Transfection was performed with INTERFERin according to the manufacturer’s instructions.

Neddylation is a posttranslational protein modification that conjugates ubiquitin-like protein neural precursor cell-expressed developmentally downregulated protein 8 (NEDD8) to target proteins and regulates diverse cellular processes. MLN4924, a novel NEDD8 activating enzyme inhibitor, which has emerged as a promising anticancer drug, has a multifaceted function by inhibiting the process of neddylation. However, the potential roles of MLN4924 and neddylation in IFN-beta production remain unknown. In this study, we show that MLN4924 inhibits TLR3/4- and retinoic acid-inducible gene-I-induced IFN-beta expression in different cells, whereas NEDD8 knockdown had no effects on IFN-beta expression. The ability of the MLN4924 to inhibit IFN-beta production was confirmed in vivo, as mice treated with MLN4924 exhibited decreased levels of IFN-beta upon LPS or polyinosinic-polycytidylic acid stimulation. Furthermore, we show that MLN4924 inhibits IFN regulatory factor 3 (IRF3) transcriptional activation and prevents IRF3 binding to IFN-beta promoter. Our findings suggest that MLN4924 inhibits TLR3/4- and retinoic acid-inducible gene-I-induced IFN-beta expression by preventing IRF3 binding to the IFN-beta promoter, with a neddylation-independent manner. Therefore, our results provide new insight into the mechanism of MLN4924 and may have significant implications for the treatment of MLN4924.