Umanskiĭ S R, Korol' B A, Nelipovich P A
Mol Biol (Mosk). 1981 Sep-Oct;15(5):1028-39.
Properties of chromatin fragments which are formed as a result of in vivo DNA degradation in thymocytes of gamma-irradiated rats were studied. It is shown that under these conditions chromatin breakdown is accounted for by internucleosomal DNA scission without proteolysis and disturbance of nucleosome structure as judged from how they are split by DNAase I. Amount of mononucleosomes and their dimers, trimers and tetramers is in average about 10% of the fragments formed, and that of oligomers composed of about 8--10 nucleosomes equals about 80%. Core-particles and subnucleosomal fragments are never observed. Chromatin fragments of different size have been purified and their composition was studied. Electrophoresis in 3% PAAG--0.5% agarose divides mononucleosomes into two fractions. The less mobile fraction contains all histones, non-histone proteins and DNA fragments of 178 base pairs long. More mobile mononucleosomes do not contain at least fragments of 178 base pairs long. More mobile mononucleosomes do not contain at least one of the histone H1 subfraction and the size of their DNA is 168 base pairs. Chromatin fragments of different size contain both similar and different non-histone proteins. In mononucleosomes and their dimers, trimers and tetramers proteins are found which are absent in chromatin fragments of high molecular weight. It is assumed that mononucleosomes and their dimers, trimers and tetramers are products of active chromatin degradation and that high molecular weight oligomers are supernucleosomal structures of inactive chromatin.
研究了γ射线照射大鼠胸腺细胞体内DNA降解产生的染色质片段的特性。结果表明，在这些条件下，染色质的断裂是由核小体间DNA断裂引起的，没有蛋白水解和核小体结构的破坏，这从它们被DNA酶I切割的方式可以判断。单核小体及其二聚体、三聚体和四聚体的数量平均约为形成片段的10%，由约8-10个核小体组成的寡聚体数量约为80%。从未观察到核心颗粒和亚核小体片段。已纯化了不同大小的染色质片段并研究了它们 的组成。在3%聚丙烯酰胺凝胶-0.5%琼脂糖中进行电泳可将单核小体分为两个部分。迁移较慢的部分包含所有组蛋白、非组蛋白和178个碱基对长的DNA片段。迁移较快的单核小体至少不包含178个碱基对长的片段。迁移较快的单核小体至少不包含一种组蛋白H1亚组分，其DNA大小为168个碱基对。不同大小的染色质片段含有相似和不同的非组蛋白。在单核小体及其二聚体、三聚体和四聚体中发现了高分子量染色质片段中不存在的蛋白质。据推测，单核小体及其二聚体、三聚体和四聚体是活性染色质降解的产物，而高分子量寡聚体是无活性染色质的超核小体结构。
