1
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Nascimento JF, Souza ROO, Alencar MB, Marsiccobetre S, Murillo AM, Damasceno FS, Girard RBMM, Marchese L, Luévano-Martinez LA, Achjian RW, Haanstra JR, Michels PAM, Silber AM. How much (ATP) does it cost to build a trypanosome? A theoretical study on the quantity of ATP needed to maintain and duplicate a bloodstream-form Trypanosoma brucei cell. PLoS Pathog 2023; 19:e1011522. [PMID: 37498954 PMCID: PMC10409291 DOI: 10.1371/journal.ppat.1011522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 08/08/2023] [Accepted: 06/29/2023] [Indexed: 07/29/2023] Open
Abstract
ATP hydrolysis is required for the synthesis, transport and polymerization of monomers for macromolecules as well as for the assembly of the latter into cellular structures. Other cellular processes not directly related to synthesis of biomass, such as maintenance of membrane potential and cellular shape, also require ATP. The unicellular flagellated parasite Trypanosoma brucei has a complex digenetic life cycle. The primary energy source for this parasite in its bloodstream form (BSF) is glucose, which is abundant in the host's bloodstream. Here, we made a detailed estimation of the energy budget during the BSF cell cycle. As glycolysis is the source of most produced ATP, we calculated that a single parasite produces 6.0 x 1011 molecules of ATP/cell cycle. Total biomass production (which involves biomass maintenance and duplication) accounts for ~63% of the total energy budget, while the total biomass duplication accounts for the remaining ~37% of the ATP consumption, with in both cases translation being the most expensive process. These values allowed us to estimate a theoretical YATP of 10.1 (g biomass)/mole ATP and a theoretical [Formula: see text] of 28.6 (g biomass)/mole ATP. Flagellar motility, variant surface glycoprotein recycling, transport and maintenance of transmembrane potential account for less than 30% of the consumed ATP. Finally, there is still ~5.5% available in the budget that is being used for other cellular processes of as yet unknown cost. These data put a new perspective on the assumptions about the relative energetic weight of the processes a BSF trypanosome undergoes during its cell cycle.
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Affiliation(s)
- Janaina F. Nascimento
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Rodolpho O. O. Souza
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Mayke B. Alencar
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Sabrina Marsiccobetre
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Ana M. Murillo
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Flávia S. Damasceno
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Richard B. M. M. Girard
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Letícia Marchese
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Luis A. Luévano-Martinez
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Renan W. Achjian
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
| | - Jurgen R. Haanstra
- Systems Biology Lab, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Paul A. M. Michels
- School of Biological Sciences, The University of Edinburgh, Edinburgh, United Kingdom
| | - Ariel M. Silber
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo–São Paulo, Brazil
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2
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Ramanantsalama MR, Landrein N, Casas E, Salin B, Blancard C, Bonhivers M, Robinson DR, Dacheux D. TFK1, a basal body transition fibre protein that is essential for cytokinesis in Trypanosoma brucei. J Cell Sci 2022; 135:275643. [PMID: 35588197 DOI: 10.1242/jcs.259893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 05/12/2022] [Indexed: 11/20/2022] Open
Abstract
In Trypanosoma brucei, transition fibres (TF) form a nine-bladed pattern-like structure connecting the base of the flagellum to the flagellar pocket membrane. Despite the characterization of two TF proteins, CEP164C and TbRP2, little is known about the organization of these fibres. Here, we report the identification and characterization of the first kinetoplastid-specific TF protein named TFK1 (Tb927.6.1180). Bioinformatics and functional domain analysis identified three TFK1 distinct domains: an N-terminal domain of an unpredicted function, a coiled-coil domain involved in TFK1-TFK1 interaction and a C-terminal intrinsically disordered region potentially involved in protein interaction. Cellular immuno-localization showed that TFK1 is a newly identified basal body maturation marker. Further, using ultrastructure expansion and immuno-electron microscopies we localized CEP164C and TbRP2 at the TF and TFK1 on the distal appendage matrix of the TF. Importantly, RNAi knockdown of TFK1 in bloodstream form cells induced misplacement of basal bodies, a defect in the furrow or fold generation and eventually cell death. We hypothesize that TFK1 is a basal body positioning specific actor and a key regulator of cytokinesis in the bloodstream form Trypanosoma brucei.
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Affiliation(s)
| | - Nicolas Landrein
- University of Bordeaux, CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Elina Casas
- University of Bordeaux, CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Bénédicte Salin
- University of Bordeaux, CNRS, Microscopy Department IBGC, UMR 5095, F-33000 Bordeaux, France
| | - Corinne Blancard
- University of Bordeaux, CNRS, Microscopy Department IBGC, UMR 5095, F-33000 Bordeaux, France
| | - Mélanie Bonhivers
- University of Bordeaux, CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Derrick R Robinson
- University of Bordeaux, CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
| | - Denis Dacheux
- University of Bordeaux, CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France.,Bordeaux INP, Microbiologie Fondamentale et Pathogénicité, UMR 5234, F-33000 Bordeaux, France
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3
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Mulindwa J, Ssentamu G, Matovu E, Kamanyi Marucha K, Aresta-Branco F, Helbig C, Clayton C. In vitro culture of freshly isolated Trypanosoma brucei brucei bloodstream forms results in gene copy-number changes. PLoS Negl Trop Dis 2021; 15:e0009738. [PMID: 34516555 PMCID: PMC8459984 DOI: 10.1371/journal.pntd.0009738] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 09/23/2021] [Accepted: 08/17/2021] [Indexed: 11/19/2022] Open
Abstract
Most researchers who study unicellular eukaryotes work with an extremely limited number of laboratory-adapted isolates that were obtained from the field decades ago, but the effects of passage in laboratory rodents, and adaptation to in vitro culture, have been little studied. For example, the vast majority of studies of Trypanosoma brucei biology have concentrated on just two strains, Lister 427 and EATRO1125, which were taken from the field over half a century ago and have since have undergone innumerable passages in rodents and culture. We here describe two new Trypanosoma brucei brucei strains. MAK65 and MAK98, which have undergone only 3 rodent passages since isolation from Ugandan cattle. High-coverage sequencing revealed that adaptation of the parasites to culture was accompanied by changes in gene copy numbers. T. brucei has so far been considered to be uniformly diploid, but we also found trisomy of chromosome 5 not only in one Lister 427 culture, but also in the MAK98 field isolate. Trisomy of chromosome 6, and increased copies of other chromosome segments, were also seen in established cultured lines. The two new T. brucei strains should be useful to researchers interested in trypanosome differentiation and pathogenicity. Initial results suggested that the two strains have differing infection patterns in rodents. MAK65 is uniformly diploid and grew more reproducibly in bloodstream-form culture than MAK98.
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Affiliation(s)
- Julius Mulindwa
- Department of Biochemistry and Sports Science, College of Natural Sciences, Makerere University, Kampala, Uganda
| | - Geofrey Ssentamu
- School of Biosecurity, Biotechnical and Laboratory Sciences, College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, Kampala, Uganda
| | - Enock Matovu
- School of Biosecurity, Biotechnical and Laboratory Sciences, College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, Kampala, Uganda
| | | | | | - Claudia Helbig
- Heidelberg University Centre for Molecular Biology (ZMBH), Heidelberg, Germany
| | - Christine Clayton
- Heidelberg University Centre for Molecular Biology (ZMBH), Heidelberg, Germany
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4
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Li B, Zhao Y. Regulation of Antigenic Variation by Trypanosoma brucei Telomere Proteins Depends on Their Unique DNA Binding Activities. Pathogens 2021; 10:pathogens10080967. [PMID: 34451431 PMCID: PMC8402208 DOI: 10.3390/pathogens10080967] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 07/22/2021] [Accepted: 07/27/2021] [Indexed: 01/17/2023] Open
Abstract
Trypanosoma brucei causes human African trypanosomiasis and regularly switches its major surface antigen, Variant Surface Glycoprotein (VSG), to evade the host immune response. Such antigenic variation is a key pathogenesis mechanism that enables T. brucei to establish long-term infections. VSG is expressed exclusively from subtelomere loci in a strictly monoallelic manner, and DNA recombination is an important VSG switching pathway. The integrity of telomere and subtelomere structure, maintained by multiple telomere proteins, is essential for T. brucei viability and for regulating the monoallelic VSG expression and VSG switching. Here we will focus on T. brucei TRF and RAP1, two telomere proteins with unique nucleic acid binding activities, and summarize their functions in telomere integrity and stability, VSG switching, and monoallelic VSG expression. Targeting the unique features of TbTRF and TbRAP1′s nucleic acid binding activities to perturb the integrity of telomere structure and disrupt VSG monoallelic expression may serve as potential therapeutic strategy against T. brucei.
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Affiliation(s)
- Bibo Li
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
- Case Comprehensive Cancer Center, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
- Center for RNA Science and Therapeutics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
- Correspondence: (B.L.); (Y.Z.)
| | - Yanxiang Zhao
- Shenzhen Research Institute, The Hong Kong Polytechnic University, Shenzhen, China
- State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
- Correspondence: (B.L.); (Y.Z.)
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5
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Saha A, Gaurav AK, Pandya UM, Afrin M, Sandhu R, Nanavaty V, Schnur B, Li B. TbTRF suppresses the TERRA level and regulates the cell cycle-dependent TERRA foci number with a TERRA binding activity in its C-terminal Myb domain. Nucleic Acids Res 2021; 49:5637-5653. [PMID: 34048580 PMCID: PMC8191777 DOI: 10.1093/nar/gkab401] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 04/05/2021] [Accepted: 04/29/2021] [Indexed: 02/07/2023] Open
Abstract
Telomere repeat-containing RNA (TERRA) has been identified in multiple organisms including Trypanosoma brucei, a protozoan parasite that causes human African trypanosomiasis. T. brucei regularly switches its major surface antigen, VSG, to evade the host immune response. VSG is expressed exclusively from subtelomeric expression sites, and we have shown that telomere proteins play important roles in the regulation of VSG silencing and switching. In this study, we identify several unique features of TERRA and telomere biology in T. brucei. First, the number of TERRA foci is cell cycle-regulated and influenced by TbTRF, the duplex telomere DNA binding factor in T. brucei. Second, TERRA is transcribed by RNA polymerase I mainly from a single telomere downstream of the active VSG. Third, TbTRF binds TERRA through its C-terminal Myb domain, which also has the duplex DNA binding activity, in a sequence-specific manner and suppresses the TERRA level without affecting its half-life. Finally, levels of the telomeric R-loop and telomere DNA damage were increased upon TbTRF depletion. Overexpression of an ectopic allele of RNase H1 that resolves the R-loop structure in TbTRF RNAi cells can partially suppress these phenotypes, revealing an underlying mechanism of how TbTRF helps maintain telomere integrity.
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Affiliation(s)
- Arpita Saha
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | - Amit Kumar Gaurav
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | - Unnati M Pandya
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | - Marjia Afrin
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | - Ranjodh Sandhu
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | - Vishal Nanavaty
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | - Brittny Schnur
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | - Bibo Li
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA.,Case Comprehensive Cancer Center, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.,Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.,Center for RNA Science and Therapeutics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
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6
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Li B. Keeping Balance Between Genetic Stability and Plasticity at the Telomere and Subtelomere of Trypanosoma brucei. Front Cell Dev Biol 2021; 9:699639. [PMID: 34291053 PMCID: PMC8287324 DOI: 10.3389/fcell.2021.699639] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 06/08/2021] [Indexed: 12/13/2022] Open
Abstract
Telomeres, the nucleoprotein complexes at chromosome ends, are well-known for their essential roles in genome integrity and chromosome stability. Yet, telomeres and subtelomeres are frequently less stable than chromosome internal regions. Many subtelomeric genes are important for responding to environmental cues, and subtelomeric instability can facilitate organismal adaptation to extracellular changes, which is a common theme in a number of microbial pathogens. In this review, I will focus on the delicate and important balance between stability and plasticity at telomeres and subtelomeres of a kinetoplastid parasite, Trypanosoma brucei, which causes human African trypanosomiasis and undergoes antigenic variation to evade the host immune response. I will summarize the current understanding about T. brucei telomere protein complex, the telomeric transcript, and telomeric R-loops, focusing on their roles in maintaining telomere and subtelomere stability and integrity. The similarities and differences in functions and underlying mechanisms of T. brucei telomere factors will be compared with those in human and yeast cells.
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Affiliation(s)
- Bibo Li
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, Cleveland, OH, United States.,Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH, United States.,Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States.,Center for RNA Science and Therapeutics, Case Western Reserve University, Cleveland, OH, United States
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7
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Saha A, Nanavaty VP, Li B. Telomere and Subtelomere R-loops and Antigenic Variation in Trypanosomes. J Mol Biol 2019; 432:4167-4185. [PMID: 31682833 DOI: 10.1016/j.jmb.2019.10.025] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Revised: 10/02/2019] [Accepted: 10/21/2019] [Indexed: 12/12/2022]
Abstract
Trypanosoma brucei is a kinetoplastid parasite that causes African trypanosomiasis, which is fatal if left untreated. T. brucei regularly switches its major surface antigen, VSG, to evade the host immune responses. VSGs are exclusively expressed from subtelomeric expression sites (ESs) where VSG genes are flanked by upstream 70 bp repeats and downstream telomeric repeats. The telomere downstream of the active VSG is transcribed into a long-noncoding RNA (TERRA), which forms RNA:DNA hybrids (R-loops) with the telomeric DNA. At an elevated level, telomere R-loops cause more telomeric and subtelomeric double-strand breaks (DSBs) and increase VSG switching rate. In addition, stabilized R-loops are observed at the 70 bp repeats and immediately downstream of ES-linked VSGs in RNase H defective cells, which also have an increased amount of subtelomeric DSBs and more frequent VSG switching. Although subtelomere plasticity is expected to be beneficial to antigenic variation, severe defects in subtelomere integrity and stability increase cell lethality. Therefore, regulation of the telomere and 70 bp repeat R-loop levels is important for the balance between antigenic variation and cell fitness in T. brucei. In addition, the high level of the active ES transcription favors accumulation of R-loops at the telomere and 70 bp repeats, providing an intrinsic mechanism for local DSB formation, which is a strong inducer of VSG switching.
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Affiliation(s)
- Arpita Saha
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Science and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | - Vishal P Nanavaty
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Science and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | - Bibo Li
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Science and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA; Case Comprehensive Cancer Center, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
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8
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Martínez-Calvillo S, Romero-Meza G, Vizuet-de-Rueda JC, Florencio-Martínez LE, Manning-Cela R, Nepomuceno-Mejía T. Epigenetic Regulation of Transcription in Trypanosomatid Protozoa. Curr Genomics 2018; 19:140-149. [PMID: 29491742 PMCID: PMC5814962 DOI: 10.2174/1389202918666170911163517] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 02/13/2017] [Accepted: 04/18/2017] [Indexed: 12/15/2022] Open
Abstract
The Trypanosomatid family includes flagellated parasites that cause fatal human diseases. Remarkably, protein-coding genes in these organisms are positioned in long tandem arrays that are transcribed polycistronically. However, the knowledge about regulation of transcription initiation and termination in trypanosomatids is scarce. The importance of epigenetic regulation in these processes has become evident in the last years, as distinctive histone modifications and histone variants have been found in transcription initiation and termination regions. Moreover, multiple chromatin-related proteins have been identified and characterized in trypanosomatids, including histone-modifying enzymes, effector complexes, chromatin-remodelling enzymes and histone chaperones. Notably, base J, a modified thymine residue present in the nuclear DNA of trypanosomatids, has been implicated in transcriptional regulation. Here we review the current knowledge on epigenetic control of transcription by all three RNA polymerases in this group of early-diverged eukaryotes.
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Affiliation(s)
- Santiago Martínez-Calvillo
- Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México. Av. de los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Edo. de México, CP 54090, México
| | - Gabriela Romero-Meza
- Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México. Av. de los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Edo. de México, CP 54090, México
| | - Juan C. Vizuet-de-Rueda
- Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México. Av. de los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Edo. de México, CP 54090, México
| | - Luis E. Florencio-Martínez
- Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México. Av. de los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Edo. de México, CP 54090, México
| | - Rebeca Manning-Cela
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, México, D.F., CP 07360, México
| | - Tomás Nepomuceno-Mejía
- Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México. Av. de los Barrios 1, Col. Los Reyes Iztacala, Tlalnepantla, Edo. de México, CP 54090, México
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9
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Albisetti A, Florimond C, Landrein N, Vidilaseris K, Eggenspieler M, Lesigang J, Dong G, Robinson DR, Bonhivers M. Interaction between the flagellar pocket collar and the hook complex via a novel microtubule-binding protein in Trypanosoma brucei. PLoS Pathog 2017; 13:e1006710. [PMID: 29091964 PMCID: PMC5683654 DOI: 10.1371/journal.ppat.1006710] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 11/13/2017] [Accepted: 10/24/2017] [Indexed: 12/16/2022] Open
Abstract
Trypanosoma brucei belongs to a group of unicellular, flagellated parasites that are responsible for human African trypanosomiasis. An essential aspect of parasite pathogenicity is cytoskeleton remodelling, which occurs during the life cycle of the parasite and is accompanied by major changes in morphology and organelle positioning. The flagellum originates from the basal bodies and exits the cell body through the flagellar pocket (FP) but remains attached to the cell body via the flagellum attachment zone (FAZ). The FP is an invagination of the pellicular membrane and is the sole site for endo- and exocytosis. The FAZ is a large complex of cytoskeletal proteins, plus an intracellular set of four specialised microtubules (MtQ) that elongate from the basal bodies to the anterior end of the cell. At the distal end of the FP, an essential, intracellular, cytoskeletal structure called the flagellar pocket collar (FPC) circumvents the flagellum. Overlapping the FPC is the hook complex (HC) (a sub-structure of the previously named bilobe) that is also essential and is thought to be involved in protein FP entry. BILBO1 is the only functionally characterised FPC protein and is necessary for FPC and FP biogenesis. Here, we used a combination of in vitro and in vivo approaches to identify and characterize a new BILBO1 partner protein-FPC4. We demonstrate that FPC4 localises to the FPC, the HC, and possibly to a proximal portion of the MtQ. We found that the C-terminal domain of FPC4 interacts with the BILBO1 N-terminal domain, and we identified the key amino acids required for this interaction. Interestingly, the FPC4 N-terminal domain was found to bind microtubules. Over-expression studies highlight the role of FPC4 in its association with the FPC, HC and FPC segregation. Our data suggest a tripartite association between the FPC, the HC and the MtQ.
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Affiliation(s)
- Anna Albisetti
- University of Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Célia Florimond
- University of Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Nicolas Landrein
- University of Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Keni Vidilaseris
- Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
| | - Marie Eggenspieler
- University of Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Johannes Lesigang
- Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
| | - Gang Dong
- Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria
| | - Derrick Roy Robinson
- University of Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Mélanie Bonhivers
- University of Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
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10
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Jehi SE, Nanavaty V, Li B. Trypanosoma brucei TIF2 and TRF Suppress VSG Switching Using Overlapping and Independent Mechanisms. PLoS One 2016; 11:e0156746. [PMID: 27258069 PMCID: PMC4892550 DOI: 10.1371/journal.pone.0156746] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Accepted: 05/18/2016] [Indexed: 12/04/2022] Open
Abstract
Trypanosoma brucei causes debilitating human African trypanosomiasis and evades the host’s immune response by regularly switching its major surface antigen, VSG, which is expressed exclusively from subtelomeric loci. We previously showed that two interacting telomere proteins, TbTRF and TbTIF2, are essential for cell proliferation and suppress VSG switching by inhibiting DNA recombination events involving the whole active VSG expression site. We now find that TbTIF2 stabilizes TbTRF protein levels by inhibiting their degradation by the 26S proteasome, indicating that decreased TbTRF protein levels in TbTIF2-depleted cells contribute to more frequent VSG switching and eventual cell growth arrest. Surprisingly, although TbTIF2 depletion leads to more subtelomeric DNA double strand breaks (DSBs) that are both potent VSG switching inducers and detrimental to cell viability, TbTRF depletion does not increase the amount of DSBs inside subtelomeric VSG expression sites. Furthermore, expressing an ectopic allele of F2H-TbTRF in TbTIF2 RNAi cells allowed cells to maintain normal TbTRF protein levels for a longer frame of time. This resulted in a mildly better cell growth and partially suppressed the phenotype of increased VSG switching frequency but did not suppress the phenotype of more subtelomeric DSBs in TbTIF2-depleted cells. Therefore, TbTIF2 depletion has two parallel effects: decreased TbTRF protein levels and increased subtelomeric DSBs, both resulting in an acute increased VSG switching frequency and eventual cell growth arrest.
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Affiliation(s)
- Sanaa E. Jehi
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, Ohio, United States of America
| | - Vishal Nanavaty
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, Ohio, United States of America
| | - Bibo Li
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, Ohio, United States of America
- The Rockefeller University, New York, New York, United States of America
- Department of Immunology, Cleveland Clinic Lerner Research Institute, Cleveland, Ohio, United States of America
- Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail:
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11
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Carnes J, Anupama A, Balmer O, Jackson A, Lewis M, Brown R, Cestari I, Desquesnes M, Gendrin C, Hertz-Fowler C, Imamura H, Ivens A, Kořený L, Lai DH, MacLeod A, McDermott SM, Merritt C, Monnerat S, Moon W, Myler P, Phan I, Ramasamy G, Sivam D, Lun ZR, Lukeš J, Stuart K, Schnaufer A. Genome and phylogenetic analyses of Trypanosoma evansi reveal extensive similarity to T. brucei and multiple independent origins for dyskinetoplasty. PLoS Negl Trop Dis 2015; 9:e3404. [PMID: 25568942 PMCID: PMC4288722 DOI: 10.1371/journal.pntd.0003404] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 11/09/2014] [Indexed: 11/18/2022] Open
Abstract
Two key biological features distinguish Trypanosoma evansi from the T. brucei group: independence from the tsetse fly as obligatory vector, and independence from the need for functional mitochondrial DNA (kinetoplast or kDNA). In an effort to better understand the molecular causes and consequences of these differences, we sequenced the genome of an akinetoplastic T. evansi strain from China and compared it to the T. b. brucei reference strain. The annotated T. evansi genome shows extensive similarity to the reference, with 94.9% of the predicted T. b. brucei coding sequences (CDS) having an ortholog in T. evansi, and 94.6% of the non-repetitive orthologs having a nucleotide identity of 95% or greater. Interestingly, several procyclin-associated genes (PAGs) were disrupted or not found in this T. evansi strain, suggesting a selective loss of function in the absence of the insect life-cycle stage. Surprisingly, orthologous sequences were found in T. evansi for all 978 nuclear CDS predicted to represent the mitochondrial proteome in T. brucei, although a small number of these may have lost functionality. Consistent with previous results, the F1FO-ATP synthase γ subunit was found to have an A281 deletion, which is involved in generation of a mitochondrial membrane potential in the absence of kDNA. Candidates for CDS that are absent from the reference genome were identified in supplementary de novo assemblies of T. evansi reads. Phylogenetic analyses show that the sequenced strain belongs to a dominant group of clonal T. evansi strains with worldwide distribution that also includes isolates classified as T. equiperdum. At least three other types of T. evansi or T. equiperdum have emerged independently. Overall, the elucidation of the T. evansi genome sequence reveals extensive similarity of T. brucei and supports the contention that T. evansi should be classified as a subspecies of T. brucei.
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Affiliation(s)
- Jason Carnes
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Atashi Anupama
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Oliver Balmer
- Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Andrew Jackson
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Liverpool, United Kingdom
| | - Michael Lewis
- Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Rob Brown
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Igor Cestari
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Marc Desquesnes
- CIRAD, UMR-InterTryp, Montpellier, France
- Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand
| | - Claire Gendrin
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Christiane Hertz-Fowler
- Centre for Genomic Research, Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Hideo Imamura
- Unit of Molecular Parasitology, Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Alasdair Ivens
- Centre of Immunity, Infection and Evolution, University of Edinburgh, Edinburgh, United Kingdom
| | - Luděk Kořený
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic
- Faculty of Sciences, University of South Bohemia, Centre, České Budějovice (Budweis), Czech Republic
| | - De-Hua Lai
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic
- Faculty of Sciences, University of South Bohemia, Centre, České Budějovice (Budweis), Czech Republic
- Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, and Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, People′s Republic of China
| | - Annette MacLeod
- Wellcome Trust Centre for Molecular Parasitology, Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | | | - Chris Merritt
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Severine Monnerat
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Wonjong Moon
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Peter Myler
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Isabelle Phan
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Gowthaman Ramasamy
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Dhileep Sivam
- Seattle Biomedical Research Institute, Seattle, United States of America
| | - Zhao-Rong Lun
- Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, and Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, People′s Republic of China
- * E-mail: (ZRL); (JL); (KS); (AS)
| | - Julius Lukeš
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic
- Faculty of Sciences, University of South Bohemia, Centre, České Budějovice (Budweis), Czech Republic
- Canadian Institute for Advanced Research, Toronto, Canada
- * E-mail: (ZRL); (JL); (KS); (AS)
| | - Ken Stuart
- Seattle Biomedical Research Institute, Seattle, United States of America
- Department of Global Health, University of Washington, Seattle, United States of America
- * E-mail: (ZRL); (JL); (KS); (AS)
| | - Achim Schnaufer
- Centre of Immunity, Infection and Evolution, University of Edinburgh, Edinburgh, United Kingdom
- Institute of Immunology & Infection Research, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail: (ZRL); (JL); (KS); (AS)
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12
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Cross GAM, Kim HS, Wickstead B. Capturing the variant surface glycoprotein repertoire (the VSGnome) of Trypanosoma brucei Lister 427. Mol Biochem Parasitol 2014; 195:59-73. [PMID: 24992042 DOI: 10.1016/j.molbiopara.2014.06.004] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 06/19/2014] [Accepted: 06/23/2014] [Indexed: 11/30/2022]
Abstract
Trypanosoma brucei evades the adaptive immune response through the expression of antigenically distinct Variant Surface Glycoprotein (VSG) coats. To understand the progression and mechanisms of VSG switching, and to identify the VSGs expressed in populations of trypanosomes, it is desirable to predetermine the available repertoire of VSG genes (the 'VSGnome'). To date, the catalog of VSG genes present in any strain is far from complete and the majority of current information regarding VSGs is derived from the TREU927 strain that is not commonly used as an experimental model. We have assembled, annotated and analyzed 2563 distinct and previously unsequenced genes encoding complete and partial VSGs of the widely used Lister 427 strain of T. brucei. Around 80% of the VSGnome consists of incomplete genes or pseudogenes. Read-depth analysis demonstrated that most VSGs exist as single copies, but 360 exist as two or more indistinguishable copies. The assembled regions include five functional metacyclic VSG expression sites. One third of minichromosome sub-telomeres contain a VSG (64-67 VSGs on ∼96 minichromosomes), of which 85% appear to be functionally competent. The minichromosomal repertoire is very dynamic, differing among clones of the same strain. Few VSGs are unique along their entire length: frequent recombination events are likely to have shaped (and to continue to shape) the repertoire. In spite of their low sequence conservation and short window of expression, VSGs show evidence of purifying selection, with ∼40% of non-synonymous mutations being removed from the population. VSGs show a strong codon-usage bias that is distinct from that of any other group of trypanosome genes. VSG sequences are generally very divergent between Lister 427 and TREU927 strains of T. brucei, but those that are highly similar are not found in 'protected' genomic environments, but may reflect genetic exchange among populations.
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Affiliation(s)
- George A M Cross
- Laboratory of Molecular Parasitology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
| | - Hee-Sook Kim
- Laboratory of Molecular Parasitology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
| | - Bill Wickstead
- Medical School, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK.
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Li B. Telomere components as potential therapeutic targets for treating microbial pathogen infections. Front Oncol 2012; 2:156. [PMID: 23125966 PMCID: PMC3485576 DOI: 10.3389/fonc.2012.00156] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 10/16/2012] [Indexed: 01/12/2023] Open
Abstract
In a number of microbial pathogens that undergoes antigenic variation to evade the host's immune attack, genes encoding surface antigens are located at subtelomeric loci, and recent studies have revealed that telomere components play important roles in regulation of surface antigen expression in several of these pathogens, indicating that telomeres play critical roles in microbial pathogen virulence regulation. Importantly, although telomere protein components and their functions are largely conserved from protozoa to mammals, telomere protein homologs in microbial pathogens and humans have low sequence homology. Therefore, pathogen telomere components are potential drug targets for therapeutic approaches because first, most telomere proteins are essential for pathogens' survival, and second, disruption of pathogens' antigenic variation mechanism would facilitate host's immune system to clear the infection.
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Affiliation(s)
- Bibo Li
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, Cleveland State University Cleveland, OH, USA
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14
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Abstract
Temporal and spatial organization of the nucleus is critical for the control of transcription, mRNA processing and the assembly of ribosomes. This includes the occupancy of specific territories by mammalian chromosomes, the presence of subnuclear compartments such as the nucleolus and Cajal bodies and the division of chromatin between active and inactive states. These latter are commonly associated with the location of DNA within euchromatin and heterochromatin respectively; critically these distinctions arise through modifications to chromatin-associated proteins, including histones, as well as the preferential localization of heterochromatin at the nuclear periphery. Most research on nuclear organization has focused on metazoa and fungi; however, recent technical advances have made more divergent eukaryotes accessible to study, with some surprising results. For example, the organization of heterochromatin is mediated in metazoan nuclei in large part by lamins, the prototypical intermediate filament proteins. Despite the presence of heterochromatin, detected both biochemically and by EM in most eukaryotic organisms, until this year lamins were thought to be restricted to metazoan taxa, and the proteins comprising the lamina in other lineages were unknown. Recent work indicates the presence of lamin orthologs in amoeba, while trypanosomatids possess a large coiled-coil protein, NUP-1, that performs functions analogous to lamins. These data indicate that the presence of a nuclear lamina is substantially more widespread than previously thought, with major implications for the evolution of eukaryotic gene expression mechanisms. We discuss these and other recent findings on the organization of nuclei in diverse organisms, and the implications of these findings for the evolutionary origin of eukaryotes.
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Affiliation(s)
- Mark C Field
- Department of Pathology; University of Cambridge, Cambridge, UK.
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15
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Vink C, Rudenko G, Seifert HS. Microbial antigenic variation mediated by homologous DNA recombination. FEMS Microbiol Rev 2012; 36:917-948. [PMID: 22212019 PMCID: PMC3334452 DOI: 10.1111/j.1574-6976.2011.00321.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 12/12/2011] [Accepted: 12/13/2011] [Indexed: 11/27/2022] Open
Abstract
Pathogenic microorganisms employ numerous molecular strategies in order to delay or circumvent recognition by the immune system of their host. One of the most widely used strategies of immune evasion is antigenic variation, in which immunogenic molecules expressed on the surface of a microorganism are continuously modified. As a consequence, the host is forced to constantly adapt its humoral immune response against this pathogen. An antigenic change thus provides the microorganism with an opportunity to persist and/or replicate within the host (population) for an extended period of time or to effectively infect a previously infected host. In most cases, antigenic variation is caused by genetic processes that lead to the modification of the amino acid sequence of a particular antigen or to alterations in the expression of biosynthesis genes that induce changes in the expression of a variant antigen. Here, we will review antigenic variation systems that rely on homologous DNA recombination and that are found in a wide range of cellular, human pathogens, including bacteria (such as Neisseria spp., Borrelia spp., Treponema pallidum, and Mycoplasma spp.), fungi (such as Pneumocystis carinii) and parasites (such as the African trypanosome Trypanosoma brucei). Specifically, the various DNA recombination-based antigenic variation systems will be discussed with a focus on the employed mechanisms of recombination, the DNA substrates, and the enzymatic machinery involved.
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Affiliation(s)
- Cornelis Vink
- Department of Pediatrics, Erasmus MC, Rotterdam, The Netherlands
| | - Gloria Rudenko
- Division of Cell and Molecular Biology, Imperial College-South Kensington, London, UK
| | - H. Steven Seifert
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
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16
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Epigenetic mechanisms, nuclear architecture and the control of gene expression in trypanosomes. Expert Rev Mol Med 2012; 14:e13. [PMID: 22640744 DOI: 10.1017/erm.2012.7] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The control of gene expression, and more significantly gene cohorts, requires tight transcriptional coordination and is an essential feature of probably all cells. In higher eukaryotes, the mechanisms used involve controlled modifications to both local and global DNA environments, principally through changes in chromatin structure as well as cis-element-driven mechanisms. Although the mechanisms regulating chromatin in terms of transcriptional permissiveness and the relation to developmental programmes and responses to the environment are becoming better understood for animal and fungal cells, it is only just beginning to become clear how these processes operate in other taxa, including the trypanosomatids. Recent advances are now illuminating how African trypanosomes regulate higher-order chromatin structure, and, further, how these mechanisms impact on the expression of major surface antigens that are of fundamental importance to life-cycle progression. It is now apparent that several mechanisms are rather more similar between animal and fungal cells and trypanosomes than it originally appeared, but some aspects do involve gene products unique to trypanosomes. Therefore, both evolutionarily common and novel mechanisms cohabit in trypanosomes, offering both important biological insights and possible therapeutic opportunity.
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17
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Ersfeld K. Nuclear architecture, genome and chromatin organisation in Trypanosoma brucei. Res Microbiol 2011; 162:626-36. [PMID: 21392575 DOI: 10.1016/j.resmic.2011.01.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Accepted: 01/29/2011] [Indexed: 11/29/2022]
Abstract
The nucleus of the human pathogen Trypanosoma brucei not only has unusual chromosomal composition, characterised by the presence of megabase, intermediate and minichromosomes, but also chromosome and gene organisation that is unique amongst eukaryotes. Here I provide an overview of current knowledge of nuclear structure, chromatin organisation and chromosome dynamics during interphase and mitosis. New technologies such as chromatin immunoprecipitation, in combination with new generation sequencing and proteomic analysis of subnuclear fractions, have led to novel insights into the organisation of the nucleus and chromatin. In particular, we are beginning to understand how universal mechanisms of chromatin modifications and nuclear position effects are deployed for parasite-specific functions and are centrally involved in genomic organisation and transcriptional regulation. These advances also have a major impact on progress in understanding the molecular basis of antigenic variation.
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Affiliation(s)
- Klaus Ersfeld
- Department of Biological Sciences and Hull York Medical School, University of Hull, Hull HU6 7RX, UK.
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18
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Abstract
The African trypanosome Trypanosoma brucei is a unicellular parasite which causes African sleeping sickness. Transcription in African trypanosomes displays some unusual features, as most of the trypanosome genome is transcribed as extensive polycistronic RNA Pol II (polymerase II) transcription units that are not transcriptionally regulated. In addition, RNA Pol I is used for transcription of a small subset of protein coding genes in addition to the rDNA (ribosomal DNA). These Pol I-transcribed protein coding genes include the VSG (variant surface glycoprotein) genes. Although a single trypanosome has many hundreds of VSG genes, the active VSG is transcribed in a strictly monoalleleic fashion from one of approx. 15 telomeric VSG ESs (expression sites). Originally, it was thought that chromatin was not involved in the transcriptional control of ESs; however, this view is now being re-evaluated. It has since been shown that the active ES is depleted of nucleosomes compared with silent ESs. In addition, a number of proteins involved in chromatin remodelling or histone modification and which play a role in ES silencing {including TbISWI [T. brucei ISWI (imitation-switch protein)] and DOT1B} have recently been identified. Lastly, the telomere-binding protein TbRAP1 (T. brucei RAP1) has been shown to establish a repressive gradient extending from the ES telomere end up to the ES promoter. We still need to determine which epigenetic factors are involved in ‘marking’ the active ES as part of the counting mechanism of monoallelic exclusion. The challenge will come in determining how these multiple regulatory layers contribute to ES control.
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Denninger V, Fullbrook A, Bessat M, Ersfeld K, Rudenko G. The FACT subunit TbSpt16 is involved in cell cycle specific control of VSG expression sites in Trypanosoma brucei. Mol Microbiol 2010; 78:459-74. [PMID: 20879999 PMCID: PMC3034197 DOI: 10.1111/j.1365-2958.2010.07350.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The African trypanosome Trypanosoma brucei monoallelically expresses one of more than 1000 Variant Surface Glycoprotein (VSG) genes. The active VSG is transcribed from one of about 15 telomeric VSG expression sites (ESs). It is unclear how monoallelic expression of VSG is controlled, and how inactive VSG ESs are silenced. Here, we show that blocking synthesis of the T. brucei FACT subunit TbSpt16 triggers a G2/early M phase cell cycle arrest in both bloodstream and insect form T. brucei. Segregation of T. brucei minichromosomes in these stalled cells is impaired, implicating FACT in maintenance of centromeres. Strikingly, knock-down of TbSpt16 results in 20- to 23-fold derepression of silent VSG ES promoters in bloodstream form T. brucei, with derepression specific to the G2/M cell cycle stage. In insect form T. brucei TbSpt16 knock-down results in 16- to 25-fold VSG ES derepression. Using chromatin immunoprecipitation (ChIP), TbSpt16 was found to be particularly enriched at the promoter region of silent but not active VSG ESs in bloodstream form T. brucei. The chromatin remodeler FACT is therefore implicated in maintenance of repressed chromatin present at silent VSG ES promoters, but is also essential for chromosome segregation presumably through maintenance of functional centromeres.
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Affiliation(s)
- Viola Denninger
- Division of Cell and Molecular Biology, Sir Alexander Fleming Building, Imperial College, South Kensington, London SW72AZ, UK
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Wang QP, Kawahara T, Horn D. Histone deacetylases play distinct roles in telomeric VSG expression site silencing in African trypanosomes. Mol Microbiol 2010; 77:1237-45. [PMID: 20624217 PMCID: PMC2941730 DOI: 10.1111/j.1365-2958.2010.07284.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2010] [Indexed: 01/10/2023]
Abstract
African trypanosomes evade the host immune response through antigenic variation, which is achieved by periodically expressing different variant surface glycoproteins (VSGs). VSG expression is monoallelic such that only one of approximately 15 telomeric VSG expression sites (ESs) is transcribed at a time. Epigenetic regulation is involved in VSG control but our understanding of the mechanisms involved remains incomplete. Histone deacetylases are potential drug targets for diseases caused by protozoan parasites. Here, using recombinant expression we show that the essential Trypanosoma brucei deacetylases, DAC1 (class I) and DAC3 (class II) display histone deacetylase activity. Both DAC1 and DAC3 are nuclear proteins in the bloodstream stage parasite, while only DAC3 remains concentrated in the nucleus in insect-stage cells. Consistent with developmentally regulated localization, DAC1 antagonizes SIR2rp1-dependent telomeric silencing only in the bloodstream form, indicating a conserved role in the control of silent chromatin domains. In contrast, DAC3 is specifically required for silencing at VSG ES promoters in both bloodstream and insect-stage cells. We conclude that DAC1 and DAC3 play distinct roles in subtelomeric gene silencing and that DAC3 represents the first readily druggable target linked to VSG ES control in the African trypanosome.
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Affiliation(s)
- Qiao-Ping Wang
- London School of Hygiene and Tropical MedicineKeppel Street, London WC1E 7HT, UK
- Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, Key Laboratory of Tropical Diseases Control, Ministry of Education, Zhongshan Medical College, Sun Yat-Sen UniversityGuangzhou 510275, China
| | - Taemi Kawahara
- London School of Hygiene and Tropical MedicineKeppel Street, London WC1E 7HT, UK
| | - David Horn
- London School of Hygiene and Tropical MedicineKeppel Street, London WC1E 7HT, UK
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21
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Gene expression in trypanosomatid parasites. J Biomed Biotechnol 2010; 2010:525241. [PMID: 20169133 PMCID: PMC2821653 DOI: 10.1155/2010/525241] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Accepted: 11/04/2009] [Indexed: 12/21/2022] Open
Abstract
The parasites Leishmania spp., Trypanosoma brucei, and Trypanosoma cruzi are the trypanosomatid protozoa that cause the deadly human diseases leishmaniasis, African sleeping sickness, and Chagas disease, respectively. These organisms possess unique mechanisms for gene expression such as constitutive polycistronic transcription of protein-coding genes and trans-splicing. Little is known about either the DNA sequences or the proteins that are involved in the initiation and termination of transcription in trypanosomatids. In silico analyses of the genome databases of these parasites led to the identification of a small number of proteins involved in gene expression. However, functional studies have revealed that trypanosomatids have more general transcription factors than originally estimated. Many posttranslational histone modifications, histone variants, and chromatin modifying enzymes have been identified in trypanosomatids, and recent genome-wide studies showed that epigenetic regulation might play a very important role in gene expression in this group of parasites. Here, we review and comment on the most recent findings related to transcription initiation and termination in trypanosomatid protozoa.
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Lewis MD, Llewellyn MS, Gaunt MW, Yeo M, Carrasco HJ, Miles MA. Flow cytometric analysis and microsatellite genotyping reveal extensive DNA content variation in Trypanosoma cruzi populations and expose contrasts between natural and experimental hybrids. Int J Parasitol 2009; 39:1305-17. [PMID: 19393242 PMCID: PMC2731025 DOI: 10.1016/j.ijpara.2009.04.001] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 04/03/2009] [Accepted: 04/06/2009] [Indexed: 12/05/2022]
Abstract
Trypanosoma cruzi exhibits remarkable genetic heterogeneity. This is evident at the nucleotide level but also structurally, in the form of karyotypic variation and DNA content differences between strains. Although natural populations of T. cruzi are predominantly clonal, hybrid lineages (TcIId and TcIIe) have been identified and hybridisation has been demonstrated in vitro, raising the possibility that genetic exchange may continue to shape the evolution of this pathogen. The mechanism of genetic exchange identified in the laboratory is unusual, apparently involving fusion of diploid parents followed by genome erosion. We investigated DNA content diversity in natural populations of T. cruzi in the context of its genetic subdivisions by using flow cytometric analysis and multilocus microsatellite genotyping to determine the relative DNA content and estimate the ploidy of 54 cloned isolates. The maximum difference observed was 47.5% between strain Tu18 cl2 (TcIIb) and strain C8 cl1 (TcI), which we estimated to be equivalent to ∼73 Mb of DNA. Large DNA content differences were identified within and between discrete typing units (DTUs). In particular, the mean DNA content of TcI strains was significantly less than that for TcII strains (P < 0.001). Comparisons of hybrid DTUs TcIId/IIe with corresponding parental DTUs TcIIb/IIc indicated that natural hybrids are predominantly diploid. We also measured the relative DNA content of six in vitro-generated TcI hybrid clones and their parents. In contrast to TcIId/IIe hybrid strains these experimental hybrids comprised populations of sub-tetraploid organisms with mean DNA contents 1.65–1.72 times higher than the parental organisms. The DNA contents of both parents and hybrids were shown to be relatively stable after passage through a mammalian host, heat shock or nutritional stress. The results are discussed in the context of hybridisation mechanisms in both natural and in vitro settings.
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Colasante C, Peña Diaz P, Clayton C, Voncken F. Mitochondrial carrier family inventory of Trypanosoma brucei brucei: Identification, expression and subcellular localisation. Mol Biochem Parasitol 2009; 167:104-17. [PMID: 19463859 DOI: 10.1016/j.molbiopara.2009.05.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Revised: 05/05/2009] [Accepted: 05/07/2009] [Indexed: 01/23/2023]
Abstract
The mitochondrial carrier family (MCF) is a group of structurally conserved proteins that mediate the transport of a wide range of metabolic intermediates across the mitochondrial inner membrane. In this paper, an overview of the mitochondrial carrier proteins (MCPs) of the early-branching kinetoplastid parasite Trypanosoma brucei brucei is presented. Sequence analysis and phylogenetic reconstruction gave insight into the evolution and conservation of the 24 identified TbMCPs; for most of these, putative transport functions could be predicted. Comparison of the kinetoplastid MCP inventory to those previously reported for other eukaryotes revealed remarkable deviations: T. b. brucei lacks genes encoding some prototypical MCF members, such as the citrate carrier and uncoupling proteins. The in vivo expression of the identified TbMCPs in the two replicating life-cycle forms of T. b. brucei, the bloodstream-form and procyclic-form, was quantitatively assessed at the mRNA level by Northern blot analysis. Immunolocalisation studies confirmed that majority of the 24 identified TbMCPs is found in the mitochondrion of procyclic-form T. b. brucei.
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Affiliation(s)
- Claudia Colasante
- Department of Biological Sciences and Hull York Medical School (HYMS), University of Hull, HU6 7RX Hull, United Kingdom.
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24
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Hertz-Fowler C, Figueiredo LM, Quail MA, Becker M, Jackson A, Bason N, Brooks K, Churcher C, Fahkro S, Goodhead I, Heath P, Kartvelishvili M, Mungall K, Harris D, Hauser H, Sanders M, Saunders D, Seeger K, Sharp S, Taylor JE, Walker D, White B, Young R, Cross GAM, Rudenko G, Barry JD, Louis EJ, Berriman M. Telomeric expression sites are highly conserved in Trypanosoma brucei. PLoS One 2008; 3:e3527. [PMID: 18953401 PMCID: PMC2567434 DOI: 10.1371/journal.pone.0003527] [Citation(s) in RCA: 210] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Accepted: 09/23/2008] [Indexed: 11/27/2022] Open
Abstract
Subtelomeric regions are often under-represented in genome sequences of eukaryotes. One of the best known examples of the use of telomere proximity for adaptive purposes are the bloodstream expression sites (BESs) of the African trypanosome Trypanosoma brucei. To enhance our understanding of BES structure and function in host adaptation and immune evasion, the BES repertoire from the Lister 427 strain of T. brucei were independently tagged and sequenced. BESs are polymorphic in size and structure but reveal a surprisingly conserved architecture in the context of extensive recombination. Very small BESs do exist and many functioning BESs do not contain the full complement of expression site associated genes (ESAGs). The consequences of duplicated or missing ESAGs, including ESAG9, a newly named ESAG12, and additional variant surface glycoprotein genes (VSGs) were evaluated by functional assays after BESs were tagged with a drug-resistance gene. Phylogenetic analysis of constituent ESAG families suggests that BESs are sequence mosaics and that extensive recombination has shaped the evolution of the BES repertoire. This work opens important perspectives in understanding the molecular mechanisms of antigenic variation, a widely used strategy for immune evasion in pathogens, and telomere biology.
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Comini MA, Rettig J, Dirdjaja N, Hanschmann EM, Berndt C, Krauth-Siegel RL. Monothiol Glutaredoxin-1 Is an Essential Iron-Sulfur Protein in the Mitochondrion of African Trypanosomes. J Biol Chem 2008; 283:27785-27798. [DOI: 10.1074/jbc.m802010200] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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26
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Gould MK, Vu XL, Seebeck T, de Koning HP. Propidium iodide-based methods for monitoring drug action in the kinetoplastidae: comparison with the Alamar Blue assay. Anal Biochem 2008; 382:87-93. [PMID: 18722997 DOI: 10.1016/j.ab.2008.07.036] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 07/23/2008] [Accepted: 07/25/2008] [Indexed: 11/19/2022]
Abstract
The urgent need for new drug development for African trypanosomiasis is widely recognized. This requires reliable and informative high-throughput assays. Currently, drug action is determined with a fluorimetric/colorimetric assay based on the metabolism of the dye Alamar Blue (resazurin) by live cells. However, this assay does not easily distinguish between cell death and growth arrest, or supply information about the rate at which test compounds affect these parameters. We report here an alternative fluorimetric assay, based on the interaction of propidium iodide with DNA, that allows either real-time monitoring of cell viability or the generation of EC(50) values at a predetermined time-point. The assay is highly sensitive and fluorescence readings easily correlate to numbers of parasites or DNA content. The EC(50) values were highly similar to those obtained with the standard Alamar Blue assay. The procedure lends itself readily to applications in drug development or resistance monitoring.
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Affiliation(s)
- Matthew K Gould
- Institute of Biomedical and Life Sciences, Division of Infection and Immunity, University of Glasgow, 120 University Place, Glasgow G128TA, UK
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27
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Cooper A, Tait A, Sweeney L, Tweedie A, Morrison L, Turner CMR, MacLeod A. Genetic analysis of the human infective trypanosome Trypanosoma brucei gambiense: chromosomal segregation, crossing over, and the construction of a genetic map. Genome Biol 2008; 9:R103. [PMID: 18570680 PMCID: PMC2481433 DOI: 10.1186/gb-2008-9-6-r103] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Revised: 05/20/2008] [Accepted: 06/22/2008] [Indexed: 11/29/2022] Open
Abstract
A high-resolution genetic linkage map of the STIB 386 strain of Trypanosoma brucei gambiense is presented. Background Trypanosoma brucei is the causative agent of human sleeping sickness and animal trypanosomiasis in sub-Saharan Africa, and it has been subdivided into three subspecies: Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense, which cause sleeping sickness in humans, and the nonhuman infective Trypanosoma brucei brucei. T. b. gambiense is the most clinically relevant subspecies, being responsible for more than 90% of all trypanosomal disease in humans. The genome sequence is now available, and a Mendelian genetic system has been demonstrated in T. brucei, facilitating genetic analysis in this diploid protozoan parasite. As an essential step toward identifying loci that determine important traits in the human-infective subspecies, we report the construction of a high-resolution genetic map of the STIB 386 strain of T. b. gambiense. Results The genetic map was determined using 119 microsatellite markers assigned to the 11 megabase chromosomes. The total genetic map length of the linkage groups was 733.1 cM, covering a physical distance of 17.9 megabases with an average map unit size of 24 kilobases/cM. Forty-seven markers in this map were also used in a genetic map of the nonhuman infective T. b. brucei subspecies, permitting comparison of the two maps and showing that synteny is conserved between the two subspecies. Conclusion The genetic linkage map presented here is the first available for the human-infective trypanosome T. b. gambiense. In combination with the genome sequence, this opens up the possibility of using genetic analysis to identify the loci responsible for T. b. gambiense specific traits such as human infectivity as well as comparative studies of parasite field populations.
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Affiliation(s)
- Anneli Cooper
- Wellcome Centre for Molecular Parasitology, Glasgow Biomedical Research Centre, University Place, Glasgow G12 8TA, UK.
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28
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Fly transmission and mating of Trypanosoma brucei brucei strain 427. Mol Biochem Parasitol 2008; 160:100-6. [PMID: 18524395 PMCID: PMC2442871 DOI: 10.1016/j.molbiopara.2008.04.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2008] [Revised: 04/17/2008] [Accepted: 04/22/2008] [Indexed: 11/21/2022]
Abstract
Like yeast, Trypanosoma brucei is a model organism and has a published genome sequence. Although T. b. brucei strain 427 is used for studies of trypanosome molecular biology, particularly antigenic variation, in many labs worldwide, this strain was not selected for the genome sequencing project as it is monomorphic and unable to complete development in the insect vector. Instead, the fly transmissible, mating competent strain TREU 927 was used for the genome project, but is not as easily grown or genetically manipulable as strain 427; furthermore, recent findings have spread concern on the potential human infectivity of TREU 927. Here we show that a 40-year-old cryopreserved line of strain 427, Variant 3, is fly transmissible and also able to undergo genetic exchange with another strain of T. b. brucei. Comparison of Variant 3 with lab isolates of 427 shows that all have variant surface glycoprotein genes 117, 121 and 221, and identical alleles for 3 microsatellite loci. Therefore, despite some differences in molecular karyotype, there is no doubt that Variant 3 is an ancestral line of present day 427 lab isolates. Since Variant 3 grows fast both as bloodstream forms and procyclics and is readily genetically manipulable, it may prove useful where a fly transmissible version of 427 is required.
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Hartley CL, McCulloch R. Trypanosoma brucei BRCA2 acts in antigenic variation and has undergone a recent expansion in BRC repeat number that is important during homologous recombination. Mol Microbiol 2008; 68:1237-51. [PMID: 18430140 PMCID: PMC2408642 DOI: 10.1111/j.1365-2958.2008.06230.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Antigenic variation in Trypanosoma brucei has selected for the evolution of a massive archive of silent Variant Surface Glycoprotein (VSG) genes, which are activated by recombination into specialized expression sites. Such VSG switching can occur at rates substantially higher than background mutation and is dependent on homologous recombination, a core DNA repair reaction. A key regulator of homologous recombination is BRCA2, a protein that binds RAD51, the enzyme responsible for DNA strand exchange. Here, we show that T. brucei BRCA2 has undergone a recent, striking expansion in the number of BRC repeats, a sequence element that mediates interaction with RAD51. T. brucei BRCA2 mutants are shown to be significantly impaired in antigenic variation and display genome instability. By generating BRCA2 variants with reduced BRC repeat numbers, we show that the BRC expansion is crucial in determining the efficiency of T. brucei homologous recombination and RAD51 localization. Remarkably, however, this appears not to be a major determinant of the activation of at least some VSG genes.
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Affiliation(s)
- Claire L Hartley
- The Wellcome Centre for Molecular Parasitology and Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow Biomedical Research Centre, 120 University Place, Glasgow G12 8TA, UK
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30
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Abstract
Trypanosomatids are protozoan parasites, of interest due to both their disease burden and deeply divergent position within the eukaryotic lineage. The African trypanosome, Trypanosoma brucei, has emerged as a very amenable model system, with a considerable toolbox of methods available, including inducible overexpression, RNA interference, and a completed genome. Here we describe some of the special considerations that need to be addressed when studying trypanosome gene function, and in particular small GTPases; we provide protocols for transfection, RNA interference, overexpression and basic transport assays, in addition to an overview of available vectors, cell lines, and strategies.
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Affiliation(s)
- Mark C Field
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
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31
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Dreesen O, Cross GAM. Telomere length in Trypanosoma brucei. Exp Parasitol 2007; 118:103-10. [PMID: 17910953 PMCID: PMC2233935 DOI: 10.1016/j.exppara.2007.07.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Revised: 07/12/2007] [Accepted: 07/16/2007] [Indexed: 01/09/2023]
Abstract
Trypanosoma brucei thwarts the host immune response by replacing its variant surface glycoprotein (VSG). The actively transcribed VSG is located in one of approximately 20 telomeric expression sites (ES). Antigenic variation can occur by transcriptional switching, reciprocal translocations, or duplicative gene conversion events among ES or with the large repertoire of telomeric and non-telomeric VSG. In recently isolated strains, duplicative gene conversion occurs at a high frequency and predominates, but the switching frequency decreases dramatically upon laboratory-adaptation. Uniquely, T. brucei telomeres grow--apparently indefinitely--at a steady rate of 6-12 base pairs (bp) per population doubling (PD), but the telomere adjacent to an active ES undergoes frequent truncations. Using two-dimensional gel electrophoresis, we demonstrate that all of the chromosome classes of fast-switching and minimally propagated T. brucei have shorter telomeres than extensively propagated Lister 427 clones, suggesting a link between laboratory adaptation, telomere growth, and VSG switching rates.
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Affiliation(s)
| | - George A. M. Cross
- * Corresponding author. Tel.: +1 212-327-7571; fax: +1 212-327-7845. E-mail address:
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32
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Guirnalda P, Murphy NB, Nolan D, Black SJ. Anti-Trypanosoma brucei activity in Cape buffalo serum during the cryptic phase of parasitemia is mediated by antibodies. Int J Parasitol 2007; 37:1391-9. [PMID: 17583714 DOI: 10.1016/j.ijpara.2007.04.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Revised: 04/03/2007] [Accepted: 04/18/2007] [Indexed: 11/24/2022]
Abstract
Cape buffalo are reservoir hosts of African trypanosomes. They rapidly suppress population growth of the highly antigenically variable extracellular haemoprotozoa and subsequently maintain a cryptic infection. Here we use in vitro cultures of trypanosomes cloned from Cape buffalo blood during cryptic infection, as well as related and unrelated trypanosomes, to identify anti-trypanosome components present in cryptic-phase infection serum. Trypanosome clone-specific complement-dependent trypanolytic IgM and IgG arose after appearance of target trypanosomes during cryptic infection. Serum collected late in the cryptic phase of infection contained complement-independent growth-inhibitory IgG which varied in activity among target trypanosomes. Removal of protein A/G-binding IgG from the serum restored its capacity to support trypanosome growth in vitro. Recovered growth-inhibitory IgG reacted with the variable surface glycoprotein (VSG) of parasites most affected by it, and reacted with trypanosome common antigens, notably the endosome-restricted tomato lectin-binding glycoproteins (TL-antigens). The inclusion of purified TL-antigens in culture medium did not affect the trypanosome growth-inhibitory activity of immune Cape buffalo serum. In addition, hyperimmune rabbit IgG against TL-antigens showed little or no binding to intact trypanosomes and did not affect trypanosome growth in vitro although it did react strongly with TL-antigens and trypanosome endosomes. We conclude that antibodies, particularly clone-specific (putatively VSG-specific) antibodies are responsible for the anti-trypanosome activity of cryptic phase infection serum consistent with a dominant role in parasite control in Cape buffalo.
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Affiliation(s)
- Patrick Guirnalda
- Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01003, USA
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33
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Faulkner SD, Oli MW, Kieft R, Cotlin L, Widener J, Shiflett A, Cipriano MJ, Pacocha SE, Birkeland SR, Hajduk SL, McArthur AG. In vitro generation of human high-density-lipoprotein-resistant Trypanosoma brucei brucei. EUKARYOTIC CELL 2007; 5:1276-86. [PMID: 16896212 PMCID: PMC1539141 DOI: 10.1128/ec.00116-06] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The host range of African trypanosomes is influenced by innate protective molecules in the blood of primates. A subfraction of human high-density lipoprotein (HDL) containing apolipoprotein A-I, apolipoprotein L-I, and haptoglobin-related protein is toxic to Trypanosoma brucei brucei but not the human sleeping sickness parasite Trypanosoma brucei rhodesiense. It is thought that T. b. rhodesiense evolved from a T. b. brucei-like ancestor and expresses a defense protein that ablates the antitrypanosomal activity of human HDL. To directly investigate this possibility, we developed an in vitro selection to generate human HDL-resistant T. b. brucei. Here we show that conversion of T. b. brucei from human HDL sensitive to resistant correlates with changes in the expression of the variant surface glycoprotein (VSG) and abolished uptake of the cytotoxic human HDLs. Complete transcriptome analysis of the HDL-susceptible and -resistant trypanosomes confirmed that VSG switching had occurred but failed to reveal the expression of other genes specifically associated with human HDL resistance, including the serum resistance-associated gene (SRA) of T. b. rhodesiense. In addition, we found that while the original active expression site was still utilized, expression of three expression site-associated genes (ESAG) was altered in the HDL-resistant trypanosomes. These findings demonstrate that resistance to human HDLs can be acquired by T. b. brucei.
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Affiliation(s)
- Sara D Faulkner
- Josephine Bay Paul Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA
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Glover L, Alsford S, Beattie C, Horn D. Deletion of a trypanosome telomere leads to loss of silencing and progressive loss of terminal DNA in the absence of cell cycle arrest. Nucleic Acids Res 2007; 35:872-80. [PMID: 17251198 PMCID: PMC1807955 DOI: 10.1093/nar/gkl1100] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Eukaryotic chromosomes are capped with telomeres which allow complete chromosome replication and prevent the ends from being recognized by the repair machinery. The African trypanosome, Trypanosoma brucei, is a protozoan parasite where antigenic variation requires reversible silencing of a repository of telomere-adjacent variant surface glycoprotein (VSG) genes. We have investigated the role of the telomere adjacent to a repressed VSG. In cells lacking telomerase, the rate of telomere-repeat loss appeared to be inversely proportional to telomere length. We therefore constructed strains in which a single telomere could be immediately removed by conditional I-SceI meganuclease cleavage. Following telomere deletion, cells maintain and segregate the damaged chromosome without repairing it. These cells continue to proliferate at the normal rate but progressively lose terminal DNA at the broken end. Although sirtuin-dependent repression is lost along with the telomere, VSG-silencing is preserved. The results provide direct evidence for telomere-dependent repression but suggest a telomere-independent mode of VSG-silencing. They also indicate the absence of a telomere-loss checkpoint in T. brucei.
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Affiliation(s)
| | | | | | - David Horn
- *To whom correspondence should be addressed. Tel: (020) 7927 2352; Fax: (020) 7636 8739; E-mail:
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35
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Kramer S, Klöckner T, Selmayr M, Boshart M. Interstrain sequence comparison, transcript map and clonal genomic rearrangement of a 28 kb locus on chromosome 9 of Trypanosoma brucei. Mol Biochem Parasitol 2006; 151:129-32. [PMID: 17112605 DOI: 10.1016/j.molbiopara.2006.10.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Revised: 09/27/2006] [Accepted: 10/10/2006] [Indexed: 11/23/2022]
Affiliation(s)
- Susanne Kramer
- Ludwig-Maximilians-Universität München, Department of Biology, Section Genetics, Maria-Ward-Str. 1a, D-80638 München, Germany
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36
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Dreesen O, Cross GAM. Telomerase-independent stabilization of short telomeres in Trypanosoma brucei. Mol Cell Biol 2006; 26:4911-9. [PMID: 16782879 PMCID: PMC1489180 DOI: 10.1128/mcb.00212-06] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In cancer cells and germ cells, shortening of chromosome ends is prevented by telomerase. Telomerase-deficient cells have a replicative life span, after which they enter senescence. Senescent cells can give rise to survivors that maintain chromosome ends through recombination-based amplification of telomeric or subtelomeric repeats. We found that in Trypanosoma brucei, critically short telomeres are stable in the absence of telomerase. Telomere stabilization ensured genomic integrity and could have implications for telomere maintenance in human telomerase-deficient cells. Cloning and sequencing revealed 7 to 27 TTAGGG repeats on stabilized telomeres and no changes in the subtelomeric region. Clones with short telomeres were used to study telomere elongation dynamics, which differed dramatically at transcriptionally active and silent telomeres, after restoration of telomerase. We propose that transcription makes the termini of short telomeres accessible for rapid elongation by telomerase and that telomere elongation in T. brucei is not regulated by a protein-counting mechanism. Many minichromosomes were lost after long-term culture in the absence of telomerase, which may reflect their different mitotic segregation properties.
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Affiliation(s)
- Oliver Dreesen
- Laboratory of Molecular Parasitology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
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37
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Callejas S, Leech V, Reitter C, Melville S. Hemizygous subtelomeres of an African trypanosome chromosome may account for over 75% of chromosome length. Genome Res 2006; 16:1109-18. [PMID: 16899654 PMCID: PMC1557766 DOI: 10.1101/gr.5147406] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
African trypanosomes are parasitic protozoa that infect a wide range of mammals, including humans. These parasites remain extracellular in the mammalian bloodstream, where antigenic variation allows them to survive the immune response. The Trypanosoma brucei nuclear genome sequence has been published recently. However, the significant chromosome size polymorphism observed among strains and subspecies of T. brucei, where total DNA content may vary up to 30%, necessitates a comparative study to determine the underlying basis and significance of such variation between parasites. In addition, the sequenced strain (Tb927) presents one of the smallest genomes analyzed among T. brucei isolates; therefore, establishing polymorphic regions will provide essential complementary information to the sequencing project. We have developed a Tb927 high-resolution DNA microarray to study DNA content variation along chromosome I, one of the most size-variable chromosomes, in different strains and subspecies of T. brucei. Results show considerable copy number polymorphism, especially at subtelomeres, but are insufficient to explain the observed size difference. Additional sequencing reveals that >50% of a larger chromosome I consists of arrays of variant surface glycoprotein genes (VSGs), involved in avoidance of acquired immunity. In total, the subtelomeres appear to be three times larger than the diploid core. These results reveal that trypanosomes can utilize subtelomeres for amplification and divergence of gene families to such a remarkable extent that they may constitute most of a chromosome, and that the VSG repertoire may be even larger than reported to date. Further experimentation is required to determine if these results are applicable to all size-variable chromosomes.
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Affiliation(s)
- Sergio Callejas
- Department of Pathology, University of Cambridge, CB2 1QP, Cambridge, United Kingdom
| | - Vanessa Leech
- Department of Pathology, University of Cambridge, CB2 1QP, Cambridge, United Kingdom
| | - Christopher Reitter
- Department of Pathology, University of Cambridge, CB2 1QP, Cambridge, United Kingdom
| | - Sara Melville
- Department of Pathology, University of Cambridge, CB2 1QP, Cambridge, United Kingdom
- Corresponding author.E-mail ; fax +44-1223-333737
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38
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Aitcheson N, Talbot S, Shapiro J, Hughes K, Adkin C, Butt T, Sheader K, Rudenko G. VSG switching in Trypanosoma brucei: antigenic variation analysed using RNAi in the absence of immune selection. Mol Microbiol 2005; 57:1608-22. [PMID: 16135228 PMCID: PMC1618954 DOI: 10.1111/j.1365-2958.2005.04795.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Trypanosoma brucei relies on antigenic variation of its variant surface glycoprotein (VSG) coat for survival. We show that VSG switching can be efficiently studied in vitro using VSG RNAi in place of an immune system to select for switch variants. Contrary to models predicting an instant switch after inhibition of VSG synthesis, switching was not induced by VSG RNAi and occurred at a rate of 10(-4) per division. We find a highly reproducible hierarchy of VSG activation, which appears to be capable of resetting, whereby more than half of the switch events over 12 experiments were to one of two VSGs. We characterized switched clones according to switch mechanism using marker genes in the active VSG expression site (ES). Transcriptional switches between ESs were the preferred switching mechanism, whereby at least 10 of the 17 ESs identified in T. brucei 427 can be functionally active in vitro. We could specifically select for switches mediated by DNA rearrangements by inducing VSG RNAi in the presence of drug selection for the active ES. Most of the preferentially activated VSGs could be activated by multiple mechanisms. This VSG RNAi-based procedure provides a rapid and powerful means for analysing VSG switching in African trypanosomes entirely in vitro.
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Affiliation(s)
| | | | | | | | | | | | | | - Gloria Rudenko
- * To whom correspondence should be addressed. Tel: +44 1865 281 548, FAX: +44 1865 281 894, E-mail:
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39
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Coppel RL, Black CG. Parasite genomes. Int J Parasitol 2005; 35:465-79. [PMID: 15826640 DOI: 10.1016/j.ijpara.2005.01.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2005] [Revised: 02/24/2005] [Accepted: 02/24/2005] [Indexed: 01/01/2023]
Abstract
The availability of genome sequences and the associated transcriptome and proteome mapping projects has revolutionised research in the field of parasitology. As more parasite species are sequenced, comparative and phylogenetic comparisons are improving the quality of gene prediction and annotation. Genome sequences of parasites are also providing important data sets for understanding parasite biology and identifying new vaccine candidates and drug targets. We review some of the preliminary conclusions from examination of parasite genome sequences and discuss some of the bioinformatics approaches taken in this analysis.
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Affiliation(s)
- Ross L Coppel
- Department of Microbiology and the Victorian Bioinformatics Consortium, Monash University, Melbourne, Vic. 3800, Australia.
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40
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Horn D, Barry JD. The central roles of telomeres and subtelomeres in antigenic variation in African trypanosomes. Chromosome Res 2005; 13:525-33. [PMID: 16132817 DOI: 10.1007/s10577-005-0991-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Telomeres and subtelomeres are important to the virulence of a number of pathogens, as they harbour large diverse gene families associated with the maintenance of infection. Evasion of immunity by African trypanosomes involves the differential expression of variant surface glycoproteins (VSGs), which are encoded by a family of >1500 genes and pseudogenes. This silent archive is located subtelomerically and is activated by gene conversion into specialized transcription units, which themselves are subject to silencing by allelic exclusion. Current research addresses the role of telomeres in the conversion and silencing mechanisms and in the diversification of the VSG archive.
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Affiliation(s)
- David Horn
- London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
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Becker M, Aitcheson N, Byles E, Wickstead B, Louis E, Rudenko G. Isolation of the repertoire of VSG expression site containing telomeres of Trypanosoma brucei 427 using transformation-associated recombination in yeast. Genome Res 2004; 14:2319-29. [PMID: 15520294 PMCID: PMC525691 DOI: 10.1101/gr.2955304] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Accepted: 08/14/2004] [Indexed: 11/24/2022]
Abstract
Trypanosoma brucei switches between variant surface glycoproteins (VSGs) allowing immune escape. The active VSG is in one of many telomeric bloodstream form VSG expression sites (BESs), also containing expression site-associated genes (ESAGs) involved in host adaptation. The role of BES sequence diversity in parasite virulence can best be understood through analysis of the full repertoire of BESs from a given T. brucei strain. However, few BESs have been cloned, as telomeres are highly underrepresented in standard libraries. We devised a strategy for isolating the repertoire of T. brucei 427 BES-containing telomeres in Saccaromyces cerevisiae by using transformation-associated recombination (TAR). We isolated 182 T. brucei 427 BES TAR clones, 167 of which could be subdivided into minimally 17 BES groups. This set gives us the first view of the breadth and diversity of BESs from one T. brucei strain. Most BESs ranged between 40 and 70 kb (average, 57 +/- 17 kb) and contained most identified ESAGs. Phylogenetic comparison of the cohort of BES promoter and ESAG6 sequences did not show similar trees, indicating rapid evolution most likely mediated by sequence exchange between BESs. This cloning strategy could be used for any T. brucei strain, facilitating research on the biodiversity of telomeric gene families and host-pathogen interactions.
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Affiliation(s)
- Marion Becker
- Department of Genetics, University of Leicester, University Road, Leicester LE1 7RH, UK
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42
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Abstract
Although the majority of animals and plants, including humans, are dominated by the diploid phase of their life cycle, extensive diversity in ploidy level exists among eukaryotes, with some groups being primarily haploid whereas others alternate between haploid and diploid phases. Previous theory has illuminated conditions that favor the evolution of increased or decreased ploidy but has shed little light on which species should be primarily haploid and which primarily diploid. Here, we report a discovery that emerged from host-parasite models in which ploidy levels were allowed to evolve: selection is more likely to favor diploidy in host species and haploidy in parasite species. Essentially, when parasites must evade a host's immune system or defense response, selection favors parasitic individuals that express a narrow array of antigens and elicitors, thus favoring haploid parasites over diploid parasites. Conversely, when hosts must recognize a parasite before mounting a defensive response, selection favors hosts with a broader arsenal of recognition molecules, thus favoring diploid hosts over haploid hosts. These results are consistent with the predominance of haploidy among parasitic protists.
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Affiliation(s)
- Scott L Nuismer
- Department of Biological Sciences, University of Idaho, Moscow, 83844, USA.
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43
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Ejchel TF, Ramirez MI, Vargas N, Azevedo EB, Elias MC, Zingales B, Schenkman S. The largest subunit of the RNA polymerase II of Trypanosoma cruzi lacks the repeats in the carboxy-terminal domain and is encoded by several genes. Parasitol Int 2004; 52:243-9. [PMID: 14550480 DOI: 10.1016/s1383-5769(03)00009-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The largest subunit of eukaryotic RNA polymerase II (RNA Pol II) of several members of Kinetoplastida order and other early diverging eukaryote contains a serine, tyrosine and proline-rich domain in the carboxyl-terminal instead of the typical heptapeptides repeats found in most eukaryotes. The lack of these repeats seems to reflect the different control of gene transcription found in these organisms. To provide further understanding in these mechanisms, we have characterized the largest subunit of RNA polymerase II (RNA Pol II LSU) in Trypanosoma cruzi. We found that it also lacks the heptapeptide repeats in the carboxy-terminal domain, but is quite similar to the same region in the Trypanosoma brucei enzyme, suggesting a conserved role for this domain. In addition, we found several genes encoding the RNA Pol II in T. cruzi, distributed in different chromosomal bands in several isolates. Two of these genes were entirely sequenced and shown to be quite similar. The presence of several gene copies of the RNA Pol II LSU, also described in African trypanosomes might reflect a gene amplification requirement that appeared early in the evolution of these organisms.
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Affiliation(s)
- Tatiana Flank Ejchel
- Departamento de Microbiologia, Imunologia e Parasitologia Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
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44
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Abstract
The sequencing of eukaryotic genomes has lagged behind sequencing of organisms in the other domains of life, archae and bacteria, primarily due to their greater size and complexity. With recent advances in high-throughput technologies such as robotics and improved computational resources, the number of eukaryotic genome sequencing projects has increased significantly. Among these are a number of sequencing projects of tropical pathogens of medical and veterinary importance, many of which are responsible for causing widespread morbidity and mortality in peoples of developing countries. Uncovering the complete gene complement of these organisms is proving to be of immense value in the development of novel methods of parasite control, such as antiparasitic drugs and vaccines, as well as the development of new diagnostic tools. Combining pathogen genome sequences with the host and vector genome sequences is promising to be a robust method for the identification of host-pathogen interactions. Finally, comparative sequencing of related species, especially of organisms used as model systems in the study of the disease, is beginning to realize its potential in the identification of genes, and the evolutionary forces that shape the genes, that are involved in evasion of the host immune response.
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Affiliation(s)
- Jane M Carlton
- The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20850, USA.
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45
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Hall N, Berriman M, Lennard NJ, Harris BR, Hertz-Fowler C, Bart-Delabesse EN, Gerrard CS, Atkin RJ, Barron AJ, Bowman S, Bray-Allen SP, Bringaud F, Clark LN, Corton CH, Cronin A, Davies R, Doggett J, Fraser A, Grüter E, Hall S, Harper AD, Kay MP, Leech V, Mayes R, Price C, Quail MA, Rabbinowitsch E, Reitter C, Rutherford K, Sasse J, Sharp S, Shownkeen R, MacLeod A, Taylor S, Tweedie A, Turner CMR, Tait A, Gull K, Barrell B, Melville SE. The DNA sequence of chromosome I of an African trypanosome: gene content, chromosome organisation, recombination and polymorphism. Nucleic Acids Res 2003; 31:4864-73. [PMID: 12907729 PMCID: PMC169939 DOI: 10.1093/nar/gkg674] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The African trypanosome, Trypanosoma brucei, causes sleeping sickness in humans in sub-Saharan Africa. Here we report the sequence and analysis of the 1.1 Mb chromosome I, which encodes approximately 400 predicted genes organised into directional clusters, of which more than 100 are located in the largest cluster of 250 kb. A 160-kb region consists primarily of three gene families of unknown function, one of which contains a hotspot for retroelement insertion. We also identify five novel gene families. Indeed, almost 20% of predicted genes are members of families. In some cases, tandemly arrayed genes are 99-100% identical, suggesting an active process of amplification and gene conversion. One end of the chromosome consists of a putative bloodstream-form variant surface glycoprotein (VSG) gene expression site that appears truncated and degenerate. The other chromosome end carries VSG and expression site-associated genes and pseudogenes over 50 kb of subtelomeric sequence where, unusually, the telomere-proximal VSG gene is oriented away from the telomere. Our analysis includes the cataloguing of minor genetic variations between the chromosome I homologues and an estimate of crossing-over frequency during genetic exchange. Genetic polymorphisms are exceptionally rare in sequences located within and around the strand-switches between several gene clusters.
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Affiliation(s)
- Neil Hall
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Matthew Berriman
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Nicola J. Lennard
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Barbara R. Harris
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Christiane Hertz-Fowler
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Emmanuelle N. Bart-Delabesse
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Caroline S. Gerrard
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Rebecca J. Atkin
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Andrew J. Barron
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | | | - Sarah P. Bray-Allen
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Frédéric Bringaud
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Louise N. Clark
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Craig H. Corton
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Ann Cronin
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Robert Davies
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Jonathon Doggett
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Audrey Fraser
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Eric Grüter
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Sarah Hall
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - A. David Harper
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Mike P. Kay
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Vanessa Leech
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Rebecca Mayes
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Claire Price
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Michael A. Quail
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Ester Rabbinowitsch
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Christopher Reitter
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Kim Rutherford
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Jürgen Sasse
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Sarah Sharp
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Ratna Shownkeen
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Annette MacLeod
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Sonya Taylor
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Alison Tweedie
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - C. Michael R. Turner
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Andrew Tait
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Keith Gull
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Bart Barrell
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Sara E. Melville
- The Wellcome Trust Sanger Institute, The Wellcome Trust Genome Campus, Hinxton CB10 1SA, UK,
University of Cambridge Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, UK, Université Victor Segalen Bordeaux II, Rue Léo Saignat 33076 Bordeaux, France, Wellcome Centre for Molecular Parasitology, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, UK, Division of Infection and Immunity, Joseph Black Building, Institute of Biological and Life Science, Glasgow G12 8QQ, UK and Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
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46
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te Vruchte D, Aitcheson N, Rudenko G. Downregulation of Trypanosoma brucei VSG expression site promoters on circular bacterial artificial chromosomes. Mol Biochem Parasitol 2003; 128:123-33. [PMID: 12742579 DOI: 10.1016/s0166-6851(03)00053-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Trypanosoma brucei has about 20 telomeric variant surface glycoprotein (VSG) gene expression sites (ESs), which are downregulated in the insect form. We investigated the transcriptional behaviour of ES promoters on bacterial artificial chromosomes (BACs) containing two different ESs and their flanking regions on fragments of about 140kb. Four different BACs containing either the 221 or the VO2 ES were introduced into insect form T. brucei. The BACs replicated as circular episomes as shown using pulsed field gel (PFG) analysis of DNA exposed to increasing doses of gamma radiation, and digestion with Dam methylation-sensitive restriction enzymes. BAC copy number per cell varied from about 3 for the 221 ES BACs to about 15 for the VO2 ES BACs. Increasing drug selection pressure on the VO2 BAC T. brucei transformants resulted in amplification to about 80 BACs per cell. Although BACs were maintained in the absence of drug selection for at least 56 days, copy number fell and there was no evidence for centromere activity. ES promoters on small plasmid episomes introduced into insect form T. brucei in transient transfections are derepressed. In contrast, ES promoters on large BAC episomes are downregulated both on the original ES BACs, and on ES BACs selected for a drug marker driven by a rDNA promoter fused to the BAC vector. This indicates that downregulation of ES promoters in insect form T. brucei is influenced by genomic context, but does not necessitate proximity to a chromosome end.
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Affiliation(s)
- Daniëlle te Vruchte
- The Peter Medawar Building for Pathogen Research, University of Oxford, South Parks Road, Oxford OX1 3SY, UK
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47
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Hillebrand H, Schmidt A, Krauth-Siegel RL. A second class of peroxidases linked to the trypanothione metabolism. J Biol Chem 2003; 278:6809-15. [PMID: 12466271 DOI: 10.1074/jbc.m210392200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Trypanosoma brucei, the causative agent of African sleeping sickness, has three nearly identical genes encoding cysteine homologues of classical selenocysteine-containing glutathione peroxidases. The proteins are expressed in the mammalian and insect stages of the parasite. One of the genes, which contains a mitochondrial as well as a glycosomal targeting signal has been overexpressed. The recombinant T. brucei peroxidase has a high preference for the trypanothione/tryparedoxin couple as electron donor for the reduction of different hydroperoxides but accepts also T. brucei thioredoxin. The apparent rate constants k(2)' for the regeneration of the reduced enzyme are 2 x 10(5) m(-1) s(-1) with tryparedoxin and 5 x 10(3) m(-1) s(-1) with thioredoxin. No saturation kinetics was observed and the rate-limiting step of the overall reaction is reduction of the hydroperoxide. With glutathione, the peroxidase has marginal activity and reduction of the enzymes becomes limiting with a k(2)' value of 3 m (-1) s(-1). The T. brucei peroxidase, in contrast to the related Trypanosoma cruzi enzyme, also accepts hydrogen peroxide as substrate. The catalytic efficiency of the peroxidase studied here is comparable with that of the peroxiredoxin-like tryparedoxin peroxidases, which shows that trypanosomes possess two distinct peroxidase systems both dependent on the unique dithiol trypanothione.
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Affiliation(s)
- Henning Hillebrand
- Biochemie-Zentrum Heidelberg, Universität Heidelberg, 69120 Heidelberg, Germany
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48
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Alsford NS, Navarro M, Jamnadass HR, Dunbar H, Ackroyd M, Murphy NB, Gull K, Ersfeld K. The identification of circular extrachromosomal DNA in the nuclear genome of Trypanosoma brucei. Mol Microbiol 2003; 47:277-89. [PMID: 12519183 DOI: 10.1046/j.1365-2958.2003.03266.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Nuclear extrachromosomal DNA elements have been identified in several kinetoplastids such as Leishmania and Trypanosoma cruzi, but never in Trypanosoma brucei. They can occur naturally or arise spontaneously as the result of sublethal drug exposure of parasites. In most cases, they are represented as circular elements and are mitotically unstable. In this study we describe the presence of circular DNA in the nucleus of Trypanosoma brucei. This novel type of DNA was termed NR-element (NlaIII repeat element). In contrast to drug-induced episomes in other kinetoplastids, the T. brucei extrachromosomal NR-element is not generated by drug selection. Furthermore, the element is stable during mitosis over many generations. Restriction analysis of tagged NR-element DNA, unusual migration patterns during pulsed field gel electrophoresis (PFGE) and CsCl/ethidium bromide equilibrium centrifugation demonstrates that the NR-element represents circular DNA. Whereas it has been found in all field isolates of the parasites we analysed, it is not detectable in some laboratory strains notably the genome reference strain 927. The DNA sequence of this element is related to a 29 bp repeat present in the subtelomeric region of VSG-bearing chromosomes of T. brucei. It has been suggested that this subtelomeric region is part of a transition zone on chromosomes separating the relatively stable telomeric repeats from the recombinationaly active region downstream of VSG genes. Therefore, we discuss a functional connection between the occurrence of this circular DNA and subtelomeric recombination events in T. brucei.
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MESH Headings
- Animals
- Base Sequence
- Cattle
- Cell Nucleus/genetics
- DNA, Circular/chemistry
- DNA, Circular/genetics
- DNA, Protozoan/chemistry
- DNA, Protozoan/genetics
- Deoxyribonucleases, Type II Site-Specific/metabolism
- Electrophoresis, Gel, Pulsed-Field
- Genome, Protozoan
- Molecular Sequence Data
- Sequence Analysis, DNA
- Telomere/genetics
- Trypanosoma brucei brucei/genetics
- Trypanosomiasis, Bovine/parasitology
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Affiliation(s)
- N S Alsford
- School of Biological Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
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49
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Conway C, Proudfoot C, Burton P, Barry JD, McCulloch R. Two pathways of homologous recombination in Trypanosoma brucei. Mol Microbiol 2002; 45:1687-700. [PMID: 12354234 DOI: 10.1046/j.1365-2958.2002.03122.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
African trypanosomes are unicellular parasites that use DNA recombination to evade the mammalian immune response. They do this in a process called antigenic variation, in which the parasites periodically switch the expression of VSG genes that encode distinct Variant Surface Glycoprotein coats. Recombination is used to move new VSG genes into specialised bloodstream VSG transcription sites. Genetic and molecular evidence has suggested that antigenic variation uses homologous recombination, but the detailed reaction pathways are not understood. In this study, we examine the recombination pathways used by trypanosomes to integrate transformed DNA into their genome, and show that they possess at least two pathways of homologous recombination. The primary mechanism is dependent upon RAD51, but a subsidiary pathway exists that is RAD51-independent. Both pathways contribute to antigenic variation. We show that the RAD51-independent pathway is capable of recombining DNA substrates with very short lengths of sequence homology and in some cases aberrant recombination reactions can be detected using such microhomologies.
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Affiliation(s)
- Colin Conway
- The Wellcome Centre for Molecular Parasitology, The Anderson College, University of Glasgow, UK
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50
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Robinson NP, McCulloch R, Conway C, Browitt A, Barry JD. Inactivation of Mre11 does not affect VSG gene duplication mediated by homologous recombination in Trypanosoma brucei. J Biol Chem 2002; 277:26185-93. [PMID: 12011090 DOI: 10.1074/jbc.m203205200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We demonstrate, by gene deletion analysis, that Mre11 has a critical role in maintaining genomic integrity in Trypanosoma brucei. mre11(-/-) null mutant strains exhibited retarded growth but no delay or disruption of cell cycle progression. They showed also a weak hyporecombination phenotype and the accumulation of gross chromosomal rearrangements, which did not involve sequence translocation, telomere loss, or formation of new telomeres. The trypanosome mre11(-/-) strains were hypersensitive to phleomycin, a mutagen causing DNA double strand breaks (DSBs) but, in contrast to mre11(-/-) null mutants in other organisms and T. brucei rad51(-/-) null mutants, displayed no hypersensitivity to methyl methanesulfonate, which causes point mutations and DSBs. Mre11 therefore is important for the repair of chromosomal damage and DSBs in trypanosomes, although in this organism the intersection of repair pathways appears to differ from that in other organisms. Mre11 inactivation appears not to affect VSG gene switching during antigenic variation of a laboratory strain, which is perhaps surprising given the importance of homologous recombination during this process.
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Affiliation(s)
- Nicholas P Robinson
- Wellcome Centre for Molecular Parasitology, University of Glasgow, Anderson College, 56 Dumbarton Road, Glasgow G11 6NU, Scotland, United Kingdom
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