Abstract
Hepatitis B virus X protein (HBx) is closely involved in the development of hepatocellular carcinoma (HCC). Tumor suppressor p53 was reported to induce HBx degradation and repress its oncogenic function recently, but the molecular mechanism is unknown. In this study, we attempted to identify the underlying mechanism. We found that overexpression of p53 protein reduces the level of HBx protein and shortens its half-life, however, in MDM2 knock out cells, p53 has no effects on degradation of HBx, meanwhile, overexpression of MDM2 in absence of p53 can accelerate turnover of HBx protein. These indicate that p53-mediated HBx degradation is MDM2-dependent. MDM2 interacts with HBx in vitro and in vivo but does not promote its ubiquitination. In consistent with the results above, HCC tissue samples with wild-type p53 hardly detect HBx protein, whereas, HBx always accumulate in the tissues with mutant p53. Our data provide a possible mechanism on how p53 regulate HBx stability and also a new clue for the study of p53 mutation and HCC development.
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Acknowledgements
We thank Dr. Zhu Minghua for providing the pCMV-Myc-HBx plasmid (Changhai Hospital, the Second Military Medical University, Shanghai, China). This work was supported by the National 973 program of China (2004CB518605), the National 863 project of China (2006AA020501), the National Key Sci-Tech Special Project of China (2008ZX10002-020).
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Supplementary Fig. 1
Detection of HBx protein by western-blot in HBV-positive HCC tissues. a Western-blot analysis of HBx and p53 in HBV-positive HCC tissues with anti-HBx and DO-1 monoclonal antibody. β-actin levels are shown as loading control. p53-MU means samples with mutant p53, and p53-WT means samples with wild-type p53. b Statistical analysis of western-blot results by chi square test in the 36 HBV-positive HCC tissues (JPEG 440 kb)
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Xian, L., Zhao, J., Wang, J. et al. p53 Promotes proteasome-dependent degradation of oncogenic protein HBx by transcription of MDM2. Mol Biol Rep 37, 2935–2940 (2010). https://doi.org/10.1007/s11033-009-9855-1
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DOI: https://doi.org/10.1007/s11033-009-9855-1