greater resolution to 4q23 and 10q24, respectively. 
These results demonstrate that these members of the 
NF-kB family are unlinked. Interestingly, p49/ 
pi 00, as well as pi 05, maps to regions associated 
with certain types of acute lymphoblastic leukemia. 
Transcriptional activation of the IL-2Ra gene in T 
cells is dependent on a regulatory element that can 
bind NF-/cB but which differs in sequence and function 
from the kB site of the immunoglobulin (Ig) en- 
hancer. To define the molecular basis of gene -specific 
regulation by this variant kB site, the laboratory has 
used electrophoretic mobility shift assays to character- 
ize a novel gene product, designated RkB, that binds 
preferentially to the related kB site in IL-2Ra. A cDNA 
encoding this 107-kDa protein has been isolated from 
a Agtl 1 expression library by screening with a probe 
containing the IL-2Ra kB site. 
R/cB is a tissue-specific transcription factor con- 
taining an amino acid sequence similar to a discrete 
region of the myogenic regulatory protein MyoD, 
but is unrelated to other DNA-binding proteins, in- 
cluding those belonging to the rel/ dorsal gene fam- 
ily. This novel /cB-binding protein may therefore con- 
tribute to the regulation of distinct cellular and viral 
genes with variant kB sites. Grants from the National 
Institutes of Health provided partial support for the 
projects described above. 
Gene Transfer in Vivo 
In addition to studies of gene regulation, gene 
transfer techniques have been used to deliver recom- 
binant genes to specific sites in vivo. Previously, 
endothelial or vascular smooth muscle cells were 
transduced with recombinant genes in vitro and in- 
troduced stably on porcine arteries in vivo after de- 
livery with a catheter. More recently, a recombinant 
/3-galactosidase gene was expressed in a specific arte- 
rial segment in vivo by direct infection with a mu- 
rine amphotropic retroviral vector or by DNA trans- 
fection with the use of liposomes. Several cell types 
in the vessel wall were transduced, including endo- 
thelial and vascular smooth muscle cells for at least 
five months, and no helper virus was detected. 
Autoimmune vasculitis represents a disease char- 
acterized by focal inflammation within arteries at 
multiple sites in the vasculature. Therapeutic inter- 
ventions in this disease are empirical and often un- 
successful, and the mechanisms of immune injury 
are not well defined. The direct transfer of recombi- 
nant genes and their expression in the anerial wall 
provides an opportunity to explore the pathogene- 
sis and treatment of vascular disease. 
An animal model for vasculitis has been devel- 
oped, using these direct gene transfer approaches. 
Inflammation has been elicited by introduction of a 
foreign class I major histocompatibility complex 
(MHC) gene, HLA-B7, to specific sites in porcine 
arteries. Transfer and expression of this recombi- 
nant gene was confirmed by polymerase chain reac- 
tion (PGR) analysis and immunohistochemistry, and 
cytolytic T cells specific for HLA-BJwere detected. 
These findings demonstrated that expression of a re- 
combinant gene in the vessel wall can induce a focal 
immune response and suggest that vessel damage 
induced by cell-mediated immune injury can initi- 
ate vasculitis. 
The safety and toxicity of this method of gene de- 
livery have been assessed after in vivo administra- 
tion, either by intravenous or direct intratumor in- 
jection. Nine to eleven days after intravenous 
injection, DNA was found primarily in heart and 
lung tissue by PGR analysis. No abnormalities were 
evident from histologic examination of tissue, exam- 
ination of tissue-specific serum enzymes, routine 
biochemical parameters, or electrocardiographic 
monitoring. DNA-liposome complexes can there- 
fore be used for the delivery of recombinant genes 
in vivo with minimal toxicity. (These studies have 
been supported in part by grants from the National 
Institutes of Health.) 
Taken together, these results have demonstrated 
that site-specific gene expression can be achieved 
by cell-mediated and direct gene transfer in vivo 
and could be applied to the treatment of such hu- 
man diseases as atherosclerosis or cancer. 
Dr. Nabel is also Associate Professor of Internal 
Medicine and Biological Chemistry and a member 
of the Cell and Molecular Biology Department at 
the University of Michigan Medical School. 
Articles 
Adams, B.S., Leung, K., Hanley, E.W., and Nabel, 
G.J. 1991. Gloning of R/cB, a novel DNA-binding 
protein that recognizes the interleukin-2 receptor 
a chain kB site. New Biol 3:1063-1073- 
Butera, S T., Perez, V.L., Wu, B.-Y., Nabel, G.J., and 
Folks, T.M. 1991. Oscillation of the human immu- 
nodeficiency virus surface receptor is regulated 
by the state of viral activation in a GD4^ cell 
model of chronic infection. / Virol 65:4645- 
4653. 
Eck, S.L., and Nabel, G.J. 1992. Antisense oligonu- 
cleotides for therapeutic intervention. Curr Opin 
Biotechnol 2:897-904. 
Griffin, G.E., Leung, K., Folks, T.M., Kunkel, S., and 
Nabel, G.J. 1991. Induction of NF-kB during 
monocyte differentiation is associated with acti- 
vation of HIV gene expression. Res Virol 
142:233-238. 
GENETICS 229 
