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Journal of Virology, November 1998, p. 9217-9223, Vol. 72, No. 11
Department of Human Retrovirology, University
of Amsterdam, Academic Medical Center, Amsterdam, The Netherlands
Received 1 June 1998/Accepted 24 July 1998
The human immunodeficiency virus type 1 RNA genome contains a
terminal repeat (R) sequence that encodes the TAR hairpin motif, which
has been implicated in Tat-mediated activation of transcription. More
recently, a variety of other functions have been proposed for this
structured RNA element. To determine the replicative roles of the 5'
and 3' TAR hairpins, we analyzed multiple steps in the life cycle of
wild-type and mutant viruses. A structure-destabilizing mutation was
introduced in either the 5', the 3', or both TAR motifs of the proviral
genome. As expected, opening of the 5' TAR hairpin caused a
transcription defect. Because the level of protein expression was not
similarly reduced, the translation of this mRNA was improved. No effect
of the 3' hairpin on transcription and translation was measured.
Mutations of the 5' and 3' hairpin structures reduced the efficiency of
RNA packaging to similar extents, and RNA packaging was further reduced
in the 5' and 3' TAR double mutant. Upon infection of cells with these
virions, a reduced amount of reverse transcription products was
synthesized by the TAR mutant. However, no net reverse transcription
defect was observed after correction for the reduced level of virion RNA. This result was confirmed in in vitro reverse transcription assays. These data indicate that the 5' and 3' TAR motifs play important roles in several steps of the replication cycle, but these
structures have no significant effect on the mechanism of reverse
transcription.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
The 5' and 3' TAR Elements of Human Immunodeficiency Virus Exert
Effects at Several Points in the Virus Life Cycle
*
Corresponding author. Mailing address: Department of
Human Retrovirology, Academic Medical Center, University of Amsterdam, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands. Phone:
31-20-5664854. Fax: 31-20-6916531. E-mail:
B.Berkhout{at}AMC.UVA.NL.
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