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Journal of Virology, October 2000, p. 8854-8860, Vol. 74, No. 19
McGill University AIDS Centre, Lady Davis
Institute-Jewish General Hospital, Montreal, Quebec, Canada H3T
1E2,1 and Department of Microbiology and
Immunology, McGill University, Montreal, Quebec Canada H3A
2B42
Received 2 March 2000/Accepted 6 July 2000
Simian immunodeficiency virus (SIV) infection of macaques is
remarkably similar to that of human immunodeficiency virus type 1 (HIV-1) in humans, and the SIV-macaque system is a good model for AIDS
research. We have constructed an SIV proviral DNA clone that is deleted
of 97 nucleotides (nt), i.e., construct SD, at positions (+322 to +418)
immediately downstream of the primer binding site (PBS) of SIVmac239.
When this construct was transfected into COS-7 cells, the resultant
viral progeny were severely impaired with regard to their ability to
replicate in C8166 cells. Further deletion analysis showed that a virus
termed SD1, containing a deletion of 23 nt (+322 to +344), was able to
replicate with wild-type kinetics, while viruses containing deletions
of 21 nt (+398 to +418) (construct SD2) or 53 nt (+345 to +397)
(construct SD3) displayed diminished capacity in this regard. Both the
SD2 and SD3 viruses were also impaired with regard to ability to
package viral RNA, while SD1 viruses were not. The SD and SD3
constructs did not revert to increased replication ability in C8166
cells over 6 months in culture. In contrast, long-term passage of the SD2 mutated virus resulted in a restoration of replication capacity, due to the appearance of four separate point mutations. Two of these
substitutions were located in leader sequences of viral RNA within the
PBS and the dimerization initiation site (DIS), while the other two
were located within two distinct Gag proteins, i.e., CA and p6. The
biological relevance of three of these point mutations was confirmed by
site-directed mutagenesis studies that showed that SD2 viruses
containing each of these substitutions had regained a significant
degree of viral replication capacity. Thus, leader sequences downstream
of the PBS, especially the U5-leader stem and the DIS stem-loop, are
important for SIV replication and for packaging of the viral genome.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Leader Sequences Downstream of the Primer Binding
Site Are Important for Efficient Replication of Simian
Immunodeficiency Virus
*
Corresponding author. Mailing address: McGill AIDS
Centre, Lady Davis Institute-Jewish General Hospital, 3755 Cote
Ste-Catherine Rd., Montreal, Québec, Canada H3T 1E2. Phone: (514)
340-8260. Fax: (514) 340-7537. E-mail:
mwainb1{at}po-box.mcgill.ca.
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