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Chawla J, Goldowitz I, Oberstaller J, Zhang M, Pires CV, Navarro F, Sollelis L, Wang CCQ, Seyfang A, Dvorin J, Otto TD, Rayner JC, Marti M, Adams JH. Phenotypic Screens Identify Genetic Factors Associated with Gametocyte Development in the Human Malaria Parasite Plasmodium falciparum. Microbiol Spectr 2023; 11:e0416422. [PMID: 37154686 PMCID: PMC10269797 DOI: 10.1128/spectrum.04164-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 03/23/2023] [Indexed: 05/10/2023] Open
Abstract
Transmission of the deadly malaria parasite Plasmodium falciparum from humans to mosquitoes is achieved by specialized intraerythrocytic sexual forms called gametocytes. Though the crucial regulatory mechanisms leading to gametocyte commitment have recently come to light, networks of genes that control sexual development remain to be elucidated. Here, we report a pooled-mutant screen to identify genes associated with gametocyte development in P. falciparum. Our results categorized genes that modulate gametocyte progression as hypoproducers or hyperproducers of gametocytes, and the in-depth analysis of individual clones confirmed phenotypes in sexual commitment rates and putative functions in gametocyte development. We present a new set of genes that have not been implicated in gametocytogenesis before and demonstrate the potential of forward genetic screens in isolating genes impacting parasite sexual biology, an exciting step toward the discovery of new antimalarials for a globally significant pathogen. IMPORTANCE Blocking human-to-vector transmission is an essential step toward malaria elimination. Gametocytes are solely responsible for achieving this transmission and represent an opportunity for therapeutic intervention. While these falciform-shaped parasite stages were first discovered in the 1880s, our understanding of the genetic determinants responsible for their formation and molecular mechanisms that drive their development is limited. In this work, we developed a scalable screening methodology with piggyBac mutants to identify genes that influence the development of gametocytes in the most lethal human malaria parasite, P. falciparum. By doing so, we lay the foundation for large-scale functional genomic studies specifically designed to address remaining questions about sexual commitment, maturation, and mosquito infection in P. falciparum. Such functional genetic screens will serve to expedite the identification of essential pathways and processes for the development of novel transmission-blocking agents.
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Affiliation(s)
- Jyotsna Chawla
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Ilana Goldowitz
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, USA
| | - Jenna Oberstaller
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Min Zhang
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Camilla Valente Pires
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Francesca Navarro
- Boston Children’s Hospital and Harvard Medical School, Harvard Medical School, Boston, Massachusetts, USA
| | - Lauriane Sollelis
- Institute of Infection, Immunity, and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- Institute of Parasitology Zurich, VetSuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Chengqi C. Q. Wang
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Andreas Seyfang
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Jeffrey Dvorin
- Boston Children’s Hospital and Harvard Medical School, Harvard Medical School, Boston, Massachusetts, USA
| | - Thomas D. Otto
- Institute of Infection, Immunity, and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Julian C. Rayner
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Matthias Marti
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, USA
- Institute of Infection, Immunity, and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- Institute of Parasitology Zurich, VetSuisse Faculty, University of Zurich, Zurich, Switzerland
| | - John H. Adams
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, USA
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Characterization of the variable merozoite surface antigen (VMSA) gene family of Babesia orientalis. Parasitol Res 2020; 119:3639-3648. [PMID: 32930858 DOI: 10.1007/s00436-020-06877-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 09/06/2020] [Indexed: 01/01/2023]
Abstract
Due to its wide presence in apicomplexan parasites as well as high polymorphism and antigenic diversity, the variable merozoite surface antigen (VMSA) family in Babesia sp. has attracted increasing attention of researchers. Here, all the reported VMSA genes of Babesia spp. were obtained from GenBank, and multiple alignments were performed by using conserved regions to blast the Babesia orientalis genome database (unpublished data). Five MSA genes (named MSA-2a1, MSA-2a2, MSA-2c1, MSA-1, and MSA-2c2, respectively) were identified, sequenced, and cloned from B. orientalis, which were shown to encode proteins with open reading frames ranging in size from 266 (MSA-2c1) to 317 (MSA-1) amino acids. All the five proteins contain an MSA-2c superfamily conserved domain, with an identical signal peptide and glycosyl phosphatidyl inositol (GPI)-anchor for each of them. The five proteins were also predicted to contain B cell epitopes, with only three for BoMSA-2c1, the smallest protein in the BoVMSA family, while at least six for each of the others. Notably, BoMSA-2a1 has 2 identical copies, a specific phenomenon only present in B. orientalis. This research has determined the MSA genes of B. orientalis and provides a genetic basis for further research of functional genes in B. orientalis.
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Rao PN, Santos JM, Pain A, Templeton TJ, Mair GR. Translational repression of the cpw-wpc gene family in the malaria parasite Plasmodium. Parasitol Int 2016; 65:463-71. [PMID: 27312996 DOI: 10.1016/j.parint.2016.06.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 06/08/2016] [Accepted: 06/10/2016] [Indexed: 12/22/2022]
Abstract
The technical challenges of working with the sexual stages of the malaria parasite Plasmodium have hindered the characterization of sexual stage antigens in the quest for a successful malaria transmission-blocking vaccine. One such predicted and largely uncharacterized group of sexual stage candidate antigens is the CPW-WPC family of proteins. CPW-WPC proteins are named for a characteristic domain that contains two conserved motifs, CPxxW and WPC. Conserved across Apicomplexa, this family is also present earlier in the Alveolata in the free-living, non-parasitophorous, photosynthetic chromerids, Chromera and Vitrella. In Plasmodium falciparum and Plasmodium berghei blood stage parasites, the transcripts of all nine cpw-wpc genes have been detected in gametocytes. RNA immunoprecipitation followed by reverse transcriptase-PCR reveals all P. berghei cpw-wpc transcripts to be bound by the translational repressors DOZI and CITH, and thus are likely under translational control prior to transmission from the rodent host to the mosquito vector in P. berghei. The GFP tagging of two endogenous P. berghei genes confirmed translational silencing in the gametocyte and translation in ookinetes. By establishing a luciferase transgene assay, we show that the 3' untranslated region of PF3D7_1331400 controls protein expression of this reporter in P. falciparum gametocytes. Our analyses suggest that cpw-wpc genes are translationally silenced in gametocytes across Plasmodium spp. and activated during ookinete formation and thus may have a role in transmission to the mosquito.
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Affiliation(s)
- Pavitra N Rao
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY 10065, USA; Programs in Biochemistry, Cell, and Molecular Biology, Weill Graduate School of Medical Sciences of Cornell University, New York, NY 10065, USA
| | - Jorge M Santos
- Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisbon, Portugal
| | - Arnab Pain
- Pathogen Genomics Laboratory, Biological and Environmental Sciences and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah 23955-6900, Saudi Arabia; Global Station for Zoonosis Control, Global Institution for Collaborative Research and Education (GI-CoRE), Hokkaido University, N20 W10 Kita-ku, Sapporo 001-0020, Japan
| | - Thomas J Templeton
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY 10065, USA; Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki 852-8523, Japan.
| | - Gunnar R Mair
- Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisbon, Portugal; Parasitology, Center for Infectious Diseases, University of Heidelberg Medical School, Im Neuenheimer Feld 345, 69120 Heidelberg, Germany.
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Siciliano G, Alano P. Enlightening the malaria parasite life cycle: bioluminescent Plasmodium in fundamental and applied research. Front Microbiol 2015; 6:391. [PMID: 26029172 PMCID: PMC4426725 DOI: 10.3389/fmicb.2015.00391] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 04/16/2015] [Indexed: 12/31/2022] Open
Abstract
The unicellular protozoan parasites of the genus Plasmodium impose on human health worldwide the enormous burden of malaria. The possibility to genetically modify several species of malaria parasites represented a major advance in the possibility to elucidate their biology and is now turning laboratory lines of transgenic Plasmodium into precious weapons to fight malaria. Amongst the various genetically modified plasmodia, transgenic parasite lines expressing bioluminescent reporters have been essential to unveil mechanisms of parasite gene expression and to develop in vivo imaging approaches in mouse malaria models. Mainly the human malaria parasite Plasmodium falciparum and the rodent parasite P. berghei have been engineered to express bioluminescent reporters in almost all the developmental stages of the parasite along its complex life cycle between the insect and the vertebrate hosts. Plasmodium lines expressing conventional and improved luciferase reporters are now gaining a central role to develop cell based assays in the much needed search of new antimalarial drugs and to open innovative approaches for both fundamental and applied research in malaria.
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Affiliation(s)
| | - Pietro Alano
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di SanitàRome, Italy
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Hasenkamp S, Russell K, Ullah I, Horrocks P. Functional analysis of the 5' untranslated region of the phosphoglutamase 2 transcript in Plasmodium falciparum. Acta Trop 2013; 127:69-74. [PMID: 23567550 DOI: 10.1016/j.actatropica.2013.03.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 03/18/2013] [Accepted: 03/20/2013] [Indexed: 01/07/2023]
Abstract
Plasmodium falciparum transcripts contain long untranslated regions (UTR), with some of the longest in any eukaryote that uses monocistronic transcription. Owing to the extreme AT nucleotide bias within the intergenic regions that encode these UTR, attempts to characterise how they are apportioned over genes and to describe their contribution to the absolute and temporal control of gene expression have been limited. Here we describe a study using a typical house-keeping gene that encodes phosphoglutamase 2 (PFD0660w), whose expression is subject to developmentally linked control during intraerythrocytic development. We show that deletion of a significant proportion (80%) of the predicted 5' UTR has no apparent effect on the developmentally linked expression of a luciferase reporter cassette. Further, serial deletions reveal that whilst the absolute level of transcription is unaffected when up to 50% of the predicted 5' UTR is removed, the subsequent efficiency of translation is affected. These data provide key insights into the interplay of transcriptional and post-transcriptional mechanisms in the control of gene expression in this important human pathogen.
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Affiliation(s)
- Sandra Hasenkamp
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, United Kingdom
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Russell K, Hasenkamp S, Emes R, Horrocks P. Analysis of the spatial and temporal arrangement of transcripts over intergenic regions in the human malarial parasite Plasmodium falciparum. BMC Genomics 2013; 14:267. [PMID: 23601558 PMCID: PMC3681616 DOI: 10.1186/1471-2164-14-267] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 04/06/2013] [Indexed: 11/25/2022] Open
Abstract
Background The ability of the human malarial parasite Plasmodium falciparum to invade, colonise and multiply within diverse host environments, as well as to manifest its virulence within the human host, are activities tightly linked to the temporal and spatial control of gene expression. Yet, despite the wealth of high throughput transcriptomic data available for this organism there is very little information regarding the location of key transcriptional landmarks or their associated cis-acting regulatory elements. Here we provide a systematic exploration of the size and organisation of transcripts within intergenic regions to yield surrogate information regarding transcriptional landmarks, and to also explore the spatial and temporal organisation of transcripts over these poorly characterised genomic regions. Results Utilising the transcript data for a cohort of 105 genes we demonstrate that the untranscribed regions of mRNA are large and apportioned predominantly to the 5′ end of the open reading frame. Given the relatively compact size of the P. falciparum genome, we suggest that whilst transcriptional units are likely to spatially overlap, temporal co-transcription of adjacent transcriptional units is actually limited. Critically, the size of intergenic regions is directly dependent on the orientation of the two transcriptional units arrayed over them, an observation we extend to an analysis of the complete sequences of twelve additional organisms that share moderately compact genomes. Conclusions Our study provides a theoretical framework that extends our current understanding of the transcriptional landscape across the P. falciparum genome. Demonstration of a consensus gene-spacing rule that is shared between P. falciparum and ten other moderately compact genomes of apicomplexan parasites reveals the potential for our findings to have a wider impact across a phylum that contains many organisms important to human and veterinary health.
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Affiliation(s)
- Karen Russell
- Institute for Science and Technology in Medicine, Keele University, Huxley Building, Staffordshire ST5 5BG, United Kingdom
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Ecker A, Lewis RE, Ekland EH, Jayabalasingham B, Fidock DA. Tricks in Plasmodium's molecular repertoire--escaping 3'UTR excision-based conditional silencing of the chloroquine resistance transporter gene. Int J Parasitol 2012; 42:969-74. [PMID: 23023047 DOI: 10.1016/j.ijpara.2012.09.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2012] [Revised: 08/18/2012] [Accepted: 09/17/2012] [Indexed: 11/25/2022]
Abstract
In the human malaria parasite Plasmodium falciparum, the major determinant of chloroquine resistance, P. falciparum chloroquine resistance transporter (pfcrt), likely plays an essential role in asexual blood stages, thus precluding conventional gene targeting approaches. We attempted to conditionally silence the expression of its ortholog in Plasmodium berghei (pbcrt) through Flp recombinase-mediated excision of the 3'untranslated region (UTR) during mosquito passage. However, parasites maintained pbcrt expression despite 3'UTR excision. Characterisation of these pbcrt mRNAs, by 3'rapid amplification of cDNA ends, identified several replacement 3'UTR sequences. Our observations demonstrate the astounding genetic plasticity of this parasite when faced with the loss of an essential gene.
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Affiliation(s)
- Andrea Ecker
- Department of Microbiology and Immunology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
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Panneerselvam P, Bawankar P, Kulkarni S, Patankar S. In Silico Prediction of Evolutionarily Conserved GC-Rich Elements Associated with Antigenic Proteins of Plasmodium falciparum. Evol Bioinform Online 2011; 7:235-55. [PMID: 22375094 PMCID: PMC3283219 DOI: 10.4137/ebo.s8162] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
The Plasmodium falciparum genome being AT-rich, the presence of GC-rich regions suggests functional significance. Evolution imposes selection pressure to retain functionally important coding and regulatory elements. Hence searching for evolutionarily conserved GC-rich, intergenic regions in an AT-rich genome will help in discovering new coding regions and regulatory elements. We have used elevated GC content in intergenic regions coupled with sequence conservation against P. reichenowi, which is evolutionarily closely related to P. falciparum to identify potential sequences of functional importance. Interestingly, ~30% of the GC-rich, conserved sequences were associated with antigenic proteins encoded by var and rifin genes. The majority of sequences identified in the 5′ UTR of var genes are represented by short expressed sequence tags (ESTs) in cDNA libraries signifying that they are transcribed in the parasite. Additionally, 19 sequences were located in the 3′ UTR of rifins and 4 also have overlapping ESTs. Further analysis showed that several sequences associated with var genes have the capacity to encode small peptides. A previous report has shown that upstream peptides can regulate the expression of var genes hence we propose that these conserved GC-rich sequences may play roles in regulation of gene expression.
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Affiliation(s)
- Porkodi Panneerselvam
- Centre for Biotechnology, Anna University, Sardar Patel Road, Guindy, Chennai 600025, India
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Balu B, Chauhan C, Maher SP, Shoue DA, Kissinger JC, Fraser MJ, Adams JH. piggyBac is an effective tool for functional analysis of the Plasmodium falciparum genome. BMC Microbiol 2009; 9:83. [PMID: 19422698 PMCID: PMC2686711 DOI: 10.1186/1471-2180-9-83] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Accepted: 05/07/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Much of the Plasmodium falciparum genome encodes hypothetical proteins with limited homology to other organisms. A lack of robust tools for genetic manipulation of the parasite limits functional analysis of these hypothetical proteins and other aspects of the Plasmodium genome. Transposon mutagenesis has been used widely to identify gene functions in many organisms and would be extremely valuable for functional analysis of the Plasmodium genome. RESULTS In this study, we investigated the lepidopteran transposon, piggyBac, as a molecular genetic tool for functional characterization of the Plasmodium falciparum genome. Through multiple transfections, we generated 177 unique P. falciparum mutant clones with mostly single piggyBac insertions in their genomes. Analysis of piggyBac insertion sites revealed random insertions into the P. falciparum genome, in regards to gene expression in parasite life cycle stages and functional categories. We further explored the possibility of forward genetic studies in P. falciparum with a phenotypic screen for attenuated growth, which identified several parasite genes and pathways critical for intra-erythrocytic development. CONCLUSION Our results clearly demonstrate that piggyBac is a novel, indispensable tool for forward functional genomics in P. falciparum that will help better understand parasite biology and accelerate drug and vaccine development.
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Affiliation(s)
- Bharath Balu
- Department of Global Health, University of South Florida, Tampa, Florida 33612, USA.
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Horrocks P, Wong E, Russell K, Emes RD. Control of gene expression in Plasmodium falciparum - ten years on. Mol Biochem Parasitol 2008; 164:9-25. [PMID: 19110008 DOI: 10.1016/j.molbiopara.2008.11.010] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2008] [Revised: 11/25/2008] [Accepted: 11/26/2008] [Indexed: 01/24/2023]
Abstract
Ten years ago this journal published a review with an almost identical title detailing how the then recent introduction of transfection technology had advanced our understanding of the molecular control of transcriptional processes in Plasmodium falciparum, particularly in terms of promoter structure and function. In the succeeding years, sequencing of several Plasmodium spp. genomes and application of high throughput global postgenomic technologies have proven as significant, if not more, as has the ability to genetically manipulate these parasites in dissecting the molecular control of gene expression. Here we aim to review our current understanding of the control of gene expression in P. falciparum, including evidence available from other Plasmodium spp. and apicomplexan parasites. Specifically, however, we will address the current polarised debate regarding the level at which control is mediated, and attempt to identify some of the challenges this field faces in the next 10 years.
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Affiliation(s)
- Paul Horrocks
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, United Kingdom.
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Braks JAM, Mair GR, Franke-Fayard B, Janse CJ, Waters AP. A conserved U-rich RNA region implicated in regulation of translation in Plasmodium female gametocytes. Nucleic Acids Res 2007; 36:1176-86. [PMID: 18158300 PMCID: PMC2275103 DOI: 10.1093/nar/gkm1142] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Translational repression (TR) plays an important role in post-transcriptional regulation of gene expression and embryonic development in metazoans. TR also regulates the expression of a subset of the cytoplasmic mRNA population during development of fertilized female gametes of the unicellular malaria parasite, Plasmodium spp. which results in the formation of a polar and motile form, the ookinete. We report the conserved and sex-specific regulatory role of either the 3'- or 5'-UTR of a subset of translationally repressed mRNA species as shown by almost complete inhibition of expression of a GFP reporter protein in the female gametocyte. A U-rich, TR-associated element, identified previously in the 3'-UTR of TR-associated transcripts, played an essential role in mediating TR and a similar region could be found in the 5'-UTR shown in this study to be active in TR. The silencing effect of this 5'-UTR was shown to be independent of its position relative to its ORF, as transposition to a location 3' of the ORF did not affect TR. These results demonstrate for the first time in a unicellular organism that the 5' or the 3'-UTR of TR-associated transcripts play an important and conserved role in mediating TR in female gametocytes.
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Affiliation(s)
- Joanna A M Braks
- Department of Parasitology, Centre of Infectious Diseases, Leiden University Medical Centre (LUMC), Leiden, The Netherlands
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Lu F, Jiang H, Ding J, Mu J, Valenzuela JG, Ribeiro JMC, Su XZ. cDNA sequences reveal considerable gene prediction inaccuracy in the Plasmodium falciparum genome. BMC Genomics 2007; 8:255. [PMID: 17662120 PMCID: PMC1978503 DOI: 10.1186/1471-2164-8-255] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Accepted: 07/27/2007] [Indexed: 11/17/2022] Open
Abstract
Background The completion of the Plasmodium falciparum genome represents a milestone in malaria research. The genome sequence allows for the development of genome-wide approaches such as microarray and proteomics that will greatly facilitate our understanding of the parasite biology and accelerate new drug and vaccine development. Designing and application of these genome-wide assays, however, requires accurate information on gene prediction and genome annotation. Unfortunately, the genes in the parasite genome databases were mostly identified using computer software that could make some erroneous predictions. Results We aimed to obtain cDNA sequences to examine the accuracy of gene prediction in silico. We constructed cDNA libraries from mixed blood stages of P. falciparum parasite using the SMART cDNA library construction technique and generated 17332 high-quality expressed sequence tags (EST), including 2198 from primer-walking experiments. Assembly of our sequence tags produced 2548 contigs and 2671 singletons versus 5220 contigs and 5910 singletons when our EST were assembled with EST in public databases. Comparison of all the assembled EST/contigs with predicted CDS and genomic sequences in the PlasmoDB database identified 356 genes with predicted coding sequences fully covered by EST, including 85 genes (23.6%) with introns incorrectly predicted. Careful automatic software and manual alignments found an additional 308 genes that have introns different from those predicted, with 152 new introns discovered and 182 introns with sizes or locations different from those predicted. Alternative spliced and antisense transcripts were also detected. Matching cDNA to predicted genes also revealed silent chromosomal regions, mostly at subtelomere regions. Conclusion Our data indicated that approximately 24% of the genes in the current databases were predicted incorrectly, although some of these inaccuracies could represent alternatively spliced transcripts, and that more genes than currently predicted have one or more additional introns. It is therefore necessary to annotate the parasite genome with experimental data, although obtaining complete cDNA sequences from this parasite will be a formidable task due to the high AT nature of the genome. This study provides valuable information for genome annotation that will be critical for functional analyses.
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Affiliation(s)
- Fangli Lu
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
- Department of Parasitology, Zhongshan School of Medicine, Sun Yat‑sen University, Guangzhou, Guangdong 510080, PRoC
| | - Hongying Jiang
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Jinhui Ding
- Bioinformatics Unit, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, Maryland, USA
| | - Jianbing Mu
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Jesus G Valenzuela
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - José MC Ribeiro
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Xin-zhuan Su
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
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Oguariri RM, Dunn JM, Golightly LM. 3' gene regulatory elements required for expression of the Plasmodiumfalciparum developmental protein, Pfs25. Mol Biochem Parasitol 2006; 146:163-72. [PMID: 16439031 DOI: 10.1016/j.molbiopara.2005.12.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2005] [Revised: 07/21/2005] [Accepted: 12/09/2005] [Indexed: 11/29/2022]
Abstract
Development of sexual stage parasites within the mosquito vector is a crucial step in the transmission of Plasmodium parasites. The expression of the P25 and P28 proteins on the surface of Plasmodium parasites in the mosquito midgut is required for development and hence disease transmission. 3' gene-flanking sequences are essential for expression of these critical proteins but the nucleotide elements required are poorly defined. Transient gene transfection experiments using constructs containing deletions of the 3' gene-flanking region of the Plasmodium falciparum P25 homologue, pfs25, reveal that elements necessary for protein expression are within 315 nucleotides (nt) of the stop codon. A T-rich region 137-231 nt from the stop codon is required for expression. The nonamer AATAAAATG, 360 nt downstream from the stop codon, enhances expression by 51 percent. Using 3' RACE analysis, multiple polyadenylation sites from endogenous and plasmid-derived pfs25 transcripts were identified. Dissimilarities between the identified elements and those of metazoans support the hypothesis that definition of P25/28 3' gene regulatory processes may eventually permit the development of agents which block malaria transmission but are non-toxic to humans.
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Affiliation(s)
- Raphael M Oguariri
- Department of Medicine, Division of International Medicine and Infectious Diseases, Weill Medical College of Cornell University, New York, NY 10021, USA
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Neafsey DE, Hartl DL, Berriman M. Evolution of noncoding and silent coding sites in the Plasmodium falciparum and Plasmodium reichenowi genomes. Mol Biol Evol 2005; 22:1621-6. [PMID: 15858207 DOI: 10.1093/molbev/msi154] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We compared levels of sequence divergence between fourfold synonymous coding sites and noncoding sites from the intergenic and intronic regions of the Plasmodium falciparum and Plasmodium reichenowi genomes. We observed significant differences in the level of divergence between these classes of silent sites. Fourfold synonymous coding sites exhibited the highest level of sequence divergence, followed by introns, and then intergenic sequences. This pattern of relative divergence rates has been observed in primate genomes but was unexpected in Plasmodium due to a paucity of variation at silent sites in P. falciparum and the corollary hypothesis that silent sites in this genome may be subject to atypical selective constraints. Exclusion of hypermutable CpG dinucleotides reduces the divergence level of synonymous coding sites to that of intergenic sites but does not diminish the significantly higher divergence level of introns relative to intergenic sites. A greater than expected incidence of CpG dinucleotides in intergenic regions less than 500 bp from genes may indicate selective maintenance of regulatory motifs containing CpGs. Divergence rates of different classes of silent sites in these Plasmodium genomes are determined by a combination of mutational and selective pressures.
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Affiliation(s)
- Daniel E Neafsey
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA.
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Cann H, Brown SV, Oguariri RM, Golightly LM. 3' UTR signals necessary for expression of the Plasmodium gallinaceum ookinete protein, Pgs28, share similarities with those of yeast and plants. Mol Biochem Parasitol 2005; 137:239-45. [PMID: 15383294 DOI: 10.1016/j.molbiopara.2004.06.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2004] [Revised: 06/15/2004] [Accepted: 06/18/2004] [Indexed: 11/15/2022]
Abstract
During metazoan development, 3' UTR signals mediate the time and place of gene expression. For protozoan Plasmodium parasites, the formation of ookinetes from gametes in the mosquito midgut is an analogous developmental process. Previous studies of the 3' UTR signals necessary for expression of Pgs28, the major surface protein of Plasmodium gallinaceum ookinetes, suggested that a 3' UTR T-rich region and DNA sequences containing an ATTAAA eukaryotic polyadenylation consensus motif were necessary for its expression. During metazoan development, U-rich elements may function in conjunction with eukaryotic polyadenylation consensus signals to mediate developmental protein expression. To define whether the putative Plasmodium elements were mediators of Pgs28 expression mutations of these nucleotide sequences were made in plasmid constructs. The effect of the mutations on Pgs28 expression was tested by the transient gene transfection of sexual stage P. gallinaceum parasites. These studies reveal that two different mutations of the ATTAAA motif, which alter gene expression in higher eukaryotes and yeast, do not alter the expression of Pgs28. However, the U-rich element, adjacent nucleotides UUUACAAAAUUGUUUUAACU and downstream nucleotides UAUAUAAAA are able to mediate expression to varying degrees. The organization and overlapping function of these elements appears to more closely resemble that of yeasts or plants than those of metazoans.
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Affiliation(s)
- Helen Cann
- Department of Medicine, Division of International Medicine and Infectious Diseases, Weill Medical College of Cornell University, 1300 York Avenue, Room A421, New York, NY 10021, USA
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Le Roch KG, Johnson JR, Florens L, Zhou Y, Santrosyan A, Grainger M, Yan SF, Williamson KC, Holder AA, Carucci DJ, Yates JR, Winzeler EA. Global analysis of transcript and protein levels across the Plasmodium falciparum life cycle. Genome Res 2005; 14:2308-18. [PMID: 15520293 PMCID: PMC525690 DOI: 10.1101/gr.2523904] [Citation(s) in RCA: 374] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
To investigate the role of post-transcriptional controls in the regulation of protein expression for the malaria parasite, Plasmodium falciparum, we have compared mRNA transcript and protein abundance levels for seven different stages of the parasite life cycle. A moderately high positive relationship between mRNA and protein abundance was observed for these stages; the most common discrepancy was a delay between mRNA and protein accumulation. Potentially post-transcriptionally regulated genes are identified, and families of functionally related genes were observed to share similar patterns of mRNA and protein accumulation.
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Affiliation(s)
- Karine G Le Roch
- Department of Cell Biology ICND202, the Scripps Research Institute, La Jolla, California 92037, USA
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Shue P, Brown SV, Cann H, Singer EF, Appleby S, Golightly LM. The 3′ UTR elements of P. gallinaceum protein Pgs28 are functionally distinct from those of human cells. Mol Biochem Parasitol 2004; 137:355-9. [PMID: 15383307 DOI: 10.1016/j.molbiopara.2004.07.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2004] [Revised: 06/30/2004] [Accepted: 07/06/2004] [Indexed: 11/23/2022]
Affiliation(s)
- Peter Shue
- Department of Medicine, Division of International Medicine and Infectious Diseases, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA
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18
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Gunasekera AM, Patankar S, Schug J, Eisen G, Kissinger J, Roos D, Wirth DF. Widespread distribution of antisense transcripts in the Plasmodium falciparum genome. Mol Biochem Parasitol 2004; 136:35-42. [PMID: 15138065 DOI: 10.1016/j.molbiopara.2004.02.007] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2003] [Revised: 02/09/2004] [Accepted: 02/20/2004] [Indexed: 11/25/2022]
Abstract
The availability of the complete genome sequence of Plasmodium falciparum has facilitated high-throughput profiling of its complex life cycle, following the application of micro-array, proteomic, and serial analysis of gene expression (SAGE) technologies in this system. These, in turn, have yielded unprecedented insight into global gene expression, including the foremost demonstration of antisense transcription in the parasite. For example, owing to its inherent ability to sample novel ORFs and to predict transcript orientation, SAGE analysis in asexual forms led to the initial discovery of highly abundant antisense RNAs. To determine the extent of this phenomenon in P. falciparum, we have surveyed the distribution of both sense and antisense transcripts across the asexual transcriptome for the first time. To this end, a relational database integrating SAGE expression data with genome annotation information was constructed. This allowed the comprehensive annotation of a total of 17245 SAGE tags, extending over a 350-fold expression range. Transcripts from approximately 30% of the estimated 3D7 gene loci were present at detectable levels in mixed asexual stages, where loci involved in invasion and immune evasion; and carbohydrate metabolism were highly represented in the sense transcriptome. Approximately 12% of SAGE tags, however, were derived from the non-coding strand of nuclear-encoded ORFs, indicating that endogenous antisense RNAs are widespread in this system. Notably, these antisense transcripts were absent from the mitochondrial genome. Interestingly, we note that sense and antisense tag counts from single loci across the transcriptome were inversely related. Taken together, this data may provide first hints as to the possible function of antisense transcription in this system.
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Affiliation(s)
- Anusha Munasinghe Gunasekera
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Harvard University, 665 Huntington Avenue, Boston, MA 02115, USA
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Militello KT, Dodge M, Bethke L, Wirth DF. Identification of regulatory elements in the Plasmodium falciparum genome. Mol Biochem Parasitol 2004; 134:75-88. [PMID: 14747145 DOI: 10.1016/j.molbiopara.2003.11.004] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is little information regarding regulatory sequences in the newly sequenced genome of the malaria parasite, Plasmodium falciparum. Thus, for the first time, a bioinformatic strategy was utilized to identify regulatory elements in this genome using the P. falciparum heat shock protein (hsp) gene family as a model system. Our analysis indicates that the P. falciparum hsp genes do not contain standard eukaryotic regulatory elements. However, a novel G-rich regulatory element named the G-box was identified upstream of several P. falciparum hsp genes and the P. yoelii yoelii, P. berghei, and P. vivax hsp86 genes. Remarkably, the Plasmodium sp. G-boxes were required for maximal reporter gene expression in transient transfection assays. The G-box is not homologous to known eukaryotic elements, and is the best-defined functional element elucidated from Plasmodium sp. Our analysis also revealed several other elements necessary for reporter gene expression including an upstream sequence element, the region surrounding the transcription start site, and the 5' and 3' untranslated regions. These data demonstrate that unique regulatory elements are conserved in the genomes of Plasmodium sp., and demonstrate the feasibility of bioinformatic approaches for their identification.
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Affiliation(s)
- Kevin T Militello
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115, USA
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O'Connor RM, Kim K, Khan F, Ward HD. Expression of Cpgp40/15 in Toxoplasma gondii: a surrogate system for the study of Cryptosporidium glycoprotein antigens. Infect Immun 2003; 71:6027-34. [PMID: 14500524 PMCID: PMC201096 DOI: 10.1128/iai.71.10.6027-6034.2003] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cryptosporidium parvum is a waterborne enteric coccidian that causes diarrheal disease in a wide range of hosts. Development of successful therapies is hampered by the inability to culture the parasite and the lack of a transfection system for genetic manipulation. The glycoprotein products of the Cpgp40/15 gene, gp40 and gp15, are involved in C. parvum sporozoite attachment to and invasion of host cells and, as such, may be good targets for anticryptosporidial therapies. However, the function of these antigens appears to be dependent on the presence of multiple O-linked alpha-N-acetylgalactosamine (alpha-GalNAc) determinants. A eukaryotic expression system that would produce proteins bearing glycosylation patterns similar to those found on the native C. parvum glycoproteins would greatly facilitate the molecular and functional characterization of these antigens. As a unique approach to this problem, the Cpgp40/15 gene was transiently expressed in Toxoplasma gondii, and the expressed recombinant glycoproteins were characterized. Antisera to gp40 and gp15 reacted with the surface membranes of tachyzoites expressing the Cpgp40/15 construct, and this reactivity colocalized with that of antiserum to the T. gondii surface protein SAG1. Surface membrane localization was dependent on the presence of the glycophosphatidylinositol anchor attachment site present in the gp15 coding sequence. The presence of terminal O-linked alpha-GalNAc determinants on the T. gondii recombinant gp40 was confirmed by reactivity with Helix pomatia lectin and the monoclonal antibody 4E9, which recognizes alpha-GalNAc residues, and digestion with alpha-N-acetylgalactosaminidase. In addition to appropriate localization and glycosylation, T. gondii apparently processes the gp40/15 precursor into the gp40 and gp15 component glycopolypeptides, albeit inefficiently. These results suggest that a surrogate system using T. gondii for the study of Cryptosporidium biology may be useful.
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Affiliation(s)
- R M O'Connor
- Division of Geographic Medicine and Infectious Diseases, Tufts-New England Medical Center, 50 Washington Street, Boston, MA 02111, USA.
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Chow CS, Wirth DF. Linker scanning mutagenesis of the Plasmodium gallinaceum sexual stage specific gene pgs28 reveals a novel downstream cis-control element. Mol Biochem Parasitol 2003; 129:199-208. [PMID: 12850264 DOI: 10.1016/s0166-6851(03)00101-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Protozoan parasites undergo complex life cycles that depend on regulated gene expression. However, limited studies on gene regulation in these parasites have repeatedly shown characteristics different from other eukaryotes. Within the Apicomplexa family, little is known about the mechanism of gene expression and regulation in Plasmodium spp. We have been investigating the cis-elements that control basal expression of a sexual stage specific gene in Plasmodium gallinaceum. Previously, we identified by 5' deletion analysis of a reporter construct that the 333bp upstream of the translational start site of pgs28 is sufficient for basal expression, and that the sequence between -333 and 316bp is necessary for such expression. In this report, we identified by linker scanning mutagenesis an 8-bp sequence that is essential for pgs28 transgene expression. This sequence is a target of sequence-specific nuclear factors. Primer extension studies demonstrate that, interestingly, the endogenous pgs28 transcript has two 5' ends, at -65 and +1. We suggest that this 8-bp sequence, CAGACAGC that is situated at +24 to +31 (with respect to the proximal start site), is a novel downstream promoter element in P. gallinaceum that appears to function independently of a TATA box or an Inr element.
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Affiliation(s)
- Connie S Chow
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
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Florin-Christensen M, Suarez CE, Hines SA, Palmer GH, Brown WC, McElwain TF. The Babesia bovis merozoite surface antigen 2 locus contains four tandemly arranged and expressed genes encoding immunologically distinct proteins. Infect Immun 2002; 70:3566-75. [PMID: 12065497 PMCID: PMC128111 DOI: 10.1128/iai.70.7.3566-3575.2002] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Members of the variable merozoite surface antigen (vmsa) gene family of Babesia bovis encode membrane proteins involved in erythrocyte invasion. In this study, we have identified and sequenced the complete 8.3-kb genomic locus containing msa-2, a member of the vmsa family, in the biologically cloned Mexico Mo7 strain. Four tandemly arranged copies of msa-2-related genes were found in the locus. The four genes, designated msa-2a(1) (which corresponds to the originally described msa-2 gene), msa-2a(2), msa-2b, and msa-2c, were shown to be transcribed and expressed and encode proteins with open reading frames ranging in size from 266 (MSA-2c) to 317 (MSA-2a(1)) amino acids. MSA-2a(1) and -2a(2) are the most closely related of the four proteins (90% identity), differing by (i) the number of 24-amino-acid repeats that comprise a surface-exposed B-cell epitope and (ii) the presence of a 32-amino-acid area of recombination between MSA-2a(2) and -2b. In contrast, msa-2c is most closely related to the previously described babr 0.8 gene in Australia strains of B. bovis. Comparison of MSA-2 proteins in the Argentina R1A strain of B. bovis with the Mexico Mo7 clone revealed a relatively high degree of conservation (83.6, 69.4, 79.1, and 88.7% amino acid identity for MSA-2a(1), -2a(2), -2b, and -2c, respectively), in contrast to the extensive MSA-1 sequence variation (52% identity) between the same two strains. Postinfection bovine immune serum contains antibodies that bound to each of the recombinant MSA-2 proteins. Blocking assays demonstrated the presence of unique B-cell epitopes in MSA-2a(1), -2b, and -2c. The results support the evolution of the msa-2 locus through at least two gene duplications, with selection for multiple related but antigenically distinct merozoite surface proteins.
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Affiliation(s)
- Monica Florin-Christensen
- Program in Vector-Borne Diseases, Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington 99164-7040, USA
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O'Connor RM, Thorpe CM, Cevallos AM, Ward HD. Expression of the highly polymorphic Cryptosporidium parvum Cpgp40/15 gene in genotype I and II isolates. Mol Biochem Parasitol 2002; 119:203-15. [PMID: 11814572 DOI: 10.1016/s0166-6851(01)00416-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The enteric protozoan Cryptosporidium parvum infects intestinal epithelial cells in a wide range of hosts, causing severe gastrointestinal disease. The invasive sporozoite stage most likely attaches to and invades host cells through multiple host receptor/parasite ligand interactions. Preliminary evidence suggests that the glycoprotein products of the Cpgp40/15 gene, gp40 and gp15, are involved in these interactions. In addition, the Cpgp40/15 gene that encodes these glycopeptides is highly polymorphic in genotype I isolates, suggesting that the gene products may be subject to immune selection. In this study, we characterized the Cpgp40/15 gene in a genotype I isolate and compared expression of the Cpgp40/15 gene in isolates of both genotype. Cpgp40/15 is a single copy gene in both TU502 (genotype I) and GCH1 (genotype II) isolates. However, Northern blot analysis revealed the presence of two transcripts, 2.3 and 1.5 kb in size, in mRNA from GCH1 as well as TU502-infected Caco-2A cells. Accumulation of the two Cpgp40/15 mRNAs peaked 12-24 h post-infection. Using 3'RACE analysis, three polyadenylation sites were identified 371, 978 and 1002 bp downstream of the GCH1 Cpgp40/15 stop codon. Two of these polyadenylation sites were also used in TU502. The sequences of the GCH1 Cpgp40/15 3'untranslated regions (3'UTRs) were identical to genomic sequence and shared 96.7% homology with TU502 3'UTRs. Actinomycin D treatment of GCH1-infected Caco-2A cells followed by Northern blot analysis, revealed that the stability of the 1.5 kb message was considerably greater than that of the 2.3 kb transcript.
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Affiliation(s)
- Roberta M O'Connor
- Division of Geographic Medicine and Infectious Diseases, New England Medical Center, Tufts University School of Medicine, Box 041, 750 Washington Street, Boston, MA 02111, USA.
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D'Orso I, Frasch AC. TcUBP-1, a developmentally regulated U-rich RNA-binding protein involved in selective mRNA destabilization in trypanosomes. J Biol Chem 2001; 276:34801-9. [PMID: 11435421 DOI: 10.1074/jbc.m102120200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Developmental stages of the trypanosome life cycle differ in their morphology, biology, and biochemical properties. Consequently, several proteins have to be tightly regulated in their expression to allow trypanosomes to adapt rapidly to sudden environmental changes, a process that might be of central importance for parasite survival. However, in contrast to higher eukaryotic cells, trypanosomes do not seem to regulate gene expression through regulation of transcription initiation. These parasites make use of post-transcriptional regulatory mechanisms and modification of mRNA half-life is a relevant one. Trans-acting factors binding to cis-elements that affect mRNA stability of mature transcripts have not been identified in these cells. In this work, a novel U-rich RNA-binding protein (TcUBP-1) from Trypanosoma cruzi, the agent of Chagas disease, was identified. Its structure includes an RNA recognition motif, a nuclear export signal, and auxiliary domains with glycine- and glutamine-rich regions. TcUBP-1 recognizes the 44-nucleotide AU-rich RNA instability element located in the 3'-untranslated region of mucin SMUG mRNAs (Di Noia, J. M., D'Orso, I., Sanchez, D. O., and Frasch, A. C. (2000) J. Biol. Chem. 275, 10218-10227) as well as GU-rich sequences. Over-expression of TcUBP-1 in trypanosomes decreases the half-life of SMUG mucin mRNAs in vivo but does not affect the stability of other parasite mRNAs. Because TcUBP-1 is developmentally regulated, it might have a relevant role in regulating protein expression during trypanosome differentiation, allowing a correct expression pattern of U-rich-containing mRNAs.
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Affiliation(s)
- I D'Orso
- Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús, Consejo Nacional de Investigaciones Cientificas y Técnicas, Universidad Nacional de General San Martin, 1650 San Martin, Provincia de Buenos Aires, Argentina
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Mbacham WF, Chow CS, Daily J, Golightly LM, Wirth DF. Deletion analysis of the 5' flanking sequence of the Plasmodium gallinaceum sexual stage specific gene pgs28 suggests a bipartite arrangement of cis-control elements. Mol Biochem Parasitol 2001; 113:183-7. [PMID: 11254967 DOI: 10.1016/s0166-6851(01)00210-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- W F Mbacham
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
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Patankar S, Fujioka H, Wirth DF. The signal sequence and C-terminal hydrophobic domain are required for localization of the sexual stage antigen pgs28 to the surface of P. gallinaceum ookinetes. Mol Biochem Parasitol 2000; 111:425-35. [PMID: 11163448 DOI: 10.1016/s0166-6851(00)00340-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Pgs28 protein is a major surface antigen of the sexual stages of Plasmodium gallinaceum the zygotes and the ookinetes. The protein contains conserved motifs, namely an N-terminal signal sequence, four epidermal growth factor-like repeats and a C-terminal hydrophobic domain that serves as a signal for glycosylphosphatidylinositol (GPI)--anchor modification. In this study, we define the protein motifs required for the surface localization of Pgs28 in ookinetes. using transient transfection combined with immunofluorescence and confocal microscopy. Pgs28 fused to the green fluorescent protein (Pgs28-GFP) is expressed in zygotes, intermediate retort forms and ookinetes. Mutational analyses of Pgs28 coding regions reveal that deletions of the signal sequence and the C-terminal domain result in intracellular retention of the fusion protein. Therefore, the signal sequence and C-terminal domain are required for cell surface localization. Additionally, the Pgs28-GFP fusion proteins are shed from the surface of live ookinetes, suggesting that Pgs28 may be involved in interactions with the cells of the mosquito midgut or during motility.
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Affiliation(s)
- S Patankar
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115, USA
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