| Literature DB >> 33217319 |
Brady A Travis1, Kathryn M Ramsey2, Samantha M Prezioso3, Thomas Tallo3, Jamie M Wandzilak4, Allen Hsu5, Mario Borgnia5, Alberto Bartesaghi6, Simon L Dove7, Richard G Brennan8, Maria A Schumacher9.
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 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.Entities:
Keywords: Cryo-EM; Francisella tularensis; MglA-SspA; PigR; RNA polymerase; pathogenicity island; ppGpp; transcription; αCTD; σ70
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Year: 2020 PMID： 33217319 PMCID： PMC7959165 DOI： 10.1016/j.molcel.2020.10.035
Source DB: PubMed Journal: Mol Cell ISSN： 1097-2765 Impact factor: 17.970