Nucleic Acids Research, Vol 27, Issue 19 3844-3850, Copyright © 1999 by Oxford University Press
OA Sedelnikova, IG Panyutin, AN Luu and RD Neumann
We studied the stability of a DNA triplex resulting from the binding of a
38 nt long purine motif triplex-forming oligonucleotide (TFO) to a
covalently closed plasmid containing a target sequence from the human HPRT
gene. Our in vitro experiments showed that the triplex formed at plasmid
and TFO concentrations as low as 10(-9)M. Once formed, the triplex was
remarkably stable and could withstand 10 min incubation at 65 degrees C. We
next delivered these TFO-plasmid complexes into cultured human cells. To
monitor the TFO-plasmid complexes inside cells we applied a new technique
that we call 'radioprinting'. Because the TFO was(125)I labeled, we could
quantitatively monitor the triplexes by measuring(125)I-induced DNA strand
breaks in the target plasmid sequence. We found that the triplexes remain
stable inside the cells for at least 48 h. Based on these findings we
propose using TFO for indirect labeling of intact plasmid DNA. As a
demonstration, we show that the intracellular distribution of a
fluorescein-labeled TFO was different when it was liposome-delivered into
cultured human cells alone or in a complex with the plasmid. In the latter
case, the fluorescence was detected in nearly all the cells while detection
of the plasmid by use of a marker gene (beta-galactosidase) revealed
expression of the gene in only half of the cells.
ARTICLES
The stability of DNA triplexes inside cells as studied by iodine-125 radioprinting
Department of Nuclear Medicine, Warren G. Magnuson Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA.
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