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Journal of Virology, November 2001, p. 10543-10549, Vol. 75, No. 21
McGill AIDS Centre, Lady Davis Institute for
Medical Research, Jewish General Hospital,1 and
Departments of Medicine2 and
Microbiology and Immunology,3 McGill
University, Montreal, Quebec, Canada
Received 13 March 2001/Accepted 20 July 2001
Stem-loop B is a 12-nucleotide [nt]-long completely conserved
sequence postulated to form a 4-bp stem and a 4-nt internal loop under
the kissing-loop hairpin (klh) (nt 248 to 270) of human immunodeficiency virus type 1 (HIV-1) genomic RNA. We investigated its
role in viral replication, genomic RNA dimerization, and dimerization of partial HIV-1 RNA transcripts. The putative CUCG246-CGAG277 duplex was replaced by nine alternative complementary sequences, five
likely to base pair only in short RNAs and four likely to base pair in
long (~500-nt) RNAs, as assessed by the algorithm mfold. Among the
five former sequences, none preserved genome dimerization and all
reduced viral replication by 98 to 99.9%. Among the four latter
sequences, three (MB6, -9, and -10) preserved genome dimerization, one
(MB7) did not significantly inhibit it, and two (MB9 and -10) preserved
viral replication. We conclude that duplex formation by stem B
nucleotides is necessary for viral infectivity and complete genome
dimerization. Deleting the 5' or 3' side of loop B or of stem B had
little impact on dimerization of partial RNA transcript and no impact
on klh folding (and, for loop B mutations, on stem B folding), but each
deletion inhibited genome dimerization almost as much as klh
destruction. This suggests that loop B is required for complete genome
dimerization and that loop B and stem B stimulate dimerization only in
very long RNAs and/or in the presence of unidentified viral and
cellular factors. Finally, we asked if nine deletions or
nucleotide substitutions within nt 200 to 242 and/or nt 282 to
335 could influence genome dimerization. These mutations had
intermediate inhibitory impacts consistent with their predicted
influence on stem B, loop B, and klh formation. Two exceptions were
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.21.10543-10549.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Role of Stem B, Loop B, and Nucleotides next to the
Primer Binding Site and the Kissing-Loop Domain in Human
Immunodeficiency Virus Type 1 Replication and Genomic-RNA
Dimerization
200-226 and
236-242 genomic RNAs, which dimerized
relatively poorly despite having neutral or positive influences on stem
B, loop B, and klh folding.
*
Corresponding author. Mailing address: Lady Davis
Institute for Medical Research, 3755 Cote Ste. Catherine Rd., Montreal, Quebec, Canada H3T 1E2. Phone: (514) 340-8260. Fax: (514) 340-7502. E-mail: mi.laughrea{at}mcgill.ca or
laughrea{at}hotmail.com.
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