p53 Promotes proteasome-dependent degradation of oncogenic protein HBx by transcription of MDM2.
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.
State Key Laboratory of Genetic Engineering, Institute of Genetics, School of Life Sciences, Fudan University, 220 Handan Road, Shanghai 200433, People's Republic of China.
Lingling
L
Xian
Jing
J
Zhao
Jia
J
Wang
Zhou
Z
Fang
Bo
B
Peng
Wenzhang
W
Wang
Xiaona
X
Ji
Long
L
Yu
D000818:Animals; D045744:Cell Line, Tumor; D006801:Humans; D051379:Mice; D009857:Oncogenes; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D055550:Protein Stability; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D054875:Ubiquitination; D054334:Viral Regulatory and Accessory Proteins
D015534:Trans-Activators; D016159:Tumor Suppressor Protein p53; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D051736:Proto-Oncogene Proteins c-mdm2; D046988:Proteasome Endopeptidase Complex