Dataset Information

Interferon-inducible ribonuclease ISG20 inhibits hepatitis B virus replication through directly binding to the epsilon stem-loop structure of viral RNA.

ABSTRACT: Hepatitis B virus (HBV) replicates its DNA genome through reverse transcription of a viral RNA pregenome. We report herein that the interferon (IFN) stimulated exoribonuclease gene of 20 KD (ISG20) inhibits HBV replication through degradation of HBV RNA. ISG20 expression was observed at basal level and was highly upregulated upon IFN treatment in hepatocytes, and knock down of ISG20 resulted in elevation of HBV replication and attenuation of IFN-mediated antiviral effect. The sequence element conferring the susceptibility of HBV RNA to ISG20-mediated RNA degradation was mapped at the HBV RNA terminal redundant region containing epsilon (?) stem-loop. Furthermore, ISG20-induced HBV RNA degradation relies on its ribonuclease activity, as the enzymatic inactive form ISG20D94G was unable to promote HBV RNA decay. Interestingly, ISG20D94G retained antiviral activity against HBV DNA replication by preventing pgRNA encapsidation, resulting from a consequence of ISG20-? interaction. This interaction was further characterized by in vitro electrophoretic mobility shift assay (EMSA) and ISG20 was able to bind HBV ? directly in absence of any other cellular proteins, indicating a direct ? RNA binding capability of ISG20; however, cofactor(s) may be required for ISG20 to efficiently degrade ?. In addition, the lower stem portion of ? is the major ISG20 binding site, and the removal of 4 base pairs from the bottom portion of ? abrogated the sensitivity of HBV RNA to ISG20, suggesting that the specificity of ISG20-? interaction relies on both RNA structure and sequence. Furthermore, the C-terminal Exonuclease III (ExoIII) domain of ISG20 was determined to be responsible for interacting with ?, as the deletion of ExoIII abolished in vitro ISG20-? binding and intracellular HBV RNA degradation. Taken together, our study sheds light on the underlying mechanisms of IFN-mediated HBV inhibition and the antiviral mechanism of ISG20 in general.

SUBMITTER: Liu Y

PROVIDER: S-EPMC5388505 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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Interferon-inducible ribonuclease ISG20 inhibits hepatitis B virus replication through directly binding to the epsilon stem-loop structure of viral RNA.

Liu Yuanjie Y Nie Hui H Mao Richeng R Mitra Bidisha B Cai Dawei D Yan Ran R Guo Ju-Tao JT Block Timothy M TM Mechti Nadir N Guo Haitao H

PLoS pathogens 20170411 4

Hepatitis B virus (HBV) replicates its DNA genome through reverse transcription of a viral RNA pregenome. We report herein that the interferon (IFN) stimulated exoribonuclease gene of 20 KD (ISG20) inhibits HBV replication through degradation of HBV RNA. ISG20 expression was observed at basal level and was highly upregulated upon IFN treatment in hepatocytes, and knock down of ISG20 resulted in elevation of HBV replication and attenuation of IFN-mediated antiviral effect. The sequence element co ...[more]

PMID: 28399146

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Project description: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.IMPORTANCE 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.

Dataset Information

Interferon-inducible ribonuclease ISG20 inhibits hepatitis B virus replication through directly binding to the epsilon stem-loop structure of viral RNA.

Publications

Interferon-inducible ribonuclease ISG20 inhibits hepatitis B virus replication through directly binding to the epsilon stem-loop structure of viral RNA.

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