THE SIGMA-B-DEPENDENT PROMOTER OF THE BACILLUS-SUBTILIS SIGB OPERON IS INDUCED BY HEAT-SHOCK
THE SIGMA-B-DEPENDENT PROMOTER OF THE BACILLUS-SUBTILIS SIGB OPERON IS INDUCED BY HEAT-SHOCK
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DOI：
10.1128/jb.175.7.1929-1935.1993
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发表时间：
1993-04-01
影响因子：
3.2
通讯作者：
HALDENWANG, WG
中科院分区：
文献类型：
--
作者：
BENSON, AK;HALDENWANG, WG
Sigma(B)是枯草芽孢杆菌的一种次要西格玛因子，当培养温度从37℃改变到48℃时，Sigma(B)增加了5到10倍。Western印迹(免疫印迹)分析中，针对SIGB操纵子产物RsbV、RsbW和sigma(B)的单抗被用来探测来自野生型和突变枯草杆菌菌株的提取物，发现这三种蛋白在热休克后都协调增加，并且这种增加依赖于sigma(B)，而不是RsbV，RsbV是依赖于sigma(B)的SIGB表达所必需的正调控因子。热休克后合成的RNA的核酸酶保护实验支持这样的观点，即向48℃的转变增强了SIGB操纵子的sigma(B)依赖启动子的转录。在Sigma(B)依赖的CTC启动子上启动的mRNA水平在热休克后也被认为增加了大约5-10倍。对转变到48摄氏度后合成的蛋白质的脉冲标记表明，SIGB野生型和突变株产生的主要热诱导蛋白的量相似；然而，在温度转变后，野生型菌株中至少存在7种额外的蛋白质，但在SIGB零突变体中不存在。因此，尽管Sigma(B)不是必需的热休克基因表达所必需的，但它被热休克激活以提高自身的合成，并可能促进其他几种热诱导蛋白的合成。
Sigma(B), a secondary sigma factor of Bacillus subtilis, was found to increase 5- to 10-fold when cultures were shifted from 37 to 48-degrees-C. Western blot (immunoblot) analyses, in which monoclonal antibodies specific for the sigB operon products RsbV, RsbW, and sigma(B) were used to probe extracts from wild-type and mutant B. subtilis strains, revealed that all three proteins increased coordinately after heat shock and that this increase was dependent on sigma(B) but not RsbV, a positive regulator normally essential for sigma(B)-dependent sigB expression. Nuclease protection experiments of RNA synthesized after heat shock supported the notion that the shift to 48-degrees-C enhanced transcription from the sigB operon's sigma(B)-dependent promoter. The level of mRNA initiating at the sigma(B)-dependent ctc promoter was also seen to increase approximately 5- to 10-fold after heat shock. Pulse-labeling of the proteins synthesized after a shift to 48-degrees-C demonstrated that sigB wild-type and mutant strains produced the major heat-inducible proteins in similar amounts; however, at least seven additional proteins were present after the temperature shift in the wild-type strain but absent in the sigB null mutant. Thus, although sigma(B) is not required for the expression of essential heat shock genes, it is activated by heat shock to elevate its own synthesis and possibly the synthesis of several other heat-inducible proteins.