Davis A H, Reudelhuber T L, Garrard W T
J Mol Biol. 1983 Jun 15;167(1):133-55. doi: 10.1016/s0022-2836(83)80038-2.
We have employed a chromatin fractionation procedure on micrococcal nuclease-digested nuclei to examine the chromatin structure of mouse ribosomal RNA genes in two systems that differ by at least 14-fold in the level of ribosomal RNA transcription. In a cultured cell line enriched in transcriptionally active ribosomal chromatin, most ribosomal sequences are preferentially sensitive to digestion by micrococcal nuclease, reside in an insoluble chromatin fraction, and lack typical nucleosomal packaging; only minor amounts of ribosomal sequences are packaged into soluble, nucleosomal chromatin. By contrast, in adult liver, which is enriched in transcriptionally inactive ribosomal chromatin, the majority of ribosomal genes are packaged into soluble, nucleosomal chromatin. However, a significant fraction of liver ribosomal chromatin is insoluble and possesses a non-nucleosomal structure. Therefore, within a single cell population or tissue, mouse ribosomal RNA genes are organized into both nucleosomal and non-nucleosomal chromatin structures. We suggest that these structures have functional significance.
我们采用了一种对微球菌核酸酶消化的细胞核进行染色质分级分离的方法，以研究小鼠核糖体RNA基因在两个核糖体RNA转录水平相差至少14倍的系统中的染色质结构。在一个富含转录活性核糖体染色质的培养细胞系中，大多数核糖体序列对微球菌核酸酶的消化具有优先敏感性，存在于不溶性染色质部分，并且缺乏典型的核小体包装；只有少量的核糖体序列被包装成可溶性的核小体染色质。相比之下，在富含转录无活性核糖体染色质的成年肝脏中，大多数核糖体基因被包装成可溶性的核小体染色质。然而，相当一部分肝脏核糖体染色质是不溶性的，并且具有非核小体结构。因此，在单个细胞群体或组织内，小鼠核糖体RNA基因被组织成核小体和非核小体染色质结构。我们认为这些结构具有功能意义。
