The striking and ubiquitous in vitro affinity between hemin and DNA/RNA G-quadruplexes raises the intriguing possibility of its relevance to biology. To date, no satisfactory experimental framework has been reported for investigating such a possibility. Complexation by G-quadruplexes leads to activation of the bound hemin toward catalysis of 1- and 2-electron oxidative reactions, with phenolic compounds being particularly outstanding substrates. We report here a strategy for exploiting that intrinsic peroxidase activity of hemin•G-quadruplex complexes for self-biotinylation of their G-quadruplex component. Such self-biotinylation occurs with good efficiency and high discrimination in vitro, being specific for G-quadruplexes and not for duplexes. The biotinylated DNA, moreover, remains amenable to polymerase chain reaction amplification, rendering it suitable for analysis by ChIP-Seq and related methods. We anticipate that this self-biotinylation methodology will also serve as a sensitive tool, orthogonal to existing ones, for identifying, labeling and pulling down cellular RNA and DNA G-quadruplexes in general, as well as proteins bound to or proximal to such quadruplexes
