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X protein of hepatitis B virus functions as a transcriptional corepressor on the human telomerase promoter†
Article first published online: 8 JUN 2007
Copyright © 2007 American Association for the Study of Liver Diseases
Volume 46, Issue 2, pages 402–413, August 2007
How to Cite
Su, J.-M., Lai, X.-M., Lan, K.-H., Li, C.-P., Chao, Y., Yen, S.-H., Chang, F.-Y., Lee, S.-D. and Lee, W.-P. (2007), X protein of hepatitis B virus functions as a transcriptional corepressor on the human telomerase promoter. Hepatology, 46: 402–413. doi: 10.1002/hep.21675
Potential conflict of interest: Nothing to report.
- Issue published online: 27 JUL 2007
- Article first published online: 8 JUN 2007
- Manuscript Accepted: 12 FEB 2007
- Manuscript Received: 23 JUL 2006
- National Science Council, Taiwan. Grant Numbers: NSC93-2320-B-075-013, NSC94-2320-B-075-014
- Taipei Veterans General Hospital, Taiwan. Grant Numbers: VGH93-183, VGH94-191, VGH94023
The X protein of hepatitis B virus (HBx) is essential for transactivation of hepatitis B viral and host cellular genes. It has been specifically implicated in the development of hepatocellular carcinoma; however, the molecular mechanism remains unknown. Telomeres, the DNA-protein complexes at the ends of eukaryotic chromosomes, protect chromosomes from degradation at the terminal regions, fusion with a broken DNA end, and inappropriate recombination. The shortening of telomeres that occurs during hepatocellular carcinogenesis has been well studied. In the present study, we isolated an HBx isoform that resulted in telomere shortening in hepatoma cell lines. We found that this HBx isoform down-regulated the expression of human telomerase by transcriptionally repressing its promoter. To further determine the molecular mechanism, we examined human telomerase promoter and identified myc-associated zinc finger protein (MAZ) as a transcriptional repressor of the promoter. We found that the HBx isoform achieved transcriptional suppression of human telomerase by enhancing MAZ binding to its consensus sequence in the promoter through physical association with MAZ. Conclusion: The data suggest that HBx can induce telomere shortening by acting as a transcriptional corepressor of MAZ on the human telomerase promoter. (HEPATOLOGY 2007.)