centriole or basal body of eukaryotic cells is often seen to be at the centre of such processes. We have used a combination of electron microscopy and electron tomography techniques to provide a detailed three-dimensional view of duplication of the basal body in trypanosomes. We show that the basal body duplication and maturation cycle exerts an influence on the intimately associated flagellar pocket membrane system that is the portal for secretion and uptake from this cell. At the start of the cell cycle, a probasal body is positioned anterior to the basal body of the existing flagellum. At the G1-S transition, the probasal body matures, elongates and invades the pre-existing flagellar pocket to form the new flagellar axoneme. The new basal body undergoes a spectacular anti-clockwise rotation around the old flagellum, while its short new axoneme is associated with the pre-existing flagellar pocket. This rotation and subsequent posterior movements results in division of the flagellar pocket and ultimately sets parameters for subsequent daughter cell morphogenesis.
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Affiliation(s)
- Sylvain Lacomble
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK
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Liu B, Yildirir G, Wang J, Tolun G, Griffith JD, Englund PT. TbPIF1, a Trypanosoma brucei mitochondrial DNA helicase, is essential for kinetoplast minicircle replication. J Biol Chem 2010; 285:7056-7066. [PMID: 20042610 PMCID: PMC2844155 DOI: 10.1074/jbc.m109.084038] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 12/22/2009] [Indexed: 12/17/2023] Open
Abstract
Kinetoplast DNA, the trypanosome mitochondrial genome, is a network of interlocked DNA rings including several thousand minicircles and a few dozen maxicircles. Minicircles replicate after release from the network, and their progeny reattach. Remarkably, trypanosomes have six mitochondrial DNA helicases related to yeast PIF1 helicase. Here we report that one of the six, TbPIF1, functions in minicircle replication. RNA interference (RNAi) of TbPIF1 causes a growth defect and kinetoplast DNA loss. Minicircle replication intermediates decrease during RNAi, and there is an accumulation of multiply interlocked, covalently closed minicircle dimers (fraction U). In studying the significance of fraction U, we found that this species also accumulates during RNAi of mitochondrial topoisomerase II. These data indicate that one function of TbPIF1 is an involvement, together with topoisomerase II, in the segregation of minicircle progeny.
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Affiliation(s)
- Beiyu Liu
- From the Department of Biological Chemistry, Johns Hopkins Medical School, Baltimore, Maryland 21205 and
| | - Gokben Yildirir
- From the Department of Biological Chemistry, Johns Hopkins Medical School, Baltimore, Maryland 21205 and
| | - Jianyang Wang
- From the Department of Biological Chemistry, Johns Hopkins Medical School, Baltimore, Maryland 21205 and
| | - Gökhan Tolun
- the Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Jack D. Griffith
- the Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Paul T. Englund
- From the Department of Biological Chemistry, Johns Hopkins Medical School, Baltimore, Maryland 21205 and
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Inheritance of DNA transferred from American trypanosomes to human hosts. PLoS One 2010; 5:e9181. [PMID: 20169193 PMCID: PMC2820539 DOI: 10.1371/journal.pone.0009181] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Accepted: 01/04/2010] [Indexed: 01/09/2023] Open
Abstract
Interspecies DNA transfer is a major biological process leading to the accumulation of mutations inherited by sexual reproduction among eukaryotes. Lateral DNA transfer events and their inheritance has been challenging to document. In this study we modified a thermal asymmetric interlaced PCR by using additional targeted primers, along with Southern blots, fluorescence techniques, and bioinformatics, to identify lateral DNA transfer events from parasite to host. Instances of naturally occurring human infections by Trypanosoma cruzi are documented, where mitochondrial minicircles integrated mainly into retrotransposable LINE-1 of various chromosomes. The founders of five families show minicircle integrations that were transferred vertically to their progeny. Microhomology end-joining of 6 to 22 AC-rich nucleotide repeats in the minicircles and host DNA mediates foreign DNA integration. Heterogeneous minicircle sequences were distributed randomly among families, with diversity increasing due to subsequent rearrangement of inserted fragments. Mosaic recombination and hitchhiking on retrotransposition events to different loci were more prevalent in germ line as compared to somatic cells. Potential new genes, pseudogenes, and knockouts were identified. A pathway of minicircle integration and maintenance in the host genome is suggested. Thus, infection by T. cruzi has the unexpected consequence of increasing human genetic diversity, and Chagas disease may be a fortuitous share of negative selection. This demonstration of contemporary transfer of eukaryotic DNA to the human genome and its subsequent inheritance by descendants introduces a significant change in the scientific concept of evolutionary biology and medicine.
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Particularities of mitochondrial structure in parasitic protists (Apicomplexa and Kinetoplastida). Int J Biochem Cell Biol 2009; 41:2069-80. [PMID: 19379828 DOI: 10.1016/j.biocel.2009.04.007] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Revised: 04/07/2009] [Accepted: 04/09/2009] [Indexed: 11/20/2022]
Abstract
Without mitochondria, eukaryotic cells would depend entirely on anaerobic glycolysis for ATP generation. This also holds true for protists, both free-living and parasitic. Parasitic protists include agents of human and animal diseases that have a huge impact on world populations. In the phylum Apicomplexa, several species of Plasmodium cause malaria, whereas Toxoplasma gondii is a cosmopolite parasite found on all continents. Flagellates of the order Kinetoplastida include the genera Leishmania and Trypanosoma causative agents of human leishmaniasis and (depending on the species) African trypanosomiasis and Chagas disease. Although clearly distinct in many aspects, the members of these two groups bear a single and usually well developed mitochondrion. The single mitochondrion of Apicomplexa has a dense matrix and many cristae with a circular profile. The organelle is even more peculiar in the order Kinetoplastida, exhibiting a condensed network of DNA at a specific position, always close to the flagellar basal body. This arrangement is known as Kinetoplast and the name of the order derived from it. Kinetoplastids also bear glycosomes, peroxisomes that concentrate enzymes of the glycolytic cycle. Mitochondrial volume and activity is maximum when glycosomal is low and vice versa. In both Apicomplexa and trypanosomatids, mitochondria show particularities that are absent in other eukaryotic organisms. These peculiar features make them an attractive target for therapeutic drugs for the diseases they cause.
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Lindsay ME, Gluenz E, Gull K, Englund PT. A new function of Trypanosoma brucei mitochondrial topoisomerase II is to maintain kinetoplast DNA network topology. Mol Microbiol 2008; 70:1465-76. [PMID: 19019151 DOI: 10.1111/j.1365-2958.2008.06493.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mitochondrial genome of Trypanosoma brucei, called kinetoplast DNA, is a network of topologically interlocked DNA rings including several thousand minicircles and a few dozen maxicircles. Kinetoplast DNA synthesis involves release of minicircles from the network, replication of the free minicircles and reattachment of the progeny. Here we report a new function of the mitochondrial topoisomerase II (TbTOP2mt). Although traditionally thought to reattach minicircle progeny to the network, here we show that it also mends holes in the network created by minicircle release. Network holes are not observed in wild-type cells, implying that this mending reaction is normally efficient. However, RNAi of TbTOP2mt causes holes to persist and enlarge, leading to network fragmentation. Remarkably, these network fragments remain associated within the mitochondrion, and many appear to be appropriately packed at the local level, even as the overall kinetoplast organization is dramatically altered. The deficiency in mending holes is temporally the earliest observable defect in the complex TbTOP2mt RNAi phenotype.
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Affiliation(s)
- Megan E Lindsay
- Department of Biological Chemistry, Johns Hopkins Medical School, Baltimore, MD, USA
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Selvapandiyan A, Duncan R, Mendez J, Kumar R, Salotra P, Cardo LJ, Nakhasi HL. A Leishmania minicircle DNA footprint assay for sensitive detection and rapid speciation of clinical isolates. Transfusion 2008; 48:1787-98. [PMID: 18564397 DOI: 10.1111/j.1537-2995.2008.01798.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Diversity in clinical outcome, due to different species of Leishmania, and its presence in asymptomatic blood donors in endemic areas warrant development of methods that are sensitive and can rapidly identify infecting species. STUDY DESIGN AND METHODS The kinetoplast minicircle DNA is known to have heterogeneity in sequence and is present in many thousands of copies in Leishmania. Fluorescence-based polymerase chain reaction (PCR) was used to amplify minicircle DNA from six Leishmania species from different geographic locations. The sequences were then used to construct a phylogenetic tree. Speciation of 46 blinded parasite clinical isolates from various geographic regions was validated using the assay. RESULTS Analysis displayed a distinct cluster for each species or strain. Forty-three of 46 isolates were correctly assigned to the same species identified by isoenzyme electrophoresis. The three untyped isolates were all either new species or samples from a unique geographic region. The minicircles of the three isolates formed new clusters in the tree analysis. Using minicircle DNA as PCR target, the sensitivity of the parasite detection in the spiked blood samples was five parasites per mL. CONCLUSION Increased sensitivity and speciation without the need for parasite culture will be useful for diagnosis and treatment in clinical settings.
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Affiliation(s)
- Angamuthu Selvapandiyan
- Division of Emerging and Transfusion Transmitted Diseases, Office of Blood Research and Review, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland, USA.
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24
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Souza WD. Electron microscopy of trypanosomes: a historical view. Mem Inst Oswaldo Cruz 2008; 103:313-25. [DOI: 10.1590/s0074-02762008000400001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Accepted: 06/18/2008] [Indexed: 11/22/2022] Open
Affiliation(s)
- Wanderley de Souza
- Universidade Federal do Rio de Janeiro, Brasil; Normalização e Qualidade Industrial, Brasil
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Li Z, Lindsay ME, Motyka SA, Englund PT, Wang CC. Identification of a bacterial-like HslVU protease in the mitochondria of Trypanosoma brucei and its role in mitochondrial DNA replication. PLoS Pathog 2008; 4:e1000048. [PMID: 18421378 PMCID: PMC2277460 DOI: 10.1371/journal.ppat.1000048] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Accepted: 03/20/2008] [Indexed: 12/03/2022] Open
Abstract
ATP-dependent protease complexes are present in all living organisms, including the 26S proteasome in eukaryotes, Archaea, and Actinomycetales, and the HslVU protease in eubacteria. The structure of HslVU protease resembles that of the 26S proteasome, and the simultaneous presence of both proteases in one organism was deemed unlikely. However, HslVU homologs have been identified recently in some primordial eukaryotes, though their potential function remains elusive. We characterized the HslVU homolog from Trypanosoma brucei, a eukaryotic protozoan parasite and the causative agent of human sleeping sickness. TbHslVU has ATP-dependent peptidase activity and, like its bacterial counterpart, has essential lysine and N-terminal threonines in the catalytic subunit. By epitope tagging, TbHslVU localizes to mitochondria and is associated with the mitochondrial genome, kinetoplast DNA (kDNA). RNAi of TbHslVU dramatically affects the kDNA by causing over-replication of the minicircle DNA. This leads to defects in kDNA segregation and, subsequently, to continuous network growth to an enormous size. Multiple discrete foci of nicked/gapped minicircles are formed on the periphery of kDNA disc, suggesting a failure in repairing the gaps in the minicircles for kDNA segregation. TbHslVU is a eubacterial protease identified in the mitochondria of a eukaryote. It has a novel function in regulating mitochondrial DNA replication that has never been observed in other organisms. ATP-dependent protein-hydrolyzing enzyme complexes are present in all living organisms, including the 26S proteasome in eukaryotes and the HslVU complex in bacteria. A simultaneous presence of both complexes in an organism was originally deemed unlikely until some HslVU homologs were found in certain ancient eukaryotes, though their potential function in these organisms remains unclear. We characterized an HslVU complex in Trypanosoma brucei, a protozoan parasite that causes human sleeping sickness in Africa. The complex is an active enzyme localized to the mitochondria of the parasite and closely associated with the mitochondrial DNA complex, which consists of several thousand small circular DNAs and a few dozen mitochondrial genomic DNAs. Depletion of this HslVU from the parasite resulted in a continuous synthesis of the small circular DNA, which led to aberrant segregation and incessant growth of the mitochondrial DNA complex to an enormous size that eventually blocks cell division. This novel HslVU function, which has not been observed in other organisms previously, could be a potential target for anti-sleeping sickness chemotherapy.
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Affiliation(s)
- Ziyin Li
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California, United States of America
| | - Megan E. Lindsay
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Shawn A. Motyka
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Paul T. Englund
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Ching C. Wang
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California, United States of America
- * E-mail:
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Effect of hydroxyurea on procyclic Trypanosoma brucei: an unconventional mechanism for achieving synchronous growth. EUKARYOTIC CELL 2007; 7:425-8. [PMID: 18083826 DOI: 10.1128/ec.00369-07] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Procyclic Trypanosoma brucei cells were synchronized with 0.2 mM hydroxyurea. The cells did not arrest at the G(1)/S boundary but proceeded through one round of replication and arrested near the end of S phase. The mitochondrial genome (kinetoplast DNA network) replicated, forming two progeny networks, but the repair of minicircle gaps was inhibited.
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27
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Zhao Z, Lindsay ME, Roy Chowdhury A, Robinson DR, Englund PT. p166, a link between the trypanosome mitochondrial DNA and flagellum, mediates genome segregation. EMBO J 2007; 27:143-54. [PMID: 18059470 DOI: 10.1038/sj.emboj.7601956] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Accepted: 11/20/2007] [Indexed: 11/09/2022] Open
Abstract
Kinetoplast DNA (kDNA), the trypanosome mitochondrial genome, is a giant network containing several thousand interlocked DNA rings. Within the mitochondrion, kDNA is condensed into a disk-shaped structure positioned near the flagellar basal body. The disk is linked to the basal body by a remarkable transmembrane filament system named the tripartite attachment complex (TAC). Following kDNA replication, the TAC mediates network segregation, pulling the progeny networks into the daughter cells by their linkage to the basal bodies. So far TAC has been characterized only morphologically with no known protein components. By screening an RNAi library, we discovered p166, a protein localizing between the kDNA and basal body in intact cells and in isolated flagellum-kDNA complexes. RNAi of p166 has only small effects on kDNA replication, but it causes profound defects in network segregation. For example, kDNA replication without segregation causes the networks to grow to enormous size. Thus, p166 is the first reported molecular component of the TAC, and its discovery will facilitate study of kDNA segregation machinery at the molecular level.
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Affiliation(s)
- Zhixing Zhao
- Department of Biological Chemistry, Johns Hopkins Medical School, Baltimore, MD 21205, USA
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28
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Hines JC, Ray DS. Structure of discontinuities in kinetoplast DNA-associated minicircles during S phase in Crithidia fasciculata. Nucleic Acids Res 2007; 36:444-50. [PMID: 18039707 PMCID: PMC2241878 DOI: 10.1093/nar/gkm1061] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Kinetoplast DNA (kDNA) is a novel form of mitochondrial DNA consisting of thousands of interlocked minicircles and 20–30 maxicircles. The minicircles replicate free of the kDNA network but nicks and gaps in the newly synthesized strands remain at the time of reattachment to the kDNA network. We show here that the steady-state population of replicated, network-associated minicircles only becomes repaired to the point of having nicks with a 3′OH and 5′deoxyribonucleoside monophosphate during S phase. These nicks represent the origin/terminus of the strand and occur within the replication origins (oriA and oriB) located 180° apart on the minicircle. Minicircles containing a new L strand have a single nick within either oriA or oriB but not in both origins in the same molecule. The discontinuously synthesized H strand contains single nicks within both oriA and oriB in the same molecule implying that discontinuities between the H-strand Okazaki fragments become repaired except for the fragments initiated within the two origins. Nicks in L and H strands at the origins persist throughout S phase and only become ligated as a prelude to network division. The failure to ligate these nicks until just prior to network division is not due to inappropriate termini for ligation.
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Affiliation(s)
- Jane C Hines
- Molecular Biology Institute and Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, CA 90095-1570, USA
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