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Journal of Virology, March 2001, p. 2526-2534, Vol. 75, No. 6
Laboratory of Molecular Virology, Samsung Biomedical
Research Institute, Seoul,1 and
Department of Biological Sciences, Korea Advanced Institute
of Science and Technology, Taejon,2 Korea, and
Department of Microbiology, University of Alabama at
Birmingham, Birmingham, Alabama 352943
Received 29 August 2000/Accepted 19 December 2000
The carboxy terminus-encoding portion of the gag gene
of Mason-Pfizer monkey virus (M-PMV), the prototype immunosuppressive primate type D retrovirus, encodes a 36-amino-acid, proline-rich protein domain that, in the mature virion, becomes the p4 capsid protein. The p4 domain has no known role in M-PMV replication. We found
that two mutants with premature termination codons that remove half or
all of the p4 domain produced lower levels of stable Gag protein and of
self-assembled capsids. Interestingly, yeast two-hybrid screening
revealed that p4 specifically interacted with TCP-1
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.6.2526-2534.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Type D Retrovirus Gag Polyprotein Interacts with
the Cytosolic Chaperonin TRiC
, a subunit of
the chaperonin TRiC (TCP-1 ring complex). TRiC is a cytosolic
chaperonin that is known to be involved in both folding and subunit
assembly of a variety of cellular proteins. TCP-1
also associated
with high specificity with the M-PMV pp24/16-p12 domain and human
immunodeficiency virus p6. Moreover, in cells, Gag polyprotein
associated with the TRiC chaperonin complex and this association
depended on ATP hydrolysis. In the p4 truncation mutants, the Gag-TRiC
association was significantly reduced. These results strongly suggest
that cytosolic chaperonin TRiC is involved in Gag folding and/or capsid
assembly. We propose that TRiC associates transiently with nascent
M-PMV Gag molecules to assist in their folding. Consequently, properly
folded Gag molecules carry out the intermolecular interactions involved
in self-assembly of the immature capsid.
*
Corresponding author. Present address: Laboratory of
Molecular Biology, NIMH, Building 36, Room 1D03, MSC 4034, Bethesda, MD
20892. Phone: (301) 402-1040. Fax: (301) 402-0245. E-mail: ssrhee{at}netscape.net.
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