G-quadruplex unwinding helicases and their function in vivo.

The concept that G-quadruplex (G4) structures can form within DNA or RNA in vitro has been long known and extensively discussed. In recent years, accumulating evidences imply that G-quadruplex structures form in vivo Initially, inefficient regulation of G-quadruplex structures was mainly associated with genome instability. However, due to the location of G-quadruplex motifs and their evolutionary conservation, different cellular functions of these structures have been postulated (e.g. in telomere maintenance, DNA replication, transcription, and translation). Regardless of their function, efficient and controlled formation and unwinding are very important, because 'mis'-regulated G-quadruplex structures are detrimental for a given process, causing genome instability and diseases. Several helicases have been shown to target and regulate specific G-quadruplex structures. This mini-review focuses on the biological consequences of G4 disruption by different helicases in vivo.