Molitor H, Drahovsky D, Wacker A
Biochim Biophys Acta. 1976 Apr 15;432(1):28-36. doi: 10.1016/0005-2787(76)90038-1.
Enzymatic methylation of DNA in mouse L cells has been studied using DNA fibre autoradiography to analyse the distribution of 5-methylcytosine in chromosomal DNA. The autoradiographic pattern of DNA labelled in the 5-methylcytosine is in several respects similar to the pattern of DNA replication. Two mean features are apparent: (1) the silver grains appear in well defined sections, and (2) the labelled sections are arranged in tandem along each DNA double helix. After a short pulse of radioactivity in the rate of growth of labeled sections in the pattern of DNA replication and the enzymatic methylation of DNA are identical. Unlike the replication pattern, DNA labeled during the S phase with L-[Me-3H] methionine is not completely labeled. There are distinct, 8-20 mum intervals in the autoradiographic pattern of this DNA. The length of these intervals may correspond to unmethylated sections of chromosomal DNA of about 23 to 58 kilo base pairs. These unmethylated sections of chromosomal DNA represent about 10% of the total genome.
利用DNA纤维放射自显影技术研究了小鼠L细胞中DNA的酶促甲基化，以分析5-甲基胞嘧啶在染色体DNA中的分布。5-甲基胞嘧啶标记的DNA的放射自显影模式在几个方面与DNA复制模式相似。有两个明显特征：（1）银颗粒出现在明确界定的区域，（2）标记区域沿每个DNA双螺旋串联排列。在短暂的放射性脉冲后，DNA复制模式中标记区域的生长速率与DNA的酶促甲基化相同。与复制模式不同，在S期用L-[甲基-³H]甲硫氨酸标记的DNA并未完全被标记。在这种DNA的放射自显影模式中有明显的8-20微米间隔。这些间隔的长度可能对应于约23至58千碱基对的染色体DNA未甲基化区域。这些染色体DNA的未甲基化区域约占基因组总量的10%。
