Abstract
BackgroundThe covalently closed-circular DNA (cccDNA) of hepatitis B virus (HBV) is associated with viral persistence in HBV-infected hepatocytes. However, the regulation of cccDNA and its transcription in the host cells at different growth stages is not well understood.MethodsWe took advantages of a stably HBV-producing cell line, 1.3ES2, and examine the dynamic changes of HBV cccDNA, viral transcripts, and viral replication intermediates in different cellular growth stages.ResultsIn this study, we showed that cccDNA increased suddenly in the initial proliferation phase of cell growth, probably attributable to its nuclear replenishment by intracellular nucleocapsids. The amount of cccDNA then decreased dramatically in the cells during their exponential proliferation similar to the loss of extrachromosomal plasmid DNA during cell division, after which it accumulated gradually while the host cells grew to confluency. We found that cccDNA was reduced in dividing cells and could be removed when proliferating cells were subjected to long term of lamivudine (3TC) treatment. The amounts of viral replicative intermediates were rapidly reduced in these proliferating cells and were significantly increased after cells reaching confluency. The expression levels of viral transcripts were increased in parallel with the elevated expression of hepatic transcription factors (HNF4α, CEBPα, PPARα, etc.) during cell growth confluency. The HBV transcripts were transcribed from both integrated viral genome and cccDNA, however the transcriptional abilities of cccDNA was less efficient then that from integrated viral genome in all cell growth stages. We also noted increases in the accumulation of intracellular viral particles and the secretion of mature virions as the cells reached confluency and ceased to grow.ConclusionsBased on the dynamics of HBV replication, we propose that HBV replication is modulated differently in the different stages of cell growth, and can be divided into three phases (initial proliferation phase, exponential proliferation phase and growth confluency phase) according to the cell growth curve. The regulation of cccDNA in different cell growth phase and its importance regarding HBV replication are discussed.
Highlights
The covalently closed-circular DNA of hepatitis B virus (HBV) is associated with viral persistence in HBV-infected hepatocytes
Dynamics of HBV replication during cell proliferation and growth confluency To explore the dynamics of HBV replication at different cell growth stages, the confluent 1.3ES2 cells were re-plated to initiate cell growth and continuously cultured for 24 days
According to the cell proliferation status, the cell growth curve was divided into three phases including (I) initial proliferation phase, (II) exponential proliferation phase, and (III) growth confluency phase (Figure 1A)
Summary
The covalently closed-circular DNA (cccDNA) of hepatitis B virus (HBV) is associated with viral persistence in HBV-infected hepatocytes. Infection with hepatitis B virus (HBV), which can cause acute and chronic liver diseases, remains one of the most serious viral infections in humans. In CHB patients, a pool of covalently closed circular DNA (cccDNA), generated from the relaxed-circle (RC) form of viral DNA, is maintained in the nuclei of infected hepatocytes and acts as the template for viral gene expression [3]. After treatment with antiviral drugs, the half-life of cccDNA was reported to range from 33 to 57 days in these hepadnaviruese-infected woodchucks and ducks [10,11]. The elimination of cccDNA from infected cells, to achieve viral clearance, has become a major issue in the treatment of chronic HBV infection
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
