Fujita N, Nomura T, Ishihama A
J Biol Chem. 1987 Feb 5;262(4):1855-9.
An RNA polymerase holoenzyme containing sigma 32, the heat-shock sigma subunit, has been purified from heat-shocked Escherichia coli cells, and its functional properties including the promoter selectivity have been analyzed using the in vitro mixed transcription system. The holoenzyme correctly recognized a heat-shock promoter for the groE gene and efficiently initiated transcription at the same site as that found in vivo. The enzyme was, however, unable to recognize the promoters which are usually transcribed by the regular holoenzyme (E sigma 70), such as tufB, nusA, supP, lacUV5, araS, rpsA, recA, rplJ, dnaQ, rnh, and trp promoters. On the other hand, the regular holoenzyme did not recognize the groE promoter. These observations altogether indicate that strict difference exists in the promoter selectivity between two molecular species of the RNA polymerase holoenzyme. The groE transcription in vitro was not affected significantly within the temperature range from 32 to 42 degrees C. The two sigma subunits could be replaced in vitro on the same core enzyme, supporting the view that the spectrum of gene expression in E. coli is under a dynamic control by intracellular levels of individual sigma subunits.
一种含有热休克σ亚基σ32的RNA聚合酶全酶已从热休克的大肠杆菌细胞中纯化出来，并利用体外混合转录系统分析了其功能特性，包括启动子选择性。该全酶能正确识别groE基因的热休克启动子，并在与体内相同的位点高效启动转录。然而，该酶无法识别通常由常规全酶（Eσ70）转录的启动子，如tufB、nusA、supP、lacUV5、araS、rpsA、recA、rplJ、dnaQ、rnh和trp启动子。另一方面，常规全酶不能识别groE启动子。这些观察结果共同表明，两种RNA聚合酶全酶分子在启动子选择性上存在严格差异。体外groE转录在32至42摄氏度的温度范围内没有受到显著影响。两种σ亚基可以在体外同一核心酶上进行替换，这支持了大肠杆菌中基因表达谱受单个σ亚基细胞内水平动态控制的观点。
