Razin A, Cedar H
Proc Natl Acad Sci U S A. 1977 Jul;74(7):2725-8. doi: 10.1073/pnas.74.7.2725.
The content of 5-methylcytosine in eukaryotic DNA was measured by mass spectrometry. Almost equal amounts of methylated cytosine were found in the DNA of various tissues of the chicken. When chromatin or nuclei were digested with micrococcal nuclease, 50% of the DNA was found to be nuclease resistant. In contrast to this, over 75% of the 5-methylcytosine was protected from nuclease digestion by chromatin proteins. These results suggest that 5-methylcytosine is nonrandomly distributed with respect to the nucleoproteins.
采用质谱法测定真核生物DNA中5-甲基胞嘧啶的含量。在鸡的各种组织的DNA中发现了几乎等量的甲基化胞嘧啶。当用微球菌核酸酶消化染色质或细胞核时，发现50%的DNA对核酸酶具有抗性。与此形成对比的是，超过75%的5-甲基胞嘧啶受到染色质蛋白的保护而不被核酸酶消化。这些结果表明，5-甲基胞嘧啶相对于核蛋白是非随机分布的。
