Arnold E A, Wahn U, Young K E
Nucleic Acids Res. 1975 May;2(5):667-81. doi: 10.1093/nar/2.5.667.
The structure of eukaryotic chromatin has been investigated by isolating and analyzing the "accessible" DNA fraction of rat liver chromatin. This DNA fraction has been isolated by titrating the chromatin with the protese-resistant D isomer of polylysine to bind the "accessible" DNA sites. After removal of chromosomal proteins by digestion with pronase, all DNA not protected from attack by bound polylysine was removed by digestion with DNase. Even after exhaustive treatment with pronase and DNase approximately 30% of the chromatin DNA remains resistant to nuclease attack. Analysis of the isolated DNA shows it to be mainly double-stranded with an average size of 200-250 base pairs. The DNA is slightly A-T rich and contains both repetitive and "single-copy" nuleotide sequences. The results suggest that there are extensive regions in chromatin where the DNA is not tightly complexed with protein. Furthermore, the DNA of these regions is similar in gross properties to the DNA of the total genome.
通过分离和分析大鼠肝脏染色质的“可及”DNA部分，对真核染色质的结构进行了研究。该DNA部分是通过用对蛋白酶有抗性的聚赖氨酸D异构体滴定染色质以结合“可及”DNA位点而分离出来的。在用链霉蛋白酶消化去除染色体蛋白质后，所有未被结合的聚赖氨酸保护免受攻击的DNA通过用DNase消化而被去除。即使在用链霉蛋白酶和DNase进行彻底处理后，仍有约30%的染色质DNA对核酸酶攻击具有抗性。对分离出的DNA的分析表明，它主要是双链的，平均大小为200 - 250个碱基对。该DNA略富含A - T，并且包含重复和“单拷贝”核苷酸序列。结果表明，染色质中存在广泛的区域，其中DNA与蛋白质没有紧密结合。此外，这些区域的DNA在总体性质上与整个基因组的DNA相似。
