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The aim of the present study was to investigate the clinical characteristics and management of primary renal sinus tumors. We retrospectively analyzed three cases of primary renal sinus tumors. The first patient was a 33-year-old man who presented with right flank pain for 6 months. Based on the imaging results, the patient was diagnosed with renal sinus tumor. The second case was a 34-year-old woman who presented with sudden lumbago in the right flank for 3 days. The imaging results confirmed the diagnosis of right renal angiomyolipoma. The third case was a 55-year-old woman with flank pain, which had persisted for 1 year. The imaging tests revealed lipoma of the left renal sinus. All three cases underwent surgical procedures. The first case was diagnosed with benign angioleiomyoma following pathological analysis. During surgery, the tumor was ablated and the kidney was spared. The second case was scheduled for tumor enucleating, but a nephrectomy was performed due to serious hemorrhaging and a damaged renal pelvis. Pathological analysis identified angiomyolipoma. The third case was scheduled for lipoma enucleating; however, nephrectomy was performed as the tumor encapsulated the renal vascular pedicle. Pathological analysis revealed lipoma. In the three cases, no relapse over 3 years, 10 months and 4 years of follow-up, respectively, was observed. In addition, this review examined previous literature and concluded that the occurrence of tumors in the renal sinus is rare and the majority of such tumors are benign. Furthermore, cases are easily misdiagnosed as renal pelvic tumors. Computed tomography, magnetic resonance imaging and intravenous urography are the best imaging examination methods for differential diagnosis. In conclusion, surgery is the usual approach for the treatment of renal sinus tumors and radical nephrectomy should be performed for malignant tumors. [ABSTRACT FROM AUTHOR]

The Epstein-Barr nuclear antigen 3C (EBNA3C), one of the essential latent antigens for Epstein-Barr virus (EBV)-induced immortalization of primary human B lymphocytes in vitro, has been implicated in regulating cell proliferation and anti-apoptosis via interaction with several cellular and viral factors. Gemin3 (also named DDX20 or DP103) is a member of DEAD RNA helicase family which exhibits diverse cellular functions including DNA transcription, recombination and repair, and RNA metabolism. Gemin3 was initially identified as a binding partner to EBNA2 and EBNA3C. However, the mechanism by which EBNA3C regulates Gemin3 function remains unclear. Here, we report that EBNA3C directly interacts with Gemin3 through its C-terminal domains. This interaction results in increased stability of Gemin3 and its accumulation in both B lymphoma cells and EBV transformed lymphoblastoid cell lines (LCLs). Moreover, EBNA3C promotes formation of a complex with p53 and Gemin3 which blocks the DNA-binding affinity of p53. Small hairpin RNA based knockdown of Gemin3 in B lymphoma or LCL cells remarkably attenuates the ability of EBNA3C to inhibit the transcription activity of p53 on its downstream genes p21 and Bax, as well as apoptosis. These findings provide the first evidence that Gemin3 may be a common target of oncogenic viruses for driving cell proliferation and anti-apoptotic activities. [ABSTRACT FROM AUTHOR]

Cytokine-mediated JAK/STAT signaling controls numerous important biologic responses like immune function, cellular growth, and differentiation. Inappropriate activation of this signaling pathway is associated with a range of malignancies. Kaposi's sarcoma-associated herpesvirus (KSHV) is the infectious viral agent associated with Kaposi's sarcoma and may also contribute to B-cell disorders, which include primary effusion lymphoma (PEL) and multicentric Castleman's disease. However, regulation of cytokine-mediated lymphocytic immune response by KSHV is not fully understood. In this report, we demonstrate that KSHV suppresses the interleukin-4 (IL-4)-stimulated immune response of B-lymphocyte activation and cell proliferation. Moreover, we show that the latency-associated nuclear antigen (LANA) encoded by KSHV is essential for viral blocking of IL-4-induced signaling. LANA reduces phosphorylation of the signal transducers and activators of transcription 6 (STAT6) on Y-641 and concomitantly its DNA binding ability. Importantly, knockdown of endogenous STAT6 dramatically increases the sensitivity of PEL cells to low-serum stress or chemical-mediated cellular apoptosis and reactivation of KSHV from latent replication. Thus, these findings suggest that the IL-4/STAT6 signaling network is precisely controlled by KSHV for survival, maintenance of latency, and suppression of the host cytokine immune response of the virus-infected cells. [ABSTRACT FROM AUTHOR]

Functional inactivation of the von Hippel-Lindau (VHL) tumor suppressor protein is linked to the development of several forms of cancer as well as oncogenic progression like sporadic renal clear-cell carcinomas (RCC). Despite the critical role played by VHL in destruction of hypoxia-inducible factor α (HIFα) via ubiquitin-mediated proteolysis, very little is known about the post-translational modification which regulates VHL activity. Our previous study showed that the SUMO E3 ligase PIASy interacts with VHL and induces VHL SUMOylation on lysine residue 171 (Cai et al, PLoS ONE, 2010, 5(3):e9720). Here we further report that VHL also undergoes ubiquitylation on both lysine residues 171 and 196, which is blocked by PIASy. Moreover, using a VHL-SUMO1 or ubiquitin fusion protein, we found that ubiquitylated VHL is localized predominantly in the cytoplasm, while SUMOylated VHL results in increased VHL protein stability and nuclear redistribution. Interestingly, substitution of lysine 171 and 196 to arginine of VHL abrogates its inhibitory function on the transcriptional activity of HIFα, and tube formation in vitro. This demonstrates that post-translational modifications like ubiquitylation and SUMOylation contributes to VHL protein stability and nucleocytoplasmic shuttling, and that the overall function of VHL in tumor suppression may require a precise and dynamically regulated process which involves protein modification. [ABSTRACT FROM AUTHOR]

The hypoxic microenvironment contributes to embryonic development and tumor progression through stabilization of the potent transcriptional factor HIFα. In normoxia, the tumor suppressor protein VHL acts as an E3 ubiquitin ligase to target HIFα for proteolytic destruction. Increasing evidence shows that VHL is a multifunctional adaptor involved in inhibition of HIFα-dependent and independent cellular processes. However, the molecular effect of hypoxic stress on VHL functions remains elusive. Here we report that PIASy, a SUMO E3 ligase upregulated in hypoxia, interacts with VHL and induces VHL SUMOylation on lysine residue 171. Moreover, PIASy-mediated SUMO1 modification induces VHL oligomerization and abrogates its inhibitory function on tumor cell growth, migration and clonogenicity. Knockdown of PIASy by small interfering RNA leads to reduction of VHL oligomerization and increases HIF1α degradation. These findings reveal a unique molecular strategy for inactivation of VHL under hypoxic stress. [ABSTRACT FROM AUTHOR]

TRIM32 is often aberrantly expressed in many types of cancers. Kaposi’s sarcoma-associated herpesvirus (KSHV) is linked with several human malignancies, including Kaposi’s sarcoma and primary effusion lymphomas (PELs). Increasing evidence has demonstrated the crucial role of KSHV lytic replication in viral tumorigenesis. However, the role of TRIM32 in herpesvirus lytic replication remains unclear. Here, we reveal that the expression of TRIM32 is upregulated by KSHV in latency, and reactivation of KSHV lytic replication leads to the inhibition of TRIM32 in PEL cells. Strikingly, RTA, the master regulator of lytic replication, interacts with TRIM32 and dramatically promotes TRIM32 for degradation via the proteasome systems. Inhibition of TRIM32 induces cell apoptosis and in turn inhibits the proliferation and colony formation of KSHV-infected PEL cells and facilitates the reactivation of KSHV lytic replication and virion production. Thus, our data imply that the degradation of TRIM32 is vital for the lytic activation of KSHV and is a potential therapeutic target for KSHV-associated cancers. IMPORTANCE TRIM32 is associated with many cancers and viral infections; however, the role of TRIM32 in viral oncogenesis remains largely unknown. In this study, we found that the expression of TRIM32 is elevated by Kaposi’s sarcoma-associated herpesvirus (KSHV) in latency, and RTA (the master regulator of lytic replication) induces TRIM32 for proteasome degradation upon viral lytic reactivation. This finding provides a potential therapeutic target for KSHV-associated cancers. [ABSTRACT FROM AUTHOR]

Developing broad-spectrum vaccines and optimal vaccination strategies is crucial to controlling the COVID-19 pandemic. Here, we generated a chimpanzee adenoviral vector-based COVID-19 vaccine carrying broad-spectrum immunogens, modified full-length spike, and conserved T-cell epitopes of SARS-CoV-2, and assessed its immune response in mice through intramuscular (i.m.), intranasal (i.n.), or combined immunization routes (i.m. + i.n., or i.n. + i.m.). Compared to other vaccination strategies, the two combined regimens elicited higher neutralizing antibody (NAb) responses to all variants. Compared to i.n. + i.m. regimen, the i.m. + i.n. regimen stimulated a stronger secondary GC response, which is more pivotal to high-quality antibody production than the primary GC response. Moreover, the i.m. + i.n. regimen was adept at mediating systemic cellular immunity, while the i.n. + i .m. regimen tended to elicit lung tissue-resident memory T (TRM) cell responses. Overall, the two combined regimens induced comprehensive but distinct immune responses consisting of lgA, lgG, NAbs, GC B cells, long-lived plasma cells, TRM cells, and systemic memory T cells, which conferred complete protection against BA.2 infection in hACE2 transgenic mice, and warranted further investigation as potential universal vaccination strategies. IMPORTANCE The development of broad-spectrum SARS-CoV-2 vaccines will reduce the global economic and public health stress from the COVID-19 pandemic. The use of conserved T-cell epitopes in combination with spike antigen that induce humoral and cellular immune responses simultaneously may be a promising strategy to further enhance the broad spectrum of COVID-19 vaccine candidates. Moreover, this research suggests that the combined vaccination strategies have the ability to induce both effective systemic and mucosal immunity, which may represent promising strategies for maximizing the protective efficacy of respiratory virus vaccines. [ABSTRACT FROM AUTHOR]

The article presents the case of a 56-year-old male patient with a medical history of urgency and twice-hourly micturition and who was diagnosed with seminal vesicle carcinoma based on the result of computed tomography (CT).

Hypoxia-inducible factor 1 (HIF-1) is a ubiquitously expressed transcriptional regulator involved in induction of numerous genes associated with angiogenesis and tumor growth. Kaposi's sarcoma, associated with increased angiogenesis, is a highly vascularized, endothelial cell-derived tumor. Previously, we have shown that the latency-associated nuclear antigen (LANA) encoded by Kaposi's sarcoma-associated herpesvirus (KSHV) targets the HIF-1 α suppressors von Hippel-Lindau protein and p53 for degradation via its suppressor of cytokine signaling-box motif, which recruits the EC5S ubiquitin complex. Here we further show that HIF-1 α was aberrantly accumulated in KSHV latently infected primary effusion lymphoma (PEL) cells, as well as HEK293 cells infected with KSHV, and also show that a potential α-helical amino-terminal domain of LANA was important for HIF-1 α nuclear accumulation in normoxic conditions. Moreover, we have now determined that this association was dependent on the residues 46 to 89 of LANA and the oxygen-dependent degradation domain of HIF-1 α. Introduction of specific small interfering RNA against LANA into PEL cells also resulted in a diminished nuclear accumulation of HIF-1 α. Therefore, these data show that LANA can function not only as an inhibitor of HIF-1 α suppressor proteins but can also induce nuclear accumulation of HIF-1 α during KSHV latent infection. [ABSTRACT FROM AUTHOR]

Hypoxia can induce lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV) in primary effusion lymphoma (PEL) cells. However, the molecular mechanism of lytic reactivation of KSHV by hypoxia remains unclear. Here we show that the latency-associated nuclear antigen (LANA), which plays a crucial role in modulating viral and cellular gene expression, directly associated with a low oxygen responder, hypoxia-inducible factor-1α (HIF-1α). LANA enhanced not only the transcriptional activities of HIF-1α but also its mRNA level. Coimmunoprecipitation and immunofluorescence studies documented a physical interaction between LANA and HIF-1α in transiently transfected 293T cells as well as in PEL cell lines during hypoxia. Through sequence analysis, several putative hypoxia response elements (HRE-1 to -6) were identified in the essential lytic gene Rta promoter. Reporter assays showed that HRE-2 (-1130 to -1123) and HRE-5 and HRE-6 (+234 to +241 and +812 to +820, respectively, within the intron sequence) were necessary and sufficient for the LANA-mediated HIF-1α response. Electrophoretic mobility shift assays showed HIF-1α-dependent binding of a LANA protein complex specifically to the HRE-2, -5, and -6 motifs within the promoter regulatory sequences. This study demonstrates that hypoxia-induced KSHV lytic replication is mediated at least in part through cooperation of HIF-1α with LANA bound to the HRE motifs of the Rta promoter. [ABSTRACT FROM AUTHOR]

Aggressive B-cell lymphoma is one of the most common types of blood malignancy. Robust delivery of genes of interest into target cells, long-term gene expression, and minimal risk of secondary effects are highly desirable for translational medicine including gene therapy and studies on gene function. However, efficient gene delivery into viral or nonviral B-lymphoma cells remains a challenge. Here, we report a strategy for inducing foreign gene expression in B-lymphoma cells by using a vector based on the novel parainfluenza virus PIV5-L (a strain isolated from B cells) that enabled us to study and control the function of a gene product within B-lymphoma cells. Using enhanced green fluorescent protein (eGFP) as a reporter, we successfully rescued PIV5-L and established a one-step system to generate PIV5-L virus-like particles (L-VLPs) with efficient delivery into a broad spectrum of susceptible B-lymphoma cell lines, including Epstein-Barr virus (EBV)- or Kaposi’s sarcoma-associated herpesvirus (KSHV)-transformed B-lymphoblastoid cells. Similar to lentiviral vector, the L-VLP highly expressed exogenous genes and remained stable for long periods without obvious negative effects on cell viability. Taken together, these data demonstrate that the PIV5-L-based system provides a potential new strategy for the delivery of desirable genes and the treatment of cancer. [ABSTRACT FROM AUTHOR]

Purpose: As the mechanism of interaction between circular RNAs (circRNAs) and microRNAs (miRNAs) in regulating the development of prostate cancer (PCa) is not clear, this study focuses on investigating these effects. Materials and Methods: Sample tissues were collected from the PCa of patients, and microarray analysis of human circRNAs was conducted. The expression of circ_0001686, hsa_ miR-411-5p (miR-411-5p) were also detected by qRT-PCR. Circ_0001686 and miR-411-5p mimics were transfected into the PCa cell lines (CWR22RV1and LNCaP) and MTT, colony formation, Transwell, and scratch wound assays were used to analyze the biological behaviors of PCa cells. Si-circ_0001686 and ASO-miR-411-5p were used as negative controls, and dual-luciferase reporter assays were performed to verify the interactions among circ_0001686, miR-411-5p, and SMAD3/TGFBR2. The levels of SMAD3 and TGFBR2 in different treated PCa cells were measured by western blot, and in vivo experiments in a nude mouse model were carried out to strengthen the in vitro findings of miR-411-5p. Results: The expression of circ_0001686 was up-regulated, while the expression of miR-411-5p was down-regulated in PCa cells. Moreover, circ_0001686 promoted cell proliferation, migration, and invasion. Molecular mechanism exploration revealed that circ_0001686 could reduce miR-411-5p, affecting the downstream target genes of SMAD3 and TGFBR2. In vitro and in vivo studies verified that miR-411-5p inhibits PCa progression. Conclusions: Circ_0001686 can reduce miR-411-5p to increase the expression of SMAD3/TGFBR2, which consequently promotes the proliferation, invasion, and migration of PCa cells. [ABSTRACT FROM AUTHOR]

Kaposi's sarcoma-associated herpesvirus (KSHV) is tightly linked to at least two lymphoproliferative disorders, primary effusion lymphoma (PEL) and multicentric Castleman's disease (MCD). However, the development of KSHV-mediated lymphoproliferative disease is not fully understood. Here, we generated two recombinant KSHV viruses deleted for the first RBP-Jκ binding site (RTA1st) and all three RBP-Jκ binding sites (RTAall) within the RTA promoter. Our results showed that RTA1st and RTAall recombinant viruses possess increased viral latency and a decreased capability for lytic replication in HEK 293 cells, enhancing colony formation and proliferation of infected cells. Furthermore, recombinant RTA1st and RTAall viruses showed greater infectivity in human peripheral blood mononuclear cells (PBMCs) relative to wt KSHV. Interestingly, KSHV BAC36 wt, RTA1st and RTAall recombinant viruses infected both T and B cells and all three viruses efficiently infected T and B cells in a time-dependent manner early after infection. Also, the capability of both RTA1st and RTAall recombinant viruses to infect CD19+ B cells was significantly enhanced. Surprisingly, RTA1st and RTAall recombinant viruses showed greater infectivity for CD3+ T cells up to 7 days. Furthermore, studies in Telomerase-immortalized human umbilical vein endothelial (TIVE) cells infected with KSHV corroborated our data that RTA1st and RTAall recombinant viruses have enhanced ability to persist in latently infected cells with increased proliferation. These recombinant viruses now provide a model to explore early stages of primary infection in human PBMCs and development of KSHV-associated lymphoproliferative diseases. [ABSTRACT FROM AUTHOR]

High plasma lactate is associated with poor prognosis of many malignancies, but its role in virally mediated cancer progression and underlying molecular mechanisms are unclear. Epstein-Barr virus (EBV), the first human oncogenic virus, causes several cancers, including B-cell lymphoma. Here, we report that lactate dehydrogenase A (LDH-A) expression and lactate production are elevated in EBV-immortalized B lymphoblastic cells, and lactic acid (LA; acidic lactate) at low concentration triggers EBV-infected B-cell adhesion, morphological changes and proliferation in vitro and in vivo. Moreover, LA-induced responses of EBV-infected B cells uniquely occurs in viral latency type III, and it is dramatically associated with the inhibition of global viral microRNAs, particularly the miR-BHRF1 cluster, and the high expression of SMAD3, JUN, and COL1A genes. The introduction of miR-BHRF1-1 blocks the LA-induced effects of EBV-infected B cells. Thus, this may be a novel mechanism to explain EBV-immortalized B lymphoblastic cell malignancy in an LA microenvironment. IMPORTANCE The tumor microenvironment is complicated, and lactate, which is created by cell metabolism, contributes to an acidic microenvironment that facilitates cancer progression. However, how LA operates in virus-associated cancers is unclear. Thus, we studied how EBV (the first tumor virus identified in humans; it is associated with many cancers) upregulates the expression of LDH-A and lactate production in B lymphoma cells. Elevated LA induces adhesion and the growth of EBVinfected B cells by inhibiting viral microRNA transcription. Thus, we offer a novel understanding of how EBV utilizes an acidic microenvironment to promote cancer development. [ABSTRACT FROM AUTHOR]

Kaposi's sarcoma-associated herpesvirus (KSHV; or human herpesvirus 8 [HHV8]) is implicated in the pathogenesis of many human malignancies including Kaposi's sarcoma (KS), multicentric Castleman's disease (MCD), and primary effusion lymphoma (PEL). KSHV infection displays two alternative life cycles, referred to as the latent and lytic or productive cycle. Previously, we have reported that the replication and transcription activator (RTA), a major lytic cycle transactivator, contributes to the development of KSHV latency by inducing latency-associated nuclear antigen (LANA) expression during early stages of infection by targeting RBP-Jκ, the master regulator of the Notch signaling pathway. Here, we generated a bacterial artificial chromosome (BAC) KSHV recombinant virus with a deletion of the RBP-Jκ site within the LANA promoter to evaluate the function of the RBP-Jκ cognate site in establishing primary latent infection. The results showed that genetic disruption of the RBP-Jκ binding site within the KSHV LANA promoter led to enhanced expression of the KSHV-encoded immediate early RTA, resulting in an increase in lytic replication during primary infection of human peripheral blood mononuclear cells (PBMCs). This system provides a powerful tool for use in indentifying additional cellular and viral molecules involved in LANA-mediated latency maintenance during the early stages of KSHV infection. [ABSTRACT FROM AUTHOR]

Activation of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway has been associated with numerous human malignancies, including primary effusion lymphomas (PELs). PEL, a cancerous proliferation of B cells, is caused by Kaposi's sarcoma-associated herpesvirus (KSHV). Previously we identified constitutive phosphorylation of STAT6 on tyrosine 641 (p-STAT6C) in PEL cell lines BC3 and BCBL1; however, the molecular mechanism leading to this activation remains unclear. Here we demonstrate that STAT6 activation tightly correlates with interleukin-13 (IL-13) secretion, JAK1/2 tyrosine phosphorylation, and reduced expression of SHP1 due to KSHV infection. Moreover, p-STAT6C and reduction of SHP1 were also observed in KS patient tissue. Notably, blockade of IL-13 by antibody neutralization dramatically inhibits PEL cell proliferation and survival. Taken together, these results suggest that IL-13/STAT6 signaling is modulated by KSHV to promote host cell proliferation and viral pathogenesis. [ABSTRACT FROM AUTHOR]

Major histocompatibility complex class II (MHC-II) molecules play a central role in adaptive antiviral immunity by presenting viral peptides to CD4+ T cells. Due to their key role in adaptive immunity, many viruses, including Kaposi's sarcoma-associated herpesvirus (KSHV), have evolved multiple strategies to inhibit the MHC-II antigen presentation pathway. The expression of MHC-II, which is controlled mainly at the level of transcription, is strictly dependent upon the binding of the class II transactivator (CIITA) to the highly conserved promoters of all MHC-II genes. The recruitment of CIITA to MHC-II promoters requires its direct interactions with a preassembled MHC-II enhanceosome consisting of cyclic AMP response element-binding protein (CREB) and nuclear factor Y (NF-Y) complex and regulatory factor X (RFX) complex proteins. Here, we show that KSHV-encoded latency-associated nuclear antigen (LANA) disrupts the association of CIITA with the MHC-II enhanceosome by binding to the components of the RFX complex. Our data show that LANA is capable of binding to all three components of the RFX complex, RFX-associated protein (RFXAP), RFX5, and RFX-associated ankyrin-containing protein (RFXANK), in vivo but binds more strongly with the RFXAP component in in vitro binding assays. Levels of MHC-II proteins were significantly reduced in KSHV-infected as well as LANA-expressing B cells. Additionally, the expression of LANA in a luciferase promoter reporter assay showed reduced HLA-DRA promoter activity in a dose-dependent manner. Chromatin immunoprecipitation assays showed that LANA binds to the MHC-II promoter along with RFX proteins and that the overexpression of LANA disrupts the association of CIITA with the MHC-II promoter. These assays led to the conclusion that the interaction of LANA with RFX proteins interferes with the recruitment of CIITA to MHC-II promoters, resulting in an inhibition of MHC-II gene expression. Thus, the data presented here identify a novel mechanism used by KSHV to downregulate the expressions of MHC-II genes. [ABSTRACT FROM AUTHOR]

Hypoxia-inducible factor 1α (HIF-1α) has been frequently implicated in many cancers as well as viral pathogenesis. Kaposi's sarcoma-associated herpesvirus (KSHV) is linked to several human malignancies. It can stabilize HIF-1α during latent infection and undergoes lytic replication in response to hypoxic stress. However, the mechanism by which KSHV controls its latent and lytic life cycle through the deregulation of HIF-1α is not fully understood. Our previous studies showed that the hypoxia-sensitive chromatin remodeler KAP1 was targeted by the KSHV-encoded latency-associated nuclear antigen (LANA) to repress expression of the major lytic replication and transcriptional activator (RTA). Here we further report that an RNA interferencebased knockdown of KAP1 in KSHV-infected primary effusion lymphoma (PEL) cells disrupted viral episome stability and abrogated sub-G1/G1 arrest of the cell cycle while increasing the efficiency of KSHV lytic reactivation by hypoxia or using the chemical 12-O-tetradecanoylphorbol-13-acetate (TPA) or sodium butyrate (NaB). Moreover, KSHV genome-wide screening revealed that four hypoxia-responsive clusters have a high concurrence of both RBP-Jκ and HIF-1α binding sites (RBSHRE) within the same gene promoter and are tightly associated with KAP1. Inhibition of KAP1 greatly enhanced the association of RBP-Jκ with the HIF-1α complex for driving RTA expression not only in normoxia but also in hypoxia. These results suggest that both KAP1 and the concurrence of RBS+HRE within the RTA promoter are essential for KSHV latency and hypoxia-induced lytic reactivation. [ABSTRACT FROM AUTHOR]

Epstein-Barr virus (EBV) is an oncogenic gammaherpesvirus that is implicated in several human malignancies, including Burkitt's lymphoma (BL), posttransplant lymphoproliferative disease (PTLD), nasopharyngeal carcinoma (NPC), and AIDSassociated lymphomas. Epstein-Barr nuclear antigen 3C (EBNA3C), one of the essential EBV latent antigens, can induce mammalian cell cycle progression through its interaction with cell cycle regulators. Aurora kinase B (AK-B) is important for cell division, and deregulation of AK-B is associated with aneuploidy, incomplete mitotic exit, and cell death. Our present study shows that EBNA3C contributes to upregulation of AK-B transcript levels by enhancing the activity of its promoter. Further, EBNA3C also increased the stability of the AK-B protein, and the presence of EBNA3C leads to reduced ubiquitination of AK-B. Importantly, EBNA3C in association with wild-type AK-B but not with its kinase-dead mutant led to enhanced cell proliferation, and AK-B knockdown can induce nuclear blebbing and cell death. This phenomenon was rescued in the presence of EBNA3C. Knockdown of AK-B resulted in activation of caspase 3 and caspase 9, along with poly(ADP-ribose) polymerase 1 (PARP1) cleavage, which is known to be an important contributor to apoptotic signaling. Importantly, EBNA3C failed to stabilize the kinasedead mutant of AK-B compared to wild-type AK-B, which suggests a role for the kinase domain in AK-B stabilization and downstream phosphorylation of the cell cycle regulator retinoblastoma protein (Rb). This study demonstrates the functional relevance of AK-B kinase activity in EBNA3C-regulated B-cell proliferation and apoptosis. [ABSTRACT FROM AUTHOR]

Epstein-Barr virus (EBV) was the first human DNA virus to be associated with cancer. Its oncogenic potential was further demonstrated by its ability to transform primary B lymphocytes in vitro. EBV nuclear antigen 3C (EBNA3C) is one of a small subset of latent antigens critical for the transformation of human primary B lymphocytes. Although EBNA3C has been shown to modulate several cellular functions, additional targets involved in cellular transformation remain to be explored. EBNA3C can recruit key components of the SCFSkp2 ubiquitin ligase complex. In this report, we show that EBNA3C residues 130 to 190, previously shown to bind to the SCFSkp2 complex, also can strongly associate with the c-Myc oncoprotein. Additionally, the interaction of EBNA3C with c-Myc was mapped to the region of c-Myc that includes the highly conserved Skp2 binding domain. Skp2 has been shown to regulate c-Myc stability and also has been shown to function as a coactivator of transcription for c-Myc target genes. We now show that the EBV latent oncoprotein EBNA3C can stabilize c-Myc and that the recruitment of both c-Myc and its cofactor Skp2 to c-Myc-dependent promoters can enhance c-Myc-dependent transcription. This same region of EBNA3C also recruits and modulates the activity of retinoblastoma and p27, both major regulators of the mammalian cell cycle. The inclusion of c-Myc in the group of cellular targets modulated by this domain further accentuates the importance of these critical residues of EBNA3C in bypassing the cell cycle checkpoints. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Kaposi's sarcoma-associated herpesvirus (KSHV) genomes are tethered to the host chromosomes and partitioned faithfully into daughter cells with the host chromosomes. The latency-associated nuclear antigen (LANA) is important for segregation of the newly synthesized viral genomes to the daughter nuclei. Here, we report that the nuclear mitotic apparatus protein (NuMA) and LANA can associate in KSHV-infected cells. In synchronized cells, NuMA and LANA are colocalized in interphase cells and separate during mitosis at the beginning of prophase, reassociating again at the end of telophase and cytokinesis. Silencing of NuMA expression by small interfering RNA and expression of LGN and a dominant-negative of dynactin (P150-CC1), which disrupts the association of NuMA with microtubules, resulted in the loss of KSHV terminal-repeat plasmids containing the major latent origin. Thus, NuMA is required for persistence of the KSHV episomes in daughter cells. This interaction between NuMA and LANA is critical for segregation and maintenance of the KSHV episomes through a temporally controlled mechanism of binding and release during specific phases of mitosis. [ABSTRACT FROM AUTHOR]