JVI：中科院微生物所在流感病毒感染和複製研究中取得新進展

導 讀

隨病毒感染宿主的過程中能誘導機體產生大量的長鏈非編碼RNAs（lncRNAs），研究lncRNAs如何在病毒感染中發揮作用，如何調控宿主的抗病毒免疫反應，對於流感病毒跨物種傳播及病毒性疾病的防控將具有指導意義。近日，中科院微生物所葉昕課題組與劉文軍課題組合作，在流感病毒與宿主相互作用研究中取得新進展，發現一條長鏈非編碼RNA（lnc-ISG20）在流感病毒感染和複製過程中發揮關鍵性作用，闡釋了lncRNA-ISG20調控流感病毒的作用靶點及其抑制流感病毒複製的分子機制，揭示lnc-ISG20作為一種新型干擾素誘導基因在宿主抗病毒天然免疫防禦系統中的作用。相關研究於2018年6月13日以"Lnc-ISG20 inhibits influenza A virus replication by enhancing ISG20 expression"為題在線發表於國際期刊Journal of Virology上。

Fig.長鏈非編碼RNA（lnc-ISG20）調控流感病毒感染和複製模式圖

研究背景

A型流感病毒（InfluenzaA virus, IAV）屬於正黏病毒科流感病毒屬。該病毒宿主譜較為廣泛，能感染人、禽類和豬等物種，曾引起多次世界性大流行，持續給人類健康、畜禽養殖造成重大威脅。目前宿主細胞所產生的lncRNAs在流感病毒複製中的功能以及調控抗病毒天然免疫應答的機制尚不清楚。

研究團隊曾發現ISG20通過與流感病毒NP蛋白相互作用以及抑制病毒聚合酶活性來抑制病毒複製，本研究則發現一條長鏈非編碼RNA（lnc-ISG20）在流感病毒感染和複製過程中發揮關鍵性作用。研究證實lnc-ISG20可作為一種競爭性內源性RNA（ceRNA）與miR-326結合，降低其對ISG20 mRNA的抑制作用，從而提高ISG20蛋白水平，達到抑制流感病毒複製的作用。

結果速覽

通過採用RNA深度測序等方法，研究者篩選到了一個與ISG20基因位於相同染色體位點上並被流感病毒WSN/CA04上調的lncRNA（命名為lnc-ISG20）。初步研究表明，lnc-ISG20是一種干擾素誘導基因，具有抑制流感病毒複製的作用，且能上調ISG20的蛋白水平。進一步研究表明，在聚肌胞苷酸（Poly I:C）和仙台病毒處理的A549細胞中，lnc-ISG20過表達可提高ISG20蛋白水平，而lnc-ISG20敲減則降低ISG20蛋白水平。此外，研究證明，lnc-ISG20是以ISG20依賴的方式抑制IAV病毒複製。

由於lnc-ISG20並未影響ISG20 mRNA水平，推測其可能作為ISG20的競爭性內源性RNA（ceRNA）促進ISG20翻譯。研究發現，miR-326是ISG20和lnc-ISG20的共有miRNA，它作用於ISG20 mRNA的3"UTR，抑制 ISG20的翻譯。研究證實，lnc-ISG20可與miR-326結合，使與ISG20 mRNA結合的miR-326的量下降。

總之，本研究證明lnc-ISG20可作為一種ceRNA與miR-326結合，降低其對ISG20 mRNA的抑制作用，從而提高ISG20蛋白水平，達到抑制流感病毒複製的作用。

結 語

研究闡釋了lncRNA-ISG20調控流感病毒的作用靶點及其抑制流感病毒複製的分子機制，揭示lnc-ISG20作為一種新型干擾素誘導基因在宿主抗病毒天然免疫防禦系統中的作用。該研究得到國家重點研發計劃項目及國家自然科學基金等資助。博士研究生柴文佳和副研究員李晶為該論文第一作者，葉昕研究員為文章通訊作者。

ABSTRACT

LncRNAs are involved in many aspects of cellular processes, including 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 293T 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. Overe xpression of lnc-ISG20 inhibited IAV replication, while lnc-ISG20 knockdown favored viral replication, suggesting that ln-ISG20 is inhibitory to IAV replication. Further study indicated that over expression of lnc-ISG20 enhances ISG20 protein levels, while knockdown of lnc-ISG20 reduced ISG20 protein levels in A549 cells induced with polyI: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 competing endogenous RNA to ISG20 to enhance its translation. Indeed, we identified that miR-326 is a mutual miRNA for both ISG20 and lnc-ISG20 that targets the 3′UTR of ISG20 mRNA to inhibitits 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, weidentified that the IAV-upregulated lnc-ISG20 is a novel interferon-stimulating gene that elicits its inhibitory effect on IAV replication by enhancing ISG20 expression. We demonstrated that lnc-ISG20 functions as a ceRNA to bind miR-326to reduce its inhibition on ISG20 translation. Our results revealed the mechanism by which lnc-ISG20 inhibits IAV replication.

IMPRTANCE

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 up-regulated during IAV infection and is also an interferon-stimulated gene. We demonstrated that lnc-ISG20 can enhance ISG20 expression, which inturn 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.

參考文獻：

1.Chai W, Li J, Shangguan Q, Liu Q, Li X, Qi D, Tong X, Liu W, Ye X.Lnc-ISG20inhibits influenza A virus replication by enhancing ISG20 expression.J Virol. 2018 Jun 13. pii: JVI.00539-18.

doi:10.1128/JVI.00539-18.

2.中科院微生物所官網：

微生物所在流感病毒感染和複製研究中獲進展

http://www.cas.cn/syky/201806/t20180626_4655943.shtml

本期編輯：Annabella

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