IscR Is Essential for Yersinia pseudotuberculosis Type III Secretion and Virulence

PLoS Pathogens

Todd M. Lowe¹  David L. Bernick¹  Patricia P. Chan¹  Erin Mettert²  Patricia J. Kiley²  Halie K. Miller³  Laura Kwuan³  Leah Schwiesow³  Hector A. Ramirez³  Victoria Auerbuch³  James M. Ragle⁴ 

[1] Biomolecular Engineering, University of California Santa Cruz, Santa Cruz, California, United States of America;Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America;Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, California, United States of America;Department of Molecular, Cell, and Developmental Biology, University of California Santa Cruz, Santa Cruz, California, United States of America

关键词: Yersinia pseudotuberculosis;    Secretion systems;    Operons;    Chaperone proteins;    Gene regulation;    Secretion;    Transcriptional control;    Sequence motif analysis;   

DOI  :  10.1371/journal.ppat.1004194

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Type III secretion systems (T3SS) are essential for virulence in dozens of pathogens, but are not required for growth outside the host. Therefore, the T3SS of many bacterial species are under tight regulatory control. To increase our understanding of the molecular mechanisms behind T3SS regulation, we performed a transposon screen to identify genes important for T3SS function in the food-borne pathogen Yersinia pseudotuberculosis. We identified two unique transposon insertions in YPTB2860, a gene that displays 79% identity with the E. coli iron-sulfur cluster regulator, IscR. A Y. pseudotuberculosis iscR in-frame deletion mutant (ΔiscR) was deficient in secretion of Ysc T3SS effector proteins and in targeting macrophages through the T3SS. To determine the mechanism behind IscR control of the Ysc T3SS, we carried out transcriptome and bioinformatic analysis to identify Y. pseudotuberculosis genes regulated by IscR. We discovered a putative IscR binding motif upstream of the Y. pseudotuberculosis yscW-lcrF operon. As LcrF controls transcription of a number of critical T3SS genes in Yersinia, we hypothesized that Yersinia IscR may control the Ysc T3SS through LcrF. Indeed, purified IscR bound to the identified yscW-lcrF promoter motif and mRNA levels of lcrF and 24 other T3SS genes were reduced in Y. pseudotuberculosis in the absence of IscR. Importantly, mice orally infected with the Y. pseudotuberculosis ΔiscR mutant displayed decreased bacterial burden in Peyer's patches, mesenteric lymph nodes, spleens, and livers, indicating an essential role for IscR in Y. pseudotuberculosis virulence. This study presents the first characterization of Yersinia IscR and provides evidence that IscR is critical for virulence and type III secretion through direct regulation of the T3SS master regulator, LcrF.

【 授权许可】

CC BY