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J Virol, March 1998, p. 1983-1993, Vol. 72, No. 3
Department of Medicine, Children's Hospital,
and Department of Pediatrics, Harvard Medical School, Boston,
Massachusetts 02115
Received 19 September 1997/Accepted 14 November 1997
The nucleocapsid protein (NC) of retroviruses plays a major role in
genomic RNA packaging, and some evidence has implicated the matrix
protein (MA) of certain retroviruses in viral RNA binding. To further
investigate the role of NC in the selective recognition of genomic
viral RNA and to address the potential contribution of MA in this
process, we constructed chimeric and deletion human immunodeficiency
virus type 1 (HIV-1) mutants that alter the NC or MA protein. Both HIV
and mouse mammary tumor virus (MMTV) NC proteins have two zinc-binding
domains and similar basic amino acid compositions but differ
substantially in total length, amino acid sequence, and spacing of the
zinc-binding motifs. When the entire NC coding sequence of HIV was
replaced with the MMTV NC coding sequence, we found that the HIV genome
was incorporated into virions at 50% of wild-type levels. Viruses
produced from chimeric HIV genomes with complete NC replacements, or
with the two NC zinc-binding domains replaced with MMTV sequences,
preferentially incorporated HIV genomes when both HIV and MMTV genomes
were simultaneously present in the cell. Viruses produced from chimeric
MMTV genomes in which the MMTV NC had been replaced with HIV NC
preferentially incorporated MMTV genomes when both HIV and MMTV genomes
were simultaneously present in the cell. In contrast, viruses produced from chimeric HIV genomes containing the Moloney NC, which contains a
single zinc-binding motif, were previously shown to preferentially incorporate Moloney genomic RNA. Taken together, these results indicate
that an NC protein with two zinc-binding motifs is required for
specific HIV RNA packaging and that the amino acid context of these
motifs, while contributing to the process, is less crucial for
specificity. The data also suggest that HIV NC may not be the exclusive
determinant of RNA selectivity. Analysis of an HIV MA mutant revealed
that specific RNA packaging does not require MA protein.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Nucleocapsid and Matrix Protein Contributions to
Selective Human Immunodeficiency Virus Type 1 Genomic RNA
Packaging
*
Corresponding author. Mailing address: Children's
Hospital, Enders 609, 300 Longwood Ave., Boston, MA 02115. Phone: (617) 355-8426. Fax: (617) 355-8387. E-mail address:
aldovini{at}A1.tch.harvard.edu
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