Visna virus encodes a post-transcriptional regulator of viral structural gene expression.
Visna virus is an ungulate lentivirus that is distantly related to the primate lentiviruses, including human immunodeficiency virus type 1 (HIV-1). Replication of HIV-1 and of other complex primate retroviruses, including human T-cell leukemia virus type I (HTLV-I), requires the expression in trans of a virally encoded post-transcriptional activator of viral structural gene expression termed Rev (HIV-1) or Rex (HTLV-I). We demonstrate that the previously defined L open reading frame of visna virus encodes a protein, here termed Rev-V, that is required for the cytoplasmic expression of the incompletely spliced RNA that encodes the viral envelope protein. Transactivation by Rev-V was shown to require a cis-acting target sequence that coincides with a predicted RNA secondary structure located within the visna virus env gene. However, Rev-V was unable to function by using the structurally similar RNA target sequences previously defined for Rev or Rex and, therefore, displays a distinct sequence specificity. Remarkably, substitution of this visna virus target sequence in place of the HIV-1 Rev response element permitted the Rev-V protein to efficiently rescue the expression of HIV-1 structural proteins, including Gag, from a Rev- proviral clone. These results suggest that the post-transcriptional regulation of viral structural gene expression may be a characteristic feature of complex retroviruses.
Tiley
L S
LS
Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710.
Brown
P H
PH
Le
S Y
SY
Maizel
J V
JV
Clements
J E
JE
Cullen
B R
BR
D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D015967:Gene Expression Regulation, Viral; D015694:Gene Products, rev / Q000235:genetics*; D016370:Gene Products, rex / Q000235:genetics*; D005814:Genes, Viral; D005822:Genetic Vectors; D015497:HIV-1 / Q000235:genetics*; D015368:Human T-lymphotropic virus 1 / Q000235:genetics*; D009710:Nucleotide Mapping; D016366:Open Reading Frames; D014162:Transfection; D014759:Viral Envelope Proteins / Q000235:genetics / Q000302:isolation & purification; D015678:Viral Structural Proteins / Q000235:genetics*; D014790:Visna-maedi virus / Q000235:genetics*; D054321:rev Gene Products, Human Immunodeficiency Virus
D015694:Gene Products, rev; D016370:Gene Products, rex; D014759:Viral Envelope Proteins; D015678:Viral Structural Proteins; D054321:rev Gene Products, Human Immunodeficiency Virus