scholarly journals Induction of the DNA-binding activity of c-jun/c-fos heterodimers by the hepatitis B virus transactivator pX.

1994 ◽  
Vol 14 (2) ◽  
pp. 989-998 ◽  
Author(s):  
G Natoli ◽  
M L Avantaggiati ◽  
P Chirillo ◽  
A Costanzo ◽  
M Artini ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Hepatitis B Virus ◽  
Protein Kinase ◽  
Dna Binding ◽  
Hepatitis B ◽  
Cell Lines ◽  
Binding Activity ◽  
Dna Binding Activity ◽  
Kinase C ◽  
B Virus

The hepatitis B virus (HBV) X protein (pX) is capable of activating transcription regulated by viral and cellular promoters containing binding sites for different transcription factors, including AP1. In this study we have analyzed the mechanisms of AP1 induction by pX. The hepatitis B virus transactivator was able to activate TRE (12-O-tetradecanoylphorbol-13-acetate response element)-directed transcription in different cell lines, including HepG2, HeLa, CV1, and PLC/PRF/5 cells. pX-induced AP1 activation in HepG2 cells was associated with an increase in the DNA-binding activity of c-Jun/c-Fos heterodimers, which was not dependent either on an increase in the overall amount of c-Fos and c-Jun proteins in the cells or on formation of dimers between pX and the two proteins, thus suggesting the involvement of posttranslational modifications of the transcription factor. The observation that the overexpression of c-Jun and c-Fos in the cells results in a strong augmentation of the effect of pX on TRE-directed transcription is additional evidence indicating the involvement of posttranscriptional modifications of c-Jun/c-Fos heterodimers. The increased AP1 binding observed in the presence of pX was unaffected by the protein kinase C inhibitors calphostin C and sphingosine and by the protein kinase A inhibitor HA1004, while it was almost completely blocked by staurosporine, a potent and nonspecific protein kinase inhibitor, suggesting that protein kinase C- and A-independent phosphorylation events might play a role in the phenomenon. The ability of pX also to increase TRE-directed transcription in cell lines in which AP1-binding activity is not increased (i.e., HeLa, CV1, and PLC/PRF/5 cells) suggests that pX can activate canonical TRE sites by different mechanisms as well.

scholarly journals Interferon-α suppresses hepatitis B virus enhancer II activity via the protein kinase C pathway

Virology ◽  
2012 ◽  
Vol 432 (2) ◽  
pp. 452-459 ◽  
Author(s):  
Takatoshi Nawa ◽  
Hisashi Ishida ◽  
Tomohide Tatsumi ◽  
Wei Li ◽  
Satoshi Shimizu ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Hepatitis B Virus ◽  
Protein Kinase ◽  
Hepatitis B ◽  
Interferon Α ◽  
Kinase C ◽  
B Virus ◽  
Enhancer Ii

Activation of protein kinase C decreases phosphorylation of c-Jun at sites that negatively regulate its DNA-binding activity

Cell ◽  
1991 ◽  
Vol 64 (3) ◽  
pp. 573-584 ◽  
Author(s):  
William J. Boyle ◽  
Tod Smeal ◽  
Libert H.K. Defize ◽  
Peter Angel ◽  
James R. Woodgett ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Dna Binding ◽  
Binding Activity ◽  
Dna Binding Activity ◽  
Kinase C

The hepatitis B virus transactivator HBx causes elevation of diacylglycerol and activation of protein kinase C

1993 ◽  
Vol 144 ◽  
pp. 311-321 ◽  
Author(s):  
B. Luber ◽  
U. Lauer ◽  
L. Weiss ◽  
M. Höhne ◽  
P.H. Hofschneider ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Hepatitis B Virus ◽  
Protein Kinase ◽  
Hepatitis B ◽  
Kinase C ◽  
B Virus

scholarly journals Cross-coupling of signal transduction pathways: the dioxin receptor mediates induction of cytochrome P-450IA1 expression via a protein kinase C-dependent mechanism.

1993 ◽  
Vol 13 (1) ◽  
pp. 677-689 ◽  
Author(s):  
A Berghard ◽  
K Gradin ◽  
I Pongratz ◽  
M Whitelaw ◽  
L Poellinger
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Dna Binding ◽  
Binding Activity ◽  
Dna Binding Activity ◽  
Kinase C ◽  
The Individual ◽  
Dioxin Receptor

Signal transduction by dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin) is mediated by the intracellular dioxin receptor which, in its dioxin-activated state, regulates transcription of target genes encoding drug-metabolizing enzymes, such as cytochrome P-450IA1 and glutathione S-transferase Ya. Exposure of the dioxin receptor to dioxin leads to an apparent translocation of the receptor to the nucleus in vivo and to a rapid conversion of the receptor from a latent, non-DNA-binding form to a species that binds to dioxin-responsive positive control elements in vitro. This DNA-binding form of receptor appears to be a heterodimeric complex with the helix-loop-helix factor Arnt. In this study, we show that activation of the cytochrome P-450IA1 gene and minimal dioxin-responsive reporter constructs by the dioxin receptor was inhibited following prolonged treatment of human keratinocytes with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate. Inhibition of the receptor-mediated activation response was also achieved by treatment of the cells with a number of protein kinase inhibitors, one of which, calphostin C, shows selectivity for protein kinase C. Taken together, these data suggest that protein kinase C-dependent phosphorylation may play an essential role in the dioxin signaling pathway. This hypothesis is supported by the observation that pretreatment of the cells with 12-O-tetradecanoylphorbol-13-acetate inhibited the DNA-binding activity of the dioxin receptor in vivo. In vivo, the dioxin receptor was found to be a phosphoprotein. In vitro, dephosphorylation of the ligand-activated, heteromeric dioxin receptor form or dephosphorylation of the individual ligand-binding and Arnt receptor subunits inhibited the xenobiotic response element-binding activity. Moreover, dephosphorylation experiments with the individual receptor subunits prior to assembly of the xenobiotic response element-binding receptor form indicated that phosphorylation seemed to be important for the DNA-binding activity per se of the receptor, whereas Arnt appeared to require phosphorylation to interact with the receptor. Finally, a protein kinase C inhibitor-sensitive cytosolic catalytic activity that could restore the DNA-binding activity of the dephosphorylated dioxin receptor form was identified.

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