Search

The effects of divalent ions (Mn2+, Mg2+, Ca2+) on the interaction between DNA and histone are studied using a fluorescence anisotropy assay. Fluorescence anisotropies of DNA and DNA-histone in the presence of divalent ions (Mn2+, Mg2+, Ca2+) are measured. The results indicate that histone reduces the fluorescence anisotropy of lambda DNA while the divalent ions (Mn2+, Mg2+, Ca2+) significantly enhance the fluorescence anisotropy. Compared to the case of DNA incubated with histone alone, there are more histones binding to DNA when divalent ion, histone and DNA are incubated together. We also find that Mn2+ makes the DNA-histone complexes more condensed than the other ions do. [ABSTRACT FROM AUTHOR]

Molecular combing is a powerful and simple method for aligning DNA molecules onto a surface. Using this technique combined with fluorescence microscopy, DNA-histone complexes are stretched on a hydrophobic polymethyl methacrylate (PMMA) surface and observed directly. We have developed a new method to stretch single DNA-histone complexes, termed spin-stretching. The results show that the histones markedly enhance DNA binding to the PMMA surface. DNA winds around the histones and therefore decreases in length. The number of histones that bind to each DNA molecule is found to correlate with the histone concentration. The combed DNA-histone complexes are found to depend on two factors: the binding force on the surface and the centrifugal force at its local position. Na+ ions should compete with histones for binding to DNA; however, the observed competitive binding effect of Na+ ions at low concentrations was negligible. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The effects of monovalent (Na+, K+) and divalent (Mg2+, Ca2+, Mn2+) ions on the interaction between DNA and histone are studied using the molecular combing technique, k-DNA molecules and DNA-histone complexes incubated with metal cations (Na+, K+, Mg2+, Ca2+, Mn2+) are stretched on hydrophobic surfaces, and directly observed by fluorescence microscopy. The results indicate that when these cations are added into the DNA solution, the fluorescence intensities of the stained DNA are reduced differently. The monovalent cations (Na+, K+) inhibit binding d histone to DNA. The divalent cations (Mg2+, Ca2+, Mn2+) enhance significantly the binding of histone to DNA and the binding of the DNA-histone complex to the hydrophobic surface. Mn2+ also induces condensation and aggregation of the DNA- histone complex. [ABSTRACT FROM AUTHOR]