The Binding of Hepatitis B Virus X Protein to Glioma-Associated Oncogene Homologue 1 and its Biological Characterization In vitro

Background/Aims: Hepatitis B virus (HBV)-associated glomerulonephritis (HBV-GN) is characterized by a reduced number of podocytes due to apoptosis and shedding from the basement membrane. However, the pathological mechanism of HBV-GN is unclear. We previously showed that hepatitis B virus X protein (HBx) promotes apoptosis in tubular epithelial cells. In this study, we transfected podocytes with HBx and examined the effects on adhesion and apoptosis of these cells. Methods: Podocytes were transfected with pc-DNA3.1 (+)-HBx. One control group was not transfected and another control group was transfected with empty plasmids. Podocyte adhesion was assessed by a fluorescence assay, apoptosis was measured by flow cytometry and fluorescence microscopy, and expression of α3β1 integrin was determined by western blotting and the reverse transcription polymerase chain reaction (RT-PCR). Activity of caspase-8 was measured by a spectrophotometric assay. Results: Relative to controls, podocytes with pc-DNA3.1(+)-HBx had reduced cell adhesion, increased apoptosis, reduced expression of α3β1 integrin, and increased caspase-8 activity. β1 integrin blockage reduced podocyte adhesion, but increased apoptosis and caspase-8 activity. Treatment of transfected podocytes with a caspase-8 inhibitor (Z-IETD-FMK) had no effect on the HBx-mediated integrin downregulation and reduced podocyte adhesion, suggesting that α3β1 integrin downregulaton is sufficient to alter cell adhesion. Conclusions: Our in vitro results indicate that HBx reduced podocyte adhesion and expression of α3β1 integrin, and increased apoptosis. Moreover, HBx-mediated downregulation of α3β1 integrin expression is sufficient to reduce podocyte adhesion. HBx-induced apoptosis of podocytes may contribute to HBV-GN.

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Anti-oncogene PTPN13 inactivation by hepatitis B virus X protein counteracts IGF2BP1 to promote hepatocellular carcinoma progression

Oncogene ◽

10.1038/s41388-020-01498-3 ◽

2020 ◽

Vol 40 (1) ◽

pp. 28-45 ◽

Cited By ~ 1

Author(s):

Yongcong Yan ◽

Pinbo Huang ◽

Kai Mao ◽

Chuanchao He ◽

Qiaodong Xu ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Hepatitis B Virus ◽

Hepatitis B ◽

Tyrosine Phosphatase ◽

Cellular Protein ◽

Metabolic Reprogramming ◽

X Protein ◽

B Virus

AbstractHepatitis B x protein (HBx) affects cellular protein expression and participates in the tumorigenesis and progression of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). Metabolic reprogramming contributed to the HCC development, but its role in HBV-related HCC remains largely unclear. Tyrosine-protein phosphatase nonreceptor type 13 (PTPN13) is a significant regulator in tumor development, however, its specific role in hepatocarcinogenesis remains to be explored. Here, we found that decreased PTPN13 expression was associated with HBV/HBx. Patients with low PTPN13 expression showed a poor prognosis. Functional assays revealed that PTPN13 inhibited proliferation and tumorigenesis in vitro and in vivo. Further mechanistic studies indicated that HBx inhibited PTPN13 expression by upregulating the expression of DNMT3A and interacting with DNMT3A. Furthermore, we found that DNMT3A bound to the PTPN13 promoter (−343 to −313 bp) in an epigenetically controlled manner associated with elevated DNA methylation and then inhibited PTPN13 transcription. In addition, we identified IGF2BP1 as a novel PTPN13-interacting gene and demonstrated that PTPN13 influences c-Myc expression by directly and competitively binding to IGF2BP1 to decrease the intracellular concentration of functional IGF2BP1. Overexpressing PTPN13 promoted c-Myc mRNA degradation independent of the protein tyrosine phosphatase (PTP) activity of PTPN13. Importantly, we discovered that the PTPN13-IGF2BP1-c-Myc axis was important for cancer cell growth through promoting metabolic reprogramming. We verified the significant negative correlations between PTPN13 expression and c-Myc, PSPH, and SLC7A1 expression in clinical HCC tissue samples. In summary, our findings demonstrate that PTPN13 is a novel regulator of HBV-related hepatocarcinogenesis and may play an important role in HCC. PTPN13 may serve as a prognostic marker and therapeutic target in HBV-related HCC patients.

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Polo-like kinase 1 inhibition suppresses hepatitis B virus X protein-induced transformation in an in vitro model of liver cancer progression

Hepatology ◽

10.1002/hep.22996 ◽

2009 ◽

Vol 50 (2) ◽

pp. 414-423 ◽

Cited By ~ 29

Author(s):

Leo L. Studach ◽

Lova Rakotomalala ◽

Wen-Horng Wang ◽

Ronald L. Hullinger ◽

Stefano Cairo ◽

...

Keyword(s):

Hepatitis B Virus ◽

Liver Cancer ◽

Hepatitis B ◽

Cancer Progression ◽

In Vitro Model ◽

X Protein ◽

B Virus ◽

Vitro Model

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Stimulation of Cellular Proliferation by Hepatitis B Virus X Protein

Disease Markers ◽

10.1155/2001/571254 ◽

2001 ◽

Vol 17 (3) ◽

pp. 153-157 ◽

Cited By ~ 47

Author(s):

Charles R. Madden ◽

Betty L. Slagle

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Cellular Proliferation ◽

X Protein ◽

Hepatitis Viruses ◽

B Virus ◽

Infected Cells ◽

Proliferation In Vitro

Chronic infection with the hepatitis B virus (HBV) is a known risk factor in the development of human hepatocellular carcinoma (HCC). The HBV-encoded X protein, HBx, has been investigated for properties that may explain its cancer cofactor role in transgenic mouse lines. We discuss here recent data showing that HBx is able to induce hepatocellular proliferation in vitro and in vivo. This property of HBx is predicted to sensitize hepatocytes to other HCC cofactors, including exposure to carcinogens and to other hepatitis viruses. Cellular proliferation is intimately linked to the mechanism(s) by which most tumor-associated viruses transform virus-infected cells. The HBx alteration of the cell cycle provides an additional mechanism by which chronic HBV infection may contribute to HCC.

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49 HEPATITIS B VIRUS X PROTEIN INDUCED MODULATION IN THE EXPRESSION OF MIR-222 IN MALIGNANT HEPATOCYTES IN VITRO

Journal of Clinical and Experimental Hepatology ◽

10.1016/s0973-6883(12)60050-4 ◽

2012 ◽

Vol 2 (1) ◽

pp. S28

Author(s):

M Bandopadhyay ◽

A Banarjee ◽

R Panigrahi ◽

N Sarkar ◽

A Biswas ◽

...

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

X Protein ◽

B Virus

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Hepatitis B virus X protein promotes proliferation of hepatocellular carcinoma cells by upregulating miR-181b by targeting ING5

Biological Chemistry ◽

10.1515/hsz-2018-0178 ◽

2018 ◽

Vol 399 (6) ◽

pp. 611-619 ◽

Cited By ~ 2

Author(s):

Xuhua Xie ◽

Xiaopei Xu ◽

Changyu Sun ◽

Zujiang Yu

Keyword(s):

Hepatocellular Carcinoma ◽

Hepatitis B Virus ◽

Hepatitis B ◽

Cell Lines ◽

Tumor Model ◽

Luciferase Reporter ◽

X Protein ◽

B Virus

Abstract Hepatitis B virus X protein (HBx) played a key role in the development of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). Emerging evidence has demonstrated that miR-181b and the inhibitor of growth protein 5 (ING5) participated in the pathophysiological process. However, the regulatory mechanism of HBx remained unknown. The expression of miR-181b and ING5 in HCC tissues and cell lines were examined using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting. Cell viability was determined using the MTT method following HCC cell lines transfection. The interaction between miR-181b and ING5 was assessed by luciferase reporter assay. The nude mice tumor model was well established to evaluate the role and biological functions of HBx on the progression of HBV-related HCC in vivo. MiR-181b was upregulated and ING5 was downregulated in HCC tissues and cell lines. As suggested by the results from in vitro and in vivo experiments, HBx downregulates the expression of the miR-181b target gene ING5, resulting in the promotion of HCC cell proliferation. HBx accelerates proliferation activity of HCC cells by increasing miR-181b expression via targeting ING5, thereby influencing the progression of HBV-related HCC.

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Different Regions of Hepatitis B Virus X Protein Are Required for Enhancement of bZip-Mediated Transactivation versus Transrepression

Journal of Virology ◽

10.1128/jvi.74.1.83-90.2000 ◽

2000 ◽

Vol 74 (1) ◽

pp. 83-90 ◽

Cited By ~ 27

Author(s):

Sangeeta Barnabas ◽

Ourania M. Andrisani

Keyword(s):

Amino Acid ◽

Hepatitis B Virus ◽

Hepatitis B ◽

Deletion Mutants ◽

Amino Acid Residues ◽

X Protein ◽

Amino Acid Region ◽

B Virus

ABSTRACT The hepatitis B virus X protein (pX) interacts directly with the bZip transactivator CREB and the bZip repressors ICERIIγ and ATF3, increasing their DNA-binding affinity in vitro and their transcriptional efficacy in vivo. However, the mechanism of bZip-pX interaction and of the pX-mediated increase in the bZip transcriptional efficacy remains to be understood. In this study with deletion mutants of pX, we delineated a 67-amino-acid region spanning residues 49 to 115 required for direct CREB, ATF3, and ICER IIγ interaction in vitro and in vivo and increased bZip/CRE binding in vitro. Transient transfections of the pX deletion mutants in AML12 hepatocytes demonstrate that pX49–115 is as effective as the full-length pX in enhancing the ATF3- and ICERIIγ-mediated transrepression. However, this pX region is inactive in increasing the transactivation efficacy of CREB; additional amino acid residues present in pX49–140are required to mediate the increased transactivation efficacy of CREB in vivo. This requirement for different regions of pX in affecting CREB transactivation suggests that amino acid residues 115 to 140 integrate additional events in effecting pX-mediated transactivation, such as concomitant interactions with select components of the basal transcriptional apparatus.

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Hepatitis B Virus X Protein Modulates Chemokine CCL15 Upregulation in Hepatocellular Carcinoma

Anti-Cancer Agents in Medicinal Chemistry ◽

10.2174/1871520621666210302083407 ◽

2021 ◽

Vol 21 ◽

Author(s):

Ying Li ◽

Chaomin Wang ◽

Ting Zhao ◽

Ranliang Cui ◽

Linfei Hu ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Hepatitis B Virus ◽

Hepatitis B ◽

X Protein ◽

Tissue Samples ◽

B Virus ◽

Mrna And Protein Expression ◽

Progression Factor ◽

Liver Tissues

Background: Hepatitis B virus X protein (HBx) is an indispensable progression factor in hepatocellular carcinoma (HCC). CCL15 could be a peculiar proteomic biomarker of HCC with tumorigenesis and tumor invasion. Objective: The aim of study was to explore the relationship between HBx and CCL15 expression in HCC. Methods: HBV–positive HCC pathological tissue samples and corresponding adjacent non-tumor liver tissues were clearly collected. The expression of HBx and CCL15 was analyzed by immunohistochemistry, real-time polymerase chain reaction (PCR) and western blot analysis in tissues or in vitro. Results: The levels of CCL15 mRNA and protein expression in HCC samples were observably higher than the ones of adjacent non-tumor liver tissues. The CCL15 was significantly associated with the expression of HBx in HBV-positive HCC samples. The up-regulation of HBx induced CCL15 expression in vitro. The high expression score of CCL15 was significant associated with the poor prognosis of HCC patients. Conclusions: The CCL15 expression was observably associated with HBx in HCC patients. The CCL15 may be considered as a indicator in clinical managment of HBV-associated HCC.

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Hepatitis B virus X protein stimulates cell growth by downregulating p16 levels via PA28γ-mediated proteasomal degradation

Journal of General Virology ◽

10.1099/jgv.0.001461 ◽

2020 ◽

Vol 101 (9) ◽

pp. 963-971

Author(s):

Sungkyung Cha ◽

Kyung Lib Jang

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Cell Cycle Progression ◽

Critical Role ◽

Proteasomal Degradation ◽

X Protein ◽

Cycle Progression ◽

B Virus

Proteasomal activator 28 gamma (PA28γ), an essential constituent of the 20S proteasome responsible for ubiquitin-independent degradation of target proteins, is frequently overexpressed in hepatocellular carcinoma. Recently, we have reported that hepatitis B virus (HBV) X protein (HBx) activates PA28γ expression in human hepatocytes via upregulation of p53 levels; however, its role in HBV tumorigenesis remains unknown. Here, we found that HBx-activated PA28γ downregulates p16 levels via ubiquitin-independent proteasomal degradation. As a result, HBx activated the Rb-E2F pathway and stimulated G1/S cell cycle progression, resulting in an increase in cell proliferation. The potential of HBx to induce these effects was reproduced in a 1.2-mer HBV replicon and in in vitro HBV infection systems and was almost completely abolished by either PA28γ knockdown or p16 overexpression, demonstrating the critical role of the PA28γ-mediated p16 degradation in HBV tumorigenesis.

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