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• EBV can upregulate the PI3K/AKT pathway through its encoded EBER1 and LMP2A, thereby promoting the expression of YAP1 in EBVaGC cells. • YAP1 enhances the proliferation, migration, autophagy, S-phase accumulation, and anti-apoptotic ability of EBVaGC cells, which may play carcinogenic role in EBVaGC progression. • YAP1 also enhances EBV replication, and TPA and NaB induced EBV lytic reactivation, forming a bidirectional regulatory mechanism with EBV, further promoting the development of EBVaGC. This study aims to explore the role and regulatory mechanism of Yes-associated protein 1 (YAP1) in the development of Epstein-Barr virus-associated gastric cancer (EBVaGC). Here we showed that EBV can upregulate the expression and activity of YAP1 protein through its encoded latent products EBV-encoded small RNA 1 (EBER1) and latent membrane protein 2A (LMP2A), enhancing the malignant characteristics of EBVaGC cells. In addition, we also showed that overexpression of YAP1 induced the expression of EBV encoding latent and lytic phase genes and proteins in the epithelial cell line AGS-EBV infected with EBV, and increased the copy number of the EBV genome, while loss of YAP1 expression reduced the aforementioned indicators. Moreover, we found that YAP1 enhanced EBV lytic reactivation induced by two known activators, 12-O-tetradecanoylhorbol-13-acetate (TPA) and sodium butyrate (NaB). These results indicated a bidirectional regulatory mechanism between EBV and YAP1 proteins, providing new experimental evidence for further understanding the regulation of EBV infection patterns and carcinogenic mechanisms in gastric cancer. [ABSTRACT FROM AUTHOR]

Highlights • The relative expression of miR-BART16 is higher in EBVaGC tissues than cell lines. • Overexpression of miR-BART16 could reduce the LMP1 mRNA and protein levels. • Inhibition the endogenous miR-BART16 increases the LMP1 mRNA and protein level. • BART16 has a vital role on cell proliferation in EBV-associated gastric carcinoma. Abstract Epstein–Barr virus (EBV) is a ubiquitous oncogenic herpesvirus associated with various human tumors. Latent membrane protein (LMP) 1 is considered a key oncoprotein in some EBV-associated tumors, while it is absent in EBV-associated gastric carcinoma (EBVaGC). In the present study, we did not detect the mRNA or the protein expression of LMP1 in 10 EBVaGC tissue samples, but we found that miRNA-BART16 was more abundantly expressed in EBVaGC primary tissues than in cell lines. It has been reported that EBV-encoded miRNA-BART16 can target the 3′-untranslated regions of LMP1 and negatively regulate its expression. When a BART16 inhibitor or mimics were transfected into EBVaGC cell lines, both mRNA and protein levels were changed compared with those in controls. We further investigated the role of miRNA-BART16 in EBVaGC. According to the CCK8 assay, the proliferation of GT38 and GT39 cells increased after treatment with a miRNA-BART16 inhibitor. At the same time, the BART16 inhibitor caused increased accumulation of G2/M phase cells by bromodeoxyuridine and propidium iodide staining analysis. In addition, no obvious difference was observed in apoptosis after treatment with an inhibitor or mimics using annexin V staining. Our findings highlight the viral role of EBV-encoded miRNA-BART16 in regulating oncogenic LMP1 expression and a negative association with the proliferation of EBVaGC. [ABSTRACT FROM AUTHOR]