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Journal of Virology, March 1999, p. 2309-2320, Vol. 73, No. 3
Department of Microbiology and
Immunology,1 and
Department of
Medicine,2 Pennsylvania State University
College of Medicine, Hershey, Pennsylvania 17033, and
Department of Molecular Virology, Pasteur Merieux-Connaught
Canada, North York, Ontario M2R 3T4, Canada3
Received 6 July 1998/Accepted 13 November 1998
Retroviral Gag proteins, in the absence of any other viral
products, induce budding and release of spherical, virus-like particles from the plasma membrane. Gag-produced particles, like those of authentic retrovirions, are not uniform in diameter but nevertheless fall within a fairly narrow distribution of sizes. For the human immunodeficiency virus type 1 (HIV-1) Gag protein, we recently reported
that elements important for controlling particle size are contained
within the C-terminal region of Gag, especially within the p6
sequence (L. Garnier, L. Ratner, B. Rovinski, S.-X. Cao, and J. W. Wills, J. Virol. 72:4667-4677, 1998). Deletions and substitutions
throughout this sequence result in the release of very large particles.
Because the size determinant could not be mapped to any one of the
previously defined functions within p6, it seemed likely that its
activity requires the overall proper folding of this region of Gag.
This left open the possibility of the size determinant residing in a
subdomain of p6, and in this study, we examined whether the late domain
(the region of Gag that is critical for the virus-cell separation step)
is involved in controlling particle size. We found that particles of
normal size are produced when p6 is replaced with the totally unrelated late domain sequences from Rous sarcoma virus (contained in its p2b
sequence) or equine infectious anemia virus (contained in p9). In
addition, we found that the large particles released in the absence of
p6 require the entire CA and adjacent spacer peptide sequences, whereas
these internal sequences of HIV-1 Gag are not needed for budding (or
proper size) when a late domain is present. Thus, it appears the
requirements for budding are very different in the presence and absence
of p6.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Identification of Retroviral Late Domains as
Determinants of Particle Size
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Pennsylvania State University College of Medicine, 500 University Dr., P.O. Box 850, Hershey, PA 17033. Phone:
(717) 531-3528. Fax: (717) 531-6522. E-mail: jwills{at}psu.edu.
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