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Cell resistance to the Cytolethal Distending Toxin involves an association of DNA repair mechanisms.

ABSTRACT: The Cytolethal Distending Toxin (CDT), produced by many bacteria, has been associated with various diseases including cancer. CDT induces DNA double-strand breaks (DSBs), leading to cell death or mutagenesis if misrepaired. At low doses of CDT, other DNA lesions precede replication-dependent DSB formation, implying that non-DSB repair mechanisms may contribute to CDT cell resistance. To address this question, we developed a proliferation assay using human cell lines specifically depleted in each of the main DNA repair pathways. Here, we validate the involvement of the two major DSB repair mechanisms, Homologous Recombination and Non Homologous End Joining, in the management of CDT-induced lesions. We show that impairment of single-strand break repair (SSBR), but not nucleotide excision repair, sensitizes cells to CDT, and we explore the interplay of SSBR with the DSB repair mechanisms. Finally, we document the role of the replicative stress response and demonstrate the involvement of the Fanconi Anemia repair pathway in response to CDT. In conclusion, our work indicates that cellular survival to CDT-induced DNA damage involves different repair pathways, in particular SSBR. This reinforces a model where CDT-related genotoxicity primarily involves SSBs rather than DSBs, underlining the importance of cell proliferation during CDT intoxication and pathogenicity.

SUBMITTER: Bezine E

PROVIDER: S-EPMC5075911 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Cell resistance to the Cytolethal Distending Toxin involves an association of DNA repair mechanisms.

Bezine Elisabeth E Malaisé Yann Y Loeuillet Aurore A Chevalier Marianne M Boutet-Robinet Elisa E Salles Bernard B Mirey Gladys G Vignard Julien J

Scientific reports 20161024

The Cytolethal Distending Toxin (CDT), produced by many bacteria, has been associated with various diseases including cancer. CDT induces DNA double-strand breaks (DSBs), leading to cell death or mutagenesis if misrepaired. At low doses of CDT, other DNA lesions precede replication-dependent DSB formation, implying that non-DSB repair mechanisms may contribute to CDT cell resistance. To address this question, we developed a proliferation assay using human cell lines specifically depleted in each ...[more]

PMID: 27775089

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Project description:Campylobacter spp. are major causes of gastroenteritis worldwide. The virulence potential of Campylobacter shed in crow feces obtained from a roost area in Bothell, Washington, was studied and compared with that from isolates from other parts of Washington and from a different crow species 7,000 miles away in Kolkata, India. Campylobacter organisms were isolated from 61% and 69% of the fecal samples obtained from Washington and Kolkata, respectively, and were confirmed to be C. jejuni The cytolethal distending toxin (CDT) gene cluster from these isolates revealed a truncated sequence of approximately 1,350 bp. Sequencing of the gene cluster revealed two types of mutations: a 668-bp deletion across cdtA and cdtB and a 51-bp deletion within cdtB Some strains had additional 20-bp deletions in cdtB In either case, a functional toxin is not expected; a functional toxin is produced by the expression of three tandem genes, cdtA, cdtB, and cdtC Reverse transcriptase PCR with total RNA extracted from the isolates showed no expression of cdtB A toxin assay performed with these isolates on HeLa cells failed to show cytotoxic effects on the cells. However, the isolates were able to colonize the chicken ceca for a period of at least 4 weeks, similar to that of a clinical isolate. Other virulence gene markers, flagellin A and CadF, were present in 100% of the isolates. Our study suggests that crows carry the bacterium C. jejuni but with a dysfunctional toxin protein that is expected to drastically reduce its potential to cause diarrhea.IMPORTANCE Campylobacters are a major cause of gastroenteritis in humans. Since outbreaks have most often been correlated with poultry or unpasteurized dairy products, contact with farm animals, or contaminated water, historically, the majority of the studies have been with campylobacter isolates from poultry, domestic animals, and human patients. However, the bacterium has a broad host range that includes birds. These reservoirs need to be investigated, because the identification of the source and a determination of the transmission routes for a pathogen are important for the development of evidence-based disease control programs. In this study, two species of the human-commensal crow, from two different geographical regions separated by 7,000 miles of land and water, have been examined for their ability to cause disease by shedding campylobacters. Our results show that the crow may not play a significant role in campylobacteriosis, because the campylobacter organisms they shed produce a nonfunctional toxin.

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Cell resistance to the Cytolethal Distending Toxin involves an association of DNA repair mechanisms.

Publications

Cell resistance to the Cytolethal Distending Toxin involves an association of DNA repair mechanisms.

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