Targeting Human Telomeric Higher-Order DNA: Dimeric G-Quadruplex Units Serve as Preferred Binding Site

Long human telomeric fragments can form stable, higher-order G-quadruplex structures, recently identified in human cells, which are potential drug targets. However, there are very few examples of ligand binding to higher-order G-quadruplexes, and all the reported ligands are proposed to bind at the cleft between two G-quadruplexes. Here we report that zinc-finger-like chiral supramolecular complexes prefer binding to higher-order G-quadruplexes over a single G-quadruplex, with similar to 200-fold higher selectivity. To our knowledge, this is the first example of a ligand that can distinguish higher-order G-quadruplexes from a single G-quadruplex with such high selectivity. Further studies indicate that the nanosized chiral complex would bind to two well-matched G-quadruplex units, instead of binding at the cleft between the two G-quadruplexes. These results provide new insights into the targeting of higher-order G-quadruplex ligands. Our work illustrates that dimeric G-quadruplex units can be ligand-preferred binding sites.