Effects of Epstein-Barr virus miR-BARTs in modulating intracellular pathways in human lymphoma cells

Burkitt Lymphoma (BL) is a highly aggressive B-cell non-Hodgkin lymphoma associated with the Epstein-Barr virus (EBV) infection in virtually all cases of its endemic African form. EBV was the first human virus found to encode viral miRNAs, clustered in two distinct regions of the viral genome: the BamHI fragment H rightward open reading frame 1 (miR-BHRFs) and the BamHI-A rightward transcripts (miR-BARTs). Although extensively studied in epithelial cancers, the role of EBV miR-BARTs on the pathogenesis of EBV-associated lymphomas is essentially unknown. Therefore, this study sought to investigate the effects of EBV miRs BART7 and BART9 suppression in Akata EBV-positive cells using CRISPR/Cas9-targeted mutagenesis. Overall, both Akata mutants harboring the edited EBV genomes exhibited low levels of viral miRNAs expression, demonstrating the efficacy of the CRISPR/Cas9-mediated knockdown of EBV miR-BART7 and 9. A reduction in cell viability, proliferation, and increased expression of viral lytic genes was found in both mutants. The knockdown of EBV miR-BART7 significantly increased the expression of several RNA binding proteins (RBPs), while the knockdown of EBV miR-BART9 increased the expression of DNA topoisomerases and ubiquitin/proteasome proteins. Our results unravel potential roles for EBV miR-BART7 and miR-BART9 increasing cell proliferation and maintaining viral latency by hijacking critical cellular pathways associated with the viral lytic cycle. (AU)