Project description:Lytic activation from latency is a key transition point in the life cycle of herpesviruses. Epstein-Barr virus (EBV) is a human herpesvirus that can cause lymphomas, epithelial cancers, and other diseases, most of which require the lytic cycle. While the lytic cycle of EBV can be triggered by chemicals and immunologic ligands, the lytic cascade is only activated when expression of the EBV latency-to-lytic switch protein ZEBRA is turned on. ZEBRA then transcriptionally activates other EBV genes and together with some of those gene products ensures completion of the lytic cycle. However, not every latently-infected cell exposed to a lytic trigger turns expression of ZEBRA on, resulting in responsive and refractory subpopulations. What governs this dichotomy? By examining the nascent transcriptome following exposure to a lytic trigger, we find that several cellular genes are transcriptionally upregulated temporally upstream of ZEBRA. These genes regulate lytic susceptibility to variable degrees in latently-infected cells that respond to mechanistically distinct lytic triggers. While increased expression of these cellular genes defines a pro-lytic state, such upregulation also runs counter to the well-known mechanism of viral nuclease-mediated host shut-off that is activated downstream of ZEBRA. Furthermore, a subset of upregulated cellular genes is transcriptionally repressed downstream of ZEBRA, indicating an additional mode of virus-mediated host shut-off through transcriptional repression. Thus, increased transcription of a set of host genes contributes to a pro-lytic state that allows a subpopulation of cells to support the EBV lytic cycle.
Project description:Epstein-Barr virus (EBV) Rta is a latent-lytic molecular switch evolutionarily conserved in all gamma-herpesviruses. In previous studies, doxycycline-inducible Rta was shown to potently produce an irreversible G1 arrest followed by cellular senescence in 293 cells. Here, we demonstrate that in this system the inducible Rta not only reactivates resident genome of EBV but also that of Kaposi’s sarcoma-associated herpesvirus (KSHV), to similar efficiency. However, Rta-induced senescence program was terminated by the robust viral lytic cycle replication that eventually caused cell death. Furthermore, prior to the abrupt expression of immediate-early protein (EBV BZLF1 or KSHV RTA), Rta simultaneously down-regulates cell cycle activators (c-Myc, CDK6, CCND2) and up-regulates senescence-related genes (p21, 14-3-3s). Since Rta is a viral immediate-early transcriptional activator, it is envisioned that during the initial stage of viral reactivation, Rta may engage to modulate the host transcriptome, to halt cell cycle progression, and to maintain an ideal environment for manufacturing infectious virions. Refer to individual Series. This SuperSeries is composed of the following subset Series: GSE24585: Expression profiling of host genes modulated by Epstein-Barr virus (EBV) Rta in HEK293 cells GSE24586: Expression profiling of host genes modulated by Epstein-Barr virus Rta in nasopharyngeal carcinoma cells
Project description:Epstein-Barr virus (EBV) has a lifelong latency period after initial infection. Rarely, however, when the EBV immediate early gene BZLF1 is expressed by a specific stimulus, the virus switches to the lytic cycle to produce progeny viruses. We found that EBV infection reduced levels of various ceramide species in gastric cancer cells. As ceramide is a bioactive lipid implicated in the infection of various viruses, we assessed the effect of ceramide on the EBV lytic cycle. Treatment with C6-ceramide (C6-Cer) induced an increase in the endogenous ceramide pool and increased production of the viral product as well as BZLF1 expression. Treatment with the ceramidase inhibitor ceranib-2 induced EBV lytic replication with an increase in the endogenous ceramide pool. The glucosylceramide synthase inhibitor Genz-123346 inhibited C6-Cer-induced lytic replication. C6-Cer induced ERK1/2 and CREB phosphorylation, c-JUN expression, and accumulation of the autophagosome marker LC3B. Treatment with MEK1/2 inhibitor U0126 or autophagy initiation inhibitor 3-MA suppressed C6-Cer-induced EBV lytic replication. In contrast, the autophagosome-lysosome fusion inhibitor chloroquine induced BZLF1 expression. Transfection with siCREB reduced ERK1/2 phosphorylation and C6-Cer-induced BZLF1 expression. On the other hand, siJUN transfection did not affect BZLF1 expression. Our results show that increased endogenous ceramide and glycosyl ceramide (GlyCer) following C6-Cer treatment induce EBV lytic replication in gastric cancer cells via ERK1/2 and CREB phosphorylation and autophagosome accumulation.
Project description:Burkitt lymphoma cells can be latently infected with Epstein-Barr virus (EBV). The virus may be activated into its lytic cycle by small molecules, such as sodium butyrate. Other molecules, such as valproate and valpromide, block viral lytic reactivation. These pharmacological agents alter the cellular physiology that controls viral lytic gene expression. Changes in the cellular transcription were measured in response to one activator and two inhibitors of the Epstein-Barr virus lytic cycle in order to identify cellular genes that are potential regulators of the viral life cycle.
Project description:The Epstein-Barr virus (EBV) switches between latent and lytic phases in hosts that are important in developing related diseases. However, the underlying mechanism of how the viral latent-lytic switch is controlled and how EBV itself mediates this regulation remains largely unknown. This study identified the upregulated histone acetyl reader bromodomain-containing protein 7 (BRD7) during EBV latent infection. Based on the ChIP-sequencing of endogenous BRD7 in Burkitt lymphoma cells, we found that EBV drove BRD7 to regulate cellular and viral genomic loci, including the transcriptional activation of c-Myc, a recently reported regulator of EBV latency. Additionally, EBV-mediated BRD7 signals enriched around the FUSE site in chromosome 8, and the enhancer LOC108348026 in the lgH locus, which might activate the c-Myc alleles. Mechanically, EBV-encoded nuclear antigen 1 (EBNA1) bound and recruited BRD7 to colocalize at promotor regions of the related genes, thus serving as cofactors for the maintenance of viral latency. Moreover, the disruption of BRD7 decreased the c-Myc expression, induced the BZLF1 expression, and reactivated the lytic cycle. Our findings reveal the unique role of BRD7 hijacked by EBV in maintaining the viral latency state via chromatin remodeling. The study paved the way for understanding the new molecular mechanism of EBV-induced chromatin remodeling and latent-lytic switch regulation, providing novel therapeutic candidate targets for EBV persistent infection. With establishing persistent infection in most human hosts, EBV is usually at a latent infection state. How the viral latency is maintained in cells remains largely unknown. c-Myc was recently reported to act as a controller of the lytic switch, while whether and how EBV regulates it remains to be explored. Here, we identified that BRD7 is involved in controlling EBV latency. We found that EBV-mediated BRD7 was enriched in both the normal promoter regions and the translocation alleles of c-Myc, and the disruption of BRD7 decreased c-Myc expression to reactivate the lytic cycle. We also demonstrated that EBV-encoded EBNA1 bound to and regulated BRD7. Therefore, we reveal a novel mechanism by which EBV can regulate its infection state by hijacking host BRD7 to target c-Myc. Our findings will help future therapeutic intervention strategies of EBV infection and pathogenesis.
Project description:Epstein Barr virus (EBV) replication contributes to multiple human diseases, including infectious mononucleosis, nasopharyngeal carcinoma, B-cell lymphomas, and oral hairy leukoplakia. We performed systematic quantitative analyses of temporal changes in host and EBV proteins during lytic replication to gain novel insights into virus-host interactions, using conditional Burkitt lymphoma models of type I and II EBV infection. We quantified profiles of >8000 cellular and 69 EBV proteins, including >500 plasma membrane proteins, providing temporal views of the lytic B-cell proteome and EBV virome. Our approach revealed EBV-induced remodelling of cell cycle, innate and adaptive immune pathways, including upregulation of the complement cascade and proteasomal degradation of the B-cell receptor complex, conserved between EBV types I and II. Cross-comparison with proteomic analyses of human cytomegalovirus infection and of a Kaposi sarcoma associated herpesvirus immunoevasin identified host factors targeted by multiple herpesviruses. Our results provide an important resource for studies of EBV replication.
Project description:Nascent transcriptomics reveal cellular pro-lytic factors upregulated upstream of the latency-to-lytic switch protein of Epstein-Barr virus
Project description:RATIONALE: The Epstein Barr virus can cause cancer and lymphoproliferative disorders. Ganciclovir is an antiviral drug that acts against the Epstein Barr virus. Arginine butyrate may make virus cells more sensitive to ganciclovir. Combining ganciclovir and arginine butyrate may kill more Epstein Barr virus cells and tumor cells.
PURPOSE: Phase I trial to study the effectiveness of arginine butyrate plus ganciclovir in treating patients who have cancer or lymphoproliferative disorders that are associated with the Epstein Barr virus.