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Sookpongthai P, Utayopas K, Sitthiyotha T, Pengsakul T, Kaewthamasorn M, Wangkanont K, Harnyuttanakorn P, Chunsrivirot S, Pattaradilokrat S. Global diversity of the gene encoding the Pfs25 protein-a Plasmodium falciparum transmission-blocking vaccine candidate. Parasit Vectors 2021; 14:571. [PMID: 34749796 PMCID: PMC8574928 DOI: 10.1186/s13071-021-05078-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 10/21/2021] [Indexed: 11/29/2022] Open
Abstract
Background Vaccines against the sexual stages of the malarial parasite Plasmodium falciparum are indispensable for controlling malaria and abrogating the spread of drug-resistant parasites. Pfs25, a surface antigen of the sexual stage of P. falciparum, is a leading candidate for transmission-blocking vaccine development. While clinical trials have reported that Pfs25-based vaccines are safe and effective in inducing transmission-blocking antibodies, the extent of the genetic diversity of Pfs25 in malaria endemic populations has rarely been studied. Thus, this study aimed to investigate the global diversity of Pfs25 in P. falciparum populations. Methods A database of 307 Pfs25 sequences of P. falciparum was established. Population genetic analyses were performed to evaluate haplotype and nucleotide diversity, analyze haplotypic distribution patterns of Pfs25 in different geographical populations, and construct a haplotype network. Neutrality tests were conducted to determine evidence of natural selection. Homology models of the Pfs25 haplotypes were constructed, subjected to molecular dynamics (MD), and analyzed in terms of flexibility and percentages of secondary structures. Results The Pfs25 gene of P. falciparum was found to have 11 unique haplotypes. Of these, haplotype 1 (H1) and H2, the major haplotypes, represented 70% and 22% of the population, respectively, and were dominant in Asia, whereas only H1 was dominant in Africa, Central America, and South America. Other haplotypes were rare and region-specific, resulting in unique distribution patterns in different geographical populations. The diversity in Pfs25 originated from ten single-nucleotide polymorphism (SNP) loci located in the epidermal growth factor (EGF)-like domains and anchor domain. Of these, an SNP at position 392 (GGA/GCA), resulting in amino acid substitution 131 (Gly/Ala), defined the two major haplotypes. The MD results showed that the structures of H1 and H2 variants were relatively similar. Limited polymorphism in Pfs25 could likely be due to negative selection. Conclusions The study successfully established a Pfs25 sequence database that can become an essential tool for monitoring vaccine efficacy, designing assays for detecting malaria carriers, and conducting epidemiological studies of P. falciparum. The discovery of the two major haplotypes, H1 and H2, and their conserved structures suggests that the current Pfs25-based vaccines could be used globally for malaria control. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-021-05078-6.
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Affiliation(s)
- Pornpawee Sookpongthai
- M.Sc. program in Zoology, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Korawich Utayopas
- Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Thassanai Sitthiyotha
- Structural and Computational Biology Research Unit, Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Theerakamol Pengsakul
- Faculty of Medical Technology, Prince of Songkla University, Hat Yai, Songkhla, 90110, Thailand
| | - Morakot Kaewthamasorn
- Veterinary Parasitology Research Unit, Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Kittikhun Wangkanont
- Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | | | - Surasak Chunsrivirot
- Structural and Computational Biology Research Unit, Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand.,Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
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Jing Q, Cao L, Zhang L, Cheng X, Gilbert N, Dai X, Sun M, Liang S, Jiang L. Plasmodium falciparum var Gene Is Activated by Its Antisense Long Noncoding RNA. Front Microbiol 2018; 9:3117. [PMID: 30619191 PMCID: PMC6305453 DOI: 10.3389/fmicb.2018.03117] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 12/03/2018] [Indexed: 12/21/2022] Open
Abstract
Plasmodium falciparum erythrocyte membrane protein 1, encoded by var gene, is an immunodominant antigen mediating immune evasion in humans. At a given time, only a single var gene is commonly expressed in one parasite. However, the regulation mechanism of var transcription remains largely unknown. In this study, we identified the antisense long non-coding RNA (aslncRNA) derived from var intron as an activation factor for the corresponding var gene. The exogenous artificial var aslncRNA transcribed by T7 RNA polymerase from episome can specifically activate the homologous var gene, and the exogenous aslncRNA activates transcription of both var mRNA and endogenous aslncRNA in a manner independent of the conserved intron sequence within the var gene family. Interestingly, the newly activated var gene and the previously dominant var gene then could be co-expressed in the same parasite nuclei, which suggests that the aslncRNA-mediated var gene activation could escape from the control of mutually exclusively expression of the var gene family. Together, our work shows that var aslncRNA is the activator responsible for var gene transcriptional regulation.
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Affiliation(s)
- Qingqing Jing
- Unit of Human Parasite Molecular and Cell Biology, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Long Cao
- Unit of Human Parasite Molecular and Cell Biology, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China
| | - Liangliang Zhang
- Clinical Laboratory Medicine, Changzhi People's Hospital, Changzhi, China.,Department of Parasitology, School of Basic Medical Science, Wenzhou Medical University, Wenzhou, China
| | - Xiu Cheng
- Unit of Human Parasite Molecular and Cell Biology, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Nicolas Gilbert
- Unit of Human Parasite Molecular and Cell Biology, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,Institut de Médecine Régénératrice et de Biothérapie, INSERM U1183, CHU Montpellier, Montpellier, France
| | - Xueyu Dai
- Unit of Human Parasite Molecular and Cell Biology, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Maoxin Sun
- Unit of Human Parasite Molecular and Cell Biology, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,ShanghaiTech University, Shanghai, China
| | - Shaohui Liang
- Department of Parasitology, School of Basic Medical Science, Wenzhou Medical University, Wenzhou, China
| | - Lubin Jiang
- Unit of Human Parasite Molecular and Cell Biology, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China.,ShanghaiTech University, Shanghai, China
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Painter HJ, Carrasquilla M, Llinás M. Capturing in vivo RNA transcriptional dynamics from the malaria parasite Plasmodium falciparum. Genome Res 2017; 27:1074-1086. [PMID: 28416533 PMCID: PMC5453321 DOI: 10.1101/gr.217356.116] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 03/22/2017] [Indexed: 12/30/2022]
Abstract
To capture the transcriptional dynamics within proliferating cells, methods to differentiate nascent transcription from preexisting mRNAs are desired. One approach is to label newly synthesized mRNA transcripts in vivo through the incorporation of modified pyrimidines. However, the human malaria parasite, Plasmodium falciparum, is incapable of pyrimidine salvage for mRNA biogenesis. To capture cellular mRNA dynamics during Plasmodium development, we engineered parasites that can salvage pyrimidines through the expression of a single bifunctional yeast fusion gene, cytosine deaminase/uracil phosphoribosyltransferase (FCU). We show that expression of FCU allows for the direct incorporation of thiol-modified pyrimidines into nascent mRNAs. Using developmental stage-specific promoters to express FCU-GFP enables the biosynthetic capture and in-depth analysis of mRNA dynamics from subpopulations of cells undergoing differentiation. We demonstrate the utility of this method by examining the transcriptional dynamics of the sexual gametocyte stage transition, a process that is essential to malaria transmission between hosts. Using the pfs16 gametocyte-specific promoter to express FCU-GFP in 3D7 parasites, we found that sexual stage commitment is governed by transcriptional reprogramming and stabilization of a subset of essential gametocyte transcripts. We also measured mRNA dynamics in F12 gametocyte-deficient parasites and demonstrate that the transcriptional program required for sexual commitment and maturation is initiated but likely aborted due to the absence of the PfAP2-G transcriptional regulator and a lack of gametocyte-specific mRNA stabilization. Biosynthetic labeling of Plasmodium mRNAs is incredibly versatile, can be used to measure transcriptional dynamics at any stage of parasite development, and will allow for future applications to comprehensively measure RNA-protein interactions in the malaria parasite.
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Affiliation(s)
- Heather J Painter
- Department of Biochemistry and Molecular Biology and Huck Center for Malaria Research, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Manuela Carrasquilla
- Department of Biochemistry and Molecular Biology and Huck Center for Malaria Research, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Manuel Llinás
- Department of Biochemistry and Molecular Biology and Huck Center for Malaria Research, Pennsylvania State University, University Park, Pennsylvania 16802, USA.,Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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A semi-automated luminescence based standard membrane feeding assay identifies novel small molecules that inhibit transmission of malaria parasites by mosquitoes. Sci Rep 2015; 5:18704. [PMID: 26687564 PMCID: PMC4685452 DOI: 10.1038/srep18704] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 11/24/2015] [Indexed: 12/27/2022] Open
Abstract
Current first-line treatments for uncomplicated falciparum malaria rapidly clear the asexual stages of the parasite, but do not fully prevent parasite transmission by mosquitoes. The standard membrane feeding assay (SMFA) is the biological gold standard assessment of transmission reducing activity (TRA), but its throughput is limited by the need to determine mosquito infection status by dissection and microscopy. Here we present a novel dissection-free luminescence based SMFA format using a transgenic Plasmodium falciparum reporter parasite without resistance to known antimalarials and therefore unrestricted in its utility in compound screening. Analyses of sixty-five compounds from the Medicines for Malaria Venture validation and malaria boxes identified 37 compounds with high levels of TRA (>80%); different assay modes allowed discrimination between gametocytocidal and downstream modes of action. Comparison of SMFA data to published assay formats for predicting parasite infectivity indicated that individual in vitro screens show substantial numbers of false negatives. These results highlight the importance of the SMFA in the screening pipeline for transmission reducing compounds and present a rapid and objective method. In addition we present sixteen diverse chemical scaffolds from the malaria box that may serve as a starting point for further discovery and development of malaria transmission blocking drugs.
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De Niz M, Helm S, Horstmann S, Annoura T, del Portillo HA, Khan SM, Heussler VT. In vivo and in vitro characterization of a Plasmodium liver stage-specific promoter. PLoS One 2015; 10:e0123473. [PMID: 25874388 PMCID: PMC4398466 DOI: 10.1371/journal.pone.0123473] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 03/03/2015] [Indexed: 12/28/2022] Open
Abstract
Little is known about stage-specific gene regulation in Plasmodium parasites, in particular the liver stage of development. We have previously described in the Plasmodium berghei rodent model, a liver stage-specific (lisp2) gene promoter region, in vitro. Using a dual luminescence system, we now confirm the stage specificity of this promoter region also in vivo. Furthermore, by substitution and deletion analyses we have extended our in vitro characterization of important elements within the promoter region. Importantly, the dual luminescence system allows analyzing promoter constructs avoiding mouse-consuming cloning procedures of transgenic parasites. This makes extensive mutation and deletion studies a reasonable approach also in the malaria mouse model. Stage-specific expression constructs and parasite lines are extremely valuable tools for research on Plasmodium liver stage biology. Such reporter lines offer a promising opportunity for assessment of liver stage drugs, characterization of genetically attenuated parasites and liver stage-specific vaccines both in vivo and in vitro, and may be key for the generation of inducible systems.
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Affiliation(s)
- Mariana De Niz
- Institute of Cell Biology, University of Bern, Bern, Switzerland
- * E-mail:
| | - Susanne Helm
- Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Sebastian Horstmann
- Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - Takeshi Annoura
- Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
- Department of Parasitology, National Institute of Infectious Diseases (NIID), Tokyo, Japan
| | - Hernando A. del Portillo
- Barcelona Centre for International Health Research (CRESIB), Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain
| | - Shahid M. Khan
- Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
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6
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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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Feagin JE, Harrell MI, Lee JC, Coe KJ, Sands BH, Cannone JJ, Tami G, Schnare MN, Gutell RR. The fragmented mitochondrial ribosomal RNAs of Plasmodium falciparum. PLoS One 2012; 7:e38320. [PMID: 22761677 PMCID: PMC3382252 DOI: 10.1371/journal.pone.0038320] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 05/03/2012] [Indexed: 11/18/2022] Open
Abstract
Background The mitochondrial genome in the human malaria parasite Plasmodium falciparum is most unusual. Over half the genome is composed of the genes for three classic mitochondrial proteins: cytochrome oxidase subunits I and III and apocytochrome b. The remainder encodes numerous small RNAs, ranging in size from 23 to 190 nt. Previous analysis revealed that some of these transcripts have significant sequence identity with highly conserved regions of large and small subunit rRNAs, and can form the expected secondary structures. However, these rRNA fragments are not encoded in linear order; instead, they are intermixed with one another and the protein coding genes, and are coded on both strands of the genome. This unorthodox arrangement hindered the identification of transcripts corresponding to other regions of rRNA that are highly conserved and/or are known to participate directly in protein synthesis. Principal Findings The identification of 14 additional small mitochondrial transcripts from P. falcipaurm and the assignment of 27 small RNAs (12 SSU RNAs totaling 804 nt, 15 LSU RNAs totaling 1233 nt) to specific regions of rRNA are supported by multiple lines of evidence. The regions now represented are highly similar to those of the small but contiguous mitochondrial rRNAs of Caenorhabditis elegans. The P. falciparum rRNA fragments cluster on the interfaces of the two ribosomal subunits in the three-dimensional structure of the ribosome. Significance All of the rRNA fragments are now presumed to have been identified with experimental methods, and nearly all of these have been mapped onto the SSU and LSU rRNAs. Conversely, all regions of the rRNAs that are known to be directly associated with protein synthesis have been identified in the P. falciparum mitochondrial genome and RNA transcripts. The fragmentation of the rRNA in the P. falciparum mitochondrion is the most extreme example of any rRNA fragmentation discovered.
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Affiliation(s)
- Jean E Feagin
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America.
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Gregory JA, Li F, Tomosada LM, Cox CJ, Topol AB, Vinetz JM, Mayfield S. Algae-produced Pfs25 elicits antibodies that inhibit malaria transmission. PLoS One 2012; 7:e37179. [PMID: 22615931 PMCID: PMC3353897 DOI: 10.1371/journal.pone.0037179] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Accepted: 04/17/2012] [Indexed: 12/21/2022] Open
Abstract
Subunit vaccines are significantly more expensive to produce than traditional vaccines because they are based primarily on recombinant proteins that must be purified from the expression system. Despite the increased cost, subunit vaccines are being developed because they are safe, effective, and can elicit antibodies that confer protection against diseases that are not currently vaccine-preventable. Algae are an attractive platform for producing subunit vaccines because they are relatively inexpensive to grow, genetically tractable, easily scaled to large volumes, have a short generation time, and are devoid of inflammatory, viral, or prion contaminants often present in other systems. We tested whether algal chloroplasts can produce malaria transmission blocking vaccine candidates, Plasmodium falciparum surface protein 25 (Pfs25) and 28 (Pfs28). Antibodies that recognize Pfs25 and Pfs28 disrupt the sexual development of parasites within the mosquito midgut, thus preventing transmission of malaria from one human host to the next. These proteins have been difficult to produce in traditional recombinant systems because they contain tandem repeats of structurally complex epidermal growth factor-like domains, which cannot be produced in bacterial systems, and because they are not glycosylated, so they must be modified for production in eukaryotic systems. Production in algal chloroplasts avoids these issues because chloroplasts can fold complex eukaryotic proteins and do not glycosylate proteins. Here we demonstrate that algae are the first recombinant system to successfully produce an unmodified and aglycosylated version of Pfs25 or Pfs28. These antigens are structurally similar to the native proteins and antibodies raised to these recombinant proteins recognize Pfs25 and Pfs28 from P. falciparum. Furthermore, antibodies to algae-produced Pfs25 bind the surface of in-vitro cultured P. falciparum sexual stage parasites and exhibit transmission blocking activity. Thus, algae are promising organisms for producing cysteine-disulfide-containing malaria transmission blocking vaccine candidate proteins.
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Affiliation(s)
- James A. Gregory
- Division of Biological Sciences, and the San Diego Center for Algae Biotechnology, University of California San Diego, California, United States of America
| | - Fengwu Li
- Division of Infectious Disease, Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Lauren M. Tomosada
- Division of Biological Sciences, and the San Diego Center for Algae Biotechnology, University of California San Diego, California, United States of America
| | - Chesa J. Cox
- Division of Biological Sciences, and the San Diego Center for Algae Biotechnology, University of California San Diego, California, United States of America
| | - Aaron B. Topol
- Division of Biological Sciences, and the San Diego Center for Algae Biotechnology, University of California San Diego, California, United States of America
| | - Joseph M. Vinetz
- Division of Infectious Disease, Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Stephen Mayfield
- Division of Biological Sciences, and the San Diego Center for Algae Biotechnology, University of California San Diego, California, United States of America
- * E-mail:
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9
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Fisher N, Abd Majid R, Antoine T, Al-Helal M, Warman AJ, Johnson DJ, Lawrenson AS, Ranson H, O'Neill PM, Ward SA, Biagini GA. Cytochrome b mutation Y268S conferring atovaquone resistance phenotype in malaria parasite results in reduced parasite bc1 catalytic turnover and protein expression. J Biol Chem 2012; 287:9731-9741. [PMID: 22282497 PMCID: PMC3322985 DOI: 10.1074/jbc.m111.324319] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 01/26/2012] [Indexed: 11/24/2022] Open
Abstract
Atovaquone is an anti-malarial drug used in combination with proguanil (e.g. Malarone(TM)) for the curative and prophylactic treatment of malaria. Atovaquone, a 2-hydroxynaphthoquinone, is a competitive inhibitor of the quinol oxidation (Q(o)) site of the mitochondrial cytochrome bc(1) complex. Inhibition of this enzyme results in the collapse of the mitochondrial membrane potential, disruption of pyrimidine biosynthesis, and subsequent parasite death. Resistance to atovaquone in the field is associated with point mutations in the Q(o) pocket of cytochrome b, most notably near the conserved Pro(260)-Glu(261)-Trp(262)-Tyr(263) (PEWY) region in the ef loop). The effect of this mutation has been extensively studied in model organisms but hitherto not in the parasite itself. Here, we have performed a molecular and biochemical characterization of an atovaquone-resistant field isolate, TM902CB. Molecular analysis of this strain reveals the presence of the Y268S mutation in cytochrome b. The Y268S mutation is shown to confer a 270-fold shift of the inhibitory constant (K(i)) for atovaquone with a concomitant reduction in the V(max) of the bc(1) complex of ∼40% and a 3-fold increase in the observed K(m) for decylubiquinol. Western blotting analyses reveal a reduced iron-sulfur protein content in Y268S bc(1) suggestive of a weakened interaction between this subunit and cytochrome b. Gene expression analysis of the TM902CB strain reveals higher levels of expression, compared with the 3D7 (atovaquone-sensitive) control strain in bc(1) and cytochrome c oxidase genes. It is hypothesized that the observed differential expression of these and other key genes offsets the fitness cost resulting from reduced bc(1) activity.
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Affiliation(s)
- Nicholas Fisher
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - Roslaini Abd Majid
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - Thomas Antoine
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - Mohammed Al-Helal
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - Ashley J Warman
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - David J Johnson
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | | | - Hilary Ranson
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and
| | - Paul M O'Neill
- Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, United Kingdom
| | - Stephen A Ward
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and.
| | - Giancarlo A Biagini
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom and.
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Liu Z, Miao J, Cui L. Gametocytogenesis in malaria parasite: commitment, development and regulation. Future Microbiol 2012; 6:1351-69. [PMID: 22082293 DOI: 10.2217/fmb.11.108] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Malaria parasites have evolved a complicated life cycle alternating between two hosts. Gametocytes are produced in the vertebrate hosts and are obligatory for natural transmission of the parasites through mosquito vectors. The mechanism of sexual development in Plasmodium has been the focus of extensive studies. In the postgenomic era, the advent of genome-wide analytical tools and genetic manipulation technology has enabled rapid advancement of our knowledge in this area. Patterns of gene expression during sexual development, molecular distinction of the two sexes, and mechanisms underlying subsequent formation of gametes and their fertilization have been progressively elucidated. However, the triggers and mechanism of sexual development remain largely unknown. This article provides an update of our understanding of the molecular and cellular events associated with the decision for commitment to sexual development and regulation of gene expression during gametocytogenesis. Insights into the molecular mechanisms of gametocyte development are essential for designing proper control strategies for interruption of malaria transmission and ultimate elimination.
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Affiliation(s)
- Zhenyu Liu
- Department of Entomology, The Pennsylvania State University, 537 ASI Building University Park, PA 16802, USA
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11
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Wong EH, Hasenkamp S, Horrocks P. Analysis of the molecular mechanisms governing the stage-specific expression of a prototypical housekeeping gene during intraerythrocytic development of P. falciparum. J Mol Biol 2011; 408:205-21. [PMID: 21354176 PMCID: PMC3081073 DOI: 10.1016/j.jmb.2011.02.043] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Revised: 02/10/2011] [Accepted: 02/17/2011] [Indexed: 01/22/2023]
Abstract
Gene expression during the intraerythrocytic development cycle of the human malarial parasite Plasmodium falciparum is subject to tight temporal control, resulting in a cascade of gene expression to meet the physiological demands of growth, replication, and reinvasion. The roles of the different molecular mechanisms that drive this temporal program of gene expression are poorly understood. Here we report the use of the bxb1 integrase system to reconstitute all aspects of the absolute and temporal control of the prototypical housekeeping gene encoding the proliferating cell nuclear antigen (Pfpcna) around an integrated luciferase reporter cassette. A quantitative analysis of the effect of the serial deletion of 5′ and 3′ genetic elements and sublethal doses of histone deacetylase inhibitors demonstrates that while the absolute control of gene expression could be perturbed, no effect on the temporal control of gene expression was observed. These data provide support for a novel model for the temporal control of potentially hundreds of genes during the intraerythrocytic development of this important human pathogen.
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Affiliation(s)
- Eleanor H. Wong
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, UK
- School of Medicine, Keele University, Staffordshire ST5 5BG, UK
| | - Sandra Hasenkamp
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, UK
| | - Paul Horrocks
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, UK
- School of Medicine, Keele University, Staffordshire ST5 5BG, UK
- Corresponding author. Institute for Science and Technology in Medicine, Keele University, Huxley Building, Staffordshire ST5 5BG, UK.
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Campbell TL, De Silva EK, Olszewski KL, Elemento O, Llinás M. Identification and genome-wide prediction of DNA binding specificities for the ApiAP2 family of regulators from the malaria parasite. PLoS Pathog 2010; 6:e1001165. [PMID: 21060817 PMCID: PMC2965767 DOI: 10.1371/journal.ppat.1001165] [Citation(s) in RCA: 182] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 09/27/2010] [Indexed: 11/18/2022] Open
Abstract
The molecular mechanisms underlying transcriptional regulation in apicomplexan parasites remain poorly understood. Recently, the Apicomplexan AP2 (ApiAP2) family of DNA binding proteins was identified as a major class of transcriptional regulators that are found across all Apicomplexa. To gain insight into the regulatory role of these proteins in the malaria parasite, we have comprehensively surveyed the DNA-binding specificities of all 27 members of the ApiAP2 protein family from Plasmodium falciparum revealing unique binding preferences for the majority of these DNA binding proteins. In addition to high affinity primary motif interactions, we also observe interactions with secondary motifs. The ability of a number of ApiAP2 proteins to bind multiple, distinct motifs significantly increases the potential complexity of the transcriptional regulatory networks governed by the ApiAP2 family. Using these newly identified sequence motifs, we infer the trans-factors associated with previously reported plasmodial cis-elements and provide evidence that ApiAP2 proteins modulate key regulatory decisions at all stages of parasite development. Our results offer a detailed view of ApiAP2 DNA binding specificity and take the first step toward inferring comprehensive gene regulatory networks for P. falciparum.
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Affiliation(s)
- Tracey L. Campbell
- Department of Molecular Biology & Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Erandi K. De Silva
- Department of Molecular Biology & Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Kellen L. Olszewski
- Department of Molecular Biology & Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
| | - Olivier Elemento
- Institute for Computational Medicine, Weill Cornell Medical College, New York, New York, United States of America
| | - Manuel Llinás
- Department of Molecular Biology & Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey, United States of America
- * E-mail:
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13
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Development of a reverse transcription-loop-mediated isothermal amplification (RT-LAMP) for clinical detection of Plasmodium falciparum gametocytes. Parasitol Int 2010; 59:414-20. [DOI: 10.1016/j.parint.2010.05.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Revised: 05/28/2010] [Accepted: 05/28/2010] [Indexed: 11/23/2022]
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14
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Malaria gametocytogenesis. Mol Biochem Parasitol 2010; 172:57-65. [PMID: 20381542 PMCID: PMC2880792 DOI: 10.1016/j.molbiopara.2010.03.019] [Citation(s) in RCA: 159] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Revised: 03/29/2010] [Accepted: 03/30/2010] [Indexed: 02/07/2023]
Abstract
Male and female gametocytes are the components of the malaria parasite life cycle which are taken up from an infected host bloodstream by mosquitoes and thus mediate disease transmission. These gamete precursors are morphologically and functionally quite distinct from their asexual blood stage counterparts and this is reflected in their distinct patterns of gene expression, cellular development and metabolism. Recent transcriptome, proteome and reverse genetic studies have added valuable information to that obtained from traditional studies. However, we still have no answer to the fundamental question regarding sexual development: 'what triggers gametocytogenesis'? In the current climate of eradication/elimination, tackling transmission by killing gametocytes has an important place on the agenda because most antimalarial drugs, whilst killing asexual blood stage parasites, have no effect on the transmissible stages.
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15
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Regulation of gene expression in protozoa parasites. J Biomed Biotechnol 2010; 2010:726045. [PMID: 20204171 PMCID: PMC2830571 DOI: 10.1155/2010/726045] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 11/10/2009] [Accepted: 01/08/2010] [Indexed: 12/25/2022] Open
Abstract
Infections with protozoa parasites are associated with high burdens of morbidity and mortality across the developing world. Despite extensive efforts to control the transmission of these parasites, the spread of populations resistant to drugs and the lack of effective vaccines against them contribute to their persistence as major public health problems. Parasites should perform a strict control on the expression of genes involved in their pathogenicity, differentiation, immune evasion, or drug resistance, and the comprehension of the mechanisms implicated in that control could help to develop novel therapeutic strategies. However, until now these mechanisms are poorly understood in protozoa. Recent investigations into gene expression in protozoa parasites suggest that they possess many of the canonical machineries employed by higher eukaryotes for the control of gene expression at transcriptional, posttranscriptional, and epigenetic levels, but they also contain exclusive mechanisms. Here, we review the current understanding about the regulation of gene expression in Plasmodium sp., Trypanosomatids, Entamoeba histolytica and Trichomonas vaginalis.
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16
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Gopalakrishnan AM, López-Estraño C. Role of cis-regulatory elements on the ring-specific hrp3 promoter in the human parasite Plasmodium falciparum. Parasitol Res 2010; 106:833-45. [PMID: 20127361 DOI: 10.1007/s00436-010-1738-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Accepted: 01/04/2010] [Indexed: 11/30/2022]
Abstract
Identification of promoter elements responsible for regulation of gene expression has been hampered by the AT richness of P. falciparum intergenic regions. Nested deletions of histidine-rich protein 3 (hrp3) promoter suggested the presence of a multipartite ring-specific element. Linker scanning (LS) of this ring-specific promoter showed that the alteration of several promoter regions decreased the luciferase activity compared to the wild-type configuration, indicating that these regions played a role in gene expression. No homology was observed by comparison of putative regulatory elements of other genes identified by bioinformatic analysis with the hrp3 enhancer, implying a different mechanism of gene regulation by the hrp3 promoter. LS and deletion analysis of the 5' untranslated region (UTR) of the hrp3 suggested that this region contains elements which interact with promoter elements to regulate gene expression. Analysis of the intron in the UTR region suggested that this region does not play a role in stage specificity in the hrp3 promoter. Together, our results indicate the presence of multiple mechanisms of gene regulation in the parasite.
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17
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Howitt CA, Wilinski D, Llinás M, Templeton TJ, Dzikowski R, Deitsch KW. Clonally variant gene families in Plasmodium falciparum share a common activation factor. Mol Microbiol 2009; 73:1171-85. [PMID: 19708920 DOI: 10.1111/j.1365-2958.2009.06846.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The genome of the malaria parasite Plasmodium falciparum contains several multicopy gene families, including var, rifin, stevor and Pfmc-2TM. These gene families undergo expression switching and appear to play a role in antigenic variation. It has recently been shown that forcing parasites to express high copy numbers of transcriptionally active, episomal var promoters led to gradual downregulation and eventual silencing of the entire var gene family, suggesting that a limiting titratable factor plays a role in var gene activation. Through similar experiments using rifin, stevor or Pfmc-2TM episomal promoters we show that promoter titration can be used as a general method to downregulate multicopy gene families in P. falciparum. Additionally, we show that promoter titration with var, rifin, stevor or Pfmc-2TM episomal promoters results in downregulation of expression not only of the family to which the episomal promoter belongs, but also members of the other gene families, suggesting that the var-specific titratable factor previously described is shared by all four families. Further, transcriptionally active promoters from different families colocalize within the same subnuclear expression site, indicating that the role that nuclear architecture plays in var gene regulation also likely applies to the other multicopy gene families of P. falciparum.
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Affiliation(s)
- Cali A Howitt
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY, USA
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18
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Jurgelenaite R, Dijkstra TMH, Kocken CHM, Heskes T. Gene regulation in the intraerythrocytic cycle of Plasmodium falciparum. ACTA ACUST UNITED AC 2009; 25:1484-91. [PMID: 19336444 DOI: 10.1093/bioinformatics/btp179] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
MOTIVATION To date, there is little knowledge about one of the processes fundamental to the biology of Plasmodium falciparum, gene regulation including transcriptional control. We use noisy threshold models to identify regulatory sequence elements explaining membership to a gene expression cluster where each cluster consists of genes active during the part of the developmental cycle inside a red blood cell. Our approach is both able to capture the combinatorial nature of gene regulation and to incorporate uncertainty about the functionality of putative regulatory sequence elements. RESULTS We find a characteristic pattern where the most common motifs tend to be absent upstream of genes active in the first half of the cycle and present upstream of genes active in the second half. We find no evidence that motif's score, orientation, location and multiplicity improves prediction of gene expression. Through comparative genome analysis, we find a list of potential transcription factors and their associated motifs. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Rasa Jurgelenaite
- Institute for Computing and Information Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands.
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19
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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: 71] [Impact Index Per Article: 4.4] [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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20
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Petter M, Bonow I, Klinkert MQ. Diverse expression patterns of subgroups of the rif multigene family during Plasmodium falciparum gametocytogenesis. PLoS One 2008; 3:e3779. [PMID: 19020666 PMCID: PMC2582490 DOI: 10.1371/journal.pone.0003779] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Accepted: 11/02/2008] [Indexed: 12/14/2022] Open
Abstract
Background The maturation of Plasmodium falciparum gametocytes in the human host takes several days, during which the parasites need to efficiently evade the host immune system. Like asexual stage parasites, immature gametocytes can sequester at various sites in the human body, and only mature sexual stages are found in the circulation. Although the fundamental mechanisms of gametocyte immune evasion are still largely unknown, candidate molecules that may be involved include variant antigens encoded by multigene families in the P. falciparum genome, such as the PfEMP1, STEVOR and RIFIN proteins. While expression of the former two families in sexual stages has been investigated earlier, we report here RIFIN expression during gametocytogenesis. Methodology/Principal Findings Variants of two previously characterized RIFIN subfamilies (A- and B-type RIFINs) were found to be synthesized in gametocytes. Immunofluorescence experiments showed A-type RIFINs to be accumulated in a crescent-shaped pattern of discrete punctate structures at the infected erythrocyte membrane, while members of the B-type family were associated with the parasite. Transcription analysis demonstrated the existence of diverse transcriptional regulation patterns during sexual differentiation and indicated variant-specific regulation of B-type RIFINs, in contrast to group-specific regulation for A-type RIFINs. Phylogenetic analysis of 5′-upstream regions showed that the rif–gene family falls into five defined clusters, designated rups (rifupstream) A1, A2, AB, B and C. In trophozoites and early gametocytes, rif variants of the rupsA2-type were preferentially expressed. Conclusions/Significance In this work we demonstrate the expression dynamics of the rif-gene family during sexual differentiation and present indications for subgroup specific regulation patterns. Therefore, our data provide a first foundation and point to new directions for future investigations of the potential role of RIFINs in gametocyte immune evasion.
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Affiliation(s)
- Michaela Petter
- Bernhard Nocht-Institute for Tropical Medicine, Hamburg, Germany.
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21
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Berry A, Deymier C, Sertorio M, Witkowski B, Benoit-Vical F. Pfs 16 pivotal role in Plasmodium falciparum gametocytogenesis: a potential antiplasmodial drug target. Exp Parasitol 2008; 121:189-92. [PMID: 19014941 DOI: 10.1016/j.exppara.2008.10.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2008] [Revised: 10/15/2008] [Accepted: 10/24/2008] [Indexed: 11/29/2022]
Abstract
Mature gametocytes, the sexual stage of Plasmodium falciparum, ensure the continued transmission of malaria from the human host to the mosquito vector. Even if gametocytes are not implicated in the malaria physiopathology it is crucial to the spread of malaria. Gametocytes are to be a key target for drugs used against Plasmodium in public health. The expression levels of 4 sexual-stage specific genes, Pfs 16, Pfs 25, Pfg 27 and S 18S rRNA, during gametocytogenesis of various P. falciparum strains were analyzed by a real time PCR assay. The strains showed different capacities to produce mature gametocytes and in parallel different patterns of sexual gene expression. There was a correlation only between Pfs 16 cDNA overexpression in the first 48h of the culture and the production of mature gametocytes. Pfs 16 is an early marker of the development of mature gametocytes in cultures and is therefore a potential target for new antimalarial drugs.
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Affiliation(s)
- Antoine Berry
- Service de Parasitologie-Mycologie du CHU de Toulouse, Toulouse, France.
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22
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Llinás M, Deitsch KW, Voss TS. Plasmodium gene regulation: far more to factor in. Trends Parasitol 2008; 24:551-6. [PMID: 18929512 DOI: 10.1016/j.pt.2008.08.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2008] [Revised: 08/18/2008] [Accepted: 08/28/2008] [Indexed: 11/16/2022]
Abstract
Gene expression in the malaria parasite has received generous attention over the past several decades, predominantly because of the importance of var gene regulation, which is key to antigenic variation and host immune evasion. However, the role of transcriptional regulation in governing other genes expressed during the various stages of development has remained less well characterized. This mostly has been due to the lack of defined transcriptional regulators in Plasmodium parasites. Here, we describe recent advances that have become possible by joining traditional biochemistry with new technological innovations. These studies have increased our understanding of the role of transcriptional regulation, not only in the control of gene expression for antigenic variation but also in the coordination of stage-specific parasite development.
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Affiliation(s)
- Manuel Llinás
- Department of Molecular Biology, Princeton University, 246 Carl Icahn Laboratory, Princeton, NJ 08544, USA.
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23
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Gopalakrishnan AM, Nyindodo LA, Ross Fergus M, López-Estraño C. Plasmodium falciparum: Preinitiation complex occupancy of active and inactive promoters during erythrocytic stage. Exp Parasitol 2008; 121:46-54. [PMID: 18951895 DOI: 10.1016/j.exppara.2008.09.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Revised: 07/22/2008] [Accepted: 09/30/2008] [Indexed: 10/21/2022]
Abstract
Over 80% of Plasmodium falciparum genes are developmentally regulated during the parasite's life cycle with most genes expressed in a "just in time" fashion. However, the molecular mechanisms of gene regulation are still poorly understood. Analysis of P. falciparum genome shows that the parasite appears to encode relatively few transcription factors homologous to those in other eukaryotes. We used Chromatin immunoprecipitation (ChIP) to study interaction of PfTBP and PfTFIIE with stage specific Plasmodium promoters. Our results indicate that PfTBP and PfTFIIE are bound to their cognate sequence in active and inactive erythrocytic-expressed promoters. In addition, TF occupancy appears to extend beyond the promoter regions, since PfTBP interaction with the coding and 3' end regions was also detected. No PfTBP or PfTFIIE interaction was detected on csp and pfs25 genes which are not active during the erythrocytic asexual stage. Furthermore, PfTBP and PfTFIIE binding did not appear to correlate with histone 3 and/or 4 acetylation, suggesting that histone acetylation may not be a prerequisite for PfTBP or PfTFIIE promoter interaction. Based on our observations we concluded that the PfTBP/PfTFIIE-containing preinitiation complex (PIC) would be preassembled on promoters of all erythrocytic-expressed genes in a fashion independent of histone acetylation, providing support for the "poised" model. Contrary to the classical model of eukaryotic gene regulation, PIC interaction with Plasmodium promoters occurred independent of transcriptional activity and to the notion that chromatin acetylation leads to PIC assembly.
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Affiliation(s)
- Anusha M Gopalakrishnan
- Department of Biology, Life Sciences Building, Room 409B, The University of Memphis, 3774 Walker Avenue, Memphis, TN 38152, USA
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24
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Babiker HA, Schneider P. Application of molecular methods for monitoring transmission stages of malaria parasites. Biomed Mater 2008; 3:034007. [PMID: 18708712 DOI: 10.1088/1748-6041/3/3/034007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Recent technical advances in malaria research have allowed specific detection of mRNA of genes that are expressed exclusively in sexual stages (gametocytes) of malaria parasites. The specificity and sensitivity of these techniques were validated on cultured laboratory clones of both human malaria parasites (Plasmodium falciparum) and rodent parasites (P. chabaudi). More recently, quantitative molecular techniques have been developed to quantify these sexual stages and used to monitor gametocyte dynamics and their transmission to mosquitoes. Molecular techniques showed that the infectious reservoir for malaria is larger than expected from previous microscopic studies; individual parasite genotypes within an infection can simultaneously produce infectious gametocytes; gametocyte production can be sustained for several months, and is modulated by environmental factors. The above techniques have empowered approaches for in-depth analysis of the biology of the transmission stages of the parasite and epidemiology of malaria transmission.
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Affiliation(s)
- Hamza A Babiker
- Biochemistry Department, Faculty of Medicine, Sultan Qaboos University, Alkhod, PO Box 35, Muscat, Oman School of Biological Sciences, University of Edinburgh, UK.
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25
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Komaki-Yasuda K, Okuwaki M, Kano S, Nagata K, Kawazu SI. 5' sequence- and chromatin modification-dependent gene expression in Plasmodium falciparum erythrocytic stage. Mol Biochem Parasitol 2008; 162:40-51. [PMID: 18692528 DOI: 10.1016/j.molbiopara.2008.07.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Revised: 07/09/2008] [Accepted: 07/10/2008] [Indexed: 11/18/2022]
Abstract
Plasmodium falciparum, the human malaria parasite, is evolutionarily distant from other eukaryotes. Genome-wide analyses of transcription-associated proteins have revealed a relative paucity of putative regulatory transcription factors and an abundance of putative chromatin remodeling machinery, suggesting that this parasite has a transcription regulatory system that is distinct from those of other eukaryotes. Here, we have analyzed transcriptional regulation of the peroxiredoxin genes, pf1-cys-prx and pftpx-1, which show different expression patterns in P. falciparum. The reporter assays revealed the presence of putative enhancers in the 5' regions of these genes. Although pf1-cys-prx shows trophozoite/schizont stage-specific transcription, a putative cis-acting enhancer sequence in pf1-cys-prx was constitutively active when inserted into the 5' region of pftpx-1. Electrophoretic mobility shift and DNase I footprinting assays showed that this enhancer region is the target of trophozoite/schizont stage-specific DNA binding proteins. In addition, chromatin immunoprecipitation assays showed that the increased levels of histone acetylation in the 5' region of pf1-cys-prx and pftpx-1 correlate with the transcriptional activity of these genes. Recruitment of PfGCN5 histone acetyltransferase to the pf1-cys-prx enhancer in trophozoite/schizont stage was observed. These results suggest that P. falciparum possesses a sophisticated system of transcriptional regulation during intraerythrocytic stages that is managed by coordinated interactions of unique cis-elements and trans-acting factors and chromatin modifications.
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26
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Coleman BI, Duraisingh MT. Transcriptional control and gene silencing in Plasmodium falciparum. Cell Microbiol 2008; 10:1935-46. [PMID: 18637022 DOI: 10.1111/j.1462-5822.2008.01203.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Infection with the apicomplexan parasite Plasmodium falciparum is associated with a high burden of morbidity and mortality across the developing world, yet the mechanisms of transcriptional control in this organism are poorly understood. While P. falciparum possesses many of the characteristics common to eukaryotic transcription, including much of the canonical machinery, it also demonstrates unique patterns of gene expression and possesses unusually AT-rich intergenic sequences. Importantly, several biological processes that are critical to parasite virulence involve highly regulated patterns of gene expression and silencing. The relative scarcity of transcription-associated proteins and specific cis-regulatory motifs recognized in the P. falciparum genome have been thought to reflect a reduced role for transcription factors in transcriptional control in these parasites. New approaches and technologies, however, have led to the discovery of many more of these elements, including an expanded family of DNA-binding proteins, and a re-assessment of this hypothesis is required. We review the current understanding of transcriptional control in P. falciparum, specifically highlighting promoter-driven and epigenetic mechanisms involved in the control of transcription initiation.
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Affiliation(s)
- Bradley I Coleman
- Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
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27
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Gissot M, Ting LM, Daly TM, Bergman LW, Sinnis P, Kim K. High mobility group protein HMGB2 is a critical regulator of plasmodium oocyst development. J Biol Chem 2008; 283:17030-8. [PMID: 18400754 DOI: 10.1074/jbc.m801637200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The sexual cycle of Plasmodium is required for transmission of malaria from mosquitoes to mammals, but how parasites induce the expression of genes required for the sexual stages is not known. We disrupted the Plasmodium yoelii gene encoding high mobility group nuclear factor hmgb2, which encodes a DNA-binding protein potentially implicated in transcriptional regulation of malaria gene expression. We investigated its function in vivo in the vertebrate and invertebrate hosts. Deltapyhmgb2 parasites develop into gametocytes but have drastic impairment of oocyst formation. A global transcriptome analysis of the Deltapyhmgb2 parasites identified approximately 30 genes whose expression is down-regulated in the Deltapyhmgb2 parasites. These genes are conserved in all malaria species, and more than 90% of these genes show a peak of mRNA expression at the gametocyte stage. Surprisingly, the transcripts coding for the Plasmodium berghei orthologues of those genes are stored and translated in the ookinete stage. Therefore, sexual stage protein expression appears to be both transcriptionally and translationally regulated with Plasmodium HMGB2 acting as an important regulator of malaria sexual stage gene expression.
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Affiliation(s)
- Mathieu Gissot
- Department of Medicine and of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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28
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Olivieri A, Silvestrini F, Sanchez M, Alano P. A 140-bp AT-rich sequence mediates positive and negative transcriptional control of a Plasmodium falciparum developmentally regulated promoter. Int J Parasitol 2008; 38:299-312. [DOI: 10.1016/j.ijpara.2007.08.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2007] [Revised: 08/14/2007] [Accepted: 08/15/2007] [Indexed: 11/26/2022]
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29
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Law PJ, Claudel-Renard C, Joubert F, Louw AI, Berger DK. MADIBA: a web server toolkit for biological interpretation of Plasmodium and plant gene clusters. BMC Genomics 2008; 9:105. [PMID: 18307768 PMCID: PMC2277412 DOI: 10.1186/1471-2164-9-105] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2007] [Accepted: 02/28/2008] [Indexed: 11/10/2022] Open
Abstract
Background Microarray technology makes it possible to identify changes in gene expression of an organism, under various conditions. Data mining is thus essential for deducing significant biological information such as the identification of new biological mechanisms or putative drug targets. While many algorithms and software have been developed for analysing gene expression, the extraction of relevant information from experimental data is still a substantial challenge, requiring significant time and skill. Description MADIBA (MicroArray Data Interface for Biological Annotation) facilitates the assignment of biological meaning to gene expression clusters by automating the post-processing stage. A relational database has been designed to store the data from gene to pathway for Plasmodium, rice and Arabidopsis. Tools within the web interface allow rapid analyses for the identification of the Gene Ontology terms relevant to each cluster; visualising the metabolic pathways where the genes are implicated, their genomic localisations, putative common transcriptional regulatory elements in the upstream sequences, and an analysis specific to the organism being studied. Conclusion MADIBA is an integrated, online tool that will assist researchers in interpreting their results and understand the meaning of the co-expression of a cluster of genes. Functionality of MADIBA was validated by analysing a number of gene clusters from several published experiments – expression profiling of the Plasmodium life cycle, and salt stress treatments of Arabidopsis and rice. In most of the cases, the same conclusions found by the authors were quickly and easily obtained after analysing the gene clusters with MADIBA.
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Affiliation(s)
- Philip J Law
- Bioinformatics and Computational Biology Unit, African Centre for Gene Technologies (ACGT), Department of Biochemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, 0002, South Africa.
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30
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Garcia CRS, de Azevedo MF, Wunderlich G, Budu A, Young JA, Bannister L. Plasmodium in the postgenomic era: new insights into the molecular cell biology of malaria parasites. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 266:85-156. [PMID: 18544493 DOI: 10.1016/s1937-6448(07)66003-1] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In this review, we bring together some of the approaches toward understanding the cellular and molecular biology of Plasmodium species and their interaction with their host red blood cells. Considerable impetus has come from the development of new methods of molecular genetics and bioinformatics, and it is important to evaluate the wealth of these novel data in the context of basic cell biology. We describe how these approaches are gaining valuable insights into the parasite-host cell interaction, including (1) the multistep process of red blood cell invasion by the merozoite; (2) the mechanisms by which the intracellular parasite feeds on the red blood cell and exports parasite proteins to modify its cytoadherent properties; (3) the modulation of the cell cycle by sensing the environmental tryptophan-related molecules; (4) the mechanism used to survive in a low Ca(2+) concentration inside red blood cells; (5) the activation of signal transduction machinery and the regulation of intracellular calcium; (6) transfection technology; and (7) transcriptional regulation and genome-wide mRNA studies in Plasmodium falciparum.
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Affiliation(s)
- Celia R S Garcia
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, CEP 05508-900, São Paulo, SP, Brazil
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Wargo AR, de Roode JC, Huijben S, Drew DR, Read AF. Transmission stage investment of malaria parasites in response to in-host competition. Proc Biol Sci 2007; 274:2629-38. [PMID: 17711832 PMCID: PMC1975767 DOI: 10.1098/rspb.2007.0873] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Conspecific competition occurs in a multitude of organisms, particularly in parasites, where several clones are commonly sharing limited resources inside their host. In theory, increased or decreased transmission investment might maximize parasite fitness in the face of competition, but, to our knowledge, this has not been tested experimentally. We developed and used a clone-specific, stage-specific, quantitative PCR protocol to quantify Plasmodium chabaudi replication and transmission stage densities in mixed-clone infections. We co-infected mice from two strains with an avirulent and virulent parasite clone and found competitive suppression of in-host (blood-stage) parasite densities and generally corresponding reductions in transmission stage production, with the virulent clone obtaining overall competitive superiority. In response to competitive suppression, there was little evidence of any alteration in transmission stage investment, apart from a small reduction by one of the two clones in one of the two host strains. This alteration did not result in a competitive advantage, although it might have reduced the disadvantage. This study supports much of the current literature, which predicts that conspecific in-host competition will result in a competitive advantage and positive selection for virulent clones and thus the evolution of higher virulence.
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Affiliation(s)
- Andrew R Wargo
- Institutes of Evolution, Immunology and Infection Research, Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, The King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
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Imamura H, Persampieri JH, Chuang JH. Sequences conserved by selection across mouse and human malaria species. BMC Genomics 2007; 8:372. [PMID: 17937810 PMCID: PMC2174483 DOI: 10.1186/1471-2164-8-372] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Accepted: 10/15/2007] [Indexed: 11/22/2022] Open
Abstract
Background Little is known, either experimentally or computationally, about the genomic sequence features that regulate malaria genes. A sequence conservation analysis of the malaria species P. falciparum, P. berghei, P. yoelii, and P. chabaudi could significantly advance knowledge of malaria gene regulation. Results We computationally identify intergenic sequences conserved beyond neutral expectations, using a conservation algorithm that accounts for the strong compositional biases in malaria genomes. We first quantify the composition-specific divergence at silent positions in coding sequence. Using this as a background, we examine gene 5' regions, identifying 610 blocks conserved far beyond neutral expectations across the three mouse malariae, and 81 blocks conserved as strongly across all four species (p < 10-6). Detailed analysis of these blocks indicates that only a minor fraction are likely to be previously unknown coding sequences. Analogous noncoding conserved blocks have been shown to regulate adjacent genes in other phylogenies, making the predicted blocks excellent candidates for novel regulatory functions. We also find three potential transcription factor binding motifs which exhibit strong conservation and overrepresentation among the rodent malariae. Conclusion A broader finding of our analysis is that less malaria intergenic sequence has been conserved by selection than in yeast or vertebrate genomes. This supports the hypothesis that transcriptional regulation is simpler in malaria than other eukaryotic species. We have built a public database containing all sequence alignments and functional predictions, and we expect this to be a valuable resource to the malaria research community.
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Affiliation(s)
- Hideo Imamura
- Boston College - Department of Biology, 140 Commonwealth Avenue, Chestnut Hill, MA 02467, USA.
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Gissot M, Kelly KA, Ajioka JW, Greally JM, Kim K. Epigenomic modifications predict active promoters and gene structure in Toxoplasma gondii. PLoS Pathog 2007; 3:e77. [PMID: 17559302 PMCID: PMC1891328 DOI: 10.1371/journal.ppat.0030077] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Accepted: 04/17/2007] [Indexed: 11/23/2022] Open
Abstract
Mechanisms of gene regulation are poorly understood in Apicomplexa, a phylum that encompasses deadly human pathogens like Plasmodium and Toxoplasma. Initial studies suggest that epigenetic phenomena, including histone modifications and chromatin remodeling, have a profound effect upon gene expression and expression of virulence traits. Using the model organism Toxoplasma gondii, we characterized the epigenetic organization and transcription patterns of a contiguous 1% of the T. gondii genome using custom oligonucleotide microarrays. We show that methylation and acetylation of histones H3 and H4 are landmarks of active promoters in T. gondii that allow us to deduce the position and directionality of gene promoters with >95% accuracy. These histone methylation and acetylation “activation” marks are strongly associated with gene expression. We also demonstrate that the pattern of histone H3 arginine methylation distinguishes certain promoters, illustrating the complexity of the histone modification machinery in Toxoplasma. By integrating epigenetic data, gene prediction analysis, and gene expression data from the tachyzoite stage, we illustrate feasibility of creating an epigenomic map of T. gondii tachyzoite gene expression. Further, we illustrate the utility of the epigenomic map to empirically and biologically annotate the genome and show that this approach enables identification of previously unknown genes. Thus, our epigenomics approach provides novel insights into regulation of gene expression in the Apicomplexa. In addition, with its compact genome, genetic tractability, and discrete life cycle stages, T. gondii provides an important new model to study the evolutionarily conserved components of the histone code. Apicomplexan parasites, including Toxoplasma gondii, are responsible for a variety of deadly infections, but little is understood about how these important pathogens regulate gene expression. Initial studies suggest that alterations in chromatin structure regulate expression of virulence traits. To understand the relationship of chromatin remodeling and transcriptional regulation in T. gondii, we characterized the histone modifications and gene expression of a contiguous 1% of the T. gondii genome using custom DNA oligonucleotide microarrays. We found that active promoters have a characteristic pattern of histone modifications that correlates strongly with active gene expression in tachyzoites. These data, integrated with prior gene predictions, enable more accurate annotation of the genome and discovery of new genes. Further, these studies illustrate the power of an integrated epigenomic approach to illuminate the role of the “histone code” in regulation of gene expression in the Apicomplexa.
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Affiliation(s)
- Mathieu Gissot
- Department of Medicine (Infectious Diseases), Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Krystyna A Kelly
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- Medical Research Council Biostatistics Unit, Institute of Public Health, Cambridge, United Kingdom
| | - James W Ajioka
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - John M Greally
- Department of Medicine (Hematology), Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Kami Kim
- Department of Medicine (Infectious Diseases), Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * To whom correspondence should be addressed. E-mail:
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López-Estraño C, Gopalakrishnan AM, Semblat JP, Fergus MR, Mazier D, Haldar K. An enhancer-like region regulates hrp3 promoter stage-specific gene expression in the human malaria parasite Plasmodium falciparum. ACTA ACUST UNITED AC 2007; 1769:506-13. [PMID: 17570541 PMCID: PMC2267920 DOI: 10.1016/j.bbaexp.2007.04.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Revised: 04/25/2007] [Accepted: 04/26/2007] [Indexed: 01/05/2023]
Abstract
The asexual blood stage of Plasmodium falciparum is comprised of morphologically distinct ring, trophozoite and schizont stages. Each of these developmental stages possesses a distinct pattern of gene expression. Regulation of P. falciparum gene expression is thought to occur, at least in part, at the promoter level. Previously, we have found that although the hrp3 mRNA is only seen in ring-stage parasites, deletion of a specific sequence in the 5' end of the promoter region decreased ring-stage expression of hrp3 and enabled detection of its transcripts in trophozoite-stage parasites. In order to investigate this stage specific regulation of gene expression, we employed a series of nested deletions of the 1.7-kb hrp3 promoter. Firefly luciferase gene was used as a reporter to evaluate the role of promoter sequences in gene regulation. Using this approach, we identified a ring-stage specific regulatory region on the hrp3 promoter located between -1.7 kb and -1.1 kb from the ATG initiation codon. Small 100-150 bp truncations on this enhancer-like region failed to uncover discrete regulatory sequences, suggesting the multipartite nature of this element. The data presented in this study demonstrate that stage specific promoter activity of the hrp3 gene in P. falciparum blood stage parasites is supported, at least in-part, by a small promoter region that can function in the absence of a larger chromosomal context.
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Affiliation(s)
- Carlos López-Estraño
- Department of Biology, Life Sciences Bldg. Room 409B, The University of Memphis, 3774 Walker Ave. Memphis, Tennessee 38152, USA.
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Promoter regions of Plasmodium vivax are poorly or not recognized by Plasmodium falciparum. Malar J 2007; 6:20. [PMID: 17313673 PMCID: PMC1805447 DOI: 10.1186/1475-2875-6-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2006] [Accepted: 02/21/2007] [Indexed: 11/18/2022] Open
Abstract
Background Heterologous promoter analysis in Plasmodium has revealed the existence of conserved cis regulatory elements as promoters from different species can drive expression of reporter genes in heterologous transfection assays. Here, the functional characterization of different Plasmodium vivax promoters in Plasmodium falciparum using luciferase as the reporter gene is presented. Methods Luciferase reporter plasmids harboring the upstream regions of the msp1, dhfr, and vir3 genes as well as the full-length intergenic regions of the vir23/24 and ef-1α genes of P. vivax were constructed and transiently transfected in P. falciparum. Results Only the constructs with the full-length intergenic regions of the vir23/24 and ef-1α genes were recognized by the P. falciparum transcription machinery albeit to values approximately two orders of magnitude lower than those reported by luc plasmids harbouring promoter regions from P. falciparum and Plasmodium berghei. A bioinformatics approach allowed the identification of a motif (GCATAT) in the ef-1α intergenic region that is conserved in five Plasmodium species but is degenerate (GCANAN) in P. vivax. Mutations of this motif in the P. berghei ef-1α promoter region decreased reporter expression indicating it is active in gene expression in Plasmodium. Conclusion Together, this data indicates that promoter regions of P. vivax are poorly or not recognized by the P. falciparum transcription machinery suggesting the existence of P. vivax-specific transcription regulatory elements.
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López-Estraño C, Semblat JP, Gopalakrishnan AM, Turner L, Mazier D, Haldar K. Plasmodium falciparum: hrp3 promoter region is associated with stage-specificity and episomal recombination. Exp Parasitol 2007; 116:327-33. [PMID: 17367782 PMCID: PMC2267921 DOI: 10.1016/j.exppara.2007.01.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2006] [Revised: 12/27/2006] [Accepted: 01/22/2007] [Indexed: 10/23/2022]
Abstract
The asexual blood stage of Plasmodium falciparum in the human host is comprised of morphologically distinct ring, trophozoite and schizont stages, each of which possesses a distinct pattern of gene expression. Episomal promoter recombination has been recently reported in malaria parasites. We aim to investigate the nature of this process, and its relationship with promoter activity by employing a series of nested deletions of the ring-specific hrp3 promoter. Our results showed a discrete promoter region that is preferentially used for recombination. The P. falciparum hrp3 mRNA is only seen in ring-stage parasites but deletion of the recombination region was associated with decreased ring-stage expression and concurrent detection of transcripts in trophozoite-stage parasites. Our results describe a ring-stage specific regulatory region possibly involved in episomal promoter recombination, suggesting that common sequences might mediate both processes.
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Affiliation(s)
- Carlos López-Estraño
- Department of Biology, Life Sciences Building, Room 409B, The University of Memphis, Memphis, TN 38152, USA.
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Gunasekera AM, Myrick A, Militello KT, Sims JS, Dong CK, Gierahn T, Le Roch K, Winzeler E, Wirth DF. Regulatory motifs uncovered among gene expression clusters in Plasmodium falciparum. Mol Biochem Parasitol 2007; 153:19-30. [PMID: 17307259 DOI: 10.1016/j.molbiopara.2007.01.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2006] [Revised: 11/29/2006] [Accepted: 01/10/2007] [Indexed: 10/23/2022]
Abstract
Control of gene expression is poorly understood in the Plasmodium system, where relatively few homologues to known eukaryotic transcription factors have been uncovered. Recent evidence suggests that the parasite may utilize a combinatorial mode of gene regulation, with multiple cis-acting sequences contributing to overall activity at individual promoters [1]. To further probe this mechanism of control, we first searched for over-represented sequence motifs among gene clusters sharing similar expression profiles in Plasmodium falciparum. More specifically, we applied bioinformatic tools to a previously characterized micro-array data set from drug-treated asexual stage cultures (Gunasekera et al., submitted). Cluster analysis of 600 drug responsive genes identified only a single 5' motif, GAGAGAA. Two additional 5' motifs, ACTATAAAGA and TGCAC, were also shared among loci displaying patterns of coordinate expression across varying asexual growth stages. Secondly and most importantly, the functional relevance of each motif was tested in two independent assays-transient transfection and gel-retardation experiments. The GAGAGAA and TGCAC motifs were both active in the former. The GAGAGAA and ACTATAAAGA elements formed specific RNA-protein, but not DNA-protein complexes in gel shift assays, suggesting a key level of control at the RNA level. This is the first report of functionally characterized motifs in P. falciparum that were uncovered following clustering analysis of its asexual stage transcriptome. Together, both the bioinformatic and functional data reported here imply that multiple forms of gene regulation, including post-transcriptional control, may be important in the malarial system.
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Affiliation(s)
- Anusha M Gunasekera
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Harvard University, Boston, MA, USA
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Tham WH, Payne PD, Brown GV, Rogerson SJ. Identification of basic transcriptional elements required for rif gene transcription. Int J Parasitol 2006; 37:605-15. [PMID: 17196595 DOI: 10.1016/j.ijpara.2006.11.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2006] [Revised: 11/16/2006] [Accepted: 11/19/2006] [Indexed: 10/23/2022]
Abstract
The rif gene family is the largest multi-gene family in the malaria parasite Plasmodium falciparum. The gene products of rif genes, rifins, are clonally variant and transported to the surface of the infected erythrocyte where they are targets of the human immune response. Maximal rif transcription occurs during the late ring to early trophozoite stages of the intra-erythrocytic cycle. The factors involved in the transcriptional activation and repression of rif genes are not known. In this paper, we characterize several DNA elements involved in the regulation of rif transcription. We identify the upstream region that contains a functional promoter and the transcriptional start site of a rif gene. In addition, we identify two distinct regions within the rif upstream region involved in the transcriptional repression of these genes. These repressor sites are bound by nuclear protein factors expressed in different stages of the Plasmodium life cycle. We propose that the differential timing of binding provides a mechanism for the temporal repression of rif genes. In addition, we find that transcription profiles of upsA var genes and their neighbouring rif genes are unlinked.
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Affiliation(s)
- Wai-Hong Tham
- Department of Medicine, University of Melbourne, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia.
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Watanabe J, Wakaguri H, Sasaki M, Suzuki Y, Sugano S. Comparasite: a database for comparative study of transcriptomes of parasites defined by full-length cDNAs. Nucleic Acids Res 2006; 35:D431-8. [PMID: 17151081 PMCID: PMC1781114 DOI: 10.1093/nar/gkl1039] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Comparasite is a database for comparative studies of transcriptomes of parasites. In this database, each data is defined by the full-length cDNAs from various apicomplexan parasites. It integrates seven individual databases, Full-Parasites, consisting of numerous full-length cDNA clones that we have produced and sequenced: 12 484 cDNA sequences from Plasmodium falciparum, 11 262 from Plasmodium yoelii, 9633 from Plasmodium vivax, 1518 from Plasmodium berghei, 7400 from Toxoplasma gondii, 5921 from Cryptosporidium parvum and 10 966 from the tapeworm Echinococcus multilocularis. Putatively counterpart gene groups are clustered and comparative analysis of any combination of six apicomplexa species is implemented, such as interspecies comparisons regarding protein motifs (InterPro), predicted subcellular localization signals (PSORT), transmembrane regions (SOSUI) or upstream promoter elements. By specifying keywords and other search conditions, Comparasite retrieves putative counterpart gene groups containing a given feature in common or in a species-specific manner. By enabling multi-faceted comparative analyses of genes of apicomplexa protozoa, monophyletic organisms that have evolved to diversify to parasitize various hosts by adopting complex life cycles, Comparasite should help elucidate the mechanism behind parasitism. Our full-length cDNA databases and Comparasite are accessible from .
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Affiliation(s)
- Junichi Watanabe
- Department of Parasitology, Institute of Medical Science, Graduate School of Frontier Sciences, University of Tokyo, 4-6-1, Shirokanedai, Minatoku, Tokyo 108-8639, Japan.
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Abstract
One of the goals of systems-biology research is to discover networks and interactions by integrating diverse data sets. So far, systems-biology research has focused on model organisms, which are well characterized and therefore suited to testing new methods. Systems biology has great potential for use in the search for therapies for disease. Here, the potential of systems-biology approaches in the search for new drugs and vaccines to treat malaria is examined.
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Affiliation(s)
- Elizabeth A Winzeler
- Department of Cell Biology, ICND202, The Scripps Research Institute, La Jolla, California 92037, 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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Young JA, Fivelman QL, Blair PL, de la Vega P, Le Roch KG, Zhou Y, Carucci DJ, Baker DA, Winzeler EA. The Plasmodium falciparum sexual development transcriptome: a microarray analysis using ontology-based pattern identification. Mol Biochem Parasitol 2005; 143:67-79. [PMID: 16005087 DOI: 10.1016/j.molbiopara.2005.05.007] [Citation(s) in RCA: 242] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Revised: 04/29/2005] [Accepted: 05/20/2005] [Indexed: 01/24/2023]
Abstract
The sexual stages of malarial parasites are essential for the mosquito transmission of the disease and therefore are the focus of transmission-blocking drug and vaccine development. In order to better understand genes important to the sexual development process, the transcriptomes of high-purity stage I-V Plasmodium falciparum gametocytes were comprehensively profiled using a full-genome high-density oligonucleotide microarray. The interpretation of this transcriptional data was aided by applying a novel knowledge-based data-mining algorithm termed ontology-based pattern identification (OPI) using current information regarding known sexual stage genes as a guide. This analysis resulted in the identification of a sexual development cluster containing 246 genes, of which approximately 75% were hypothetical, exhibiting highly-correlated, gametocyte-specific expression patterns. Inspection of the upstream promoter regions of these 246 genes revealed putative cis-regulatory elements for sexual development transcriptional control mechanisms. Furthermore, OPI analysis was extended using current annotations provided by the Gene Ontology Consortium to identify 380 statistically significant clusters containing genes with expression patterns characteristic of various biological processes, cellular components, and molecular functions. Collectively, these results, available as part of a web-accessible OPI database (http://carrier.gnf.org/publications/Gametocyte), shed light on the components of molecular mechanisms underlying parasite sexual development and other areas of malarial parasite biology.
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Affiliation(s)
- Jason A Young
- Department of Cell Biology ICND202, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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Trager W. What triggers the gametocyte pathway in Plasmodium falciparum? Trends Parasitol 2005; 21:262-4. [PMID: 15922244 DOI: 10.1016/j.pt.2005.04.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Revised: 02/28/2005] [Accepted: 04/11/2005] [Indexed: 11/17/2022]
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Callebaut I, Prat K, Meurice E, Mornon JP, Tomavo S. Prediction of the general transcription factors associated with RNA polymerase II in Plasmodium falciparum: conserved features and differences relative to other eukaryotes. BMC Genomics 2005; 6:100. [PMID: 16042788 PMCID: PMC1199594 DOI: 10.1186/1471-2164-6-100] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2005] [Accepted: 07/23/2005] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND To date, only a few transcription factors have been identified in the genome of the parasite Plasmodium falciparum, the causative agent of malaria. Moreover, no detailed molecular analysis of its basal transcription machinery, which is otherwise well-conserved in the crown group of eukaryotes, has yet been reported. In this study, we have used a combination of sensitive sequence analysis methods to predict the existence of several parasite encoded general transcription factors associated with RNA polymerase II. RESULTS Several orthologs of general transcription factors associated with RNA polymerase II can be predicted among the hypothetical proteins of the P. falciparum genome using the two-dimensional Hydrophobic Cluster Analysis (HCA) together with profile-based search methods (PSI-BLAST). These predicted orthologous genes encoding putative transcription factors include the large subunit of TFIIA and two candidates for its small subunit, the TFIIE beta-subunit, which would associate with the previously known TFIIE alpha-subunit, the TFIIF beta-subunit, as well as the p62/TFB1 subunit of the TFIIH core. Within TFIID, the putative orthologs of TAF1, TAF2, TAF7 and TAF10 were also predicted. However, no candidates for TAFs with classical histone fold domain (HFD) were found, suggesting an unusual architecture of TFIID complex of RNA polymerase II in the parasite. CONCLUSION Taken together, these results suggest that more general transcription factors may be present in the P. falciparum proteome than initially thought. The prediction of these orthologous general transcription factors opens the way for further studies dealing with transcriptional regulation in P. falciparum. These alternative and sensitive sequence analysis methods can help to identify candidates for other transcriptional regulatory factors in P. falciparum. They will also facilitate the prediction of biological functions for several orphan proteins from other apicomplexan parasites such as Toxoplasma gondii, Cryptosporidium parvum and Eimeria.
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Affiliation(s)
- Isabelle Callebaut
- Centre National de la Recherche Scientifique CNRS UMR7590, Universités Paris 6 et Paris 7, Département de Biologie Structurale, IMPMC, case 115, 4 place Jussieu, 75252 Paris Cedex 05, France
| | - Karine Prat
- Centre National de la Recherche Scientifique CNRS UMR7590, Universités Paris 6 et Paris 7, Département de Biologie Structurale, IMPMC, case 115, 4 place Jussieu, 75252 Paris Cedex 05, France
| | - Edwige Meurice
- Centre National de la Recherche Scientifique CNRS UMR 8576, Université des Sciences et Technologies de Lille, Equipe de Parasitologie Moléculaire, Laboratoire de Chimie Biologique, UGSF, Bâtiment C9, 59655 Villeneuve d'Ascq, France
| | - Jean-Paul Mornon
- Centre National de la Recherche Scientifique CNRS UMR7590, Universités Paris 6 et Paris 7, Département de Biologie Structurale, IMPMC, case 115, 4 place Jussieu, 75252 Paris Cedex 05, France
| | - Stanislas Tomavo
- Centre National de la Recherche Scientifique CNRS UMR 8576, Université des Sciences et Technologies de Lille, Equipe de Parasitologie Moléculaire, Laboratoire de Chimie Biologique, UGSF, Bâtiment C9, 59655 Villeneuve d'Ascq, France
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Ruvalcaba-Salazar OK, del Carmen Ramírez-Estudillo M, Montiel-Condado D, Recillas-Targa F, Vargas M, Hernández-Rivas R. Recombinant and native Plasmodium falciparum TATA-binding-protein binds to a specific TATA box element in promoter regions. Mol Biochem Parasitol 2005; 140:183-96. [PMID: 15760658 DOI: 10.1016/j.molbiopara.2005.01.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2004] [Revised: 01/05/2005] [Accepted: 01/06/2005] [Indexed: 10/25/2022]
Abstract
RNA polymerase II promoters in Plasmodium spp., like in most eukaryotes, have a bipartite structure. However, the identification of a functional TATA box located within the Plasmodium spp. core promoters has been difficult, mainly because of its high A+T content. Only few putative trans-acting elements have been identified in the malaria parasite genome such as a gene orthologous to the TATA box binding protein (PfTBP). In this study, we demonstrate that PfTBP is part of the DNA-protein complexes formed in the kahrp and gbp-130 gene promoter regions. Supershift and footprinting assays performed with a GST-PfTBP fusion protein showed that PfTBP associates with a consensus TATA box sequence located 81 base pairs upstream of the transcription start site in the kahrp promoter region and with a TATA box-like (TGTAA) sequence at position -186 of the gbp-130 gene promoter region. Chromatin immunoprecipitation assays confirmed that native PfTBP is able to associate in vivo with both TATA box elements. This is the first study that reports the identification of cis-acting sequences (TATAA and TGTAA) and their corresponding trans-acting (PfTBP) factor in P. falciparum.
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Affiliation(s)
- Omar K Ruvalcaba-Salazar
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (IPN), Apartado Postal 14-740, 07360 México
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Polson HEJ, Blackman MJ. A role for poly(dA)poly(dT) tracts in directing activity of the Plasmodium falciparum calmodulin gene promoter. Mol Biochem Parasitol 2005; 141:179-89. [PMID: 15850701 DOI: 10.1016/j.molbiopara.2005.02.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2004] [Revised: 02/08/2005] [Accepted: 02/13/2005] [Indexed: 11/30/2022]
Abstract
Expression of the Plasmodium falciparum calmodulin gene (pfcam) is developmentally regulated throughout the blood-stage cycle. The promoter lies within approximately 1 kb of intergenic sequence that separates the pfcam open reading frame (ORF) from an upstream inverted ORF encoding a product homologous to the co-chaperone STI1. Using the oligo-capping method, which selectively reverse-transcribes cDNA from only full-length, capped transcript, we have mapped multiple transcription-initiation sites for both genes. Transcription of the pfSTI1 gene initiates over a 150 bp region centred approximately 350 bp upstream of the ORF. The pfcam transcription start sites cluster into four approximately 30 bp regions lying within 180 bp upstream of the pfcam ORF, generating transcripts with 5' untranslated regions (UTR) of 3-173 nucleotides in length. Remarkably, splicing was found to be related to UTR length, with apparent preferential splicing of longer transcripts. Activity of the pfcam promoter diminished in a linear fashion to undetectable levels upon step-wise removal of sequence between 625 and 230 bp upstream of the start ATG. Electromobility-shift assays demonstrated nuclear factor binding to eight oligonucleotide probes spanning 657 bp of the pfcam ORF proximal upstream sequence. The degree of binding correlated with the density of poly(dA)poly(dT) tracts within the probes, and in all cases could be inhibited by excess synthetic poly(dA)poly(dT), but not by poly(dAdT)poly(dAdT). The multiple transcription-initiation sites of both pfSTI1 and pfcam genes lie just downstream of 25 bp-long poly(dA)poly(dT) tracts, and the intergenic region contains over 20 poly(dA)poly(dT) tracts of 4 bp or more. Our results suggest that the basal pfcam promoter is situated between approximately -300 and -230 bp upstream of the pfcam ORF and that the P. falciparum transcription-initiation complex has a low degree of sequence-specificity for the sites of initiation but preferentially acts downstream of long poly(dA)poly(dT) tracts.
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Affiliation(s)
- Hannah E J Polson
- Division of Parasitology, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
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Schneider P, Schoone G, Schallig H, Verhage D, Telgt D, Eling W, Sauerwein R. Quantification of Plasmodium falciparum gametocytes in differential stages of development by quantitative nucleic acid sequence-based amplification. Mol Biochem Parasitol 2005; 137:35-41. [PMID: 15279949 DOI: 10.1016/j.molbiopara.2004.03.018] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2003] [Revised: 02/25/2004] [Accepted: 03/17/2004] [Indexed: 11/22/2022]
Abstract
Two quantitative nucleic acid sequence-based amplification assays (QT-NASBA) based on Pfs16 and Pfs25, have been developed to quantify sexual stage commitment and mature gametocytes of Plasmodium falciparum. Pfs16 mRNA is expressed in all sexual forms including sexually committed ring stages while expression of Pfs25 mRNA is restricted to late stage gametocytes. Both assays showed a sensitivity of one sexual stage parasite/microl of blood. Blood samples from experimentally infected non-immune human volunteers were tested for Plasmodium falciparum by standard microscopy, a previously developed asexual 18S rRNA QT-NASBA, Pfs16 and Pfs25 mRNA QT-NASBA. Pfs16 QT-NASBA was positive in 9 out of 10 volunteers within 48 h after first detection of 18S rRNA, mostly before or at the day of positive microscopy. In contrast, the Pfs25 mRNA QT-NASBA was negative during the 28 days of follow-up, but consistently positive in gametocyte samples from naturally infected Kenyan patients. These data suggest that sexual stage commitment can occur early in the blood-stage infection without successful maturation into infectious gametocytes. In conclusion, Pfs16 and Pfs25 QT-NASBA assays in combination with a previously developed asexual stage QT-NASBA allow for the separate quantification of all developmental stages present in the circulation. The application of sexual stage QT-NASBA assays may contribute to a better understanding of the biology and epidemiology of malaria transmission.
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Affiliation(s)
- Petra Schneider
- Department of Medical Microbiology, University Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
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Gissot M, Briquet S, Refour P, Boschet C, Vaquero C. PfMyb1, a Plasmodium falciparum transcription factor, is required for intra-erythrocytic growth and controls key genes for cell cycle regulation. J Mol Biol 2004; 346:29-42. [PMID: 15663925 DOI: 10.1016/j.jmb.2004.11.045] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2004] [Revised: 11/18/2004] [Accepted: 11/18/2004] [Indexed: 11/23/2022]
Abstract
During the complex life cycle of Plasmodium falciparum, divided between mosquito and human hosts, the regulation of morphologic changes implies a fine control of transcriptional regulation. Transcriptional control, however, and in particular its molecular actors, transcription factors and regulatory motifs, are as yet poorly described in Plasmodium. In order to decipher the molecular mechanisms implicated in transcriptional regulation, a transcription factor belonging to the tryptophan cluster family was studied. In a previous work, the PfMyb1 protein, contained in nuclear extracts, was shown to have DNA binding activity and to interact specifically with myb regulatory elements. We used long pfmyb1 double-stranded RNA (dsRNA) to interfere with the cognate messenger expression. Parasite cultures treated with pfmyb1 dsRNA exhibited a 40% growth inhibition when compared with either untreated cultures or cultures treated with unrelated dsRNA, and parasite mortality occurred during trophozoite to schizont transition. In addition, the pfmyb1 transcript and protein decreased by as much as 80% in treated trophozoite cultures at the time of their maximum expression. The global effect of this partial loss of transcript and protein was investigated using a thematic DNA microarray encompassing genes involved in signal transduction, cell cycle and transcriptional regulation. SAM software enabled us to identify several genes that were differentially expressed and probably directly or indirectly under the control of PfMyb1. Using chromatin immuno-precipitation, we demonstrated that PfMyb1 binds, within the parasite nuclei, to several promoters and therefore participates directly in the transcriptional regulation of the corresponding genes. This study provides the first evidence of a regulation network involving a Plasmodium transcription factor.
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Affiliation(s)
- Mathieu Gissot
- INSERM U511, CHU Pitié-Salpêtrière, 91 boulevard de l'Hôpital, 75013 Paris, France
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Kumar N, Cha G, Pineda F, Maciel J, Haddad D, Bhattacharyya M, Nagayasu E. Molecular complexity of sexual development and gene regulation in Plasmodium falciparum. Int J Parasitol 2004; 34:1451-8. [PMID: 15582522 DOI: 10.1016/j.ijpara.2004.10.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2004] [Revised: 10/19/2004] [Accepted: 10/19/2004] [Indexed: 11/28/2022]
Abstract
The malaria parasite, Plasmodium falciparum, has a complex life cycle which alternates between the vertebrate host and the invertebrate vector. Various morphological changes as well as stage-specific transcripts and gene expression profiles that accompany parasite's asexual and sexual life cycle suggest that gene regulation is crucial for the parasite's continual adaptations to survive the changing environments as well as for pathogenesis. Development of sexual stages is crucial for malaria transmission and relatively little is known about the role of specific gene products during asexual to sexual differentiation and further development. Therefore, in order to have a full understanding of the biology of the malaria parasite, gene regulation on a genome-wide global level must be understood, an area remaining to be elucidated in P. falciparum. Parasite features, such as A-T bias, difficulties in cloning, labor-intensive culture and purification of specific stages of the parasite, all contribute to the difficulties to investigate many aspects of parasite biology. However, despite these challenges, limited studies have revealed a number of parallelisms with eukaryotic transcription. For example, the parasite's genes are organised in a similar fashion, contain promoter elements and upstream activation sequences, as shown by structural searches and functional assays, and some of the basal machinery and general transcription factors have been found in Plasmodium. The completion of the full genome sequence of P. falciparum and other species of Plasmodium has resulted in the search for specific transcription factors through genome mining. Although genome mining may identify some of the factors, search for these factors solely by primary sequence homology would result in a non-comprehensive list for transcription factors present in the genome. Here, we present further discussion on putative transcription factors like activities detected in the asexual and sexual stages of P. falciparum.
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Affiliation(s)
- Nirbhay Kumar
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins Malaria Research Institute, Johns Hopkins University, 615 N. Wolfe Street, Baltimore, MD 21205, USA.
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Llinás M, DeRisi JL. Pernicious plans revealed: Plasmodium falciparum genome wide expression analysis. Curr Opin Microbiol 2004; 7:382-7. [PMID: 15358256 DOI: 10.1016/j.mib.2004.06.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The asexual intraerythrocytic developmental cycle (IDC) of Plasmodium falciparum is responsible for the majority of the clinical manifestations of malaria in humans. Although malaria has been studied for over a century, the elucidation of the full genome sequence of P. falciparum has now allowed for in-depth studies of gene expression throughout the entire intraerythrocytic stage. As the mainstays of anti-malarial chemotherapy become increasingly ineffective, we need a deeper understanding of fundamental plasmodial bioregulatory mechanisms to successfully subvert them. Recent gene expression studies have begun to examine different aspects of the IDC and are providing key insights into the basic mechanisms of Plasmodium gene regulation and are helping to define gene functions. However, to date, no transcription factor has been fully characterized from Plasmodium and the definitive identification of cis-acting regulatory elements along with their corresponding trans-acting partners is still lacking. The characterization of the transcriptome of P. falciparum is the first major step towards the understanding of the genome wide regulation of gene expression in this parasite. IDC expression data for almost every gene in the P. falciparum genome can now be publicly queried at and. The results of these studies suggest promising leads for identifying novel targets for anti-malarial therapeutics and vaccines in addition to providing a solid foundation for the ongoing elucidation of plasmodial gene expression.
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Affiliation(s)
- Manuel Llinás
- Department of Biochemistry and Biophysics, UC San Francisco, 600-16th Street, BOX 2240, San Francisco, California 94143-2240, USA.
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