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Journal of Virology, November 1998, p. 8659-8668, Vol. 72, No. 11
Institute for Clinical and Molecular
Virology,
Received 12 May 1998/Accepted 17 July 1998
The Rex trans-regulatory protein of human T-cell
leukemia virus type 1 (HTLV-1) is required for the nuclear export of
incompletely spliced and unspliced viral mRNAs and is therefore
essential for virus replication. Rex is a nuclear phosphoprotein that
directly binds to its cis-acting Rex response element RNA
target sequence and constantly shuttles between the nucleus and
cytoplasm. Moreover, Rex induces nuclear accumulation of unspliced
viral RNA. Three protein domains which mediate nuclear import-RNA
binding, nuclear export, and Rex oligomerization have been mapped
within the 189-amino-acid Rex polypeptide. Here we identified a
different region in the carboxy-terminal half of Rex which is also
required for biological activity. In inactive mutants with mutations
that map within this region, as well as in mutants that are deficient
in Rex-specific multimerization, Rex trans activation could
be reconstituted by fusion to a heterologous leucine zipper
dimerization interface. The intracellular trafficking capabilities of
wild-type and mutant Rex proteins reveal that biologically inactive and
multimerization-deficient Rex mutants are still efficiently
translocated from the nucleus to the cytoplasm. This observation
indicates that multimerization is essential for Rex function but is not
required for nuclear export. Finally, we are able to provide an
improved model of the HTLV-1 Rex domain structure.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Multimer Formation Is Not Essential for Nuclear
Export of Human T-Cell Leukemia Virus Type 1 Rex
trans-Activator Protein
*
Corresponding author. Mailing address: Institute for
Clinical and Molecular Virology, University Erlangen-Nürnberg,
Schlossgarten 4, D-91054 Erlangen, Germany. Phone: 49-9131-852 6182. Fax: 49-9131-852 2101. E-mail:
jmhauber{at}viro.med.uni-erlangen.de.
Journal of Virology, November 1998, p. 8659-8668, Vol. 72, No. 11
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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