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

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.

Hepatitis B Virus X Protein and Hepatocarcinogenesis

“…This effect can be reversed by 5‑aza‑CdR, a methyl enzyme inhibitor [ 27 ]. Similar results are observed in protocadherin 10 (PCDH10), caveolin-1, and metastasis-associated protein 1 (MTA1) [ 28 , 29 , 30 ]. Some normally-hypermethylated intragenic CpG islands (mCGIs) have been observed to be hypomethylation before the development of HCC in HBx transgenic mouse liver.…”

Hepigenetics: A Review of Epigenetic Modulators and Potential Therapies in Hepatocellular Carcinoma

“…In HCC of HBV etiology, the normally silenced metastasis-associated protein 1 ( MTA1 ) gene was upregulated by recruitment of DNMT3a and DNMT3b leading to hypomethylation of its promoter and increasing the tumor metastatic disposition [ 23 ]. Additionally, DNMT3b was elsewhere reported to be overexpressed by telomerase reverse transcriptase ( TERT ) in HCC.…”

Hepatitis B Virus X Protein Driven Alpha Fetoprotein Expression to Promote Malignant Behaviors of Normal Liver Cells and Hepatoma Cells

“…Recent studies have reported that HBx plays an critical role in promoting the invasive and metastatic properties of intrahepatic and extrahepatic metastases of HCC, and poor prognosis in hepatitis B virus-related HCC 5 - 7 . HBx increases the invasion potential by upregulating the expression of metastasis-associated proteins 8 , vascular endothelial growth factors, the membrane-type matrix metalloproteinases 9 and miR-148a 6 , which contributes to HCC cells invasion and metastasis. These evidence implicated that HBx play a role not only in inducing development of HCC, but also in promoting malignant behaviors of HCC cells.…”