1 research outputs found
Simian Immunodeficiency Virus in Which <i>nef</i> and U3 Sequences Do Not Overlap Replicates Efficiently In Vitro and In Vivo in Rhesus Macaques
No full textABSTRACT
The
nef
genes of human immunodeficiency virus and simian immunodeficiency virus (SIV) overlap about 80% of the U3 region of the 3′ long terminal repeat (LTR) and contain several essential
cis
-acting elements (here referred to as the TPI region): a T-rich region, the polypurine tract, and attachment (
att
) sequences required for integration. We inactivated the TPI region in the
nef
reading frame of the pathogenic SIVmac239 clone (239wt) by 13 silent point mutations. To restore viral infectivity, intact
cis
-regulatory elements were inserted just downstream of the mutated
nef
gene. The resulting SIV genome contains U3 regions that are 384 bp shorter than the 517-bp 239wt U3 region. Overall, elimination of the duplicated Nef coding sequences truncates the proviral genome by 350 bp. Nonetheless, it contains all known coding sequences and
cis
-acting elements. The TPI mutant virus expressed functional Nef and replicated like 239wt in all cell culture assays and in vivo in rhesus macaques. Notably, these SIVmac constructs allow us to study Nef function in the context of replication-competent viruses without the restrictions of overlapping LTR sequences and important
cis
-acting elements. The genomes of all known primate lentiviruses contain a large overlap between
nef
and the U3 region. We demonstrate that this conserved genomic organization is not obligatory for efficient viral replication and pathogenicity.
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