Singer J, Roberts-Ems J, Riggs A D
Science. 1979 Mar 9;203(4384):1019-21. doi: 10.1126/science.424726.
The restriction enzymes Hpa II and Msp I both recognize the sequence 5'-CCGG (C, cytosine; G, guanine). However, Hpa II cuts mouse liver DNA to fragments four times larger than does Msp I. The size of DNA cut by Msp I is close to that predicted from base composition and nearest neighbor analysis. The most probable explanation of these results is that in mouse the site 5'-CCGG is highly methylated.
限制性内切酶Hpa II和Msp I都识别序列5'-CCGG（C代表胞嘧啶；G代表鸟嘌呤）。然而，Hpa II将小鼠肝脏DNA切割成的片段大小是Msp I切割所得片段的四倍。Msp I切割的DNA大小接近于根据碱基组成和相邻碱基分析所预测的大小。对这些结果最可能的解释是，在小鼠中，5'-CCGG位点高度甲基化。
