Synthesis of and triplex formation in oligonucleotides containing 2′-deoxy-6-thioxanthosine.

This study aimed to synthesize triplex-forming oligonucleotides (TFOs) containing 2′-deoxy-6-thioxanthosine (s 6 X) and 2′-deoxy-6-thioguanosine (s 6 Gs) residues and examined their triplex-forming ability. Consecutive arrangement of s 6 X and s 6 Gs residues increased the triplex-forming ability of the oligonucleotides more than 50 times, compared with the unmodified TFOs. Moreover, the stability of triplex containing a mismatched pair was much lower than that of the full-matched triplex, though s 6 X could form a s 6 X-GC mismatched pair via tautomerization of s 6 X. The present results reveal excellent properties of modified TFOs containing s 6 Xs and s 6 Gs residues, which may be harnessed in gene therapy and DNA nanotechnology. [ABSTRACT FROM AUTHOR]