DISTRIBUTION OF PROTEINS AMONG CHROMATIN COMPONENTS OF NUCLEOLI
DISTRIBUTION OF PROTEINS AMONG CHROMATIN COMPONENTS OF NUCLEOLI
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DOI：
10.1021/bi00282a023
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发表时间：
1983-01-01
期刊：
影响因子：
2.9
通讯作者：
THOMPSON, BA
中科院分区：
文献类型：
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作者：
OLSON, MOJ;THOMPSON, BA
核仁含有蛋白质，据信这些蛋白质参与其子成分的组织。为了检查这些蛋白质的可能位置，研究了微球菌核酸酶、DNase I 和 RNase A 消化 Novikoff 肝癌核仁时蛋白质和染色质亚基的释放。核仁的微球菌核酸酶消化产生典型的核小体蔗糖密度梯度曲线，显示单体、二聚体和三聚体的分离。单体、二聚体和三聚体的 DNA 长度与之前报道的各种大鼠组织的全核染色质的 DNA 长度基本相同。蛋白质 C23（分子量 110,000）是一种假定的核仁组织蛋白，含有高酸性磷酸化区域，可被微球菌核酸酶快速释放。微球菌核酸酶释放的大部分（约 90%）蛋白质 C23 沉积速度比单核小体更慢，约为 7S。蛋白质 C23 的剩余部分在不同消化程度下与单核小体、二核小体和三核小体一起沉积。 DNase I 还从核仁中释放蛋白质 C23。用核糖核酸酶 A 处理核仁释放大量蛋白质 C23，但不释放组蛋白。蛋白 C23 可能与含 DNA 和 RNA 的成分相关，但该蛋白的主要部分松散结合或与 RNP [核糖核蛋白] 成分相关。它可能以较小但重要的程度存在于核小体中。蛋白质 B23（分子量 37,000）也含有高酸性磷酸化区域，所有核酸酶处理都会释放该蛋白，但在核小体组分中发现程度较低。另一种分子量为 160,000 (160 K) 的蛋白质与二核小体和三核小体一起沉积，与全核染色质相比，其在核仁中的浓度更高。 DNase I 消化核仁，然后用 2 M NaCl 提取后，160 K 蛋白质主要存在于沉淀中，表明它是核基质的核仁成分。
The nucleolus contains proteins which are believed to be involved in the organization of its subcomponents. To examine the possible locations of these proteins, the release of proteins and chromatin subunits by digestion of Novikoff hepatoma nucleoli by micrococcal nuclease, DNase I and RNase A was studied. Micrococcal nuclease digests of nucleoli produced typical sucrose density gradient profiles of nucleosomes showing separation of monomers, dimers and trimers. The DNA lengths in the monomers, dimers and trimers were generally the same as previously reported for whole nuclear chromatin of various rat tissues. Protein C23 (MW 110,000), a putative nucleolus organizer protein which contains highly acidic phosphorylated regions, was rapidly released by micrococcal nuclease. The bulk (.apprx. 90%) of protein C23 released by micrococcal nuclease sedimented more slowly than mononucleosomes, at approximately 7S. The remaining portion of protein C23 sedimented with mono-, di- and trinucleosomes at various extents of digestion. DNase I also liberated protein C23 from nucleoli. Treatment of nucleoli with ribonuclease A released significant quantities of protein C23 without release of histones. Protein C23 may be associated with DNA-containing as well as RNA-containing components but the major portion of the protein is loosely bound or associated with RNP [ribonucleoprotein] components. It may be present in nucleosomes to a small but significant extent. Protein B23 (MW 37,000), which also contains highly acidic phosphorylated regions, was released by all nuclease treatments but was found to a lesser extent in nucleosome fractions. Another protein of MW 160,000 (160 K) sedimented with di- and trinucleosomes and was present in higher concentrations in nucleolar compared to whole nuclear chromatin. The 160 K protein was found predominantly in the pellet after DNase I digestion of nucleoli followed by extraction with 2 M NaCl, suggesting that it is a nucleolar component of the nuclear matrix.