Conditions for initial chromatin endonucleolysis and the characteristics of its products

: The restricted initial autohydrolysis of chromatin is used for obtaining its matrix-active fractions. Application of the method for isolating cell nuclei in the presence of 10 mM CaCl2 makes it possible to appreciably inhibit the cleavage of chromatin DNA in the course of isolation, namely to 0.9% according to the acid-soluble fraction. It is shown that at the initial stages of autohydrolysis the method of solubilization is by one order of magnitude more sensitive as compared to the measurement according to the acid-soluble fraction. Initial autohydrolysis is characterized by rapid increment of the amount of the solubilized fraction, delayed formation of mononucleosomes and by the capacity to a 20% activation in the presence of 10(-5) M histamine.