ChIP-mini: a low-input ChIP-exo protocol for elucidating DNA-binding protein dynamics in intracellular pathogens

Area of Science:

• Microbiology
• Molecular Biology
• Genomics

Background:

• Understanding pathogen virulence requires mapping DNA-binding protein interactions.
• Current ChIP-exo methods demand high bacterial cell input, limiting studies on intracellular pathogens.
• Identifying pathogen protein dynamics during infection is crucial but technically challenging.

Purpose of the Study:

• To develop a low-input ChIP-exo method (ChIP-mini) for genome-wide DNA-binding protein analysis in intracellular pathogens.
• To investigate the binding dynamics of H-NS and RpoD in Salmonella Typhimurium during host infection.
• To elucidate the coordinated regulation of virulence genes by H-NS and RpoD.

Main Methods:

• Developed and optimized ChIP-mini, a low-input ChIP-exo technique reducing cell input by 5,000-fold.
• Applied ChIP-mini to intracellular Salmonella Typhimurium within host macrophages.
• Utilized an analysis pipeline to identify and quantify genome-wide binding sites.

Main Results:

• Identified 642 H-NS and 1,837 RpoD binding sites in Salmonella Typhimurium.
• Observed decreased H-NS binding at intergenic regions post-infection, exposing virulence gene promoters.
• Found increased RpoD binding in H-NS-depleted regions, correlating with virulence gene upregulation.

Conclusions:

• ChIP-mini is an effective tool for studying DNA-binding protein dynamics in low-input pathogens.
• H-NS and RpoD collaboratively regulate virulence gene transcription initiation within macrophages.
• This method facilitates understanding pathogen adaptation and virulence mechanisms during infection.