The i-motif is a high-order DNA structure formed by hemiprotonated cytosine-cytosine base pairs under acidic conditions. It is less well studied than other high-order DNA structures, such as G-quadruplexes. However, increasing numbers of i-motif-binding ligands are being reported, and they are being used as tools to investigate the i-motif's structure and biological functions. It has become clear that the i-motif has a functional role in the regulation of gene expression. In this review, we provide an overview of i-motif ligands so far reported, and we summarize their effects on the structure and their use as tools to investigate its biological functions.
Keywords: DNA application; DNA high-order structure; i-motif; interacting agent; ligand.