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J. Virol., 11 1997, 8542-8551, Vol 71, No. 11
MP Wentz, BE Moore, MW Cloyd, SM Berget and LA Donehower
We have isolated a naturally arising human immunodeficiency type 1 (HIV- 1)
mutant containing a point mutation within the env gene. The point mutation
resulted in complete loss of balanced splicing, with dominant production of
aberrant mRNAs. The aberrant RNAs arose via activation of normally cryptic
splice sites flanking the mutation within the env terminal exon to create
exon 6D, which was subsequently incorporated in aberrant env, tat, rev, and
nef mRNAs. Aberrant multiply spliced messages contributed to reduced virus
replication as a result of a reduction in wild-type Rev protein. The point
mutation within exon 6D activated exon 6D inclusion when the exon and its
flanking splice sites were transferred to a heterologous minigene.
Introduction of the point mutation into an otherwise wild-type HIV-1
proviral clone resulted in virus that was severely inhibited for
replication in T cells and displayed elevated usage of exon 6D. Exon 6D
contains a bipartite element similar to that seen in tat exon 3 of HIV-1,
consisting of a potential exon splicing silencer (ESS) juxtaposed to a
purine-rich sequence similar to known exon splicing enhancers. In the
absence of a flanking 5' splice site, the point mutation within the exon 6D
ESS-like element strongly activated env splicing, suggesting that the
putative ESS plays a natural role in limiting the level of env splicing. We
propose, therefore, that exon silencers may be a common element in the
HIV-1 genome used to create balanced splicing of multiple products from a
single precursor RNA.
Copyright © 1997, American Society for Microbiology
A naturally arising mutation of a potential silencer of exon splicing in human immunodeficiency virus type 1 induces dominant aberrant splicing and arrests virus production
Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030, USA.
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