title: Nickel-responsive regulation of two novel Helicobacter pylori NikR-targeted genes.
abstract: Nickel is an essential transition metal for the survival of Helicobacter pylori in the acidic human stomach. The nickel-responsive transcriptional regulator HpNikR is important for maintaining healthy cytosolic nickel concentrations through the regulation of multiple genes, but its complete regulon and role in nickel homeostasis are not well understood. To investigate potential gene targets of HpNikR, ChIP sequencing was performed using H. pylori grown at neutral pH in nickel-supplemented media and this experiment identified HPG27_866 (frpB2) and HPG27_1499 (ceuE). These two genes are annotated to encode a putative iron transporter and a nickel-binding, periplasmic component of an ABC transporter, respectively. In vitro DNA-binding assays revealed that HpNikR binds both gene promoter sequences in a nickel-responsive manner with affinities on the order of ∼10(-7) M. The recognition sites of HpNikR were identified and loosely correlate with the HpNikR pseudo-consensus sequence (TATTATT-N11-AATAATA). Quantitative PCR experiments revealed that HPG27_866 and HPG27_1499 are transcriptionally repressed following growth of H. pylori G27 in nickel-supplemented media, and that this response is dependent on HpNikR. In contrast, iron supplementation results in activation of HPG27_1499, but no impact on the expression of HPG27_866 was observed. Metal analysis of the Δ866 strain revealed that HPG27_866 has an impact on nickel accumulation. These studies demonstrate that HPG27_866 and HPG27_1499 are both direct targets of HpNikR and that HPG27_866 influences nickel uptake in H. pylori.
authors.affiliation: Department of Chemistry, University of Toronto, 80 St. George St., Toronto, ON, M5S 3H6, Canada. dzamble@chem.utoronto.ca.
authors.forename: M D
authors.initials: MD
authors.lastname: Jones
authors.forename: I
authors.initials: I
authors.lastname: Ademi
authors.forename: X
authors.initials: X
authors.lastname: Yin
authors.forename: Y
authors.initials: Y
authors.lastname: Gong
authors.forename: D B
authors.initials: DB
authors.lastname: Zamble
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D001483:Base Sequence; D001665:Binding Sites; D047369:Chromatin Immunoprecipitation; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000737:chemistry; D004269:DNA, Bacterial; D003850:Deoxyribonuclease I / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial; D016480:Helicobacter pylori / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008670:Metals / Q000737:chemistry; D008969:Molecular Sequence Data; D009532:Nickel / Q000737:chemistry*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012313:RNA / Q000737:chemistry; D012097:Repressor Proteins / Q000737:chemistry*; D012689:Sequence Homology, Nucleic Acid
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008670:Metals; C523724:NikR protein, Helicobacter pylori; D012097:Repressor Proteins; D012313:RNA; D009532:Nickel; D004247:DNA; D003850:Deoxyribonuclease I