No. Bukanov et al., PD-LOOP - A COMPLEX OF DUPLEX DNA WITH AN OLIGONUCLEOTIDE, Proceedings of the National Academy of Sciences of the United Statesof America, 95(10), 1998, pp. 5516-5520
A stable complex between duplex DNA and an oligonucleotide is assemble
d with the aid of a DNA synthetic mimic, peptide nucleic acid (PNA). H
omopyrimidine PNAs are known to invade into short homopurine tracts in
duplex DNA forming P-loops, We have found that P-loops, formed at two
closely located purine tracts in the same DNA strand separated by a m
ixed purine-pyrimidine sequence, merge and open the double helix betwe
en them, The opposite DNA strand, which is not bound with PNA, exposes
and becomes accessible for complexing with an oligonucleotide via Wat
son-Crick pairing. As a result, the PD-loop emerges, which consists of
locally open duplex DNA, PNA ''openers,'' and an oligonucleotide, The
PD-loop stability and sequence specificity are demonstrated by affini
ty capture of duplex DNAs by using biotinylated oligonucleotides and s
treptavidin-covered magnetic beads. The type of complex formed by PNAs
, an oligonucleotide and duplex DNA we describe, opens ways for develo
pment of various in vitro and in situ hybridization techniques with du
plex DNA and may find applications in DNA nanotechnology and genomics.