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J. Virol., Sep 1997, 6315-6322, Vol 71, No. 9
Y Li, Z Zhang, JK Wakefield, SM Kang and CD Morrow
Sequence analysis of integrated proviruses of human immunodeficiency virus
type 1 (HIV-1) which utilize tRNA(His) to initiate reverse transcription
[virus derived from pHXB2(His-AC-TGT)] revealed five additional nucleotide
substitutions in the U5 and primer binding site (PBS) regions (ATGAC for
CCTGT at nucleotides 152, 160, 174, 181, and 200, respectively) (Z. Zhang
et al., Virology 226:306-317, 1996). We constructed a mutant proviral
genome [pHXB2(His-AC-GAC)] which contained the ATGAC substitutions to test
if they represented a necessary adaptation by the virus for use of
tRNA(His) to initiate reverse transcription. Viruses from pHXB2(His-AC-TGT)
and pHXB2(His-AC- GAC) were infectious. Sequence analysis of the U5 and PBS
regions of integrated provirus from a cell culture infected with virus
derived from pHXB2(His-AC-TGT) revealed a G-to-A change in CCTGT at
nucleotide 181 after limited in vitro culture, suggesting that this
nucleotide change represented an adaptation by the virus to efficiently
utilize tRNA(His) to initiate reverse transcription. To further address
this possibility, we used a specific mutation in reverse transcriptase
(RT), a methionine-to-valine change in the highly conserved YMDD amino acid
motif of HIV-1 RT (M184V), which has been shown in previous studies to
influence the fidelity and activity of the enzyme. The M184V RT mutation
was cloned into pHXB2(His-AC-GAC) and pHXB2(His-AC-TGT). Virus derived from
pHXB2(His-AC-GAC) with M184V RT had slightly delayed replication compared
to the virus from pHXB2(His-AC-GAC) with wild-type RT; in contrast, virus
from pHXB2(His-AC-TGT) with M184V RT was severely compromised in
replication. Using an endogenous reverse transcription-PCR assay to analyze
the reverse transcription of viruses obtained after transfection, we found
that viruses derived from pHXB2(His-AC-GAC) with the wildtype RT were
slightly faster in the initiation of reverse transcription than viruses
with M184V RT. The initiation of reverse transcription was delayed in
viruses derived from pHXB2(His-AC-TGT) with wild-type RT and M184V RT
compared to viruses derived from pHXB2(His-AC-GAC). Finally, sequence
analysis of U5 and PBS regions of proviruses from pHXB2(His-AC-GAC) with
wild-type RT revealed considerably more nucleotide substitutions than in
viruses derived from pHXB2(His-AC-GAC) containing the M184V mutation in RT
after extended in vitro culture. Our studies point to a role for these
additional nucleotide substitutions in U5 as an adaptation by the virus to
utilize an alternative tRNA to initiate reverse transcription.
Copyright © 1997, American Society for Microbiology
Nucleotide substitutions within U5 are critical for efficient reverse transcription of human immunodeficiency virus type 1 with a primer binding site complementary to tRNA(His)
Department of Microbiology, University of Alabama at Birmingham 35294, USA.
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