DNA secondary structures: stability and function of G-quadruplex structures

Growing evidence is implicating non‑B-form DNA structures in processes related to DNA stability and function, including replication and transcription. In particular, genomic studies are suggesting that sequences that could form G-quadruplex structures are widespread, so there is a need to improve our understanding of these structures. In addition to the canonical double helix, DNA can fold into various other inter- and intramolecular secondary structures. Although many such structures were long thought to be in vitro artefacts, bioinformatics demonstrates that DNA sequences capable of forming these structures are conserved throughout evolution, suggesting the existence of non-B-form DNA in vivo. In addition, genes whose products promote formation or resolution of these structures are found in diverse organisms, and a growing body of work suggests that the resolution of DNA secondary structures is critical for genome integrity. This Review focuses on emerging evidence relating to the characteristics of G-quadruplex structures and the possible influence of such structures on genomic stability and cellular processes, such as transcription.