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J Mol Biol. 2011 Jun 24;409(5):692-709. doi: 10.1016/j.jmb.2011.04.017. Epub 2011 Apr 22.

Different requirements for σ Region 4 in BvgA activation of the Bordetella pertussis promoters P(fim3) and P(fhaB).

Author information

1
Gene Expression and Regulation Section, Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.

Abstract

Bordetella pertussis BvgA is a global response regulator that activates virulence genes, including adhesin-encoding fim3 and fhaB. At the fhaB promoter, P(fhaB), a BvgA binding site lies immediately upstream of the -35 promoter element recognized by Region 4 of the σ subunit of RNA polymerase (RNAP). We demonstrate that σ Region 4 is required for BvgA activation of P(fhaB), a hallmark of Class II activation. In contrast, the promoter-proximal BvgA binding site at P(fim3) includes the -35 region, which is composed of a tract of cytosines that lacks specific sequence information. We demonstrate that σ Region 4 is not required for BvgA activation at P(fim3). Nonetheless, Region 4 mutations that impair its typical interactions with core and with the -35 DNA affect P(fim3) transcription. Hydroxyl radical cleavage using RNAP with σD581C-FeBABE positions Region 4 near the -35 region of P(fim3); cleavage using RNAP with α276C-FeBABE or α302C-FeBABE also positions an α subunit C-terminal domain within the -35 region, on a different helical face from the promoter-proximal BvgA~P dimer. Our results suggest that the -35 region of P(fim3) accommodates a BvgA~P dimer, an α subunit C-terminal domain, and σ Region 4. Molecular modeling suggests how BvgA, σ Region 4, and α might coexist within this DNA in a conformation that suggests a novel mechanism of activation.

PMID:
21536048
PMCID:
PMC3141349
DOI:
10.1016/j.jmb.2011.04.017
[Indexed for MEDLINE]
Free PMC Article

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