Sheffery M, Rifkind R A, Marks P A
Proc Natl Acad Sci U S A. 1982 Feb;79(4):1180-4. doi: 10.1073/pnas.79.4.1180.
The sensitivity to digestion by DNase I of chromatin containing the alpha- and beta(major)-globin genes and the pattern of DNA methylation near these genes was examined during hexamethylenebisacetamide (HMBA)-mediated erythroid differentiation of murine erythroleukemia cells (MELC). In uninduced and induced cells, the chromatin regions containing the alpha- and beta-(major)-globin genes are more sensitive to digestion by DNase I than is the region containing an immunoglobulin gene (Igalpha) not expressed during erythroid differentiation. However, at low concentrations of DNase I, a 6- to 10-fold increase in site-specific cleavages was generated in chromatin regions near both the alpha- and beta(major)-globin genes in cells induced to differentiate by HMBA. The DNase I hypersensitive site near the beta(major)-globin gene maps to a small region near the 5' terminus of the gene. No detectable change in the pattern of DNA methylation around either the alpha- or beta-globin genes was observed during HMBA-mediated erythroid differentiation. Of the potentially methylated sites assayed and mapped near the beta(major)-globin gene, one site is fully methylated, one is partially methylated, and one is unmethylated both in uninduced and induced cells. Many (but not all) sites assayed near the alpha-globin genes are unmethylated in both uninduced and induced cells. These results show that specific alterations of chromatin structure occur during MELC differentiation and suggest that these changes may not involve alterations in the pattern of DNA methylation.
在六亚甲基双乙酰胺（HMBA）介导的小鼠红白血病细胞（MELC）红系分化过程中，研究了含有α和β（主要）珠蛋白基因的染色质对DNase I消化的敏感性以及这些基因附近的DNA甲基化模式。在未诱导和诱导的细胞中，含有α和β（主要）珠蛋白基因的染色质区域比含有在红系分化过程中不表达的免疫球蛋白基因（Igalpha）的区域对DNase I消化更敏感。然而，在低浓度的DNase I下，在经HMBA诱导分化的细胞中，α和β（主要）珠蛋白基因附近的染色质区域产生了位点特异性切割增加6至10倍的情况。β（主要）珠蛋白基因附近的DNase I超敏感位点定位于该基因5'末端附近的一个小区域。在HMBA介导的红系分化过程中，未观察到α或β珠蛋白基因周围的DNA甲基化模式有可检测到的变化。在β（主要）珠蛋白基因附近检测和定位的潜在甲基化位点中，一个位点在未诱导和诱导的细胞中均完全甲基化，一个位点部分甲基化，一个位点未甲基化。在α珠蛋白基因附近检测的许多（但不是全部）位点在未诱导和诱导的细胞中均未甲基化。这些结果表明，在MELC分化过程中发生了染色质结构的特异性改变，并表明这些变化可能不涉及DNA甲基化模式的改变。
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