Tripartite motif-containing protein 21 is involved in IFN-γ-induced suppression of hepatitis B virus by regulating hepatocyte nuclear factors

초록

The antiviral role of the tripartite motif-containing (TRIM) protein family a member of the E3-ubiquitin ligase family has recently been actively studied. Hepatitis B virus (HBV) infection is a major contributor to liver diseases; however the host factors regulated by cytokine-inducible TRIM21 to suppress HBV remain unclear. In this study we showed the antiviral efficacyof TRIM21 against HBV in hepatoma cell lines primary human hepatocytes isolated from patient liver tissues and mouse model. Using TRIM21 knock-out cells we confirmedthat the antiviral effectsof interferon-gamma which suppress HBV replication are diminished when TRIM21 is deficient.Northern blot analysis confirmeda reduction of HBV RNA levels by TRIM21. Using Luciferase reporter assay we also discovered that TRIM21 decreases the activity of HBV enhancers which play a crucial role in covalently closed circular DNA transcription. The participation of the RING domain and PRY-SPRY domain in the anti-HBV effectof TRIM21 was demonstrated through experiments using deletion mutants. We identifieda novel interaction between TRIM21 and hepatocyte nuclear factor 4α (HNF4α) through co-immunoprecipitation assay. More specificallyubiquitination assay revealed that TRIM21 promotes ubiquitin-mediated proteasomal degradation of HNF4α. HNF1α transcription is down-regulated as a result of the degradation of HNF4α an activator for the HNF1α promoter. Therefore the reduction of key HBV enhancer activators HNF4α and HNF1α by TRIM21 resulted in a decline in HBV transcription ultimately leading to the inhibition of HBV replication. © 2024 Won et al.

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