The G-Triplex DNA

In summary, during the folding process of the G-quadruplex aptamer TBA, we have observed the formation of the G-triplex structural motif. The existence of this structure has been proven in an 11-mer oligonucleotide, whose structural and thermodynamic properties have been characterized. At variance with the already known triplex structures, the G-triplex presents G:G:G triad planes stabilized by an array of Hoogsteen-like hydrogen bonds. Although this kind of structure was already hypothesized as an intermediate in the folding process of other quadruplex forming sequences,11 this is the first time that DNA has been unambiguously isolated and structurally characterized in this conformation. G-rich regions, potentially able to form G-triplex structures, are very abundant in the genome and our study paves the way for further investigations into the presence of these structures in vivo, their biological role, and ways of interacting with them.