Doenecke D
Eur J Biochem. 1979 Feb 1;93(3):481-6. doi: 10.1111/j.1432-1033.1979.tb12846.x.
The accessibility of DNA in nucleosome dimers (as a model of the chromosomal chain of nucleosomes) was determined by means of modification methylases from Haemophilus influenzae Rd. Using these enzymes, the rate of modification of nucleosome dimers is about one fifth the rate observed with protein-free DNA from chromatin subunit dimers. Methylated DNA sites in nucleosome dimers are readily accessible to micrococcal nuclease. The analysis of the fragment pattern of nucleosomes after methylation and mild nuclease treatment reveals that the methylated sites are predominantly located in the internucleosomal linker DNA. Polylysine binding experiments further support this interpretation. This compound preferentially interacts with the nucleosomal core DNA and protects it against internal cleavage. It neither affects the degradation of methylated sites drastically nor does it inhibit the methylation of nucleosome dimers. Thus, a combination of protection, cleavage and modification is proposed as a useful tool for the analysis of the structure of chromatin.
通过来自流感嗜血杆菌Rd的修饰甲基化酶来确定核小体二聚体（作为核小体染色体链的模型）中DNA的可及性。使用这些酶，核小体二聚体的修饰速率约为染色质亚基二聚体中无蛋白质DNA所观察到速率的五分之一。核小体二聚体中的甲基化DNA位点很容易被微球菌核酸酶作用。对甲基化和温和核酸酶处理后的核小体片段模式分析表明，甲基化位点主要位于核小体间的连接DNA中。聚赖氨酸结合实验进一步支持了这一解释。该化合物优先与核小体核心DNA相互作用并保护其免受内部切割。它既不会显著影响甲基化位点的降解，也不会抑制核小体二聚体的甲基化。因此，保护、切割和修饰的组合被认为是分析染色质结构的有用工具。
