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Epstein-Barr virus nuclear antigen 3C (EBNA3C) interacts with the metabolism sensing C-terminal binding protein (CtBP) repressor to upregulate host genes.

ABSTRACT: Epstein-Barr virus (EBV) infection is associated with the development of specific types of lymphoma and some epithelial cancers. EBV infection of resting B-lymphocytes in vitro drives them to proliferate as lymphoblastoid cell lines (LCLs) and serves as a model for studying EBV lymphomagenesis. EBV nuclear antigen 3C (EBNA3C) is one of the genes required for LCL growth and previous work has suggested that suppression of the CDKN2A encoded tumor suppressor p16INK4A and possibly p14ARF is central to EBNA3C's role in this growth transformation. To directly assess whether loss of p16 and/or p14 was sufficient to explain EBNA3C growth effects, we used CRISPR/Cas9 to disrupt specific CDKN2A exons in EBV transformed LCLs. Disruption of p16 specific exon 1α and the p16/p14 shared exon 2 were each sufficient to restore growth in the absence of EBNA3C. Using EBNA3C conditional LCLs knocked out for either exon 1α or 2, we identified EBNA3C induced and repressed genes. By trans-complementing with EBNA3C mutants, we determined specific genes that require EBNA3C interaction with RBPJ or CtBP for their regulation. Unexpectedly, interaction with the CtBP repressor was required not only for repression, but also for EBNA3C induction of many host genes. Contrary to previously proposed models, we found that EBNA3C does not recruit CtBP to the promoters of these genes. Instead, our results suggest that CtBP is bound to these promoters in the absence of EBNA3C and that EBNA3C interaction with CtBP interferes with the repressive function of CtBP, leading to EBNA3C mediated upregulation.

SUBMITTER: Ohashi M

PROVIDER: S-EPMC7993866 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Epstein Barr virus (EBV) nuclear antigen 3C (EBNA3C) is an essential transcription factor for initiating and maintaining human B lymphocyte transformation to lymphoblastoid cell lines (LCLs). To comprehensively identify EBNA3C regulated cell genes in LCLs, oligonucleotide arrays were used to compare RNA abundances in 3 different LCLs transformed by an EBV that conditionally expresses EBNA3C. Cell RNA levels were assessed in actively growing LCLs, under non-permissive or permissive conditions or under non-permissive conditions after transcomplementation with wild type EBNA3C. A two-way ANOVA model with covariates including the 3 different clone effects and the 3 EBNA3C expression levels, identified 550 EBNA3C regulated genes, with False Discovery Rate <0.01 and >1.5 fold change. A seeded Bayesian network analysis of the 80 most significantly EBNA3C regulated genes that changed >1.5 fold, positioned RAC1, LYN and TNF upstream of other EBNA3C regulated genes. Further, Gene Set Enrichment Assay (GSEA) identified EBNA3C regulated genes to be enriched for MAP kinase signaling, cytokine-cytokine receptor interactions, JAK-STAT signaling, and cell adhesion molecule effects, implicating these pathways in LCL growth or survival. Moreover, 106 EBNA3C regulated genes could be placed in protein interaction networks. Since CXCL12 and CXCR4 signaling are implicated in LCL growth and were EBNA3C up-regulated, up-regulation of CXCL12 was validated by qRT-PCR and effects on induced LCL migration were confirmed. EBNA3C regulated genes significantly overlapped with EBNA2 and EBNA3A regulated genes, consistent with a central role for RBP/CSL in these effects. RNAs from three different Lymphoblastoid Cell Lines(LCLs) expressing conditional EBNA3C grown under permissive or non-permissive conditions for 7 days; the same LCLs transcompletemented with EBNA3C expressed in trans at full wild-type level were used to identify EBNA3C regualted cellular genes. Total cell RNAs were hybrdized to Affymetrix U-133 Plus 2.0 microarrays. A two way ANOVA model was developed with covariates including the 3 different clone effects and the 3 EBNA3C expression levels and identified 550 EBNA3C regulated genes.

Project description:Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA-3C) is a large transcriptional regulator essential for EBV-mediated immortalization of B lymphocytes. We previously identified interactions between EBNA-3C and two cellular transcription factors, J kappa and Spi proteins, through which EBNA-3C regulates transcription. To better understand the contribution of these interactions to EBNA-3C function and EBV latency, we examined whether they are conserved in the homologous proteins of nonhuman primate lymphocryptoviruses (LCVs), which bear a strong genetic and biological similarity to EBV. The homologue of EBNA-3C encoded by the LCV that infects baboons (BaLCV) was found to be only 35% identical in sequence to its EBV counterpart. Of particular significance, this homology localized predominantly to the N-terminal half of the molecule, which encompasses the domains in EBNA-3C that interact with J kappa and Spi proteins. Like EBNA-3C, both BaLCV and rhesus macaque LCV (RhLCV) 3C proteins bound to J kappa and repressed transcription mediated by EBNA-2 through its interaction with J kappa. Both nonhuman primate 3C proteins were also able to activate transcription mediated by the Spi proteins in the presence of EBNA-2. Like EBNA-3C, a domain encompassing the putative basic leucine zipper motif of the BaLCV-3C protein directly interacted with both Spi-1 and Spi-B. Surprisingly, a recently identified motif in EBNA-3C that mediates repression was not identifiable in the BaLCV-3C protein. Finally, although the C terminus of BaLCV-3C bears minimal homology to EBNA-3C, it nonetheless contains a C-terminal domain rich in glutamine and proline that was able to function as a potent transcriptional activation domain, as does the C terminus of EBNA-3C. The conservation of these functional motifs despite poor overall homology among the LCV 3C proteins strongly suggests that the interactions of EBNA-3C with J kappa and Spi do indeed play significant roles in the life cycle of EBV.

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Epstein-Barr virus nuclear antigen 3C (EBNA3C) interacts with the metabolism sensing C-terminal binding protein (CtBP) repressor to upregulate host genes.

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