Muliavko N A, Khalmuradov A G
Biokhimiia. 1984 Oct;49(10):1623-7.
The dependence of ADP-ribosylation of chicken liver nuclear histones on NAD concentration in the nuclei was studied under conditions of stimulation of coenzyme synthesis by the nicotinamide and nicotinic acid as well as upon addition of various concentrations of the [Ado-U-14C]NAD nuclei to the incubation mixture. In the first case, the rate of [Ado-U-14C]NAD incorporation into the histones was decreased due to the dilution of the label by the de novo synthesized NAD. The amount of the latter formed under effects of nicotinic acid and nicotinamide increased, correspondingly, from 2,2 X 10(-5) mmol up to 4.1 X 10(-5) and 7.0 X 10(-5) mmol per mg of nuclear protein. The incorporation of [Ado-U-14C]NAD into the histones decreased from 12.0 X 10(-8) mmol after incubation of liver slides with nicotinic acid and nicotinamide down to 8.0 X 10(-8) and 7.0 X 10(-8) mmol, respectively. With a rise in the concentration of exogenous [Ado-U-14C]NAD, the level of ADP-ribosylation of nuclear histones increased, the plot [14C]NAD incorporation at the labeled coenzyme concentration of 25 X 10(-7) mM/mg of histone had a plateau. Changes in the labeled substrate concentration brought about corresponding changes in the average length of the histone-linked poly-(ADP-ribose) chain.
在烟酰胺和烟酸刺激辅酶合成的条件下，以及在向孵育混合物中添加不同浓度的[Ado-U-¹⁴C]NAD细胞核的情况下，研究了鸡肝细胞核组蛋白的ADP-核糖基化对细胞核中NAD浓度的依赖性。在第一种情况下，由于从头合成的NAD对标记物的稀释作用，[Ado-U-¹⁴C]NAD掺入组蛋白的速率降低。在烟酸和烟酰胺的作用下形成的后者的量相应地从每毫克核蛋白2.2×10⁻⁵ mmol增加到4.1×10⁻⁵和7.0×10⁻⁵ mmol。在用烟酸和烟酰胺孵育肝切片后，[Ado-U-¹⁴C]NAD掺入组蛋白的量分别从12.0×10⁻⁸ mmol降至8.0×10⁻⁸和7.0×10⁻⁸ mmol。随着外源[Ado-U-¹⁴C]NAD浓度的升高，细胞核组蛋白的ADP-核糖基化水平增加，在标记辅酶浓度为25×10⁻⁷ mM/毫克组蛋白时，[¹⁴C]NAD掺入曲线有一个平台期。标记底物浓度的变化导致组蛋白连接的聚（ADP-核糖）链的平均长度发生相应变化。
