Parish R W, Schmidlin S
Nucleic Acids Res. 1985 Jan 11;13(1):15-30. doi: 10.1093/nar/13.1.15.
Mononucleosomes released from Dictyostelium discoideum chromatin by micrococcal nuclease contained two distinctive DNA sizes (166-180 and 146 bp). Two dimensional gel electrophoresis suggested a lysine-rich protein protected the larger mononucleosomes from nuclease digestion. This was confirmed by stripping the protein from chromatin with Dowex resin. Subsequently, only the 146 bp mononucleosome was produced by nuclease digestion. Reconstitution of the stripped chromatin with the purified lysine-rich protein resulted in the reappearance of the larger mononucleosomes. Two-dimensional gel electrophoresis showed the protein was associated with mononucleosomes. Hence, the protein functions as an H1 histone in bringing the two DNA strands together at their exit point from the nucleosome. Trypsin digestion of the lysine-rich protein in nuclei resulted in a limiting peptide of approx. 10 kilodaltons. Trypsin concentrations which degraded the protein to peptides of 12-14 kilodaltons and partially degraded the core histones did not change the DNA digestion patterns obtained with micrococcal nuclease. Thus, the trypsin-resistant domain of the lysine-rich protein is able to maintain chromatosome structure.
用微球菌核酸酶从盘基网柄菌染色质中释放出的单核小体含有两种不同大小的DNA（166 - 180和146 bp）。二维凝胶电泳表明，一种富含赖氨酸的蛋白质保护较大的单核小体不被核酸酶消化。用Dowex树脂从染色质中去除该蛋白质证实了这一点。随后，核酸酶消化仅产生146 bp的单核小体。用纯化的富含赖氨酸的蛋白质重建去除蛋白质的染色质，导致较大的单核小体重新出现。二维凝胶电泳表明该蛋白质与单核小体相关。因此，该蛋白质在使两条DNA链在其从核小体的出口点处结合在一起时起到H1组蛋白的作用。用胰蛋白酶消化细胞核中富含赖氨酸的蛋白质产生了一个约10千道尔顿的限制性肽段。将该蛋白质降解为12 - 14千道尔顿肽段并部分降解核心组蛋白的胰蛋白酶浓度并未改变用微球菌核酸酶获得的DNA消化模式。因此，富含赖氨酸的蛋白质的抗胰蛋白酶结构域能够维持染色小体结构。
