scholarly journals Screening of the HBx transactivation domain interacting proteins and the function of interactor Pin1 in HBV replication

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Qiaoxia Zhou ◽  
Libo Yan ◽  
Baofu Xu ◽  
Xue’er Wang ◽  
Xuehong Sun ◽  
...  
Keyword(s):  
Hepg2 Cells ◽  
Functional Domain ◽  
Transactivation Domain ◽  
Glutathione S Transferase ◽  
Host Proteins ◽  
Hbv Replication ◽  
Pulldown Assay ◽  
Potential Association ◽  
B Virus

AbstractHepatitis B virus (HBV) X protein (HBx) has been determined to play a crucial role in the replication and transcription of HBV, and its biological functions mainly depend on the interaction with other host proteins. This study aims at screening the proteins that bind to the key functional domain of HBx by integrated proteomics. Proteins that specifically bind to the transactivation domain of HBx were selected by comparing interactors of full-length HBx and HBx-D5 truncation determined by glutathione-S-transferase (GST) pull-down assay combined with mass spectrometry (MS). The function of HBx interactor Pin1 in HBV replication was further investigated by in vitro experiments. In this study, a total of 189 proteins were identified from HepG2 cells that specifically bind to the transactivation domain of HBx by GST pull-down and subsequent MS. After gene ontology (GO) analysis, Pin1 was selected as the protein with the highest score in the largest cluster functioning in protein binding, and also classified into the cluster of proteins with the function of structural molecule activity, which is of great potential to be involved in HBV life cycle. The interaction between Pin1 and HBx has been further confirmed by Ni2+-NTA pulldown assay, co-immunoprecipitation, and immunofluorescence microscopy. HBsAg and HBeAg levels significantly decreased in Pin1 expression inhibited HepG2.2.15 cells. Besides, the inhibition of Pin1 expression in HepG2 cells impeded the restored replication of HBx-deficient HBV repaired by ectopic HBx expression. In conclusion, our study identified Pin1 as an interactor binds to the transactivation domain of HBx, and suggested the potential association between Pin1 and the function of HBx in HBV replication.

scholarly journals Use of the Hepatitis B Virus Recombinant Baculovirus-HepG2 System to Study the Effects of (−)-β-2′,3′-Dideoxy-3′-Thiacytidine on Replication of Hepatitis B Virus and Accumulation of Covalently Closed Circular DNA

1999 ◽  
Vol 43 (8) ◽  
pp. 2017-2026 ◽  
Author(s):  
William E. Delaney ◽  
Thomas G. Miller ◽  
Harriet C. Isom
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Hepg2 Cells ◽  
Hbv Dna ◽  
Model Systems ◽  
Extracellular Dna ◽  
Hbv Replication ◽  
B Virus ◽  
Replicative Intermediates

ABSTRACT (−)-β-2′,3′-Dideoxy-3′-thiacytidine (lamivudine [3TC]) is a nucleoside analog which effectively interferes with the replication of hepatitis B virus (HBV) DNA in vitro and in vivo. We have investigated the antiviral properties of 3TC in vitro in HepG2 cells infected with recombinant HBV baculovirus. Different types of information can be obtained with the HBV baculovirus-HepG2 system because (i) experiments can be carried out at various levels of HBV replication including levels significantly higher than those that can be obtained from conventional HBV-expressing cell lines, (ii) cultures can be manipulated and/or treated prior to or during the initiation of HBV expression, and (iii) high levels of HBV replication allow the rapid detection of HBV products including covalently closed circular (CCC) HBV DNA from low numbers of HepG2 cells. The treatment of HBV baculovirus-infected HepG2 cells with 3TC resulted in an inhibition of HBV replication, evidenced by reductions in the levels of both extracellular HBV DNA and intracellular replicative intermediates. The effect of 3TC on HBV replication was both dose and time dependent, and the reductions in extracellular HBV DNA that we observed agreed well with the previously reported efficacy of 3TC in vitro. As expected, levels of HBV transcripts and extracellular hepatitis B surface antigen and e antigen were not affected by 3TC. Importantly, the HBV baculovirus-HepG2 system made it possible to observe for the first time that CCC HBV DNA levels are lower in cells treated with 3TC than in control cells. We also observed that the treatment of HepG2 cells prior to HBV baculovirus infection resulted in a slight increase in the efficacy of 3TC compared to treatments starting 24 h postinfection. The treatment of HepG2 cells with the highest concentration of 3TC tested in this study (2 μM) prior to the initiation of HBV replication markedly inhibited the accumulation of CCC DNA, whereas treatment with the same concentration of 3TC at a time when CCC HBV DNA pools were established within the cells was considerably less effective. In addition, our results suggest that in HepG2 cells, non-protein-associated relaxed circular HBV DNA and particularly CCC HBV DNA are considerably more resistant to 3TC treatment than other forms of HBV DNA, including replicative intermediates and extracellular DNA. We conclude from these studies that the HBV baculovirus-HepG2 system has specific advantages for drug studies and can be used to complement other in vitro model systems currently used for testing antiviral compounds.

scholarly journals Phosphorothioate Di- and Trinucleotides as a Novel Class of Anti-Hepatitis B Virus Agents

2004 ◽  
Vol 48 (6) ◽  
pp. 2199-2205 ◽  
Author(s):  
Radhakrishnan P. Iyer ◽  
Yi Jin ◽  
Arlene Roland ◽  
John D. Morrey ◽  
Samir Mounir ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Nucleoside Analogs ◽  
Hbv Dna ◽  
Parallel Synthesis ◽  
Hbv Replication ◽  
Long Term Treatment ◽  
B Virus ◽  
Dna Strand

ABSTRACT Several nucleoside analogs are under clinical development for use against hepatitis B virus (HBV). Lamivudine (3TC), a nucleoside analog, and adefovir dipivoxil (ADV), an acyclonucleotide analog, are clinically approved. However, long-term treatment can induce viral resistance, and following the cessation of therapy, viral rebound is frequently observed. There continues to be a need for new antiviral agents with novel mechanisms of action. A library of more than 600 di- and trinucleotide compounds synthesized by parallel synthesis using a combinatorial strategy was screened for potential inhibitors of HBV replication using the chronically HBV-producing cell line 2.2.15. Through an iterative process of synthesis, lead optimization, and screening, three analogs were identified as potent inhibitors of HBV replication: dinucleotides ORI-7246 (drug concentration at which a 10-fold reduction of HBV DNA was observed [EC90], 1.4 μM) and ORI-9020 (EC90, 1.2 μM) and trinucleotide ORI-7170 (EC90, 7.2 μM). These analogs inhibited the replication of both strands of HBV DNA. No suppression of HBV protein synthesis or intracellular core particle formation by these analogs was observed. No inhibition of HBV DNA strand elongation by the analogs or their 5′-triphosphate versions was apparent in in vitro polymerase assays. Although the exact mechanism of action is not yet identified, present data are consistent with an inhibition of the HBV reverse transcriptase-directed priming step prior to elongation of the first viral DNA strand. In transient-transfection assays, these analogs inhibited the replication of 3TC-resistant HBV. Synergistic interactions in combination treatments between the analogs and either 3TC or ADV were observed. These compounds represent a novel class of anti-HBV molecules and warrant further investigation as potential therapeutic agents.

scholarly journals Effects of point mutations in the cytidine deaminase domains of APOBEC3B on replication and hypermutation of hepatitis B virus in vitro

2007 ◽  
Vol 88 (12) ◽  
pp. 3270-3274 ◽  
Author(s):  
Marianne Bonvin ◽  
Jobst Greeve
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Point Mutations ◽  
Alternative Mechanism ◽  
Amino Terminal ◽  
Hbv Replication ◽  
B Virus ◽  
Carboxy Terminal ◽  
Deaminase Domain

APOBEC3 cytidine deaminases hypermutate hepatitis B virus (HBV) and inhibit its replication in vitro. Whether this inhibition is due to the generation of hypermutations or to an alternative mechanism is controversial. A series of APOBEC3B (A3B) point mutants was analysed in vitro for hypermutational activity on HBV DNA and for inhibitory effects on HBV replication. Point mutations inactivating the carboxy-terminal deaminase domain abolished the hypermutational activity and reduced the inhibitory activity on HBV replication to approximately 40 %. In contrast, the point mutation H66R, inactivating the amino-terminal deaminase domain, did not affect hypermutations, but reduced the inhibition activity to 63 %, whilst the mutant C97S had no effect in either assay. Thus, only the carboxy-terminal deaminase domain of A3B catalyses cytidine deaminations leading to HBV hypermutations, but induction of hypermutations is not sufficient for full inhibition of HBV replication, for which both domains of A3B must be intact.

Binding of nuclear factor EF-C to a functional domain of the hepatitis B virus enhancer region

1989 ◽  
Vol 9 (7) ◽  
pp. 2787-2797
Author(s):  
P Ostapchuk ◽  
G Scheirle ◽  
P Hearing
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Inverted Repeat ◽  
Functional Domain ◽  
Nuclear Factor ◽  
Transcriptional Enhancer ◽  
Base Pairs ◽  
Enhancer Region ◽  
B Virus

Nuclear factor EF-C is present in extracts prepared from human HepG2 liver cells and from other, nonliver cell lines and binds to the hepatitis B virus and polyomavirus transcriptional enhancer regions in vitro. An inverted repeat (5'-GTTGCNNNGCAAC-3') is located within both binding regions. Diethyl pyrocarbonate interference binding assays and competition binding experiments using altered binding sites demonstrated that EF-C contacts symmetrical nucleotides within the inverted repeat. Mutations that changed the length of the spacer region between the arms of the inverted repeat were introduced in the hepatitis enhancer region. Introduction of 1 or 2 base pairs between the repeats did not affect EF-C binding, but deletion of 1 base pair or introduction of 3 to 9 base pairs reduced binding dramatically. Introduction of 10 base pairs restored partial EF-C binding ability. These and other results suggest that EF-C binding is stabilized by dimerization. In vivo assays for enhancer function using these mutants demonstrated that the EF-C binding site is a functional and important component of the hepatitis B virus enhancer region.

scholarly journals Efficacies of Entecavir against Lamivudine-Resistant Hepatitis B Virus Replication and Recombinant Polymerases In Vitro

2002 ◽  
Vol 46 (8) ◽  
pp. 2525-2532 ◽  
Author(s):  
S. Levine ◽  
D. Hernandez ◽  
G. Yamanaka ◽  
S. Zhang ◽  
R. Rose ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Cross Resistance ◽  
Wild Type ◽  
Resistance Mutations ◽  
Hbv Replication ◽  
B Virus ◽  
Inhibition Studies

ABSTRACT Entecavir (ETV) is a potent and selective inhibitor of hepatitis B virus (HBV) replication in vitro and in vivo that is currently in clinical trials for the treatment of chronic HBV infections. A major limitation of the current HBV antiviral therapy, lamivudine (3TC), is the emergence of drug-resistant HBV in a majority of treated patients due to specific mutations in the nucleotide binding site of HBV DNA polymerase (HBV Pol). To determine the effects of 3TC resistance mutations on inhibition by ETV triphosphate (ETV-TP), a series of in vitro studies were performed. The inhibition of wild-type and 3TC-resistant HBV Pol by ETV-TP was measured using recombinant HBV nucleocapsids, and compared to that of 3TC-TP. These enzyme inhibition studies demonstrated that ETV-TP is a highly potent inhibitor of wild-type HBV Pol and is 100- to 300-fold more potent than 3TC-TP against 3TC-resistant HBV Pol. Cell culture assays were used to gauge the potential for antiviral cross-resistance of 3TC-resistant mutants to ETV. Results demonstrated that ETV inhibited the replication of 3TC-resistant HBV, but 20- to 30-fold higher concentrations were required. To gain further perspective regarding the potential therapeutic use of ETV, its phosphorylation was examined in hepatoma cells treated with extracellular concentrations representative of drug levels in plasma in ETV-treated patients. At these concentrations, intracellular ETV-TP accumulated to levels expected to inhibit the enzyme activity of both wild-type and 3TC-resistant HBV Pol. These findings are predictive of potent antiviral activity of ETV against both wild-type and 3TC-resistant HBV.

scholarly journals Role and Functional Domain of Hepatitis B Virus X Protein in Regulating HBV Transcription and Replication in Vitro and in Vivo

Viruses ◽  
2013 ◽  
Vol 5 (5) ◽  
pp. 1261-1271 ◽  
Author(s):  
Dao-Yin Gong ◽  
En-Qiang Chen ◽  
Fei-Jun Huang ◽  
Xiao-Hua Leng ◽  
Xing Cheng ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Functional Domain ◽  
X Protein ◽  
B Virus ◽  
Transcription And Replication

scholarly journals Cellular Pharmacology of the Anti-Hepatitis B Virus Agent β-l-2′,3′-Didehydro-2′,3′-Dideoxy-N4-Hydroxycytidine: Relevance for Activation in HepG2 Cells

2009 ◽  
Vol 54 (1) ◽  
pp. 341-345 ◽  
Author(s):  
E. Matthes ◽  
H. Bünger
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Half Life ◽  
Hepg2 Cells ◽  
Selective Inhibitor ◽  
Cellular Pharmacology ◽  
Hbv Replication ◽  
B Virus ◽  
Drug Free ◽  
Triphosphate Derivatives

ABSTRACT ß-l-2′,3′-Didehydro-2′,3′-dideoxy-N4-hydroxycytidine (l-Hyd4C) was demonstrated to be an effective and highly selective inhibitor of hepatitis B virus (HBV) replication in HepG2.2.15 cells (50% effective dose [ED50] = 0.03 μM; 50% cytotoxic dose [CD50] = 2,500 μM). In the present study, we investigated the intracellular pharmacology of tritiated l-Hyd4C in HepG2 cells. l-[3H]Hyd4C was shown to be phosphorylated extensively and rapidly to the 5′-mono-, 5′-di-, and 5′-triphosphate derivatives. Other metabolites deriving from a reduction or removal of the NHOH group of l-Hyd4C could not be detected, although both reactions were described as the primary catabolic pathways of the stereoisomer ß-d-N4-hydroxycytidine in HepG2 cells. Also, the formation of liponucleotide metabolites, such as the 5′-diphosphocholine derivative of l-Hyd4C, as described for some l-deoxycytidine analogues, seems to be unlikely. After incubation of HepG2 cells with 10 μM l-[3H]Hyd4C for 24 h, the 5′-triphosphate accumulated to 19.4 ± 2.7 pmol/106 cells. The predominant peak belonged to 5-diphosphate, with 43.5 ± 4.3 pmol/106 cells. The intracellular half-life of the 5′-triphosphate was estimated to be 29.7 h. This extended half-life probably reflects a generally low affinity of 5′-phosphorylated l-deoxycytidine derivatives for phosphate-degrading enzymes but may additionally be caused by an efficient rephosphorylation of the 5′-diphosphate during a drug-free incubation. The high 5′-triphosphate level and its extended half-life in HepG2 cells are consistent with the potent antiviral activity of l-Hyd4C.

scholarly journals In Vitro Characterization of the Anti-Hepatitis B Virus Activity and Cross-Resistance Profile of 2′,3′-Dideoxy-3′-Fluoroguanosine

2006 ◽  
Vol 50 (3) ◽  
pp. 955-961 ◽  
Author(s):  
A.-C. Jacquard ◽  
M.-N. Brunelle ◽  
C. Pichoud ◽  
D. Durantel ◽  
S. Carrouée-Durantel ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Antiviral Activity ◽  
Drug Resistant ◽  
Free System ◽  
Hbv Replication ◽  
Duck Hepatitis ◽  
Huh7 Cells ◽  
B Virus

ABSTRACT The fluorinated guanosine analog 2′,3′-dideoxy-3′-fluoroguanosine (FLG) was shown to inhibit wild-type (wt) hepatitis B virus (HBV) replication in a human hepatoma cell line permanently expressing HBV. Experiments performed in the duck model of HBV infection also showed its in vivo antiviral activity. In this study, we investigated the mechanism of inhibition of FLG on HBV replication and its profile of antiviral activity against different HBV or duck hepatitis B virus (DHBV) drug-resistant mutants. We found that FLG-triphosphate inhibits weakly the priming of the reverse transcription compared to adefovir-diphosphate in a cell-free system assay allowing the expression of an enzymatically active DHBV reverse transcriptase. It inhibits more potently wt DHBV minus-strand DNA synthesis compared to lamivudine-triphosphate and shows a similar activity compared to adefovir-diphosphate. FLG-triphosphate was most likely a competitive inhibitor of dGTP incorporation and a DNA chain terminator. In Huh7 cells transiently transfected with different HBV constructs, FLG inhibited similarly the replication of wt, lamivudine-resistant, adefovir-resistant, and lamivudine-plus-adefovir-resistant HBV mutants. These results were consistent with those obtained in the DHBV polymerase assay using the same drug-resistant polymerase mutants. In conclusion, our data provide new insights in the mechanism of action of FLG-triphosphate on HBV replication and demonstrate its inhibitory activity on drug-resistant mutant reverse transcriptases in vitro. Furthermore, our results provide the rationale for further clinical evaluation of FLG in the treatment of drug-resistant virus infection and in the setting of combination therapy to prevent or delay drug resistance.

scholarly journals Properties of Monoclonal Antibodies Directed against Hepatitis B Virus Polymerase Protein

1999 ◽  
Vol 73 (5) ◽  
pp. 4188-4196 ◽  
Author(s):  
Jasper zu Putlitz ◽  
Robert E. Lanford ◽  
Rolf I. Carlson ◽  
Lena Notvall ◽  
Suzanne M. de la Monte ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Insect Cells ◽  
Rnase H ◽  
Hbv Replication ◽  
B Virus ◽  
Multifunctional Enzymes ◽  
Infected Insect

ABSTRACT Hepadnavirus polymerases are multifunctional enzymes that play critical roles during the viral life cycle but have been difficult to study due to a lack of a well-defined panel of monoclonal antibodies (MAbs). We have used recombinant human hepatitis B virus (HBV) polymerase (Pol) expressed in and purified from baculovirus-infected insect cells to generate a panel of six MAbs directed against HBV Pol protein. Such MAbs were subsequently characterized with respect to their isotypes and functions in analytical and preparative assays. Using these MAbs as probes together with various deletion mutants of Pol expressed in insect cells, we mapped the B-cell epitopes of Pol recognized by these MAbs to amino acids (aa) 8 to 20 and 20 to 30 in the terminal protein (TP) region of Pol, to aa 225 to 250 in the spacer region, and to aa 800 to 832 in the RNase H domain. Confocal microscopy and immunocytochemical studies using various Pol-specific MAbs revealed that the protein itself appears to be exclusively localized to the cytoplasm. Finally, MAbs specific for the TP domain, but not MAbs specific for the spacer or RNase H regions of Pol, appeared to inhibit Pol function in the in vitro priming assay, suggesting that antibody-mediated interference with TP may now be assessed in the context of HBV replication.

Sign in / Sign up

Export Citation Format

Share Document