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J. Virol., Aug 1997, 6003-6010, Vol 71, No. 8
X Li, C Liang, Y Quan, R Chandok, M Laughrea, MA Parniak, L Kleiman and MA Wainberg
Reverse transcription of retroviruses is initiated from an 18- nucleotide
(nt) primer binding site (PBS), located within the 5' region of viral
genomic RNA, to which the host cell-derived tRNA primer is annealed and
also involves viral genomic sequences outside the PBS. We constructed
proviral DNA clones of human immunodeficiency virus (HIV) that had
selective deletions of either a 7-nt segment found immediately downstream
of the PBS or an extended nontranslated 54-nt stretch located immediately
downstream of the PBS and containing the aforementioned 7-nt segment.
Synthesis of minus-strand strong-stop DNA was assessed with MT-4 cells
infected with viruses derived from COS-7 cells that had been transfected
with these various constructs. We found that similar levels of minus-strand
strong-stop DNA as well as DNA produced after template switching were
expressed in MT-4 cells infected with COS-7-derived wild-type viruses or
with viruses that had the 7-nt segment deleted. In contrast, significantly
lower levels of viral DNA were detected in MT-4 cells after infection with
viruses that had deletions of the 54-nt stretch. Furthermore, the molecular
clone containing the 7-nt deletion was able to replicate with wild-type
kinetics, while that containing the 54-nt deletion displayed a
significantly diminished capacity in this regard. Further deletion analysis
showed that a 16-nt segment at the 3' end of this 54-nt segment was largely
responsible for these effects. We also conducted studies to determine
levels of viral mRNA in COS-7 cells that had been transfected with
equivalent amounts of DNA derived from either a wild- type HIV construct or
our various deletion mutants. In the case of transfections performed with
the 7-nt deletion mutant and wild-type HIV DNA, high levels of viral mRNA
transcripts were detected, which was not the case for the 54 nt-deletion
mutant. However, these various mRNAs possessed similar stabilities, as
shown through studies in which transcript formation was arrested by
treatment of cells with actinomycin D. Thus, the 54-nt segment of 5'
nontranslated RNA, located downstream of the PBS, is involved in efficient
expression of each of viral DNA, mRNA, and infectious virus.
Copyright © 1997, American Society for Microbiology
Identification of sequences downstream of the primer binding site that are important for efficient replication of human immunodeficiency virus type 1
McGill University AIDS Centre, Jewish General Hospital, and Department of Medicine, McGill University, Montreal, Quebec, Canada.
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