Fisher E A, Felsenfeld G
Biochemistry. 1986 Dec 2;25(24):8010-6. doi: 10.1021/bi00372a033.
The dependence of chromatin conformation upon salt concentration has been studied for chicken ovalbumin and beta-globin genes isolated from oviduct and adult erythrocytes. At NaCl concentrations of 25 or 50 mM, the sedimentation properties, as a function of DNA size, of ovalbumin and globin chromatin are similar regardless of the source of the chromatin. In 100 mM NaCl, however, beta-globin chromatin isolated from erythrocytes sediments more slowly than an ovalbumin chromatin fraction from erythrocytes containing DNA of the same size. When the same experiment is carried out with material isolated from oviduct nuclei, the relative sedimentation rates are reversed, so that the ovalbumin chromatin sediments more slowly. This behavior cannot be accounted for by differences in binding of RNA polymerase or other molecules associated with transcription, or by partial aggregation of the chromatin. The most reasonable explanation is that transcriptionally active chromatin with a history of transcriptional activity, although largely covered with histones and capable of considerable compaction, is not able to form a fully compact structure as the ionic strength is raised. This behavior is consistent with a slight depletion in active chromatin of core histones or histone H1/H5 or both.
针对从输卵管和成年红细胞中分离出的鸡卵清蛋白基因和β-珠蛋白基因，研究了染色质构象对盐浓度的依赖性。在25或50 mM的NaCl浓度下，无论染色质的来源如何，卵清蛋白和珠蛋白染色质的沉降特性（作为DNA大小的函数）都是相似的。然而，在100 mM NaCl中，从红细胞中分离出的β-珠蛋白染色质的沉降速度比来自含有相同大小DNA的红细胞的卵清蛋白染色质部分要慢。当用从输卵管核中分离出的物质进行相同实验时，相对沉降速率会反转，使得卵清蛋白染色质沉降得更慢。这种行为无法通过RNA聚合酶或其他与转录相关分子的结合差异，或染色质的部分聚集来解释。最合理的解释是，具有转录活性历史的转录活性染色质，尽管大部分被组蛋白覆盖且能够进行相当程度的压缩，但随着离子强度的增加，它无法形成完全紧密的结构。这种行为与核心组蛋白或组蛋白H1/H5或两者在活性染色质中的轻微消耗是一致的。
