[Activation of chromatin and histone proteolysis during protein synthesis inhibition in liver cells]

The initial response of rat liver chromatin to strong (up to 95%) inhibition of protein synthesis by cycloheximide consist in activation (2-3-fold) of proteolysis of weakly bound nuclear histones, especially of the acetylated histone H3, in a decrease (7-8-fold) of the rate of histone acetylation, in an increased sensitivity of chromatin to DNAase I (EC 3.1.4.5) and in transformations of the DNA-histone interactions during the first 1-2 hours after inhibition of translation. This results in a temporary activation of chromatin which manifests itself in acceleration of RNA synthesis. Within 3 hours following the inhibition of translation the rate of proteolysis in the nucleus, the amount of acetylated forms of histone H3 and other acetylated proteins, the sensitivity of chromatin to DNAase I and the rate of RNA synthesis are decreased. It is assumed that at strong inhibition of protein synthesis one of the factors controlling chromatin activity is a specific proteolysis of modified histones.