[Features of poly-ADP-ribosylation and chromatin structure under conditions of varying NAD content in the rat liver].

It is shown that nicotinamide-induced in vivo stimulation of NAD biosynthesis in the liver nuclei of rats causes a decrease of the DNA sensitivity to treatment with DNAse I under conditions of weak hydrolysis. When rats are given synthetic vitamin PP-deprived food, the NAD level in the liver falls down to 40% and a great number of DNAse I-hypersensitive chromatin sites appear. A 24% decrease in the level of poly-ADP-ribosylation of total histones in comparison with the control has been observed with hypovitaminosis. Under conditions of vitamin PP deficiency nicotinamide administered to animals has increased the 14C NAD incorporation into histones 2 times (as compared with the control). These variations occur primarily due to increase of the label incorporation to histone H1. Fractionation of chromatin by solutions of different ionic strength has confirmed that vitamin PP deficiency and NAD amount decrease in the liver are accompanied by a relative increase of the NAD-pyrophosphorylase and poly-ADP-ribose polymerase activities in the fraction extracted by the low ionic solution.