Background: Expression mechanism of EBV oncogene LMP1 is not fully understood. Results: C/EBP was newly isolated to enhance the LMP1 promoter in our transient assay system. Conclusion: C/EBP transactivate the LMP1 promoter at physiological levels. Significance: This is the first report that showed the significance of C/EBP on LMP1 expression.

Reactivation of the Epstein-Barr virus from latency is dependent on expression of the BZLF1 viral immediate-early protein.The BZLF1 promoter (Zp) normally exhibits only low basal activity but is activated in response to chemical inducers such as 12-O-tetradecanoylphorbol-13-acetate and calcium ionophore. We found that Jun dimerization protein 2 (JDP2) plays a significant role in suppressing Zp activity. Reporter, EMSA, and ChIP assays of a Zp mutant virus revealed JDP2 association with Zp at the ZII cis-element, a binding site for CREB/ATF/AP-1. Suppression of Zp activity by JDP2 correlated with HDAC3 association and reduced levels of histone acetylation. Although introduction of point mutations into the ZII element of the viral genome did not increase the level of BZLF1 production, silencing of endogenous JDP2 gene expression by RNA interference increased the levels of viral early gene products and viral DNA replication. These results indicate that JDP2 plays a role as a repressor of Zp and that its replacement by CREB/ ATF/AP-1 at ZII is crucial to triggering reactivation from latency to lytic replication.The Epstein-Barr virus (EBV) 2 is a human ␥-herpesvirus that predominantly establishes latent infection in B lymphocytes. Only a small percentage of infected cells switch from the latent stage into the lytic cycle to produce progeny viruses. Although the mechanism of EBV reactivation in vivo is not fully understood, it is known to be elicited by treatment of latently infected B cells with chemical or biological reagents, such as 12-O-tetradecanoylphorbol 13-acetate (TPA), calcium ionophore, sodium butyrate, or anti-immunoglobulin, at least in cultured cells. Stimulation of the EBV lytic cascade by any of these leads to expression of two immediate-early genes, BZLF1 and BRLF1.The BZLF1 protein is a transcriptional activator that shares structural similarities to basic leucine zipper (b-Zip) family transcriptional factors and acts as an oriLyt binding protein essential for lytic viral DNA replication. BZLF1 expression alone can trigger the entire reactivation cascade (1-3).Expression of the BZLF1 gene is tightly controlled at the transcriptional level. The BZLF1 promoter (Zp) normally exhibits low basal activity and is activated in response to TPA or the other reagents described above. The minimal sequence of Zp necessary for activation by the inducers is 233 bp in length (4). The region harbors at least three types of cis regulatory elements, referred to as ZI, ZII, and ZIII. Four copies of the ZI element (ZIA-D) are distributed within the minimal Zp. The myocyte enhancer factor 2D binds to ZIA, ZIB, and ZID (5), whereas Sp1 or Sp3 can bind to ZIA, ZIC, and ZID (6). A single ZII element is located near TATA, sharing homology with binding sites for the cyclic AMP-response element-binding protein (CREB), activating transcription factor (ATF), and activator protein-1 (AP-1) family transcriptional factors such as JunB and JunD (7,8). Two copies of the ZIII element (ZIII-A and -B) bind to the BZLF1 protein. Previou...

Latent membrane protein 1 (LMP1) is a major oncogene essential for primary B cell transformation by Epstein-Barr virus (EBV).Previous studies suggested that some transcription factors, such as PU.1, RBP-J, NF-B, and STAT, are involved in this expression, but the underlying mechanism is unclear. Here, we identified binding sites for PAX5, AP-2, and EBF in the proximal LMP1 promoter (ED-L1p). We first confirmed the significance of PU.1 and POU domain transcription factor binding for activation of the promoter in latency III. We then focused on the transcription factors AP-2 and early B cell factor (EBF). Interestingly, among the three AP-2-binding sites in the LMP1 promoter, two motifs were also bound by EBF. Overexpression, knockdown, and mutagenesis in the context of the viral genome indicated that AP-2 plays an important role in LMP1 expression in latency II in epithelial cells. In latency III B cells, on the other hand, the B cell-specific transcription factor EBF binds to the ED-L1p and activates LMP1 transcription from the promoter. IMPORTANCE Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) is crucial for B cell transformation and oncogenesis of other EBVrelated malignancies, such as nasopharyngeal carcinoma and T/NK lymphoma.Its expression is largely dependent on the cell type or condition, and some transcription factors have been implicated in its regulation. However, these previous reports evaluated the significance of specific factors mostly by reporter assay. In this study, we prepared point-mutated EBV at the binding sites of such transcription factors and confirmed the importance of AP-2, EBF, PU.1, and POU domain factors. Our results will provide insight into the transcriptional regulation of the major oncogene LMP1. The Epstein-Barr virus (EBV) is a human gammaherpesvirus that mainly infects and establishes latent infection in B lymphocytes, but it can also infect other types of cells, including NK, T, and epithelial cells. EBV infection has been implicated as a causal factor in a variety of malignancies, and the expression pattern of viral latent genes varies depending on the tissue of origin and the state of the tumors. Neoplasms such as Burkitt lymphomas or gastric carcinomas express only EBV-encoded small RNA (EBER) and EBV nuclear antigen 1 (EBNA1) (type I latency), whereas some Hodgkin lymphomas, nasopharyngeal carcinomas (NPC), and NK/T lymphomas express EBER, EBNA1, latent membrane protein 1 (LMP1), and LMP2 genes (type II latency). In addition to the type II genes, EBNA2, EBNA3, and EBNA-LP are also expressed in immunosuppression-related lymphomas or lymphoblastoid cell lines (LCLs; type III latency). LMP1 constitutively activates cellular signaling through NF-B, mitogen-activated protein, JAK/STAT, and AKT and is believed to be a major oncogene encoded by EBV (1-11).Two promoters regulate LMP1 gene transcription, with mechanisms that differ between type II and type III infection. In latency III in B lymphocytes, LMP1 transcription from the proximal ED-L1 promoter is acti...