Alternate promoters direct stress-induced transcription of the Bacillus subtilis clpC operon.
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.
Krüger
E
E
Institut für Mikrobiologie und Molekularbiologie, Ernst-Moritz-Arndt-Universität, Greifswald, Germany.
Msadek
T
T
Hecker
M
M
D001345:Autoradiography; D001412:Bacillus subtilis / Q000235:genetics*; D001483:Base Sequence; D015152:Blotting, Northern; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009876:Operon; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011691:Puromycin / Q000494:pharmacology; D012333:RNA, Messenger / Q000737:chemistry; D014158:Transcription, Genetic
D012333:RNA, Messenger; D011691:Puromycin; D006861:Hydrogen Peroxide