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Abstract
Plasmodium falciparum, the human malaria parasite, infects two hosts and various cell types, inducing distinct morphological and physiological changes in the parasite in response to different environmental conditions. These variations required the parasite to adapt and develop elaborate molecular mechanisms to ensure its spread and transmission. Recent findings have significantly improved our understanding of the regulation of gene expression in P. falciparum. Here, we provide an up-to-date overview of technologies used to highlight the transcriptomic adjustments occurring in the parasite throughout its life cycle. We also emphasize the complementary and complex epigenetic mechanisms regulating gene expression in malaria parasites. This review concludes with an outlook on the chromatin architecture, the remodeling systems, and how this 3D genome organization is critical in various biological processes.
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Affiliation(s)
- Thomas Hollin
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, California, USA;
| | - Zeinab Chahine
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, California, USA;
| | - Karine G Le Roch
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, California, USA;
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2
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PfARID Regulates P. falciparum Malaria Parasite Male Gametogenesis and Female Fertility and Is Critical for Parasite Transmission to the Mosquito Vector. mBio 2022; 13:e0057822. [PMID: 35638735 PMCID: PMC9239086 DOI: 10.1128/mbio.00578-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sexual reproduction of Plasmodium falciparum parasites is critical to the spread of malaria in the human population. The factors that regulate gene expression underlying formation of fertilization-competent gametes, however, remain unknown. Here, we report that P. falciparum expresses a protein with an AT-rich interaction domain (ARID) which, in other organisms, is part of chromatin remodeling complexes. P. falciparum ARID (PfARID) localized to the parasite nucleus and is critical for the formation of male gametes and fertility of female gametes. PfARID gene deletion (Pfarid–) gametocytes showed downregulation of gene expression important for gametogenesis, antigenic variation, and cell signaling and for parasite development in the mosquito. Our study identifies PfARID as a critical nuclear protein involved in regulating the gene expression landscape of mature gametocytes. This establishes fertility and also prepares the parasite for postfertilization events that are essential for infection of the mosquito vector.
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Saxena H, Gupta A. P. falciparum PfRUVBL proteins binds at TARE region and var gene promoter located in subtelomeric region. Pathog Dis 2022; 80:6595874. [PMID: 35640888 DOI: 10.1093/femspd/ftac018] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 04/14/2022] [Accepted: 05/25/2022] [Indexed: 11/13/2022] Open
Abstract
In order to survive and establish infection, Plasmodium parasite employ various strategies to evade host immune response. Var genes family, a repertoire of 60 genes, express parasite-specific protein PfEMP1, a variable surface antigen, on the membrane of infected erythrocyte, and by continuously switching the variants of PfEMP1, helps the parasite to avoid detection and destruction by host immune system during intra-erythrocytic developmental cycle. Although chromatin modifications are recognized to be a prominent phenomenon in regulation of mono-allelic expression of these var genes, however the precise histone codes and molecular players & mechanisms guiding these modifications are yet to be unravelled in depth. In this study, we have functionally characterized RUVBL proteins of P. falciparum and shown that PfMYST (an essential lysine acetyl transferase) and PfRUVBL protein complex occupy the TARE region and var gene promoter in ring stage of the parasite. Further we have demonstrated that PfMYST/PfRUVBL complex interact with core histone, H3 & H4. Overall the findings of this study adds a layer by identifying the potential role of epigenetic regulators, PfMYST & PfRUVBL in regulation of monoallelic expression of var genes in malaria parasite.
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Affiliation(s)
- Himani Saxena
- Epigenetics and Human disease laboratory, Department of Life Sciences, Shiv Nadar University, Delhi-NCR, India
| | - Ashish Gupta
- Epigenetics and Human disease laboratory, Department of Life Sciences, Shiv Nadar University, Delhi-NCR, India
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Miao J, Wang C, Lucky AB, Liang X, Min H, Adapa SR, Jiang R, Kim K, Cui L. A unique GCN5 histone acetyltransferase complex controls erythrocyte invasion and virulence in the malaria parasite Plasmodium falciparum. PLoS Pathog 2021; 17:e1009351. [PMID: 34403450 PMCID: PMC8396726 DOI: 10.1371/journal.ppat.1009351] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 08/27/2021] [Accepted: 07/21/2021] [Indexed: 12/14/2022] Open
Abstract
The histone acetyltransferase GCN5-associated SAGA complex is evolutionarily conserved from yeast to human and functions as a general transcription co-activator in global gene regulation. In this study, we identified a divergent GCN5 complex in Plasmodium falciparum, which contains two plant homeodomain (PHD) proteins (PfPHD1 and PfPHD2) and a plant apetela2 (AP2)-domain transcription factor (PfAP2-LT). To dissect the functions of the PfGCN5 complex, we generated parasite lines with either the bromodomain in PfGCN5 or the PHD domain in PfPHD1 deleted. The two deletion mutants closely phenocopied each other, exhibiting significantly reduced merozoite invasion of erythrocytes and elevated sexual conversion. These domain deletions caused dramatic decreases not only in histone H3K9 acetylation but also in H3K4 trimethylation, indicating synergistic crosstalk between the two euchromatin marks. Domain deletion in either PfGCN5 or PfPHD1 profoundly disturbed the global transcription pattern, causing altered expression of more than 60% of the genes. At the schizont stage, these domain deletions were linked to specific down-regulation of merozoite genes involved in erythrocyte invasion, many of which contain the AP2-LT binding motif and are also regulated by AP2-I and BDP1, suggesting targeted recruitment of the PfGCN5 complex to the invasion genes by these specific factors. Conversely, at the ring stage, PfGCN5 or PfPHD1 domain deletions disrupted the mutually exclusive expression pattern of the entire var gene family, which encodes the virulent factor PfEMP1. Correlation analysis between the chromatin state and alteration of gene expression demonstrated that up- and down-regulated genes in these mutants are highly correlated with the silent and active chromatin states in the wild-type parasite, respectively. Collectively, the PfGCN5 complex represents a novel HAT complex with a unique subunit composition including an AP2 transcription factor, which signifies a new paradigm for targeting the co-activator complex to regulate general and parasite-specific cellular processes in this low-branching parasitic protist. Epigenetic regulation of gene expression plays essential roles in orchestrating the general and parasite-specific cellular pathways in the malaria parasite Plasmodium falciparum. To better understand the epigenetic mechanisms in this parasite, we characterized the histone acetyltransferase GCN5-mediated transcription regulation during intraerythrocytic development of the parasite. Using tandem affinity purification and proteomic characterization, we identified that the PfGCN5-associated complex contains nine core components, including two PHD domain proteins (PfPHD1 and PfPHD2) and an AP2-domain transcription factor, which is divergent from the canonical GCN5 complexes evolutionarily conserved from yeast to human. To understand the functions of the PfGCN5 complex, we performed domain deletions in two subunits of this complex, PfGCN5 and PfPHD1. We found that the two deletion mutants displayed very similar growth phenotypes, including significantly reduced merozoite invasion rates and elevated sexual conversion. These two mutants were associated with dramatic decreases in histone H3K9 acetylation and H3K4 trimethylation, which led to global changes in chromatin states and gene expression. Consistent with the phenotypes, genes significantly affected by the PfGCN5 and PfPHD1 gene disruption include those participating in parasite-specific pathways such as invasion, virulence, and sexual development. In conclusion, this study presents a new model of the PfGCN5 complex for targeting the co-activator complex to regulate general and parasite-specific cellular processes in this low-branching parasitic protist.
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Affiliation(s)
- Jun Miao
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
- * E-mail: (JM); (LC)
| | - Chengqi Wang
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Amuza Byaruhanga Lucky
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Xiaoying Liang
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Hui Min
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Swamy Rakesh Adapa
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Rays Jiang
- Center for Global Health and Infectious Diseases Research, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Kami Kim
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
| | - Liwang Cui
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States of America
- * E-mail: (JM); (LC)
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5
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Peculiarities of Plasmodium falciparum Gene Regulation and Chromatin Structure. Int J Mol Sci 2021; 22:ijms22105168. [PMID: 34068393 PMCID: PMC8153576 DOI: 10.3390/ijms22105168] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 05/10/2021] [Accepted: 05/10/2021] [Indexed: 12/14/2022] Open
Abstract
The highly complex life cycle of the human malaria parasite, Plasmodium falciparum, is based on an orchestrated and tightly regulated gene expression program. In general, eukaryotic transcription regulation is determined by a combination of sequence-specific transcription factors binding to regulatory DNA elements and the packaging of DNA into chromatin as an additional layer. The accessibility of regulatory DNA elements is controlled by the nucleosome occupancy and changes of their positions by an active process called nucleosome remodeling. These epigenetic mechanisms are poorly explored in P. falciparum. The parasite genome is characterized by an extraordinarily high AT-content and the distinct architecture of functional elements, and chromatin-related proteins also exhibit high sequence divergence compared to other eukaryotes. Together with the distinct biochemical properties of nucleosomes, these features suggest substantial differences in chromatin-dependent regulation. Here, we highlight the peculiarities of epigenetic mechanisms in P. falciparum, addressing chromatin structure and dynamics with respect to their impact on transcriptional control. We focus on the specialized chromatin remodeling enzymes and discuss their essential function in P. falciparum gene regulation.
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6
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Hollin T, Le Roch KG. From Genes to Transcripts, a Tightly Regulated Journey in Plasmodium. Front Cell Infect Microbiol 2020; 10:618454. [PMID: 33425787 PMCID: PMC7793691 DOI: 10.3389/fcimb.2020.618454] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 11/19/2020] [Indexed: 12/17/2022] Open
Abstract
Over the past decade, we have witnessed significant progresses in understanding gene regulation in Apicomplexa including the human malaria parasite, Plasmodium falciparum. This parasite possesses the ability to convert in multiple stages in various hosts, cell types, and environments. Recent findings indicate that P. falciparum is talented at using efficient and complementary molecular mechanisms to ensure a tight control of gene expression at each stage of its life cycle. Here, we review the current understanding on the contribution of the epigenome, atypical transcription factors, and chromatin organization to regulate stage conversion in P. falciparum. The adjustment of these regulatory mechanisms occurring during the progression of the life cycle will be extensively discussed.
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Affiliation(s)
- Thomas Hollin
- Department of Molecular, Cell and Systems Biology, University of California Riverside, CA, United States
| | - Karine G Le Roch
- Department of Molecular, Cell and Systems Biology, University of California Riverside, CA, United States
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7
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Tang J, Chisholm SA, Yeoh LM, Gilson PR, Papenfuss AT, Day KP, Petter M, Duffy MF. Histone modifications associated with gene expression and genome accessibility are dynamically enriched at Plasmodium falciparum regulatory sequences. Epigenetics Chromatin 2020; 13:50. [PMID: 33225957 PMCID: PMC7682024 DOI: 10.1186/s13072-020-00365-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 09/29/2020] [Indexed: 12/15/2022] Open
Abstract
Background The malaria parasite Plasmodium falciparum has an unusually euchromatic genome with poorly conserved positioning of nucleosomes in intergenic sequences and poorly understood mechanisms of gene regulation. Variant histones and histone modifications determine nucleosome stability and recruit trans factors, but their combinatorial contribution to gene regulation is unclear. Results Here, we show that the histone H3 acetylations H3K18ac and H3K27ac and the variant histone Pf H2A.Z are enriched together at regulatory sites upstream of genes. H3K18ac and H3K27ac together dynamically mark regulatory regions of genes expressed during the asexual life cycle. In contrast, H3K4me1 is depleted in intergenic sequence and dynamically depleted upstream of expressed genes. The temporal pattern of H3K27ac and H3K18ac enrichment indicates that they accumulate during S phase and mitosis and are retained at regulatory sequences until at least G1 phase and after cessation of expression of the cognate genes. We integrated our ChIPseq data with existing datasets to show that in schizont stages H3K18ac, H3K27ac and Pf H2A.Z colocalise with the transcription factor PfAP2-I and the bromodomain protein PfBDP1 and are enriched at stably positioned nucleosomes within regions of exposed DNA at active transcriptional start sites. Using transient transfections we showed that sequences enriched with colocalised H3K18ac, H3K27ac and Pf H2A.Z possess promoter activity in schizont stages, but no enhancer-like activity. Conclusions The dynamic H3 acetylations define P. falciparum regulatory sequences and contribute to gene activation. These findings expand the knowledge of the chromatin landscape that regulates gene expression in P. falciparum.
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Affiliation(s)
- Jingyi Tang
- Department of Medicine, The University of Melbourne, Royal Melbourne Hospital, Parkville, VIC, 3050, Australia.,School of Medicine, Faculty of Health, Deakin University, Geelong Waurn Ponds Campus, Waurn Ponds, VIC, 3216, Australia
| | - Scott A Chisholm
- School of BioSciences, The University of Melbourne, Parkville, VIC, 3052, Australia.,Bio21 Institute, Parkville, VIC, 3052, Australia
| | - Lee M Yeoh
- Bio21 Institute, Parkville, VIC, 3052, Australia.,Peter Doherty Institute, Melbourne, VIC, 3000, Australia.,Department of Microbiology and Immunology, The University of Melbourne, Victoria, 3000, Australia
| | - Paul R Gilson
- Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, VIC, 3004, Australia.,Monash University, Melbourne, VIC, 3800, Australia
| | - Anthony T Papenfuss
- Bioinformatics Division, Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia.,Department of Mathematics and Statistics, University of Melbourne, Victoria, Australia.,Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia.,Sir Peter MacCallum, Department of Oncology, University of Melbourne, Parkville, VIC, Australia
| | - Karen P Day
- Bio21 Institute, Parkville, VIC, 3052, Australia.,Peter Doherty Institute, Melbourne, VIC, 3000, Australia.,Department of Microbiology and Immunology, The University of Melbourne, Victoria, 3000, Australia
| | - Michaela Petter
- Department of Medicine, The University of Melbourne, Royal Melbourne Hospital, Parkville, VIC, 3050, Australia.,Erlangen University, 91054, Erlangen, Germany
| | - Michael F Duffy
- Department of Medicine, The University of Melbourne, Royal Melbourne Hospital, Parkville, VIC, 3050, Australia. .,Bio21 Institute, Parkville, VIC, 3052, Australia. .,Peter Doherty Institute, Melbourne, VIC, 3000, Australia. .,Department of Microbiology and Immunology, The University of Melbourne, Victoria, 3000, Australia.
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8
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Dynamic Chromatin Structure and Epigenetics Control the Fate of Malaria Parasites. Trends Genet 2020; 37:73-85. [PMID: 32988634 DOI: 10.1016/j.tig.2020.09.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 08/27/2020] [Accepted: 09/02/2020] [Indexed: 12/11/2022]
Abstract
Multiple hosts and various life cycle stages prompt the human malaria parasite, Plasmodium falciparum, to acquire sophisticated molecular mechanisms to ensure its survival, spread, and transmission to its next host. To face these environmental challenges, increasing evidence suggests that the parasite has developed complex and complementary layers of regulatory mechanisms controlling gene expression. Here, we discuss the recent developments in the discovery of molecular components that contribute to cell replication and differentiation and highlight the major contributions of epigenetics, transcription factors, and nuclear architecture in controlling gene regulation and life cycle progression in Plasmodium spp.
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9
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Abel S, Le Roch KG. The role of epigenetics and chromatin structure in transcriptional regulation in malaria parasites. Brief Funct Genomics 2020; 18:302-313. [PMID: 31220857 DOI: 10.1093/bfgp/elz005] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 02/25/2019] [Accepted: 03/14/2019] [Indexed: 12/28/2022] Open
Abstract
Due to the unique selective pressures and extreme changes faced by the human malaria parasite Plasmodium falciparum throughout its life cycle, the parasite has evolved distinct features to alter its gene expression patterns. Along with classical gene regulation by transcription factors (TFs), of which only one family, the AP2 TFs, has been described in the parasite genome, a large body of evidence points toward chromatin structure and epigenetic factors mediating the changes in gene expression associated with parasite life cycle stages. These attributes may be critically important for immune evasion, host cell invasion and development of the parasite in its two hosts, the human and the Anopheles vector. Thus, the factors involved in the maintenance and regulation of chromatin and epigenetic features represent potential targets for antimalarial drugs. In this review, we discuss the mechanisms in P. falciparum that regulate chromatin structure, nucleosome landscape, the 3-dimensional structure of the genome and additional distinctive features created by parasite-specific genes and gene families. We review conserved traits of chromatin in eukaryotes in order to highlight what is unique in the parasite.
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Affiliation(s)
- Steven Abel
- Department of Molecular, Cell and Systems Biology, University of California Riverside, Riverside, CA, USA
| | - Karine G Le Roch
- Department of Molecular, Cell and Systems Biology, University of California Riverside, Riverside, CA, USA
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10
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Batugedara G, Le Roch KG. Unraveling the 3D genome of human malaria parasites. Semin Cell Dev Biol 2018; 90:144-153. [PMID: 30009946 DOI: 10.1016/j.semcdb.2018.07.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 07/03/2018] [Indexed: 01/31/2023]
Abstract
The chromosomes within the eukaryotic cell nucleus are highly dynamic and adopt complex hierarchical structures. Understanding how this three-dimensional (3D) nuclear architectureaffects gene regulation, cell cycle progression and disease pathogenesis are important biological questions in development and disease. Recently, many genome-wide technologies including chromosome conformation capture (3C) and 3C-based methodologies (4C, 5C, and Hi-C) have been developed to investigate 3D chromatin structure. In this review, we introduce 3D genome methodologies, with a focus on their application for understanding the nuclear architecture of the human malaria parasite, Plasmodium falciparum. An increasing amount of evidence now suggests that gene regulation in the parasite is largely regulated by epigenetic mechanisms and nuclear reorganization. Here, we explore the 3D genome architecture of P. falciparum, including local and global chromatin structure. In addition, molecular components important for maintaining 3D chromatin organization including architectural proteins and long non-coding RNAs are discussed. Collectively, these studies contribute to our understanding of how the plasticity of 3D genome architecture regulates gene expression and cell cycle progression in this deadly parasite.
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Affiliation(s)
- Gayani Batugedara
- Department of Molecular, Cell and Systems Biology, University of California Riverside, Riverside, CA 92521, USA
| | - Karine G Le Roch
- Department of Molecular, Cell and Systems Biology, University of California Riverside, Riverside, CA 92521, USA.
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11
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Otto TD, Böhme U, Sanders M, Reid A, Bruske EI, Duffy CW, Bull PC, Pearson RD, Abdi A, Dimonte S, Stewart LB, Campino S, Kekre M, Hamilton WL, Claessens A, Volkman SK, Ndiaye D, Amambua-Ngwa A, Diakite M, Fairhurst RM, Conway DJ, Franck M, Newbold CI, Berriman M. Long read assemblies of geographically dispersed Plasmodium falciparum isolates reveal highly structured subtelomeres. Wellcome Open Res 2018; 3:52. [PMID: 29862326 PMCID: PMC5964635 DOI: 10.12688/wellcomeopenres.14571.1] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/27/2018] [Indexed: 12/30/2022] Open
Abstract
Background: Although thousands of clinical isolates of
Plasmodium falciparum are being sequenced and analysed by short read technology, the data do not resolve the highly variable subtelomeric regions of the genomes that contain polymorphic gene families involved in immune evasion and pathogenesis. There is also no current standard definition of the boundaries of these variable subtelomeric regions. Methods: Using long-read sequence data (Pacific Biosciences SMRT technology), we assembled and annotated the genomes of 15
P. falciparum isolates, ten of which are newly cultured clinical isolates. We performed comparative analysis of the entire genome with particular emphasis on the subtelomeric regions and the internal
var genes clusters.
Results: The nearly complete sequence of these 15 isolates has enabled us to define a highly conserved core genome, to delineate the boundaries of the subtelomeric regions, and to compare these across isolates. We found highly structured variable regions in the genome. Some exported gene families purportedly involved in release of merozoites show copy number variation. As an example of ongoing genome evolution, we found a novel CLAG gene in six isolates. We also found a novel gene that was relatively enriched in the South East Asian isolates compared to those from Africa. Conclusions: These 15 manually curated new reference genome sequences with their nearly complete subtelomeric regions and fully assembled genes are an important new resource for the malaria research community. We report the overall conserved structure and pattern of important gene families and the more clearly defined subtelomeric regions.
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Affiliation(s)
- Thomas D Otto
- Wellcome Sanger Institute, Hinxton, UK.,Centre of Immunobiology, Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | | | | | - Adam Reid
- Wellcome Sanger Institute, Hinxton, UK
| | - Ellen I Bruske
- Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany
| | - Craig W Duffy
- London School of Hygiene and Tropical Medicine, London, UK
| | - Pete C Bull
- Department of Pathology, University of Cambridge, Cambridge, UK
| | - Richard D Pearson
- Wellcome Sanger Institute, Hinxton, UK.,Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, Oxford, UK
| | | | - Sandra Dimonte
- Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany
| | | | - Susana Campino
- Wellcome Sanger Institute, Hinxton, UK.,London School of Hygiene and Tropical Medicine, London, UK
| | | | | | | | - Sarah K Volkman
- Harvard T.H. Chan School of Public Health, Boston, MA, USA.,The Broad Institute of MIT and Harvard, Cambridge, MA, USA.,Simmons College, Boston, MA, USA
| | - Daouda Ndiaye
- Faculty of Medicine and Pharmacy, Université Cheikh Anta Diop, Dakar, Senegal
| | | | - Mahamadou Diakite
- Malaria Research and Training Center, University of Bamako, Bamako, Mali
| | - Rick M Fairhurst
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA
| | - David J Conway
- London School of Hygiene and Tropical Medicine, London, UK
| | - Matthias Franck
- Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany
| | - Chris I Newbold
- Wellcome Sanger Institute, Hinxton, UK.,Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
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12
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Ubhe S, Rawat M, Verma S, Anamika K, Karmodiya K. Genome-wide identification of novel intergenic enhancer-like elements: implications in the regulation of transcription in Plasmodium falciparum. BMC Genomics 2017; 18:656. [PMID: 28836940 PMCID: PMC5569477 DOI: 10.1186/s12864-017-4052-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 08/11/2017] [Indexed: 01/28/2023] Open
Abstract
Background The molecular mechanisms of transcriptional regulation are poorly understood in Plasmodium falciparum. In addition, most of the genes in Plasmodium falciparum are transcriptionally poised and only a handful of cis-regulatory elements are known to operate in transcriptional regulation. Here, we employed an epigenetic signature based approach to identify significance of previously uncharacterised intergenic regions enriched with histone modification marks leading to discovery of enhancer-like elements. Results We found that enhancer-like elements are significantly enriched with H3K4me1, generate unique non-coding bi-directional RNAs and majority of them can function as cis-regulators. Furthermore, functional enhancer reporter assay demonstrates that the enhancer-like elements regulate transcription of target genes in Plasmodium falciparum. Our study also suggests that the Plasmodium genome segregates functionally related genes into discrete housekeeping and pathogenicity/virulence clusters, presumably for robust transcriptional control of virulence/pathogenicity genes. Conclusions This report contributes to the understanding of parasite regulatory genomics by identification of enhancer-like elements, defining their epigenetic and transcriptional features and provides a resource of functional cis-regulatory elements that may give insights into the virulence/pathogenicity of Plasmodium falciparum. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-4052-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Suyog Ubhe
- Department of Biology, Indian Institute of Science Education and Research, Pashan, Pune, 411008, India
| | - Mukul Rawat
- Department of Biology, Indian Institute of Science Education and Research, Pashan, Pune, 411008, India
| | - Srikant Verma
- Labs, Persistent Systems Limited, Pingala - Aryabhata, Erandwane, Pune, 411004, India
| | - Krishanpal Anamika
- Labs, Persistent Systems Limited, Pingala - Aryabhata, Erandwane, Pune, 411004, India
| | - Krishanpal Karmodiya
- Department of Biology, Indian Institute of Science Education and Research, Pashan, Pune, 411008, India.
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13
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Gupta AP, Zhu L, Tripathi J, Kucharski M, Patra A, Bozdech Z. Histone 4 lysine 8 acetylation regulates proliferation and host-pathogen interaction in Plasmodium falciparum. Epigenetics Chromatin 2017; 10:40. [PMID: 28830512 PMCID: PMC5568195 DOI: 10.1186/s13072-017-0147-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 08/07/2017] [Indexed: 01/09/2023] Open
Abstract
Background The dynamics of histone modifications in Plasmodium falciparum indicates the existence of unique mechanisms that link epigenetic factors with transcription. Here, we studied the impact of acetylated histone code on transcriptional regulation during the intraerythrocytic developmental cycle (IDC) of P. falciparum. Results Using a dominant-negative transgenic approach, we showed that acetylations of histone H4 play a direct role in transcription. Specifically, these histone modifications mediate an inverse transcriptional relationship between the factors of cell proliferation and host–parasite interaction. Out of the four H4 acetylations, H4K8ac is likely the rate-limiting, regulatory step, which modulates the overall dynamics of H4 posttranslational modifications. H4K8ac exhibits maximum responsiveness to HDAC inhibitors and has a highly dynamic distribution pattern along the genome of P. falciparum during the IDC. Moreover, H4K8ac functions mainly in the euchromatin where its occupancy shifts from intergenic regions located upstream of 5′ end of open reading frame into the protein coding regions. This shift is directly or indirectly associated with transcriptional activities at the corresponding genes. H4K8ac is also active in the heterochromatin where it stimulates expression of the main antigenic gene family (var) by its presence in the promoter region. Conclusions Overall, we demonstrate that H4K8ac is a potential major regulator of chromatin-linked transcriptional changes during P. falciparum life cycle which is associated not only with euchromatin but also with heterochromatin environment. This is potentially a highly significant finding that suggests a regulatory connection between growth and parasite–host interaction both of which play a major role in malaria parasite virulence. Electronic supplementary material The online version of this article (doi:10.1186/s13072-017-0147-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Archana P Gupta
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Lei Zhu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Jaishree Tripathi
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Michal Kucharski
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Alok Patra
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore
| | - Zbynek Bozdech
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.
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14
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Abstract
Malaria is a significant threat throughout the developing world. Among the most fascinating aspects of the protozoan parasites responsible for this disease are the methods they employ to avoid the immune system and perpetuate chronic infections. Key among these is antigenic variation: By systematically altering antigens that are displayed to the host's immune system, the parasite renders the adaptive immune response ineffective. For Plasmodium falciparum, the species responsible for the most severe form of human malaria, this process involves a complicated molecular mechanism that results in continuously changing patterns of variant-antigen-encoding gene expression. Although many features of this process remain obscure, significant progress has been made in recent years to decipher various molecular aspects of the regulatory cascade that causes chronic infection.
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Affiliation(s)
- Kirk W Deitsch
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10065;
| | - Ron Dzikowski
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada and Kuvin Center for the Study of Infectious and Tropical Diseases, Hebrew University Hadassah Medical School, Jerusalem 91120, Israel;
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15
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Batugedara G, Lu XM, Bunnik EM, Le Roch KG. The Role of Chromatin Structure in Gene Regulation of the Human Malaria Parasite. Trends Parasitol 2017; 33:364-377. [PMID: 28065669 PMCID: PMC5410391 DOI: 10.1016/j.pt.2016.12.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 11/28/2016] [Accepted: 12/07/2016] [Indexed: 12/11/2022]
Abstract
The human malaria parasite, Plasmodium falciparum, depends on a coordinated regulation of gene expression for development and propagation within the human host. Recent developments suggest that gene regulation in the parasite is largely controlled by epigenetic mechanisms. Here, we discuss recent advancements contributing to our understanding of the mechanisms controlling gene regulation in the parasite, including nucleosome landscape, histone modifications, and nuclear architecture. In addition, various processes involved in regulation of parasite-specific genes and gene families are examined. Finally, we address the use of epigenetic processes as targets for novel antimalarial therapies. Collectively, these topics highlight the unique biology of P. falciparum, and contribute to our understanding of mechanisms regulating gene expression in this deadly parasite.
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Affiliation(s)
- Gayani Batugedara
- Department of Cell Biology and Neuroscience, University of California Riverside, Riverside, CA 92521, USA
| | - Xueqing M Lu
- Department of Cell Biology and Neuroscience, University of California Riverside, Riverside, CA 92521, USA
| | - Evelien M Bunnik
- Department of Microbiology, Immunology & Molecular Genetics, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Karine G Le Roch
- Department of Cell Biology and Neuroscience, University of California Riverside, Riverside, CA 92521, USA.
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16
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Gupta AP, Bozdech Z. Epigenetic landscapes underlining global patterns of gene expression in the human malaria parasite, Plasmodium falciparum. Int J Parasitol 2017; 47:399-407. [PMID: 28414071 DOI: 10.1016/j.ijpara.2016.10.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 10/15/2016] [Accepted: 10/20/2016] [Indexed: 12/31/2022]
Abstract
The dynamic chromatin landscape displaying combinatorial complexity of the epigenome impacts gene expression that underlies many events of differentiation and cell cycle progression. In the past few years, epigenetic mechanisms have emerged as important processes involved in the tight gene regulation in malaria parasites, Plasmodium spp. Focusing predominantly on Plasmodium falciparum, the species associated with the most severe form of the disease, many advances have been made in our understanding of the interaction between transcriptional regulation and epigenetic mechanisms as the pivotal processes in regulating life cycle progression, host parasite interactions and parasite adaptation to the host environment. This review focuses on the epigenome and its effect on transcriptional regulation in P. falciparum, highlighting its unique, evolutionary diverse features.
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Affiliation(s)
- Archana P Gupta
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Zbynek Bozdech
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
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17
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Plasmodium falciparum Nucleosomes Exhibit Reduced Stability and Lost Sequence Dependent Nucleosome Positioning. PLoS Pathog 2016; 12:e1006080. [PMID: 28033404 PMCID: PMC5198986 DOI: 10.1371/journal.ppat.1006080] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 11/19/2016] [Indexed: 11/19/2022] Open
Abstract
The packaging and organization of genomic DNA into chromatin represents an additional regulatory layer of gene expression, with specific nucleosome positions that restrict the accessibility of regulatory DNA elements. The mechanisms that position nucleosomes in vivo are thought to depend on the biophysical properties of the histones, sequence patterns, like phased di-nucleotide repeats and the architecture of the histone octamer that folds DNA in 1.65 tight turns. Comparative studies of human and P. falciparum histones reveal that the latter have a strongly reduced ability to recognize internal sequence dependent nucleosome positioning signals. In contrast, the nucleosomes are positioned by AT-repeat sequences flanking nucleosomes in vivo and in vitro. Further, the strong sequence variations in the plasmodium histones, compared to other mammalian histones, do not present adaptations to its AT-rich genome. Human and parasite histones bind with higher affinity to GC-rich DNA and with lower affinity to AT-rich DNA. However, the plasmodium nucleosomes are overall less stable, with increased temperature induced mobility, decreased salt stability of the histones H2A and H2B and considerable reduced binding affinity to GC-rich DNA, as compared with the human nucleosomes. In addition, we show that plasmodium histone octamers form the shortest known nucleosome repeat length (155bp) in vitro and in vivo. Our data suggest that the biochemical properties of the parasite histones are distinct from the typical characteristics of other eukaryotic histones and these properties reflect the increased accessibility of the P. falciparum genome. Nucleosomes are not positioned randomly on DNA but on preferential sites with respect to the underlying DNA sequence. Histones belong to the most conserved eukaryotic proteins, as sequence dependent nucleosome positioning is an essential regulatory feature of nucleosomes, determining the accessibility of regulatory factors to DNA. We determined the biochemical properties of plasmodium histones and show that they are distinct from human forms, explaining the accessible chromatin structure of P. falciparum. Amino acid exchanges in the histones do not present an adaption to the AT-rich genome, but rather reduce the binding affinity to GC-rich DNA sequences, resulting in rather unstable nucleosomes with labile H2A and H2B, requiring extra-nucleosomal positioning signals to keep them on place. Plasmodium chromatin exhibits the shortest nucleosome spacing known to date potentially inhibiting the formation of higher order structures and maintaining chromatin accessible.
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18
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The nuclear envelope and gene organization in parasitic protozoa: Specializations associated with disease. Mol Biochem Parasitol 2016; 209:104-113. [PMID: 27475118 DOI: 10.1016/j.molbiopara.2016.07.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 07/12/2016] [Accepted: 07/26/2016] [Indexed: 12/11/2022]
Abstract
The parasitic protozoa Trypanosoma brucei and Plasmodium falciparum are lethal human parasites that have developed elegant strategies of immune evasion by antigenic variation. Despite the vast evolutionary distance between the two taxa, both parasites employ strict monoallelic expression of their membrane proteins, variant surface glycoproteins in Trypanosomes and the var, rif and stevor genes in Plasmodium, in order to evade their host's immune system. Additionally, both telomeric location and epigenetic controls are prominent features of these membrane proteins. As such, telomeres, chromatin structure and nuclear organization all contribute to control of gene expression and immune evasion. Here, we discuss the importance of epigenetics and sub-nuclear context for the survival of these disease-causing parasites.
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19
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Saraf A, Cervantes S, Bunnik EM, Ponts N, Sardiu ME, Chung DWD, Prudhomme J, Varberg JM, Wen Z, Washburn MP, Florens L, Le Roch KG. Dynamic and Combinatorial Landscape of Histone Modifications during the Intraerythrocytic Developmental Cycle of the Malaria Parasite. J Proteome Res 2016; 15:2787-801. [PMID: 27291344 DOI: 10.1021/acs.jproteome.6b00366] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A major obstacle in understanding the complex biology of the malaria parasite remains to discover how gene transcription is controlled during its life cycle. Accumulating evidence indicates that the parasite's epigenetic state plays a fundamental role in gene expression and virulence. Using a comprehensive and quantitative mass spectrometry approach, we determined the global and dynamic abundance of histones and their covalent post-transcriptional modifications throughout the intraerythrocytic developmental cycle of Plasmodium falciparum. We detected a total of 232 distinct modifications, of which 160 had never been detected in Plasmodium and 88 had never been identified in any other species. We further validated over 10% of the detected modifications and their expression patterns by multiple reaction monitoring assays. In addition, we uncovered an unusual chromatin organization with parasite-specific histone modifications and combinatorial dynamics that may be directly related to transcriptional activity, DNA replication, and cell cycle progression. Overall, our data suggest that the malaria parasite has a unique histone modification signature that correlates with parasite virulence.
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Affiliation(s)
- Anita Saraf
- Stowers Institute for Medical Research , 1000 E. 50th Street, Kansas City, Missouri 64110, United States
| | - Serena Cervantes
- Department of Cell Biology and Neuroscience, University of California , 900 University Avenue, Riverside, California 92521, United States
| | - Evelien M Bunnik
- Department of Cell Biology and Neuroscience, University of California , 900 University Avenue, Riverside, California 92521, United States
| | - Nadia Ponts
- Department of Cell Biology and Neuroscience, University of California , 900 University Avenue, Riverside, California 92521, United States
| | - Mihaela E Sardiu
- Stowers Institute for Medical Research , 1000 E. 50th Street, Kansas City, Missouri 64110, United States
| | - Duk-Won D Chung
- Department of Cell Biology and Neuroscience, University of California , 900 University Avenue, Riverside, California 92521, United States
| | - Jacques Prudhomme
- Department of Cell Biology and Neuroscience, University of California , 900 University Avenue, Riverside, California 92521, United States
| | - Joseph M Varberg
- Stowers Institute for Medical Research , 1000 E. 50th Street, Kansas City, Missouri 64110, United States
| | - Zhihui Wen
- Stowers Institute for Medical Research , 1000 E. 50th Street, Kansas City, Missouri 64110, United States
| | - Michael P Washburn
- Stowers Institute for Medical Research , 1000 E. 50th Street, Kansas City, Missouri 64110, United States.,Department of Pathology and Laboratory Medicine, University of Kansas Medical Center , 3901 Rainbow Boulevard, Kansas City, Kansas 66160, United States
| | - Laurence Florens
- Stowers Institute for Medical Research , 1000 E. 50th Street, Kansas City, Missouri 64110, United States
| | - Karine G Le Roch
- Department of Cell Biology and Neuroscience, University of California , 900 University Avenue, Riverside, California 92521, United States
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20
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Kensche PR, Hoeijmakers WAM, Toenhake CG, Bras M, Chappell L, Berriman M, Bártfai R. The nucleosome landscape of Plasmodium falciparum reveals chromatin architecture and dynamics of regulatory sequences. Nucleic Acids Res 2015; 44:2110-24. [PMID: 26578577 PMCID: PMC4797266 DOI: 10.1093/nar/gkv1214] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 10/28/2015] [Indexed: 11/13/2022] Open
Abstract
In eukaryotes, the chromatin architecture has a pivotal role in regulating all DNA-associated processes and it is central to the control of gene expression. For Plasmodium falciparum, a causative agent of human malaria, the nucleosome positioning profile of regulatory regions deserves particular attention because of their extreme AT-content. With the aid of a highly controlled MNase-seq procedure we reveal how positioning of nucleosomes provides a structural and regulatory framework to the transcriptional unit by demarcating landmark sites (transcription/translation start and end sites). In addition, our analysis provides strong indications for the function of positioned nucleosomes in splice site recognition. Transcription start sites (TSSs) are bordered by a small nucleosome-depleted region, but lack the stereotypic downstream nucleosome arrays, highlighting a key difference in chromatin organization compared to model organisms. Furthermore, we observe transcription-coupled eviction of nucleosomes on strong TSSs during intraerythrocytic development and demonstrate that nucleosome positioning and dynamics can be predictive for the functionality of regulatory DNA elements. Collectively, the strong nucleosome positioning over splice sites and surrounding putative transcription factor binding sites highlights the regulatory capacity of the nucleosome landscape in this deadly human pathogen.
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Affiliation(s)
- Philip Reiner Kensche
- Department of Molecular Biology, Radboud University, 6525GA Nijmegen, The Netherlands
| | | | | | - Maaike Bras
- Department of Molecular Biology, Radboud University, 6525GA Nijmegen, The Netherlands
| | - Lia Chappell
- Parasite Genomics Group, Wellcome Trust Sanger Institute, CB10 1SA Hinxton, UK
| | - Matthew Berriman
- Parasite Genomics Group, Wellcome Trust Sanger Institute, CB10 1SA Hinxton, UK
| | - Richárd Bártfai
- Department of Molecular Biology, Radboud University, 6525GA Nijmegen, The Netherlands
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21
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Koster M, Snel B, Timmers H. Genesis of Chromatin and Transcription Dynamics in the Origin of Species. Cell 2015; 161:724-36. [DOI: 10.1016/j.cell.2015.04.033] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Indexed: 11/15/2022]
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22
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Russell K, Emes R, Horrocks P. Triaging informative cis-regulatory elements for the combinatorial control of temporal gene expression during Plasmodium falciparum intraerythrocytic development. Parasit Vectors 2015; 8:81. [PMID: 25652008 PMCID: PMC4322800 DOI: 10.1186/s13071-015-0701-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 01/27/2015] [Indexed: 01/18/2023] Open
Abstract
Background Over 2700 genes are subject to stage-specific regulation during the intraerythrocytic development of the human malaria parasite Plasmodium falciparum. Bioinformatic analyses have identified a large number of over-represented motifs in the 5′ flanking regions of these genes that may act as cis-acting factors in the promoter-based control of temporal expression. Triaging these lists to provide candidates most likely to play a role in regulating temporal expression is challenging, but important if we are to effectively design in vitro studies to validate this role. Methods We report here the application of a repeated search of variations of 5′ flanking sequences from P. falciparum using the Finding Informative Regulatory Elements (FIRE) algorithm. Results Our approach repeatedly found a short-list of high scoring DNA motifs, for which cognate specific transcription factors were available, that appear to be typically associated with upregulation of mRNA accumulation during the first half of intraerythrocytic development. Conclusions We propose these cis-trans interactions may provide a combinatorial promoter-based control of gene expression to complement more global mechanisms of gene regulation that can account for temporal control during the second half of intraerythrocytic development. Electronic supplementary material The online version of this article (doi:10.1186/s13071-015-0701-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Karen Russell
- Institute for Science and Technology in Medicine, Keele University, Staffordshire, ST5 5BG, UK.
| | - Richard Emes
- School of Veterinary Medicine and Science, University of Nottingham, Leicestershire, LE12 5RD, UK. .,Advanced Data Analysis Centre, University of Nottingham, Leicestershire, LE12 5RD, UK.
| | - Paul Horrocks
- Institute for Science and Technology in Medicine, Keele University, Staffordshire, ST5 5BG, UK.
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23
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Ay F, Bunnik EM, Varoquaux N, Vert JP, Noble WS, Le Roch KG. Multiple dimensions of epigenetic gene regulation in the malaria parasite Plasmodium falciparum: gene regulation via histone modifications, nucleosome positioning and nuclear architecture in P. falciparum. Bioessays 2014; 37:182-94. [PMID: 25394267 DOI: 10.1002/bies.201400145] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Plasmodium falciparum is the most deadly human malarial parasite, responsible for an estimated 207 million cases of disease and 627,000 deaths in 2012. Recent studies reveal that the parasite actively regulates a large fraction of its genes throughout its replicative cycle inside human red blood cells and that epigenetics plays an important role in this precise gene regulation. Here, we discuss recent advances in our understanding of three aspects of epigenetic regulation in P. falciparum: changes in histone modifications, nucleosome occupancy and the three-dimensional genome structure. We compare these three aspects of the P. falciparum epigenome to those of other eukaryotes, and show that large-scale compartmentalization is particularly important in determining histone decomposition and gene regulation in P. falciparum. We conclude by presenting a gene regulation model for P. falciparum that combines the described epigenetic factors, and by discussing the implications of this model for the future of malaria research.
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Affiliation(s)
- Ferhat Ay
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
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24
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Seridi L, Ryu T, Ravasi T. Dynamic epigenetic control of highly conserved noncoding elements. PLoS One 2014; 9:e109326. [PMID: 25289637 PMCID: PMC4188601 DOI: 10.1371/journal.pone.0109326] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Accepted: 09/11/2014] [Indexed: 11/19/2022] Open
Abstract
Background Many noncoding genomic loci have remained constant over long evolutionary periods, suggesting that they are exposed to strong selective pressures. The molecular functions of these elements have been partially elucidated, but the fundamental reason for their extreme conservation is still unknown. Results To gain new insights into the extreme selection of highly conserved noncoding elements (HCNEs), we used a systematic analysis of multi-omic data to study the epigenetic regulation of such elements during the development of Drosophila melanogaster. At the sequence level, HCNEs are GC-rich and have a characteristic oligomeric composition. They have higher levels of stable nucleosome occupancy than their flanking regions, and lower levels of mononucleosomes and H3.3, suggesting that these regions reside in compact chromatin. Furthermore, these regions showed remarkable modulations in histone modification and the expression levels of adjacent genes during development. Although HCNEs are primarily initiated late in replication, about 10% were related to early replication origins. Finally, HCNEs showed strong enrichment within lamina-associated domains. Conclusion HCNEs have distinct and protective sequence properties, undergo dynamic epigenetic regulation, and appear to be associated with the structural components of the chromatin, replication origins, and nuclear matrix. These observations indicate that such elements are likely to have essential cellular functions, and offer insights into their epigenetic properties.
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Affiliation(s)
- Loqmane Seridi
- Division of Biological and Environmental Sciences & Engineering, Division of Applied Mathematics and Computer Sciences, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia
| | - Taewoo Ryu
- Division of Biological and Environmental Sciences & Engineering, Division of Applied Mathematics and Computer Sciences, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia
- * E-mail: (T. Ryu); (T. Ravasi)
| | - Timothy Ravasi
- Division of Biological and Environmental Sciences & Engineering, Division of Applied Mathematics and Computer Sciences, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia
- Department of Medicine, Division of Genetics, University of California San Diego, La Jolla, California, United States of America
- * E-mail: (T. Ryu); (T. Ravasi)
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25
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Russell K, Cheng CH, Bizzaro JW, Ponts N, Emes RD, Le Roch K, Marx KA, Horrocks P. Homopolymer tract organization in the human malarial parasite Plasmodium falciparum and related Apicomplexan parasites. BMC Genomics 2014; 15:848. [PMID: 25281558 PMCID: PMC4194402 DOI: 10.1186/1471-2164-15-848] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 09/24/2014] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Homopolymeric tracts, particularly poly dA.dT, are enriched within the intergenic sequences of eukaryotic genomes where they appear to act as intrinsic regulators of nucleosome positioning. A previous study of the incomplete genome of the human malarial parasite Plasmodium falciparum reports a higher than expected enrichment of poly dA.dT tracts, far above that anticipated even in this highly AT rich genome. Here we report an analysis of the relative frequency, length and spatial arrangement of homopolymer tracts for the complete P. falciparum genome, extending this analysis to twelve additional genomes of Apicomplexan parasites important to human and animal health. In addition, using nucleosome-positioning data available for P. falciparum, we explore the correlation of poly dA.dT tracts with nucleosome-positioning data over key expression landmarks within intergenic regions. RESULTS We describe three apparent lineage-specific patterns of homopolymeric tract organization within the intergenic regions of these Apicomplexan parasites. Moreover, a striking pattern of enrichment of overly long poly dA.dT tracts in the intergenic regions of Plasmodium spp. uniquely extends into protein coding sequences. There is a conserved spatial arrangement of poly dA.dT immediately flanking open reading frames and over predicted core promoter sites. These key landmarks are all relatively depleted in nucleosomes in P. falciparum, as would be expected for poly dA.dT acting as nucleosome exclusion sequences. CONCLUSIONS Previous comparative studies of homopolymer tract organization emphasize evolutionary diversity; this is the first report of such an analysis within a single phylum. Our data provide insights into the evolution of homopolymeric tracts and the selective pressures at play in their maintenance and expansion.
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Affiliation(s)
- Karen Russell
- />Institute for Science and Technology in Medicine, Keele University, Stoke-on-Trent, ST5 5BG Staffordshire, UK
| | - Chia-Ho Cheng
- />Center for Intelligent Biomaterials, University of Massachusetts Lowell, Lowell, MA 01854 USA
- />Hebrew SeniorLife, Institute for Aging Research, Boston, MA 02131 USA
| | | | - Nadia Ponts
- />National Institute for Agricultural Research (INRA), UR1264-Mycology and Food Safety (MycSA), CS20032, 33882 Villenave d’Ornon Cedex, France
| | - Richard D Emes
- />School of Veterinary Medicine and Science, University of Nottingham, LE12 5RD Nottingham, Leicestershire, UK
- />Advanced Data Analysis Centre, University of Nottingham, Nottingham, UK
| | - Karine Le Roch
- />Department Cell Biology and Neuroscience, University of California, Riverside, CA 92521 USA
| | - Kenneth A Marx
- />Center for Intelligent Biomaterials, University of Massachusetts Lowell, Lowell, MA 01854 USA
| | - Paul Horrocks
- />Institute for Science and Technology in Medicine, Keele University, Stoke-on-Trent, ST5 5BG Staffordshire, UK
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26
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Yamagishi J, Wakaguri H, Yokoyama N, Yamashita R, Suzuki Y, Xuan X, Igarashi I. The Babesia bovis gene and promoter model: an update from full-length EST analysis. BMC Genomics 2014; 15:678. [PMID: 25124460 PMCID: PMC4148916 DOI: 10.1186/1471-2164-15-678] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 07/08/2014] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Babesia bovis is an apicomplexan parasite that causes babesiosis in infected cattle. Genomes of pathogens contain promising information that can facilitate the development of methods for controlling infections. Although the genome of B. bovis is publically available, annotated gene models are not highly reliable prior to experimental validation. Therefore, we validated a preproposed gene model of B. bovis and extended the associated annotations on the basis of experimentally obtained full-length expressed sequence tags (ESTs). RESULTS From in vitro cultured merozoites, 12,286 clones harboring full-length cDNAs were sequenced from both ends using the Sanger method, and 6,787 full-length cDNAs were assembled. These were then clustered, and a nonredundant referential data set of 2,115 full-length cDNA sequences was constructed. The comparison of the preproposed gene model with our data set identified 310 identical genes, 342 almost identical genes, 1,054 genes with potential structural inconsistencies, and 409 novel genes. The median length of 5' untranslated regions (UTRs) was 152 nt. Subsequently, we identified 4,086 transcription start sites (TSSs) and 2,023 transcriptionally active regions (TARs) by examining 5' ESTs. We identified ATGGGG and CCCCAT sites as consensus motifs in TARs that were distributed around -50 bp from TSSs. In addition, we found ACACA, TGTGT, and TATAT sites, which were distributed periodically around TSSs in cycles of approximately 150 bp. Moreover, related periodical distributions were not observed in mammalian promoter regions. CONCLUSIONS The observations in this study indicate the utility of integrated bioinformatics and experimental data for improving genome annotations. In particular, full-length cDNAs with one-base resolution for TSSs enabled the identification of consensus motifs in promoter sequences and demonstrated clear distributions of identified motifs. These observations allowed the illustration of a model promoter composition, which supports the differences in transcriptional regulation frameworks between apicomplexan parasites and mammals.
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Affiliation(s)
- Junya Yamagishi
- />Tohoku Medical Megabank Organization, Tohoku University, 6-3-09, aza Aoba, Sendai, Miyagi 980-8579 Japan
- />National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho west 2-13, Obihiro, Hokkaido 080-8555 Japan
| | - Hiroyuki Wakaguri
- />Department of Medical Genome Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562 Japan
| | - Naoaki Yokoyama
- />National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho west 2-13, Obihiro, Hokkaido 080-8555 Japan
| | - Riu Yamashita
- />Tohoku Medical Megabank Organization, Tohoku University, 6-3-09, aza Aoba, Sendai, Miyagi 980-8579 Japan
| | - Yutaka Suzuki
- />Department of Medical Genome Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562 Japan
| | - Xuenan Xuan
- />National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho west 2-13, Obihiro, Hokkaido 080-8555 Japan
| | - Ikuo Igarashi
- />National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho west 2-13, Obihiro, Hokkaido 080-8555 Japan
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27
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Maree JP, Patterton HG. The epigenome of Trypanosoma brucei: a regulatory interface to an unconventional transcriptional machine. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1839:743-50. [PMID: 24942804 DOI: 10.1016/j.bbagrm.2014.05.028] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 05/09/2014] [Accepted: 05/28/2014] [Indexed: 12/15/2022]
Abstract
The epigenome represents a major regulatory interface to the eukaryotic genome. Nucleosome positions, histone variants, histone modifications and chromatin associated proteins all play a role in the epigenetic regulation of DNA function. Trypanosomes, an ancient branch of the eukaryotic evolutionary lineage, exhibit some highly unusual transcriptional features, including the arrangement of functionally unrelated genes in large, polymerase II transcribed polycistronic transcription units, often exceeding hundreds of kilobases in size. It is generally believed that transcription initiation plays a minor role in regulating the transcript level of genes in trypanosomes, which are mainly regulated post-transcriptionally. Recent advances have revealed that epigenetic mechanisms play an essential role in the transcriptional regulation of Trypanosoma brucei. This suggested that the modulation of gene activity, particularly that of pol I transcribed genes, is, indeed, an important control mechanism, and that the epigenome is critical in regulating gene expression programs that allow the successful migration of this parasite between hosts, as well as the continuous evasion of the immune system in mammalian hosts. A wide range of epigenetic signals, readers, writers and erasers have been identified in trypanosomes, some of which have been mapped to essential genetic functions. Some epigenetic mechanisms have also been observed to be unique to trypanosomes. We review recent advances in our understanding of epigenetic control mechanisms in T. brucei, the causative agent of African sleeping sickness, and highlight the utility of epigenetic targets in the possible development of new therapies for human African trypanosomiasis.
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Affiliation(s)
- Johannes P Maree
- Advanced Biomolecular Research Cluster, University of the Free State, PO Box 339, Bloemfontein 9332, South Africa
| | - Hugh-G Patterton
- Advanced Biomolecular Research Cluster, University of the Free State, PO Box 339, Bloemfontein 9332, South Africa.
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Bunnik EM, Polishko A, Prudhomme J, Ponts N, Gill SS, Lonardi S, Le Roch KG. DNA-encoded nucleosome occupancy is associated with transcription levels in the human malaria parasite Plasmodium falciparum. BMC Genomics 2014; 15:347. [PMID: 24885191 PMCID: PMC4035074 DOI: 10.1186/1471-2164-15-347] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 04/30/2014] [Indexed: 12/11/2022] Open
Abstract
Background In eukaryotic organisms, packaging of DNA into nucleosomes controls gene expression by regulating access of the promoter to transcription factors. The human malaria parasite Plasmodium falciparum encodes relatively few transcription factors, while extensive nucleosome remodeling occurs during its replicative cycle in red blood cells. These observations point towards an important role of the nucleosome landscape in regulating gene expression. However, the relation between nucleosome positioning and transcriptional activity has thus far not been explored in detail in the parasite. Results Here, we analyzed nucleosome positioning in the asexual and sexual stages of the parasite’s erythrocytic cycle using chromatin immunoprecipitation of MNase-digested chromatin, followed by next-generation sequencing. We observed a relatively open chromatin structure at the trophozoite and gametocyte stages, consistent with high levels of transcriptional activity in these stages. Nucleosome occupancy of genes and promoter regions were subsequently compared to steady-state mRNA expression levels. Transcript abundance showed a strong inverse correlation with nucleosome occupancy levels in promoter regions. In addition, AT-repeat sequences were strongly unfavorable for nucleosome binding in P. falciparum, and were overrepresented in promoters of highly expressed genes. Conclusions The connection between chromatin structure and gene expression in P. falciparum shares similarities with other eukaryotes. However, the remarkable nucleosome dynamics during the erythrocytic stages and the absence of a large variety of transcription factors may indicate that nucleosome binding and remodeling are critical regulators of transcript levels. Moreover, the strong dependency between chromatin structure and DNA sequence suggests that the P. falciparum genome may have been shaped by nucleosome binding preferences. Nucleosome remodeling mechanisms in this deadly parasite could thus provide potent novel anti-malarial targets. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-347) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | | | - Karine G Le Roch
- Department of Cell Biology and Neuroscience, Center for Disease Vector Research, Institute for Integrative Genome Biology, University of California, Riverside, 900 University Avenue, Riverside, CA 92521, USA.
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29
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Duffy MF, Selvarajah SA, Josling GA, Petter M. Epigenetic regulation of the Plasmodium falciparum genome. Brief Funct Genomics 2013; 13:203-16. [PMID: 24326119 DOI: 10.1093/bfgp/elt047] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Recent research has highlighted some unique aspects of chromatin biology in the malaria parasite Plasmodium falciparum. During its erythrocytic lifecycle P. falciparum maintains its genome primarily as unstructured euchromatin. Indeed there is no clear role for chromatin-mediated silencing of the majority of the developmentally expressed genes in P. falciparum. However discontinuous stretches of heterochromatin are critical for variegated expression of contingency genes that mediate key pathogenic processes in malaria. These range from invasion of erythrocytes and antigenic variation to solute transport and growth adaptation in response to environmental changes. Despite lack of structure within euchromatin the nucleus maintains functional compartments that regulate expression of many genes at the nuclear periphery, particularly genes with clonally variant expression. The typical components of the chromatin regulatory machinery are present in P. falciparum; however, some of these appear to have evolved novel species-specific functions, e.g. the dynamic regulation of histone variants at virulence gene promoters. The parasite also appears to have repeatedly acquired chromatin regulatory proteins through lateral transfer from endosymbionts and from the host. P. falciparum chromatin regulators have been successfully targeted with multiple drugs in laboratory studies; hopefully their functional divergence from human counterparts will allow the development of parasite-specific inhibitors.
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30
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Peprah E, Wonkam A. Biomedical research, a tool to address the health issues that affect African populations. Global Health 2013; 9:50. [PMID: 24143865 PMCID: PMC4015770 DOI: 10.1186/1744-8603-9-50] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 08/05/2013] [Indexed: 12/22/2022] Open
Abstract
Traditionally, biomedical research endeavors in low to middle resources countries have focused on communicable diseases. However, data collected over the past 20 years by the World Health Organization (WHO) show a significant increase in the number of people suffering from non-communicable diseases (e.g. heart disease, diabetes, cancer and pulmonary diseases). Within the coming years, WHO predicts significant decreases in communicable diseases while non-communicable diseases are expected to double in low and middle income countries in sub-Saharan Africa. The predicted increase in the non-communicable diseases population could be economically burdensome for the basic healthcare infrastructure of countries that lack resources to address this emerging disease burden. Biomedical research could stimulate development of healthcare and biomedical infrastructure. If this development is sustainable, it provides an opportunity to alleviate the burden of both communicable and non-communicable diseases through diagnosis, prevention and treatment. In this paper, we discuss how research using biomedical technology, especially genomics, has produced data that enhances the understanding and treatment of both communicable and non-communicable diseases in sub-Saharan Africa. We further discuss how scientific development can provide opportunities to pursue research areas responsive to the African populations. We limit our discussion to biomedical research in the areas of genomics due to its substantial impact on the scientific community in recent years however, we also recognize that targeted investments in other scientific disciplines could also foster further development in African countries.
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Affiliation(s)
- Emmanuel Peprah
- Current address: National Institutes of Health, Building 1, RM 256A, Bethesda MD 20892, USA
| | - Ambroise Wonkam
- Division of Human Genetics, Faculty of Health Sciences, University of Cape Town, Anzio Road-7925, Observatory, Cape Town, South Africa
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31
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Cai H, Hong C, Lilburn TG, Rodriguez AL, Chen S, Gu J, Kuang R, Wang Y. A novel subnetwork alignment approach predicts new components of the cell cycle regulatory apparatus in Plasmodium falciparum. BMC Bioinformatics 2013; 14 Suppl 12:S2. [PMID: 24267797 PMCID: PMC3848769 DOI: 10.1186/1471-2105-14-s12-s2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Background According to the World Health organization, half the world's population is at risk of contracting malaria. They estimated that in 2010 there were 219 million cases of malaria, resulting in 660,000 deaths and an enormous economic burden on the countries where malaria is endemic. The adoption of various high-throughput genomics-based techniques by malaria researchers has meant that new avenues to the study of this disease are being explored and new targets for controlling the disease are being developed. Here, we apply a novel neighborhood subnetwork alignment approach to identify the interacting elements that help regulate the cell cycle of the malaria parasite Plasmodium falciparum. Results Our novel subnetwork alignment approach was used to compare networks in Escherichia coli and P. falciparum. Some 574 P. falciparum proteins were revealed as functional orthologs of known cell cycle proteins in E. coli. Over one third of these predicted functional orthologs were annotated as "conserved Plasmodium proteins" or "putative uncharacterized proteins" of unknown function. The predicted functionalities included cyclins, kinases, surface antigens, transcriptional regulators and various functions related to DNA replication, repair and cell division. Conclusions The results of our analysis demonstrate the power of our subnetwork alignment approach to assign functionality to previously unannotated proteins. Here, the focus was on proteins involved in cell cycle regulation. These proteins are involved in the control of diverse aspects of the parasite lifecycle and of important aspects of pathogenesis.
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32
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Deshmukh AS, Srivastava S, Dhar SK. Plasmodium falciparum: epigenetic control of var gene regulation and disease. Subcell Biochem 2013; 61:659-682. [PMID: 23150271 DOI: 10.1007/978-94-007-4525-4_28] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Plasmodium falciparum, one of the deadliest parasites on earth causes human malaria resulting one million deaths annually. Central to the parasite pathogenicity and morbidity is the switching of parasite virulence (var) gene expression causing host immune evasion. The regulation of Plasmodium var gene expression is poorly understood. The complex life cycle of Plasmodium and mutually exclusive expression pattern of var genes make this disease difficult to control. Recent studies have demonstrated the pivotal role of epigenetic mechanism for control of coordinated expression of var genes, important for various clinical manifestations of malaria. In this review, we discuss about different Plasmodium histones and their various modifications important for gene expression and gene repression.Contribution of epigenetic mechanism to understand the var gene expression is also highlighted. We also describe in details P. falciparum nuclear architecture including heterochromatin, euchromatin and telomeric regions and their importance in subtelomeric and centrally located var gene expression. Finally, we explore the possibility of using Histone Acetyl Transferase (HAT) and Histone Deacetylase (HDAC)inhibitors against multi-drug resistance malaria parasites to provide another line of treatment for malaria.
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Affiliation(s)
- Abhijit S Deshmukh
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India
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33
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Pascali C, Teichmann M. RNA polymerase III transcription - regulated by chromatin structure and regulator of nuclear chromatin organization. Subcell Biochem 2013; 61:261-287. [PMID: 23150255 DOI: 10.1007/978-94-007-4525-4_12] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
RNA polymerase III (Pol III) transcription is regulated by modifications of the chromatin. DNA methylation and post-translational modifications of histones, such as acetylation, phosphorylation and methylation have been linked to Pol III transcriptional activity. In addition to being regulated by modifications of DNA and histones, Pol III genes and its transcription factors have been implicated in the organization of nuclear chromatin in several organisms. In yeast, the ability of the Pol III transcription system to contribute to nuclear organization seems to be dependent on direct interactions of Pol III genes and/or its transcription factors TFIIIC and TFIIIB with the structural maintenance of chromatin (SMC) protein-containing complexes cohesin and condensin. In human cells, Pol III genes and transcription factors have also been shown to colocalize with cohesin and the transcription regulator and genome organizer CCCTC-binding factor (CTCF). Furthermore, chromosomal sites have been identified in yeast and humans that are bound by partial Pol III machineries (extra TFIIIC sites - ETC; chromosome organizing clamps - COC). These ETCs/COC as well as Pol III genes possess the ability to act as boundary elements that restrict spreading of heterochromatin.
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Affiliation(s)
- Chiara Pascali
- Institut Européen de Chimie et Biologie (IECB), Université Bordeaux Segalen / INSERM U869, 2, rue Robert Escarpit, 33607, Pessac, France
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34
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Cortés A, Crowley VM, Vaquero A, Voss TS. A view on the role of epigenetics in the biology of malaria parasites. PLoS Pathog 2012; 8:e1002943. [PMID: 23271963 PMCID: PMC3521673 DOI: 10.1371/journal.ppat.1002943] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Affiliation(s)
- Alfred Cortés
- Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Barcelona, Catalonia, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Catalonia, Spain
- * E-mail:
| | - Valerie M. Crowley
- Institute for Research in Biomedicine (IRB), Barcelona, Catalonia, Spain
| | - Alejandro Vaquero
- Cancer Epigenetics and Biology Program (PEBC), Bellvitge Biomedical Research Institute (IDIBELL), L'Hospitalet de Llobregat, Barcelona, Catalonia, Spain
| | - Till S. Voss
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
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35
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Cai H, Zhou Z, Gu J, Wang Y. Comparative Genomics and Systems Biology of Malaria Parasites Plasmodium.. Curr Bioinform 2012; 7. [PMID: 24298232 DOI: 10.2174/157489312803900965] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Malaria is a serious infectious disease that causes over one million deaths yearly. It is caused by a group of protozoan parasites in the genus Plasmodium. No effective vaccine is currently available and the elevated levels of resistance to drugs in use underscore the pressing need for novel antimalarial targets. In this review, we survey omics centered developments in Plasmodium biology, which have set the stage for a quantum leap in our understanding of the fundamental processes of the parasite life cycle and mechanisms of drug resistance and immune evasion.
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Affiliation(s)
- Hong Cai
- Department of Biology, University of Texas at San Antonio, San Antonio, TX 78249, USA
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36
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Nishida H. Nucleosome Positioning. ISRN MOLECULAR BIOLOGY 2012; 2012:245706. [PMID: 27335664 PMCID: PMC4890889 DOI: 10.5402/2012/245706] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/19/2012] [Accepted: 09/17/2012] [Indexed: 02/05/2023]
Abstract
Nucleosome positioning is not only related to genomic DNA compaction but also to other biological functions. After the chromatin is digested by micrococcal nuclease, nucleosomal (nucleosome-bound) DNA fragments can be sequenced and mapped on the genomic DNA sequence. Due to the development of modern DNA sequencing technology, genome-wide nucleosome mapping has been performed in a wide range of eukaryotic species. Comparative analyses of the nucleosome positions have revealed that the nucleosome is more frequently formed in exonic than intronic regions, and that most of transcription start and translation (or transcription) end sites are located in nucleosome linker DNA regions, indicating that nucleosome positioning influences transcription initiation, transcription termination, and gene splicing. In addition, nucleosomal DNA contains guanine and cytosine (G + C)-rich sequences and a high level of cytosine methylation. Thus, the nucleosome positioning system has been conserved during eukaryotic evolution.
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Affiliation(s)
- Hiromi Nishida
- Agricultural Bioinformatics Research Unit, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan
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37
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Abstract
Temporal and spatial organization of the nucleus is critical for the control of transcription, mRNA processing and the assembly of ribosomes. This includes the occupancy of specific territories by mammalian chromosomes, the presence of subnuclear compartments such as the nucleolus and Cajal bodies and the division of chromatin between active and inactive states. These latter are commonly associated with the location of DNA within euchromatin and heterochromatin respectively; critically these distinctions arise through modifications to chromatin-associated proteins, including histones, as well as the preferential localization of heterochromatin at the nuclear periphery. Most research on nuclear organization has focused on metazoa and fungi; however, recent technical advances have made more divergent eukaryotes accessible to study, with some surprising results. For example, the organization of heterochromatin is mediated in metazoan nuclei in large part by lamins, the prototypical intermediate filament proteins. Despite the presence of heterochromatin, detected both biochemically and by EM in most eukaryotic organisms, until this year lamins were thought to be restricted to metazoan taxa, and the proteins comprising the lamina in other lineages were unknown. Recent work indicates the presence of lamin orthologs in amoeba, while trypanosomatids possess a large coiled-coil protein, NUP-1, that performs functions analogous to lamins. These data indicate that the presence of a nuclear lamina is substantially more widespread than previously thought, with major implications for the evolution of eukaryotic gene expression mechanisms. We discuss these and other recent findings on the organization of nuclei in diverse organisms, and the implications of these findings for the evolutionary origin of eukaryotes.
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Affiliation(s)
- Mark C Field
- Department of Pathology; University of Cambridge, Cambridge, UK.
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38
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Hoeijmakers WAM, Stunnenberg HG, Bártfai R. Placing the Plasmodium falciparum epigenome on the map. Trends Parasitol 2012; 28:486-95. [PMID: 22999479 DOI: 10.1016/j.pt.2012.08.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 08/23/2012] [Accepted: 08/23/2012] [Indexed: 02/04/2023]
Abstract
It is becoming increasingly evident that epigenetic mechanisms that act on and regulate chromatin structure play a key role in the development, adaptation, and survival of the malaria parasite within its human host. The study of epigenetics in Plasmodium falciparum started to flourish in recent years due to improvement of genomic technologies. Here we summarize the knowledge gained from genome-wide localization profiling of different epigenetic features, and discuss hypotheses emerging from the analysis of these 'descriptive' epigenetic maps. Furthermore, we highlight key questions to be answered, and provide a glimpse of developments required to gain true mechanistic understanding and to lift this maturing field to the next level.
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Affiliation(s)
- Wieteke A M Hoeijmakers
- Department of Molecular Biology, Radboud University, Nijmegen Center for Molecular Life Sciences, 6525GA Nijmegen, The Netherlands.
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39
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Le Roch KG, Chung DWD, Ponts N. Genomics and integrated systems biology in Plasmodium falciparum: a path to malaria control and eradication. Parasite Immunol 2012; 34:50-60. [PMID: 21995286 DOI: 10.1111/j.1365-3024.2011.01340.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The first draft of the human malaria parasite's genome was released in 2002. Since then, the malaria scientific community has witnessed a steady embrace of new and powerful functional genomic studies. Over the years, these approaches have slowly revolutionized malaria research and enabled the comprehensive, unbiased investigation of various aspects of the parasite's biology. These genome-wide analyses delivered a refined annotation of the parasite's genome, delivered a better knowledge of its RNA, proteins and metabolite derivatives, and fostered the discovery of new vaccine and drug targets. Despite the positive impacts of these genomic studies, most research and investment still focus on protein targets, drugs and vaccine candidates that were known before the publication of the parasite genome sequence. However, recent access to next-generation sequencing technologies, along with an increased number of genome-wide applications, is expanding the impact of the parasite genome on biomedical research, contributing to a paradigm shift in research activities that may possibly lead to new optimized diagnosis and treatments. This review provides an update of Plasmodium falciparum genome sequences and an overview of the rapid development of genomics and system biology applications that have an immense potential of creating powerful tools for a successful malaria eradication campaign.
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Affiliation(s)
- K G Le Roch
- Department of Cell Biology and Neuroscience, University of California Riverside, Institute for Integrative Genome Biology, and Center for Disease Vector Research, Riverside, CA 92521, USA.
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40
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Chromatin modifications, epigenetics, and how protozoan parasites regulate their lives. Trends Parasitol 2012; 28:202-13. [PMID: 22480826 DOI: 10.1016/j.pt.2012.02.009] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Revised: 02/21/2012] [Accepted: 02/29/2012] [Indexed: 12/19/2022]
Abstract
Chromatin structure plays a vital role in epigenetic regulation of protozoan parasite gene expression. Epigenetic gene regulation impacts upon parasite virulence, differentiation and cell-cycle control. Recent work in many laboratories has elucidated the functions of proteins that regulate parasite gene expression by chemical modification of constituent nucleosomes. A major focus of investigation has been the characterization of post-translational modifications (PTMs) of histones and the identification of the enzymes responsible. Despite conserved features and specificity common to all eukaryotes, parasite enzymes involved in chromatin modification have unique functions that regulate unique aspects of parasite biology.
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41
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Duffy MF, Selvarajah SA, Josling GA, Petter M. The role of chromatin in Plasmodium gene expression. Cell Microbiol 2012; 14:819-28. [DOI: 10.1111/j.1462-5822.2012.01777.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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42
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Cabral FJ, Fotoran WL, Wunderlich G. Dynamic activation and repression of the plasmodium falciparum rif gene family and their relation to chromatin modification. PLoS One 2012; 7:e29881. [PMID: 22235345 PMCID: PMC3250495 DOI: 10.1371/journal.pone.0029881] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 12/07/2011] [Indexed: 11/18/2022] Open
Abstract
The regulation of variant gene expression in Plasmodium falciparum is still only partially understood. Regulation of var genes, the most studied gene family involved in antigenic variation, is orchestrated by a dynamic pattern of inherited chromatin states. Although recent evidence pointed to epigenetic regulation of transcribed and repressed rif loci, little is known about specific on/off associated histone modifications of individual rif genes. To investigate the chromatin marks for transcribed and repressed rif loci, we cultivated parasites and evaluated the transcriptional status of chosen rif targets by qRT-PCR and performed ChIP assays using H3K9ac and H3K9me3 antibodies. We then monitored changes in the epigenetic patterns in parasites after several reinvasions and also evaluated the “poised” mark in trophozoites and schizonts of the same erythrocytic cycle by ChIP using H3K4me2 specific antibodies. Our results show that H3K9 is acetylated in transcribed rif loci and trimethylated or even unmodified in repressed rif loci. These transcriptional and epigenetic states are inherited after several reinvasions. The poised modification H3K4me2 showed a tendency to be more present in loci in trophozoites that upon progression to schizonts strongly transcribe the respective locus. However, this effect was not consistently observed for all monitored loci. While our data show important similarities to var transcription-associated chromatin modifications, the observed swiftly occurring modifications at rif loci and the absence of H3K9 modification point to a different dynamic of recruitment of chromatin modifying enzymes.
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Affiliation(s)
- Fernanda J. Cabral
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, São Paulo, Brazil
| | - Wesley L. Fotoran
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, São Paulo, Brazil
| | - Gerhard Wunderlich
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, São Paulo, Brazil
- * E-mail:
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43
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Thanakiatkrai P, Welch L. An investigation into the protective capabilities of nucleosomes on forensic STRs. FORENSIC SCIENCE INTERNATIONAL GENETICS SUPPLEMENT SERIES 2011. [DOI: 10.1016/j.fsigss.2011.09.070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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44
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Laurentino EC, Taylor S, Mair GR, Lasonder E, Bartfai R, Stunnenberg HG, Kroeze H, Ramesar J, Franke-Fayard B, Khan SM, Janse CJ, Waters AP. Experimentally controlled downregulation of the histone chaperone FACT in Plasmodium berghei reveals that it is critical to male gamete fertility. Cell Microbiol 2011; 13:1956-74. [PMID: 21899698 PMCID: PMC3429858 DOI: 10.1111/j.1462-5822.2011.01683.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Human FACT (facilitates chromatin transcription) consists of the proteins SPT16 and SSRP1 and acts as a histone chaperone in the (dis)assembly of nucleosome (and thereby chromatin) structure during transcription and DNA replication. We identified a Plasmodium berghei protein, termed FACT-L, with homology to the SPT16 subunit of FACT. Epitope tagging of FACT-L showed nuclear localization with high expression in the nuclei of (activated) male gametocytes. The gene encoding FACT-L could not be deleted indicating an essential role during blood-stage development. Using a ‘promoter-swap’ approach whereby the fact-l promoter was replaced by an ‘asexual blood stage-specific’ promoter that is silent in gametocytes, transcription of fact-l in promoter-swap mutant gametocytes was downregulated compared with wild-type gametocytes. These mutant male gametocytes showed delayed DNA replication and gamete formation. Male gamete fertility was strongly reduced while female gamete fertility was unaffected; residual ookinetes generated oocysts that arrested early in development and failed to enter sporogony. Therefore FACT is critically involved in the formation of fertile male gametes and parasite transmission. ‘Promoter swapping’ is a powerful approach for the functional analysis of proteins in gametocytes (and beyond) that are essential during asexual blood-stage development.
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Affiliation(s)
- Eliane C Laurentino
- Leiden Malaria Research Group, Department of Parasitology, Leiden University Medical, Albinusdreef 2, 2333 ZA Leiden, the Netherlands
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45
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The disequilibrium of nucleosomes distribution along chromosomes plays a functional and evolutionarily role in regulating gene expression. PLoS One 2011; 6:e23219. [PMID: 21886783 PMCID: PMC3158759 DOI: 10.1371/journal.pone.0023219] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2010] [Accepted: 07/14/2011] [Indexed: 01/24/2023] Open
Abstract
To further understand the relationship between nucleosome-space occupancy (NO) and global transcriptional activity in mammals, we acquired a set of genome-wide nucleosome distribution and transcriptome data from the mouse cerebrum and testis based on ChIP (H3)-seq and RNA-seq, respectively. We identified a nearly consistent NO patterns among three mouse tissues—cerebrum, testis, and ESCs—and found, through clustering analysis for transcriptional activation, that the NO variations among chromosomes are closely associated with distinct expression levels between house-keeping (HK) genes and tissue-specific (TS) genes. Both TS and HK genes form clusters albeit the obvious majority. This feature implies that NO patterns, i.e. nucleosome binding and clustering, are coupled with gene clustering that may be functionally and evolutionarily conserved in regulating gene expression among different cell types.
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Abstract
The DNA of eukaryotic cells is spooled around large histone protein complexes, forming nucleosomes that make up the basis for a high-order packaging structure called chromatin. Compared to naked DNA, nucleosomal DNA is less accessible to regulatory proteins and regulatory processes. The exact positions of nucleosomes therefore influence several cellular processes, including gene expression, chromosome segregation, recombination, replication, and DNA repair. Here, we review recent technological advances enabling the genome-wide mapping of nucleosome positions in the model eukaryote Saccharomyces cerevisiae. We discuss the various parameters that determine nucleosome positioning in vivo, including cis factors like AT content, variable tandem repeats, and poly(dA:dT) tracts that function as chromatin barriers and trans factors such as chromatin remodeling complexes, transcription factors, histone-modifying enzymes, and RNA polymerases. In the last section, we review the biological role of chromatin in gene transcription, the evolution of gene regulation, and epigenetic phenomena.
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47
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Kissinger JC, DeBarry J. Genome cartography: charting the apicomplexan genome. Trends Parasitol 2011; 27:345-54. [PMID: 21764378 DOI: 10.1016/j.pt.2011.03.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Revised: 03/18/2011] [Accepted: 03/21/2011] [Indexed: 11/18/2022]
Abstract
Genes reside in particular genomic contexts that can be mapped at many levels. Historically, 'genetic maps' were used primarily to locate genes. Recent technological advances in the determination of genome sequences have made the analysis and comparison of whole genomes possible and increasingly tractable. What do we see if we shift our focus from gene content (the 'inventory' of genes contained within a genome) to the composition and organization of a genome? This review examines what has been learned about the evolution of the apicomplexan genome as well as the significance and impact of genomic location on our understanding of the eukaryotic genome and parasite biology.
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Affiliation(s)
- Jessica C Kissinger
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, USA.
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Broadbent KM, Park D, Wolf AR, Van Tyne D, Sims JS, Ribacke U, Volkman S, Duraisingh M, Wirth D, Sabeti PC, Rinn JL. A global transcriptional analysis of Plasmodium falciparum malaria reveals a novel family of telomere-associated lncRNAs. Genome Biol 2011; 12:R56. [PMID: 21689454 PMCID: PMC3218844 DOI: 10.1186/gb-2011-12-6-r56] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 04/27/2011] [Accepted: 06/20/2011] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Mounting evidence suggests a major role for epigenetic feedback in Plasmodium falciparum transcriptional regulation. Long non-coding RNAs (lncRNAs) have recently emerged as a new paradigm in epigenetic remodeling. We therefore set out to investigate putative roles for lncRNAs in P. falciparum transcriptional regulation. RESULTS We used a high-resolution DNA tiling microarray to survey transcriptional activity across 22.6% of the P. falciparum strain 3D7 genome. We identified 872 protein-coding genes and 60 putative P. falciparum lncRNAs under developmental regulation during the parasite's pathogenic human blood stage. Further characterization of lncRNA candidates led to the discovery of an intriguing family of lncRNA telomere-associated repetitive element transcripts, termed lncRNA-TARE. We have quantified lncRNA-TARE expression at 15 distinct chromosome ends and mapped putative transcriptional start and termination sites of lncRNA-TARE loci. Remarkably, we observed coordinated and stage-specific expression of lncRNA-TARE on all chromosome ends tested, and two dominant transcripts of approximately 1.5 kb and 3.1 kb transcribed towards the telomere. CONCLUSIONS We have characterized a family of 22 telomere-associated lncRNAs in P. falciparum. Homologous lncRNA-TARE loci are coordinately expressed after parasite DNA replication, and are poised to play an important role in P. falciparum telomere maintenance, virulence gene regulation, and potentially other processes of parasite chromosome end biology. Further study of lncRNA-TARE and other promising lncRNA candidates may provide mechanistic insight into P. falciparum transcriptional regulation.
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Affiliation(s)
- Kate M Broadbent
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
- Broad Institute, 7 Cambridge Center, Cambridge, MA 02142, USA
| | - Daniel Park
- Broad Institute, 7 Cambridge Center, Cambridge, MA 02142, USA
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Ashley R Wolf
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
- Broad Institute, 7 Cambridge Center, Cambridge, MA 02142, USA
| | - Daria Van Tyne
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Avenue, Boston, MA 02115, USA
| | - Jennifer S Sims
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Avenue, Boston, MA 02115, USA
| | - Ulf Ribacke
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Avenue, Boston, MA 02115, USA
| | - Sarah Volkman
- Broad Institute, 7 Cambridge Center, Cambridge, MA 02142, USA
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Avenue, Boston, MA 02115, USA
- School of Nursing and Health Sciences, Simmons College, 300 The Fenway, Boston, MA 02115, USA
| | - Manoj Duraisingh
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Avenue, Boston, MA 02115, USA
| | - Dyann Wirth
- Broad Institute, 7 Cambridge Center, Cambridge, MA 02142, USA
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 651 Huntington Avenue, Boston, MA 02115, USA
| | - Pardis C Sabeti
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
- Broad Institute, 7 Cambridge Center, Cambridge, MA 02142, USA
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
- FAS Center for Systems Biology, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA
| | - John L Rinn
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
- Broad Institute, 7 Cambridge Center, Cambridge, MA 02142, USA
- Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA
- Department of Stem Cell and Regenerative Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA
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Abstract
Whole-genome comparisons provide insight into genome evolution by informing on gene repertoires, gene gains/losses, and genome organization. Most of our knowledge about eukaryotic genome evolution is derived from studies of multicellular model organisms. The eukaryotic phylum Apicomplexa contains obligate intracellular protist parasites responsible for a wide range of human and veterinary diseases (e.g., malaria, toxoplasmosis, and theileriosis). We have developed an in silico protein-encoding gene based pipeline to investigate synteny across 12 apicomplexan species from six genera. Genome rearrangement between lineages is extensive. Syntenic regions (conserved gene content and order) are rare between lineages and appear to be totally absent across the phylum, with no group of three genes found on the same chromosome and in the same order within 25 kb up- and downstream of any orthologous genes. Conserved synteny between major lineages is limited to small regions in Plasmodium and Theileria/Babesia species, and within these conserved regions, there are a number of proteins putatively targeted to organelles. The observed overall lack of synteny is surprising considering the divergence times and the apparent absence of transposable elements (TEs) within any of the species examined. TEs are ubiquitous in all other groups of eukaryotes studied to date and have been shown to be involved in genomic rearrangements. It appears that there are different criteria governing genome evolution within the Apicomplexa relative to other well-studied unicellular and multicellular eukaryotes.
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Affiliation(s)
- Jeremy D DeBarry
- Center for Tropical and Emerging Global Diseases, University of Georgia, USA.
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Expression of P. falciparum var genes involves exchange of the histone variant H2A.Z at the promoter. PLoS Pathog 2011; 7:e1001292. [PMID: 21379342 PMCID: PMC3040674 DOI: 10.1371/journal.ppat.1001292] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Accepted: 01/12/2011] [Indexed: 12/31/2022] Open
Abstract
Plasmodium falciparum employs antigenic variation to evade the human immune response by switching the expression of different variant surface antigens encoded by the var gene family. Epigenetic mechanisms including histone modifications and sub-nuclear compartmentalization contribute to transcriptional regulation in the malaria parasite, in particular to control antigenic variation. Another mechanism of epigenetic control is the exchange of canonical histones with alternative variants to generate functionally specialized chromatin domains. Here we demonstrate that the alternative histone PfH2A.Z is associated with the epigenetic regulation of var genes. In many eukaryotic organisms the histone variant H2A.Z mediates an open chromatin structure at promoters and facilitates diverse levels of regulation, including transcriptional activation. Throughout the asexual, intraerythrocytic lifecycle of P. falciparum we found that the P. falciparum ortholog of H2A.Z (PfH2A.Z) colocalizes with histone modifications that are characteristic of transcriptionally-permissive euchromatin, but not with markers of heterochromatin. Consistent with this finding, antibodies to PfH2A.Z co-precipitate the permissive modification H3K4me3. By chromatin-immunoprecipitation we show that PfH2A.Z is enriched in nucleosomes around the transcription start site (TSS) in both transcriptionally active and silent stage-specific genes. In var genes, however, PfH2A.Z is enriched at the TSS only during active transcription in ring stage parasites. Thus, in contrast to other genes, temporal var gene regulation involves histone variant exchange at promoter nucleosomes. Sir2 histone deacetylases are important for var gene silencing and their yeast ortholog antagonises H2A.Z function in subtelomeric yeast genes. In immature P. falciparum parasites lacking Sir2A or Sir2B high var transcription levels correlate with enrichment of PfH2A.Z at the TSS. As Sir2A knock out parasites mature the var genes are silenced, but PfH2A.Z remains enriched at the TSS of var genes; in contrast, PfH2A.Z is lost from the TSS of de-repressed var genes in mature Sir2B knock out parasites. This result indicates that PfH2A.Z occupancy at the active var promoter is antagonized by PfSir2A during the intraerythrocytic life cycle. We conclude that PfH2A.Z contributes to the nucleosome architecture at promoters and is regulated dynamically in active var genes. Plasmodium falciparum is a protist parasite that causes malaria and kills more than 800,000 people per year. The parasite escapes from the human immune response by antigenic variation through switching between expression of different var genes. These encode different variant antigens that are expressed on the surface of the infected erythrocyte and mediate pathogenic adhesion of the infected erythrocytes to host receptors. Understanding how this process is regulated may lead to the identification of factors that are essential for immune evasion and that could represent novel drug targets. Here, we have identified the parasite's histone variant PfH2A.Z as a novel contributor to the transcriptional regulation of antigenic variation. PfH2A.Z is enriched in the promoter of many genes, but enrichment correlates with gene expression only in var genes. Furthermore we show that PfH2A.Z enrichment in var promoters is antagonised by the var gene silencing factor PfSir2A. These findings further extend our knowledge of the complex mechanisms regulating gene expression in P. falciparum.
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