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Interferon-induced degradation of the hepatitis B virus persistence form, cccDNA, depends on ISG20

ABSTRACT: Hepatitis B virus (HBV) persists by depositing a covalently closed circular DNA (cccDNA) in the nucleus of infected cells that cannot be targeted by available antivirals. Cytokine treatments can diminish HBV cccDNA via APOBEC3-mediated deamination. Here we show that overexpression of APOBEC3A alone, however, was not sufficient to reduce cccDNA in HBV-infected cells. This required addition of interferon indicating that cccDNA degradation requires an additional, interferon-stimulated gene (ISG). Transcriptome analyses identified ISG20 as the only type I and II interferon-induced, nucleus-resident protein with annotated nuclease activity. ISG20 expression was detected in human livers in acute, self-limiting but not in chronic hepatitis B. ISG20 depletion abolished the interferon-induced loss of cccDNA, and co-expression of ISG20 and APOBEC3A was sufficient to diminish cccDNA. In conclusion, non-cytolytic HBV cccDNA decline requires induction of a deaminase and nuclease. Our findings highlight that ISGs cooperate for their antiviral function and this cooperativity may be explored for therapeutic targeting.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Hepatocyte, Liver

SUBMITTER: Christian Urban

LAB HEAD: Andreas Pichlmair

PROVIDER: PXD019285 | Pride | 2021-04-22

REPOSITORIES: Pride

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Project description:Hepatitis B virus (HBV) causes both acute and chronic liver inflammation. Approximately 600,000 CHB patients each year die of HBV-related diseases such as cirrhosis and liver cancer. Therefore, CHB remains a global health concern. Although there have been anti-HBV agents for treating CHB, they have some limitations including viral-drug resistance and adverse effects. Type III IFN or IFN-λ is promising to use as anti-HBV agents because of its anti-viral activities like type I IFNs. In addition, the expression of its receptor, IFNLR1, is limited only in epithelial cells including hepatocytes. Thus, treatment with IFN-lambda results in less side effects compared to IFN-alpha treatment. IFN-lambdas have been shown to inhibit the replication of several viruses including IAV, DENV, EMCV, HIV, HCV, and HBV; however, there have been no studies on the effects of IFN-λ3, the highest activity among other subtypes, on HBV replication. Therefore, this study aims to determine antiviral activities of IFN-λ3 against HBV replication and to investigate its molecular mechanism responsible for suppressing HBV propagation. The results showed that HBV transcripts and amount of intracellular HBV DNA were decreased in HepG2.2.15 cells, stable HBV-transfected hepatoblastoma cell line, treated with IFN-λ3 in a dose-dependent manner. This indicated that IFN-λ3 could inhibit HBV replication. Next, we performed quantitative proteomics to investigate the proteome changes in HepG2.2.15 treated with IFN-λ3. The proteins that changed their expressions were involved in several biological processes such as defense to viral infection, immune responses, cell-cell adhesion, transcription, translation, and metabolism. We further confirmed the proteomics results by immunoblotting assay. Consistent with MS data, it found that the expression of OAS3, SAMHD1 and STAT1 were increased as a result of IFN-λ3 stimulation. These results indicated that proteomics results were reproducible and reliable. Finally, we proposed 3 possible mechanisms involved in suppressing HBV replication including i.) IFN-λ3 induced anti-viral proteins affecting many steps in HBV life cycle ii.) IFN-λ3 promoted antigen processing and antigen presentation and iii.) IFN-λ3 rescued RIG-I signaling to promote both type I and type III IFN production.

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Interferon-induced degradation of the hepatitis B virus persistence form, cccDNA, depends on ISG20

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