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Campylobacter jejuni cytolethal distending toxin promotes DNA repair responses in normal human cells
Duane C Hassane1, Robert B Lee, Carol L Pickett
1Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky, Lexington, Kentucky 40536, USA.
Abstract:
Cytolethal distending toxin (CDT) is a multisubunit protein found in various gram-negative bacterial pathogens of humans which is thought to cause cell death by direct DNA damage of host cells. We sought to determine if a cellular response to DNA damage could be detected by exogenous addition of the holotoxin. Exogenous addition of the Campylobacter jejuni 81-176 CDT to primary human fibroblasts resulted in formation of Rad50 foci, which are formed around double-stranded-DNA breaks. Moreover, such foci are formed in both proliferating and nonproliferating cells that are treated with C. jejuni CDT. Fibroblasts that were intoxicated and later stimulated to proliferate failed to divide and remained arrested in the G(1) phase of the cell cycle.
Insights
Cytolethal distending toxin (CDT) from Campylobacter jejuni causes DNA damage in human fibroblasts, detected by Rad50 foci formation. Intoxicated cells arrest in the G1 phase, preventing cell division.
Area of Science:
- Microbiology
- Molecular Biology
- Cell Biology
Background:
- Cytolethal distending toxin (CDT) is a bacterial toxin implicated in host cell death.
- CDT is produced by Gram-negative pathogens and is hypothesized to induce cell death via DNA damage.
Purpose of the Study:
- To investigate the cellular DNA damage response following exposure to Campylobacter jejuni CDT holotoxin.
- To determine if CDT induces double-strand DNA breaks in human fibroblasts.
Main Methods:
- Primary human fibroblasts were treated with purified Campylobacter jejuni 81-176 CDT holotoxin.
- Formation of Rad50 foci, indicative of DNA double-strand breaks, was assessed.
- Cell cycle progression was monitored in intoxicated fibroblasts.
Main Results:
- Exogenous addition of CDT to human fibroblasts induced the formation of Rad50 foci in both proliferating and nonproliferating cells.
- These Rad50 foci are markers for DNA double-strand breaks.
- Fibroblasts treated with CDT and subsequently stimulated to proliferate exhibited G1 phase cell cycle arrest and failed to divide.
Conclusions:
- Campylobacter jejuni CDT directly induces DNA double-strand breaks in human fibroblasts.
- CDT intoxication triggers a DNA damage response pathway, evidenced by Rad50 foci formation.
- CDT-induced DNA damage leads to cell cycle arrest, contributing to its cytotoxic effects.