Aubin R, Fréchette A, de Murcia G, Malouin F, Lord A, Mandel P, Poirier G G
Princess Takamatsu Symp. 1983;13:83-91.
The properties of poly(ADP-ribose) polymerase associated to nucleosomes and nuclei were analyzed by measuring enzymatic activity, isolating poly(ADP-ribosylated) histones and by electron microscopy. The enzyme was found to be most active in tri- and tetranucleosomes. The presence of NaC1 (0 to 200 mM) in the incubation medium showed a very small inhibitory effect on the enzymatic activity of isolated nucleosomes; however, the enzyme activity of incubated nuclei showed a gradual reduction with increasing salt concentrations leading to an almost complete inhibition at 200 mM NaC1. In parallel, the histones H1 extracted from isolated nucleosomes incubated at 200 mM NaC1 were hyper(ADP-ribosylated), whereas the histones H1 extracted from nuclei chromatin showed no highly modified forms at 200 mM NaC1. The effect of ethidium bromide (EB) was also analyzed and was found to stimulate enzyme activity in tetranucleosomes and octanucleosomes but not in dinucleosomes and nucleosomes of 20 repeat units. Electron microscopic analysis of poly(ADP-ribosylated) nucleosomes does not show the presence of aggregates at low ionic strength. However at higher ionic strengths the presence of localized relaxed domains of chromatin is evidenced in condensed nucleosomes.
通过测量酶活性、分离聚（ADP - 核糖基化）组蛋白以及电子显微镜分析，研究了与核小体和细胞核相关的聚（ADP - 核糖）聚合酶的特性。发现该酶在三聚体和四聚体核小体中活性最高。孵育介质中NaCl（0至200 mM）的存在对分离的核小体的酶活性显示出非常小的抑制作用；然而，孵育细胞核的酶活性随着盐浓度的增加而逐渐降低，在200 mM NaCl时几乎完全抑制。同时，从在200 mM NaCl下孵育的分离核小体中提取的组蛋白H1被高度（ADP - 核糖基化），而从细胞核染色质中提取的组蛋白H1在200 mM NaCl时未显示出高度修饰的形式。还分析了溴化乙锭（EB）的作用，发现它能刺激四聚体核小体和八聚体核小体中的酶活性，但不能刺激二聚体核小体和20个重复单元的核小体中的酶活性。聚（ADP - 核糖基化）核小体的电子显微镜分析表明，在低离子强度下不存在聚集体。然而，在较高离子强度下，在浓缩的核小体中可证明存在染色质的局部松弛区域。
