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Alternate promoters direct stress-induced transcription of the Bacillus subtilis clpC operon

Abstract : clpC of Bacillus subtilis is part of an operon containing six genes. Northern blot analysis suggested that all genes are co-transcribed and encode stress-inducible proteins. Two promoters (PA and PB) were mapped upstream of the first gene. PA resembles promoters recognized by the vegetative RNA polymerase E sigma A. The other promoter (PB) was shown to be dependent on sigma B, the general stress sigma factor in B. subtilis, suggesting that clpC, a potential chaperone, is expressed in a sigma B-dependent manner. This is the first evidence that sigma B in B. subtilis is involved in controlling the expression of a gene whose counterpart, clpB, is subject to regulation by sigma 32 in Escherichia coli, indicating a new function of sigma B-dependent general stress proteins. PB deviated from the consensus sequence of sigma B promoters and was only slightly induced by starvation conditions. Nevertheless, strong induction by heat, ethanol, and salt stress occurred at the sigma B-dependent promoter, whereas the vegetative promoter was only weakly induced under these conditions. However, in a sigB mutant, the sigma A-like promoter became inducible by heat and ethanol stress, completely compensating for sigB deficiency. Only the downstream sigma A-like promoter was induced by certain stress conditions such as hydrogen peroxide or puromycin. These results suggest that novel stress-induction mechanisms are acting at a vegetative promoter. Involvement of additional elements in this mode of induction are discussed.
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Elke Krüger, Tarek Msadek, Michael Hecker. Alternate promoters direct stress-induced transcription of the Bacillus subtilis clpC operon. Molecular Microbiology, Wiley, 1996, 20 (4), pp.713-723. ⟨10.1111/j.1365-2958.1996.tb02511.x⟩. ⟨pasteur-02870342⟩



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