IscR is essential for yersinia pseudotuberculosis type III secretion and virulence

Area of Science:

• Microbiology
• Molecular Biology
• Pathogenesis

Background:

• Type III secretion systems (T3SS) are crucial virulence factors for many bacterial pathogens, enabling direct delivery of effector proteins into host cells.
• T3SS regulation is complex and tightly controlled, particularly in pathogens like Yersinia pseudotuberculosis, which are not required for host-independent growth.

Purpose of the Study:

• To investigate the molecular mechanisms regulating the T3SS in Yersinia pseudotuberculosis.
• To identify novel genetic factors controlling T3SS function and bacterial virulence.

Main Methods:

• A transposon mutagenesis screen was employed to identify genes essential for T3SS function in Y. pseudotuberculosis.
• Transcriptome analysis and bioinformatic approaches were used to elucidate IscR-mediated gene regulation.
• In vitro binding assays and in vivo mouse infection models were utilized to assess IscR's role in virulence and T3SS regulation.

Main Results:

• A gene homologous to E. coli IscR (YPTB2860) was identified as critical for T3SS function and virulence.
• A Y. pseudotuberculosis ΔiscR mutant exhibited defects in effector secretion and macrophage targeting via T3SS.
• IscR directly binds to the yscW-lcrF promoter, downregulating lcrF and other T3SS genes, and significantly reducing bacterial burden in infected mice.

Conclusions:

• Yersinia IscR is a key regulator of the type III secretion system (T3SS) and is essential for Y. pseudotuberculosis virulence.
• IscR controls T3SS gene expression, including the master regulator LcrF, thereby impacting pathogen-host interactions and disease progression.