Hepatitis B virus X protein enhances the transcriptional... : Hepatology (original) (raw)

Viral Hepatitis

Hepatitis B virus X protein enhances the transcriptional activity of the androgen receptor through c-Src and glycogen synthase kinase-3β kinase pathways#

Yang, Wan-Jen1†; Chang, Ching-Ju1†; Yeh, Shiou-Hwei1,2*‡; Lin, Wei-Hsiang1; Wang, Sheng-Han1; Tsai, Ting-Fen3; Chen, Ding-Shinn2,4; Chen, Pei-Jer2,4,5

1 Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan

2 National Taiwan University Center for Genomic Medicine, National Taiwan University College of Medicine, Taipei, Taiwan

3 Faculty of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan

4 Department of Internal Medicine, National Taiwan University College of Medicine, Taipei, Taiwan

5 Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan

* Department of Microbiology, National Taiwan University College of Medicine, No. 1, Jen-Ai Road, Section 1, Taipei 100, Taiwan

Email:[email protected]

Received November 15, 2008; accepted December 25, 2008.

Published online 9 February 2009 in Wiley InterScience (www.interscience.wiley.com).

Grant sponsor: National Research Program of Genomic Medicine; Grant sponsor: National Science Council, Taiwan; Grant Numbers: NSC96-3112-B-002-010- NSC97-3112-B-002-030-.

# Potential conflict of interest: Nothing to report.

† These authors contributed equally to this work.

‡ fax: (886)-2-23825962

Additional Supporting Information may be found in the online version of this article.

Abstract

Hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) occurs predominantly in men. By enhancing the transcriptional activity of the androgen receptor (AR) gene in a ligand-dependent manner, the HBV X protein (HBx) might contribute to this disparity between sexes. To dissect the mechanisms underlying HBx-enhanced AR transactivation, we investigated the effect of HBx on two critical steps in the regulation of ligand-stimulated AR activities. One step is the dimerization of AR (through the interaction of its N-termini and C-termini), and the other step is the activation of the AR N-terminal transactivation domain (NTD). HBx increased the NTD activation of the AR through c-Src kinase. HBx also enhanced AR dimerization by inhibiting glycogen synthase kinase-3β (GSK-3β) activity, which acts as a negative regulator of the interaction between AR and the N-termini and C-termini. The HBx-enhanced AR transactivation was abolished by blocking c-Src and activating GSK-3β kinases simultaneously, suggesting that these two kinases act as major switches in the activation process. The regulatory function of both kinases has been further verified in primary hepatocytes isolated from the livers of HBx transgenic male mice. Conclusion: Our study thus identified two key kinases through which HBx enhances the AR transcriptional activity. These kinases might be potential candidates for future prevention or therapy for HBV-related HCC in men. (Hepatology 2009.)