Yun C, Lee J H, Park H, Jin Y M, Park S, Park K, Cho H
Department of Biochemistry, Ajou University School of Medicine, Wonchon-dong 5, Paldal-ku, Suwon 442-749, Korea.
Oncogene. 2000 Oct 26;19(45):5163-72. doi: 10.1038/sj.onc.1203896.
Hepatitis B virus X (HBx) protein implicated in the development of liver cancer may inhibit the function of p53 tumor suppressor protein through cytoplasmic retention of p53 protein. Here, we attempt to investigate whether the functional inhibition of p53 protein by HBx protein is reversible. First, we provide the evidence for the association of endogenous p53 protein with HBx by co-immunoprecipitation in stable Chang cells that express HBx protein in an inducible manner (ChangX-34). By immunofluorescence microscopy, the major location of p53 protein of ChangX-34 cells was confirmed at the nuclear periphery as well as in the cytoplasm where HBx protein is mainly expressed. Surprisingly, anticancer drug, adriamycin induces the nuclear translocation of p53 protein sequestered in the cytoplasm. This change is accompanied by the restoration of p53 activity, which results in increased transcriptional activity at the p53-responsive DNA elements as well as increase of p21WAF1 mRNA expression. Further, we observed the induction of cell death and G1 arrest in these cells upon adriamycin treatment regardless of HBx expression. Together, we demonstrate that functional inhibition of p53 protein through its cytoplasmic retention by HBx protein is reversible. These results may be extended into other tumors of which p53 activity is modulated by viral oncoproteins.
与肝癌发生相关的乙型肝炎病毒X（HBx）蛋白可能通过使p53肿瘤抑制蛋白滞留于细胞质中而抑制其功能。在此，我们试图研究HBx蛋白对p53蛋白的功能抑制是否可逆。首先，我们通过免疫共沉淀法在可诱导表达HBx蛋白的稳定Chang细胞（ChangX-34）中提供了内源性p53蛋白与HBx相关联的证据。通过免疫荧光显微镜观察，ChangX-34细胞中p53蛋白的主要定位在核周以及HBx蛋白主要表达的细胞质中得到证实。令人惊讶的是，抗癌药物阿霉素可诱导滞留在细胞质中的p53蛋白发生核转位。这种变化伴随着p53活性的恢复，这导致p53反应性DNA元件处的转录活性增加以及p21WAF1 mRNA表达增加。此外，我们观察到在阿霉素处理后，无论HBx表达情况如何，这些细胞都会发生细胞死亡和G1期阻滞。我们共同证明，HBx蛋白通过使p53蛋白滞留于细胞质中对其进行的功能抑制是可逆的。这些结果可能推广到其他p53活性受病毒癌蛋白调节的肿瘤中。
