Downregulation of MUS81 expression inhibits cell migration and maintains EBV latent infection through miR‐BART9‐5p in EBV‐associated gastric cancer

Abstract Epstein–Barr virus (EBV) infection is associated with the occurrence and development of gastric cancer (GC). Methyl methanesulfonate and ultraviolet‐sensitive gene 81 (MUS81) is the catalytic component of a structure‐specific endonuclease and plays an important role in chromosomal stability. However, the link between EBV infection and MUS81 remains unclear. In the present study, we found that MUS81 expression was much lower in EBV‐associated GC cells than in EBV‐negative GC. MUS81 acts as an oncogene in GC by inducing the cell migration and proliferation. Western blot and luciferase reporter assays revealed that miR‐BART9‐5p directly targeted MUS81 and downregulated its expression. Additionally, overexpression of MUS81 in EBV‐positive GC cells inhibited the expression of EBV nuclear antigen 1 (EBNA1). EBNA1 is critical for the pathogenesis of EBV‐associated tumors and the maintenance of a stable copy number of the viral genomes. Altogether, these results indicated that the lowering MUS81 expression might be a mechanism by EBV to maintain its latent infection.