Monitoring the binding of metal cations and histones to DNA in real time using fluorescence assays

Yu Ying Liu, Peng Ye Wang, Shuo Xing Dou, Wei Wei Zhang, Xue Jin Wang, Hong Yi Sang

Chinese Science Bulletin, April 2011, Volume 56, Issue 11, pp 1080-1085

Abstract

The binding of cations (Na+, K+, Mg2+, Ca2+, Mn2+) and histones to DNA can be studied using fluorescence assays. Here, we measured the fluorescence intensity and fluorescence anisotropy of DNA and DNA-histone complexes in the presence of cations. We demonstrate that when different cations are added into a DNA solution, the fluorescence intensities of the stained DNA are reduced by different amounts. Compared with divalent cations, monovalent cations had a weaker effect on fluorescence intensity and fluorescence anisotropy. Divalent (Mn2+, Mg2+, Ca2+) cations markedly enhanced the fluorescence anisotropy of DNA. The binding modes of monovalent and divalent cations to DNA may be different. Divalent cations can change the structure of DNA molecules, or promote the assembly of DNA strands. The addition of histones causes DNA condensation, which mostly occurs during the first few seconds. Cation binding to DNA is abrupt, and is much faster than that of histones.

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