scholarly journals Kaposi's Sarcoma-Associated Herpesvirus Viral Interferon Regulatory Factor 4 Targets MDM2 To Deregulate the p53 Tumor Suppressor Pathway

2009 ◽  
Vol 83 (13) ◽  
pp. 6739-6747 ◽  
Author(s):  
Hye-Ra Lee ◽  
Zsolt Toth ◽  
Young C. Shin ◽  
Jong-Soo Lee ◽  
Heesoon Chang ◽  
...  
Keyword(s):  
Cell Growth ◽  
Tumor Suppressor ◽  
Viral Replication ◽  
Ubiquitin Ligase ◽  
Kaposi's Sarcoma ◽  
E3 Ubiquitin Ligase ◽  
Growth Control ◽  
Kaposi’S Sarcoma ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Cell Growth Control

ABSTRACT Cells infected by viruses utilize interferon (IFN)-mediated and p53-mediated irreversible cell cycle arrest and apoptosis as part of the overall host surveillance mechanism to ultimately block viral replication and dissemination. Viruses, in turn, have evolved elaborate mechanisms to subvert IFN- and p53-mediated host innate immune responses. Kaposi's sarcoma-associated herpesvirus (KSHV) encodes several viral IFN regulatory factors (vIRF1 to vIRF4) within a cluster of loci, their functions being primarily to inhibit host IFN-mediated innate immunity and deregulate p53-mediated cell growth control. Despite its significant homology and similar genomic location to other vIRFs, vIRF4 is distinctive, as it does not target and antagonize host IFN-mediated signal transduction. Here, we show that KSHV vIRF4 interacts with the murine double minute 2 (MDM2) E3 ubiquitin ligase, leading to the reduction of p53, a tumor suppressor, via proteasome-mediated degradation. The central region of vIRF4 is required for its interaction with MDM2, which led to the suppression of MDM2 autoubiquitination and, thereby, a dramatic increase in MDM2 stability. Consequently, vIRF4 expression markedly enhanced p53 ubiquitination and degradation, effectively suppressing p53-mediated apoptosis. These results indicate that KSHV vIRF4 targets and stabilizes the MDM2 E3 ubiquitin ligase to facilitate the proteasome-mediated degradation of p53, perhaps to circumvent host growth surveillance and facilitate viral replication in infected cells. Taken together, the indications are that the downregulation of p53-mediated cell growth control is a common characteristic of the four KSHV vIRFs and that p53 is indeed a key factor in the host's immune surveillance program against viral infections.

scholarly journals The Kaposi's Sarcoma-Associated Herpesvirus K5 E3 Ubiquitin Ligase Modulates Targets by Multiple Molecular Mechanisms

2007 ◽  
Vol 81 (12) ◽  
pp. 6573-6583 ◽  
Author(s):  
Robert E. Means ◽  
Sabine M. Lang ◽  
Jae U. Jung
Keyword(s):  
Cell Surface ◽  
Ubiquitin Ligase ◽  
Kaposi's Sarcoma ◽  
E3 Ubiquitin Ligase ◽  
Kaposi’S Sarcoma ◽  
Down Regulation ◽  
Class I Mhc ◽  
Mhc I ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus encodes two highly related membrane-associated, RING-CH-containing (MARCH) family E3 ubiquitin ligases, K3 and K5, that can down regulate a variety of cell surface proteins through enhancement of their endocytosis and degradation. In this report we present data that while K5 modulation of major histocompatibility complex class I (MHC-I) closely mirrors the mechanisms used by K3, alternative molecular pathways are utilized by this E3 ligase in the down regulation of intercellular adhesion molecule 1 (ICAM-1) and B7.2. Internalization assays demonstrate that down regulation of each target can occur through increased endocytosis from the cell surface. However, mutation of a conserved tyrosine-based endocytosis motif in K5 resulted in a protein lacking the ability to direct an increased rate of MHC-I or ICAM-1 internalization but still able to down regulate B7.2 in a ubiquitin-dependent but endocytosis-independent manner. Further, mutation of two acidic clusters abolished K5-mediated MHC-I degradation while only slightly decreasing ICAM-1 or B7.2 protein destruction. This same mutant abolished detectable ubiquitylation of all targets. These data indicate that while K5 can act as an E3 ubiquitin ligase to directly mediate cell surface molecule destruction, regulation of its targets occurs through multiple pathways, including ubiquitin-independent mechanisms.

scholarly journals An Insight Into The Role of E3 ubiquitin Ligase c-Cbl, ESCRT Machinery and Host Cell Signaling in Kaposi's Sarcoma-Associated Herpesvirus (KSHV) Entry and Trafficking

2017 ◽  
pp. JVI.01376-17 ◽  
Author(s):  
Binod Kumar ◽  
Arunava Roy ◽  
Mohanan Valiya Veettil ◽  
Bala Chandran
Keyword(s):  
Host Cell ◽  
Ubiquitin Ligase ◽  
Kaposi's Sarcoma ◽  
E3 Ubiquitin Ligase ◽  
Kaposi’S Sarcoma ◽  
Host Protein ◽  
Cell Surface Receptor ◽  
Signal Molecules ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV)in vitroinfection of dermal endothelial cell begins with its binding to host cell surface receptor molecules such as heparan sulfate (HS), integrins (α3β1, αVβ3 and αVβ5), xCT and EphA2 receptor tyrosine kinase (EphA2R). These initial events initiate dynamic host protein-protein interactions involving a multi-molecular complex of receptors, signal molecules (FAK, Src, PI3-K, RhoA-GTPase), adaptors (c-Cbl, CIB1, Crk, p130Cas and GEF-C3G), and actin/myosin II light chain that leads to virus entry via macropinocytosis. Here we discuss how KSHV hijacks c-Cbl, an E3 ubiquitin ligase, to monoubiquitinate the receptors/actin which acts like markers for trafficking (similar to zip codes), resulting in the recruitment of the members of the host endosomal sorting complexes required for transport (ESCRT) Hrs, Tsg101, EAP45, CHMP 5 and 6 proteins (zip code readers) recognizing the ubiquitinated proteins and adaptors machinery to traffic through the different endosomal compartments in the cytoplasm to initiate the macropinocytic process and infection.

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus LANA Modulates the Stability of the E3 Ubiquitin Ligase RLIM

2019 ◽  
Vol 94 (5) ◽  
Author(s):  
Hagar Tadmor ◽  
Melanie Greenway ◽  
Anuj Ahuja ◽  
Ola Orgil ◽  
Gangling Liao ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Kaposi's Sarcoma ◽  
E3 Ubiquitin Ligase ◽  
Ring Finger ◽  
Kaposi’S Sarcoma ◽  
Interacting Protein ◽  
Transcription Regulators ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
The Stability ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT The Kaposi’s sarcoma-associated herpesvirus (KSHV)-encoded latency-associated nuclear antigen (LANA) protein functions in latently infected cells as an essential participant in KSHV genome replication and as a driver of dysregulated cell growth. In a previous study, we have identified LANA-interacting proteins using a protein array screen. Here, we explore the effect of LANA on the stability and activity of RLIM (RING finger LIM-domain-interacting protein, encoded by the RNF12 gene), a novel LANA-interacting protein identified in that protein screen. RLIM is an E3 ubiquitin ligase that leads to the ubiquitination and degradation of several transcription regulators, such as LMO2, LMO4, LHX2, LHX3, LDB1, and the telomeric protein TRF1. Expression of LANA leads to downregulation of RLIM protein levels. This LANA-mediated RLIM degradation is blocked in the presence of the proteasome inhibitor, MG132. Therefore, the interaction between LANA and RLIM could be detected in coimmunoprecipitation assay only in the presence of MG132 to prevent RLIM degradation. A RING finger mutant RLIM is resistant to LANA-mediated degradation, suggesting that LANA promotes RLIM autoubiquitination. Interestingly, we found that LANA enhanced the degradation of some RLIM substrates, such as LDB1 and LMO2, and prevented RLIM-mediated degradation of others, such as LHX3 and TRF1. We also show that transcription regulation by RLIM substrates is modulated by LANA. RLIM substrates are assembled into multiprotein transcription regulator complexes that regulate the expression of many cellular genes. Therefore, our study identified another way KSHV can modulate cellular gene expression. IMPORTANCE E3 ubiquitin ligases mark their substrates for degradation and therefore control the cellular abundance of their substrates. RLIM is an E3 ubiquitin ligase that leads to the ubiquitination and degradation of several transcription regulators, such as LMO2, LMO4, LHX2, LHX3, LDB1, and the telomeric protein TRF1. Here, we show that the Kaposi’s sarcoma-associated herpesvirus (KSHV)-encoded LANA protein enhances the ubiquitin ligase activity of RLIM, leading to enhanced RLIM autoubiquitination and degradation. Interestingly, LANA enhanced the degradation of some RLIM substrates, such as LDB1 and LMO2, and prevented RLIM-mediated degradation of others, such as LHX3 and TRF1. In agreement with protein stability of RLIM substrates, we found that LANA modulates transcription by LHX3-LDB1 complex and suggest additional ways LANA can modulate cellular gene expression. Our study adds another way a viral protein can regulate cellular protein stability, by enhancing the autoubiquitination and degradation of an E3 ubiquitin ligase.

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus ori-Lyt-Dependent DNA Replication: Involvement of Host Cellular Factors

2008 ◽  
Vol 82 (6) ◽  
pp. 2867-2882 ◽  
Author(s):  
Yan Wang ◽  
Hong Li ◽  
Qiyi Tang ◽  
Gerd G. Maul ◽  
Yan Yuan
Keyword(s):  
Dna Replication ◽  
Viral Replication ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Cellular Proteins ◽  
Cellular Factors ◽  
Virally Encoded ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Lytic Dna Replication ◽  
Parp 1

ABSTRACT Herpesvirus lytic DNA replication requires both the cis-acting element, the origin, and trans-acting factors, including virally encoded origin-binding protein, DNA replication enzymes, and auxiliary factors. Two lytic DNA replication origins (ori-Lyt) of Kaposi's sarcoma-associated herpesvirus (KSHV) have been identified, and two virally encoded proteins, namely, RTA and K8, have been shown to bind to the origins. In this study, we sought to identify cellular factors that associate with ori-Lyt by using DNA affinity purification and mass spectrometry. This approach led to identification of several cellular proteins that bind to KSHV ori-Lyt. They include topoisomerases (Topo) I and II, MSH2/6, RecQL, poly(ADP-ribose) polymerase I (PARP-1), DNA-PK, Ku86/70 autoantigens, and scaffold attachment factor A (SAF-A). RecQL appears to associate with prereplication complexes and be recruited to ori-Lyt through RTA and K8. Topoisomerases, MSH2, PARP-1, DNA-PK, and Ku86 were not detected in prereplication complexes but were present in replication initiation complexes on ori-Lyt. All these cellular proteins accumulate in viral replication compartments in the nucleus, indicating that these proteins may have a role in viral replication. Topo I and II appear to be essential for viral DNA replication as inhibition of their activities with specific inhibitors (camptothecin and ellipticine) blocked ori-Lyt-dependent DNA replication. Furthermore, inhibition of PARP-1 with chemical inhibitors (3-aminobenzamide and niacinamide) resulted in decreased ori-Lyt-dependent DNA replication, whereas hydroxyurea, which raises PARP-1 activity, caused an increase in the DNA replication, suggesting a positive role for PARP-1 in KSHV lytic DNA replication.

scholarly journals K-bZIP of Kaposi's Sarcoma-Associated Herpesvirus/Human Herpesvirus 8 (KSHV/HHV-8) Binds KSHV/HHV-8 Rta and Represses Rta-Mediated Transactivation

2003 ◽  
Vol 77 (6) ◽  
pp. 3809-3815 ◽  
Author(s):  
Wei Liao ◽  
Yong Tang ◽  
Su-Fan Lin ◽  
Hsing-Jien Kung ◽  
Chou-Zen Giam
Keyword(s):  
Viral Replication ◽  
Kaposi's Sarcoma ◽  
Leucine Zipper ◽  
Human Herpesvirus ◽  
Kaposi’S Sarcoma ◽  
Early Gene ◽  
Human Herpesvirus 8 ◽  
Herpesvirus 8 ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT The regulatory circuit for Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 (KSHV/HHV-8) gene expression bears resemblance to that of Epstein-Barr virus (EBV), but with interesting differences. Based on protein sequence similarities and synteny to their EBV counterparts, two KSHV/HHV-8 viral regulatory factors, HHV-8 Rta and K-bZIP, encoded by open reading frame (ORF) 50 and ORF K8, respectively, have been identified. Rta is an immediate early transcriptional activator that activates lytic viral replication and mediates viral reactivation from latency, while ORF K8 is an early gene activated by Rta. Extensive splicing of ORF K8 mRNA leads to the production of K-bZIP, a protein of the basic domain-leucine zipper (bZIP) family. The role of K-bZIP in viral replication, however, remains unresolved. Here, we report that K-bZIP is a nuclear protein that binds Rta directly both in vivo and in vitro and represses Rta-mediated transactivation of the K-bZIP promoter. We further demonstrate that the leucine zipper domain of K-bZIP is required for Rta binding and a K-bZIP mutant lacking the leucine zipper does not repress Rta activity. Finally, the K-bZIP-mediated repression of Rta transactivation cannot be restored by overexpression of the transcriptional coactivator p300 or the p300-CBP-associated factor, P/CAF. Our results suggest that K-bZIP is involved in a feedback circuit to turn off its own expression and possibly the expression of other early genes activated by Rta.

scholarly journals GLTSCR2/PICT-1, a Putative Tumor Suppressor Gene Product, Induces the Nucleolar Targeting of the Kaposi's Sarcoma-Associated Herpesvirus KS-Bcl-2 Protein

2009 ◽  
Vol 84 (6) ◽  
pp. 2935-2945 ◽  
Author(s):  
Inna Kalt ◽  
Tatyana Borodianskiy-Shteinberg ◽  
Adi Schachor ◽  
Ronit Sarid
Keyword(s):  
Tumor Suppressor ◽  
Tumor Suppressor Gene ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Suppressor Gene ◽  
Laser Scanning Microscopy ◽  
Nucleolar Localization ◽  
Antiapoptotic Activity ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT KS-Bcl-2, encoded by Kaposi's sarcoma-associated herpesvirus (KSHV), is a structural and functional homologue of the Bcl-2 family of apoptosis regulators. Like several other Bcl-2 family members, KS-Bcl-2 protects cells from apoptosis and autophagy. Using a yeast two-hybrid screen and coimmunoprecipitation assays, we identified a novel KS-Bcl-2-interacting protein, referred to as protein interacting with carboxyl terminus 1 (PICT-1), encoded by a candidate tumor suppressor gene, GLTSCR2. Confocal laser scanning microscopy revealed nucleolar localization of PICT-1, whereas KS-Bcl-2 was located mostly at the mitochondrial membranes with a small fraction in the nucleoli. Ectopic expression of PICT-1 resulted in a large increase in the nucleolar fraction of KS-Bcl-2, and only a minor fraction remained in the cytoplasm. Furthermore, knockdown of endogenous PICT-1 abolished the nucleolar localization of KS-Bcl-2. However, ectopically expressed PICT-1 did not alter the cellular distribution of human Bcl-2. Subsequent analysis mapped the crucial amino acid sequences of both KS-Bcl-2 and PICT-1 required for their interaction and for KS-Bcl-2 targeting to the nucleolus. Functional studies suggest a correlation between nucleolar targeting of KS-Bcl-2 by PICT-1 and reduction of the antiapoptotic activity of KS-Bcl-2. Thus, these studies demonstrate a cellular mechanism to sequester KS-Bcl-2 from the mitochondria and to downregulate its virally encoded antiapoptotic activity. Additional characterization of the interaction of KS-Bcl-2 and PICT-1 is likely to shed light on the functions of both proteins.

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