title: Differential regulation of groESL operon expression in response to heat and light in Anabaena.
abstract: The HrcA protein is known to bind the cis-element CIRCE and repress expression of hsp60 in certain bacteria. However, recent data from cyanobacteria have seriously questioned the HrcA/CIRCE interaction paradigm. A hrcA null mutant showed constitutive expression of Hsp60 proteins [GroEL/Cpn60(GroEL2)], and an unexpected further increase in GroEL during temperature upshift, suggesting involvement of regulatory mechanisms other than HrcA in groESL expression in Anabaena. The negative regulation of both hsp60 genes [groEL and cpn60 (groEL2)] at CIRCE element was established by: (1) constitutive expression of Green Fluorescent Protein gene, tagged to Anabaena hsp60 promoters, in E. coli, and its repression upon co-expression of Anabaena HrcA and (2) specific binding of Anabaena HrcA to the CIRCE element. Deletion analysis of other cis-elements further distinguished (a) a photo-regulation by the K-box and (b) thermoregulation from a novel H-box, over and above the negative regulation by HrcA at CIRCE.
authors.affiliation: Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
authors.forename: Hema
authors.initials: H
authors.lastname: Rajaram
authors.forename: Shree Kumar
authors.initials: SK
authors.lastname: Apte
mesh_terms: D017033:Anabaena / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D018834:Chaperonin 60 / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006358:Hot Temperature; D008027:Light; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D009876:Operon; D011401:Promoter Regions, Genetic
chemical_list: D001426:Bacterial Proteins; D018834:Chaperonin 60; D004269:DNA, Bacterial; D049452:Green Fluorescent Proteins