scholarly journals Hepatitis B Virus Replication and Release Are Independent of Core Lysine Ubiquitination

2009 ◽  
Vol 83 (10) ◽  
pp. 4923-4933 ◽  
Author(s):  
Mayra L. Garcia ◽  
Rushelle Byfield ◽  
Michael D. Robek
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Ubiquitin Ligase ◽  
Core Protein ◽  
Structural Proteins ◽  
Hbv Replication ◽  
Virion Release ◽  
B Virus ◽  
Lysine Residues ◽  
Ubiquitin Conjugation

ABSTRACT Ubiquitin conjugation to lysine residues regulates a variety of protein functions, including endosomal trafficking and degradation. While ubiquitin plays an important role in the release of many viruses, the requirement for direct ubiquitin conjugation to viral structural proteins is less well understood. Some viral structural proteins require ubiquitin ligase activity, but not ubiquitin conjugation, for efficient release. Recent evidence has shown that, like other viruses, hepatitis B virus (HBV) requires a ubiquitin ligase for release from the infected cell. The HBV core protein contains two lysine residues (K7 and K96), and K96 has been suggested to function as a potential ubiquitin acceptor site based on the fact that previous studies have shown that mutation of this amino acid to alanine blocks HBV release. We therefore reexamined the potential connection between core lysine ubiquitination and HBV replication, protein trafficking, and virion release. In contrast to alanine substitution, we found that mutation of K96 to arginine, which compared to alanine is more conserved but also cannot mediate ubiquitin conjugation, does not affect either virus replication or virion release. We also found that the core lysine mutants display wild-type sensitivity to the antiviral activity of interferon, which demonstrates that ubiquitination of core lysines does not mediate the interferon-induced disruption of HBV capsids. However, mutation of K96 to arginine alters the nuclear-cytoplasmic distribution of core, leading to an accumulation in the nucleolus. In summary, these studies demonstrate that although ubiquitin may regulate the HBV replication cycle, these mechanisms function independently of direct lysine ubiquitination of core protein.

Hepatitis C virus core protein inhibits hepatitis B virus replication by downregulating HBx levels via Siah-1-mediated proteasomal degradation during coinfection

2021 ◽  
Vol 102 (12) ◽  
Author(s):  
Sujeong Lee ◽  
Hyunyoung Yoon ◽  
Jiwoo Han ◽  
Kyung Lib Jang
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Core Protein ◽  
Experimental Studies ◽  
Proteasomal Degradation ◽  
Hbv Replication ◽  
Hcv Core Protein ◽  
B Virus

Most clinical and experimental studies have suggested that hepatitis C virus (HCV) is dominant over hepatitis B virus (HBV) during coinfection, although the mechanism remains unclear. Here, we found that HCV core protein inhibits HBV replication by downregulating HBx levels during coinfection in human hepatoma cells. For this effect, HCV core protein increased reactive oxygen species levels in the mitochondria and activated the ataxia telangiectasia mutated-checkpoint kinase two pathway in the nucleus, resulting in an upregulation of p53 levels. Accordingly, HCV core protein induced p53-dependent activation of seven in absentia homolog one expression, an E3 ligase of HBx, resulting in the ubiquitination and proteasomal degradation of HBx. The effect of the HCV core protein on HBx levels was accurately reproduced in both a 1.2-mer HBV replicon and in vitro HBV infection systems, providing evidence for the inhibition of HBV replication by HCV core protein. The present study may provide insights into the mechanism of HCV dominance in HBV- and HCV-coinfected patients.

NIRF, a Novel Ubiquitin Ligase, Inhibits Hepatitis B Virus Replication Through Effect on HBV Core Protein and H3 Histones

2015 ◽  
Vol 34 (5) ◽  
pp. 327-332 ◽  
Author(s):  
Guanhua Qian ◽  
Bin Hu ◽  
Danlin Zhou ◽  
Yanyan Xuan ◽  
Lu Bai ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Virus Replication ◽  
Ubiquitin Ligase ◽  
Core Protein ◽  
B Virus

NIRF, a novel ubiquitin ligase, interacts with hepatitis B virus core protein and promotes its degradation

2011 ◽  
Vol 34 (1) ◽  
pp. 29-36 ◽  
Author(s):  
Guanhua Qian ◽  
Fangmin Jin ◽  
Lei Chang ◽  
Yan Yang ◽  
Huimin Peng ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Ubiquitin Ligase ◽  
Core Protein ◽  
Virus Core ◽  
B Virus

scholarly journals Influence of a Putative Intermolecular Interaction between Core and the Pre-S1 Domain of the Large Envelope Protein on Hepatitis B Virus Secretion

2002 ◽  
Vol 76 (13) ◽  
pp. 6510-6517 ◽  
Author(s):  
Sophie Le Pogam ◽  
Chiaho Shih
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Core Protein ◽  
Wild Type ◽  
The Core ◽  
Virion Release ◽  
Naturally Occurring ◽  
B Virus ◽  
Kinetics Of ◽  
Viral Reverse Transcription

ABSTRACT Virion release of hepatitis B virus (HBV) from hepatocytes is a tightly regulated event. It is a dogma that only the mature HBV genome is preferentially allowed to export from the intracellular compartment (J. Summers and W. S. Mason, Cell 29:403-415, 1982). Recently, an “immature secretion” phenotype of a highly frequent naturally occurring HBV variant containing a leucine residue at amino acid 97 of the core protein was identified. Unlike wild-type HBV, this variant secretes almost equal amounts of mature and immature genomes. This phenomenon is not caused by any instability of core particles or by any deficiency in viral reverse transcription (T. T. Yuan, P. C. Tai, and C. Shih, J. Virol. 73:10122-10128, 1999). In this study, our kinetic analysis of virion secretion of the mutant F97L (phenylalanine to leucine) indicates that the secretion of its immature genome does not occur earlier than that of its mature genome. In addition, the secretion kinetics of the mature genomes are comparable between the wild-type HBV and the mutant F97L. Therefore, the immature secretion phenomenon of mutant F97L is not caused by premature secretion or more efficient secretion. Previously, we hypothesized that the immature secretion phenotype is probably caused by the aberrant interaction between its mutant core and wild-type envelope proteins. Here, we further demonstrated that a pre-S1 envelope mutation at position 119, changing an alanine (A) to a phenylalanine (F), can offset the immature secretion phenotype of the mutant I97L (isoleucine to leucine) and successfully restore the wild-type-like selective export of the mature genome of the double mutant pre-S1-A119F/core-I97L.

scholarly journals Hepatitis B Virus DNA Replication Is Coordinated by Core Protein Serine Phosphorylation and HBx Expression

2005 ◽  
Vol 79 (15) ◽  
pp. 9810-9820 ◽  
Author(s):  
Margherita Melegari ◽  
Sarah K. Wolf ◽  
Robert J. Schneider
Keyword(s):  
Hepatitis B Virus ◽  
Dna Replication ◽  
Hepatitis B ◽  
Viral Replication ◽  
Core Protein ◽  
Regulatory Protein ◽  
Protein A ◽  
Serine Phosphorylation ◽  
Hbv Replication ◽  
B Virus

ABSTRACT The hepatitis B virus (HBV) core protein forms the capsid of viral particles and is essential for viral genome DNA replication and maturation. The C terminus of core protein contains three serines at positions 155, 162, and 170, phosphorylation of which is important for viral DNA replication. We demonstrate that the phosphorylation of these serines is stimulated by the viral HBx protein, a regulatory protein that activates signal transduction pathways and viral replication. HBx is therefore shown to stimulate HBV replication by increasing core serine phosphorylation. Mutational, biochemical, and mixing studies of C-terminal core serine mutants demonstrate that multiple serine phosphorylations occur on the same core protein. Mutation of individual core protein serines is shown to inhibit HBV replication at distinct stages corresponding to encapsidation of viral pregenomic RNA, reverse transcription, and restriction to synthesis of specific DNA replicative intermediates. We therefore demonstrate that a primary target of HBV replication that is regulated by HBx protein corresponds to increased phosphorylation of the viral core protein. We also demonstrate that core phosphorylation mediated by HBx promotes sequential progression of viral replication through the assembly of capsids primed for different stages of DNA synthesis.

scholarly journals Penciclovir is a selective inhibitor of hepatitis B virus replication in cultured human hepatoblastoma cells.

1996 ◽  
Vol 40 (5) ◽  
pp. 1282-1284 ◽  
Author(s):  
B E Korba ◽  
M R Boyd
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Antiviral Agent ◽  
Hbv Dna ◽  
Selective Inhibitor ◽  
Hbv Replication ◽  
Virion Release ◽  
B Virus ◽  
Immunodeficiency Virus ◽  
Untreated Culture

Penciclovir [9-(4-hydroxy-3-hydroxymethylbut-1-yI)guanine], an effective antiherpesvirus agent, was found to be a potent and selective antiviral agent against intracellular hepatitis B virus (HBV) replication (drug concentration at which a 10-fold decrease in HBV DNA from the average level in an untreated culture was observed [EC90], 1.6 microM) and extracellular virion release (EC90, 0.7 microM) by cultured human hepatoblastoma (2.2.15) cells. Acyclovir and three other related 9-alkoxypurines with activity against either herpesviruses or human immunodeficiency virus were uniformly inactive against HBV. The activity of penciclovir is discussed in relation to recent findings related to its mode of action against HBV.

scholarly journals SOX2 Represses Hepatitis B Virus Replication by Binding to the Viral EnhII/Cp and Inhibiting the Promoter Activation

Viruses ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 273
Author(s):  
Hua Yang ◽  
Jiayin Mo ◽  
Qi Xiang ◽  
Peiyi Zhao ◽  
Yunting Song ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Core Protein ◽  
Hepatitis B Surface Antigen ◽  
High Mobility ◽  
Promoter Activation ◽  
New Host ◽  
Rna Transcription ◽  
Hbv Replication ◽  
B Virus

Hepatitis B virus (HBV) replication is controlled by four promoters (preS1, preS2, Cp, and Xp) and two enhancers (EnhI and EnhII). EnhII stimulates Cp activity to regulate the transcriptions of precore, core, polymerase, and pregenomic RNAs, and therefore, EnhII/Cp is essential for the regulation of HBV replication. This study revealed a distinct mechanism underlying the suppression of EnhII/Cp activation and HBV replication. On the one hand, the sex determining region Y box2 (SOX2), a transcription factor, is induced by HBV. On the other hand, SOX2, in turn, represses the expression levels of HBV RNAs, HBV core-associated DNA, hepatitis B surface antigen (HBsAg), and hepatitis B e antigen (HBeAg), thereby playing an inhibitory role during HBV replication. Further studies indicated that SOX2 bound to the EnhII/Cp DNA and repressed the promoter activation. With the deletion of the high mobility group (HMG) domain, SOX2 loses the ability to repress EnhII/Cp activation, viral RNA transcription, HBV core-associated DNA replication, HBsAg and HBeAg production, as well as fails to enter the nucleus, demonstrating that the HMG domain is required for the SOX2-mediated repression of HBV replication. Moreover, SOX2 represses HBsAg and HBeAg secretion in BALB/c mice sera, and attenuates HBV 3.5 kb RNA transcription and hepatitis B virus core protein (HBc) production in the liver tissues, demonstrating that SOX2 suppresses HBV replication in mice. Furthermore, the results revealed that the HMG domain was required for SOX2-mediated repression of HBV replication in the mice. Taken together, the above facts indicate that SOX2 acts as a new host restriction factor to repress HBV replication by binding to the viral EnhII/Cp and inhibiting the promoter activation through the HMG domain.

scholarly journals Functional Surfaces of the Hepatitis B Virus Capsid

2009 ◽  
Vol 83 (22) ◽  
pp. 11616-11623 ◽  
Author(s):  
Alexander Pairan ◽  
Volker Bruss
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Core Protein ◽  
Point Mutations ◽  
Amino Acid Residues ◽  
Virion Release ◽  
P Protein ◽  
B Virus ◽  
Capsid Maturation ◽  
Almost All

ABSTRACT The hepatitis B virus (HBV) core protein (CP) forms the shell of an icosahedral nucleocapsid. In a former work, we identified 11 amino acid residues of CP exposed on the capsid surface by an alanine mutation scan as being important for capsid envelopment. We now introduced several other amino acids at six of these positions and found that almost all 27 tested point mutations at S17, K96, and I126 reproduced the phenotype of the alanine mutation (with only two exceptions): the formation of nucleocapsids and of the viral DNA genome was wild type, but capsid envelopment and virion release were strongly inhibited. This indicates that these side chains have a very specific function during nucleocapsid envelopment. We also identified several CP point mutations (e.g., F122V/S/Y and R127D/G) allowing the formation of capsids but preventing the packaging of pregenomic RNA. The envelopment of such mutant capsids was blocked. Apparently, these CP mutations hampered the recognition/packaging of the pregenome-P-protein complex by CP, a process which is still barely understood, and the mutant capsids devoid of HBV-specific nucleic acid did not express the capsid maturation signal required for envelopment.

Regulation of Hepatitis B Virus Virion Release and Envelopment Timing by Nucleocapsid and Envelope Interactions

2021 ◽  
Author(s):  
Ji Xi ◽  
Haitao Liu ◽  
Jianming Hu
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Capsid Protein ◽  
Envelope Protein ◽  
Critical Role ◽  
Envelope Proteins ◽  
Linker Sequence ◽  
Hbv Replication ◽  
Virion Release ◽  
B Virus

Interactions between the N-terminal (assembly) domain (NTD) and the linker region of the hepatitis B virus (HBV) capsid protein and the large (L) envelope protein are required for virion formation, which occurs via budding of cytoplasmic mature nucleocapsids (NCs) containing the relaxed circular (RC) DNA genome into an intracellular membrane compartment containing viral envelope proteins. L-capsid interactions also negatively regulates covalently closed circular (CCC) DNA formation, which occurs after RC DNA release from mature NCs and nuclear import. We have now found that L could increase RC DNA in cytoplasmic mature NCs that are destabilized due to mutations in the NTD or the linker, even in those that apparently fail to support secretion of complete virions extracellularly. Other mutations in the capsid linker could block the effects of L on both cytoplasmic NC DNA and nuclear CCC DNA. Furthermore, the maturity of RC DNA in cytoplasmic NCs that was enhanced by L or found in secreted virions was modulated by the capsid linker sequence. The level and maturity of the cytoplasmic RC DNA was further influenced by the efficiency of extracellular virion secretion dependent on viral genotype-specific envelope proteins. These results suggest that interactions between the capsid and envelope proteins regulate one or more steps during virion secretion beyond initial capsid envelopment, and highlights the critical role of the capsid linker in regulating capsid-envelope interaction, including the timing of envelopment during NC maturation. Importance Hepatitis B virus (HBV) is a major human pathogen causing serious liver diseases including cancer. The interactions between the HBV capsid and the large (L) envelope protein is required for formation of infectious viral particles and also negatively regulate formation of an HBV DNA episome in the host cell nucleus, which serves as the sole transcriptional template capable of supporting all viral gene expression to sustain HBV replication and therefore, is the molecular basis of HBV persistence. Here, we report evidence indicating that L-capsid interactions modulate the timing of formation of infectious HBV particles during replication and facilitate extracellular release following their formation. Furthermore, a short linker sequence in the capsid protein plays a critical role in these processes as well as controls the amplification of the nuclear episome. These findings inform fundamental mechanisms of HBV replication as well as antiviral development targeting the HBV capsid and DNA episome.

scholarly journals Virus replication and virion export in X-deficient hepatitis B virus transgenic mice

2002 ◽  
Vol 83 (5) ◽  
pp. 991-996 ◽  
Author(s):  
Kurt Reifenberg ◽  
Petra Nusser ◽  
Jürgen Löhler ◽  
Gabriele Spindler ◽  
Christa Kuhn ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Transgenic Mice ◽  
Gene Product ◽  
Core Protein ◽  
Viral Genomes ◽  
Hbv Replication ◽  
B Virus ◽  
High Level

The function of the X protein (pX) in the replication cycle of mammalian hepadnaviruses is enigmatic. Using tissue culture experiments it has been shown that the X gene product is not central to hepatitis B virus (HBV) replication and virion export. However, at present it is still unclear whether this also applies to the in vivo situation. Using a terminally redundant X-deficient HBV DNA construct, transgenic mice were established that exhibited high-level expression of the viral core protein in liver and kidneys. Importantly, replicative DNA intermediates and mature viral genomes could be detected in the liver and serum of these mice, respectively. These findings indicate that, in the in vivo model of transgenic mice, the HBV X (HBx) gene product is not required for HBV replication and virion secretion.

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