Repression of the proapoptotic cellular BIK/NBK gene by Epstein-Barr virus antagonizes transforming growth factor ß1-induced B-cell apoptosis.

UNLABELLED: The Epstein-Barr virus (EBV) establishes a lifelong latent infection in humans. EBV infection of primary B cells causes cell activation and proliferation, a process driven by the viral latency III gene expression program, which includes EBV nuclear proteins (EBNAs), latent membrane proteins, and untranslated RNAs, including microRNAs. Some latently infected cells enter the long-lived memory B-cell compartment and express only EBNA1 transiently (Lat I) or no EBV protein at all (Lat 0). Targeting the molecular machinery that controls B-cell fate decisions, including the Bcl-2 family of apoptosis-regulating proteins, is crucial to the EBV cycle of infection. Here, we show that BIK (also known as NBK), which encodes a proapoptotic "sensitizer" protein, is repressed by the EBNA2-driven Lat III program but not the Lat I program. BIK repression occurred soon after infection of primary B cells by EBV but not by a recombinant EBV in which the EBNA2 gene had been knocked out. Ectopic BIK induced apoptosis in Lat III cells by a mechanism dependent on its BH3 domain and the activation of caspases. We show that EBNA2 represses BIK in EBV-negative B-cell lymphoma-derived cell lines and that this host-virus interaction can inhibit the proapoptotic effect of transforming growth factor ß1 (TGF-ß1), a key physiological mediator of B-cell homeostasis. Reduced levels of TGF-ß1-associated regulatory SMAD proteins were bound to the BIK promoter in response to EBV Lat III or ectopic EBNA2. These data are evidence of an additional mechanism used by EBV to promote B-cell survival, namely, the transcriptional repression of the BH3-only sensitizer BIK. IMPORTANCE: Over 90% of adult humans are infected with the Epstein-Barr virus (EBV). EBV establishes a lifelong silent infection, with its DNA residing in small numbers of blood B cells that are a reservoir from which low-level virus reactivation and shedding in saliva intermittently occur. Importantly, EBV DNA is found in some B-cell-derived tumors in which viral genes play a key role in tumor cell emergence and progression. Here, we report for the first time that EBV can shut off a B-cell gene called BIK. When activated by a molecular signal called transforming growth factor ß1 (TGF-ß1), BIK plays an important role in killing unwanted B cells, including those infected by viruses. We describe the key EBV-B-cell molecular interactions that lead to BIK shutoff. These findings further our knowledge of how EBV prevents the death of its host cell during infection. They are also relevant to certain posttransplant lymphomas where unregulated cell growth is caused by EBV genes.

Protein Quantitation and Analysis of Purity.

The accurate quantitation of proteins and an analysis of their purity is essential in numerous areas of scientific research and is a critical factor in many clinical applications. The large number and variety of techniques employed for this purpose is therefore not surprising. The selection of a suitable assay is dependent on such factors as the level of sensitivity required, the presence of interfering agents, and the composition of the protein itself. In this chapter, protocols for the most commonly used protein determination methodologies are outlined, including an overview of the highly sensitive real-time quantitative immuno-polymerase chain reaction assay. In addition, an approach to validate the UV protein absorption assay is outlined, which can be applied to any procedure for method validation.

Bfl-1 is a crucial pro-survival nuclear factor-κB target gene in Hodgkin/Reed-Sternberg cells.

Hodgkin/Reed-Sternberg (H/RS) cells are believed to represent clonal progeny of Germinal Centre B cells that have escaped negative selection by evading apoptosis. Aberrant constitutive activity of the transcription factor NF-κB plays a key role in the pathogenesis of Hodgkin's Lymphoma (HL), conferring a survival advantage on H/RS cells. Bfl-1 is a pro-survival NF-κB target gene from the Bcl-2 family of apoptosis-regulating proteins. Here, we report that bfl-1 (also known as A1 or GRS) is frequently expressed in primary H/RS cells from HL tumor biopsies and that elevated bfl-1 expression is a feature of H/RS derived cell lines. We show that bfl-1 is an NF-κB target gene in this cell context and that this regulation is effected through a p65-binding DNA element located in its promoter. We demonstrate that ectopic Bfl-1 can rescue cultured H/RS cells from apoptosis induced by pharmacological inhibitors of NF-κB, and that knockdown of bfl-1 potentiates the pro-apoptotic effect of these agents. These findings are the first indication that Bfl-1 plays a crucial role in setting the elevated threshold of resistance of this malignant cell type to apoptosis.

Gene Expression Analysis by Reverse Transcription Quantitative PCR.

The reverse transcription quantitative polymerase chain reaction (RT-qPCR) is a rapid detection technology that allows the amplification and quantification of specific RNA transcripts. RT-qPCR has increasingly been adopted for the detection and quantification of H. pylori across a range of sample types and applications. In addition, it is widely used to monitor host gene expression in cells and tissues in response to H. pylori infection . Outlined here is a two-step protocol that can be employed to analyze gene expression in H. pylori or H. pylori-infected samples.

Protein Quantitation and Analysis of Purity.

The accurate quantitation of proteins and an analysis of their purity are essential in numerous areas of scientific research, and is a critical factor in many clinical applications. The large number and variety of techniques employed for this purpose is therefore not surprising. The selection of a suitable assay is dependent on such factors as the level of sensitivity required, the presence of interfering agents, and the composition of the protein itself. Here, protocols for the most commonly used protein determination methodologies are outlined, as well as for the more recently adapted technique of quantitative immuno-Polymerase Chain Reaction.

Infection of pigs in Ireland with lymphotropic gamma-herpesviruses and relationship to postweaning multisystemic wasting syndrome.

Three species of porcine lymphotropic herpesviruses (PLHVs) have been described but there are few reports on the distribution and prevalence of these viruses in domestic pigs. We aimed to determine the PLHV status of Irish commercial pig herds, and to this end spleens taken from 110 healthy adult pigs sourced from 22 geographically distributed farms in Ireland were analysed for PLHV DNA using novel species-specific polymerase chain reaction assays. We now report that PLHV infection is widespread in the Irish domestic pig population and that PLHV-1 infections are most common (74% of all animals tested), followed by PLHV-3 and PLHV-2 (45% and 21%, respectively) and that infections with multiple PLHV species were frequently detected. As the PLHVs are lymphotrophic agents, we also investigated if co-infection with PLHVs was linked to the development of porcine circovirus-2 (PCV2)-associated postweaning mutlisystemic wasting syndrome (PMWS), a disease characterised in part by histopathological lesions in lymphoid tissues. We examined the PLHV infection status of young animals on two farms that were experiencing outbreaks of PMWS. Overall the findings are further evidence of the widespread prevalence of PLHVs in domestic pigs and are a first indication that co-infection with PCV2 and PLHVs does not lead to the development of PMWS in the absence of other cofactors.

Protein quantitation and analysis of purity.

The accurate quantitation of proteins and an analysis of their purity are essential in numerous areas of scientific research, and are a critical factor in many clinical applications. The large and varied number of techniques employed for this purpose is therefore not surprising. The selection of a suitable assay is dependent on factors such as the level of sensitivity required, the presence of interfering agents, and the composition of the protein itself. Here, protocols for the most commonly used protein determination methodologies are outlined, as well as for the more recently adapted technique of quantitative immuno-polymerase chain reaction.