MaHo002: Epstein-Barr virus miRNA BART16 suppresses type I interferon signaling

The prototypic gammaherpesvirus Epstein-Barr virus (EBV) is carried by over 90% of the adult human population. Although infection often proceeds asymptomatically, the virus is causally involved in infectious mononucleosis and various malignancies. Like all herpesviruses, EBV establishes a lifelong latent infection in its human host. To successfully establish a persistent infection and spread to new hosts, EBV needs to avoid clearance by the host immune system. In addition to ~100 proteins, some of which perform immunomodulatory functions, EBV encodes over 40 mature miRNAs. Cellular miRNAs regulate diverse cellular processes, but the functions of the EBV miRNAs remain poorly understood. In this study, we identify EBV-encoded miR-BART16 as a novel viral immune evasion factor that interferes with host type I IFN responses. miR-BART16-5p downregulates the cellular histone acetyltransferase CBP (CREBB-binding protein) by directly targeting the CBP-encoding mRNA. CBP plays an important role in the type I IFN signaling pathway. Inhibiting endogenously expressed miR-BART16 in EBV-transformed B cells and gastric carcinoma cells results in increased CBP levels. Consistent with the important role of CBP in type I IFN signaling, miR-BART16 expression interferes with ISRE-promoter activity and production of interferon-stimulated genes in response to IFN-α treatment. These combined data show that EBV employs miRNAs to modify IFN-induced gene transcription. Given the importance of the host IFN system in the antiviral defence, obstructing this response may provide a way for EBV to favour viral replication and could play an etiological role in EBV-associated malignancies. 293T-ISRE-mCherry cells were lentivirally transduced to coexpress miR-BART16 and the miR-BART19-14 helper cluster or the helper cluster alone as control. Sample versus common reference (cell line HK-1) hybridizations were performed on human whole genome gene expression microarrays V2 (Agilent, Belgium), in balanced dye-swap on 2 biological replicates per group.