[Properties of activated chromatin from rat liver shortly after partial hepatectomy]

The properties of rat liver chromatin 1, 2 and 6 hours after partial hepatectomy have been studied by means of cytochemical and biochemical methods. An increase in the accessibility of DNA to low molecular weight ligands, RNA--polymerase and RNAse I and also of the distances between nucleosomes and their heterogeneity in length on electron -- microscopic photographs has been found. Analysis of the isotherms of adsorption has revealed an increase in the number of binding sites for ethidium bromide on DNA and accordingly a decrease in the extent of the filling of the template with protein in activated chromatin. Two hours after partial hepatectomy rat liver chromatin does not differ in all parameters studied from control chromatin. Limited digestion of chromatin with DNAse I almost fully eliminates the difference between the fractions of activated and control chromatin in the number of binding sites for the ligands to the fractions resistent in these conditions to nuclease. A suggestion that the changes in the properties of chromatin upon activation are due to the change in the character of chromatin proteins interaction with DNA are discussed.