630 HEPATITIS B VIRUS X PROTEIN AUGMENTS HBV TRANSCRIPTION AND REPLICATION IN VIVO OF MOUSE

ABSTRACT Chronic infection with hepatitis B virus (HBV) is one of the major etiological factors in the development of human hepatocellular carcinoma. Transgenic mice that express the HBV X protein (HBx) have previously been shown to be more sensitive to the effects of hepatocarcinogens, although the mechanism for this cofactor role remains unknown. The ability of HBx to inhibit DNA repair in transiently transfected cell lines suggests one possible pathway. In the present study, primary hepatocytes isolated from transgenic mice that possess the HBV X gene under the control of the human α-1-antitrypsin regulatory region (ATX mice) were found to be deficient in their ability to conduct unscheduled DNA synthesis in response to UV-induced DNA damage. In order to measure the impact of HBx expression on DNA repair in vivo, double-transgenic mice that express HBx and possess a bacteriophage lambda transgene were sacrificed at 30, 90, and 240 days of age. Mutation frequency was determined for high-molecular-weight liver DNA of ATX and control mice by functional analysis of the lambda transgene. Expression of HBx did not significantly increase the accumulation of spontaneous mutations. These results are consistent with previous studies of HBx transgenic mice in which no effect of HBx on liver histology was apparent. This new animal model provides a powerful system in which to investigate the in vivo cooperation between HBx expression and environmental carcinogens.

Download Full-text

RPB5-Mediating Protein Suppresses Hepatitis B Virus (HBV) Transcription and Replication by Counteracting the Transcriptional Activation of Hepatitis B virus X Protein in HBV Replication Mouse Model

Jundishapur Journal of Microbiology ◽

10.5812/jjm.21936 ◽

2015 ◽

Vol 8 (9) ◽

Cited By ~ 3

Author(s):

Qiaoling Zhou ◽

Feijun Huang ◽

Lanlan Chen ◽

Enqiang Chen ◽

Lang Bai ◽

...

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Mouse Model ◽

Transcriptional Activation ◽

X Protein ◽

Hbv Replication ◽

B Virus ◽

Transcription And Replication

Download Full-text

Hepatitis B Virus X Gene Differentially Modulates Subgenotype F1b and F4 Replication

Viruses ◽

10.3390/v11070655 ◽

2019 ◽

Vol 11 (7) ◽

pp. 655

Author(s):

María Mercedes Elizalde ◽

Micaela Speroni ◽

Rodolfo Héctor Campos ◽

Diego Martín Flichman

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Regulatory Protein ◽

Regulatory Elements ◽

Wild Type ◽

X Protein ◽

B Virus ◽

Common Purpose ◽

X Gene ◽

Transcription And Replication

Hepatitis B virus (HBV) is classified into ten genotypes and numerous subgenotypes (sgt). In particular, sgt F1b and sgt F4, native of Latin America, have been associated with differences in clinical and virological characteristics. Hepatitis B virus X protein (HBx) is a multifunctional regulatory protein associated with the modulation of viral transcription and replication. In this work, we analyzed the role of the X gene and the encoded X protein in sgtF1b and sgtF4 replication. Transfection with HBx deficient genomes revealed remarkable differences in the replicative capacity of sgtF1b and sgtF4 mutants. The silencing of HBx increased sgtF1b X(-) transcription and replication by more than 2.5 fold compared to the wild type variant, while it decreased sgtF4 X(-) transcription and replication by more than 3 fold. Trans-complementation of HBx restore sgtF1b and sgtF4 wild type transcription and replication levels. In addition, transfection with chimeric variants, carrying wild type (F1b/XF4 and F4/XF1b) or mutated (F1b/X(-)F4 and F4/X(-)F1b) X gene of one sgt in the backbone of the other sgt, showed that the nucleotide sequence of the X gene, that includes regulatory elements that modulate pgRNA transcription, was responsible for the disparity observed between sgtF1b X(-) and sgtF4 X(-). These results showed that sgtF1b and sgtF4 X gene play a central role in regulating HBV transcription and replication, which eventually lead to a common purpose, to reach wild type replication levels of sgtF1b and sgtF4 viruses.

Download Full-text

In Vivo Regulation of Hepatitis B Virus Replication by Peroxisome Proliferators

Journal of Virology ◽

10.1128/jvi.73.12.10377-10386.1999 ◽

1999 ◽

Vol 73 (12) ◽

pp. 10377-10386 ◽

Cited By ~ 35

Author(s):

Luca G. Guidotti ◽

Carrie M. Eggers ◽

Anneke K. Raney ◽

Susan Y. Chi ◽

Jeffrey M. Peters ◽

...

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Transgenic Mice ◽

Fold Increase ◽

Nuclear Hormone Receptor ◽

Peroxisome Proliferators ◽

B Virus ◽

Replication Intermediates ◽

Transcription And Replication

ABSTRACT The role of the peroxisome proliferator-activated receptor α (PPARα) in regulating hepatitis B virus (HBV) transcription and replication in vivo was investigated in an HBV transgenic mouse model. Treatment of HBV transgenic mice with the peroxisome proliferators Wy-14,643 and clofibric acid resulted in a less than twofold increase in HBV transcription rates and steady-state levels of HBV RNAs in the livers of these mice. In male mice, this increase in transcription was associated with a 2- to 3-fold increase in replication intermediates, whereas in female mice it was associated with a 7- to 14-fold increase in replication intermediates. The observed increases in transcription and replication were dependent on PPARα. HBV transgenic mice lacking this nuclear hormone receptor showed similar levels of HBV transcripts and replication intermediates as untreated HBV transgenic mice expressing PPARα but failed to demonstrate alterations in either RNA or DNA synthesis in response to peroxisome proliferators. Therefore, it appears that very modest alterations in transcription can, under certain circumstances, result in relatively large increases in HBV replication in HBV transgenic mice.

Download Full-text

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.

Download Full-text

Altered DNA Mutation Spectrum in Aflatoxin B1-Treated Transgenic Mice That Express the Hepatitis B Virus X Protein

Journal of Virology ◽

10.1128/jvi.76.22.11770-11774.2002 ◽

2002 ◽

Vol 76 (22) ◽

pp. 11770-11774 ◽

Cited By ~ 27

Author(s):

Charles R. Madden ◽

Milton J. Finegold ◽

Betty L. Slagle

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Transgenic Mice ◽

Aflatoxin B1 ◽

Environmental Carcinogens ◽

X Protein ◽

Dna Mutation ◽

Dna Mutations ◽

B Virus

ABSTRACT Humans chronically infected with hepatitis B virus (HBV) are at further risk of liver cancer upon exposure to dietary aflatoxin B1 (AFB1), a carcinogenic product of the mold Aspergillus flavus. For the present study, we utilized double-transgenic mice (ATX mice) that express the HBV X protein (HBx) and possess a bacteriophage lambda transgene to evaluate the in vivo effect of HBx expression on AFB1-induced DNA mutations. The expression of HBx correlated with a 24% increase in mutation frequency overall and an approximately twofold increase in the incidence of G/C-to-T/A transversion mutations following AFB1 exposure. These results are consistent with a model in which expression of HBx during chronic HBV infection may contribute to the development of hepatocellular carcinoma following exposure to environmental carcinogens.

Download Full-text

Paracrine in vivo inhibitory effects of hepatitis B virus X protein (HBx) on liver cell proliferation: An alternative mechanism of HBx-related pathogenesis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.092657699 ◽

2002 ◽

Vol 99 (10) ◽

pp. 6991-6996 ◽

Cited By ~ 50

Author(s):

J. G. Tralhao ◽

J. Roudier ◽

S. Morosan ◽

C. Giannini ◽

H. Tu ◽

...

Keyword(s):

Cell Proliferation ◽

Hepatitis B Virus ◽

Hepatitis B ◽

Liver Cell ◽

Alternative Mechanism ◽

Inhibitory Effects ◽

X Protein ◽

B Virus

Download Full-text

Sustained Activation of Mitogen-Activated Protein Kinases and Activator Protein 1 by the Hepatitis B Virus X Protein in Mouse Hepatocytes In Vivo

Journal of Virology ◽

10.1128/jvi.75.21.10348-10358.2001 ◽

2001 ◽

Vol 75 (21) ◽

pp. 10348-10358 ◽

Cited By ~ 61

Author(s):

Ruchika Nijhara ◽

Siddhartha S. Jana ◽

Shyamal K. Goswami ◽

Ajay Rana ◽

Subeer S. Majumdar ◽

...

Keyword(s):

Hepatitis B Virus ◽

Hepatitis B ◽

Dependent Manner ◽

Activator Protein 1 ◽

X Protein ◽

Activator Protein ◽

B Virus ◽

Mitogen Activated Protein ◽

Sustained Activation

ABSTRACT Transcriptional activation of diverse cellular genes by the X protein (HBx) of hepatitis B virus (HBV) has been suggested as one of the mechanisms for HBV-associated hepatocellular carcinoma. However, such functions of HBx have been studied using transformed cells in culture and have not been examined in the normal adult hepatocytes, a natural host of HBV. Using an efficient hepatocyte-specific virus-based gene delivery system developed in our laboratory earlier, we studied the HBx action in vivo. We demonstrate that following virosome-mediated delivery of HBx DNA, a large population (>50%) of hepatocytes express the HBx protein in a dose-dependent manner, which induces a significant increase in the activity of extracellular signal-regulated kinases (ERKs) in the livers of HBx-transfected mice. Inhibition of HBx-induced ERK activation following intravenous administration of PD98059, a mitogen-activated protein kinase kinase kinase (MEK) inhibitor, confirmed the requirement for MEK in the activation of ERKs by HBx. Induction of ERK activity by HBx was sustained for up to 30 days. Interestingly, sustained activation of c-Jun N-terminal kinases (JNKs) for up to 30 days was also noted. Such constitutive ERK and JNK activation as a consequence of continued HBx expression also led to sustained stimulation of further downstream events, such as increased levels of c-Jun and c-Fos proteins along with the persistent induction of activator protein 1 binding activity. Taken together, our data suggest a critical role of these molecules in HBx-mediated cell transformation.

Download Full-text