Katz R A, Erlanger B F, Guntaka R V
Biochim Biophys Acta. 1983 Apr 15;739(3):258-64. doi: 10.1016/0167-4781(83)90099-4.
XC cell line was established from a rat fibrosarcoma induced by avian sarcoma virus. Analysis of ribosomal RNA genes in the DNA of this cell line indicated that there was a 3- to 4-fold increase in the number of the rDNA repeating units. [methyl-14C]Methionine labeling experiments as well as Southern blot analysis of the restriction endonuclease fragments showed extensive methylation of the cytosine residues in the rDNA. Further analysis by HpaII, HhaI and MspI suggested that the entire rDNA repeat unit was uniformly methylated in the recognition sequence for these enzymes. Parallel experiments with two other rat cell lines (rat embryo fibroblasts and adenovirus-transformed rat embryo cells) indicated no evidence of methylation in the rDNA.
XC细胞系是从禽肉瘤病毒诱导的大鼠纤维肉瘤中建立的。对该细胞系DNA中的核糖体RNA基因分析表明，rDNA重复单元的数量增加了3至4倍。[甲基-14C]甲硫氨酸标记实验以及限制性内切酶片段的Southern印迹分析表明，rDNA中的胞嘧啶残基存在广泛甲基化。用HpaII、HhaI和MspI进一步分析表明，整个rDNA重复单元在这些酶的识别序列中均一甲基化。对另外两种大鼠细胞系（大鼠胚胎成纤维细胞和腺病毒转化的大鼠胚胎细胞）进行的平行实验表明，rDNA中没有甲基化的证据。
