The interaction between the single-stranded DNA and the homologous duplex DNA is essential for DNA homologous repair. Here, we report that parallel triplex structure can form spontaneously between a mechanically extended ssDNA and a homologous dsDNA in protein-free condition. The triplex has a contour length close to that of a B-form DNA duplex and remains stable after force is released. The bi...

While sequence-selective dsDNA targeting by triplex forming oligonucleotides has been studied extensively, only very little is known about the properties of PNA-dsDNA triplexes--mainly due to the competing invasion process. Here we show that when appropriately modified using pseudoisocytosine substitution, in combination with (oligo)lysine or 9-aminoacridine conjugation, homopyrimidine PNA olig...

Triplex-forming oligonucleotides (TFOs) are generally designed to inhibit transcription or DNA replication but can be used for more diverse purposes. Here we have designed a hairpin-TFO able to recruit transcription factors to a target DNA. The designed oligonucleotide contains a triplex-forming sequence, linked through a nucleotide loop to a double-stranded hairpin including the SRE enhancer o...

We have used DNase I footprinting to examine the interaction of several triplex-binding ligands with antiparallel TG- and AG-containing triplexes. We find that although a 17mer TG-containing oligonucleotide on its own fails to produce a footprint at concentrations as high as 30 microM, this interaction can be stabilised by several ligands. Within a series of disubstituted amidoanthraquinones we...

Triplex-forming oligonucleotides (TFOs) can bind to polypurine/polypyrimidine regions in DNA in a sequence-specific manner. The specificity of this binding raises the possibility of using triplex formation for directed genome modification, with the ultimate goal of repairing genetic defects in human cells. Several studies have demonstrated that treatment of mammalian cells with TFOs can provoke...

PCR primers corresponding to the adhesin genes of Mycoplasma pneumoniae and Mycoplasma genitalium were shown to detect the corresponding organisms specifically. Absence of cross-reaction with seven other mollicute species and six unrelated bacterial species commonly found in humans was demonstrated. Positive control primers directed against human mitochondrial DNA could be mixed with the Mycopl...

Oligodeoxynucleotide (ODN) conjugates with the polylysine comb-type copolymer having an ability to promote and stabilize duplex and triplex DNA formation were prepared. 5'-Aminated ODN was succinylated with succinic anhydride. The resulting ODNs having carboxyl terminus were coupled with epsilon-amino groups of the comb-type copolymer using water soluble carbodiimide. The conjugate free from un...

Homo-purine (d-TGAGGAAAGAAGGT) and homo-pyrimidine (d-CTCCTTTCTTCC) oligomers have been designed such that they are complementary in parallel orientation. When mixed in a 1:1 molar ratio, the system adopts an antiparallel duplex at neutral pH with three mismatched base pairs. On lowering the pH below 5.5, a new complex is formed. The NMR results show the coexistence of a intermolecular pyrimidi...