Cytolethal distending toxin demonstrates genotoxic activity in a yeast model

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Cytolethal distending toxins (CDTs) are bacterial virulence factors inducing cell cycle arrest and apoptosis in mammalian cells.
• Recent evidence suggests CDTs function as intracellular DNases, but their precise mechanism and genotoxic potential remain under investigation.

Purpose of the Study:

• To establish a novel yeast model for investigating the cellular effects and genotoxicity of CDT subunit B (CdtB).
• To elucidate the mechanism of CdtB-induced cell cycle arrest and DNA damage in a simplified eukaryotic system.

Main Methods:

• Expression of the bacterial CdtB subunit in Saccharomyces cerevisiae.
• Analysis of cell cycle progression using flow cytometry.
• Assessment of DNA damage and cell viability in wild-type and genetically modified yeast strains (lacking DNA damage checkpoints or with constitutively active Cdk1).

Main Results:

• Expression of CdtB in yeast induced a G2/M cell cycle arrest, mirroring effects in mammalian cells.
• CdtB-induced toxicity was not rescued by eliminating DNA damage checkpoints or forcing cell cycle progression, indicating permanent DNA damage.
• In vivo degradation of chromosomal DNA was observed upon CdtB expression, confirming its potent genotoxic activity.

Conclusions:

• The yeast model effectively recapitulates CdtB-induced cell cycle arrest and demonstrates its potent genotoxicity.
• CDTs are confirmed as genotoxins capable of causing permanent DNA damage, leading to cell death.
• The widespread presence of CDT-producing bacteria suggests a significant role for genotoxic activity in numerous human pathogens.