miR-26a exerts broad-spectrum antiviral effects via the enhancement of RIG-I-mediated type I interferon response by targeting USP15

Host innate immunity is an important defense line against virus infection and is precisely regulated by various factors. Studying the mechanism of virus-host interaction is essential to developing novel antivirals. Being one of the key host natural antiviral responses, host small non-coding RNAs (miRNAs) possess promising antiviral potential worthy of study. Herein, we found that miR-26a exerted broad-spectrum antiviral effect against multiple viruses, e.g., Hepatitis E virus, Vesicular Stomatitis Virus, and Sendai Virus. Mechanistically, miR-26a specifically targets 3 ' UTR of mRNA to inhibit USP15 expression. USP15 interacted directly with RIG-I to deubiquitinate K63-linked RIG-I, thus negatively regulating type I interferon (IFN) signaling. Consequently, miR-26a, by downregulating USP15, promotes K63 ubiquitination of RIG-I to enhance type I IFN responses, resulting in an active antiviral state against virus infection. Intriguingly, the activation of type I IFN responses could suppress miR-26a expression, serving as an intrinsic negative feedback loop to avoid dysregulated signal activation. Hence, the broad-spectrum antiviral effects of miR-26a and its mode-of-action enriched the interaction networks between miRNAs and innate immunity, providing insights for the development of broad-spectrum antivirals against viral infection.IMPORTANCEmiR-26a serves as a potent positive regulator of type I interferon (IFN) responses. By inhibiting USP15 expression, miR-26a promotes RIG-I K63-ubiquitination to enhance type I IFN responses, resulting in an active antiviral state against viruses. Being an intricate regulatory network, the activation of type I IFN responses could in turn suppress miR-26a expression to avoid the disordered activation that might result in the so-called "type I interferonopathy." The knowledge gained would be essential for the development of novel antiviral strategies against viral infection. miR-26a serves as a potent positive regulator of type I interferon (IFN) responses. By inhibiting USP15 expression, miR-26a promotes RIG-I K63-ubiquitination to enhance type I IFN responses, resulting in an active antiviral state against viruses. Being an intricate regulatory network, the activation of type I IFN responses could in turn suppress miR-26a expression to avoid the disordered activation that might result in the so-called "type I interferonopathy." The knowledge gained would be essential for the development of novel antiviral strategies against viral infection.