Epigenetic modification induced by hepatitis B virus X protein via interaction with de novo DNA methyltransferase DNMT3A.
OBJECTIVE
The hepatitis B virus X protein (HBx) has been implicated as a potential trigger of the epigenetic deregulation of some genes, but the underlying mechanisms remain unknown. The aim of this study was to identify underlying mechanisms involved in HBx-mediated epigenetic modification.


METHODS
Interactions between HBx and DNA methyltransferase (DNMT) or histone deacetylase-1 (HDAC1) were assessed by co-immunoprecipitation. DNA methylation of gene promoters was detected by bisulfite sequencing, and HBx-mediated protein binding to gene regulatory elements was evaluated by chromatin immunoprecipitation. Target gene transcriptional activity was measured by real-time polymerase chain reaction.


RESULTS
HBx can interact directly with DNMT3A and HDAC1. HBx recruited DNMT3A to the regulatory promoters of interleukin-4 receptor and metallothionein-1F and subsequently silenced their transcription via de novo DNA methylation. By contrast, the transcription of CDH6 and IGFBP3 was triggered by HBx through the deprivation of DNMT3A from their promoters. Transcriptional levels of target genes in hepatocellular carcinoma (HCC) specimens were strongly correlated with the occurrence of HBx.


CONCLUSIONS
The interaction of HBx and DNMT3A facilitates cellular epigenetic modification (via regional hypermethylation or hypomethylation) at distinct genomic loci, providing an alternative mechanism within HBx-mediated transcriptional regulation, and a profound understanding of hepatitis and HCC pathogenesis.
Zheng
Da-Li
DL
National Human Genome Center of Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Rui-Jin Road II, Shanghai 200025, China.
Zhang
Li
L
Cheng
Na
N
Xu
Xiao
X
Deng
Qing
Q
Teng
Xiao-Mei
XM
Wang
Ke-Sheng
KS
Zhang
Xin
X
Huang
Jian
J
Han
Ze-Guang
ZG
D006528:Carcinoma, Hepatocellular / Q000209:etiology; D002460:Cell Line; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000502:physiology*; D019175:DNA Methylation; D000090205:DNA Methyltransferase 3A; D044127:Epigenesis, Genetic; D005786:Gene Expression Regulation; D006509:Hepatitis B / Q000150:complications; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases / Q000502:physiology; D006801:Humans; D008113:Liver Neoplasms / Q000209:etiology; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000502:physiology*; D054334:Viral Regulatory and Accessory Proteins
C000717967:DNMT3A protein, human; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; C110550:HDAC1 protein, human; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases