G-quadruplexes-novel mediators of gene function.

Since the famous double-helix model was proposed, chromosomal DNA has been regarded as a rigid molecule containing the genetic information of an organism. It is clear now that DNA can adopt many transient, complex structures that can perform different biological functions. The G4 DNA (also called DNA G-quadruplex or G-tetraplex), a four-stranded DNA structure composed of stacked G-tetrads (guanine tetrads), has attracted much attention during the past two decades due to its ability to adopt a variety of structures and its possible biological functions. This review gives a glimpse on the structural diversity and biophysical properties of these fascinating DNA structures. Common methods that are widely used in investigating biophysical properties and biological functions of G4 DNA are described briefly. Next, bioinformatics studies that indicate evidence of evolutionary selection and potential functions of G4 DNA are discussed. Finally, examples of various biological functions of different G4 DNA are given, and potential roles of G4 DNA in respect of cardiovascular science are discussed.