Epigenetic control of metastasis-associated protein 1 gene expression by hepatitis B virus X protein during hepatocarcinogenesis

M-H Lee,Y-K Shin,M-O Lee,T-Y Na,J-K Seong,H Na

doi:10.1038/oncsis.2012.26

M-H Lee, Y-K Shin + Show 4 more

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https://doi.org/10.1038/oncsis.2012.26

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Journal: Oncogenesis	Publication Date: Sep 1, 2012
Citations: 17	License type: cc-by

Affiliation: Seoul National University

Abstract

Expression of metastasis-associated protein 1 (MTA1) gene correlates with the degree of invasion and metastasis in hepatocellular carcinoma (HCC). Expression of MTA1 is induced by hepatitis B virus X protein (HBx); however, little is known about the transcriptional regulation of MTA1 gene expression. Here, we report that the 5′-flanking region of the human MTA1 promoter contains two CpG islands. Transient expression of HBx in Chang liver cells increased the methylation of the CpG island1 from 18 to 49% when measured by bisulfite-modified direct sequencing. Chromatin immunoprecipitation showed that HBx recruited DNA methyltransferase 3a (DNMT3a) and DNMT3b to the CpG island1. In silico analysis of CpG island1 predicted the existence of putative p53-binding sequences. p53 was pulled down by a DNA probe encoding the p53-binding sequences but not by the methylated DNA probe. The mouse MTA1 promoter also contains a CpG island encoding a p53-binding sequence of which p53 binding was decreased in the presence of HBx, and the expression of MTA1 and DNMT3 was increased in the liver of HBx-transgenic mice. Comparison of MTA1 and DNMT3a expression in the human normal liver and HCC specimens produced a significant correlation coefficient >0.5 (r=0.5686, P=0.0001) for DNMT3a, and a marginally significant coefficient (r=0.3162, P=0.0103) for DNMT3b. These data show that HBx induces methylation of CpG island in the MTA1 promoter, which interferes with DNA binding of p53 in the specific DNA region. This result may explain the molecular mechanism responsible for the induction of MTA1 gene expression by HBx.

Highlights

Chronic infection by hepatitis B virus (HBV) is a major cause of the development and progression of hepatocellular carcinoma (HCC).[1]
HBV X (HBx) is associated with high expression of metastasis-associated protein 1 (MTA1) in HCC, the mechanism underlying this regulation of MTA1 expression is largely unknown
We found that CpG island 1 in the MTA1 promoter contains a p53binding site that is associated with transcriptional repression of MTA1 (Figure 3a).[23]

Summary

INTRODUCTION

Chronic infection by hepatitis B virus (HBV) is a major cause of the development and progression of hepatocellular carcinoma (HCC).[1]. The methylation level of CpG island[1] was about subsequent DNA hypermethylation of the promoter of E-cad- 35%, whereas that of CpG island[2] was about 0.1% in Chang liver herin.[17] HBx induces hypermethylation of the promoters cells, white blood cells, and normal liver tissues obtained from of genes such as insulin-like growth factor-binding protein-3 healthy donors (Figure 1c). Region-containing protein 1 (ASPP1), and ASPP2 by recruiting DNMT1, DNMT3a1, and DNMT3a2.18–21 Here, we report on an important epigenetic regulation of the MTA1 promoter that is Doxycycline increased the methylation level of CpG island[1] in.

RESULTS

DISCUSSION

MATERIALS AND METHODS