EXPRESSION OF CLPB, AN ANALOG OF THE ATP-DEPENDENT PROTEASE REGULATORY SUBUNIT IN ESCHERICHIA-COLI, IS CONTROLLED BY A HEAT-SHOCK SIGMA-FACTOR (SIGMA-32)
EXPRESSION OF CLPB, AN ANALOG OF THE ATP-DEPENDENT PROTEASE REGULATORY SUBUNIT IN ESCHERICHIA-COLI, IS CONTROLLED BY A HEAT-SHOCK SIGMA-FACTOR (SIGMA-32)
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DOI：
10.1128/jb.173.14.4247-4253.1991
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发表时间：
1991-07-01
影响因子：
3.2
通讯作者：
YURA, T
中科院分区：
文献类型：
--
作者：
KITAGAWA, M;WADA, C;YURA, T
大肠杆菌K-12产生至少两种atp依赖性蛋白酶，Lon （La）和Clp (Ti)，后者由一个调节亚基（ClpA）和一个蛋白水解亚基（ClpP）组成。在大肠杆菌染色体上发现了编码ClpA类似物的基因clpB。通过对新型热休克启动子的克隆和检测，我们鉴定出了一个主要的clpB启动子，该启动子是由热休克因子sigma-32 （rpoH [= htpR]基因产物）特异性控制的。PclpB-lacZ操纵子融合合成β -半乳糖苷酶在温度从30℃转变到42℃时被短暂诱导，诱导依赖于rpoH功能。当温度升高时，染色体clpB转录本也增加，而在rpoH缺失菌株中完全不存在clpB转录本。在体外转录实验中，clpB启动子被RNA聚合酶sigma-32特异性识别和转录。核苷酸测序和mRNA起始位点的测定使我们确定了位于clpB编码序列上游的一个主要热休克启动子。结果清楚地表明，clpB的表达受sigma-32的直接控制。由于ClpP最近被证明是一种依赖于sigma-32的热休克蛋白，因此目前的发现表明，一种潜在的atp依赖蛋白酶ClpB-ClpP复合物可能在大肠杆菌中抗热应激中起重要作用。
Escherichia coli K-12 produces at least two ATP-dependent proteases, Lon (La) and Clp (Ti), the latter consisting of a regulatory subunit (ClpA) and a proteolytic subunit (ClpP). The gene clpB encoding an analog of ClpA had been found at 57 min on the E. coli chromosome. Cloning and examination of novel heat shock promoters led us to identify a major clpB promoter specifically controlled by a heat shock sigma-factor, sigma-32 (the rpoH [= htpR] gene product). Beta-Galactosidase synthesis from a PclpB-lacZ operon fusion was transiently induced upon temperature shift from 30 to 42-degrees-C, and the induction depended on the rpoH function. Chromosomal clpB transcripts also increased upon temperature upshift and were totally absent in the rpoH deletion strain. In the in vitro transcription experiments, the clpB promoter was specifically recognized and transcribed by RNA polymerase-sigma-32. Nucleotide sequencing and determination of mRNA start sites permitted us to identify a major heat shock promoter located upstream of the clpB coding sequence. The results clearly indicate that clpB expression is under direct control of sigma-32. Since ClpP was recently shown to be a sigma-32-dependent heat shock protein, the present finding suggests the possibility that a potential ATP-dependent protease, ClpB-ClpP complex, plays an important role against thermal stress in E. coli.