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  • Title: Hepatitis B virus X mutants derived from human hepatocellular carcinoma retain the ability to abrogate p53-induced apoptosis.
    Author: Huo TI, Wang XW, Forgues M, Wu CG, Spillare EA, Giannini C, Brechot C, Harris CC.
    Journal: Oncogene; 2001 Jun 21; 20(28):3620-8. PubMed ID: 11439325.
    Abstract:
    Chronic hepatitis B virus (HBV) infection and the integration of its X gene (HBx) are closely associated with the development of hepatocellular carcinoma (HCC). The integrated HBx frequently is truncated or contains point mutations. Previous studies indicated that these HBx mutants have a diminished co-transactivational activity. We have compared the effects of wild-type (wt) HBx and its naturally occurring mutants derived from human HCCs on transcriptional co-transactivation, apoptosis and interactive effects with p53. We demonstrated that overexpression of mutant, but not wt HBx, is defective in transcriptional co-transactivation of the NF-kappaB-driven luciferase reporter. By using a microinjection technique, the HBx mutants were shown to have an attenuated pro-apoptotic activity. This deficiency may be attributed to multiple mutations in the co-transactivation domain of HBx, that leads to decreased stability of the translated product. However, wt or mutant HBx bind to p53 in vitro and retain their ability to block p53-mediated apoptosis in vivo, which has been implicated as its major tumor suppressor function. The abrogation of p53-mediated apoptosis by integrated HBx mutants may provide a selective clonal advantage for preneoplastic or neoplastic hepatocytes and contribute to hepatocellular carcinogenesis.
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