Structural transition from the random coil to quadruplex of AG 3(T 2AG 3) 3 induced by Zn 2+

Abstract

Structures of G-quadruplex DNAs can be typically stabilized by monovalent cations such as K +, Na +. Some divalent and trivalent cations, such as Sr 2+, Pb 2+, Tb 3+ and Eu 3+, can also induce the formation of G-quadruplex DNA. Here we show that Zn 2+ can induce the human telomeric sequence AG 3(T 2AG 3) 3 to fold the G-quadruplex structure by UV absorbance difference spectra and circular dichroism (CD) spectroscopy. At micromolar concentrations, the Zn 2+-induced changes in the UV absorbance difference spectra and CD spectra are the characteristics of antiparallel G-quadruplexes although the long wavelength CD maximum is around 285 nm rather than the typical value of 295 nm. The binding stoichometry of Zn 2+ per one AG 3(T 2AG 3) 3 molecule is four. To our knowledge, the structural transition of human telomeric sequence induced by Zn 2+ was observed for the first time.