Lnc-ISG20 Inhibits Influenza A Virus Replication by Enhancing ISG20 Expression

Abstract

Long noncoding RNAs (lncRNAs) are involved in many aspects of cellular processes, including the antiviral immune response. To identify influenza A virus (IAV)-related lncRNAs, we performed RNA deep sequencing to compare the profiles of lncRNAs in A549 and HEK293T cells with or without IAV infection. We identified an IAV-upregulated lncRNA named lnc-ISG20 because it shares most of its sequence with ISG20. We found that lnc-ISG20 is an interferon-stimulated gene similar to ISG20. Overexpression of lnc-ISG20 inhibited IAV replication, while lnc-ISG20 knockdown favored viral replication, suggesting that lnc-ISG20 is inhibitory to IAV replication. Further study indicated that overexpression of lnc-ISG20 enhances ISG20 protein levels, while knockdown of lnc-ISG20 reduces ISG20 protein levels in A549 cells induced with poly(I·C) and Sendai virus. We demonstrated that lnc-ISG20 inhibits IAV replication in an ISG20-dependent manner. As lnc-ISG20 did not affect the mRNA level of ISG20, we postulated that lnc-ISG20 may function as endogenous RNA competing with ISG20 to enhance its translation. Indeed, we identified that microRNA 326 (miR-326) is a mutual microRNA for both ISG20 and lnc-ISG20 that targets the 3' untranslated region of ISG20 mRNA to inhibit its translation. We confirmed that lnc-ISG20 can bind miR-326, which in turn decreased the amount of miR-326 bound to ISG20 mRNA. In conclusion, we identified that the IAV-upregulated lnc-ISG20 is a novel interferon-stimulated gene that elicits its inhibitory effect on IAV replication by enhancing ISG20 expression. We demonstrated that lnc-ISG20 functions as a competitive endogenous RNA to bind miR-326 to reduce its inhibition of ISG20 translation. Our results revealed the mechanism by which lnc-ISG20 inhibits IAV replication. The replication of influenza A virus is regulated by host factors. However, the mechanisms by which lncRNAs regulate IAV infection are not well understood. We identified that lnc-ISG20 is upregulated during IAV infection and is also an interferon-stimulated gene. We demonstrated that lnc-ISG20 can enhance ISG20 expression, which in turn inhibits IAV replication. Our studies indicate that lnc-ISG20 functions as a competing endogenous RNA that binds miR-326 and reduces its inhibitory effect on ISG20. Taken together, our findings reveal the mechanistic details of lnc-ISG20 negatively regulating IAV replication. These findings indicate that lnc-ISG20 plays an important role during the host antiviral immune response.

A Long Non-coding RNA IVRPIE Promotes Host Antiviral Immune Responses Through Regulating Interferon β1 and ISG Expression

“…Although antiviral signaling pathways in IAV infection have been well understood, the functions of non-coding RNA, especially lncRNA in these processes remain largely unclear. lncRNA NEAT, 7SL, NRAV, lnc-ISG20, and CCR5AS have been reported to regulate the innate immune responses to virus infection (Wang et al, 2007;Zhang et al, 2013;Ouyang et al, 2014;Chai et al, 2018;Kulkarni et al, 2019). In this study, we report a novel human lncRNA termed as IVRPIE, inhibits the IAV infection through promotion of the expression of IFNβ1 and several ISGs, such as IRF1, IFIT1, IFIT3, Mx1, ISG15, and IFI44L.…”

“…For example, 7SL and NEAT1 are involved in modulating HIV-1 posttranscriptional expression (Wang et al, 2007;Zhang et al, 2013). NRAV and lnc-ISG20 were found to affect IAV replication and virulence (Ouyang et al, 2014;Chai et al, 2018). CCR5AS can diminish infection of CD4 + T cells with HIV (Kulkarni et al, 2019).…”

Long noncoding RNAs: Novel regulators of virus‐host interactions

“…In A549 cells treated with poly(I:C) and Sendai virus, lncRNA ISG20 , acting as a competitive endogenous RNA (ceRNA), competes with miRNA‐326, resulting in a decreased abundance of miRNA‐326 at the 3′‐UTR of the ISG20 mRNA. In addition, the reduced binding efficiency of microRNA‐326 to ISG20 mRNA also promotes ISG20 translation and inhibits IAV replication (Figure B) . Similarly, lncRNA‐ BGL3 , acting as a ceRNA, regulates the translation of phosphatase and tensin homolog (PTEN) genes by competitively binding with a series of miRNAs, including miR‐17, miR‐93, miR‐20a, miR‐20b, miR‐106a, and miR‐106b …”

Identification of lncRNA‐155 encoded by MIR155HG as a novel regulator of innate immunity against influenza A virus infection

“…That is, negative regulator of antiviral response (NRAV) can diminish the production of some critical ISGs including IFIT2, IFIT3, IFITM3, and OASL (Ouyang et al, 2014). Lnc-ISG20 can inhibit IAV replication by enhancing ISG20 expression (Chai et al, 2018). Lnc-ISG20 can inhibit IAV replication by enhancing ISG20 expression (Chai et al, 2018).…”

“…IAV-induced upregulation of lncRNA NEAT1 resulted in the activation of IL-8, and its ectopic overexpression enhanced IFN-β production (Ma et al, 2017). Lnc-ISG20 can inhibit IAV replication by enhancing ISG20 expression (Chai et al, 2018). However, the precise role(s) of lncRNAs in IAV pathogenesis still remains elusive.…”