Ehrlich M, Gama-Sosa M A, Huang L H, Midgett R M, Kuo K C, McCune R A, Gehrke C
Nucleic Acids Res. 1982 Apr 24;10(8):2709-21. doi: 10.1093/nar/10.8.2709.
Analysis of the total base composition of DNA from seven different normal human tissues and eight different types of homogeneous human cell populations revealed considerable tissue-specific and cell-specific differences in the extent of methylation of cytosine residues. The two most highly methylated DNAs were from thymus and brain with 1.00 and 0.98 mole percent 5-methylcytosine (m5C), respectively. The two least methylated DNAs from in vivo sources were placental DNA and sperm DNA, which had 0.76 and 0.84 mole percent m5C, respectively. The differences between these two groups of samples were significant with p less than 0.01. The m5C content of DNA from six human cell lines or strains ranged from 0.57 to 0.85 mole percent. The major and minor base composition of DNA fractionated by reassociation kinetics was also determined. The distribution of m5C among these fractions showed little or no variation with tissue or cell type with the possible exception of sperm DNA. In each case, nonrepetitive DNA sequences were hypomethylated compared to unfractionated DNA.
对来自七种不同正常人体组织和八种不同类型均质人类细胞群体的DNA的总碱基组成进行分析后发现，胞嘧啶残基的甲基化程度存在显著的组织特异性和细胞特异性差异。甲基化程度最高的两种DNA分别来自胸腺和大脑，5-甲基胞嘧啶（m5C）的摩尔百分比分别为1.00和0.98。来自体内来源的甲基化程度最低的两种DNA是胎盘DNA和精子DNA，它们的m5C摩尔百分比分别为0.76和0.84。这两组样品之间的差异具有显著性，p值小于0.01。六种人类细胞系或菌株的DNA的m5C含量在0.57至0.85摩尔百分比之间。还测定了通过重缔合动力学分级分离的DNA的主要和次要碱基组成。除精子DNA可能例外，这些级分中m5C的分布随组织或细胞类型几乎没有变化或没有变化。在每种情况下，与未分级的DNA相比，非重复DNA序列的甲基化程度较低。
