The sigma B-dependent promoter of the Bacillus subtilis sigB operon is induced by heat shock.
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.
Benson
A K
AK
Department of Microbiology, University of Texas Health Science Center, San Antonio 78284-7758.
Haldenwang
W G
WG
D001412:Bacillus subtilis / Q000235:genetics*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D015152:Blotting, Northern; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics*; D006358:Hot Temperature; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012808:Sigma Factor / Q000096:biosynthesis / Q000235:genetics*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; C079011:SigB protein, Bacteria; D012808:Sigma Factor