Dataset Information

Hepatitis B Virus X Protein Promotes Degradation of SMC5/6 to Enhance HBV Replication.

ABSTRACT: The hepatitis B virus (HBV) regulatory protein X (HBx) activates gene expression from the HBV covalently closed circular DNA (cccDNA) genome. Interaction of HBx with the DDB1-CUL4-ROC1 (CRL4) E3 ligase is critical for this function. Using substrate-trapping proteomics, we identified the structural maintenance of chromosomes (SMC) complex proteins SMC5 and SMC6 as CRL4(HBx) substrates. HBx expression and HBV infection degraded the SMC5/6 complex in human hepatocytes in vitro and in humanized mice in vivo. HBx targets SMC5/6 for ubiquitylation by the CRL4(HBx) E3 ligase and subsequent degradation by the proteasome. Using a minicircle HBV (mcHBV) reporter system with HBx-dependent activity, we demonstrate that SMC5/6 knockdown, or inhibition with a dominant-negative SMC6, enhance HBx null mcHBV-Gluc gene expression. Furthermore, SMC5/6 knockdown rescued HBx-deficient HBV replication in human hepatocytes. These results indicate that a primary function of HBx is to degrade SMC5/6, which restricts HBV replication by inhibiting HBV gene expression.

SUBMITTER: Murphy CM

PROVIDER: S-EPMC5078993 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Hepatitis B Virus X Protein Promotes Degradation of SMC5/6 to Enhance HBV Replication.

Murphy Christopher M CM Xu Yanping Y Li Feng F Nio Kouki K Reszka-Blanco Natalia N Li Xiaodong X Wu Yaxu Y Yu Yanbao Y Xiong Yue Y Su Lishan L

Cell reports 20160901 11

The hepatitis B virus (HBV) regulatory protein X (HBx) activates gene expression from the HBV covalently closed circular DNA (cccDNA) genome. Interaction of HBx with the DDB1-CUL4-ROC1 (CRL4) E3 ligase is critical for this function. Using substrate-trapping proteomics, we identified the structural maintenance of chromosomes (SMC) complex proteins SMC5 and SMC6 as CRL4(HBx) substrates. HBx expression and HBV infection degraded the SMC5/6 complex in human hepatocytes in vitro and in humanized mice ...[more]

PMID: 27626656

Similar Datasets

Project description:Chronic hepatitis B virus (HBV) infection is a major etiologic factor in hepatocellular carcinoma (HCC) pathogenesis, involving effects of chronic liver inflammation and of the weakly oncogenic HBV X protein (pX). pX-mediated hepatocyte transformation requires Polo-like kinase1 (Plk1) activity, but the mechanism is not fully understood. We identified by a genome-wide short hairpin RNA (shRNA) library screen the genes zinc finger, MYM-type 2 (ZNF198) and suppressor of zeste 12 homolog (Drosophila) (SUZ12) whose protein depletion rescues pX-expressing cells from DNA damage-induced apoptosis. ZNF198 and SUZ12 are components of chromatin remodeling complexes and associate with promyelocytic leukemia (PML) nuclear bodies. Knockdown of ZNF198 and SUZ12 by small interfering RNA (siRNA) reduced p53 stability and DNA repair, rescued pX-expressing hepatocytes from DNA damage-induced apoptosis, and increased pX-induced polyploidy and oncogenic transformation, suggesting ZNF198 and SUZ12 have a role in pX-mediated transformation. Interestingly, during pX-mediated transformation the protein but not messenger RNA (mRNA) levels of ZNF198 and SUZ12 progressively decreased, whereas Plk1 levels increased. Inhibition of Plk1 activity restored protein levels of ZNF198 and SUZ12. In addition, transfected Polo-box-domain (PBD) of Plk1 coimmunoprecipitated with ZNF198 and SUZ12, suggesting that these proteins are Plk1 substrates. Elevated Plk1 and reduced protein levels of ZNF198 and SUZ12 were also observed in human liver cancer cell lines derived from HBV-related tumors and in the presence of HBV replication. Importantly, knockdown by siRNA of ZNF198 and SUZ12 enhanced HBV replication.Reduced protein levels of ZNF198 and SUZ12 and elevated Plk1 occur during pX-mediated hepatocyte transformation in human liver cancer cell lines, as well as during HBV replication, underscoring the significance of these genes both in HBV-mediated HCC pathogenesis and HBV replication. We propose Plk1 activity down-regulates ZNF198 and SUZ12, thereby enhancing both HBV replication and pX-mediated oncogenic transformation.

Project description:BackgroundPreS1-binding protein (PreS1BP), recognized as a nucleolar protein and tumor suppressor, influences the replication of various viruses, including vesicular stomatitis virus (VSV) and herpes simplex virus type 1 (HSV-1). Its role in hepatitis B virus (HBV) replication and the underlying mechanisms, however, remain elusive.MethodsWe investigated PreS1BP expression levels in an HBV-replicating cell and animal model and analyzed the impact of its overexpression on viral replication metrics. HBV DNA, covalently closed circular DNA (cccDNA), hepatitis B surface antigen (HBsAg), hepatitis B core antigen (HBcAg), and HBV RNA levels were assessed in HBV-expressing stable cell lines under varying PreS1BP conditions. Furthermore, co-immunoprecipitation and ubiquitination assays were used to detect PreS1BP- hepatitis B virus X protein (HBx) interactions and HBx stability modulated by PreS1BP.ResultsOur study revealed a marked decrease in PreS1BP expression in the presence of active HBV replication. Functional assays showed that PreS1BP overexpression significantly inhibited HBV replication and transcription, evidenced by the reduction in HBV DNA, cccDNA, HBsAg, HBcAg, and HBV RNA levels. At the molecular level, PreS1BP facilitated the degradation of HBx in a dose-dependent fashion, whereas siRNA-mediated knockdown of PreS1BP led to an increase in HBx levels. Subsequent investigations uncovered that PreS1BP accelerated HBx protein degradation via K63-linked ubiquitination in a ubiquitin-proteasome system-dependent manner. Co-immunoprecipitation assays further established that PreS1BP enhances the recruitment of the proteasome 20S subunit alpha 3 (PSMA3) for interaction with HBx, thereby fostering its degradation.ConclusionsThese findings unveil a previously unidentified mechanism wherein PreS1BP mediates HBx protein degradation through the ubiquitin-proteasome system, consequentially inhibiting HBV replication. This insight positions PreS1BP as a promising therapeutic target for future HBV interventions. Further studies are warranted to explore the clinical applicability of modulating PreS1BP in HBV therapy.

Project description:Glucosamine (GlcN), a dietary supplement widely utilized to promote joint health and effective in the treatment of osteoarthritis, is an effective macroautophagy/autophagy activator in vitro and in vivo. Previous studies have shown that autophagy is required for hepatitis B virus (HBV) replication and envelopment. The objective of this study was to determine whether and how GlcN affects HBV replication, using in vitro and in vivo experiments. Our data demonstrated that HBsAg production and HBV replication were significantly increased by GlcN treatment. Confocal microscopy and western blot analysis showed that the amount of autophagosomes and the levels of autophagic markers MAP1LC3/LC3-II and SQSTM1 were clearly elevated by GlcN treatment. GlcN strongly blocked autophagic degradation of HBV virions and proteins by inhibiting lysosomal acidification through its amino group. Moreover, GlcN further promoted HBV replication by inducing autophagosome formation via feedback inhibition of mechanistic target of rapamycin kinase complex 1 (MTORC1) signaling in an RRAGA (Ras related GTP binding A) GTPase-dependent manner. In vivo, GlcN application promoted HBV replication and blocked autophagic degradation in an HBV hydrodynamic injection mouse model. In addition, GlcN promoted influenza A virus, enterovirus 71, and vesicular stomatitis virus replication in vitro. In conclusion, GlcN efficiently promotes virus replication by inducing autophagic stress through its dual effects in suppressing autophagic degradation and inhibiting MTORC1 signaling. Thus, there is a potential risk of enhanced viral replication by oral GlcN intake in chronically virally infected patients.Abbreviations: ACTB: actin beta; ATG: autophagy-related; CMIA: chemiluminescence immunoassay; ConA: concanavalin A; CQ: chloroquine; CTSD: cathepsin D; DAPI: 4',6-diamidino-2-phenylindole; EV71: enterovirus 71; GalN: galactosamine; GFP: green fluorescence protein; GlcN: glucosamine; GNPNAT1: glucosamine-phosphate N-acetyltransferase 1; HBP: hexosamine biosynthesis pathway; HBV: hepatitis B virus; HBcAg: hepatitis B core antigen; HBsAg: hepatitis B surface antigen; HBeAg: hepatitis B e antigen; HBV RI: hepatitis B replicative intermediate; IAV: influenza A virus; LAMP1: lysosomal associated membrane protein 1; LAMTOR: late endosomal/lysosomal adaptor, MAPK and MTOR activator; ManN: mannosamine; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTORC1: mechanistic target of rapamycin kinase complex 1; PHH: primary human hepatocyte; RAB7: RAB7A, member RAS oncogene family; RPS6KB1: ribosomal protein S6 kinase B1; RRAGA: Ras related GTP binding A; RT-PCR: reverse transcriptase polymerase chain reaction; SEM: standard error of the mean; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; UAP1: UDP-N-acetylglucosamine pyrophosphorylase 1; VSV: vesicular stomatitis virus.

Project description:Prior to nuclear export, the hepatitis B virus (HBV) pregenomic RNA may be spliced by the host cell spliceosome to form shorter RNA sequences known as splice variants. Due to deletions in the open reading frames, splice variants may encode novel fusion proteins. Although not essential for HBV replication, the role of splice variants and their novel fusion proteins largely remains unknown. Some splice variants and their encoded novel fusion proteins have been shown to impair or promote wild-type HBV replication in vitro, and although splice variants Sp3 and Sp9 are two of the most common splice variants identified to date, their in vitro replication phenotype and their impact on wild-type HBV replication are unclear. Here, we utilize greater than genome-length Sp3 and Sp9 constructs to investigate their replication phenotype in vitro, and their impact on wild-type HBV replication. We show that Sp3 and Sp9 were incapable of autonomous replication, which was rescued by providing the polymerase and core proteins in trans. Furthermore, we showed that Sp3 had no impact on wild-type HBV replication, whereas Sp9 strongly reduced wild-type HBV replication in co-transfection experiments. Knocking out Sp9 novel precore-surface and core-surface fusion protein partially restored replication, suggesting that these proteins contributed to suppression of wild-type HBV replication, providing further insights into factors regulating HBV replication in vitro.ImportanceThe role of hepatitis B virus (HBV) splice variants in HBV replication and pathogenesis currently remains largely unknown. However, HBV splice variants have been associated with the development of hepatocellular carcinoma, suggesting a role in HBV pathogenesis. Several in vitro co-transfection studies have shown that different splice variants have varying impacts on wild-type HBV replication, perhaps contributing to viral persistence. Furthermore, all splice variants are predicted to produce novel fusion proteins. Sp1 hepatitis B splice protein contributes to liver disease progression and apoptosis; however, the function of other HBV splice variant novel fusion proteins remains largely unknown. We show that Sp9 markedly impairs HBV replication in a cell culture co-transfection model, mediated by expression of Sp9 novel fusion proteins. In contrast, Sp3 had no effect on wild-type HBV replication. Together, these studies provide further insights into viral factors contributing to regulation of HBV replication.

Dataset Information

Hepatitis B Virus X Protein Promotes Degradation of SMC5/6 to Enhance HBV Replication.

Publications

Hepatitis B Virus X Protein Promotes Degradation of SMC5/6 to Enhance HBV Replication.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets