title: The Haemophilus ducreyi cytolethal distending toxin activates sensors of DNA damage and repair complexes in proliferating and non-proliferating cells.
abstract: Cytolethal distending toxins (CDTs) block proliferation of mammalian cells by activating DNA damage-induced checkpoint responses. We demonstrate that the Haemophilus ducreyi CDT (HdCDT) induces phosphorylation of the histone H2AX as early as 1 h after intoxication and re-localization of the DNA repair complex Mre11 in HeLa cells with kinetics similar to those observed upon ionizing radiation. Early phosphorylation of H2AX was dependent on a functional Ataxia Telangiectasia mutated (ATM) kinase. Microinjection of a His-tagged HdCdtB subunit, homologous to the mammalian DNase I, was sufficient to induce re-localization of the Mre11 complex 1 h post treatment. However, the enzymatic potency was much lower than that exerted by bovine DNase I, which caused marked chromatin changes at 106 times lower concentrations than HdCdtB. H2AX phosphorylation and Mre11 re-localization were induced also in HdCDT-treated, non-proliferating dendritic cells (DCs) in a differentiation dependent manner, and resulted in cell death. The data highlight several novel aspects of CDTs biology. We demonstrate that the toxin activates DNA damage-associated molecules in an ATM-dependent manner, both in proliferating and non-proliferating cells, acting as other DNA damaging agents. Induction of apoptotic death of immature DCs by HdCDT may represent a previously unknown mechanism of immune evasion by CDT-producing microbes.
authors.affiliation: Microbiology and Tumorbiology Center, Karolinska Institutet, Stockholm, Sweden.
authors.forename: LiQi
authors.initials: L
authors.lastname: Li
authors.forename: Anatoly
authors.initials: A
authors.lastname: Sharipo
authors.forename: Esteban
authors.initials: E
authors.lastname: Chaves-Olarte
authors.forename: Maria G
authors.initials: MG
authors.lastname: Masucci
authors.forename: Victor
authors.initials: V
authors.lastname: Levitsky
authors.forename: Monica
authors.initials: M
authors.lastname: Thelestam
authors.forename: Teresa
authors.initials: T
authors.lastname: Frisan
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D018797:Cell Cycle Proteins; D002455:Cell Division; D002460:Cell Line; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects; D004268:DNA-Binding Proteins; D003713:Dendritic Cells / Q000187:drug effects / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000494:pharmacology; D004706:Endodeoxyribonucleases / Q000187:drug effects / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000187:drug effects / Q000378:metabolism; D006191:Haemophilus ducreyi / Q000378:metabolism / Q000472:pathogenicity*; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D007165:Immunosuppression Therapy; D019869:Phosphatidylinositol 3-Kinases / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D029701:Saccharomyces cerevisiae Proteins; D013997:Time Factors; D025521:Tumor Suppressor Proteins
chemical_list: D064007:Ataxia Telangiectasia Mutated Proteins; D001427:Bacterial Toxins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D003850:Deoxyribonuclease I; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; D006657:Histones; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D025521:Tumor Suppressor Proteins; C067044:cytolethal distending toxin; C576324:ATM protein, human; C094191:MRE11 protein, S cerevisiae