Browsing by Author "Liu, Shi"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    NEDD4 family ubiquitin ligase AIP4 interacts with Alix to enable HBV naked capsid egress in an Alix ubiquitination-independent manner
    (Public Library of Science, 2024-09-11) Shen, Sheng; Cai, Dawei; Liang, Hongyan; Zeng, Ge; Liu, Wendong; Yan, Ran; Yu, Xiaoyang; Zhang, Hu; Liu, Shi; Li, Wanying; Deng, Rui; Lu, Xingyu; Liu, Yuanjie; Sun, Jian; Guo, Haitao; Microbiology and Immunology, School of Medicine
    Hepatitis B virus (HBV) exploits the endosomal sorting complexes required for transport (ESCRT)/multivesicular body (MVB) pathway for virion budding. In addition to enveloped virions, HBV-replicating cells nonlytically release non-enveloped (naked) capsids independent of the integral ESCRT machinery, but the exact secretory mechanism remains elusive. Here, we provide more detailed information about the existence and characteristics of naked capsid, as well as the viral and host regulations of naked capsid egress. HBV capsid/core protein has two highly conserved Lysine residues (K7/K96) that potentially undergo various types of posttranslational modifications for subsequent biological events. Mutagenesis study revealed that the K96 residue is critical for naked capsid egress, and the intracellular egress-competent capsids are associated with ubiquitinated host proteins. Consistent with a previous report, the ESCRT-III-binding protein Alix and its Bro1 domain are required for naked capsid secretion through binding to intracellular capsid, and we further found that the ubiquitinated Alix binds to wild type capsid but not K96R mutant. Moreover, screening of NEDD4 E3 ubiquitin ligase family members revealed that AIP4 stimulates the release of naked capsid, which relies on AIP4 protein integrity and E3 ligase activity. We further demonstrated that AIP4 interacts with Alix and promotes its ubiquitination, and AIP4 is essential for Alix-mediated naked capsid secretion. However, the Bro1 domain of Alix is non-ubiquitinated, indicating that Alix ubiquitination is not absolutely required for AIP4-induced naked capsid secretion. Taken together, our study sheds new light on the mechanism of HBV naked capsid egress in viral life cycle.
  • Thumbnail Image
    Item
    Rapid Turnover of Hepatitis B Virus Covalently Closed Circular DNA Indicated by Monitoring Emergence and Reversion of Signature-Mutation in Treated Chronic Hepatitis B Patients
    (Wiley, 2021) Huang, Qi; Zhou, Bin; Cai, Dawei; Zong, Yuhua; Wu, Yaobo; Liu, Shi; Mercier, Alexandre; Guo, Haitao; Hou, Jinlin; Colonno, Richard; Sun, Jian; Microbiology and Immunology, School of Medicine
    Background and aims: Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) plays a pivotal role in the establishment and persistence of HBV infection. Understanding the turnover time of preexisting cccDNA pools would be helpful in designing strategies to clear HBV by fully blocking the de novo generation of cccDNA. Approach and results: In this study, we retrospectively monitored the emergence and reversion of the rtM204I/V mutant, a signature lamivudine resistance (LAMR ) mutation serving as a biomarker of cccDNA turnover in liver biopsies and longitudinal serum samples from two clinical trials. Methodologies were optimized to differentially isolate and sequence HBV virion DNA, cccDNA, and HBV RNA from clinical samples. A strong correlation was observed between LAMR composition of cccDNA with that of serum and intrahepatic HBV RNA in paired liver and serum samples (r = 0.96 and 0.90, respectively), suggesting that serum HBV RNA can serve as a surrogate marker of cccDNA genetic composition when liver biopsies are unavailable. LAMR mutations emerged and increased from undetectable to 40%-90% within 16-28 weeks in serum HBV RNA from telbivudine-treated patients experiencing virological breakthrough. Similarly, in lamivudine-resistant patients who switched to interferon therapy, serum HBV-RNA population bearing 100% LAMR mutations fully reversed back to wild type within 24-48 weeks. Conclusions: The genetic composition dynamics of serum HBV RNA and biopsy cccDNA in treated HBV patients indicates that cccDNA turnover occurs relatively rapidly (several months), offering a possibility of HBV cure with finite therapy through completely blocking cccDNA replenishment.
  • Thumbnail Image
    Item
    Serum HBV RNA: a New Potential Biomarker for Chronic Hepatitis B Virus Infection
    (AASLD, 2018) Liu, Shi; Zhou, Bin; Valdes, Juan D.; Sun, Jian; Guo, Haitao; Microbiology and Immunology, School of Medicine
    Chronic hepatitis B (CHB) is one of the major etiological causes of liver failure, cirrhosis, and hepatocellular carcinoma worldwide, and it cannot be completely cured by currently available drugs due to the persistent existence of hepatitis B virus (HBV) covalently closed circular DNA (cccDNA), the bona fide transcription template for HBV RNAs, in the infected hepatocytes. Since quantifying cccDNA per se requires an invasive procedure, serum biomarkers reflecting the intrahepatic cccDNA activity are warranted. Recently, a growing body of research suggests that the circulating HBV RNA may serve as a new serum biomarker for HBV infection, treatment and prognosis. In order to delineate the molecular and clinical characteristics of serum HBV RNA, we systematically reviewed the available literature on serum HBV RNA dating back to early 1990s. In this review, we will summarize the reported serum HBV RNA quantification methods and discuss the potential HBV RNA species in patient serum, and compare the reported correlations of serum HBV RNA with other serological markers, including HBV DNA, hepatitis B surface antigen (HBsAg), e antigen (HBeAg), and core‐related antigen (HBcrAg), as well as their correlations with the intrahepatic cccDNA, to assess its potential in clinical applications. The future directions for serum HBV RNA research will also be discussed.