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Journal of Virology, February 2000, p. 1718-1726, Vol. 74, No. 4
Division of Basic Sciences, Fred Hutchinson
Cancer Research Center, Seattle, Washington
98109,1 and Department of
Microbiology, University of Washington, Seattle, Washington
981952
Received 28 April 1999/Accepted 15 November 1999
Foamy viruses are complex retroviruses whose replication strategy
resembles that of conventional retroviruses. However, foamy virus
replication also resembles that of hepadnaviruses in many respects.
Because hepadnaviruses replicate in an integrase-independent manner, we
were interested in investigating the characteristics of human foamy
virus (HFV) integration. We have shown that HFV requires a functional
integrase protein for infectivity. Our analyses have revealed that in
single-cell clones derived from HFV-infected erythroleukemia-derived
cells (H92), there were up to 20 proviral copies per host cell genome
as determined by Southern blot and fluorescent in situ hybridization
analysis. Use of specific probes has also shown that a majority of the
proviruses contain the complete tas gene, which encodes the
viral transactivator, and are not derived from
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Multiple Integrations of Human Foamy Virus in
Persistently Infected Human Erythroleukemia Cells
and
tas
cDNAs, which have been shown to arise rapidly in infected cells. To
demonstrate that the multiple proviral sequences are due to integration
instead of recombination, we have sequenced the junctions between the
proviral sequences and the host genome and found that the proviruses
have authentic long terminal repeat ends and that each integration is
at a different chromosomal site. A virus lacking the Gag nuclear
localization signal accumulates fewer proviruses, suggesting that
nuclear translocation is important for high proviral load. Since
persistently infected H92 clones are not resistant to superinfection,
the relative importance of an intracellular versus extracellular
mechanism in proviral acquisition has yet to be determined.
*
Corresponding author. Mailing address: Division of
Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview
Ave. N., Seattle, WA 98109. Phone: (206) 667-4442. Fax: (206) 667-5939. E-mail: mlinial{at}fhcrc.org.
Present address: Division of Clinical Sciences, Fred Hutchinson
Cancer Research Center, Seattle, WA 98109.
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