Boulikas T
Départment de Biochimie, Faculté de Médecine, Université de Sherbrooke, PQ, Canada.
Proc Natl Acad Sci U S A. 1989 May;86(10):3499-503. doi: 10.1073/pnas.86.10.3499.
Histone ADP-ribosylation was studied using two-dimensional gel electrophoresis after cleavage of the nuclear DNA with nucleases. Modified histones carrying different numbers of ADP-ribose groups form a ladder of bands above each variant histone. Cellular lysates containing unfragmented DNA mainly synthesize mono(ADP-ribosylated) histones. Cleavage of the DNA with either DNase I or micrococcal nuclease to fragments of an average size of 10-20 kilobases (kb) dramatically induces the formation of poly(ADP-ribosylated) species of histones in nuclei. As the number of DNA strand breaks produced by either DNase I or micrococcal nuclease increases and a great number of DNA cuts is introduced (fragments of 0.4-0.2 kb), the size of the poly(ADP-ribose) chains on the histones decreases. Finally, in the presence of 10 mM cAMP as an inhibitor of poly(ADP-ribose) glycohydrolase, human lymphoid nuclei synthesize hyper(ADP-ribosylated) histone H2B with at least 40 ADP-ribose groups attached to it. Lateral ladders emanating at precise points of the linear ladder on hypermodified H2B can arise from branching of poly(ADP-ribose) or from multiple monomodifications of glutamic (or aspartic) acid residues. Branching or de novo monomodifications occur after a precise number of ADP-ribose groups have been added to a histone molecule. Poly(ADP-ribosylated) histones thus appear to be intermediates in nuclear processes involving DNA strand breaks.
利用核酸酶切割核DNA后，通过二维凝胶电泳研究组蛋白的ADP-核糖基化。携带不同数量ADP-核糖基团的修饰组蛋白在每个变体组蛋白上方形成一系列条带。含有未断裂DNA的细胞裂解物主要合成单（ADP-核糖基化）组蛋白。用DNase I或微球菌核酸酶将DNA切割成平均大小为10 - 20千碱基（kb）的片段，会显著诱导细胞核中组蛋白多（ADP-核糖基化）物种的形成。随着DNase I或微球菌核酸酶产生的DNA链断裂数量增加，引入大量DNA切口（0.4 - 0.2 kb的片段），组蛋白上多（ADP-核糖）链的大小会减小。最后，在存在10 mM cAMP作为多（ADP-核糖）糖苷水解酶抑制剂的情况下，人淋巴细胞核合成超（ADP-核糖基化）组蛋白H2B，其上附着至少40个ADP-核糖基团。在超修饰的H2B上，从线性条带的精确点发出的横向条带可能源于多（ADP-核糖）的分支或谷氨酸（或天冬氨酸）残基的多个单修饰。分支或从头单修饰发生在向组蛋白分子添加精确数量的ADP-核糖基团之后。因此，多（ADP-核糖基化）组蛋白似乎是涉及DNA链断裂的核过程中的中间体。
