Cooper D N, Gerber-Huber S
Cell Differ. 1985 Sep;17(3):199-205. doi: 10.1016/0045-6039(85)90488-9.
Cytosine methylation in vertebrate genomes occurs predominantly at the dinucleotide CpG. This dinucleotide is deficient in vertebrate DNA, an observation which has hitherto been explained by passive deamination of S-methylcytosine to thymidine. Since the frequency and distribution of CpG may prove to be a useful indirect means to study the function of DNA methylation, it is of interest that the observed 'CpG suppression' is less apparent within and around coding sequences. A variety of different mechanisms now appear to be responsible for maintaining a relatively high CpG level in these regions despite the apparent attendant disadvantage of mutation.
脊椎动物基因组中的胞嘧啶甲基化主要发生在二核苷酸CpG处。这种二核苷酸在脊椎动物DNA中含量不足，迄今为止，这一现象被解释为5-甲基胞嘧啶被动脱氨生成胸腺嘧啶。由于CpG的频率和分布可能被证明是研究DNA甲基化功能的一种有用的间接手段，因此值得关注的是，在编码序列内部和周围，观察到的“CpG抑制”现象不太明显。尽管存在明显的伴随突变劣势，但现在似乎有多种不同机制负责维持这些区域相对较高的CpG水平。
