title: SigCH, an extracytoplasmic function sigma factor of Porphyromonas gingivalis regulates the expression of cdhR and hmuYR.
abstract: Extracytoplasmic function (ECF) sigma factors play an important role in the bacterial response to various environmental stresses. Porphyromonas gingivalis, a prominent etiological agent in human periodontitis, possesses six putative ECF sigma factors. So far, information is limited on the ECF sigma factor, PGN_0319. The aim of this study was to investigate the role of PGN_0319 (SigCH) of P. gingivalis, focusing on the regulation of hmuY and hmuR, which encode outer-membrane proteins involved in hemin utilization, and cdhR, a transcriptional regulator of hmuYR. First, we evaluated the gene expression profile of the sigCH mutant by DNA microarray. Among the genes with altered expression levels, those involved in hemin utilization were downregulated in the sigCH mutant. To verify the microarray data, quantitative reverse transcription PCR analysis was performed. The RNA samples used were obtained from bacterial cells grown to early-log phase, in which sigCH expression in the wild type was significantly higher than that in mid-log and late-log phases. The expression levels of hmuY, hmuR, and cdhR were significantly decreased in the sigCH mutant compared to wild type. Transcription of these genes was restored in a sigCH complemented strain. Compared to the wild type, the sigCH mutant showed reduced growth in log phase under hemin-limiting conditions. Electrophoretic mobility shift assays showed that recombinant SigCH protein bound to the promoter region of hmuY and cdhR. These results suggest that SigCH plays an important role in the early growth of P. gingivalis, and directly regulates cdhR and hmuYR, thereby playing a potential role in the mechanisms of hemin utilization by P. gingivalis.
authors.affiliation: Department of Periodontology, Tokyo Dental College, Tokyo, Japan; Oral Health Science Center, Tokyo Dental College, Tokyo, Japan.
authors.forename: Koki
authors.initials: K
authors.lastname: Ota
authors.affiliation: Oral Health Science Center, Tokyo Dental College, Tokyo, Japan; Department of Microbiology, Tokyo Dental College, Tokyo, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Kikuchi
authors.affiliation: Department of Periodontology, Tokyo Dental College, Tokyo, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Imamura
authors.affiliation: Department of Periodontology, Tokyo Dental College, Tokyo, Japan.
authors.forename: Daichi
authors.initials: D
authors.lastname: Kita
authors.affiliation: Department of Periodontology, Tokyo Dental College, Tokyo, Japan.
authors.forename: Kouki
authors.initials: K
authors.lastname: Yoshikawa
authors.affiliation: Department of Periodontology, Tokyo Dental College, Tokyo, Japan; Oral Health Science Center, Tokyo Dental College, Tokyo, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Saito
authors.affiliation: Oral Health Science Center, Tokyo Dental College, Tokyo, Japan; Department of Microbiology, Tokyo Dental College, Tokyo, Japan. Electronic address: ishihara@tdc.ac.jp.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Ishihara
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006427:Hemin / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D009876:Operon; D010518:Periodontitis / Q000382:microbiology*; D016966:Porphyromonas gingivalis / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D011994:Recombinant Proteins; D012808:Sigma Factor; D006427:Hemin
keywords: ECF sigma factor; Hemin utilization; Porphyromonas gingivalis; cdhR; hmuR; hmuY