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Convergence of KSHV Reactivation with EBV latency and cellular growth mediated by the Notch signaling pathway in co-infected cells.

ABSTRACT: Kaposi’s sarcoma-associated herpesvirus (KSHV) is the etiologic agent of primary effusion lymphoma (PEL). All PEL cell lines are infected with KSHV, and 70% are co-infected with Epstein-Barr Virus (EBV). KSHV reactivation from latency requires promoter-specific transactivation by the KSHV Rta protein through interactions with RBP-Jk (CSL), the cellular DNA binding component of the Notch signal transduction pathway. EBV transformation of primary B cells requires EBV nuclear antigen (EBNA)-2 to interact with RBP-Jk to direct the latent viral and cellular gene expression program. Although KSHV Rta and EBV EBNA-2 both require RBP-Jk for transactivation, previous studies have suggested that RBP-Jk-dependent transactivators do not function identically. We have found that the EBV latent protein LMP-1 is expressed in less than 5% of KSHV+/EBV+ PEL cells, but is induced in an Rta-dependent fashion when KSHV reactivates. KSHV Rta transactivates the EBV latency promoters in an RBP-Jk-dependent fashion and forms a ternary complex with RBP-Jk on the promoters. In B cells that are conditionally transformed by EBV alone, we show that KSHV Rta complements a short-term EBNA2 growth deficiency in an autocrine/paracrine manner. Complementaton of EBNA2-deficiency by Rta depends on RBP-Jk and LMP-1, and Rta transactivation is required for optimal growth of KSHV+/EBV+ PEL lines. Our data suggest that Rta can contribute to EBV-driven cellular growth by transactivating RBP-Jk-dependent EBV latency genes. However, our data also suggest that EBNA2 and Rta induce distinct alterations in the cellular proteomes that contribute to growth of infected cells.

ORGANISM(S): Homo sapiens

PROVIDER: GSE21375 | GEO | 2010/12/31

SECONDARY ACCESSION(S): PRJNA126087

REPOSITORIES: GEO

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Project description:Kaposi’s sarcoma-associated herpesvirus (KSHV) is the etiologic agent of primary effusion lymphoma (PEL). All PEL cell lines are infected with KSHV, and 70% are co-infected with Epstein-Barr Virus (EBV). KSHV reactivation from latency requires promoter-specific transactivation by the KSHV Rta protein through interactions with RBP-Jk (CSL), the cellular DNA binding component of the Notch signal transduction pathway. EBV transformation of primary B cells requires EBV nuclear antigen (EBNA)-2 to interact with RBP-Jk to direct the latent viral and cellular gene expression program. Although KSHV Rta and EBV EBNA-2 both require RBP-Jk for transactivation, previous studies have suggested that RBP-Jk-dependent transactivators do not function identically. We have found that the EBV latent protein LMP-1 is expressed in less than 5% of KSHV+/EBV+ PEL cells, but is induced in an Rta-dependent fashion when KSHV reactivates. KSHV Rta transactivates the EBV latency promoters in an RBP-Jk-dependent fashion and forms a ternary complex with RBP-Jk on the promoters. In B cells that are conditionally transformed by EBV alone, we show that KSHV Rta complements a short-term EBNA2 growth deficiency in an autocrine/paracrine manner. Complementaton of EBNA2-deficiency by Rta depends on RBP-Jk and LMP-1, and Rta transactivation is required for optimal growth of KSHV+/EBV+ PEL lines. Our data suggest that Rta can contribute to EBV-driven cellular growth by transactivating RBP-Jk-dependent EBV latency genes. However, our data also suggest that EBNA2 and Rta induce distinct alterations in the cellular proteomes that contribute to growth of infected cells. EREB2-5 cells were transfected and grown in the presence or absence of β-estradiol, as described. Seven days post-transfection, protein extracts were prepared, and 200 ugs. of each were analyzed using the RayBio Human Apoptosis Antibody Array Kit (RayBiotech) as per manufacturers suggestions. The membranes were exposed to autoradiography film for different times to detect the chemiluminescent signals. Images with signals in linear range were quantitated using the program ImageJ [59]. For each membrane, signals from the negative control spots were averaged, and then subtracted from each of the other spots. A signal was considered valid if its value exceeded both its average local background, and the average of all valid negative control values. Valid signals were normalized using the positive control spots (for cellular BID protein). Fold change in signals for each spot were quantitated by dividing by the valid signals for each corresponding spot on the minus β-estradiol membrane. Average fold change, and standard deviation, were calculated for each protein.

Project description:Interaction of the Kaposi’s sarcoma-associated herpesvirus (KSHV) Rta protein with the cellular Notch signaling effector, Recombination Signaling Protein (RBP)-Jk (aka CSL and CBF-1), is essential for viral reactivation from latency. We previously showed that Rta binds to a DNA motif repeated in the viral Mta promoter (called “CANT” or Rta-c) to stimulate RBP-Jk DNA binding, and distinguished Rta from the activated Notch-1 protein. To determine whether Rta’s mechanism would apply generally to other viral promoters, we employed chromatin immunoprecipitation/deep sequencing (ChIP/Seq) to identify Rta and RBP-Jk binding sites across the KSHV genome. We show that RBP-Jk binds nearly exclusively to unique genome sites during latency and reactivation. Many, but not all, reactivation-specific RBP-Jk peaks were associated with Rta bound to single Rta-c motifs. Other motifs that were over-represented with stimulated RBP-Jk DNA binding including those for the cellular DNA binding proteins BCL11A, MNT, MAF B, and TCF12. Four of the top seven motifs that were most over-represented with inhibition of RBP-Jk DNA binding were putative binding sites for the Pit/Oct/Unc (POU) family of proteins, including POU3F3 (Oct-8) and POU5F1 (Oct-4). Interestingly, two other POU motifs, including one for the POU2F1 (Oct-1) protein, are associated with inhibition of RBP-Jk DNA binding unless Rta bound to a nearby Rta-c motif. The relative distances between the Rta-c, POU, and RBP-Jk motifs were conserved at reactivation-specific RBP-Jk peaks in three promoters that Rta transactivated, and the Rta-c and Oct-1 motifs overlapped in two of those. The proximity of the Rta-c/Oct-1 motif to an RBP-Jk motif is critical for Rta transactivation of the ORF50AS/KbZIP promoter, and knockdown of Oct-1 protein debilitated reactivation and production of infectious virus. Our data suggest a broad role for POU proteins in regulating DNA binding of RBP-Jk and its associated transactivators.

Project description:Primary effusion lymphomas (PELs) are specifically associated with KSHV/HHV-8 infection, and most frequently occur in HIV-positive individuals as lymphomatous effusions in the serous cavities without a detectable solid tumor mass. Most PELs have concomitant EBV infection, suggesting that EBV is an important pathogenetic co-factor, although other as yet unidentified cofactors, such as cellular genetic alterations, are also likely to play a role. Lymphomatous effusions that lack KSHV also occur; these are frequently EBV-associated in the setting of HIV infection. Here we used gene expression profile analysis to determine the viral impact on cellular gene expression and the pathogenesis of these lymphomatous effusions. We used the Affymetrix HG-U133A microarray to analyze the gene expression profile of these effusion lymphomas (three virologic groups: KSHV-positive EBV-positive PELs, KSHV-positive EBV-negative PELs and KSHV-negative EBV-positive lymphomatous effusions). Nine cell lines derived from patients with lymphomatous effusions (three from each virologic group and each cell line was done in duplicates.) and three PEL patient samples were used in the study. Our results suggest that KSHV-positive PELs are very different from KSHV-negative lymphomatous effusions, and the genes that are differentially expressed include apoptosis regulators, cell cycle regulators, transcriptional factors and signal transduction regulators. KSHV clearly plays a dominant role in the phenotype of PEL. Within the KSHV-positive PELs, two subgroups can be identified, which were correlated with their EBV viral status. Among these genes (45 gene probes), four were regulators of the MAP kinase pathway that were up-regulated in the KSHV-positive, EBV-negative PELs, suggesting that in the absence of EBV, events that lead to the activation of the MAP kinase pathway may act as a cofactor for the development of PEL. Next we determined whether we could predict the viral status of the three primary patient cases of PEL based on the 45 gene probes that were differentially expressed in KSHV-positive cell lines according to EBV status (pt. 1: KSHV-positive, EBV-positive; Pt. 2: KSHV-positive, low proportion of EBV-positive; pt. 3: KSHV-positive EBV-negative), and we could. Samples: KSHV-positive EBV-positive cell lines: BC-1, BC-2, BC-5 KSHV-positive EBV-negative cell lines: BC-3, BCBL-1, PEL-5 KSHV-negative EBV-positive cell lines: IBL4, SM1, BCKN-1 Patient 1: KSHV-positive, EBV-positive Patient 2: KSHV-positive, EBV-positive (low number of positive cells) Patient 3: KSHV-positive, EBV-negative.

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Convergence of KSHV Reactivation with EBV latency and cellular growth mediated by the Notch signaling pathway in co-infected cells.

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