ZEB Negatively Regulates the Lytic-Switch BZLF1 Gene Promoter of Epstein-Barr Virus

Kraus, Richard J.; Perrigoue, Jacqueline; Mertz, Janet E.

doi:10.1128/jvi.77.1.199-207.2003

Cited by 68 publications

(89 citation statements)

References 56 publications

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“…These include the ZI, ZII, and ZIII elements, which have been tested in both luciferase and chloramphenicol acetyltransferase reporter systems and with the complete BZLF1 gene (3,14). Mutation of an additional element known as ZV was found to cause a large increase in the response of the Zp promoter to either tetradecanoyl phorbol (3,18,19). This ZV mutation had the largest effect of any Zp mutation tested in luciferase reporter assays, giving an about 8-to 10-fold increase in Zp activity after anti-Ig induction but not making the promoter constitutively active.…”

Section: Resultsmentioning

confidence: 99%

Lytic Cycle Gene Regulation of Epstein-Barr Virus

Amon

Binné

Bryant

et al. 2004

J Virol

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Episomal reporter plasmids containing the Epstein-Barr virus (EBV) oriP sequence stably transfected into Akata Burkitt's lymphoma cells were used to analyze EBV lytic cycle gene regulation. First, we found that the Zp promoter of EBV, but not the Rp promoter, can be activated in the absence of protein synthesis in these oriP plasmids, casting doubt on the immediate early status of Rp. An additional level of regulation of Zp was implied by analysis of a mutation of the ZV element. Second, our analysis of late lytic cycle promoters revealed that the correct relative timing, dependence on ori lyt in cis, and sensitivity to inhibitors of DNA replication were reconstituted on the oriP plasmids. Late promoter luciferase activity from oriP plasmids also incorporating replication-competent ori lyt was phosphonoacetic acid sensitive, a hallmark of EBV late genes. A minimal ori lyt, which only replicates weakly, was sufficient to confer late timing of expression specifically on late promoters. Finally, deletion analysis of EBV late promoter sequences upstream of the transcription start site confirmed that sequences between ؊49 and ؉30 are sufficient for late gene expression, which is dependent on ori lyt in cis. However, the TATT version of the TATA box found in many late genes was not essential for late expression.We recently described a system for studying Epstein-Barr virus (EBV) lytic gene regulation with plasmids stably transfected into the Akata Burkitt's lymphoma cell line (3). The plasmids contain the promoter being studied linked to the luciferase reporter gene and also have the EBV oriP plasmid origin of replication and a selectable marker (hygromycin resistance). Cell lines stably maintaining the plasmids, typically at about 10 copies per cell, can readily be isolated. Akata cells containing EBV can be induced into the lytic cycle by treatment with anti-immunoglobulin (anti-Ig), which cross-links the surface B-cell receptor, providing a rapid and physiologically relevant method for studying the EBV lytic cycle in cell culture (28). This system accurately reconstituted the regulation of the Zp immediate early promoter of EBV and was used to study its regulation in detail (3,5,14). The stably transfected reporter plasmid has an average copy number similar to that of the endogenous EBV genome present in the same cell, the plasmids are assembled into chromatin like EBV, and the reactivation of endogenous virus provides viral lytic gene products that may act in trans at their normal concentrations. These features make the system a good model for studying viral gene regulation, avoiding artifacts associated with transient transfection and incorrect expression levels of regulatory factors. In this study, we extended the use of the system to investigate the Rp promoter and EBV delayed early and late gene promoters.Zp and Rp have been considered to be the immediate early promoters of EBV, but controversy has surrounded the status of Rp, partly because of technical difficulties in mapping the 5Ј end of the RNA from this ...

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Section: Resultsmentioning

confidence: 99%

Lytic Cycle Gene Regulation of Epstein-Barr Virus

Amon

Binné

Bryant

et al. 2004

J Virol

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“…Thus, whether cells contain the latent versus lytic form of viral infection is largely determined by the activity state of the BZLF1 and BRLF1 promoters (Zp and Rp). A number of cellular transcription factors, including Jun, activating transcription factor-2 (ATF-2), Sp1, EGR-1, ZEB-1, MEF-2D, and YY-1, have been shown to regulate the Zp and Rp promoters in vitro (35)(36)(37)(38)(39)(40). Interestingly, in reporter gene assays, the Zp and Rp promoters are essentially silent in most B-cell lines but constitutively active in many epithelial lines, correlating with the propensity of the virus to produce latent infection following infection of B cells and lytic infection following infection of normal epithelial cells.…”

Section: Discussionmentioning

confidence: 99%

Valproic Acid Enhances the Efficacy of Chemotherapy in EBV-Positive Tumors by Increasing Lytic Viral Gene Expression

2006

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EBV infection in tumor cells is generally restricted to the latent forms of viral infection. Switching the latent form of viral infection into the lytic form may induce tumor cell death. We have previously reported that certain chemotherapy agents can increase the amount of lytic viral gene expression in EBV-positive tumor cells. In this report, we have explored the potential utility of valproic acid (VPA), an anti-seizure drug that also has strong histone deacetylase inhibitory activity, for activating lytic viral gene expression in EBVpositive tumors. Although VPA treatment alone induced only a modest increase in the level of lytic viral gene expression, it strongly enhanced the ability of chemotherapeutic agents to induce lytic EBV gene expression in EBV-positive epithelial and lymphoid cells in vitro. Furthermore, VPA enhanced cell killing in vitro by chemotherapeutic agents in lymphoblastoid cells and gastric cells (AGS) containing wild-type EBV. In contrast, VPA did not enhance the cytotoxicity of chemotherapy in lymphoblastoid cells containing a lytic-defective (BZLF1-knockout) form of EBV or in EBV-negative AGS cells. Finally, we found that the combination of VPA and chemotherapy was significantly more effective in inhibiting EBVdriven lymphoproliferative disease in severe combined immunodeficient mice than chemotherapy alone. These results suggest that VPA could potentiate the efficacy of chemotherapy for EBV-positive tumors in patients.

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“…At the simplest level, host transcriptional repressors have been shown to bind to and repress transcription from key lytic phase promoters of EBV (28,37,38,44) and HCMV (4,32,53). Transcriptional repressors act by recruiting histone deacetylases, which remove acetyl groups from specific lysine residues in histones, thus generating higher order chromatin structures which occlude positive-acting transcription factors.…”

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confidence: 99%