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Journal of Virology, September 2000, p. 8732-8739, Vol. 74, No. 18
UNC Gene Therapy
Center,1 Neuroscience
Center,3 Curriculum in
Neurobiology,2 and Departments of
Psychiatry4 and
Pharmacology,5 University of North
Carolina, Chapel Hill, North Carolina 27599
Received 7 March 2000/Accepted 3 June 2000
Adeno-associated virus (AAV) type 2 vectors transfer stable,
long-term gene expression to diverse cell types in vivo. Many gene
therapy applications require the control of long-term transgene expression, and AAV vectors, similar to other gene transfer systems, are being evaluated for delivery of regulated gene expression cassettes. Previously, we (R. P. Haberman, T. J. McCown, and
R. J. Samulski, Gene Ther. 5:1604-1611, 1998) demonstrated the
use of the tetracycline-responsive system for long-term regulated expression in rat brains. In that study, we also observed residual expression in the "off" state both in vitro and in vivo, suggesting that the human cytomegalovirus (CMV) major immediate-early minimal promoter or other cis-acting elements (AAV terminal repeats
[TR]) were contributing to this activity. In the present study, we
identify that the AAV TR, minus the tetracycline-responsive minimal CMV promoter, will initiate mRNA expression from vector templates. Using
deletion analysis and specific PCR-derived TR reporter gene templates,
we mapped this activity to a 37-nucleotide stretch in the
A/D elements of the TR. Although the mRNA derived from the
TR is generated from a non-TATA box element, the use of mutant templates failed to identify function of canonical initiator sequences as previously described. Finally, we demonstrated the presence of green
fluorescent protein expression both in vitro and in vivo in brain by
using recombinant virus carrying only the TR element. Since the AAV
terminal repeat is a necessary component of all recombinant AAV
vectors, this TR transcriptional activity may interfere with all
regulated expression cassettes and may be a problem in the development
of novel TR split gene vectors currently being considered for genes too
large to be packaged.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Novel Transcriptional Regulatory Signals in the Adeno-Associated
Virus Terminal Repeat A/D Junction Element
*
Corresponding author. Mailing address: CB 7352, 7119 Thurston Bowles, UNC Gene Therapy Center, University of North Carolina, Chapel Hill, NC 27599. Phone: (919) 962-3285. Fax: (919) 966-0907. E-mail: rjs{at}med.unc.edu.
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