Downregulation of MicroRNA miR-526a by Enterovirus Inhibits RIG-I-Dependent Innate Immune Response

Abstract

Retinoic acid-inducible gene I (RIG-I) is an intracellular RNA virus sensor that induces type I interferon-mediated host-protective innate immunity against viral infection. Although cylindromatosis (CYLD) has been shown to negatively regulate innate antiviral response by removing K-63-linked polyubiquitin from RIG-I, the regulation of its expression and the underlying regulatory mechanisms are still incompletely understood. Here we show that RIG-I activity is regulated by inhibition of CYLD expression mediated by the microRNA miR-526a. We found that viral infection specifically upregulates miR-526a expression in macrophages via interferon regulatory factor (IRF)-dependent mechanisms. In turn, miR-526a positively regulates virus-triggered type I interferon (IFN-I) production, thus suppressing viral replication, the underlying mechanism of which is the enhancement of RIG-I K63-linked ubiquitination by miR-526a via suppression of the expression of CYLD. Remarkably, virusinduced miR-526a upregulation and CYLD downregulation are blocked by enterovirus 71 (EV71) 3C protein, while ectopic miR526a expression inhibits the replication of EV71 virus. The collective results of this study suggest a novel mechanism of the regulation of RIG-I activity during RNA virus infection by miR-526a and suggest a novel mechanism for the evasion of the innate immune response controlled by EV71. IMPORTANCERNA virus infection upregulates the expression of miR-526a in macrophages through IRF-dependent pathways. In turn, miR526a positively regulates virus-triggered type I IFN production and inhibits viral replication, the underlying mechanism of which is the enhancement of RIG-I K-63 ubiquitination by miR-526a via suppression of the expression of CYLD. Remarkably, virus-induced miR-526a upregulation and CYLD downregulation are blocked by enterovirus 71 (EV71) 3C protein; cells with overexpressed miR-526a were highly resistant to EV71 infection. The collective results of this study suggest a novel mechanism of the regulation of RIG-I activity during RNA virus infection by miR-526a and propose a novel mechanism for the evasion of the innate immune response controlled by EV71.

MicroRNA-30c Modulates Type I IFN Responses To Facilitate Porcine Reproductive and Respiratory Syndrome Virus Infection by Targeting JAK1

“…However, MLV suppresses the activation of ISG15 and ISG56 induced by IFNs in MARC-145 cells, implying that other mechanisms might contribute to the impairment of IFN-I signaling during PRRSV infection (43). Cellular miRNAs were shown to be used by viruses to evade IFN-I-mediated antiviral responses in host cells (18,21,44,45). However, whether miRNAs participate in PRRSV-mediated evasion of IFN-I-mediated antiviral responses remains elusive.…”

pol-miR-731, a teleost miRNA upregulated by megalocytivirus, negatively regulates virus-induced type I interferon response, apoptosis and cell cycle arrest

“…To date, 36 Type I IFN-regulated miRNAs have been reported in mammalian systems, targeting genes encoding components of Type I IFN pathway40. Porcine reproductive and respiratory syndrome virus is known to promote infection by upregulating miR-30c, which impairs IFN signaling41, and enterovirus-71 evades the host innate immune response by downregulating the expression of miR-526a, which positively regulates Type I IFN production42. Kaposi’s sarcoma-associated herpesvirus encodes miR-K12-11, which attenuates the IFN response by decreasing I-kappa-B kinase (IKKε)-mediated IRF3/IRF7 phosphorylation and inhibiting the activation of IKKε-dependent ISGs43.…”

Enterovirus 71 inhibits cellular type I interferon signaling by inhibiting host RIG-I ubiquitination

“…Its pathogenicity is likely related to its ability to evade host innate immunity [18,19]. Up to date, many studies suggest that the EV71 inhibit host innate antiviral immunity to facilitate its infection [15,25]. Thus, it is important to understand the mechanisms of EV71 infection against the host immune system.…”

“…Previous studies reported that the elevated level of miR-526a upon virus infections (VSV) led to enhanced RIG-I-mediated IFN-b production by suppressing the expression of CYLD deubiqutinase activity. In contrast, the level of induction of miR-526a by EV71 infection was significantly low with minimal induction of IFN-b [15]. These events promote us to investigate the possibility that removal of polyubiquitination chains from RIG-I upon EV71 infection might contribute to inactivating the RIG-Imediated antiviral response.…”

“…During EV71 infection, RIG-I recognizes viral RNA present in the cytoplasm in a 5'-triphosphate-dependent manner and subsequently recruits the IPS-1 to activate the type I interferon signaling, suggesting essential role of RIG-I in initiating antiviral responses against EV71 [13,14]. Despite the protective role of type I interferon (IFN-b) in EV71 infection, EV71 inoculation is unable to elicit production of these interferons [15]. Recent reports reveal that EV71 is able to escape from innate antiviral responses through post-translational modification or degradation of RIG-I [14,16e19].…”