scholarly journals ATM-Dependent Phosphorylation of Hepatitis B Core Protein in Response to Genotoxic Stress

Viruses ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2438
Author(s):  
Barbora Lubyova ◽  
Eva Tikalova ◽  
Kristyna Krulova ◽  
Jan Hodek ◽  
Ales Zabransky ◽  
...  
Keyword(s):  
Hepatitis B ◽  
Ataxia Telangiectasia ◽  
Core Protein ◽  
Genotoxic Stress ◽  
Phosphorylation Sites ◽  
Hbv Replication ◽  
Etoposide Treatment ◽  
Hbe Antigen ◽  
Threatening Condition ◽  
Life Threatening

Chronic hepatitis caused by infection with the Hepatitis B virus is a life-threatening condition. In fact, 1 million people die annually due to liver cirrhosis or hepatocellular carcinoma. Recently, several studies demonstrated a molecular connection between the host DNA damage response (DDR) pathway and HBV replication and reactivation. Here, we investigated the role of Ataxia-telangiectasia-mutated (ATM) and Ataxia telangiectasia and Rad3-related (ATR) PI3-kinases in phosphorylation of the HBV core protein (HBc). We determined that treatment of HBc-expressing hepatocytes with genotoxic agents, e.g., etoposide or hydrogen peroxide, activated the host ATM-Chk2 pathway, as determined by increased phosphorylation of ATM at Ser1981 and Chk2 at Thr68. The activation of ATM led, in turn, to increased phosphorylation of cytoplasmic HBc at serine-glutamine (SQ) motifs located in its C-terminal domain. Conversely, down-regulation of ATM using ATM-specific siRNAs or inhibitor effectively reduced etoposide-induced HBc phosphorylation. Detailed mutation analysis of S-to-A HBc mutants revealed that S170 (S168 in a 183-aa HBc variant) is the primary site targeted by ATM-regulated phosphorylation. Interestingly, mutation of two major phosphorylation sites involving serines at positions 157 and 164 (S155 and S162 in a 183-aa HBc variant) resulted in decreased etoposide-induced phosphorylation, suggesting that the priming phosphorylation at these serine-proline (SP) sites is vital for efficient phosphorylation of SQ motifs. Notably, the mutation of S172 (S170 in a 183-aa HBc variant) had the opposite effect and resulted in massively up-regulated phosphorylation of HBc, particularly at S170. Etoposide treatment of HBV infected HepG2-NTCP cells led to increased levels of secreted HBe antigen and intracellular HBc protein. Together, our studies identified HBc as a substrate for ATM-mediated phosphorylation and mapped the phosphorylation sites. The increased expression of HBc and HBe antigens in response to genotoxic stress supports the idea that the ATM pathway may provide growth advantage to the replicating virus.

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.

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.

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 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 A Diagnostic Laboratory-Based Study on Frequency and Distribution of Viral Hepatitis B and C Among Sudanese

2017 ◽  
Vol 11 (1) ◽  
pp. 98-107 ◽  
Author(s):  
Marwan M. Badawi ◽  
Alshaimaa A. Mohammed ◽  
Mohammed S. Mohammed ◽  
Mohammed M. Saeed ◽  
Elmoez Y. Ali ◽  
...  
Keyword(s):  
Hepatitis B ◽  
Public Health Problem ◽  
Epidemiological Data ◽  
Age Group ◽  
Diagnostic Laboratory ◽  
Genotype 4 ◽  
Care Givers ◽  
Time Period ◽  
Threatening Condition ◽  
Life Threatening

Background: Hepatitis B infection is an alarming public health problem. Almost two billion people of the population alive today, would have been infected at some time in their lives by hepatitis B. Hepatitis C virus is another life threatening condition, and about 425,000 deaths occur each year due to its complications. The current study was carried out to provide care givers and health planners basic epidemiological data regarding the frequency and distribution of HBV and HCV based on age and sex during a time period of more than 5 years. Result: A total of 2109 different patients were found to be infected by HBV during the study period; 1641 (77.81%) were males and 468 (22.19%) were females with the age group of 20-39 years predominating (64%). In addition,16% of patients tested for HBeAg were found reactive. Conclusion: There were significant correlations observed between the levels of HBV DNA and ALT, AST and AFP. Regarding HCV, 70 males (54.9%) and 63 females (45.1%) were found to be infected, with preponderance of the age group 41 - 60 years and the genotype 4. Designing knowledge raising campaigns is appreciated as well as repetition of similar studies among larger populations in the following few years will help track a way to improvement.

scholarly journals Roles of the Three Major Phosphorylation Sites of Hepatitis B Virus Core Protein in Viral Replication

Virology ◽  
1999 ◽  
Vol 259 (2) ◽  
pp. 342-348 ◽  
Author(s):  
Yueh T. Lan ◽  
Jie Li ◽  
Wen-yeh Liao ◽  
Jing-hsiung Ou
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Viral Replication ◽  
Core Protein ◽  
Phosphorylation Sites ◽  
Virus Core ◽  
B Virus

scholarly journals Involvement of Interleukin 6 in Hepatitis B Viral Infection

2015 ◽  
Vol 37 (2) ◽  
pp. 677-686 ◽  
Author(s):  
Caixia Xia ◽  
Yanning Liu ◽  
Zhi Chen ◽  
Min Zheng
Keyword(s):  
Hepatitis B ◽  
Interleukin 6 ◽  
Inflammatory Diseases ◽  
Infection Process ◽  
Hbv Replication ◽  
B Virus ◽  
Life Threatening ◽  
Hepatitis B Viral Infection ◽  
Global Health Problem

Hepatitis B is a major global health problem and a potentially life-threatening liver infection caused by hepatitis B virus (HBV). Many cytokines including interleukin 6 (IL-6) have been shown to be involved in the HBV infection process. IL-6 is a typical cytokine made up of 184 amino acids, and the gene is located in chromosome 7p21. For healthy people, serum IL-6 levels are usually too low to be detected. However, dysregulated synthesis of IL-6 has been discovered in chronic inflammatory diseases such as hepatitis B, Crohn's disease and rheumatoid arthritis. IL-6 also plays an important role in HBV replication and in the development of hepatitis B disease. This review aims to present the latest discoveries concerning the role of IL-6 in hepatitis B disease progression, and HBV entry and replication, and evaluate polymorphisms that are associated with the development of hepatitis B disease.

scholarly journals Hepatitis B Virus Nucleocapsids Formed by Carboxy-Terminally Mutated Core Proteins Contain Spliced Viral Genomes but Lack Full-Size DNA

2004 ◽  
Vol 78 (24) ◽  
pp. 13812-13818 ◽  
Author(s):  
Josef Köck ◽  
Michael Nassal ◽  
Karl Deres ◽  
Hubert E. Blum ◽  
Fritz von Weizsäcker
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Viral Replication ◽  
Core Protein ◽  
Serine Phosphorylation ◽  
Phosphorylation Sites ◽  
Nucleic Acid Binding ◽  
Core Proteins ◽  
B Virus ◽  
Arginine Residues

ABSTRACT The carboxy-terminal sequence of the hepatitis B virus (HBV) core protein constitutes a nucleic acid binding domain that is rich in arginine residues and contains three serine phosphorylation sites. While dispensable for capsid assembly, this domain is involved in viral replication, as demonstrated by the effects of mutations on RNA packaging and/or reverse transcription; however, the underlying mechanisms are poorly understood. Here we tested a series of core protein mutants in which the three serine phosphorylation sites were replaced by glutamic acid, in parallel with a previously described deletion variant lacking the 19 C-terminal amino acid residues, for their ability to support viral replication in transfected hepatoma cells. Replacement of all serines and the deletion gave rise to nucleocapsids containing a smaller than wild-type DNA genome. Rather than a single-stranded DNA intermediate, as previously thought, this was a 2.0-kbp double-stranded DNA molecule derived from spliced pregenomic RNA (pgRNA). Interestingly, full-length pgRNA was associated with nucleocapsids but was found to be sensitive to nuclease digestion, while encapsidated spliced RNA and 3′ truncated RNA species were nuclease resistant. These findings suggest that HBV pgRNA encapsidation is directional and that a packaging limit is determined by the C-terminal portion of the core protein.

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