Development of novel artificial nucleosides for expansion of triplex-recognition codes

Triplex-forming oligonucleotides (TFOs) are potential DNA-targeting molecules, and would become powerful tools for genomic research. However, the problem that the stable triplexes form only with homopurine: homopyrimidine sequences has not been generally solved in spite of extensive studies. In this study we have developed new base analogs (WNA) constructed of three parts, a benzene ring, a heterocyclic ring, and a bicyclic skeleton to hold these two parts. Among a number of WNA analogs, we have determined two useful WNA analogs, WNA-βT and WNA-βC, for selective stabilization of triplexes at a TA and a CG interrupting site with higher stability than the natural-type triplexes, respectively. The results of this study will provide useful information for the design of new WNA analogs to overcome inherent problems for further expansion of triplex recognition codes.