The Hepatitis B Virus Nucleocapsid—Dynamic Compartment for Infectious Virus Production and New Antiviral Target

Hepatitis B virus (HBV) is a small enveloped DNA virus which replicates its tiny 3.2 kb genome by reverse transcription inside an icosahedral nucleocapsid, formed by a single ~180 amino acid capsid, or core, protein (Cp). HBV causes chronic hepatitis B (CHB), a severe liver disease responsible for nearly a million deaths each year. Most of HBV’s only seven primary gene products are multifunctional. Though less obvious than for the multi-domain polymerase, P protein, this is equally crucial for Cp with its multiple roles in the viral life-cycle. Cp provides a stable genome container during extracellular phases, allows for directed intracellular genome transport and timely release from the capsid, and subsequent assembly of new nucleocapsids around P protein and the pregenomic (pg) RNA, forming a distinct compartment for reverse transcription. These opposing features are enabled by dynamic post-transcriptional modifications of Cp which result in dynamic structural alterations. Their perturbation by capsid assembly modulators (CAMs) is a promising new antiviral concept. CAMs inappropriately accelerate assembly and/or distort the capsid shell. We summarize the functional, biochemical, and structural dynamics of Cp, and discuss the therapeutic potential of CAMs based on clinical data. Presently, CAMs appear as a valuable addition but not a substitute for existing therapies. However, as part of rational combination therapies CAMs may bring the ambitious goal of a cure for CHB closer to reality.

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Phosphorylation of the Arginine-Rich C-Terminal Domains of the Hepatitis B Virus (HBV) Core Protein as a Fine Regulator of the Interaction between HBc and Nucleic Acid

Viruses ◽

10.3390/v12070738 ◽

2020 ◽

Vol 12 (7) ◽

pp. 738 ◽

Cited By ~ 2

Author(s):

Hugues de Rocquigny ◽

Virgile Rat ◽

Florentin Pastor ◽

Jean Luc Darlix ◽

Christophe Hourioux ◽

...

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Nucleic Acids ◽

Core Protein ◽

Cell Trafficking ◽

Terminal Domain ◽

Capsid Shell ◽

B Virus ◽

Capsid Stability ◽

Terminal Domains

The morphogenesis of Hepatitis B Virus (HBV) viral particles is nucleated by the oligomerization of HBc protein molecules, resulting in the formation of an icosahedral capsid shell containing the replication-competent nucleoprotein complex made of the viral polymerase and the pre-genomic RNA (pgRNA). HBc is a phospho-protein containing two distinct domains acting together throughout the viral replication cycle. The N-terminal domain, (residues 1–140), shown to self-assemble, is linked by a short flexible domain to the basic C-terminal domain (residues 150–183) that interacts with nucleic acids (NAs). In addition, the C-terminal domain contains a series of phospho-acceptor residues that undergo partial phosphorylation and de-phosphorylation during virus replication. This highly dynamic process governs the homeostatic charge that is essential for capsid stability, pgRNA packaging and to expose the C-terminal domain at the surface of the particles for cell trafficking. In this review, we discuss the roles of the N-terminal and C-terminal domains of HBc protein during HBV morphogenesis, focusing on how the C-terminal domain phosphorylation dynamics regulate its interaction with nucleic acids throughout the assembly and maturation of HBV particles.

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Evidence for Multiple Distinct Interactions between Hepatitis B Virus P Protein and Its Cognate RNA Encapsidation Signal during Initiation of Reverse Transcription

PLoS ONE ◽

10.1371/journal.pone.0072798 ◽

2013 ◽

Vol 8 (8) ◽

pp. e72798 ◽

Cited By ~ 6

Author(s):

Hui Feng ◽

Ping Chen ◽

Fei Zhao ◽

Michael Nassal ◽

Kanghong Hu

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Reverse Transcription ◽

P Protein ◽

Encapsidation Signal ◽

B Virus

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Functional Surfaces of the Hepatitis B Virus Capsid

Journal of Virology ◽

10.1128/jvi.01178-09 ◽

2009 ◽

Vol 83 (22) ◽

pp. 11616-11623 ◽

Cited By ~ 29

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.

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Correction: Evidence for Multiple Distinct Interactions between Hepatitis B Virus P Protein and Its Cognate RNA Encapsidation Signal during Initiation of Reverse Transcription

PLoS ONE ◽

10.1371/annotation/aa102795-3d0e-48b2-8898-5862c7d1e34b ◽

2013 ◽

Vol 8 (10) ◽

Cited By ~ 3

Author(s):

Hui Feng ◽

Ping Chen ◽

Fei Zhao ◽

Michael Nassal ◽

Kanghong Hu

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Reverse Transcription ◽

P Protein ◽

Encapsidation Signal ◽

B Virus

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Mapping of Amino Acid Side Chains on the Surface of Hepatitis B Virus Capsids Required for Envelopment and Virion Formation

Journal of Virology ◽

10.1128/jvi.77.1.416-422.2003 ◽

2003 ◽

Vol 77 (1) ◽

pp. 416-422 ◽

Cited By ~ 89

Author(s):

Dirk Ponsel ◽

Volker Bruss

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Core Protein ◽

Culture Media ◽

Side Chains ◽

Core Proteins ◽

Capsid Shell ◽

B Virus ◽

Virion Morphogenesis ◽

Virion Formation

ABSTRACT The crystal structure of recombinant hepatitis B virus (HBV) capsids formed by 240 core proteins has recently been published. We wanted to map sites on the surface of the icosahedral 35-nm particle that are important for nucleocapsid envelopment by HBV surface proteins during virion morphogenesis. For this purpose, we individually mutated 52 amino acids (aa) within the N-terminal 140 aa of the 185-aa long core protein displaying their side chains to the external surface of the capsid to alanine residues. The phenotype of the mutations with respect to virion formation was tested by transcomplementation of a core gene-negative HBV genome in transiently cotransfected cells, immunoprecipitation of nucleocapsids from cells and secreted virions from culture media, and detection of the particles by radioactive endogenous polymerase reactions. Thirteen point mutations impeded nucleocapsid detection by endogenous polymerase reactions. Twenty-seven mutations were compatible with virion formation. Among these were all capsid-forming mutations in the upper half of the spike protruding from the particle shell and two additional triple mutations at tip of the spike. Eleven mutations (S17, F18, L60, L95, K96, F122, I126, R127, N136, A137, and I139) allowed nucleocapsid formation but blocked particle envelopment and virion formation to undetectable levels. These mutations map to a ring-like groove around the base of the spike and to a small area at the capsid surface close to the pores in the capsid shell. These residues are candidate sites for the interaction with envelope proteins during virion morphogenesis.

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