Project description:Certain organs are capable of containing the replication of various types of viruses. In the liver, infection of Hepatitis B virus (HBV), the etiological factor of Hepatitis B and hepatocellular carcinoma (HCC), often remains asymptomatic and leads to a chronic carrier state. Here we investigated how hepatocytes contain HBV replication and promote their own survival by orchestrating a translational defense mechanism via the stress-sensitive SUMO-2/3-specific peptidase SENP3. We found that SENP3 expression level decreased in HBV-infected hepatocytes in various models including HepG2-NTCP cell lines and a humanized mouse model. Downregulation of SENP3 reduced HBV replication and boosted host protein translation. We also discovered that IQGAP2, a Ras GTPase-activating-like protein, is a key substrate for SENP3-mediated de-SUMOylation. Downregulation of SENP3 in HBV infected cells facilitated IQGAP2 SUMOylation and degradation, which leads to suppression of HBV gene expression and restoration of global translation of host genes via modulation of AKT phosphorylation. Thus, The SENP3-IQGAP2 de-SUMOylation axis is a host defense mechanism of hepatocytes that restores host protein translation and suppresses HBV gene expression.
Project description:Certain organs are capable of containing the replication of various types of viruses. In the liver, infection of Hepatitis B virus (HBV), the etiological factor of Hepatitis B and hepatocellular carcinoma (HCC), often remains asymptomatic and leads to a chronic carrier state. Here we investigated how hepatocytes contain HBV replication and promote their own survival by orchestrating a translational defense mechanism via the stress-sensitive SUMO-2/3-specific peptidase SENP3. We found that SENP3 expression level decreased in HBV-infected hepatocytes in various models including HepG2-NTCP cell lines and a humanized mouse model. Downregulation of SENP3 reduced HBV replication and boosted host protein translation. We also discovered that IQGAP2, a Ras GTPase-activating-like protein, is a key substrate for SENP3-mediated de-SUMOylation. Downregulation of SENP3 in HBV infected cells facilitated IQGAP2 SUMOylation and degradation, which leads to suppression of HBV gene expression and restoration of global translation of host genes via modulation of AKT phosphorylation. Thus, The SENP3-IQGAP2 de-SUMOylation axis is a host defense mechanism of hepatocytes that restores host protein translation and suppresses HBV gene expression.
Project description:Hepatitis B virus (HBV) infection could cause hepatitis, liver cirrhosis and hepatocellular carcinoma. HBV-mediated pathogenesis is only partially understood, but X protein (HBx) reportedly possesses oncogenic potential. Exosomes are small membrane vesicles with diverse functions released by various cells including hepatocytes, and HBV harnesses cellular exosome biogenesis and export machineries for virion morphogenesis and secretion. Therefore, HBV infection might cause changes in exosome contents with functional implications for both virus and host. In this project, exosome protein content changes induced by HBV and HBx were quantitatively analyzed by SILAC/LC-MS/MS. Exosomes prepared from SILAC-labeled hepatoma cell line Huh-7 transfected with HBx, wildtype or HBx-null HBV replicon plasmids were analyzed by LC-MS/MS.
Project description:Background and Aims Chronic infection with hepatitis B virus (HBV) has been known to cause liver cirrhosis and hepatocellular carcinoma. Although nucleos(t)ide analogs are mainly used for the treatment of HBV, they require long-term administration and may lead to the emergence of drug resistance. Therefore, to identify targets for the development of novel anti-HBV therapies, we screened HBV-suppressive host factors using RNA-bnding protein (RBP) expression plasmids library. Approach and Results We screened the RBP library by generating overexpressing RBP cell lines and observing anti-HBV effect. As a result, we identified NEDD4-binding protein 1 (N4BP1) as a candidate showing anti-HBV effect. In hepatocellular carcinoma cell lines, overexpression of N4BP1 decreased the relaxed circular DNA (rcDNA) levels, while suppression of N4BP1 expression increased rcDNA levels. Restoring N4BP1 expression in N4BP1 knockout cells regained the anti-HBV effect of N4BP1. Next, we constructed KH-like and RNase domain-deficient mutants of N4BP1 and examined their effects on HBV replication, and found that both the KH-like and RNase domains are required for its anti-HBV effect. N4BP1 suppresses the step where pregenomic RNA (pgRNA) is synthesized in the HBV life cycle by promoting degradation of pgRNA. Transcriptome analyses of primary human hepatocytes overexpressing N4BP1 suggested that N4BP1 may have anti-HBV activity independent of other host factors. Conclusions In summary, N4BP1 was found to be a novel anti-HBV factor. N4BP1 inhibited HBV replication by promoting pgRNA degradation.
Project description:This study aimed to better characterize the repertoire of serum HBV RNAs during chronic HBV infection in humans, which remains understudied. Using RT-PCR, qPCR, RNA-sequencing and immuno-precipitation, we found that (i) >50% of serum samples bore different amounts of HBV replication-derived RNAs (rd-RNAs); (ii) a few samples contained RNAs transcribed from integrated HBV DNA including 5'-HBV-human-3' RNAs (integrant-derived RNAs or id-RNAs) and 5'-human-HBV-3' transcripts as a minority of serum HBV RNAs; (iii) spliced HBV RNAs were abundant in <50% of analyzed samples; (iv) most serum rd-RNAs were polyadenylated via conventional HBV polyadenylation signal; (v) pre-genomic RNA (pgRNA) was the major component of the pool of serum RNAs; (vi) area of HBV positions 1531-1739 had very high RNA reads coverage and thus should be used as a target for detecting serum HBV RNAs; (vii) vast majority of rd-RNAs and pgRNA were associated with HBV virions, but not with unenveloped capsids, exosomes, classic microvesicles or apoptotic vesicles and bodies; (viii) considerable rd-RNAs presence in the circulating immune complexes was found in a few samples; and (ix) serum rcDNA and rd-RNAs should be quantified simultaneously to evaluate HBV replication status and efficacy of anti-HBV therapy with nucleos(t)ide analogs. In summary, sera contain various HBV RNA types of different origin, which are likely secreted via different mechanisms. In addition, since we previously showed that id-RNAs were abundant or predominant HBV RNAs in many of liver and hepatocellular carcinoma tissues comparing to rd-RNAs, there is likely a mechanism favoring the egress of the replication-derived RNAs.