Human Retroviral Gene Expression and Cellular Transcription 
specific DNA-binding proteins with double- 
stranded phosphorothioate oligonucleotides, us- 
ing octamer or kB consensus sequences. These 
oligonucleotides bind specifically to the relevant 
transcription factor. Octamer-dependent activa- 
tion of a reporter plasmid, or NF-/cB-dependent 
activation of the HIV enhancer, can be appropri- 
ately inhibited when the relevant phosphor- 
othioate oligonucleotide is added to a transiently 
transfected cell line. 
Addition of octamer phosphorothioate oligonu- 
cleotides to Jurkat T leukemia cells inhibited se- 
cretion of interleukin-2 (IL-2) to a degree similar 
to that observed with a mutated octamer site in 
the IL-2 enhancer. Double-stranded phosphor- 
othioate oligonucleotides compete for the bind- 
ing of specific transcription factors and may there- 
fore provide antiviral, immunosuppressive, or 
other therapeutic effects. 
Expression of Cellular and Retroviral- 
Vector Genes In Vivo 
Transcription factors resembling NF-/cB also 
regulate the expression of normal cellular genes. 
Examination of a growth factor receptor for an- 
other immunologic protein, interleukin-2 (IL-2), 
revealed a site closely related to the regulatory /cB 
sites of HIV. We have shown that this site is recog- 
nized not only by NF-kB but by other proteins. We 
have cloned two genes encoding these proteins 
and have evaluated their role in the regulation of 
different cellular genes. We are also studying the 
activation of another coordinately expressed T 
cell gene, IL-2, by characterizing proteins that 
bind to expression-regulating control regions. In 
particular, we have identified binding proteins 
that recognize conserved regions by which IL-2 
gene expression is negatively regulated. 
Despite recent advances in the understanding 
of eukaryotic gene regulation, the site-specific 
expression of genes in vivo remains a major ob- 
stacle to the therapeutic management of human 
disease. Using our knowledge of retroviral gene 
expression, we have developed systems utilizing 
viral vectors to express biologically active pro- 
teins in cells and tissues. 
For example, we have recently devised a 
method that allows a recombinant gene to be ex- 
pressed efficiently at a specific site in vivo by 
direct introduction of genetic material at the time 
of catheterization. A recombinant /3-galactosidase 
gene was expressed in a specific arterial segment 
by direct infection with a retroviral vector or by 
DNA transfection using liposomes. Several cell 
types in the vessel wall were transduced with the 
recombinant gene, including endothelial and vas- 
cular smooth muscle cells. Following retroviral 
infection, a recombinant reporter gene was ex- 
pressed for at least five months, with no detect- 
able helper virus generated. Recombinant gene 
expression was limited to the site of infection and 
was absent from liver, lung, kidney, and spleen. 
Thus site-specific gene expression can be 
achieved by direct gene transfer in vivo, and 
could be applied to the treatment of such human 
diseases as atherosclerosis, cancer, or AIDS. Bio- 
logically active proteins are now being intro- 
duced into cells, including growth factors, 
growth inhibitors, or immune system proteins. 
The goal of this research is not only to understand 
basic mechanisms of gene regulation, transcrip- 
tional activation, and viral gene expression, but 
also to define the biological significance of fac- 
tors that regulate gene expression in complex 
organisms. 
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