The cellular endosomal sorting complex required for transport (ESCRT) machinery participates in membrane scission and cytoplasmic budding of many RNA viruses. Here, we found that expression of dominant negative ESCRT proteins caused a blockade of Epstein-Barr virus (EBV) release and retention of viral BFRF1 at the nuclear envelope. The ESCRT adaptor protein Alix was redistributed and partially colocalized with BFRF1 at the nuclear rim of virus replicating cells. Following transient transfection, BFRF1 associated with ESCRT proteins, reorganized the nuclear membrane and induced perinuclear vesicle formation. Multiple domains within BFRF1 mediated vesicle formation and Alix recruitment, whereas both Bro and PRR domains of Alix interacted with BFRF1. Inhibition of ESCRT machinery abolished BFRF1-induced vesicle formation, leading to the accumulation of viral DNA and capsid proteins in the nucleus of EBV-replicating cells. Overall, data here suggest that BFRF1 recruits the ESCRT components to modulate nuclear envelope for the nuclear egress of EBV.

Rta, an Epstein-Barr virus (EBV)-

DDR2 was differentially upregulated in NPC and modulated by EBV Zta protein. DDR2 may play a role in NPC invasion and serve as a diagnostic and therapeutic target.

Histone deactylase inhibitors (HDACi) are common chemotherapeutic agents that stimulate Epstein-Barr virus (EBV) reactivation; the detailed mechanism remains obscure. In this study, it is demonstrated that PKCd is required for induction of the EBV lytic cycle by HDACi. Inhibition of PKCd abrogates HDACi-mediated transcriptional activation of the Zta promoter and downstream lytic gene expression. Nuclear translocation of PKCd is observed following HDACi stimulation and its overexpression leads to progression of the EBV lytic cycle. Our study suggests that PKCd is a crucial mediator of EBV reactivation and provides a novel insight to study the regulation of the EBV lytic cycle.Epstein-Barr virus (EBV) is a human gammaherpesvirus with both latent and lytic states in its life cycle (Kieff & Rickinson, 2001). EBV reactivation not only produces infectious viral progeny, but also contributes to the development of EBV-related disease (Kieff & Rickinson, 2001). Although the majority of EBV infections in vivo are latent, serological studies suggest that EBV reactivation may occur months or years before the clinical diagnosis of nasopharyngeal carcinoma (NPC), Hodgkin's disease and endemic Burkitt's lymphoma, serving as a risk factor for cancer development (Kieff & Rickinson, 2001). Previous studies have shown that some physiological stimuli and pharmacological agents, including transforming growth factor beta, cross-linking of surface immunoglobulin, phorbol ester, histone deacetylase inhibitors (HDACi) and several genotoxic agents, can induce EBV from latent status into the lytic cycle (Daibata et al., 1994;Davies et al., 1991;Feng & Kenney, 2006; Feng et al., 2002;Schuster et al., 1991).The protein kinase C (PKC) family has been known for a long time to be necessary for EBV reactivation following stimulation with 12-O-tetradecanoyl phorbol 13-acetate (TPA) (Davies et al., 1991) or anti-immunoglobulin treatment (Daibata et al., 1994). The PKC family comprises 11 isozymes, which are classified into three subfamilies according to their structure and regulatory domains activated by calcium or diacylglycerol (DAG) (Newton, 1997). Conventional PKCs (PKCa, bI, bII and c) require calcium and DAG activators, and novel PKCs (PKCd, e, h and g) respond only to DAG and not to calcium (Newton, 1997). However, atypical PKC isoforms (PKCf, i/l and m) are DAG-insensitive (Newton, 1997). Until now, it has not been clear which PKC members are involved in EBV reactivation. The limited information available suggests that PKCs may play an important role during different stages of various virus infections (Constantinescu et al., 1991;Sieczkarski et al., 2003). For example, PKCf or PKCd is required for early infection or TPA-triggered lytic-cycle activation of Kaposi's sarcoma-associated herpesvirus (KSHV) (Deutsch et al., 2004;Naranatt et al., 2003).HDACi, including trichostatin A (TSA), sodium butyrate (SB) and valproic acid, are common agents used to induce the EBV lytic cycle in several EBV-harbouring epithelial and B cells (Chang & Liu, 2...

TSG101 (Tumor susceptibility 101) gene and its aberrantly spliced isoform, termed TSG101∆154-1054, are tightly linked to tumorigenesis in various cancers. The aberrant TSG101∆154-1054 mRNA is generated from cancer-specific re-splicing of mature TSG101 mRNA. The TSG101∆154-1054 protein protects the full-length TSG101 protein from ubiquitin-mediated degradation, implicating TSG101∆154-1054 protein in the progression of cancer. Here, we confirmed that the presence of TSG101∆154-1054 mRNA indeed caused an accumulation of the TSG101 protein in biopsies of human nasopharyngeal carcinoma (NPC), which was recapitulated by the overexpression of TSG101∆154-1054 in the NPC cell line TW01. We demonstrate the potential function of the TSG101∆154-1054 protein in the malignancy of human NPC with scratch-wound healing and transwell invasion assays. By increasing the stability of the TSG101 protein, TSG101∆154-1054 specifically enhanced TSG101-mediated TW01 cell migration and invasion, suggesting the involvement in NPC metastasis in vivo. This finding sheds light on the functional significance of TSG101∆154-1054 generation via re-splicing of TSG101 mRNA in NPC metastasis and hints at its potential importance as a therapeutic target.

NPC shows significant upregulation of OSF-2 and downregulation of pIgR. Expression of OSF-2 is likely to play a role in the pathogenesis of NPC. In addition, expression of OSF-2 and pIgR is disassociated with the expression of their regulatory cytokines in NPC biopsy specimens, suggesting that the tumors may have altered responses to certain cytokines.