Download MendeleyStructural Basis for Virulence Activation of Francisella tularensis.
Travis, B.A., Ramsey, K.M., Prezioso, S.M., Tallo, T., Wandzilak, J.M., Hsu, A., Borgnia, M., Bartesaghi, A., Dove, S.L., Brennan, R.G., Schumacher, M.A.(2021) Mol Cell 81: 139
- PubMed: 33217319
- DOI: https://doi.org/10.1016/j.molcel.2020.10.035
- Primary Citation of Related Structures:
6WEG, 6WMP, 6WMR, 6WMT, 6WMU - PubMed Abstract:
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 σ 70 -associated RNAP holoenzyme (RNAPσ 70 ), 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 FtRNAPσ 70 -promoter-DNA, FtRNAPσ 70 -(MglA-SspA)-promoter DNA, and FtRNAPσ 70 -(MglA-SspA)-ppGpp-PigR-promoter DNA cryo-EM structures. Structural and genetic analyses show MglA-SspA facilitates σ 70 binding to DNA to regulate virulence and virulence-enhancing genes. Our Escherichia coli RNAPσ 70- homodimeric EcSspA structure suggests this is a general SspA-transcription regulation mechanism. Strikingly, our FtRNAPσ 70 -(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.
Organizational Affiliation:
Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA.
