Identification of androgen response elements in the enhancer I of hepatitis B virus: A mechanism for sex disparity in chronic hepatitis B

Authors

  • Sheng-Han Wang,

    Corresponding author
    1. Department of Microbiology, 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
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    • fax: 886-2-23825962.

  • Shiou-Hwei Yeh,

    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
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  • Wei-Hsiang Lin,

    1. Department of Microbiology, National Taiwan University College of Medicine, Taipei, Taiwan
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  • Hurng-Yi Wang,

    1. Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
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  • Ding-Shinn Chen,

    1. National Taiwan University Center for Genomic Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
    2. Department of Internal Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
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  • Pei-Jer Chen

    1. National Taiwan University Center for Genomic Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
    2. Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
    3. Department of Internal Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
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  • Potential conflict of interest: Nothing to report.

Abstract

Hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) occurs more often in men than in women. Male HBV carriers usually have higher viral loads, which is a well-known risk factor for HCC. Whether and how the male androgen axis regulates HBV transcription and replication is investigated here. We used HBV transgenic mice to evaluate any sex disparity of serum hepatitis B surface antigen and HBV titers as well as the castration effect on this disparity. Compared to females, HBV transgenic male mice showed higher hepatitis B surface antigen and viral titers, which were lessened by castration of the males. In a cell culture system, HepG2 cells transfected with HBV and androgen receptor (AR) constructs were used to study the effect of the androgen pathway on viral transcription and replication. We found the ligand-stimulated AR could increase the transcription of HBV RNAs through its transcription activation domain. A genomic region within HBV enhancer I was identified that is responsible for the transcriptional activation of AR. The results from chromatin immunoprecipitation and in vitro binding assays further demonstrated a direct binding of AR to this region, in a ligand-dependent manner. Two androgen-responsive element motifs in this region were identified, and their mutations can significantly abolish the AR effects. Conclusion: This study demonstrated that the androgen pathway can increase the transcription of HBV through direct binding to the androgen-responsive element sites in viral enhancer I. This may explain a higher HBV titer in male carriers and an increased risk of HCC. (HEPATOLOGY 2009.)

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