Seputiene Vaida, Suziedelis Kestutis, Normark Staffan, Melefors Ojar, Suziedeliene Edita
Department of Biochemistry and Biophysics, Faculty of Natural Sciences, Vilnius University, Vilnius 2009, Lithuania.
Res Microbiol. 2004 Sep;155(7):535-42. doi: 10.1016/j.resmic.2004.03.010.
We show here that transcription of the asr gene in Escherichia coli, Salmonella enterica serovar Typhimurium, Klebsiella pneumoniae and Enterobacter cloacae is strongly dependent on the acidification level of the growth medium, with maximal induction at pH 4.0-4.5 as determined by Northern hybridization analysis. Previous gene array analyses have also shown that asr is the most acid-induced gene in the E. coli genome. Sequence alignment of the asr promoters from different enterobacterial species identified a highly conserved region located at position -70 to -30 relative to the asr transcriptional start site. By deletion of various segments of this region in the E. coli asr promoter it was shown that sequences upstream from the -40 position were important for induction. Transcription from the E. coli asr promoter was demonstrated to be growth-phase-dependent and to require the alternative sigma factor RpoS (sigma(S)) in stationary phase. Transcription of the asr gene was also found to be subject to negative control by the nucleoid protein H-NS.
我们在此表明，在大肠杆菌、鼠伤寒沙门氏菌、肺炎克雷伯菌和阴沟肠杆菌中，asr基因的转录强烈依赖于生长培养基的酸化水平，通过Northern杂交分析确定，在pH 4.0 - 4.5时诱导作用最强。先前的基因芯片分析也表明，asr是大肠杆菌基因组中酸诱导最强的基因。对不同肠杆菌属物种的asr启动子进行序列比对，确定了一个相对于asr转录起始位点位于-70至-30位置的高度保守区域。通过缺失大肠杆菌asr启动子中该区域的各个片段，结果表明-40位置上游的序列对诱导作用很重要。已证明大肠杆菌asr启动子的转录依赖于生长阶段，并且在稳定期需要替代的σ因子RpoS（σS）。还发现asr基因的转录受到类核蛋白H-NS的负调控。
