Thraves P J, Smulson M E
Carcinogenesis. 1982;3(10):1143-8. doi: 10.1093/carcin/3.10.1143.
Poly(ADP-Rib) polymerase is activated by strand breaks in DNA and appears to play an important role in DNA repair. The enzyme catalyses the poly ADP-ribosylation of histones and non-histone proteins, yet the contribution of these major alterations in chromatin composition have, as yet, not been critically evaluated with regard to DNA strand breaks. In the present study, the effects of N-methyl-N-nitrosourea (MNU) upon the poly ADP-ribosylation of nuclear protein acceptors have been identified and quantified at the oligonucleosomal level of chromatin. Treatment of HeLa cells with MNU (4.5 mM) for 1 h resulted in a reduction in the cellular NAD pool (30%), a 2-3 fold stimulation of poly ADP-ribosylation in isolated nuclei and in isolated oligonucleosomes. Of acceptors modified, the automodification of the polymerase was stimulated at least 3-fold. Analysis of the acid-soluble acceptors showed a stimulation in the modification of the core histones and a 2-fold increase in histone H1 poly ADP-ribosylation. This modification causes a novel crosslinking of the latter histone, and this has been studied as it relates to DNA strand breaks in the present work. In vivo treatment with MNU resulted in the synthesis of longer chain or more complex polymer species at the expense of the shorter chained ADP-ribose moieties.
聚（ADP-核糖）聚合酶可被DNA链断裂激活，且似乎在DNA修复中发挥重要作用。该酶催化组蛋白和非组蛋白的聚ADP核糖基化，但就DNA链断裂而言，染色质组成中这些主要改变的作用尚未得到严格评估。在本研究中，已在染色质的寡核小体水平上鉴定并定量了N-甲基-N-亚硝基脲（MNU）对核蛋白受体聚ADP核糖基化的影响。用MNU（4.5 mM）处理HeLa细胞1小时导致细胞内NAD池减少（30%），分离的细胞核和分离的寡核小体中的聚ADP核糖基化受到2至3倍的刺激。在被修饰的受体中，聚合酶的自身修饰至少被刺激了3倍。对酸溶性受体的分析表明，核心组蛋白的修饰受到刺激，组蛋白H1的聚ADP核糖基化增加了2倍。这种修饰导致了后一种组蛋白的新型交联，在本研究中已对其与DNA链断裂的关系进行了研究。体内用MNU处理导致合成更长链或更复杂的聚合物种类，而较短链的ADP-核糖部分减少。
