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Journal of Virology, November 1998, p. 8710-8717, Vol. 72, No. 11
Department of Molecular Genetics and
Microbiology, The University of New Mexico School of Medicine,
Albuquerque, New Mexico 87131
Received 13 May 1998/Accepted 14 August 1998
Double-stranded linear DNA is synthesized as a minor viral DNA
species by all hepadnaviruses. In a previous study (W. Yang and J. Summers, J. Virol. 69:4029-4036, 1995) we showed that virus particles containing linear DNA of the duck hepatitis B virus (DHBV)
could initiate an infection of primary duck hepatocytes. In cells
infected by linear DNA containing viruses the transcriptional template,
covalently closed circular DNA, was formed by circularization of linear
DNA by nonhomologous recombination between the two ends. This process
was shown to result in viral DNA replication through multiple
generations of linear DNA intermediates, a process we called
illegitimate replication. In this study we showed that viruses
containing linear DHBV DNA produced by engineered insertions in the r
sequence, which encodes the 5' end of the pregenome, could infect
hepatocytes in vivo, and these hepatocytes proceeded to carry out
illegitimate replication. Nonhomologous recombination quickly produced
revertants and partial revertants in which all or part of the insertion
was deleted. One such partial revertant that replicated primarily
through circular DNA intermediates, but which synthesized elevated
levels of linear DNA, could be sustained for several days as the
predominant genotype in vivo, but this mutant was eventually displaced
by variants showing full reversion to legitimate replication and that
synthesized normal low levels of linear DNA. Full revertants did not
necessarily contain the wild-type r sequence. The results suggest that
the linear DNA produced during DHBV infection initiates cycles of illegitimate replication by generating mutants with altered r sequences. Some r sequence mutants carry out a mixture of legitimate and illegitimate replication that can contribute to elevated production of linear DNA in individual cells.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Infection of Ducklings with Virus Particles
Containing Linear Double-Stranded Duck Hepatitis B Virus DNA:
Illegitimate Replication and Reversion
*
Corresponding author. Mailing address: Department of
Molecular Genetics and Microbiology, The University of New Mexico
School of Medicine, Albuquerque, NM 87131. Phone: (505) 272-8896. Fax: (505) 272-8896. E-mail: jsummer{at}unm.edu.
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