title: Co-regulation by bent DNA. Functional substitutions of the integration host factor site at sigma 54-dependent promoter Pu of the upper-TOL operon by intrinsically curved sequences.
abstract: The role of integration host factor (IHF) in the regulation of the sigma 54-dependent promoter Pu of the TOL plasmid of Pseudomonas putida has been examined. We have selected in vivo insertions of intrinsically curved DNA that restore the responsiveness of an IHF-binding site deletion variant of Pu to the cognate activator of the system, XylR. We found five Pu derivatives which had inserted a core sequence with 6 phased [A]6 tracts, flanked by different lengths of DNA at the location of the former IHF site. They displayed 40-100% of the activity of Pu, were independent of IHF, and maintained the overall geometry of the wild-type promoter. The induction patterns of Pu, compared to those of hybrid promoters, were virtually indistinguishable. This supports the notion that, in native conditions, IHF co-regulates the system by providing a structural aid for promoter architecture and not by interacting directly with the RNA polymerase, as it has been suggested with other known IHF-dependent promoters.
authors.affiliation: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Pérez-Martín
authors.forename: K N
authors.initials: KN
authors.lastname: Timmis
authors.forename: V
authors.initials: V
authors.lastname: de Lorenzo
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D004269:DNA, Bacterial / Q000737:chemistry* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli; D005838:Genotype; D034982:Integration Host Factors; D008961:Models, Structural; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009876:Operon; D010641:Phenotype; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D016958:Pseudomonas putida / Q000235:genetics* / Q000378:metabolism; D015183:Restriction Mapping; D017384:Sequence Deletion; D012808:Sigma Factor / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D034982:Integration Host Factors; D012808:Sigma Factor; C440503:integration host factor, Pseudomonas