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Journal of Virology, January 2000, p. 892-898, Vol. 74, No. 2
Howard Hughes Medical Institute, Departments
of Medicine, Microbiology, and Immunology, University of California
at San Francisco, San Francisco, California 94143-0703
Received 16 July 1999/Accepted 4 October 1999
Transcriptional transactivators (Tat) from human immunodeficiency
and equine infectious anemia viruses (HIV and EIAV) interact with their
transactivation response elements (TAR) to increase the rates of viral
transcription. Whereas the human cyclin T1 is required for the binding
of Tat to TAR from HIV, it is unknown how Tat from EIAV interacts with
its TAR. Furthermore, Tat from EIAV functions in equine and canine
cells but not in human cells. In this study, we present sequences of
cyclins T1 from horse and dog and demonstrate that their N-terminal 300 residues rescue the transactivation of Tat from EIAV in human cells.
Although human and equine cyclins T1 bind to this Tat, only the equine cyclin T1 supports the binding of Tat to TAR from EIAV. Finally, a
reciprocal exchange of the valine for the leucine at position 29 in
human and equine cyclins T1, respectively, renders the human cyclin T1
active and the equine cyclin T1 inactive for Tat transactivation from
EIAV. Thus, the collaboration between a specific cyclin T1 and Tat for
their high-affinity interaction with TAR is a common theme of
lentiviral transactivation.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Interactions between Equine Cyclin T1, Tat, and TAR
Are Disrupted by a Leucine-to-Valine Substitution Found in Human
Cyclin T1
*
Corresponding author. Mailing address: UCSF Mt. Zion
Box 0703, 3rd and Parnassus Ave., San Francisco, CA 94143-0703. Phone: (415) 502-1905. Fax: (415) 502-1901. E-mail:
matija{at}itsa.ucsf.edu.
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