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Journal of Virology, January 1999, p. 608-617, Vol. 73, No. 1
Department of Molecular Biology, The Scripps
Research Institute, La Jolla, California 92037
Received 28 May 1998/Accepted 5 October 1998
The long PCR technique was used to amplify the three size classes
of viral mRNAs produced in cells infected by feline immunodeficiency virus (FIV). We identified in the env region a new splice
acceptor site that generated two transcripts, each coding for an 11-kDa protein, p11rev, whose function is unknown. The
small-size class of mRNAs included two bicistronic orf2/rev
mRNAs and two rev-like mRNAs, consisting only of the second
exon of rev and coding for a 15-kDa protein, p15rev. p15rev
contained the minimal effector domain of Rev and was sufficient to
mediate partial Rev activity. The bicistronic mRNAs encoded two
distinct proteins, one of 23 kDa corresponding to Rev and a 9-kDa
protein encoded by the orf2 gene. The orf2 gene product is a protein of
79 amino acids with characteristics similar to those of the Tat
(transactivator) proteins of the ungulate lentiviruses. Transient
expression assays, using the FIV long terminal repeat (LTR) to drive
transcription of the bacterial gene for chloramphenicol acetyltransferase demonstrated that the orf2 gene transactivates gene
expression an average of 14- to 20-fold above the basal level. Deletion
mutants of the FIV LTR were generated to locate sequences responsive to
transactivation mediated by the orf2 gene. A 5' deletion mutant that
removed the AP1 site resulted in residual low-level transactivation by
orf2. Further experiments using LTR mutants with internal deletions
identified three regions located between positions
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Demonstration that orf2 Encodes the Feline
Immunodeficiency Virus Transactivating (Tat) Protein and
Characterization of a Unique Gene Product with Partial Rev
Activity
126 and
47
relative to the cap site that were important for orf2-directed
transactivation. These regions include the AP1 site, a C/EBP tandem
repeat, and an ATF site.
*
Corresponding author. Mailing address: The Scripps
Research Institute, Department of Molecular Biology, 10550 N. Torrey
Pines Rd., La Jolla, CA 92037. Phone: (619) 784-8270. Fax: (619)
784-2750. E-mail: jelder{at}scripps.edu.
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