Study in chemical methylation of cytosine base

C5位胞嘧啶碱基甲基化是基因表达、细胞分化、病毒感染等方面的重要修饰，为了开发基于三链体形成的寡核苷酸诱导甲基化的化学技术，建立了一种结合甲基锍基团的寡核苷酸合成方法。作为用甲基锍缀合寡核苷酸处理靶DNA的结果，形成了一些源自鸟嘌呤碱基上的甲基化（烷基化）的DNA片段。重要的是，三链体形成寡核苷酸缀合烷化剂诱导DNA烷基化，这是朝向胞嘧啶甲基化的第一步。

Methylation of the cytosine base at C5 position was important modification concerning gene expression, cellular differentiation, virus infection and so on. Toward the development of the triplex-forming-oligonucleotide-based chemical technique that induces the methylation, a synthetic method of oligonucleotide conjugating a methylsulfonium group was established. As a result of the treatment of target DNA with a methyl sulfonium conjugating oligonucleotide, some DNA fragments derived from the methylation(alkylation) on the guanine bases were formed. It is important that triplex forming oligonucleotide conjugating an alkylating agent induced DNA alkylation, which is the first step toward the methylation of cytosine.