scholarly journals Opposing Transcriptional Mechanisms Regulate Toxoplasma Development

mSphere ◽  
2017 ◽  
Vol 2 (1) ◽  
Author(s):  
Dong-Pyo Hong ◽  
Joshua B. Radke ◽  
Michael W. White
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Immune System ◽  
Molecular Basis ◽  
Cyst Formation ◽  
Molecular Composition ◽  
Tissue Cyst ◽  
Developmental Pathway ◽  
Clinical Consequences ◽  
Cyst Development

ABSTRACT Toxoplasma infections are lifelong because of the development of the bradyzoite tissue cyst, which is effectively invisible to the immune system. Despite the important clinical consequences of this developmental pathway, the molecular basis of the switch mechanisms that control tissue cyst formation is still poorly understood. Significant changes in gene expression are associated with tissue cyst development, and ApiAP2 transcription factors are an important mechanism regulating this developmental transcriptome. However, the molecular composition of these ApiAP2 complexes and the operating principles of ApiAP2 mechanisms are not well defined. Here we establish that competing ApiAP2 transcriptional mechanisms operate to regulate this clinically important developmental pathway. The Toxoplasma biology that underlies human chronic infection is developmental conversion of the acute tachyzoite stage into the latent bradyzoite stage. We investigated the roles of two alkaline-stress-induced ApiAP2 transcription factors, AP2IV-3 and AP2IX-9, in bradyzoite development. These factors were expressed in two overlapping waves during bradyzoite development, with AP2IX-9 increasing expression earlier than AP2IV-3, which peaked as AP2IX-9 expression was declining. Disruption of the AP2IX-9 gene enhanced, while deletion of AP2IV-3 gene decreased, tissue cyst formation, demonstrating that these factors have opposite functions in bradyzoite development. Conversely, conditional overexpression of FKBP-modified AP2IX-9 or AP2IV-3 with the small molecule Shield 1 had a reciprocal effect on tissue cyst formation, confirming the conclusions of the knockout experiments. The AP2IX-9 repressor and AP2IV-3 activator tissue cyst phenotypes were borne out in gene expression studies that determined that many of the same bradyzoite genes were regulated in an opposite manner by these transcription factors. A common gene target was the canonical bradyzoite marker BAG1, and mechanistic experiments determined that, like AP2IX-9, AP2IV-3 regulates a BAG1 promoter-luciferase reporter and specifically binds the BAG1 promoter in parasite chromatin. Altogether, these results suggest that the AP2IX-9 transcriptional repressor and the AP2IV-3 transcriptional activator likely compete to control bradyzoite gene expression, which may permit Toxoplasma to better adapt to different tissue environments and select a suitable host cell for long-term survival of the dormant tissue cyst. IMPORTANCE Toxoplasma infections are lifelong because of the development of the bradyzoite tissue cyst, which is effectively invisible to the immune system. Despite the important clinical consequences of this developmental pathway, the molecular basis of the switch mechanisms that control tissue cyst formation is still poorly understood. Significant changes in gene expression are associated with tissue cyst development, and ApiAP2 transcription factors are an important mechanism regulating this developmental transcriptome. However, the molecular composition of these ApiAP2 complexes and the operating principles of ApiAP2 mechanisms are not well defined. Here we establish that competing ApiAP2 transcriptional mechanisms operate to regulate this clinically important developmental pathway.

scholarly journals Opposing transcriptional mechanisms regulateToxoplasmadevelopment

2016 ◽  
Author(s):  
Dong-Pyo Hong ◽  
Joshua B. Radke ◽  
Michael W. White
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Cyst Formation ◽  
Tissue Cyst ◽  
Luciferase Reporter ◽  
Alkaline Stress ◽  
Developmental Pathway ◽  
Reciprocal Effect ◽  
Gene Target ◽  
Term Survival

ABSTRACTTheToxoplasmabiology that underlies human chronic infection is developmental conversion of the acute tachyzoite stage into the latent bradyzoite stage. We investigated the role of two alkaline-stress induced ApiAP2 transcription factors, AP2IV-3 and AP2IX-9, in bradyzoite development. These factors were expressed in two overlapping waves during bradyzoite development with AP2IX-9 increasing expression earlier than AP2IV-3, which peaked as AP2IX-9 expression was declining. Disruption of the AP2IX-9 gene enhanced, while deletion of AP2IV-3 gene decreased tissue cyst formation demonstrating these factors have opposite functions in bradyzoite development. Conversely, conditional overexpression of FKBP-modified of AP2IX-9 or AP2IV-3 with the small molecule Shield 1 had a reciprocal effect on tissue cyst formation confirming the conclusions of the knockout experiments. The AP2IX-9 repressor and AP2IV-3 activator tissue cyst phenotypes were borne out in gene expression studies that determined many of the same bradyzoite genes were regulated in an opposite manner by these transcription factors. A common gene target was the canonical bradyzoite marker, BAG1, and mechanistic experiments determined that like AP2IX-9, AP2IV-3 regulates a BAG1 promoter-luciferase reporter and specific binds the BAG1 promoter in parasite chromatin. Altogether, these results suggest the AP2IX-9 transcriptional repressor and AP2IV-3 transcriptional activator likely compete to control bradyzoite gene expression, which may permitToxoplasmato better adapt to different tissue environments and select a suitable host cell for long term survival of the dormant tissue cyst.IMPORTANCEToxoplasmainfections are life-long due to the development of the bradyzoite tissue cyst, which is effectively invisible to the immune system. Despite the important clinical consequences of this developmental pathway, the molecular basis of the switch mechanisms that control formation of the tissue cyst is still poorly understood. Significant changes in gene expression are associated with tissue cyst development and ApiAP2 transcription factors are an important mechanism regulating this developmental transcriptome. However, the molecular composition of these ApiAP2 mechanisms are not well defined and the operating principles of ApiAP2 mechanisms are poorly understood. Here we establish that competing ApiAP2 transcriptional mechanisms operate to regulate this clinically important developmental pathway.

scholarly journals Toxoplasma gondii AP2IX-4 Regulates Gene Expression during Bradyzoite Development

mSphere ◽  
2017 ◽  
Vol 2 (2) ◽  
Author(s):  
Sherri Huang ◽  
Michael J. Holmes ◽  
Joshua B. Radke ◽  
Dong-Pyo Hong ◽  
Ting-Kai Liu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Toxoplasma Gondii ◽  
Cyst Formation ◽  
Tissue Cyst ◽  
Stress Induction ◽  
Content Type ◽  
A Cell ◽  
Transitional Forms ◽  
Mouse Model Of Infection ◽  
Cyst Development

ABSTRACT Toxoplasma gondii is a single-celled parasite that persists in its host as a transmissible tissue cyst. How the parasite converts from its replicative form to the bradyzoites housed in tissue cysts is not well understood, but the process clearly involves changes in gene expression. Here we report that parasites lacking a cell cycle-regulated transcription factor called AP2IX-4 display reduced frequencies of tissue cyst formation in culture and in a mouse model of infection. Parasites missing AP2IX-4 lose the ability to regulate bradyzoite genes during tissue cyst development. Expressed in developing bradyzoites still undergoing division, AP2IX-4 may serve as a useful marker in the study of transitional forms of the parasite. Toxoplasma gondii is a protozoan parasite of great importance to human and animal health. In the host, this obligate intracellular parasite persists as a tissue cyst that is imperceptible to the immune response and unaffected by current therapies. The tissue cysts facilitate transmission through predation and give rise to chronic cycles of toxoplasmosis in immunocompromised patients. Transcriptional changes accompany conversion of the rapidly replicating tachyzoites into the encysted bradyzoites, and yet the mechanisms underlying these alterations in gene expression are not well defined. Here we show that AP2IX-4 is a nuclear protein exclusively expressed in tachyzoites and bradyzoites undergoing division. Knockout of AP2IX-4 had no discernible effect on tachyzoite replication but resulted in a reduced frequency of tissue cyst formation following alkaline stress induction—a defect that is reversible by complementation. AP2IX-4 has a complex role in regulating bradyzoite gene expression, as the levels of many bradyzoite mRNAs dramatically increased beyond those seen under conditions of normal stress induction in AP2IX-4 knockout parasites exposed to alkaline media. The loss of AP2IX-4 also resulted in a modest virulence defect and reduced cyst burden in chronically infected mice, which was reversed by complementation. These findings illustrate that the transcriptional mechanisms responsible for tissue cyst development operate across the intermediate life cycle from the dividing tachyzoite to the dormant bradyzoite. IMPORTANCE Toxoplasma gondii is a single-celled parasite that persists in its host as a transmissible tissue cyst. How the parasite converts from its replicative form to the bradyzoites housed in tissue cysts is not well understood, but the process clearly involves changes in gene expression. Here we report that parasites lacking a cell cycle-regulated transcription factor called AP2IX-4 display reduced frequencies of tissue cyst formation in culture and in a mouse model of infection. Parasites missing AP2IX-4 lose the ability to regulate bradyzoite genes during tissue cyst development. Expressed in developing bradyzoites still undergoing division, AP2IX-4 may serve as a useful marker in the study of transitional forms of the parasite.

scholarly journals Transcriptional repression by ApiAP2 factors is central to chronic toxoplasmosis

2017 ◽  
Author(s):  
Joshua B. Radke ◽  
Danielle Worth ◽  
Dong-Pyo Hong ◽  
Sherri Huang ◽  
William J. Sullivan ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcriptional Repression ◽  
Chronic Infection ◽  
Parasitophorous Vacuole ◽  
Acute Infection ◽  
Cyst Formation ◽  
Tissue Cyst ◽  
Genetic Lineages ◽  
Inflammatory Monocytes ◽  
Bradyzoite Differentiation

AbstractBradyzoite differentiation is marked by major changes in gene expression resulting in a parasite that expresses a new repertoire of surface antigens hidden inside a modified parasitophorous vacuole called the tissue cyst. The factors that control this important life cycle transition are not well understood. Here we describe an importantToxoplasmatranscriptional repressor mechanism controlling bradyzoite differentiation that operates exclusively in the tachyzoite stage. The ApiAP2 factor, AP2IV-4, is a nuclear factor dynamically expressed in late S phase through mitosis/cytokinesis of the tachyzoite cell cycle. Remarkably, deletion of the AP2IV-4 locus resulted in the increased expression of bradyzoite mRNAs in replicating tachyzoites, and in two different genetic lineages we confirmed the misexpression of tissue cyst wall components (e.g. BPK1, MCP4, CST1) and the bradyzoite surface antigen SRS9 in the tachyzoite stage. In the murine animal model, the loss of AP2IV-4 had profound biological consequences. Type II prugniaud strain parasites lacking AP2IV-4 were unable to form tissue cysts in brain tissue and the absence of this factor also recruited a potent immune response characterized by increases inflammatory monocytes, IFN-γ and higher numbers of both CD8+ and CD4+ T-cells. Altogether, these results indicate that suppression of bradyzoite antigens by AP2IV-4 during acute infection is required forToxoplasmato establish a chronic infection in the immune-competent host.Author SummaryTheToxoplasmabiology that underlies the establishment of a chronic infection is developmental conversion of the acute tachyzoite stage into the latent bradyzoite-tissue cyst stage. Despite the important clinical consequences of this developmental pathway, the molecular basis of the switch mechanisms that control formation of the tissue cyst is still poorly understood. A fundamental feature of tissue cyst formation is the expression of bradyzoite-specific genes. Here we show the transcription factor AP2IV-4 directly silences bradyzoite mRNA and protein expression in the acute tachyzoite stage demonstrating that developmental control of tissue cyst formation is as much about when not to express bradyzoite genes as it is about when to activate them. Loosing the suppression of bradyzoite gene expression in the acute tachyzoite stage caused by deleting AP2IV-4 blocked the establishment of chronic disease in healthy animals through the pre-arming of the immune system suggesting a possible strategy for preventing chronicToxoplasmainfections.

scholarly journals A New Insight into Flowering Regulation: Molecular Basis of Flowering Initiation in Magnolia × soulangeana ‘Changchun’

Genes ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 15 ◽  
Author(s):  
Zheng Jiang ◽  
Liyong Sun ◽  
Qiang Wei ◽  
Ye Ju ◽  
Xuan Zou ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Molecular Basis ◽  
Woody Plants ◽  
Expression Patterns ◽  
Gene Expression Patterns ◽  
Flower Buds ◽  
Flowering Initiation ◽  
Specific Regulation ◽  
Flowering Process

Magnolia × soulangeana ‘Changchun’ are trees that bloom in spring and summer respectively after flower bud differentiation. Here, we use phenological and morphological observation and RNA-seq technology to study the molecular basis of flowering initiation in ‘Changchun’. During the process of flowering initiation in spring and summer, the growth of expanded flower buds increased significantly, and their shape was obviously enlarged, which indicated that flowering was initiated. A total of 168,120 expressed genes were identified in spring and summer dormant and expanded flower buds, of which 11,687 genes showed significantly differential expression between spring and summer dormant and expanded flower buds. These differentially expressed genes (DEGs) were mainly involved in plant hormone signal transduction, metabolic processes, cellular components, binding, and catalytic activity. Analysis of differential gene expression patterns revealed that gibberellin signaling, and some transcription factors were closely involved in the regulation of spring and summer flowering initiation in ‘Changchun’. A qRT-PCR (quantitative Real Time Polymerase Chain Reaction) analysis showed that BGISEQ-500 sequencing platform could truly reflect gene expression patterns. It also verified that GID1B (GIBBERELLIN INSENSITIVE DWARF1 B), GID1C, SPL8 (SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 8), and GASA (GIBBERELLIC ACID-STIMULATED ARABIDOPSIS) family genes were expressed at high levels, while the expression of SPY (SPINDLY) was low during spring and summer flowering initiation. Meanwhile, the up- and down-regulated expression of, respectively, AGL6 (AGAMOUS-LIKE 6) and DREB3 (DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN 3), AG15, and CDF1 (CYCLIC DOF FACTOR 1) might also be involved in the specific regulation of spring and summer flowering initiation. Obviously, flowering initiation is an important stage of the flowering process in woody plants, involving the specific regulation of relevant genes and transcription factors. This study provides a new perspective for the regulation of the flowering process in perennial woody plants.

scholarly journals Toxoplasma gondiiAP2IX-4 regulates gene expression during bradyzoite development

2017 ◽  
Author(s):  
Sherri Huang ◽  
Michael J. Holmes ◽  
Joshua B. Radke ◽  
Dong-Pyo Hong ◽  
Ting-Kai Liu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Animal Health ◽  
Protozoan Parasite ◽  
Cyst Formation ◽  
Tissue Cyst ◽  
Alkaline Media ◽  
Alkaline Stress ◽  
Stress Induction ◽  
Reduced Frequency ◽  
Current Therapies

ABSTRACTToxoplasma gondiiis a protozoan parasite of great importance to human and animal health. In the host, this obligate intracellular parasite persists as a tissue cyst form that is invisible to the immune response and unaffected by current therapies. The tissue cysts facilitate transmission through predation and give rise to chronic cycles of toxoplasmosis in immune compromised patients. Transcriptional changes accompany conversion of the rapidly replicating tachyzoites into the encysted bradyzoites, yet the mechanisms underlying these alterations in gene expression are not well-defined. Here we show that AP2IX-4 is a nuclear protein exclusively expressed in tachyzoites and bradyzoites undergoing division. Knockout of AP2IX-4 had no discernible effect on tachyzoite replication, but resulted in a reduced frequency of tissue cyst formation following alkaline stress induction – a defect that is reversible by complementation. AP2IX-4 has a complex role in regulating bradyzoite gene expression, as many bradyzoite mRNAs dramatically increased beyond normal stress-induction in AP2IX-4 knockout parasites exposed to alkaline media. The loss of AP2IX-4 also resulted in a modest virulence defect and reduced cyst burden in chronically infected mice, which was also reversed by complementation. These findings illustrate that the transcriptional mechanisms responsible for tissue cyst development operate across the intermediate life cycle from the dividing tachyzoite to the dormant bradyzoite.

scholarly journals Nfat

2002 ◽  
Vol 156 (5) ◽  
pp. 771-774 ◽  
Author(s):  
Valerie Horsley ◽  
Grace K. Pavlath
Keyword(s):  
Gene Expression ◽  
T Cells ◽  
Transcription Factors ◽  
Immune System ◽  
Cell Types ◽  
Cytokine Gene Expression ◽  
Nuclear Factor ◽  
Cytokine Gene ◽  
Activated T Cells ◽  
Control Of Gene Expression

The nuclear factor of activated T cells (NFAT) proteins are a family of transcription factors whose activation is controlled by calcineurin, a Ca2+-dependent phosphatase. Originally identified in T cells as inducers of cytokine gene expression, NFAT proteins play varied roles in cells outside of the immune system. This review addresses the recent data implicating NFAT in the control of gene expression influencing the development and adaptation of numerous mammalian cell types.

scholarly journals T Cell Activation and Regulation of HIV-1: Same Effectors with Distinct Outcomes

1999 ◽  
Vol 10 (suppl c) ◽  
pp. 25C-32C ◽  
Author(s):  
Jean-François Fortin ◽  
Benoit Barbeau ◽  
Gilles A Robichaud ◽  
Michel J Tremblay
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Immune System ◽  
Virus Replication ◽  
T Cell Activation ◽  
Cell Activation ◽  
Molecular Mechanisms ◽  
Nuclear Factor ◽  
Cellular Transcription ◽  
Hiv 1

The molecular mechanisms that regulate the function of the immune system and human immunodeficiency virus type-1 (HIV-1) gene expression are diverse and complicated. However, replication of HIV-1 is controlled by many of the same regulatory signals that play a crucial role in the transcriptional regulation of the immune system. For example, the viral promoter, as is the case for the immune system, is subject to complex regulation by combinations of cellular transcription factors that may quantitatively and/or qualitatively differ depending on cell types (eg, macrophages versus T lymphocytes) and cell states (eg, undifferentiated versus differentiated or quiescent versus activated). The present review discusses the regulation of HIV-1 gene expression by nuclear factor-kappa Band nuclear factor of activated T cells, and proposes that selective interference of these two cellular transcription factors may be a route to abrogate virus replication without disrupting normal cellular functions. A better understanding of the regulation of HIV-1 gene expression is of utmost importance for the design of molecular approaches that will effectively abrogate virus replication and, ultimately, disease progression.

Nuclear Hormone Receptors Enable Macrophages and Dendritic Cells to Sense Their Lipid Environment and Shape Their Immune Response

2012 ◽  
Vol 92 (2) ◽  
pp. 739-789 ◽  
Author(s):  
Laszlo Nagy ◽  
Attila Szanto ◽  
Istvan Szatmari ◽  
Lajos Széles
Keyword(s):  
Gene Expression ◽  
Dendritic Cells ◽  
Transcription Factors ◽  
Retinoic Acid ◽  
Immune System ◽  
Nuclear Receptors ◽  
Cell Types ◽  
Retinoid X Receptor ◽  
Lipid Signaling ◽  
Acid Receptor

A key issue in the immune system is to generate specific cell types, often with opposing activities. The mechanisms of differentiation and subtype specification of immune cells such as macrophages and dendritic cells are critical to understand the regulatory principles and logic of the immune system. In addition to cytokines and pathogens, it is increasingly appreciated that lipid signaling also has a key role in differentiation and subtype specification. In this review we explore how intracellular lipid signaling via a set of transcription factors regulates cellular differentiation, subtype specification, and immune as well as metabolic homeostasis. We introduce macrophages and dendritic cells and then we focus on a group of transcription factors, nuclear receptors, which regulate gene expression upon receiving lipid signals. The receptors we cover are the ones with a recognized physiological function in these cell types and ones which heterodimerize with the retinoid X receptor. These are as follows: the receptor for a metabolite of vitamin A, retinoic acid: retinoic acid receptor (RAR), the vitamin D receptor (VDR), the fatty acid receptor: peroxisome proliferator-activated receptor γ (PPARγ), the oxysterol receptor liver X receptor (LXR), and their obligate heterodimeric partner, the retinoid X receptor (RXR). We discuss how they can get activated and how ligand is generated and eliminated in these cell types. We also explore how activation of a particular target gene contributes to biological functions and how the regulation of individual target genes adds up to the coordination of gene networks. It appears that RXR heterodimeric nuclear receptors provide these cells with a coordinated and interrelated network of transcriptional regulators for interpreting the lipid milieu and the metabolic changes to bring about gene expression changes leading to subtype and functional specification. We also show that these networks are implicated in various immune diseases and are amenable to therapeutic exploitation.

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