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Transcription of hepatitis B virus covalently closed circular DNA is regulated by CpG methylation during chronic infection.

ABSTRACT: The persistence of hepatitis B virus (HBV) infection is maintained by the nuclear viral covalently closed circular DNA (cccDNA), which serves as transcription template for viral mRNAs. Previous studies suggested that cccDNA contains methylation-prone CpG islands, and that the minichromosome structure of cccDNA is epigenetically regulated by DNA methylation. However, the regulatory effect of each CpG island methylation on cccDNA activity remains elusive. In the present study, we analyzed the distribution of CpG methylation within cccDNA in patient samples and investigated the impact of CpG island methylation on cccDNA-driven virus replication. Our study revealed the following observations: 1) Bisulfite sequencing of cccDNA from chronic hepatitis B patients indicated that CpG island I was seldom methylated, 2) CpG island II methylation was correlated to the low level of serum HBV DNA in patients, and in vitro methylation studies confirmed that CpG island II methylation markedly reduced cccDNA transcription and subsequent viral core DNA replication, 3) CpG island III methylation was associated with low serum HBsAg titers, and 4) Furthermore, we found that HBV genotype, HBeAg positivity, and patient age and liver fibrosis stage were also relevant to cccDNA CpG methylation status. Therefore, we clearly demonstrated that the status of cccDNA methylation is connected to the biological behavior of HBV. Taken together, our study provides a complete profile of CpG island methylation within HBV cccDNA and new insights for the function of CpG methylation in regulating HBV cccDNA transcription.

SUBMITTER: Zhang Y

PROVIDER: S-EPMC4206413 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Transcription of hepatitis B virus covalently closed circular DNA is regulated by CpG methylation during chronic infection.

Zhang Yongmei Y Mao Richeng R Yan Ran R Cai Dawei D Zhang Yijun Y Zhu Haoxiang H Kang Yaoyue Y Liu Hongyan H Wang Jinyu J Qin Yanli Y Huang Yuxian Y Guo Haitao H Zhang Jiming J

PloS one 20141022 10

The persistence of hepatitis B virus (HBV) infection is maintained by the nuclear viral covalently closed circular DNA (cccDNA), which serves as transcription template for viral mRNAs. Previous studies suggested that cccDNA contains methylation-prone CpG islands, and that the minichromosome structure of cccDNA is epigenetically regulated by DNA methylation. However, the regulatory effect of each CpG island methylation on cccDNA activity remains elusive. In the present study, we analyzed the dist ...[more]

PMID: 25337821

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Project description:The purpose of this study was to explore the correlations of serum hepatitis B core-related antigen (HBcrAg) with intrahepatic Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) and HBV total DNA in hepatitis B e antigen (HBeAg)-positive chronic hepatitis B (CHB) patients. Serum HBcrAg and other parameters, including HBV DNA, HBV RNA, HBeAg, hepatitis B surface antigen (HBsAg), hepatitis B core antibody (anti-HBc), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were quantitatively measured at baseline and follow-up time points. Intrahepatic HBV cccDNA and total DNA were quantitatively detected at baseline and 96?weeks. Grading of liver necroinflammation and staging of hepatic fibrosis were assessed at baseline and 96?weeks. Correlations between serum HBcrAg and other parameters were analyzed by Pearson's correlation analysis. The results showed that pretreatment HBcrAg correlated significantly with HBV total DNA levels (r?=?0.328, P? =?0.003) in 82 CHB patients, and, after removing three outliers, with intrahepatic HBV cccDNA (r?=?0.323, P? =?0.004; n?=?79). Serum HBcrAg correlated better with HBV cccDNA in patients with lower levels of serum HBV DNA (stratified by 7?log IU/ml of HBV DNA; r?=?0.656, P? =?0.003 versus r?=?-0.02, P = 0.866). Significant inverse correlations were found between HBcrAg and grade of liver necroinflammation (r?=?-0.245, P? =?0.037), stage of hepatic fibrosis (r?=?-0.360, P? =?0.002) at baseline. Serum HBcrAg presented significant correlation with intrahepatic HBV cccDNA in patients with HBeAg seroconversion at 96?weeks (r?=?0.622, P? =?0.006). The decrease in HBcrAg showed significant correlation with the decrease in HBV cccDNA after 96-week NA therapy (r?=?0.282, P? =?0.043). Serum HBcrAg also correlated significantly with other serum markers at baseline and 96 weeks of NA therapy. In conclusion, baseline HBcrAg and its decreased value were significantly correlated with the corresponding intrahepatic HBV cccDNA.

Project description:Background & aimsHBV has a narrow host restriction, with humans and chimpanzees representing the only known natural hosts. The molecular correlates of resistance in species that are commonly used in biomedical research, such as mice, are currently incompletely understood. Expression of human NTCP (hNTCP) in mouse hepatocytes enables HBV entry, but subsequently covalently closed circular (cccDNA) does not form in most murine cells. It is unknown if this blockade in cccDNA formation is due to deficiency in repair of relaxed circular DNA (rcDNA) to cccDNA.MethodsHere, we deployed both in vivo and in vitro virological and biochemical approaches to investigate if murine cells contain a complete set of repair factors capable of converting HBV rcDNA to cccDNA.ResultsWe demonstrate that HBV cccDNA does form in murine cell culture or in mice when recombinant rcDNA without a protein adduct is directly introduced into cells. We further show that the murine orthologues of core components in DNA lagging strand synthesis, required for the repair of rcDNA to cccDNA in human cells, can support this crucial step in the HBV life cycle. It is worth noting that recombinant HBV rcDNA substrates, either without a protein adduct or containing neutravidin to mimic HBV polymerase, were used in our study; it remains unclear if the HBV polymerase removal processes are the same in mouse and human cells.ConclusionsCollectively, our data suggest that the HBV life cycle is blocked post entry and likely before the repair stage in mouse cells, which yields critical insights that will aid in the construction of a mouse model with inbred susceptibility to HBV infection.Lay summaryHepatitis B virus (HBV) is only known to infect humans and chimpanzees in nature. Mouse models are often used in modeling disease pathogenesis and preclinical research to assess the efficacy and safety of interventions before they are then tested in human participants. However, because mice are not susceptible to HBV infection it is difficult to accurately model human infection (and test potential treatments) in mouse models. Herein, we have shown that mice are able to perform a key step in the HBV life cycle, tightening the net around the possible reason why HBV can not efficiently infect and replicate in mice.

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Transcription of hepatitis B virus covalently closed circular DNA is regulated by CpG methylation during chronic infection.

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Transcription of hepatitis B virus covalently closed circular DNA is regulated by CpG methylation during chronic infection.

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