Reeves R, Gorman C M, Howard B
Nucleic Acids Res. 1985 May 24;13(10):3599-615. doi: 10.1093/nar/13.10.3599.
The nucleoprotein structures formed on various plasmid expression vectors transfected into mammalian cells by both the calcium phosphate and DEAE-dextran methods have been studied. We demonstrate by a variety of means that mammalian cells are capable of rapidly assembling non-integrated circular plasmids (both replicating and non-replicating) into typical "minichromosomes" containing nucleosomes with a 190 bp repetitive spacing. Treatment of recipient cells with sodium butyrate for a short period of time (12-16 h) immediately following transfection markedly increased the DNase I digestion sensitivity of the newly assembled plasmid chromatin. Furthermore, minichromosomes isolated from such butyrate-treated cells are depleted in histone H1 and contain highly acetylated forms of histone H4. These findings are entirely consistent with our earlier speculation (Gorman et al., Nucleic Acids Res. 11, 1044; 1983) that appropriate butyrate treatment might stimulate transient expression of newly transfected genes by facilitating their assembly into an "active" type of chromatin structure.
对通过磷酸钙和DEAE-葡聚糖方法转染到哺乳动物细胞中的各种质粒表达载体上形成的核蛋白结构进行了研究。我们通过多种方法证明，哺乳动物细胞能够迅速将非整合的环状质粒（包括复制型和非复制型）组装成典型的“微型染色体”，这些微型染色体含有重复间距为190 bp的核小体。转染后立即用丁酸钠处理受体细胞短时间（12 - 16小时），显著增加了新组装的质粒染色质对DNase I消化的敏感性。此外，从这种经丁酸钠处理的细胞中分离出的微型染色体中组蛋白H1含量减少，并且含有高度乙酰化形式的组蛋白H4。这些发现与我们早期的推测（Gorman等人，《核酸研究》11, 1044；1983）完全一致，即适当的丁酸钠处理可能通过促进新转染基因组装成“活性”类型的染色质结构来刺激其瞬时表达。
