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

Abstract

(13,28,42,49,55) and cellular (10,23,27,47,56) Phosphorylation and dephosphorylation of c-Fos and c-Jun have been described as posttranslational modifications with a critical role in the regulation of AP1 function. Phosphorylation of the c-Fos C terminus seems to be important for negative autoregulation and for transformation (34,46) but not for transactivation of genes linked to an AP1 site.

Viruses, Immunity, and Cancer: Lessons from Hepatitis B

“…On the other hand, most tumors contain clonally integrated HBV DNA and microdeletions in the flanking cellular DNA which could, theoretically, deregulate cellular growth control mechanisms. 86 Furthermore, the HBV X gene product has been shown to transactivate cellular genes associated with cellular growth control [87][88][89] and inhibit p53 gene function in vitro 90 , suggesting that deregulated X gene expression from integrated fragments of subviral DNA could play a role in hepatocarcinogenesis. 91 Similarly, C-terminally truncated viral envelope proteins expressed from integrated subviral DNA may have transactivating activity 92,93 and could, potentially, contribute to carcinogenesis in chronic HBV infection.…”

Signal transduction cascades and hepatitis B and C related hepatocellular carcinoma

“…Several reports indicated that HBx induces activation of the transcription factor activator protein-1 (AP-1), a dimer consisting of Fos and Jun proteins; however, it does not accomplish this through a direct interaction. [101][102][103][104][105][106] This led to the discovery that HBx increases the activation of Ras, a GTP-binding protein which lies upstream in the MAPK signaling cascade. As shown in Fig.…”

Hepatitis B Virus X Protein Is a Transcriptional Modulator That Communicates with Transcription Factor IIB and the RNA Polymerase II Subunit 5

“…1A). Comparable amounts of proteins were applied and fractionated by SDS-PAGE as shown by Coomassie Blue staining (lanes [25][26][27][28][29][30]. The RPB5 probe bound to TFIIB with high affinity (lane 2) as well as to HBx and to itself as reported (lanes 4 and 6) (18).…”