The interaction of histones with native and denatured DNA.

: A description is provided for the effects of various concentrations of NaCl, MgC12, and urea on the precipitation of native and denatured DNA by histones. The solubility of complexes between total histones and fractions F1, F2a, F2b, and F3 with denatured and partially denatured DNA was greater than that of the complexes between histones and native DNA. The complexes formed between histones and denatured DNA were soluble in excess histones, unlike those formed between histones and native DNA. Electrophoresis of the individual histone fractions through a polyacrylamide gel layer containing DNA led to the determination of the amount of histones bound to native and denatured DNA under conditions of saturation (0.04 ionic strength). It was established that 1 mug of native DNA binds 2.4, 2.8, and 2.5 mug of histones F1, F2a, F2b and F3, respectively. The denatured DNA binds 1.4-1.5 times less of each histone fraction than does native DNA, but the binding seems stronger. It has been demonstrated that the histones inhibit to a lesser extent the template activity of denatured and partially denatured (about 5% disruption of hydrogen bonds) DNA in comparison with native DNA in an RNA polymerase system. It has been suggested that the properties of the complexes formed between histones and denatured or partially denatured DNA, may underlie the control mechanism for genome activity in the cells of higher organisms.