scholarly journals Kaposi’s Sarcoma-Associated Herpesvirus Infection Induces the Expression of Neuroendocrine Genes in Endothelial Cells

2020 ◽  
Vol 94 (8) ◽  
Author(s):  
Mohanan Valiya Veettil ◽  
Gayathri Krishna ◽  
Arunava Roy ◽  
Anandita Ghosh ◽  
Dipanjan Dutta ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Proliferation ◽  
Endothelial Cells ◽  
Neuroendocrine Tumors ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Kshv Infection ◽  
Infected Cells ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi’s sarcoma-associated herpesvirus (KSHV) is etiologically associated with endothelial Kaposi’s sarcoma (KS) in immunocompromised individuals. KS lesion cells exhibit many similarities to neuroendocrine (NE) cancers, such as highly vascular and red/purple tumor lesions, spindle-shaped cells, an insignificant role for classic oncogenes in tumor development, the release of bioactive amines, and indolent growth of the tumors. However, the mechanistic basis for the similarity of KS lesion endothelial cells to neuroendocrine tumors remains unknown. Next-generation sequencing and bioinformatics analysis in the present study demonstrate that endothelial cells latently infected with KSHV express several neuronal and NE genes. De novo infection of primary dermal endothelial cells with live and UV-inactivated KSHV demonstrated that viral gene expression is responsible for the upregulation of five selected NE genes (adrenomedullin 2 [ADM2], histamine receptor H1 [HRH1], neuron-specific enolase [NSE] [ENO2], neuronal protein gene product 9.5 [PGP9.5], and somatostatin receptor 1 [SSTR1]). Immunofluorescence and immunohistochemistry examinations demonstrated the robust expression of the NE genes HRH1 and NSE/ENO2 in KSHV-infected KS tissue samples and KS visceral tissue microarrays. Further analysis demonstrated that KSHV latent open reading frame K12 (ORFK12) gene (kaposin A)-mediated decreased host REST/NRSF (RE1-silencing transcription factor/neuron-restrictive silencer factor) protein, a neuronal gene transcription repressor protein, is responsible for NE gene expression in infected endothelial cells. The NE gene expression observed in KSHV-infected cells was recapitulated in uninfected endothelial cells by the exogenous expression of ORFK12 and by the treatment of cells with the REST inhibitor X5050. When the neuroactive ligand-activating receptor HRH1 and inhibitory SSTR1 were knocked out by CRISPR, HRH1 knockout (KO) significantly inhibited cell proliferation, while SSTR1 KO induced cell proliferation, thus suggesting that HRH1 and SSTR1 probably counteract each other in regulating KSHV-infected endothelial cell proliferation. These results demonstrate that the similarity of KS lesion cells to neuroendocrine tumors is probably a result of KSHV infection-induced transformation of nonneuronal endothelial cells into cells with neuroendocrine features. These studies suggest a potential role of neuroendocrine pathway genes in the pathobiological characteristics of KSHV-infected endothelial cells, including a potential mechanism of escape from the host immune system by the expression of immunologically privileged neuronal-site NE genes, and NE genes could potentially serve as markers for KSHV-infected KS lesion endothelial cells as well as novel therapeutic targets to control KS lesions. IMPORTANCE Kaposi’s sarcoma-associated herpesvirus (KSHV) manipulates several cellular pathways for its survival advantage during its latency in the infected human host. Here, we demonstrate that KSHV infection upregulates the expression of genes related to neuronal and neuroendocrine (NE) functions that are characteristic of NE tumors, both in vitro and in KS patient tissues and the heterogeneity of neuroendocrine receptors having opposing roles in KSHV-infected cell proliferation. Induction of NE genes by KSHV could also provide a potential survival advantage, as the expression of proteins at immunologically privileged sites such as neurons on endothelial cells may be an avenue to escape host immune surveillance functions. The NE gene products identified here could serve as markers for KSHV-infected cells and could potentially serve as therapeutic targets to combat KSHV-associated KS.

scholarly journals Latency-Associated Nuclear Antigen of Kaposi's Sarcoma-Associated Herpesvirus (KSHV) Upregulates Survivin Expression in KSHV-Associated B-Lymphoma Cells and Contributes to Their Proliferation

2009 ◽  
Vol 83 (14) ◽  
pp. 7129-7141 ◽  
Author(s):  
Jie Lu ◽  
Subhash C. Verma ◽  
Masanao Murakami ◽  
Qiliang Cai ◽  
Pankaj Kumar ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Kaposi's Sarcoma ◽  
Survivin Expression ◽  
Kaposi’S Sarcoma ◽  
Nuclear Antigen ◽  
Mrna Levels ◽  
Survivin Promoter ◽  
Infected Cells ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Survivin is a master regulator of cell proliferation and cell viability and is highly expressed in most human tumors. The molecular network linked to survivin expression in tumors has not been completely elucidated. In this study, we show that latency-associated nuclear antigen (LANA), a multifunctional protein of Kaposi's sarcoma-associated herpesvirus (KSHV) that is found in Kaposi's sarcoma tumors, upregulates survivin expression and increases the proliferation of KSHV-infected B cells. Analysis of pathway-specific gene arrays showed that survivin expression was highly upregulated in BJAB cells expressing LANA. The mRNA levels of survivin were also upregulated in HEK 293 and BJAB cells expressing LANA. Similarly, protein levels of survivin were significantly higher in LANA-expressing, as well as KSHV-infected, cells. Survivin promoter activity assays identified GC/Sp1 and p53 cis-acting elements within the core promoter region as being important for LANA activity. Gel mobility shift assays revealed that LANA forms a complex with Sp1 or Sp1-like proteins bound to the GC/Sp1 box of the survivin promoter. In addition, a LANA/p53 complex bound to the p53 cis-acting element within the survivin promoter, indicating that upregulation of survivin expression can also occur through suppression of p53 function. Furthermore, immunohistochemistry analyses revealed that survivin expression was upregulated in KSHV-associated Kaposi's sarcoma tissue, suggesting that LANA plays an important role in the upregulation of survivin expression in KSHV-infected endothelial cells. Knockdown of survivin expression by lentivirus-delivered small hairpin RNA resulted in loss of cell proliferation in KSHV-infected cells. Therefore, upregulation of survivin expression in KSHV-associated human cells contributes to their proliferation.

scholarly journals Kaposi’s Sarcoma-Associated Herpesvirus Viral Interleukin-6 Signaling Upregulates Integrin β3 Levels and Is Dependent on STAT3

2019 ◽  
Vol 94 (5) ◽  
Author(s):  
Ricardo Rivera-Soto ◽  
Nathan J. Dissinger ◽  
Blossom Damania
Keyword(s):  
Endothelial Cells ◽  
Interleukin 6 ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Αvβ3 Integrin ◽  
Kshv Infection ◽  
Integrin Β3 ◽  
Stat3 Signaling ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi’s sarcoma-associated herpesvirus (KSHV) is the causative agent of two B-cell lymphoproliferative diseases and Kaposi’s sarcoma, an endothelial-cell-driven cancer. KSHV viral interleukin-6 (vIL-6) is a viral homolog of human IL-6 (hIL-6) that is expressed in KSHV-associated malignancies. Previous studies have shown that the expression of the integrin β3 (ITGB3) subunit is induced upon KSHV infection. Here we report that KSHV vIL-6 is able to induce the expression of ITGB3 and increase surface expression of the αVβ3 integrin heterodimer. We demonstrated using small interfering RNA (siRNA) depletion and inhibitor studies that KSHV vIL-6 can increase ITGB3 by inducing STAT3 signaling. Furthermore, we found that secreted vIL-6 is capable of inducing ITGB3 in endothelial cells in a paracrine manner. Importantly, the ability to induce ITGB3 in endothelial cells seems to be specific to vIL-6, as overexpression of hIL-6 alone did not affect levels of this integrin. Our lab and others have previously shown that vIL-6 can induce angiogenesis, and we investigated whether ITGB3 was involved in this process. We found that siRNA depletion of ITGB3 in vIL-6-expressing endothelial cells resulted in a decrease in adhesion to extracellular matrix proteins. Moreover, depletion of ITGB3 hindered the ability of vIL-6 to promote angiogenesis. In conclusion, we found that vIL-6 can singularly induce ITGB3 and that this induction is dependent on vIL-6 activation of the STAT3 signaling pathway. IMPORTANCE Kaposi’s sarcoma-associated herpesvirus (KSHV) is the etiological agent of three human malignancies: multicentric Castleman’s disease, primary effusion lymphoma, and Kaposi’s sarcoma. Kaposi’s sarcoma is a highly angiogenic tumor that arises from endothelial cells. It has been previously reported that KSHV infection of endothelial cells leads to an increase of integrin αVβ3, a molecule observed to be involved in the angiogenic process of several malignancies. Our data demonstrate that the KSHV protein viral interleukin-6 (vIL-6) can induce integrin β3 in an intracellular and paracrine manner. Furthermore, we showed that this induction is necessary for vIL-6-mediated cell adhesion and angiogenesis, suggesting a potential role of integrin β3 in KSHV pathogenesis and development of Kaposi’s sarcoma.

scholarly journals HMGB1 knockout decreases Kaposi's sarcoma-associated herpesvirus virion production in iSLK BAC16 cells by attenuating viral gene expression

2021 ◽  
Author(s):  
Su-Kyung Kang ◽  
Yun Hee Kang ◽  
Seung-Min Yoo ◽  
Changhoon Park ◽  
Hong Seok Kim ◽  
...  
Keyword(s):  
Gene Expression ◽  
Kaposi's Sarcoma ◽  
High Mobility ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Virion Production ◽  
Viral Genes ◽  
Infected Cells ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

Multiple host proteins affect the gene expression of Kaposi's sarcoma-associated herpesvirus (KSHV) during latent and lytic replication. The high mobility group box 1 (HMGB1) serves as a highly conserved chromosomal protein inside the cell and a prototypical damage-associated molecular pattern molecule outside the cell. HMGB1 has been shown to play a pathogenic role in viral infectious diseases and to regulate the lytic replication of KSHV. However, its functional effects on the KSHV life cycle in KSHV-infected cells have not been fully elucidated. Here, we explored the role of the intracellular and extracellular HMGB1 in KSHV virion production by employing CRISPR/Cas9-mediated HMGB1 knockout in the KSHV-producing iSLK BAC16 cell line. Intracellular HMGB1 formed complexes with various proteins, and the abundance of HMGB1-interacting proteins changed during latent and lytic replication. Moreover, extracellular HMGB1 was found to enhance lytic replication by phosphorylating JNK. Of note, the expression of viral genes was attenuated during lytic replication in HMGB1- knockout iSLK BAC16 cells, with significantly decreased production of infectious virions compared to that in wild-type cells. Collectively, our results demonstrate that HMGB1 is an important cellular cofactor that affects the generation of infectious KSHV progeny during lytic replication. Author Summary The high mobility group box 1 protein ( HMGB1 ) has many intra- and extracellular biological functions with an intricate role in various diseases. In certain viral infections, HMGB1 affects the viral life cycle and pathogenesis. In this study, we explored the effects of HMGB1 knockout on the production of Kaposi’s sarcoma-associated herpesvirus (KSHV). HMGB1 knockout decreased virion production in KSHV-producing cells by decreasing the expression of viral genes. The processes by which HMGB1 affects KSHV production may occur inside or outside of infected cells. For instance, several cellular and viral proteins interacted with intracellular HMGB1 in a nucleosomal complex; whereas extracellular HMGB1 induced JNK phosphorylation, thus enhancing lytic replication. Our results suggest that both intracellular and extracellular HMGB1 are necessary for efficient KSHV replication. Thus, HMGB1 may represent an effective therapeutic target for the regulation of KSHV production.

scholarly journals Viral MicroRNAs Repress the Cholesterol Pathway, and 25-Hydroxycholesterol Inhibits Infection

mBio ◽  
2017 ◽  
Vol 8 (4) ◽  
Author(s):  
Anna K. P. Serquiña ◽  
Diane M. Kambach ◽  
Ontara Sarker ◽  
Joseph M. Ziegelbauer
Keyword(s):  
Gene Expression ◽  
Kaposi's Sarcoma ◽  
De Novo ◽  
Natural Infection ◽  
Kaposi’S Sarcoma ◽  
Kshv Infection ◽  
Viral Mirnas ◽  
Cholesterol Levels ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT From various screens, we found that Kaposi’s sarcoma-associated herpesvirus (KSHV) viral microRNAs (miRNAs) target several enzymes in the mevalonate/cholesterol pathway. 3-Hydroxy-3-methylglutaryl-coenzyme A (CoA) synthase 1 (HMGCS1), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR [a rate-limiting step in the mevalonate pathway]), and farnesyl-diphosphate farnesyltransferase 1 (FDFT1 [a committed step in the cholesterol branch]) are repressed by multiple KSHV miRNAs. Transfection of viral miRNA mimics in primary endothelial cells (human umbilical vein endothelial cells [HUVECs]) is sufficient to reduce intracellular cholesterol levels; however, small interfering RNAs (siRNAs) targeting only HMGCS1 did not reduce cholesterol levels. This suggests that multiple targets are needed to perturb this tightly regulated pathway. We also report here that cholesterol levels were decreased in de novo-infected HUVECs after 7 days. This reduction is at least partially due to viral miRNAs, since the mutant form of KSHV lacking 10 of the 12 miRNA genes had increased cholesterol compared to wild-type infections. We hypothesized that KSHV is downregulating cholesterol to suppress the antiviral response by a modified form of cholesterol, 25-hydroxycholesterol (25HC). We found that the cholesterol 25-hydroxylase (CH25H) gene, which is responsible for generating 25HC, had increased expression in de novo-infected HUVECs but was strongly suppressed in long-term latently infected cell lines. We found that 25HC inhibits KSHV infection when added exogenously prior to de novo infection. In conclusion, we found that multiple KSHV viral miRNAs target enzymes in the mevalonate pathway to modulate cholesterol in infected cells during latency. This repression of cholesterol levels could potentially be beneficial to viral infection by decreasing the levels of 25HC. IMPORTANCE A subset of viruses express unique microRNAs (miRNAs), which act like cellular miRNAs to generally repress host gene expression. A cancer virus, Kaposi’s sarcoma-associated herpesvirus (KSHV, or human herpesvirus 8 [HHV-8]), encodes multiple miRNAs that repress gene expression of multiple enzymes that are important for cholesterol synthesis. In cells with these viral miRNAs or with natural infection, cholesterol levels are reduced, indicating these viral miRNAs decrease cholesterol levels. A modified form of cholesterol, 25-hydroxycholesterol, is generated directly from cholesterol. Addition of 25-hydroxycholesterol to primary cells inhibited KSHV infection of cells, suggesting that viral miRNAs may decrease cholesterol levels to decrease the concentration of 25-hydroxycholesterol and to promote infection. These results suggest a new virus-host relationship and indicate a previously unidentified viral strategy to lower cholesterol levels. IMPORTANCE A subset of viruses express unique microRNAs (miRNAs), which act like cellular miRNAs to generally repress host gene expression. A cancer virus, Kaposi’s sarcoma-associated herpesvirus (KSHV, or human herpesvirus 8 [HHV-8]), encodes multiple miRNAs that repress gene expression of multiple enzymes that are important for cholesterol synthesis. In cells with these viral miRNAs or with natural infection, cholesterol levels are reduced, indicating these viral miRNAs decrease cholesterol levels. A modified form of cholesterol, 25-hydroxycholesterol, is generated directly from cholesterol. Addition of 25-hydroxycholesterol to primary cells inhibited KSHV infection of cells, suggesting that viral miRNAs may decrease cholesterol levels to decrease the concentration of 25-hydroxycholesterol and to promote infection. These results suggest a new virus-host relationship and indicate a previously unidentified viral strategy to lower cholesterol levels.

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus Induces Sustained Levels of Vascular Endothelial Growth Factors A and C Early during In Vitro Infection of Human Microvascular Dermal Endothelial Cells: Biological Implications

2007 ◽  
Vol 82 (4) ◽  
pp. 1759-1776 ◽  
Author(s):  
Ramu Sivakumar ◽  
Neelam Sharma-Walia ◽  
Hari Raghu ◽  
Mohanan Valiya Veettil ◽  
Sathish Sadagopan ◽  
...  
Keyword(s):  
Gene Expression ◽  
Endothelial Cells ◽  
Endothelial Cell ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Angiogenic Factors ◽  
Vascular Endothelial ◽  
Kshv Infection ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma (KS), a vascular tumor associated with human immunodeficiency virus type 1 infection, is characterized by spindle-shaped endothelial cells, inflammatory cells, cytokines, growth and angiogenic factors, and angiogenesis. KS spindle cells are believed to be of the lymphatic endothelial cell (LEC) type. Kaposi's sarcoma-associated herpesvirus (KSHV, or human herpesvirus 8) is etiologically linked to KS, and in vitro KSHV infection of primary human dermal microvascular endothelial cells (HMVEC-d) is characterized by the induction of preexisting host signal cascades, sustained expression of latency-associated genes, transient expression of a limited number of lytic genes, sustained induction of NF-κB and several cytokines, and growth and angiogenic factors. KSHV induced robust vascular endothelial growth factor A (VEGF-A) and VEGF-C gene expression as early as 30 min postinfection (p.i.) in serum-starved HMVEC-d, which was sustained throughout the observation period of 72 h p.i. Significant amounts of VEGF-A and -C were also detected in the culture supernatant of infected cells. VEGF-A and -C were also induced by UV-inactivated KSHV and envelope glycoprotein gpK8.1A, thus suggesting a role for virus entry stages in the early induction of VEGF and requirement of KSHV viral gene expression for sustained induction. Exogenous addition of VEGF-A and -C increased KSHV DNA entry into target cells and moderately increased latent ORF73 and lytic ORF50 promoter activation and gene expression. KSHV infection also induced the expression of lymphatic markers Prox-1 and podoplanin as early as 8 h p.i., and a paracrine effect was seen in the neighboring uninfected cells. Similar observations were also made in the pure blood endothelial cell (BEC)-TIME cells, thus suggesting that commitment to the LEC phenotype is induced early during KSHV infection of blood endothelial cells. Treatment with VEGF-C alone also induced Prox-1 expression in the BEC-TIME cells. Collectively, these studies show that the in vitro microenvironments of KSHV-infected endothelial cells are enriched, with VEGF-A and -C molecules playing key roles in KSHV biology, such as increased infection and gene expression, as well as in angiogenesis and lymphangiogenesis, thus recapitulating the microenvironment of early KS lesions.

scholarly journals Latent Kaposi's Sarcoma-Associated Herpesvirus Infection of Endothelial Cells Activates Hypoxia-Induced Factors

2006 ◽  
Vol 80 (21) ◽  
pp. 10802-10812 ◽  
Author(s):  
Patrick A. Carroll ◽  
Heidi L. Kenerson ◽  
Raymond S. Yeung ◽  
Michael Lagunoff
Keyword(s):  
Endothelial Cells ◽  
Kaposi's Sarcoma ◽  
Significant Proportion ◽  
Kaposi’S Sarcoma ◽  
Model Systems ◽  
Luciferase Reporter ◽  
Kshv Infection ◽  
Alpha Subunits ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV or HHV-8) is the etiological agent of Kaposi's sarcoma, a highly vascularized, endothelial-derived tumor. A direct role for KSHV-mediated induction of angiogenesis has been proposed based upon the nature of the neoplasia and various KSHV gene overexpression and infection model systems. We have found that KSHV infection of endothelial cells induces mRNA of hypoxia-induced factor 1α (HIF1α) and HIF2α, two homologous alpha subunits of the heterodimeric transcription factor HIF. HIF is a master regulator of both developmental and pathological angiogenesis, composed of an oxygen-sensitive alpha subunit and a constitutively expressed beta subunit. HIF is classically activated posttranscriptionally with hypoxia, leading to increased protein stability of HIF1α and/or HIF2α. However, we demonstrate that both alpha subunits are up-regulated at the transcript level by KSHV infection. The transcriptional activation of HIF leads to a functional increase in HIF activity under normoxic conditions, as demonstrated by both luciferase reporter assay and the increased expression of vascular endothelial growth factor receptor 1 (VEGFR1), an HIF-responsive gene. KSHV infection synergizes with hypoxia mimics and induces higher expression levels of HIF1α and HIF2α protein, and HIF1α is increased in a significant proportion of the latently infected endothelial cells. Src family kinases are required for the activation of HIF and the downstream gene VEGFR1 by KSHV. We also show that KS lesions, in vivo, express elevated levels of HIF1α and HIF2α proteins. Thus, KSHV stimulates the HIF pathway via transcriptional up-regulation of both HIF alphas, and this activation may play a role in KS formation, localization, and progression.

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus Hijacks RNA Polymerase II To Create a Viral Transcriptional Factory

2017 ◽  
Vol 91 (11) ◽  
Author(s):  
Christopher Phillip Chen ◽  
Yuanzhi Lyu ◽  
Frank Chuang ◽  
Kazushi Nakano ◽  
Chie Izumiya ◽  
...  
Keyword(s):  
Gene Expression ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Cellular Gene ◽  
Viral Genomes ◽  
Infected Cells ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Locally concentrated nuclear factors ensure efficient binding to DNA templates, facilitating RNA polymerase II recruitment and frequent reutilization of stable preinitiation complexes. We have uncovered a mechanism for effective viral transcription by focal assembly of RNA polymerase II around Kaposi's sarcoma-associated herpesvirus (KSHV) genomes in the host cell nucleus. Using immunofluorescence labeling of latent nuclear antigen (LANA) protein, together with fluorescence in situ RNA hybridization (RNA-FISH) of the intron region of immediate early transcripts, we visualized active transcription of viral genomes in naturally infected cells. At the single-cell level, we found that not all episomes were uniformly transcribed following reactivation stimuli. However, those episomes that were being transcribed would spontaneously aggregate to form transcriptional “factories,” which recruited a significant fraction of cellular RNA polymerase II. Focal assembly of “viral transcriptional factories” decreased the pool of cellular RNA polymerase II available for cellular gene transcription, which consequently impaired cellular gene expression globally, with the exception of selected ones. The viral transcriptional factories localized with replicating viral genomic DNAs. The observed colocalization of viral transcriptional factories with replicating viral genomic DNA suggests that KSHV assembles an “all-in-one” factory for both gene transcription and DNA replication. We propose that the assembly of RNA polymerase II around viral episomes in the nucleus may be a previously unexplored aspect of KSHV gene regulation by confiscation of a limited supply of RNA polymerase II in infected cells. IMPORTANCE B cells infected with Kaposi's sarcoma-associated herpesvirus (KSHV) harbor multiple copies of the KSHV genome in the form of episomes. Three-dimensional imaging of viral gene expression in the nucleus allows us to study interactions and changes in the physical distribution of these episomes following stimulation. The results showed heterogeneity in the responses of individual KSHV episomes to stimuli within a single reactivating cell; those episomes that did respond to stimulation, aggregated within large domains that appear to function as viral transcription factories. A significant portion of cellular RNA polymerase II was trapped in these factories and served to transcribe viral genomes, which coincided with an overall decrease in cellular gene expression. Our findings uncover a strategy of KSHV gene regulation through focal assembly of KSHV episomes and a molecular mechanism of late gene expression.

scholarly journals Persistent Activation of STAT3 by Latent Kaposi's Sarcoma-Associated Herpesvirus Infection of Endothelial Cells

2006 ◽  
Vol 81 (5) ◽  
pp. 2449-2458 ◽  
Author(s):  
Almira S. Punjabi ◽  
Patrick A. Carroll ◽  
Lei Chen ◽  
Michael Lagunoff
Keyword(s):  
Endothelial Cells ◽  
Tumor Cell ◽  
Kaposi's Sarcoma ◽  
Primary Effusion Lymphoma ◽  
Kaposi’S Sarcoma ◽  
Receptor Expression ◽  
Kshv Infection ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) is the infectious cause of Kaposi's sarcoma, primary effusion lymphoma, and plasmablastic multicentric Castleman's disease. STAT3 has been shown to be important for the maintenance of primary effusion lymphoma cells in culture and is chronically activated in many tumor cell lines. However, little is known about the role of KSHV in the activation of STAT3 or the role of STAT3 in KS tumors. We demonstrate that STAT3 is activated by KSHV infection of endothelial cells, the KS tumor cell type, in a biphasic fashion. Viral binding and entry activate STAT3 in the first 2 h after infection, but this activation dissipates by 4 h postinfection. By 12 h after KSHV infection, concomitant with the expression of latent genes, STAT3 is once again activated, and this activation persists for as long as latent infection is maintained. Activated STAT3 translocates to the nucleus, where it can bind to STAT3-specific DNA elements and can activate STAT3-dependent promoter activity. Conditioned medium from KSHV-infected endothelial cells is able to transiently activate STAT3, indicating the involvement of a secreted factor and that a latency-associated factor in KSHV-infected cells is necessary for sustained activation. KSHV upregulates gp130 receptor expression, and both gp130 and JAK2 are required for the activation of STAT3. However, neither human nor viral interleukin-6 is required for STAT3 activation. Persistent activation of the oncogenic signal transducer, STAT3, by KSHV may play a critical role in the viral pathogenesis of Kaposi's sarcoma, as well as in primary effusion lymphomas.

scholarly journals Screening of the Human Kinome Identifies MSK1/2-CREB1 as an Essential Pathway Mediating Kaposi's Sarcoma-Associated Herpesvirus Lytic Replication during Primary Infection

2015 ◽  
Vol 89 (18) ◽  
pp. 9262-9280 ◽  
Author(s):  
Fan Cheng ◽  
Tanvee Vinod Sawant ◽  
Ke Lan ◽  
Chun Lu ◽  
Jae U. Jung ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Protein Kinase ◽  
Primary Infection ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Kshv Infection ◽  
Cellular Pathways ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACTViruses often hijack cellular pathways to facilitate infection and replication. Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic gammaherpesvirus etiologically associated with Kaposi's sarcoma, a vascular tumor of endothelial cells. Despite intensive studies, cellular pathways mediating KSHV infection and replication are still not well defined. Using an antibody array approach, we examined cellular proteins phosphorylated during primary KSHV infection of primary human umbilical vein endothelial cells. Enrichment analysis identified integrin/mitogen-activated protein kinase (integrin/MAPK), insulin/epidermal growth factor receptor (insulin/EGFR), and JAK/STAT as the activated networks during primary KSHV infection. The transcriptional factor CREB1 (cyclic AMP [cAMP]-responsive element-binding protein 1) had the strongest increase in phosphorylation. While knockdown of CREB1 had no effect on KSHV entry and trafficking, it drastically reduced the expression of lytic transcripts and proteins and the production of infectious virions. Chemical activation of CREB1 significantly enhanced viral lytic replication. In contrast, CREB1 neither influenced the expression of the latent gene LANA nor affected KSHV infectivity. Mechanistically, CREB1 was not activated through the classic cAMP/protein kinase A (cAMP/PKA) pathway or via the AKT, MK2, and RSK pathways. Rather, CREB1 was activated by the mitogen- and stress-activated protein kinases 1 and 2 (MSK1/2). Consequently, chemical inhibition or knockdown of MSKs significantly inhibited the KSHV lytic replication program; however, it had a minimal effect on LANA expression and KSHV infectivity. Together, these results identify the MSK1/2-CREB1 proteins as novel essential effectors of KSHV lytic replication during primary infection. The differential effect of the MSK1/2-CREB1 pathway on the expression of viral latent and lytic genes might control the robustness of viral lytic replication, and therefore the KSHV replication program, during primary infection.IMPORTANCEKaposi's sarcoma-associated herpesvirus (KSHV) is a human tumor virus associated with several cancers. Through genome-wide kinase screening, we found that KSHV activates the MSK1/2-CREB1 pathway during primary infection and that it depends on this pathway for viral lytic replication. Inhibition of this pathway blocks KSHV lytic replication. These results illustrate a mechanism by which KSHV hijacks a cellular pathway for its replication, and they identify a potential therapeutic target.

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