title: Chlamydial GroEL autoregulates its own expression through direct interactions with the HrcA repressor protein.
abstract: In the pathogenic bacterium Chlamydia trachomatis, a transcriptional repressor, HrcA, regulates the major heat shock operons, dnaK and groE. Cellular stress causes a transient increase in transcription of these heat shock operons through relief of HrcA-mediated repression, but the pathway leading to derepression is unclear. Elevated temperature alone is not sufficient, and it is hypothesized that additional chlamydial factors play a role. We used DNA affinity chromatography to purify proteins that interact with HrcA in vivo and identified a higher-order complex consisting of HrcA, GroEL, and GroES. This endogenous HrcA complex migrated differently than recombinant HrcA, but the complex could be disrupted, releasing native HrcA that resembled recombinant HrcA. In in vitro assays, GroEL increased the ability of HrcA to bind to the CIRCE operator and to repress transcription. Other chlamydial heat shock proteins, including the two additional GroEL paralogs present in all chlamydial species, did not modulate HrcA activity.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697-4025, USA.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Wilson
authors.forename: Christine C
authors.initials: CC
authors.lastname: Wu
authors.forename: John R
authors.initials: JR
authors.lastname: Yates
authors.forename: Ming
authors.initials: M
authors.lastname: Tan
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D018835:Chaperonin 10 / Q000378:metabolism; D018834:Chaperonin 60 / Q000096:biosynthesis / Q000378:metabolism*; D002692:Chlamydia trachomatis / Q000235:genetics* / Q000378:metabolism; D002846:Chromatography, Affinity; D004268:DNA-Binding Proteins / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial; D013058:Mass Spectrometry; D009875:Operator Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D018835:Chaperonin 10; D018834:Chaperonin 60; D004268:DNA-Binding Proteins; D012097:Repressor Proteins