scholarly journals Induction of apoptosis after switch-on of the hepatitis B virus X gene mediated by the Cre/loxP recombination system

1999 ◽  
Vol 80 (12) ◽  
pp. 3257-3265 ◽  
Author(s):  
Yoshizumi Shintani ◽  
Hiroshi Yotsuyanagi ◽  
Kyoji Moriya ◽  
Hajime Fujie ◽  
Takeya Tsutsumi ◽  
...  

The HBx protein of hepatitis B virus is a multifunctional protein that is implicated in the pathogenesis of hepatocellular carcinoma by regulating gene transcription, causing cell proliferation and, as shown recently, inducing cell death. However, analysis of the effects of HBx in stable cultured cell clones has been hampered because only cell lines that adapted to the effects of HBx were selected during the establishment of cell clones. Here, we describe a system in which transcription of the X gene of hepatitis B virus is switched on by the use of the site-specific Cre recombinase. Two human liver cell lines, HLF and HepG2, were used, the former with a mutant p53 allele and the latter with wild-type p53. The stable cell clones isolated, which carried the X gene in a transcriptionally silent state, were infected with recombinant adenovirus carrying Cre recombinase. Ninety-six hours after adenovirus infection, cell clones that expressed HBx had undergone TUNEL-positive cell death with characteristics of apoptosis. Apoptosis was induced despite concomitant inactivation of the p53 protein as a result of its cytoplasmic translocation by HBx. In contrast, neither the X gene-carrying cells infected with wild-type adenovirus nor various control cells infected with Cre-expressing adenovirus exhibited apoptosis. These results indicate that the expression of HBx protein leads to liver cell apoptosis independently of the p53 pathway. The significance of HBx-induced apoptosis in natural infection is unclear, but it may contribute to the development of hepatitis and serve to spread progeny virus to neighbouring cells while evading the host immune responses.

1997 ◽  
Vol 94 (15) ◽  
pp. 8162-8167 ◽  
Author(s):  
P. Chirillo ◽  
S. Pagano ◽  
G. Natoli ◽  
P. L. Puri ◽  
V. L. Burgio ◽  
...  

Viruses ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 655
Author(s):  
María Mercedes Elizalde ◽  
Micaela Speroni ◽  
Rodolfo Héctor Campos ◽  
Diego Martín Flichman

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.


2004 ◽  
Vol 102 (2) ◽  
pp. 133-139 ◽  
Author(s):  
Jing-Chyi Wang ◽  
Shih-Lan Hsu ◽  
Guang-Yuh Hwang

2000 ◽  
Vol 44 (12) ◽  
pp. 3402-3407 ◽  
Author(s):  
Lei Fu ◽  
Yung-Chi Cheng

ABSTRACT l-Nucleoside analogs are new therapeutic agents for treatment of chronic hepatitis B. However, their clinical application was limited by the emergence of viral resistance. It is important to develop a new system to evaluate drug cross-resistance and to test new agents that may overcome resistant virus. In this report, three cell lines HepG2-WT10, HepG2-SM1, and HepG2-DM2 are presented; these cell lines were established by transfection of HepG2 cells with unique fully functional 1.1× hepatitis B virus (HBV) genomes: wild-type HBV-adr and its L526M and L526MM550V variants, respectively. We have demonstrated that these genomes have different susceptibilities to lamivudine [l(−)SddC] and penciclovir (PCV). By examining HBV RNA transcription, antigen expression, progeny DNA replication, and viral susceptibilities to l(−)SddC, PCV, and other nucleoside analogs, it is concluded that the cell lines are able to stably producel(−)SddC- and PCV-sensitive and -resistant HBV virions. In addition, the relative susceptibilities of the wild-type and mutant HBV produced from the stably transfected cell lines to several anti-HBV nucleoside analogs were also examined and found to be about the same as those found by using a transient infection system. PMEA [9-(2-phosphonylmethoxytehyl)-adenine] and QYL685 are able to suppress l(−)SddC- and PCV-resistant HBV. In conclusion, this cell culture system is a novel and useful tool for evaluating anti-HBV compounds and biologics.


2007 ◽  
Vol 1 (1) ◽  
pp. 41-46 ◽  
Author(s):  
Mamun-Al-Mahtab ◽  
Salimur Rahman ◽  
Mobin Khan ◽  
Ayub Mamun ◽  
Kamal

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