Type-I interferons (IFN-I) are widely used for antiviral immunotherapy in clinic. Therefore, identification of the regulators of IFN-I antiviral activity is important for developing novel targets for IFN-based antiviral therapy. Monocyte chemoattractant protein 1-induced protein 1 (MCPIP1) is critical for cellular inflammatory responses. However, the roles of MCPIP1 in interferons (IFNs)-mediated antiviral immunity are unexplored. In this study, we demonstrate for the first time that MCPIP1 is an important positive regulator of IFNs antiviral activity. We found that MCPIP1 can promote innate antiviral immunity independently of both its RNase and deubiquitinase activity. Furthermore, we reveal that MCPIP1 is an IFN-induced positive feedback signal molecule which promotes IFN-I-mediated antiviral efficacy. Mechanistically, MCPIP1 does not affect the activation of JAK/STAT upstream of IFN-I signaling, but significantly promotes IFN-I signaling by enhancing ISRE promoter activity and expression of interferon stimulated genes (ISGs). And MCPIP1-mediated activation of IFN-I signaling is independently of its RNase and deubiquitinase activity. These findings uncover a novel innate antiviral mechanism mediated by the IFN-MCPIP1 axis, and may provide potential targets for enhancing IFNs antiviral therapy. (C) 2018 Elsevier Inc. All rights reserved.