GRWD1-WDR5-MLL2 Epigenetic Complex Mediates H3K4me3 Mark and Is Essential for Kaposi’s Sarcoma-Associated Herpesvirus-Induced Cellular Transformation

By performing a genome-wide CRISPR-Cas9 screening, we have identified cellular epigenetic regulators that are essential for KSHV-induced cellular transformation. Among them, GRWD1 regulates epigenetic active mark H3K4me3 by interacting with WDR5 and MLL2 and recruiting them to chromatin loci of specific genes in KSHV-transformed cells.

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Myc Is Required for the Maintenance of Kaposi's Sarcoma-Associated Herpesvirus Latency

Journal of Virology ◽

10.1128/jvi.00244-10 ◽

2010 ◽

Vol 84 (17) ◽

pp. 8945-8948 ◽

Cited By ~ 27

Author(s):

Xudong Li ◽

Shijia Chen ◽

Jun Feng ◽

Hongyu Deng ◽

Ren Sun

Keyword(s):

Cell Cycle ◽

Kaposi's Sarcoma ◽

Promoter Activity ◽

Primary Effusion Lymphoma ◽

Kaposi’S Sarcoma ◽

Cellular Transformation ◽

Mrna Levels ◽

Cycle Arrest ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Myc is deregulated by Kaposi's sarcoma-associated herpesvirus (KSHV) latent proteins, but its role in KSHV latency is not clear. We found that Myc knockdown with RNA interference (RNAi) induced KSHV reactivation and increased the protein and mRNA levels of RTA, a key viral regulator of KSHV reactivation. Myc knockdown increased, whereas Myc overexpression inhibited, RTA promoter activity. KSHV reactivation and the activation of the RTA promoter induced by Myc depletion were inhibited by c-Jun N-terminal kinase (JNK) and p38 inhibitors but not by a MEK1 inhibitor. Myc knockdown inhibited primary effusion lymphoma (PEL) cell proliferation through inducing apoptosis and G1 cell cycle arrest. Thus, Myc may be a key cellular node coupling cellular transformation and KSHV latency.

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Oncogenic Kaposi’s Sarcoma-Associated Herpesvirus Upregulates Argininosuccinate Synthase 1, a Rate-Limiting Enzyme of the Citrulline-Nitric Oxide Cycle, To Activate the STAT3 Pathway and Promote Growth Transformation

Journal of Virology ◽

10.1128/jvi.01599-18 ◽

2018 ◽

Vol 93 (4) ◽

Cited By ~ 2

Author(s):

Tingting Li ◽

Ying Zhu ◽

Fan Cheng ◽

Chun Lu ◽

Jae U. Jung ◽

...

Keyword(s):

Nitric Oxide ◽

Kaposi's Sarcoma ◽

Kaposi’S Sarcoma ◽

Soft Agar ◽

Transformed Cells ◽

Stat3 Pathway ◽

Growth Transformation ◽

Argininosuccinate Synthase ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Cancer cells are required to rewire existing metabolic pathways to support their abnormal proliferation. We have previously shown that, unlike glucose-addicted cancers, Kaposi’s sarcoma-associated herpesvirus (KSHV)-transformed cells depend on glutamine rather than glucose for energy production and amino acid and nucleotide syntheses. High-level consumption of glutamine is tightly regulated and often coupled with the citrulline-nitric oxide (NO) cycle. We have found that KSHV infection accelerates nitrogen efflux by upregulating the expression of argininosuccinate synthase 1 (ASS1), a key enzyme in the citrulline-NO cycle. KSHV utilizes multiple microRNAs to upregulate ASS1 expression. Depletion of either ASS1 or inducible nitric oxide synthase (iNOS) in KSHV-transformed cells suppresses growth proliferation, abolishes colony formation in soft agar, and decreases NO generation. Furthermore, by maintaining intracellular NO levels, ASS1 expression facilitates KSHV-mediated activation of the STAT3 pathway, which is critical for virus-induced transformation. These results illustrate a novel mechanism by which an oncogenic virus hijacks a key metabolic pathway to promote growth transformation and reveal a potential novel therapeutic target for KSHV-induced malignancies. IMPORTANCE We have previously shown that Kaposi’s sarcoma-associated herpesvirus (KSHV)-transformed cells depend on glutamine rather than glucose for energy production and amino acid and nucleotide syntheses. In this study, we have further examined how the KSHV-reprogramed metabolic pathways are regulated and discovered that KSHV hijacks the citrulline-nitric oxide (NO) cycle to promote growth proliferation and transformation. Multiple KSHV-encoded microRNAs upregulate argininosuccinate synthase 1 (ASS1), a key enzyme in the citrulline-NO cycle. ASS1 is required for KSHV-induced proliferation, colony formation in soft agar, and NO generation of KSHV-transformed cells, which also depends on inducible nitric oxide synthase. By maintaining intracellular NO levels, ASS1 mediates KSHV activation of the STAT3 pathway, which is essential for KSHV-induced abnormal cell proliferation and transformation. These results illustrate a novel mechanism by which an oncogenic virus hijacks a key metabolic pathway to promote growth transformation and reveal a potential novel therapeutic target for KSHV-induced malignancies.

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The K1 Protein of Kaposi's Sarcoma-Associated Herpesvirus Activates the Akt Signaling Pathway

Journal of Virology ◽

10.1128/jvi.78.4.1918-1927.2004 ◽

2004 ◽

Vol 78 (4) ◽

pp. 1918-1927 ◽

Cited By ~ 113

Author(s):

Christine C. Tomlinson ◽

Blossom Damania

Keyword(s):

Kaposi's Sarcoma ◽

Cell Cycle Progression ◽

B Lymphocyte ◽

Primary Effusion Lymphoma ◽

Kaposi’S Sarcoma ◽

Cellular Transformation ◽

Cell Receptor ◽

Focus Formation ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) has been implicated in Kaposi's sarcoma, as well as in primary effusion lymphoma and multicentric Castleman's disease. The K1 protein of KSHV has been shown to induce cellular transformation and focus formation and to deregulate B-lymphocyte signaling pathways by functionally mimicking the activated B-cell receptor complex. Here we show that expression of K1 in B lymphocytes targets the phosphatidylinositol-3 kinase pathway, leading to the activation of the Akt kinase and the inhibition of the phosphatase PTEN. We also demonstrate that activation of Akt by the K1 protein leads to the phosphorylation and inhibition of members of the forkhead (FKHR) transcription factor family, which are key regulators of cell cycle progression and apoptosis. We demonstrate that K1 can inhibit apoptosis induced by the FKHR proteins and by stimulation of the Fas receptor. Our observations suggest that the K1 viral protein promotes cell survival pathways and may contribute to KSHV pathogenesis by preventing virally infected cells from undergoing apoptosis prematurely.

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MicroRNA-Mediated Transformation by the Kaposi's Sarcoma-Associated Herpesvirus Kaposin Locus

Journal of Virology ◽

10.1128/jvi.03317-14 ◽

2014 ◽

Vol 89 (4) ◽

pp. 2333-2341 ◽

Cited By ~ 17

Author(s):

Eleonora Forte ◽

Archana N. Raja ◽

Priscilla Shamulailatpam ◽

Mark Manzano ◽

Matthew J. Schipma ◽

...

Keyword(s):

Kaposi's Sarcoma ◽

Ectopic Expression ◽

Human Tumor ◽

Kaposi’S Sarcoma ◽

Cellular Transformation ◽

Coding Region ◽

Stem Loop ◽

Tumor Virus ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACTThe human oncogenic Kaposi's sarcoma-associated herpesvirus (KSHV) expresses a set of ∼20 viral microRNAs (miRNAs). miR-K10a stands out among these miRNAs because its entire stem-loop precursor overlaps the coding sequence for the Kaposin (Kap) A/C proteins. The ectopic expression of KapA has been reported to lead to transformation of rodent fibroblasts. However, these experiments inadvertently also introduced miR-K10a, which raises the question whether the transforming activity of the locus could in fact be due to miR-K10a expression. To answer this question, we have uncoupled miR-K10a and KapA expression. Our experiments revealed that miR-K10a alone transformed cells with an efficiency similar to that when it was coexpressed with KapA. Maintenance of the transformed phenotype was conditional upon continued miR-K10a but not KapA protein expression, consistent with its dependence on miRNA-mediated changes in gene expression. Importantly, miR-K10a taps into an evolutionarily conserved network of miR-142-3p targets, several of which are expressed in 3T3 cells and are also known inhibitors of cellular transformation. In summary, our studies of miR-K10a serve as an example of an unsuspected function of an mRNA whose precursor is embedded within a coding transcript. In addition, our identification of conserved miR-K10a targets that limit transformation will point the way to a better understanding of the role of this miRNA in KSHV-associated tumors.IMPORTANCEKaposi's sarcoma-associated herpesvirus (KSHV) is a human tumor virus. The viral Kaposin locus has known oncogenic potential, which has previously been attributed to the encoded KapA protein. Here we show that the virally encoded miR-K10a miRNA, whose precursor overlaps the KapA-coding region, may account for the oncogenic properties of this locus. Our data suggest that miR-K10a mimics the cellular miRNA miR-142-3p and thereby represses several known inhibitors of oncogenic transformation. Our work demonstrates that functional properties attributed to a coding region may in fact be carried out by an embedded noncoding element and sheds light on the functions of viral miR-K10a.

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Transcriptional Analysis of Latent and Inducible Kaposi's Sarcoma-Associated Herpesvirus Transcripts in the K4 to K7 Region

Journal of Virology ◽

10.1128/jvi.79.24.15099-15106.2005 ◽

2005 ◽

Vol 79 (24) ◽

pp. 15099-15106 ◽

Cited By ~ 28

Author(s):

Jennifer L. Taylor ◽

Heather N. Bennett ◽

Beth A. Snyder ◽

Patrick S. Moore ◽

Yuan Chang

Keyword(s):

Kaposi's Sarcoma ◽

De Novo ◽

Primary Effusion Lymphoma ◽

Kaposi’S Sarcoma ◽

Transcriptional Analysis ◽

Phage Library ◽

Coding Region ◽

A Genome ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) is a gamma-2 herpesvirus with a genome containing a long unique coding region (LUR) flanked by GC-rich terminal repeat sequences. The LUR encodes approximately 90 annotated open reading frames (ORFs) with complex patterns of gene expression during viral latency, reactivation, and de novo infection. To identify unannotated KSHV genes, we examined the region between 21,500 and 30,000 bp of the KSHV LUR, representing approximately 8.5 kb of sequence. This region encodes seven known single-exon ORFs (K4, K4.1, K4.2, K5, K6, K7, and PAN), but previous computer analyses have failed to identify additional likely genes in the remaining 5.2 kb. We identified four novel transcripts using Northern blotting, phage library screening, and 5′ rapid amplification of cDNA ends analysis in the region between ORFs K4.2 and K7. In vitro analysis of KSHV-infected primary effusion lymphoma cell lines in the presence of 12-O-tetradecanoylphorbol-13-acetate and phosphonoformic acid suggests that one latent transcript is coterminal with the previously annotated K3 gene encoding an ubiquitin-ligase known to downregulate major histocompatibility complex class I expression. This alternatively spliced transcript may contribute to KSHV adaptive immune evasion during latent infection. Other transcripts are inducible, including a 6.1-kb transcript that is the largest transcript found in the KSHV genome to date.

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Viral Interferon Regulatory Factor 1 of Kaposi's Sarcoma-Associated Herpesvirus Binds to p53 and Represses p53-Dependent Transcription and Apoptosis

Journal of Virology ◽

10.1128/jvi.75.13.6193-6198.2001 ◽

2001 ◽

Vol 75 (13) ◽

pp. 6193-6198 ◽

Cited By ~ 79

Author(s):

Taegun Seo ◽

Junsoo Park ◽

Daeyoup Lee ◽

Sun Gwan Hwang ◽

Joonho Choe

Keyword(s):

Kaposi's Sarcoma ◽

Kaposi’S Sarcoma ◽

Cellular Transformation ◽

Interferon Regulatory Factor ◽

Regulatory Factor ◽

Reading Frame ◽

Interferon Regulatory Factor 1 ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Apoptotic Activity ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) is related to the development of Kaposi's sarcoma. Open reading frame K9 of KSHV encodes viral interferon regulatory factor 1 (vIRF1), which functions as a repressor of interferon- and IRF1-mediated signal transduction. In addition, vIRF1 acts as an oncogene to induce cellular transformation. Here we show that vIRF1 directly associates with the tumor suppressor p53 and represses its functions. The vIRF1 interaction domains of p53 are the DNA binding domain (amino acids [aa] 100 to 300) and the tetramerization domain (aa 300 to 393). p53 interacts with the central region (aa 152 to 360) of vIRF1. vIRF1 suppresses p53-dependent transcription and deregulates its apoptotic activity. These results suggest that vIRF1 may regulate cellular function by inhibiting p53.

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IKKγ-Mimetic Peptides Block the Resistance to Apoptosis Associated with Kaposi's Sarcoma-Associated Herpesvirus Infection

Journal of Virology ◽

10.1128/jvi.01170-17 ◽

2017 ◽

Vol 91 (23) ◽

Cited By ~ 5

Author(s):

Louise C. Briggs ◽

A. W. Edith Chan ◽

Christopher A. Davis ◽

Nicholas Whitelock ◽

Hajira A. Hotiana ◽

...

Keyword(s):

Cell Death ◽

Kaposi's Sarcoma ◽

Primary Effusion Lymphoma ◽

Kaposi’S Sarcoma ◽

Cellular Transformation ◽

Physical Interaction ◽

Viral Oncoprotein ◽

Mimetic Peptides ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Primary effusion lymphoma (PEL) is a lymphogenic disorder associated with Kaposi's sarcoma-associated herpesvirus (KSHV) infection. Key to the survival and proliferation of PEL is the canonical NF-κB pathway, which becomes constitutively activated following overexpression of the viral oncoprotein KSHV vFLIP (ks-vFLIP). This arises from its capacity to form a complex with the modulatory subunit of the IκB kinase (IKK) kinase, IKKγ (or NEMO), resulting in the overproduction of proteins that promote cellular survival and prevent apoptosis, both of which are important drivers of tumorigenesis. Using a combination of cell-based and biophysical assays together with structural techniques, we showed that the observed resistance to cell death is largely independent of autophagy or major death receptor signaling pathways and demonstrated that direct targeting of the ks-vFLIP–IKKγ interaction both in cells and in vitro can be achieved using IKKγ-mimetic peptides. Our results further reveal that these peptides not only induce cell killing but also potently sensitize PEL to the proapoptotic agents tumor necrosis factor alpha and etoposide and are the first to confirm ks-vFLIP as a tractable target for the treatment of PEL and related disorders. IMPORTANCE KSHV vFLIP (ks-vFLIP) has been shown to have a crucial role in cellular transformation, in which it is vital for the survival and proliferation of primary effusion lymphoma (PEL), an aggressive malignancy associated with infection that is resistant to the majority of chemotherapeutic drugs. It operates via subversion of the canonical NF-κB pathway, which requires a physical interaction between ks-vFLIP and the IKK kinase modulatory subunit IKKγ. While this interaction has been directly linked to protection against apoptosis, it is unclear whether the suppression of other cell death pathways implicated in ks-vFLIP pathogenesis is an additional contributor. We demonstrate that the interaction between ks-vFLIP and IKKγ is pivotal in conferring resistance to apoptosis. Additionally, we show that the ks-vFLIP–IKKγ complex can be disrupted using peptides leading to direct killing and the sensitization of PEL cells to proapoptotic agents. Our studies thus provide a framework for future therapeutic interventions.

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