Hepatitis B virus X protein differentially effects the ubiquitin-mediated proteasomal degradation of β-catenin depending on the status of cellular p53

Jin Kyu Jung, Hyun Jin Kwun, Jung Ok Lee, Payal Arora, Kyung Lib Jang

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

Abnormal accumulation of β-catenin is considered to be a strong driving force in hepatocellular carcinogenesis; however, the mechanism of β-catenin accumulation in tumours is unclear. Here, it was demonstrated that hepatitis B virus X protein (HBx) differentially regulates the level of β-catenin through two ubiquitin-dependent proteasome pathways depending on p53 status. In the presence of p53, HBx downregulated β-catenin through the activation of a p53-Siah-1 proteasome pathway. For this purpose, HBx upregulated Siah-1 expression at the transcriptional level via activation of p53. In the absence of p53, however, HBx stabilized β-catenin through the inhibition of a glycogen synthase kinase-3β-dependent pathway. Interestingly, HBx variants with a Pro-101 to Ser substitution were unable to activate p53 and thus could stabilize β-catenin irrespective of p53 status. Based on these findings, a model of β-catenin regulation by HBx is proposed whereby the balance between the two opposite activities of HBx determines the overall expression level of β-catenin. Differential regulation of β-catenin by HBx depending on host (p53 status) and viral factors (HBx sequence variation) helps not only to explain the observation that cancers accumulating β-catenin also exhibit a high frequency of p53 mutations but also to understand the contradictory reports on the roles of HBx during hepatocellular carcinogenesis.

Original languageEnglish (US)
Pages (from-to)2144-2154
Number of pages11
JournalJournal of General Virology
Volume88
Issue number8
DOIs
StatePublished - Aug 1 2007

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Catenins
Ubiquitin
Proteasome Endopeptidase Complex
Carcinogenesis
hepatitis B virus X protein
Glycogen Synthase Kinase 3
Mutation Rate
Neoplasms
Down-Regulation

All Science Journal Classification (ASJC) codes

  • Virology

Cite this

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title = "Hepatitis B virus X protein differentially effects the ubiquitin-mediated proteasomal degradation of β-catenin depending on the status of cellular p53",
abstract = "Abnormal accumulation of β-catenin is considered to be a strong driving force in hepatocellular carcinogenesis; however, the mechanism of β-catenin accumulation in tumours is unclear. Here, it was demonstrated that hepatitis B virus X protein (HBx) differentially regulates the level of β-catenin through two ubiquitin-dependent proteasome pathways depending on p53 status. In the presence of p53, HBx downregulated β-catenin through the activation of a p53-Siah-1 proteasome pathway. For this purpose, HBx upregulated Siah-1 expression at the transcriptional level via activation of p53. In the absence of p53, however, HBx stabilized β-catenin through the inhibition of a glycogen synthase kinase-3β-dependent pathway. Interestingly, HBx variants with a Pro-101 to Ser substitution were unable to activate p53 and thus could stabilize β-catenin irrespective of p53 status. Based on these findings, a model of β-catenin regulation by HBx is proposed whereby the balance between the two opposite activities of HBx determines the overall expression level of β-catenin. Differential regulation of β-catenin by HBx depending on host (p53 status) and viral factors (HBx sequence variation) helps not only to explain the observation that cancers accumulating β-catenin also exhibit a high frequency of p53 mutations but also to understand the contradictory reports on the roles of HBx during hepatocellular carcinogenesis.",
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Hepatitis B virus X protein differentially effects the ubiquitin-mediated proteasomal degradation of β-catenin depending on the status of cellular p53. / Jung, Jin Kyu; Kwun, Hyun Jin; Lee, Jung Ok; Arora, Payal; Jang, Kyung Lib.

In: Journal of General Virology, Vol. 88, No. 8, 01.08.2007, p. 2144-2154.

Research output: Contribution to journalArticle

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