Johnson E M, Allfrey V G, Bradbury E M, Matthews H R
Proc Natl Acad Sci U S A. 1978 Mar;75(3):1116-20. doi: 10.1073/pnas.75.3.1116.
The localization of DNA sequences coding for ribosomal RNA was studied by hybridization of purified ribosomal RNA to DNA from chromatin fragments prepared by limited digestion of Physarum nuclei with staphylococcal nuclease. The 32P-labeled 19S and 26S RNA hybridized to DNA from nucleosome monomers, dimers, trimers, and higher oligomers, separated by sucrose gradient centrifugation, although the level of hybridization to DNA from nucleosome fractions was less than the level of hybridization to undigested nuclear DNA. The distribution of 19S and 26S rDNA sequences in the nucleosome fractions differed from the distribution of bulk DNA in that the rDNA sequences were recovered primarily in two fractions containing monomer-sized DNA lengths (140-160 base pairs). The percentage of DNA hybridizing to 19S plus 26S RNA was greater in peak A, the more slowly sedimenting monomer peak, than in any other chromatin fraction at all stages of digestion. Peak A and monomer particles differed in protein content and distribution. The presence of ribosomal cistrons in an altered nucleosome configuration may be related to changes in functional states of rDNA chromatin.
通过将纯化的核糖体RNA与用葡萄球菌核酸酶有限消化多头绒泡菌细胞核制备的染色质片段的DNA进行杂交，研究了编码核糖体RNA的DNA序列的定位。经蔗糖梯度离心分离的核小体单体、二聚体、三聚体和更高聚体的DNA与32P标记的19S和26S RNA杂交，尽管与核小体组分DNA的杂交水平低于与未消化的核DNA的杂交水平。核小体组分中19S和26S rDNA序列的分布与总体DNA的分布不同，因为rDNA序列主要在两个含有单体大小DNA长度（140 - 160个碱基对）的组分中回收。在消化的所有阶段，与19S加26S RNA杂交的DNA百分比在沉降较慢的单体峰A中比在任何其他染色质组分中都要高。峰A和单体颗粒在蛋白质含量和分布上有所不同。核糖体顺反子以改变的核小体构型存在可能与rDNA染色质功能状态的变化有关。
