In this latest OBC article, Jesper Wengel and colleagues at the University of Southern Denmark, describe modified locked nucleic acids (LNA) which form highly stable triplexes with double stranded DNA.

There has been a significant amount of recent research into the therapeutic capability of anti-gene technology, where triplex-forming compounds have the ability to modify gene expression by binding to double-stranded DNA (dsDNA). An approach to this is to use triplex-forming oligonucleotides (TFOs) to bind sequence-specifically to dsDNA in the major groove. However, the formation and stability of triplexes in physiological conditions is difficult as the TFOs need to be protonated to bind. 

Many strategies have been developed to overcome this problem. One method, 'dual recognition', links part of the nucleotide monomer to one or more amines that can be protonated under physiological conditions, and another method uses conformationally locked nucleic acids (LNA), which have been shown to increase triplex stability. Wengel and colleagues have successfully combined these two effects using modified 2'-amino-LNA monomers. 

Wengel found that triplex formation was actually destabilised by 2'-amino-LNA monomers in comparison to simple LNA monomers. However, functionalisation with a glycyl unit of the 2'-amino-LNA led to a significant increase in triplex stability. 

Wengel hopes that additional structural and biophysical studies will further improve the design and performance of TFOs. 

Richard Kelly