Role of HrcA and CIRCE in the Heat Shock Regulatory Network of Bradyrhizobium japonicum
| Autor: | Franz Narberhaus, Hauke Hennecke, Hans-Martin Fischer, Alexander C. Minder |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2000 |
| Předmět: |
Transcription
Genetic Operon Molecular Sequence Data Repressor Genetics and Molecular Biology Sigma Factor Regulatory Sequences Nucleic Acid Microbiology Bacterial Proteins Sigma factor Heat shock protein Chaperonin 10 Bradyrhizobium Heat shock Cloning Molecular Symbiosis Molecular Biology Heat-Shock Proteins Genetics biology Promoter Gene Expression Regulation Bacterial Sequence Analysis DNA biology.organism_classification Recombinant Proteins Cell biology DNA-Binding Proteins Repressor Proteins Regulon Phenotype Gene Deletion Heat-Shock Response Bradyrhizobium japonicum Transcription Factors |
| Popis: | A large number of bacteria regulate chaperone gene expression by the CIRCE-HrcA system in which a DNA element called CIRCE serves as binding site for the repressor protein HrcA under non-heat-shock conditions. We have cloned the two consecutive genes hrcA and grpE of Bradyrhizobium japonicum by using a complementation approach that screened for GrpE function. In vivo and in vitro transcript mapping demonstrated that both genes are transcribed separately from RpoH (ς 32 )-dependent promoters. To investigate the supposed negative regulatory function of HrcA, we compared the expression of putative target genes in the wild type with that in an hrcA mutant. Transcription of the CIRCE-associated chaperonin operons groESL 4 and groESL 5 , as well as the β-galactosidase activity derived from corresponding groE-lacZ fusions, was strongly elevated in the hrcA mutant even at physiological temperatures. Expression of other heat shock regulons (RpoH or ROSE dependent) was not affected. To study the activity of HrcA in vitro, we purified a histidine-tagged version of the protein under nondenaturing conditions. Specific binding to the CIRCE element was obtained with a soluble fraction of HrcA in gel retardation experiments. |
| Databáze: | OpenAIRE |
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