Expanding the CarD interaction network: CrsL is a novel transcription regulator in actinobacteria

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Bacterial transcription regulation is essential for adaptation.
• CarD is a key transcription factor in mycobacteria.
• The interaction partners of CarD were previously unknown.

Purpose of the Study:

• To identify novel CarD interaction partners in Mycobacterium smegmatis.
• To characterize the function of the identified protein, CrsL.
• To elucidate the role of CrsL in mycobacterial stress responses.

Main Methods:

• Protein interaction studies to identify CarD partners.
• Nuclear Magnetic Resonance (NMR) spectroscopy to determine protein structure.
• Chromatin immunoprecipitation sequencing (ChIP-seq) to map genomic binding sites.
• RNA sequencing (RNA-seq) to analyze gene expression changes.
• Growth assays under various temperature conditions.

Main Results:

• A novel protein, CrsL, was identified as a CarD interaction partner.
• CrsL is an intrinsically disordered protein that adopts an ordered structure upon binding CarD.
• CrsL binds RNAP and modulates CarD-RNAP association.
• CrsL and CarD co-localize at the promoters of actively transcribed genes.
• CrsL knockdown affects gene expression similarly to CarD knockdown, particularly in stress response genes.
• CrsL influences bacterial growth at different temperatures, supporting growth at high temperatures but limiting it in cold.

Conclusions:

• CrsL is a novel, conserved protein that interacts with CarD in mycobacteria.
• CrsL plays a significant role in regulating gene expression and mediating stress responses.
• CrsL modulates CarD function, impacting bacterial adaptation to environmental changes.