- 作者: Dynamics of HBV cccDNA expression and transcription in different cell growth phase
- 作者服務機構: Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, ROC
- 中文摘要: --
- 英文摘要:
Background: The 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.
Methods: We 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.
Results: In 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.
Conclusions: Based 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. - 中文關鍵字: --
- 英文關鍵字: HBV, cccDNA, viral replication, cell proliferation, growth confluency