![Journal cover image](https://secure.syndetics.com/index.aspx?isbn=/lc.gif&issn=1097-4164&client=dukeuniv)
Structural Basis for Virulence Activation of Francisella tularensis.
The bacterium Francisella tularensis (Ft) is one of the most infectious agents known. Ft virulence is controlled by a unique combination of transcription regulators: the MglA-SspA heterodimer, PigR, and the stress signal, ppGpp. MglA-SspA assembles with the σ70-associated RNAP holoenzyme (RNAPσ70), forming a virulence-specialized polymerase. These factors activate Francisella pathogenicity island (FPI) gene expression, which is required for virulence, but the mechanism is unknown. Here we report FtRNAPσ70-promoter-DNA, FtRNAPσ70-(MglA-SspA)-promoter DNA, and FtRNAPσ70-(MglA-SspA)-ppGpp-PigR-promoter DNA cryo-EM structures. Structural and genetic analyses show MglA-SspA facilitates σ70 binding to DNA to regulate virulence and virulence-enhancing genes. Our Escherichia coli RNAPσ70-homodimeric EcSspA structure suggests this is a general SspA-transcription regulation mechanism. Strikingly, our FtRNAPσ70-(MglA-SspA)-ppGpp-PigR-DNA structure reveals ppGpp binding to MglA-SspA tethers PigR to promoters. PigR in turn recruits FtRNAP αCTDs to DNA UP elements. Thus, these studies unveil a unique mechanism for Ft pathogenesis involving a virulence-specialized RNAP that employs two (MglA-SspA)-based strategies to activate virulence genes.
Duke Scholars
Altmetric Attention Stats
Dimensions Citation Stats
Published In
DOI
EISSN
Publication Date
Volume
Issue
Start / End Page
Location
Related Subject Headings
- Virulence Factors
- Sigma Factor
- Promoter Regions, Genetic
- Francisella tularensis
- Escherichia coli
- Developmental Biology
- DNA-Directed RNA Polymerases
- 42 Health sciences
- 32 Biomedical and clinical sciences
- 31 Biological sciences
Citation
![Journal cover image](https://secure.syndetics.com/index.aspx?isbn=/lc.gif&issn=1097-4164&client=dukeuniv)
Published In
DOI
EISSN
Publication Date
Volume
Issue
Start / End Page
Location
Related Subject Headings
- Virulence Factors
- Sigma Factor
- Promoter Regions, Genetic
- Francisella tularensis
- Escherichia coli
- Developmental Biology
- DNA-Directed RNA Polymerases
- 42 Health sciences
- 32 Biomedical and clinical sciences
- 31 Biological sciences