Histone-induced conformational changes in DNA as probed by quasi-elastic light scattering.

Abstract

AbstractQuasi‐elastic light scattering as measured by intensity fluctuation (self‐beat) spectroscopy in the time domain can be profitably used to follow both the translational diffusion D and the dominant internal flexing mode τint of DNA and its complexes with various histones in aqueous salt solutions. Without histones, DNA is found to have D = 1.6 × 10−8 cm2/sec and τint ≅ 5 × 10−4 sec in 0.8 M NaCl, 2 M urea at 20°C. Total histone as well as fraction F2A induce supercoiling (D = 2.6 × 10−8 cm2/sec, τint ≅ 2.8 × 10−4 sec) whereas fraction F1 induces uncoiling (D = 1.0 × 10−8 cm2/sec, τint ≅ 9.4 × 10−4 sec). Upon increasing the salt concentration to 1.5 M the DNA–histone complex dissociates (D = 1.8 × 10−8 cm2/sec). Upon decreasing the salt concentration to far below 0.8 M, the DNA–histone complex eventually precipitates as a chromatin gel.