DNA triple-helix formation: an approach to artificial gene repressors?

Certain sequences of double-helical DNA can be recognized and tightly bound by oligonucleotides. The effects of such triple-helical structures on DNA binding proteins have been studied. Stabilities of DNA triple-helices at or near physiological conditions are sufficient to inhibit DNA binding proteins directed to overlapping sites. Such proteins include restriction endonucleases, methylases, transcription factors, and RNA polymerases. These and other results suggest that oligonucleotide-directed triple-helix formation could provide the basis for designing artificial gene repressors. The general question of whether biological systems employ RNA molecules for recognition and regulation of double-helical DNA is discussed.