scholarly journals Histone Loaders CAF1 and HIRA Restrict Epstein-Barr Virus B-Cell Lytic Reactivation

mBio ◽  
2020 ◽  
Vol 11 (5) ◽  
Author(s):  
Yuchen Zhang ◽  
Chang Jiang ◽  
Stephen J. Trudeau ◽  
Yohei Narita ◽  
Bo Zhao ◽  
...  
Keyword(s):  
B Cells ◽  
Burkitt Lymphoma ◽  
Epstein Barr Virus ◽  
Chromatin Assembly ◽  
Lytic Cycle ◽  
Histone Chaperones ◽  
Viral Genomes ◽  
Barr Virus ◽  
Lytic Reactivation ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) infects 95% of adults worldwide and causes infectious mononucleosis. EBV is associated with endemic Burkitt lymphoma, Hodgkin lymphoma, posttransplant lymphomas, nasopharyngeal and gastric carcinomas. In these cancers and in most infected B-cells, EBV maintains a state of latency, where nearly 80 lytic cycle antigens are epigenetically suppressed. To gain insights into host epigenetic factors necessary for EBV latency, we recently performed a human genome-wide CRISPR screen that identified the chromatin assembly factor CAF1 as a putative Burkitt latency maintenance factor. CAF1 loads histones H3 and H4 onto newly synthesized host DNA, though its roles in EBV genome chromatin assembly are uncharacterized. Here, we found that CAF1 depletion triggered lytic reactivation and virion secretion from Burkitt cells, despite also strongly inducing interferon-stimulated genes. CAF1 perturbation diminished occupancy of histones 3.1 and 3.3 and of repressive histone 3 lysine 9 and 27 trimethyl (H3K9me3 and H3K27me3) marks at multiple viral genome lytic cycle regulatory elements. Suggestive of an early role in establishment of latency, EBV strongly upregulated CAF1 expression in newly infected primary human B-cells prior to the first mitosis, and histone 3.1 and 3.3 were loaded on the EBV genome by this time point. Knockout of CAF1 subunit CHAF1B impaired establishment of latency in newly EBV-infected Burkitt cells. A nonredundant latency maintenance role was also identified for the DNA synthesis-independent histone 3.3 loader histone regulatory homologue A (HIRA). Since EBV latency also requires histone chaperones alpha thalassemia/mental retardation syndrome X-linked chromatin remodeler (ATRX) and death domain-associated protein (DAXX), EBV coopts multiple host histone pathways to maintain latency, and these are potential targets for lytic induction therapeutic approaches. IMPORTANCE Epstein-Barr virus (EBV) was discovered as the first human tumor virus in endemic Burkitt lymphoma, the most common childhood cancer in sub-Saharan Africa. In Burkitt lymphoma and in 200,000 EBV-associated cancers per year, epigenetic mechanisms maintain viral latency, during which lytic cycle factors are silenced. This property complicated EBV’s discovery and facilitates tumor immunoevasion. DNA methylation and chromatin-based mechanisms contribute to lytic gene silencing. Here, we identified histone chaperones CAF1 and HIRA, which have key roles in host DNA replication-dependent and replication-independent pathways, respectively, as important for EBV latency. EBV strongly upregulates CAF1 in newly infected B-cells, where viral genomes acquire histone 3.1 and 3.3 variants prior to the first mitosis. Since histone chaperones ATRX and DAXX also function in maintenance of EBV latency, our results suggest that EBV coopts multiple histone pathways to reprogram viral genomes and highlight targets for lytic induction therapeutic strategies.

scholarly journals Histone loaders CAF1 and HIRA restrict Epstein-Barr virus B-cell lytic reactivation

2020 ◽  
Author(s):  
Yuchen Zhang ◽  
Chang Jiang ◽  
Stephen J. Trudeau ◽  
Yohei Narita ◽  
Bo Zhao ◽  
...  
Keyword(s):  
B Cells ◽  
Burkitt Lymphoma ◽  
Epstein Barr Virus ◽  
Chromatin Assembly ◽  
Lytic Cycle ◽  
Histone Chaperones ◽  
Viral Genomes ◽  
Barr Virus ◽  
Lytic Reactivation ◽  
Epstein Barr

ABSTRACTEpstein-Barr virus (EBV) infects 95% of adults worldwide and causes infectious mononucleosis. EBV is associated with endemic Burkitt lymphoma, Hodgkin lymphoma, post-transplant lymphomas, nasopharyngeal and gastric carcinomas. In these cancers and in most infected B-cells, EBV maintains a state of latency, where nearly 80 lytic cycle antigens are epigenetically suppressed. To gain insights into host epigenetic factors necessary for EBV latency, we recently performed a human genome-wide CRISPR screen that identified the chromatin assembly factor CAF1 as a putative Burkitt latency maintenance factor. CAF1 loads histones H3 and H4 onto newly synthesized host DNA, though its roles in EBV genome chromatin assembly are uncharacterized. Here, we identified that CAF1 depletion triggered lytic reactivation and transforming virion secretion from Burkitt cells, despite strongly also inducing interferon stimulated genes. CAF1 perturbation diminished occupancy of histones 3.1, 3.3 and repressive H3K9me3 and H3K27me3 marks at multiple viral genome lytic cycle regulatory elements. Suggestive of an early role in establishment of latency, EBV strongly upregulated CAF1 expression in newly infected primary human B-cells prior to the first mitosis, and histone 3.1 and 3.3 were loaded on the EBV genome by this timepoint. Knockout of CAF1 subunit CHAF1B impaired establishment of latency in newly EBV-infected Burkitt cells. A non-redundant latency maintenance role was also identified for the DNA synthesis-independent histone 3.3 loader HIRA. Since EBV latency also requires histone chaperones ATRX and DAXX, EBV coopts multiple host histone pathways to maintain latency, and these are potential targets for lytic induction therapeutic approaches.IMPORTANCEEpstein-Barr virus (EBV) was discovered as the first human tumor virus in endemic Burkitt lymphoma, the most common childhood cancer in sub-Saharan Africa. In Burkitt lymphoma and in 200,000 EBV-associated cancers per year, epigenetic mechanisms maintain viral latency, where lytic cycle factors are silenced. This property complicated EBV’s discovery and facilitates tumor immunoevasion. DNA methylation and chromatin-based mechanisms contribute to lytic gene silencing. Here, we identify histone chaperones CAF1 and HIRA, which have key roles in host DNA replication-dependent and replication independent pathways, respectively, are each important for EBV latency. EBV strongly upregulates CAF1 in newly infected B-cells, where viral genomes acquire histone 3.1 and 3.3 variants prior to the first mitosis. Since histone chaperones ATRX and DAXX also function in maintenance of EBV latency, our results suggest that EBV coopts multiple histone pathways to reprogram viral genomes and highlights targets for lytic induction therapeutic strategies.

scholarly journals Inhibition of Epstein-Barr Virus Lytic Reactivation by the Atypical Antipsychotic Drug Clozapine

Viruses ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 450 ◽  
Author(s):  
Abbie G. Anderson ◽  
Cullen B. Gaffy ◽  
Joshua R. Weseli ◽  
Kelly L. Gorres
Keyword(s):  
Atypical Antipsychotic ◽  
Antipsychotic Drug ◽  
Burkitt Lymphoma ◽  
Epstein Barr Virus ◽  
Lytic Cycle ◽  
Lymphoma Cells ◽  
Atypical Antipsychotic Drug ◽  
Barr Virus ◽  
Lytic Reactivation ◽  
Epstein Barr

Epstein–Barr virus (EBV), a member of the Herpesviridae family, maintains a lifelong latent infection in human B cells. Switching from the latent to the lytic phase of its lifecycle allows the virus to replicate and spread. The viral lytic cycle is induced in infected cultured cells by drugs such as sodium butyrate and azacytidine. Lytic reactivation can be inhibited by natural products and pharmaceuticals. The anticonvulsant drugs valproic acid and valpromide inhibit EBV in Burkitt lymphoma cells. Therefore, other drugs that treat neurological and psychological disorders were investigated for effects on EBV lytic reactivation. Clozapine, an atypical antipsychotic drug used to treat schizophrenia and bipolar disorder, was found to inhibit the reactivation of the EBV lytic cycle. Levels of the viral lytic genes BZLF1, BRLF1, and BMLF1 were decreased by treatment with clozapine in induced Burkitt lymphoma cells. The effects on viral gene expression were dependent on the dose of clozapine, yet cells were viable at an inhibitory concentration of clozapine. One metabolite of clozapine—desmethylclozapine—also inhibited EBV lytic reactivation, while another metabolite—clozapine-N-oxide—had no effect. These drugs may be used to study cellular pathways that control the viral lytic switch in order to develop treatments for diseases caused by EBV.

scholarly journals The Epstein-Barr virus (EBV) nuclear antigen 1 BamHI F promoter is activated on entry of EBV-transformed B cells into the lytic cycle.

1992 ◽  
Vol 66 (12) ◽  
pp. 7461-7468 ◽  
Author(s):  
A L Lear ◽  
M Rowe ◽  
M G Kurilla ◽  
S Lee ◽  
S Henderson ◽  
...  
Keyword(s):  
B Cells ◽  
Epstein Barr Virus ◽  
Lytic Cycle ◽  
Nuclear Antigen ◽  
Barr Virus ◽  
Epstein Barr

scholarly journals Antibodies to gp350/220 Enhance the Ability of Epstein-Barr Virus To Infect Epithelial Cells

2006 ◽  
Vol 80 (19) ◽  
pp. 9628-9633 ◽  
Author(s):  
Susan M. Turk ◽  
Ru Jiang ◽  
Liudmila S. Chesnokova ◽  
Lindsey M. Hutt-Fletcher
Keyword(s):  
B Cells ◽  
Nasopharyngeal Carcinoma ◽  
Epithelial Cells ◽  
Epstein Barr Virus ◽  
Lytic Cycle ◽  
Virus Envelope ◽  
Barr Virus ◽  
High Risk Populations ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) is a persistent, orally transmitted herpesvirus that replicates in B cells and epithelial cells and is associated with lymphoid and epithelial malignancies. The virus binds to CD21 on B cells via glycoprotein gp350/220 and infects efficiently. Infection of cultured epithelial cells has not typically been efficient but can occur in the absence of gp350/220 and CD21 and in vivo is thought to be important to the development of nasopharyngeal carcinoma. We report here that antibodies to gp350/220, which inhibit EBV infection of B cells, enhance infection of epithelial cells. The effect is not mediated by Fc receptor binding but is further enhanced by antibody cross-linking, which may patch gp350/220 in the virus envelope. Saliva from EBV-seropositive individuals has similar effects that can be reversed by depletion of antibody. The results are consistent with a model in which gp350/220 interferes with the access of other important players to the epithelial cell surface. The results may have implications for the development of nasopharyngeal carcinoma in high-risk populations in which elevated titers of antibody to EBV lytic cycle proteins are prognostic.

scholarly journals Knockout of Epstein-Barr Virus BPLF1 Retards B-Cell Transformation and Lymphoma Formation in Humanized Mice

mBio ◽  
2015 ◽  
Vol 6 (5) ◽  
Author(s):  
Christopher B. Whitehurst ◽  
Guangming Li ◽  
Stephanie A. Montgomery ◽  
Nathan D. Montgomery ◽  
Lishan Su ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Cell Transformation ◽  
Lytic Cycle ◽  
Humanized Mice ◽  
Barr Virus ◽  
Epstein Barr ◽  
Knockout Virus ◽  
Large B Cell

ABSTRACTBPLF1 of Epstein-Barr virus (EBV) is classified as a late lytic cycle protein but is also found in the viral tegument, suggesting its potential involvement at both initial and late stages of viral infection. BPLF1 possesses both deubiquitinating and deneddylating activity located in its N-terminal domain and is involved in processes that affect viral infectivity, viral DNA replication, DNA repair, and immune evasion. A recently constructed EBV BPLF1-knockout (KO) virus was used in conjunction with a humanized mouse model that can be infected with EBV, enabling the first characterization of BPLF1 functionin vivo. Results demonstrate that the BPLF1-knockout virus is approximately 90% less infectious than wild-type (WT) virus. Transformation of human B cells, a hallmark of EBV infection, was delayed and reduced with BPLF1-knockout virus. Humanized mice infected with EBV BPLF1-knockout virus showed less weight loss and survived longer than mice infected with equivalent infectious units of WT virus. Additionally, splenic tumors formed in 100% of mice infected with WT EBV but in only 25% of mice infected with BPLF1-KO virus. Morphological features of spleens containing tumors were similar to those in EBV-induced posttransplant lymphoproliferative disease (PTLD) and were almost identical to cases seen in human diffuse large B-cell lymphoma. The presence of EBV genomes was detected in all mice that developed tumors. The results implicate BPLF1 in human B-cell transformation and tumor formation in humanized mice.IMPORTANCEEpstein-Barr virus infects approximately 90% of the world's population and is the causative agent of infectious mononucleosis. EBV also causes aggressive lymphomas in individuals with acquired and innate immune disorders and is strongly associated with diffuse large B-cell lymphomas, classical Hodgkin lymphoma, Burkitt lymphoma, and nasopharyngeal carcinoma (NPC). Typically, EBV initially infects epithelial cells in the oropharynx, followed by a lifelong persistent latent infection in B-cells, which may develop into lymphomas in immunocompromised individuals. This work is the first of its kind in evaluating the effects of EBV's BPLF1 in terms of pathogenesis and lymphomagenesis in humanized mice and implicates BPLF1 in B-cell transformation and tumor development. Currently, there is no efficacious treatment for EBV, and therapeutic targeting of BPLF1 may lead to a new path to treatment for immunocompromised individuals or transplant recipients infected with EBV.

scholarly journals Interplay between the epigenetic enzyme lysine (K)-specific demethylase 2B and Epstein-Barr virus infection

2018 ◽  
Author(s):  
Romina C. Vargas-Ayala ◽  
Antonin Jay ◽  
Hector Hernandez-Vargas ◽  
Audrey Diederichs ◽  
Alexis Robitaille ◽  
...  
Keyword(s):  
Life Cycle ◽  
B Cells ◽  
Virus Infection ◽  
Burkitt Lymphoma ◽  
Epstein Barr Virus ◽  
Epstein Barr Virus Infection ◽  
Barr Virus ◽  
Epstein Barr ◽  
Barr Virus Infection

AbstractHistone modifier lysine (K)-specific demethylase 2B(KDM2B) plays a role in hematopoietic cells differentiation and its expression appears to be deregulated in certain cancers of hematological and lymphoid origins. We have previously found that KDM2B gene is differentially methylated in cell lines derived from the Epstein-Barr virus (EBV) associated endemic Burkitt’s lymphomas (eBL) compared to EBV negative sporadic BL cells. However, whether KDM2B plays a role in eBL development has never been previously demonstrated. Oncogenic viruses have been shown to hijack the host cell epigenome to complete their life cycle and to promote the transformation process by perturbing cell chromatin organization. Here we investigated whether EBV would alter KDM2B levels to enable its life cycle and promote B-cells transformation. We show that infection of B-cells with EBV leads to down-regulation of KDM2B levels. We also show that LMP1, one of the main EBV transforming proteins, induces increased DNMT1 recruitment to KDM2B gene and augments its methylation. By altering KDM2B levels and performing chromatin immunoprecipitation in EBV infected B-cells, we were able to show that KDM2B is recruited to the EBV gene promoters and inhibits their expression. Furthermore, forced KDM2B expression in immortalized B-cells led to altered mRNA levels of some differentiation-related genes. Our data show that EBV deregulates KDM2B levels through an epigenetic mechanism and provide evidence for a role of KDM2B in regulating virus and host cell gene expression, warranting further investigations to assess the role of KDM2B in the process of EBV-mediated lymphomagenesis.IMPORTANCE. In Africa, Epstein-Barr virus infection is associated with endemic Burkitt lymphoma, a pediatric cancer. The molecular events leading to its development are poorly understood compared to the sporadic Burkitt lymphoma. In a previous study, by analyzing the DNA methylation changes in endemic compared to sporadic Burkitt lymphomas cell lines, we identified several differential methylated genomic positions in proximity of genes with a potential role in cancer, among them the KDM2B gene. KDM2B encodes a histone H3 demethylase already shown to be involved in some hematological disorders. However, whether KDM2B plays a role in the development of Epstein-Barr virus-mediated lymphoma has never been investigated before. In this study we show that Epstein-Barr virus deregulates KDM2B expression and describe the underlying mechanisms. We also reveal a role of the demethylase in controlling viral and B-cells genes expression, thus highlighting a novel interaction between the virus and the cellular epigenome.

Early Stage of Epstein-Barr Virus Lytic Infection Leading to the “Starry Sky” Pattern Formation in Endemic Burkitt Lymphoma

2004 ◽  
Vol 128 (5) ◽  
pp. 549-552 ◽  
Author(s):  
Shuichi Fujita ◽  
Nathan Buziba ◽  
Atsushi Kumatori ◽  
Masachika Senba ◽  
Akira Yamaguchi ◽  
...  
Keyword(s):  
Burkitt Lymphoma ◽  
Epstein Barr Virus ◽  
Early Stage ◽  
Lytic Cycle ◽  
Lymphoma Cells ◽  
Tissue Samples ◽  
Barr Virus ◽  
Epstein Barr ◽  
Neoplastic Lymphocytes ◽  
Almost All

Abstract Context.—Burkitt lymphoma (BL) is histologically characterized by a “starry sky” appearance, representing scattered macrophages that have phagocytosed cell debris among proliferating lymphoma cells. As is well known, almost all the neoplastic cells of endemic BL are infected with Epstein-Barr virus (EBV). Previous studies have indicated that most of the EBV in B cells is latent, and few virus particles enter the lytic cycle. Objective.—To examine the histologic relationship between EBV infection stages and the formation of the starry sky pattern in African endemic BL tissues. Design.—Tissue samples from 44 patients with African endemic BL were examined with immunohistochemistry and in situ hybridization. We used EBV-encoded small RNA (EBER) as a marker of latent infection, and BamHI H left frame 1 (BHLF1) and BamHI Z EBV replication activator (ZEBRA) as lytic cycle markers. Results.—In all cases, signals for EBER were found in most neoplastic lymphocytes, and in 73% of cases, signals for BHLF1 and/or ZEBRA were recognized in the lymphoma cells within and around the lacunae in starry sky figures. The mean number of lacunae per unit area in cases positive for lytic cycle markers was significantly higher than that in negative cases (P < .001). Conclusions.—Our findings suggest that EBV-infected lymphoma cells in the lytic cycle, which eventually lapse into cell death, are phagocytosed prior to their rupture by macrophages that have migrated into the parenchyma. We emphasize that transition of EBV-infected lymphoma cells to the lytic cycle is one of the histomorphogenetic factors influencing the formation of starry sky pattern in endemic BL.

scholarly journals Upregulation of STAT3 Marks Burkitt Lymphoma Cells Refractory to Epstein-Barr Virus Lytic Cycle Induction by HDAC Inhibitors

2009 ◽  
Vol 84 (2) ◽  
pp. 993-1004 ◽  
Author(s):  
Derek Daigle ◽  
Cynthia Megyola ◽  
Ayman El-Guindy ◽  
Lyn Gradoville ◽  
David Tuck ◽  
...  
Keyword(s):  
Burkitt Lymphoma ◽  
Epstein Barr Virus ◽  
De Novo ◽  
Fundamental Problem ◽  
Single Cells ◽  
Lytic Cycle ◽  
Barr Virus ◽  
Refractory State ◽  
Epstein Barr

ABSTRACT A fundamental problem in studying the latent-to-lytic switch of Epstein-Barr virus (EBV) and the viral lytic cycle itself is the lack of a culture system fully permissive to lytic cycle induction. Strategies to target EBV-positive tumors by inducing the viral lytic cycle with chemical agents are hindered by inefficient responses to stimuli. In vitro, even in the most susceptible cell lines, more than 50% of cells latently infected with EBV are refractory to induction of the lytic cycle. The mechanisms underlying the refractory state are not understood. We separated lytic from refractory Burkitt lymphoma-derived HH514-16 cells after treatment with an HDAC inhibitor, sodium butyrate. Both refractory- and lytic-cell populations responded to the inducing stimulus by hyperacetylation of histone H3. However, analysis of host cell gene expression showed that specific cellular transcripts Stat3, Fos, and interleukin-8 (IL-8) were preferentially upregulated in the refractory-cell population, while IL-6 was upregulated in the lytic population. STAT3 protein levels were also substantially increased in refractory cells relative to untreated or lytic cells. This increase in de novo expression resulted primarily in unphosphorylated STAT3. Examination of single cells revealed that high levels of STAT3 were strongly associated with the refractory state. The refractory state is manifest in a unique subpopulation of cells that exhibits different cellular responses than do lytic cells exposed to the same stimulus. Identifying characteristics of cells refractory to lytic induction relative to cells that undergo lytic activation will be an important step in developing a better understanding of the regulation of the EBV latent to lytic switch.

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