1
|
Menezes AP, Murillo AM, de Castro CG, Bellini NK, Tosi LRO, Thiemann OH, Elias MC, Silber AM, da Cunha JPC. Navigating the boundaries between metabolism and epigenetics in trypanosomes. Trends Parasitol 2023; 39:682-695. [PMID: 37349193 DOI: 10.1016/j.pt.2023.05.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 05/24/2023] [Accepted: 05/24/2023] [Indexed: 06/24/2023]
Abstract
Epigenetic marks enable cells to acquire new biological features that favor their adaptation to environmental changes. These marks are chemical modifications on chromatin-associated proteins and nucleic acids that lead to changes in the chromatin landscape and may eventually affect gene expression. The chemical tags of these epigenetic marks are comprised of intermediate cellular metabolites. The number of discovered associations between metabolism and epigenetics has increased, revealing how environment influences gene regulation and phenotype diversity. This connection is relevant to all organisms but underappreciated in digenetic parasites, which must adapt to different environments as they progress through their life cycles. This review speculates and proposes associations between epigenetics and metabolism in trypanosomes, which are protozoan parasites that cause human and livestock diseases.
Collapse
Affiliation(s)
- Ana Paula Menezes
- Laboratório de Ciclo Celular - Instituto Butantan, São Paulo-SP, Brazil; Centro de Toxinas, Resposta Imune e Sinalização Celular (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - Ana Milena Murillo
- Laboratório de Bioquímica de Tryps - LabTryps, Departamento de Parasitologia, Universidade de São Paulo, São Paulo-SP, Brazil
| | - Camila Gachet de Castro
- Laboratório de Ciclo Celular - Instituto Butantan, São Paulo-SP, Brazil; Centro de Toxinas, Resposta Imune e Sinalização Celular (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - Natalia Karla Bellini
- Laboratório de Ciclo Celular - Instituto Butantan, São Paulo-SP, Brazil; Centro de Toxinas, Resposta Imune e Sinalização Celular (CeTICS), Instituto Butantan, São Paulo, Brazil
| | | | | | - Maria Carolina Elias
- Laboratório de Ciclo Celular - Instituto Butantan, São Paulo-SP, Brazil; Centro de Toxinas, Resposta Imune e Sinalização Celular (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - Ariel Mariano Silber
- Laboratório de Bioquímica de Tryps - LabTryps, Departamento de Parasitologia, Universidade de São Paulo, São Paulo-SP, Brazil.
| | - Julia Pinheiro Chagas da Cunha
- Laboratório de Ciclo Celular - Instituto Butantan, São Paulo-SP, Brazil; Centro de Toxinas, Resposta Imune e Sinalização Celular (CeTICS), Instituto Butantan, São Paulo, Brazil.
| |
Collapse
|
2
|
Previously Unidentified Histone H1-Like Protein Is Involved in Cell Division and Ribosome Biosynthesis in Toxoplasma gondii. mSphere 2022; 7:e0040322. [PMID: 36468865 PMCID: PMC9769792 DOI: 10.1128/msphere.00403-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Chromatin dynamics can regulate all DNA-dependent processes. Access to DNA within chromatin is orchestrated mainly by histones and their posttranslational modifications (PTMs). Like other eukaryotes, the apicomplexan parasite Toxoplasma gondii encodes four canonical histones and five histone variants. In contrast, the linker histone (H1) has never been identified in apicomplexan parasites. In other eukaryotes, histone H1 compacts the chromatin by linking the nucleosome and increasing the DNA compaction. H1 is a multifunctional protein and can be involved in different steps of DNA metabolism or associated with protein complexes related to distinct biological processes. We have identified a novel protein in T. gondii ("TgH1-like") that, although lacking the globular domain of mammalian H1, is remarkably like the H1-like proteins of bacteria and trypanosomatids. Our results demonstrate that TgH1-like is a nuclear protein associated with chromatin and other histones. Curiously, TgH1-like is also in the nucleolus and associated with ribosomal proteins, indicating a versatile function in this parasite. Although knockout of the tgh1-like gene does not affect the cell cycle, it causes endopolygeny and asynchronous division. Interestingly, mutation of posttranslationally modified amino acids results in defects in cell division like those in the Δtgh1-like mutant, showing that these sites are important for protein function. Furthermore, in the bradyzoite stage, this protein is expressed only in dividing parasites, reinforcing its importance in cell division. Indeed, the absence of TgH1-like decreases compaction of peripheral chromatin, confirming its role in the chromatin modulation in T. gondii. IMPORTANCE Histone H1, or linker histone, is an important protein that binds to the nucleosome, aiding chromatin compaction. Here, we characterize for the first time a linker histone in T. gondii, named TgH1-like. It is a small and basic protein that corresponds only to the C-terminal portion of the human H1 but is similar to histone H1 from trypanosomatids and bacteria. TgH1-like is located in the nucleus, interacts with nucleosome histones, and acts in chromatin structure and cell division. Our findings show for the first time the presence of a histone H1 protein in an apicomplexan parasite and will provide new insights into cell division and chromatin dynamics in T. gondii and related parasites.
Collapse
|
3
|
Hao F, Mishra LN, Jaya P, Jones R, Hayes JJ. Identification and Analysis of Six Phosphorylation Sites Within the Xenopus laevis Linker Histone H1.0 C-Terminal Domain Indicate Distinct Effects on Nucleosome Structure. Mol Cell Proteomics 2022; 21:100250. [PMID: 35618225 PMCID: PMC9243160 DOI: 10.1016/j.mcpro.2022.100250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Revised: 05/01/2022] [Accepted: 05/20/2022] [Indexed: 11/25/2022] Open
Abstract
As a key structural component of the chromatin of higher eukaryotes, linker histones (H1s) are involved in stabilizing the folding of extended nucleosome arrays into higher-order chromatin structures and function as a gene-specific regulator of transcription in vivo. The H1 C-terminal domain (CTD) is essential for high-affinity binding of linker histones to chromatin and stabilization of higher-order chromatin structure. Importantly, the H1 CTD is an intrinsically disordered domain that undergoes a drastic condensation upon binding to nucleosomes. Moreover, although phosphorylation is a prevalent post-translational modification within the H1 CTD, exactly where this modification is installed and how phosphorylation influences the structure of the H1 CTD remains unclear for many H1s. Using novel mass spectrometry techniques, we identified six phosphorylation sites within the CTD of the archetypal linker histone Xenopus H1.0. We then analyzed nucleosome-dependent CTD condensation and H1-dependent linker DNA organization for H1.0 in which the phosphorylated serine residues were replaced by glutamic acid residues (phosphomimics) in six independent mutants. We find that phosphomimetics at residues S117E, S155E, S181E, S188E, and S192E resulted in a significant reduction in nucleosome-bound H1.0 CTD condensation compared with unphosphorylated H1.0, whereas S130E did not alter CTD structure. Furthermore, we found distinct effects among the phosphomimetics on H1-dependent linker DNA trajectory, indicating unique mechanisms by which this modification can influence H1 CTD condensation. These results bring to light a novel role for linker histone phosphorylation in directly altering the structure of nucleosome-bound H1 and a potential novel mechanism for its effects on chromatin structure and function.
Collapse
Affiliation(s)
- Fanfan Hao
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York, USA
| | - Laxmi N Mishra
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York, USA
| | - Prasoon Jaya
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York, USA; Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York, USA
| | | | - Jeffrey J Hayes
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York, USA.
| |
Collapse
|
4
|
Lima ARJ, de Araujo CB, Bispo S, Patané J, Silber AM, Elias MC, da Cunha JPC. Nucleosome landscape reflects phenotypic differences in Trypanosoma cruzi life forms. PLoS Pathog 2021; 17:e1009272. [PMID: 33497423 PMCID: PMC7864430 DOI: 10.1371/journal.ppat.1009272] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 02/05/2021] [Accepted: 01/04/2021] [Indexed: 11/25/2022] Open
Abstract
Trypanosoma cruzi alternates between replicative and nonreplicative life forms, accompanied by a shift in global transcription levels and by changes in the nuclear architecture, the chromatin proteome and histone posttranslational modifications. To gain further insights into the epigenetic regulation that accompanies life form changes, we performed genome-wide high-resolution nucleosome mapping using two T. cruzi life forms (epimastigotes and cellular trypomastigotes). By combining a powerful pipeline that allowed us to faithfully compare nucleosome positioning and occupancy, more than 125 thousand nucleosomes were mapped, and approximately 20% of them differed between replicative and nonreplicative forms. The nonreplicative forms have less dynamic nucleosomes, possibly reflecting their lower global transcription levels and DNA replication arrest. However, dynamic nucleosomes are enriched at nonreplicative regulatory transcription initiation regions and at multigenic family members, which are associated with infective-stage and virulence factors. Strikingly, dynamic nucleosome regions are associated with GO terms related to nuclear division, translation, gene regulation and metabolism and, notably, associated with transcripts with different expression levels among life forms. Finally, the nucleosome landscape reflects the steady-state transcription expression: more abundant genes have a more deeply nucleosome-depleted region at putative 5' splice sites, likely associated with trans-splicing efficiency. Taken together, our results indicate that chromatin architecture, defined primarily by nucleosome positioning and occupancy, reflects the phenotypic differences found among T. cruzi life forms despite the lack of a canonical transcriptional control context.
Collapse
Affiliation(s)
- Alex R. J. Lima
- Laboratório de Ciclo Celular, Instituto Butantan, São Paulo, Brazil
- Center of Toxins, Immune Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - Christiane B. de Araujo
- Laboratório de Ciclo Celular, Instituto Butantan, São Paulo, Brazil
- Center of Toxins, Immune Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - Saloe Bispo
- Laboratório de Ciclo Celular, Instituto Butantan, São Paulo, Brazil
- Center of Toxins, Immune Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - José Patané
- Laboratório de Ciclo Celular, Instituto Butantan, São Paulo, Brazil
- Center of Toxins, Immune Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil
| | - Ariel M. Silber
- Laboratory of Biochemistry of Tryps–LaBTryps, Department of Parasitology, Institute of Biomedical Sciences, Universidade de São Paulo, São Paulo, Brazil
| | - M. Carolina Elias
- Laboratório de Ciclo Celular, Instituto Butantan, São Paulo, Brazil
- Center of Toxins, Immune Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil
- * E-mail: (MCE); (JPCC)
| | - Julia P. C. da Cunha
- Laboratório de Ciclo Celular, Instituto Butantan, São Paulo, Brazil
- Center of Toxins, Immune Response and Cell Signaling (CeTICS), Instituto Butantan, São Paulo, Brazil
- * E-mail: (MCE); (JPCC)
| |
Collapse
|
5
|
Histone Modifications and Other Facets of Epigenetic Regulation in Trypanosomatids: Leaving Their Mark. mBio 2020; 11:mBio.01079-20. [PMID: 32873754 PMCID: PMC7468196 DOI: 10.1128/mbio.01079-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Histone posttranslational modifications (PTMs) modulate several eukaryotic cellular processes, including transcription, replication, and repair. Vast arrays of modifications have been identified in conventional eukaryotes over the last 20 to 25 years. While initial studies uncovered these primarily on histone tails, multiple modifications were subsequently found on the central globular domains as well. Histones are evolutionarily conserved across eukaryotes, and a large number of their PTMs and the functional relevance of these PTMs are largely conserved. Histone posttranslational modifications (PTMs) modulate several eukaryotic cellular processes, including transcription, replication, and repair. Vast arrays of modifications have been identified in conventional eukaryotes over the last 20 to 25 years. While initial studies uncovered these primarily on histone tails, multiple modifications were subsequently found on the central globular domains as well. Histones are evolutionarily conserved across eukaryotes, and a large number of their PTMs and the functional relevance of these PTMs are largely conserved. Trypanosomatids, however, are early diverging eukaryotes. Although possessing all four canonical histones as well as several variants, their sequences diverge from those of other eukaryotes, particularly in the tails. Consequently, the modifications they carry also vary. Initial analyses almost 15 years ago suggested that trypanosomatids possessed a smaller collection of histone modifications. However, exhaustive high resolution mass spectrometry analyses in the last few years have overturned this belief, and it is now evident that the “histone code” proposed by Allis and coworkers in the early years of this century is as complex in these organisms as in other eukaryotes. Trypanosomatids cause several diseases, and the members of this group of organisms have varied lifestyles, evolving diverse mechanisms to evade the host immune system, some of which have been found to be principally controlled by epigenetic mechanisms. This minireview aims to acquaint the reader with the impact of histone PTMs on trypanosomatid cellular processes, as well as other facets of trypanosomatid epigenetic regulation, including the influence of three-dimensional (3D) genome architecture, and discusses avenues for future investigations.
Collapse
|
6
|
Zuma AA, Santos JDO, Mendes I, de Souza W, Machado CR, Motta MCM. Chaetocin-A histone methyltransferase inhibitor-Impairs proliferation, arrests cell cycle and induces nucleolar disassembly in Trypanosoma cruzi. Acta Trop 2017; 170:149-160. [PMID: 28185826 DOI: 10.1016/j.actatropica.2017.02.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 01/12/2017] [Accepted: 02/06/2017] [Indexed: 12/15/2022]
Abstract
The Trypanosomatidae family includes pathogenic species of medical and veterinary interest. Chagas disease is endemic in Latin America, and about 8 million people are infected worldwide. There is a need for more effective drugs for the acute, undetermined and chronic phases of the disease that, in addition, do not cause side effects, stimulating the search for identification of new drug targets, as well as new chemotherapeutic targets. Trypanosomatids contain characteristic structures, such as the nucleus that undergoes a closed mitosis without chromosome formation and variations of chromatin packing in the different protozoa developmental stages. The nuclear DNA is condensed by histones that suffer post-translational modifications, such as addition of methyl groups by histone methyltransferases (MHT) and addition of acetyl groups by acetyltransferases. These processes modulate gene expression and chromatin organization, which are crucial to transcription, replication, repair and recombination. In the present study, the effects of chaetocin, a HMT inhibitor, on T. cruzi epimastigote proliferation, viability, ultrastructure and cell cycle were investigated. Results indicate that chaetocin promoted irreversible inhibition of protozoa growth, evident unpacking of nuclear heterochromatin and intense nucleolus fragmentation, which is associated with parasite cell cycle arrest and RNA transcription blockage. Taken together, data obtained with chaetocin treatment stimulate the use of histone methyltransferase inhibitors against pathogenic trypanosomatids.
Collapse
|
7
|
Izzo A, Schneider R. The role of linker histone H1 modifications in the regulation of gene expression and chromatin dynamics. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1859:486-95. [PMID: 26348411 DOI: 10.1016/j.bbagrm.2015.09.003] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 08/07/2015] [Accepted: 09/02/2015] [Indexed: 12/27/2022]
Abstract
BACKGROUND Linker histone H1 is a structural component of chromatin. It exists as a family of related proteins known as variants and/or subtypes. H1.1, H1.2, H1.3, H1.4 and H1.5 are present in most somatic cells, whereas other subtypes are mainly expressed in more specialized cells. SCOPE OF REVIEW H1 subtypes have been shown to have unique functions in chromatin structure and dynamics. This can occur at least in part via specific post-translational modifications of distinct H1 subtypes. However, while core histone modifications have been extensively studied, our knowledge of H1 modifications and their molecular functions has remained for a long time limited to phosphorylation. In this review we discuss the current state of knowledge of linker histone H1 modifications and where possible highlight functional differences in the modifications of distinct H1 subtypes. MAJOR CONCLUSIONS AND GENERAL SIGNIFICANCE H1 histones are intensely post-translationally modified. These modifications are located in the N- and C-terminal tails as well as within the globular domain. Recently, advanced mass spectrometrical analysis revealed a large number of novel histone H1 subtype specific modification sites and types. H1 modifications include phosphorylation, acetylation, methylation, ubiquitination, and ADP ribosylation. They are involved in the regulation of all aspects of linker histone functions, however their mechanism of action is often only poorly understood. Therefore systematic functional characterization of H1 modifications will be necessary in order to better understand their role in gene regulation as well as in higher-order chromatin structure and dynamics.
Collapse
Affiliation(s)
- Annalisa Izzo
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS UMR 7104, INSERM U 964, Université de Strasbourg, 67404 Illkirch, France
| | - Robert Schneider
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS UMR 7104, INSERM U 964, Université de Strasbourg, 67404 Illkirch, France.
| |
Collapse
|
8
|
Padmanabhan PK, Polidoro RB, Barteneva NS, Gazzinelli RT, Burleigh BA. Transient transfection and expression of foreign and endogenous genes in the intracellular stages of Trypanosoma cruzi. Mol Biochem Parasitol 2015; 198:100-3. [PMID: 25712770 DOI: 10.1016/j.molbiopara.2015.02.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 02/06/2015] [Accepted: 02/14/2015] [Indexed: 11/17/2022]
Abstract
The capacity for rapid localization of epitope-tagged or fluorescent fusion proteins in cells is an important tool for biological discovery and functional analysis. For Trypanosoma cruzi, the protozoan parasite that causes human Chagas disease, visualization of ectopically-expressed proteins in the clinically-relevant mammalian stages is hindered by the necessity to first perform transfection and lengthy selection procedures in the insect vector form of the parasite. Here, we demonstrate the ability to by-pass the insect stage with the delivery of plasmid DNA to non-dividing, tissue culture trypomastigotes such that upon host cell infection, transgenes are expressed and rapidly localized in intracellular T. cruzi amastigotes. The inclusion of a sorting step prior to host cell infection by trypomastigotes greatly enriches (>90%) the number of transgene-expressing amastigotes observed in mammalian host cells. This is a significant methodological advance that has the potential to accelerate the pace of discovery in the Chagas disease field.
Collapse
Affiliation(s)
- Prasad K Padmanabhan
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 665 Huntington Ave, Boston, MA 02115, United States
| | - Rafael B Polidoro
- Departamento de Bioquímica e Imunologia and Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, Minas Gerais, Brazil
| | - Natasha S Barteneva
- Cellular and Molecular Medicine Program, Boston Children's Hospital and Department of Pediatrics, Harvard Medical School, 200 Longwood Ave, Boston, MA 02115, United States
| | - Ricardo T Gazzinelli
- Departamento de Bioquímica e Imunologia and Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, Minas Gerais, Brazil; Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Av. Augusto de Lima 1715, 30190-002 Belo Horizonte, MG, Brazil; Division of Infectious Disease and Immunology, University of Massachusetts Medical School, 364 Plantation St, Worcester, MA 01605, United States
| | - Barbara A Burleigh
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 665 Huntington Ave, Boston, MA 02115, United States.
| |
Collapse
|
9
|
Insights into dynamic mitotic chromatin organization through the NIMA kinase suppressor SonC, a chromatin-associated protein involved in the DNA damage response. Genetics 2013; 196:177-95. [PMID: 24214344 DOI: 10.1534/genetics.113.156745] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The nuclear pore complex proteins SonA and SonB, the orthologs of mammalian RAE1 and NUP98, respectively, were identified in Aspergillus nidulans as cold-sensitive suppressors of a temperature-sensitive allele of the essential mitotic NIMA kinase (nimA1). Subsequent analyses found that sonB1 mutants exhibit temperature-dependent DNA damage sensitivity. To understand this pathway further, we performed a genetic screen to isolate additional conditional DNA damage-sensitive suppressors of nimA1. We identified two new alleles of SonA and four intragenic nimA mutations that suppress the temperature sensitivity of the nimA1 mutant. In addition, we identified SonC, a previously unstudied binuclear zinc cluster protein involved with NIMA and the DNA damage response. Like sonA and sonB, sonC is an essential gene. SonC localizes to nuclei and partially disperses during mitosis. When the nucleolar organizer region (NOR) undergoes mitotic condensation and removal from the nucleolus, nuclear SonC and histone H1 localize in a mutually exclusive manner with H1 being removed from the NOR region and SonC being absent from the end of the chromosome beyond the NOR. This region of chromatin is adjacent to a cluster of nuclear pore complexes to which NIMA localizes last during its progression around the nuclear envelope during initiation of mitosis. The results genetically extend the NIMA regulatory system to include a protein with selective large-scale chromatin location observed during mitosis. The data suggest a model in which NIMA and SonC, its new chromatin-associated suppressor, might help to orchestrate global chromatin states during mitosis and the DNA damage response.
Collapse
|
10
|
Moretti NS, Schenkman S. Chromatin modifications in trypanosomes due to stress. Cell Microbiol 2013; 15:709-17. [DOI: 10.1111/cmi.12111] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2012] [Revised: 01/08/2013] [Accepted: 01/10/2013] [Indexed: 01/02/2023]
Affiliation(s)
- Nilmar Silvio Moretti
- Department of Microbiology, Immunology and Parasitology; Federal University of São Paulo; São Paulo Brazil
| | - Sergio Schenkman
- Department of Microbiology, Immunology and Parasitology; Federal University of São Paulo; São Paulo Brazil
| |
Collapse
|
11
|
Povelones ML, Gluenz E, Dembek M, Gull K, Rudenko G. Histone H1 plays a role in heterochromatin formation and VSG expression site silencing in Trypanosoma brucei. PLoS Pathog 2012; 8:e1003010. [PMID: 23133390 PMCID: PMC3486875 DOI: 10.1371/journal.ppat.1003010] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 09/20/2012] [Indexed: 11/30/2022] Open
Abstract
The African sleeping sickness parasite Trypanosoma brucei evades the host immune system through antigenic variation of its variant surface glycoprotein (VSG) coat. Although the T. brucei genome contains ∼1500 VSGs, only one VSG is expressed at a time from one of about 15 subtelomeric VSG expression sites (ESs). For antigenic variation to work, not only must the vast VSG repertoire be kept silent in a genome that is mainly constitutively transcribed, but the frequency of VSG switching must be strictly controlled. Recently it has become clear that chromatin plays a key role in silencing inactive ESs, thereby ensuring monoallelic expression of VSG. We investigated the role of the linker histone H1 in chromatin organization and ES regulation in T. brucei. T. brucei histone H1 proteins have a different domain structure to H1 proteins in higher eukaryotes. However, we show that they play a key role in the maintenance of higher order chromatin structure in bloodstream form T. brucei as visualised by electron microscopy. In addition, depletion of histone H1 results in chromatin becoming generally more accessible to endonucleases in bloodstream but not in insect form T. brucei. The effect on chromatin following H1 knock-down in bloodstream form T. brucei is particularly evident at transcriptionally silent ES promoters, leading to 6–8 fold derepression of these promoters. T. brucei histone H1 therefore appears to be important for the maintenance of repressed chromatin in bloodstream form T. brucei. In particular H1 plays a role in downregulating silent ESs, arguing that H1-mediated chromatin functions in antigenic variation in T. brucei. Trypanosoma brucei causes African sleeping sickness, endemic to sub-Saharan Africa. Bloodstream form T. brucei is covered with a dense coat of variant surface glycoprotein (VSG). Only one VSG is expressed at a time out of a vast repertoire of ∼1500 VSGs. The active VSG is transcribed in a telomeric VSG expression site (ES), and VSG switching allows immune evasion. Exactly how monoallelic exclusion of VSG ESs operates, and how switching between ESs is mediated remains mysterious, although epigenetics and chromatin structure clearly play a major role. The linker histone H1 is thought to orchestrate higher order chromatin structure in eukaryotes, but its exact function is unclear. We investigated the role of histone H1 in the regulation of antigenic variation in T. brucei. We show that histone H1 is associated with chromatin and is required for higher order chromatin structure. Depletion of histone H1 results in derepression of silent VSG ES promoters, indicating that H1-mediated chromatin functions in antigenic variation in T. brucei.
Collapse
Affiliation(s)
- Megan L. Povelones
- Division of Cell and Molecular Biology, Imperial College London, South Kensington, London, United Kingdom
| | - Eva Gluenz
- The Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Marcin Dembek
- Division of Cell and Molecular Biology, Imperial College London, South Kensington, London, United Kingdom
| | - Keith Gull
- The Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Gloria Rudenko
- Division of Cell and Molecular Biology, Imperial College London, South Kensington, London, United Kingdom
- * E-mail:
| |
Collapse
|
12
|
Schenkman S, Pascoalino BDS, Nardelli SC. Nuclear structure of Trypanosoma cruzi. ADVANCES IN PARASITOLOGY 2011; 75:251-83. [PMID: 21820560 DOI: 10.1016/b978-0-12-385863-4.00012-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The presence of nucleus in living organisms characterizes the Eukaryote domain. The nucleus compartmentalizes the genetic material surrounded by a double membrane called nuclear envelope. The nucleus has been observed since the advent of the light microscope, and sub-compartments such as nucleoli, diverse nuclear bodies and condensed chromosomes have been later recognized, being part of highly organized and dynamic structure. The significance and function of such organization has increased with the understanding of transcription, replication, DNA repair, recombination processes. It is now recognized as consequence of adding complexity and regulation in more complex eukaryotic cells. Here we provide a description of the actual stage of knowledge of the nuclear structure of Trypanosoma cruzi. As an early divergent eukaryote, it presents unique and/or reduced events of DNA replication, transcription and repair as well as RNA processing and transport to the cytosol. Nevertheless, it shows peculiar structure changes accordingly to the cell cycle and stage of differentiation. T. cruzi proliferates only as epimastigote and amastigote stages, and when these forms differentiate in trypomastigote forms, their cell cycle is arrested. This arrested stage is capable of invading mammalian cells and of surviving harsh conditions, such as the gut of the insect vector and mammalian macrophages. Transcription and replication decrease during transformation in trypomastigotes implicating large alterations in the nuclear structure. Recent evidences also suggest that T. cruzi nucleus respond to oxidative and nutritional stresses. Due to the phylogenetic proximity with other well-known trypanosomes, such as Trypanosoma brucei and Leishmania major, they are expected to have similar nuclear organization, although differences are noticed due to distinct life cycles, cellular organizations and the specific adaptations for surviving in different host environments. Therefore, the general features of T. cruzi nuclear structure regarding unique characteristics of this protozoan parasite will be described.
Collapse
Affiliation(s)
- Sergio Schenkman
- Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de São Paulo, São Paulo, Brazil
| | | | | |
Collapse
|
13
|
Abstract
Trypanosomes are a group of protozoan eukaryotes, many of which are major parasites of humans and livestock. The genomes of trypanosomes and their modes of gene expression differ in several important aspects from those of other eukaryotic model organisms. Protein-coding genes are organized in large directional gene clusters on a genome-wide scale, and their polycistronic transcription is not generally regulated at initiation. Transcripts from these polycistrons are processed by global trans-splicing of pre-mRNA. Furthermore, in African trypanosomes, some protein-coding genes are transcribed by a multifunctional RNA polymerase I from a specialized extranucleolar compartment. The primary DNA sequence of the trypanosome genomes and their cellular organization have usually been treated as separate entities. However, it is becoming increasingly clear that in order to understand how a genome functions in a living cell, we will need to unravel how the one-dimensional genomic sequence and its trans-acting factors are arranged in the three-dimensional space of the eukaryotic nucleus. Understanding this cell biology of the genome will be crucial if we are to elucidate the genetic control mechanisms of parasitism. Here, we integrate the concepts of nuclear architecture, deduced largely from studies of yeast and mammalian nuclei, with recent developments in our knowledge of the trypanosome genome, gene expression, and nuclear organization. We also compare this nuclear organization to those in other systems in order to shed light on the evolution of nuclear architecture in eukaryotes.
Collapse
|
14
|
Nucleolar localization/retention signal is responsible for transient accumulation of histone H2B in the nucleolus through electrostatic interactions. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:27-38. [PMID: 21095207 DOI: 10.1016/j.bbamcr.2010.11.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 10/24/2010] [Accepted: 11/10/2010] [Indexed: 11/21/2022]
Abstract
The majority of known nuclear proteins are highly mobile. The molecular mechanisms by which they accumulate inside stable compartments that are not separated from the nucleoplasm by membranes are obscure. The compartmental retention of some proteins is associated with their biological function; however, some protein interactions within distinct nuclear structures may be non-specific. The non-specific retention may lead to the accumulation of proteins in distinct structural domains, even if the protein does not function inside this domain. In this study, we have shown that histone H2B-EGFP initially accumulated in the nucleolus after ectopic expression, and then gradually incorporated into the chromatin to leave only a small amount of nucleolus-bound histone that was revealed by removing chromatin-bound proteins with DNase I treatment. Nucleolar histone H2B had several characteristics: (i) it preferentially bound to granular component of the nucleolus and interacted with RNA or RNA-containing nucleolar components; (ii) it freely exchanged between the nucleolus and nucleoplasm; (iii) it associated with the nuclear matrix; and (iv) it bound to interphase prenuclear bodies that formed after hypotonic treatment. The region in histone H2B that acts as a nucleolar localization/retention signal (NoRS) was identified. This signal overlapped with a nuclear localization signal (NLS), which appears to be the primary function of this region. The NoRS activity of this region was non-specific, but the molecular mechanism was probably similar to the NoRSs of other nucleolar proteins. All known NoRSs are enriched with basic amino acids, and we demonstrated that positively charged motifs (nona-arginine (R9) and nona-lysine (K9)) were sufficient for the nucleolar accumulation of EGFP. Also, the correlation between measured NoRS activity and the predicted charge was observed. Thus, NoRSs appear to achieve their function through electrostatic interactions with the negatively charged components of the nucleolus. Though these interactions are non-specific, the functionally unrelated retention of a protein can increase the probability of its interaction with specific and functionally related binding sites.
Collapse
|
15
|
Abstract
RNA interference (RNAi) is defined as the mechanism through which double-stranded RNA (dsRNA) triggers degradation of homologous transcripts. Besides providing an invaluable tool to downregulate gene expression in a variety of organisms, it is now evident that RNAi acts beyond the cytoplasm and is involved in a variety of gene-silencing phenomena in the nucleus. In the present work we review the current status of the knowledge about RNAi in protozoan parasites that belong to the Trypanosoma genus and have medical relevance. While RNAi was first discovered in Trypanosoma brucei, it became evident that other members of the same genus of organisms, namely Trypanosoma cruzi, does not possess RNAi, probably due to the lack of Ago protein analogs in their genomes. We will discuss the genome organization of Trypanosoma cruzi and propose that the absence of both RNAi and gene promoters is symptomatic of alternative epigenetic controls in this parasite orchestrated by parasite-host interactions. Whereas in Trypanosoma brucei, RNAi and other epigenetic controls dictate alternative transcriptional programs critical for virulence.
Collapse
|