Two types of localization of the DNA-binding proteins within the Escherichia coli nucleoid
Two types of localization of the DNA-binding proteins within the Escherichia coli nucleoid
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DOI：
10.1046/j.1365-2443.2000.00350.x
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发表时间：
2000-08-01
期刊：
影响因子：
2.1
通讯作者：
Ishihama, A
中科院分区：
文献类型：
--
作者：
Azam, TA;Hiraga, S;Ishihama, A
背景资料：大肠杆菌的基因组DNA通过几种DNA结合蛋白的结合折叠成核小体样结构，通常称为类核。我们以前测定了12种大肠杆菌DNA结合的特异性和亲和力。coli DNA结合蛋白，以及它们在不同生长阶段的细胞内浓度。这些蛋白在大肠杆菌中的胞内定位。大肠杆菌可以预测从这些数据，但没有尝试，迄今已取得直接观察细胞内分布的DNA结合proteins.Results：细胞内定位在大肠杆菌中的10种的核相关蛋白，三个组成部分的转录器，和三个组成部分的翻译机器进行了研究，通过间接免疫荧光显微镜。DNA结合蛋白可分为两类。I组蛋白，包括主要的类核结构蛋白，H-NS，HU，IHF，StpA和Dps，均匀分布在整个类核内。相反，被认为具有DNA功能调节活性的II组蛋白质在类核内的特定位点积累，形成2（SeqA）、3-4（CbpA和CbpB）和6-10（Fis和IciA）免疫染色点。每个免疫染色点可以代表在基因组DNA的特定位点处的每种DNA结合蛋白的一百到一千个分子的缔合，或者来自折叠基因组的不同结构域的蛋白质缔合DNA片段的组装。RNA聚合酶核心酶和sigma（70）亚基主要与类核相关，但anti-sigma（70）因子（Rsd）似乎积聚在稳定期细胞中类核和胞质溶胶之间的边界处。结果表明，Hfq主要存在于细胞质中，同时存在的还有核糖体蛋白L7/L12和RME。大肠杆菌可分为两类。一组蛋白质均匀分布在类核内，而另一组蛋白质呈不规则分布，形成免疫染色斑点或团块。
Background: The genome DNA of Escherichia coli is folded into the nucleosome-like structure, often called a nucleoid, by the binding of several DNA-binding proteins. We previously determined the specificity and affinity of DNA-binding for 12 species of the E. coli DNA-binding protein, and their intracellular concentrations at various growth phases. The intracellular localization of these proteins in E. coli could be predicted from these data, but no attempt;has been made thus far to directly observe the intracellular distribution of the DNA-binding proteins.Results: The intracellular localization in Escherichia coli of 10 species of the nucleoid-associated protein, three components of the transcription apparatus, and three components of the translation machinery was investigated by indirect immune-fluorescence microscopy. The DNA-binding proteins could be classified into two groups. The group-I proteins, including the major nucleoid-structural proteins, H-NS, HU, IHF, StpA and Dps, are distributed uniformly within the entire nucleoid. In contrast, the group-II proteins, which are presumed to possess regulatory activities of DNA functions accumulate at specific loci within the nucleoid, forming 2 (SeqA), 3-4 (CbpA and CbpB) and 6-10 (Fis and IciA) immune-stained dots. Each immunostained dot may represent either the association of a hundred to one thousand molecules of each DNA-binding protein at a specific locus of the genome DNA or the assembly of protein-associated DNA segments from different domains of the folded genome. Both the RNA polymerase core enzyme and the sigma(70) subunit are mainly associated with the nucleoid, but the anti-sigma(70) factor (Rsd) appears to be accumulated at the boundary between the nucleoid and the cytosol in the stationary-phase cells. Here we show that the majority of Hfq is present in cytoplasm together with ribosomal proteins L7/L12 and RME.Conclusion: The DNA-binding proteins of E. coli could be classified into two groups. One group proteins was distributed uniformly within the nucleoid, but the other group of proteins showed an irregular distribution, forming immune-stained spots or clumps.