Song C Z, Hanada K, Yano K, Maeda Y, Yamamoto K, Muramatsu M
Department of Biochemistry, University of Tokyo School of Medicine, Japan.
J Biol Chem. 1994 Oct 28;269(43):26976-81.
Mouse RNA polymerase I (or A) was purified from an ascites cell line MH134 to virtual homogeneity using a novel purification procedure and examined for subunit composition. In marked contrast to older purifications that reported 5-8 subunits, polymerase I was found to have 11 subunits with remarkable correspondence to those of yeasts. The cDNA encoding a 40-kDa subunit of this enzyme, designated RPA40, was isolated. It predicts a polypeptide of 355 amino acids (M(r) = 40,065) and is encoded by a single copy gene. Protein sequence analysis reveals that RPA40 is the homolog of yeast RPC40, having homology to alpha subunit of Escherichia coli RNA polymerase, yeast RPB3, and human RPB33 RNA polymerase II subunits. The high conservation of this subunit among distant eukaryotes and different RNA polymerases suggests functional importance of this protein as a core subunit.
利用一种新颖的纯化方法，从小鼠腹水细胞系MH134中纯化出了几乎达到纯品状态的小鼠RNA聚合酶I（或A），并对其亚基组成进行了检测。与以往报道有5 - 8个亚基的纯化方法形成显著对比的是，发现聚合酶I有11个亚基，与酵母的亚基有显著对应关系。分离出了编码该酶40 kDa亚基的cDNA，命名为RPA40。它预测有一个355个氨基酸的多肽（M(r)=40,065），由一个单拷贝基因编码。蛋白质序列分析表明，RPA40是酵母RPC40的同源物，与大肠杆菌RNA聚合酶的α亚基、酵母RPB3和人RNA聚合酶II的RPB33亚基具有同源性。该亚基在远缘真核生物和不同RNA聚合酶之间的高度保守性表明，这种蛋白质作为核心亚基具有重要的功能。
