Synthesis of the covalently closed circular (ccc) DNA is a critical, but not well-understood step in the life cycle of hepadnaviruses. Our previous studies favor a model that removal of genome-linked viral DNA polymerase occurs in the cytoplasm and the resulting deproteinized relaxed circular DNA (DP-rcDNA) is subsequently transported into the nucleus and converted into cccDNA. In support of this model, our current study showed that deproteinization of viral double-stranded linear (dsl) DNA also took place in the cytoplasm. Furthermore, we demonstrated that Ku80, a component of non-homologous end joining DNA repair pathway, was essential for synthesis of cccDNA from dslDNA, but not rcDNA. In an attempt to identify additional host factors regulating cccDNA biosynthesis, we found that the DP-rcDNA was produced in all tested cell lines that supported DHBV DNA replication, but cccDNA was only synthesized in the cell lines that accumulated high levels of DP-rcDNA, except for NCI-H322M and MDBK cells, which failed to synthesize cccDNA despite of the existence of nuclear DP-rcDNA. The results thus imply that while removal of the genome-linked viral DNA polymerase is most likely catalyzed by viral or ubiquitous host function(s), nuclear factors required for the conversion of DP-rcDNA into cccDNA and/or its maintenance are deficient in the above two cell lines, which could be useful tools for identification of the elusive host factors essential for cccDNA biosynthesis or maintenance.
Characterization of the Host Factors Required for Hepadnavirus Covalently Closed Circular (ccc) DNA Formation
Creators
Haitao Guo - Drexel University
Chunxiao Xu - Drexel University
Tianlun Zhou - Hepatitis B Foundation
Timothy M. Block - Drexel University
Ju-Tao Guo - Drexel University
Publication Details
PloS one, v 7(8), pp e43270-e43270
Publisher
Public Library Science
Number of pages
10
Grant note
AI094474 / National Institutes of Health; United States Department of Health & Human Services; National Institutes of Health (NIH) - USA
Commonwealth of Pennsylvania
R01AI094474 / NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES; United States Department of Health & Human Services; National Institutes of Health (NIH) - USA; NIH National Institute of Allergy & Infectious Diseases (NIAID)
Hepatitis B Foundation
Resource Type
Journal article
Language
English
Academic Unit
Microbiology and Immunology
Web of Science ID
WOS:000307500100075
Scopus ID
2-s2.0-84865060138
Other Identifier
991019167338204721
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