PMID:9303302

Citation	Mogk, A, Homuth, G, Scholz, C, Kim, L, Schmid, FX and Schumann, W (1997) The GroE chaperonin machine is a major modulator of the CIRCE heat shock regulon of Bacillus subtilis. EMBO J. 16:4579-90
Abstract	Class I heat-inducible genes in Bacillus subtilis consist of the heptacistronic dnaK and the bicistronic groE operon and form the CIRCE regulon. Both operons are negatively regulated at the level of transcription by the HrcA repressor interacting with its operator, the CIRCE element. Here, we demonstrate that the DnaK chaperone machine is not involved in the regulation of HrcA and that the GroE chaperonin exerts a negative effect in the post-transcriptional control of HrcA. When expression of the groE operon was turned off, the dnaK operon was significantly activated and large amounts of apparently inactive HrcA repressor were produced. Overproduction of GroEL, on the other hand, resulted in decreased expression of the dnaK operon. Introduction of the hrcA gene and its operator into Escherichia coli was sufficient to elicit a transient heat shock response, indicating that no additional Bacillus-specific gene(s) was needed. As in B. subtilis, the groEL gene of E. coli negatively influenced the activity of HrcA. HrcA could be overproduced in E. coli, but formed inclusion bodies which could be dissolved in 8 M urea. Upon removal of urea, HrcA had a strong tendency to aggregate, but aggregation could be suppressed significantly by the addition of GroEL. Purified HrcA repressor was able specifically to retard a DNA fragment containing the CIRCE element, and the amount of retarded DNA was increased significantly in the presence of GroEL. These results suggest that the GroE chaperonin machine modulates the activity of the HrcA repressor and therefore point to a novel function of GroE as a modulator of the heat shock response.
Links	PubMed PMC1170084 Online version:10.1093/emboj/16.15.4579
Keywords	Bacillus subtilis/genetics; Bacillus subtilis/metabolism; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Chaperonin 10/genetics; Chaperonin 10/metabolism; Chaperonin 60/genetics; Chaperonin 60/metabolism; Chaperonins; DNA, Bacterial/genetics; DNA, Bacterial/metabolism; DNA-Binding Proteins; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins; Genes, Bacterial; HSP40 Heat-Shock Proteins; HSP70 Heat-Shock Proteins/genetics; HSP70 Heat-Shock Proteins/metabolism; Heat-Shock Proteins/genetics; Heat-Shock Proteins/metabolism; Hot Temperature; Molecular Chaperones/genetics; Molecular Chaperones/metabolism; Mutation; Operon; Regulon; Repressor Proteins/genetics; Repressor Proteins/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BACSU:CH60		GO:0006457: protein folding	ECO:0000314:		P		Figure 8	complete

References

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