Ward T H, Itzhaki R F
J Cell Sci. 1981 Oct;51:153-62. doi: 10.1242/jcs.51.1.153.
Studies have been made of the effect of N-methyl-N-nitrosourea on hen erythrocytes in vitro. These were done to find whether the highly condensed state of the chromatin and the very low metabolic activity of these cells would affect the extent of methylation of the DNA and chromatin proteins and the persistence of any methylation sites in these macromolecules with time after treatment. Also, the effect of methylnitrosourea on incorporation of [3H] uridine into RNA has been examined. It has been found that the DNA, histones and non-histone proteins are methylated. The main methylation site in DNA is 7-methylguanine and its level is higher than that found by others in the DNA of other cell types after treatment with methylnitrosourea; however, methylation of the two types of protein (especially the histones) is relatively very low. The level of methylation decreases in the DNA and the chromatin proteins with time after treatment. The amount of [3H] uridine in RNA was found to decrease after the treatment.
已经对N-甲基-N-亚硝基脲在体外对母鸡红细胞的作用进行了研究。进行这些研究是为了确定染色质的高度浓缩状态以及这些细胞极低的代谢活性是否会影响DNA和染色质蛋白的甲基化程度，以及处理后这些大分子中任何甲基化位点随时间的持续性。此外，还研究了甲基亚硝基脲对[3H]尿苷掺入RNA的影响。已发现DNA、组蛋白和非组蛋白蛋白质发生了甲基化。DNA中的主要甲基化位点是7-甲基鸟嘌呤，其水平高于其他细胞类型在用甲基亚硝基脲处理后的DNA中所发现的水平；然而，这两种蛋白质（尤其是组蛋白）的甲基化相对非常低。处理后，DNA和染色质蛋白中的甲基化水平随时间降低。发现处理后RNA中[3H]尿苷的量减少。
