title: Functional analysis of the heat shock regulator HrcA of Chlamydia trachomatis.
abstract: HrcA is a regulator of bacterial heat shock gene expression that binds to a cis-acting DNA element called CIRCE. It has been proposed that HrcA and CIRCE function as a repressor-operator pair. We have purified recombinant HrcA from the pathogenic bacterium Chlamydia trachomatis and have shown that it is a DNA-binding protein that functions as a negative regulator of transcription. HrcA bound specifically to the CIRCE element in a concentration-dependent manner. HrcA repressed the in vitro transcription of a chlamydial heat shock promoter, and this repression was promoter specific. HrcA-mediated repression appears to be dependent on the topological state of the promoter, as repression on a supercoiled promoter template was greater than that on a linearized template. These results provide direct support for the role of HrcA as a transcriptional repressor in bacteria. This is the first report of the in vitro reconstitution of transcriptional regulation in Chlamydia.
authors.affiliation: Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, California 92697-4025, USA.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Wilson
authors.forename: Ming
authors.initials: M
authors.lastname: Tan
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002692:Chlamydia trachomatis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004268:DNA-Binding Proteins; D004742:Enhancer Elements, Genetic / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D012097:Repressor Proteins; C063842:dnaK protein, E coli