Fig. 2

Circular dichroism spectra of histone H1-DNA complexes. Rat testis nuclei were digested with MNase (1 Sigma unit/100A₂₆₀ units of nuclei) for different times at 37 °C. The DNA was purified and analyzed on 1.5% agarose gel in TAE buffer. Oligonucleosomal DNA corresponding to 0.5–2 kb was electroeluted and used for CD experiments. a–c, Spectra obtained with linker histone H1d, H1t, and HILS1-oligonucleosomal DNA complex, respectively. The spectra of the various protein–DNA complexes prepared at different histone H1/DNA ratios, as mentioned in the text, in 150 mM NaCl, 10 mM Tris–HCl pH 7.4, 0.1 mM EDTA, were recorded in a JASCO 810 spectropolarimeter. Histone/DNA ratio has been shown on the right side of the spectra. d Comparison of the in vitro DNA condensation property of rH1d, rH1t, and rHILS1 protein. Ellipticity changes observed in figures a–c with rat oligonucleosomal DNA upon binding to histone H1, termed, Δθ are plotted as a function of protein/DNA ratio