Woychik N A, Young R A
Whitehead Institute for Biomedical Research, Nine Cambridge Center, Massachusetts 02142.
Mol Cell Biol. 1989 Jul;9(7):2854-9. doi: 10.1128/mcb.9.7.2854-2859.1989.
RPB4 encodes the fourth-largest RNA polymerase II subunit in Saccharomyces cerevisiae. The RPB4 gene was cloned and sequenced, and its identity was confirmed by amino acid sequence analysis of tryptic peptides from the purified subunit. The RPB4 DNA sequence predicted a protein of 221 amino acids with a molecular mass of 25,414 daltons. The central 100 amino acids of the RPB4 protein were found to be similar to a segment of the major sigma subunit in Escherichia coli RNA polymerase. Deletion of RPB4 produced cells that were heat and cold sensitive but could grow, albeit slowly, at intermediate temperatures. RNA polymerase II lacking the RPB4 subunit exhibited markedly reduced activity in crude extracts in vitro. The RPB4 subunit, although not essential for mRNA synthesis or enzyme assembly, was essential for normal levels of RNA polymerase II activity and indispensable for cell viability over a wide temperature range.
RPB4编码酿酒酵母中第四大的RNA聚合酶II亚基。克隆并测序了RPB4基因，并通过对纯化亚基的胰蛋白酶肽段进行氨基酸序列分析来确认其身份。RPB4 DNA序列预测出一种由221个氨基酸组成、分子量为25414道尔顿的蛋白质。发现RPB4蛋白的中央100个氨基酸与大肠杆菌RNA聚合酶中主要的σ亚基的一段序列相似。缺失RPB4会产生对热和冷敏感但在中等温度下仍能生长（尽管生长缓慢）的细胞。缺乏RPB4亚基的RNA聚合酶II在体外粗提物中表现出明显降低的活性。RPB4亚基虽然对于mRNA合成或酶组装不是必需的，但对于RNA聚合酶II活性的正常水平是必需的，并且在很宽的温度范围内对于细胞活力是不可或缺的。
