Effective strand invasion ODN incorporating a new bicyclic nucleoside analogue (WNA).

Efficient and specific targeting of DNA sequences by synthetic ligands is a major goal in chemical biology. Triplex-forming oligonucleotides (TFOs) are sequence-specific DNA-binding agents, but are limited to homopurine/homopyrimidine target sequences. We have previously reported two useful analogues (WNA: W-shaped nucleoside analogues), WNA-bT and WNAbC, which recognize a TA and a CG interrupting site forming triplexes with high stability and selectivity, respectively. However, their ability to form triplexes depended on their neighbouring bases in the TFO. Subsequent studies have shown that the sequence-dependency of the WNA analogues, for the formation of triplexes, has been partially solved by use of a WNA analogue bearing a substituted aromatic ring. Investigations into the effects of the substituted aromatic ring of WNA derivatives on the stability of triplexes led to the discovery of strand invasion by the TFO incorporating the new WNA analogue to form a highly stable duplex.