title: Insights into the complex regulation of rpoS in Borrelia burgdorferi.
abstract: Co-ordinated regulation of gene expression is required for the transmission and survival of Borrelia burgdorferi in different hosts. The sigma factor RpoS (sigma(S)), as regulated by RpoN (sigma(54)), has been shown to regulate key virulence factors (e.g. OspC) required for these processes. As important, multiple signals (e.g. temperature, pH, cell density, oxygen) have been shown to increase the expression of sigma(S)-dependent genes; however, little is known about the signal transduction mechanisms that modulate the expression of rpoS. In this report we show that: (i) rpoS has a sigma(54)-dependent promoter that requires Rrp2 to activate transcription; (ii) Rrp2Delta123, a constitutively active form of Rrp2, activated sigma(54)-dependent transcription of rpoS/P-lacZ reporter constructs in Escherichia coli; (iii) quantitative reverse transcription polymerase chain reaction (QRT-PCR) experiments with reporter cat constructs in B. burgdorferi indicated that Rrp2 activated transcription of rpoS in an enhancer-independent fashion; and finally, (iv) rpoN is required for cell density- and temperature-dependent expression of rpoS in B. burgdorferi, but histidine kinase Hk2, encoded by the gene immediately upstream of rrp2, is not essential. Based on these findings, a model for regulation of rpoS has been proposed which provides mechanisms for multiple signalling pathways to modulate the expression of the sigma(S) regulon in B. burgdorferi.
authors.affiliation: Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA.
authors.forename: Mary N
authors.initials: MN
authors.lastname: Burtnick
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Downey
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Brett
authors.forename: Julie A
authors.initials: JA
authors.lastname: Boylan
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Frye
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Hoover
authors.forename: Frank C
authors.initials: FC
authors.lastname: Gherardini
mesh_terms: D000942:Antigens, Bacterial / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D025065:Borrelia burgdorferi / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D000071677:Histidine Kinase; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000378:metabolism; D051877:RNA Polymerase Sigma 54 / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics*; D013696:Temperature; D015534:Trans-Activators / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C079616:OspC protein; D012808:Sigma Factor; D015534:Trans-Activators; C069567:sigma factor KatF protein, Bacteria; D011494:Protein Kinases; D000071677:Histidine Kinase; D051877:RNA Polymerase Sigma 54