Article

Secreted transcription factor controls Mycobacterium tuberculosis virulence.

Department of Microbiology and Immunology, Program in Microbial Pathogenesis and Host Defense, University of California, San Francisco, 600 16th Street, Campus Box 2200, San Francisco, California 94143-2200, USA.
Nature (Impact Factor: 42.35). 09/2008; 454(7205):717-21.
Source: PubMed

ABSTRACT Bacterial pathogens trigger specialized virulence factor secretion systems on encountering host cells. The ESX-1 protein secretion system of Mycobacterium tuberculosis-the causative agent of the human disease tuberculosis-delivers bacterial proteins into host cells during infection and is critical for virulence, but how it is regulated is unknown. Here we show that EspR (also known as Rv3849) is a key regulator of ESX-1 that is required for secretion and virulence in mice. EspR activates transcription of an operon that includes three ESX-1 components, Rv3616c-Rv3614c, whose expression in turn promotes secretion of ESX-1 substrates. EspR directly binds to and activates the Rv3616c-Rv3614c promoter and, unexpectedly, is itself secreted from the bacterial cell by the ESX-1 system that it regulates. Efflux of the DNA-binding regulator results in reduced Rv3616c-Rv3614c transcription, and thus reduced ESX-1 secretion. Our results reveal a direct negative feedback loop that regulates the activity of a secretion system essential for virulence. As the virulence factors secreted by the ESX-1 system are highly antigenic, fine control of secretion may be critical to successful infection.

0 Bookmarks
 · 
102 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mycobacterium tuberculosis (MTB) infects 30% of all humans and kills someone every 20-30 s. Here we report genome-wide binding for ~80% of all predicted MTB transcription factors (TFs), and assayed global expression following induction of each TF. The MTB DNA-binding network consists of ~16,000 binding events from 154 TFs. We identify >50 TF-DNA consensus motifs and >1,150 promoter-binding events directly associated with proximal gene regulation. An additional ~4,200 binding events are in promoter windows and represent strong candidates for direct transcriptional regulation under appropriate environmental conditions. However, we also identify >10,000 'dormant' DNA-binding events that cannot be linked directly with proximal transcriptional control, suggesting that widespread DNA binding may be a common feature that should be considered when developing global models of coordinated gene expression.
    Nature Communications 01/2015; 6:5829. · 10.74 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The mycobacterial Esx-1 (ESAT-6 System-1) exporter translocates virulence factors across the cytoplasmic membrane to the cell wall, cell surface and the bacteriological media in vitro. The mechanisms underlying substrate targeting to distinct locations are unknown. Several Esx-1 substrates are N-α terminally acetylated. The role of this rare modification in bacteria is unclear. We sought to identify genes required for Esx-1 substrate modification, transport and localization. Pathogenic mycobacteria lyse Acanthamoeba castellanii in an Esx-1-dependent manner. We conducted a genetic screen to identify Mycobacterium marinum strains which failed to lyse amoebae. We identified a non-cytotoxic M. marinum strain with a transposon insertion in a predicted N-α terminal acetyltransferase not previously linked to mycobacterial pathogenesis. Disruption of this gene led to attenuation of virulence, failure to induce a type I interferon response during macrophage infection and loss of hemolytic activity. The major Esx-1 substrates, EsxA and EsxB, were exported to the cell surface, but only low levels were released into the bacteriological media. The balance of EsxA N-α terminal acetylation was disrupted resulting in a mycobacterial strain in which surface-associated EsxA was hyper-acetylated. Genetic complementation completely restored Esx-1 function and the levels of N-α terminally acetylated EsxA on the surface, but restored only low levels of Esx-1 substrates in the bacteriological media. Our results reveal a novel gene required for mycobacterial Esx-1 export. Our findings indicate that maintaining the homeostasis of Esx-1 substrate N-α terminal acetylation is essential for Esx-1-mediated virulence. We propose an inverse correlation between EsxA acetylation and virulence.
    Infection and immunity 08/2014; · 4.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Cholix toxin from V. cholerae, is the third member of the diphtheria toxin group of mono-ADP-ribosyltransferase bacterial toxins. It shares structural and functional properties with P. aeruginosa exotoxin A and C. diphtheriae diphtheria toxin. Cholix toxin is an important model for the development of antivirulence approaches and therapeutics against these toxins from pathogenic bacteria. Herein, we have used the high-resolution X-ray structure of full-length cholix complexed with NAD(+) to describe the properties of the NAD(+)-binding pocket at the residue level, including the role of crystallographic water molecules in the NAD(+) substrate interaction. The full length apo cholix structure is used to describe the putative NAD(+) binding site(s) and to correlate biochemical with crystallographic data to study the stoichiometry and orientation of bound NAD(+) molecules. We quantitatively describe the NAD(+) substrate interactions on a residue basis for the main 22 pocket residues in cholixf, a glycerol and 5 contact water molecules as part of the recognition surface by the substrate according to the conditions of crystallization. In addition, the dynamic properties of an in silico version of the catalytic domain were investigated in order to understand the lack of electronic density for one of the main flexible loops (R-loop) in the pocket of X-ray complexes. Implications for a rational drug design approach for mART toxins are derived.
    Journal of biomolecular Structure & Dynamics 01/2015; · 2.98 Impact Factor

Full-text (2 Sources)

Download
14 Downloads
Available from
Jul 18, 2014