title: Pneumococcal Pneumolysin Induces DNA Damage and Cell Cycle Arrest.
abstract: Streptococcus pneumoniae produces pneumolysin toxin as a key virulence factor against host cells. Pneumolysin is a cholesterol-dependent cytolysin (CDC) toxin that forms lytic pores in host membranes and mediates pneumococcal disease pathogenesis by modulating inflammatory responses. Here, we show that pneumolysin, which is released during bacterial lysis, induces DNA double strand breaks (DSBs), as indicated by ataxia telangiectasia mutated (ATM)-mediated H2AX phosphorylation (γH2AX). Pneumolysin-induced γH2AX foci recruit mediator of DNA damage checkpoint 1 (MDC1) and p53 binding protein 1 (53BP1), to sites of DSBs. Importantly, results show that toxin-induced DNA damage precedes cell cycle arrest and causes apoptosis when DNA-dependent protein kinase (DNA-PK)-mediated non-homologous end joining is inhibited. Further, we observe that cells that were undergoing DNA replication harbored DSBs in greater frequency during pneumolysin treatment. This observation raises the possibility that DSBs might be arising as a result of replication fork breakdown. Additionally, neutralizing the oligomerization domain of pneumolysin with monoclonal antibody suppresses DNA damage and also cell cycle arrest, indicating that pneumolysin oligomerization is important for causing DNA damage. Taken together, this study reveals a previously unidentified ability of pneumolysin to induce cytotoxicity via DNA damage, with implications in the pathophysiology of S. pneumoniae infection.
authors.affiliation: Infectious Diseases Group, Singapore-MIT Alliance for Research &Technology, Singapore 138602.|Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545.
authors.forename: Prashant
authors.initials: P
authors.lastname: Rai
authors.affiliation: Animal Health Biotechnology, Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604.
authors.forename: Fang
authors.initials: F
authors.lastname: He
authors.affiliation: Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545.|Animal Health Biotechnology, Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604.
authors.forename: Jimmy
authors.initials: J
authors.lastname: Kwang
authors.affiliation: Infectious Diseases Group, Singapore-MIT Alliance for Research &Technology, Singapore 138602.|Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Bevin P
authors.initials: BP
authors.lastname: Engelward
authors.affiliation: Infectious Diseases Group, Singapore-MIT Alliance for Research &Technology, Singapore 138602.|Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545.
authors.forename: Vincent T K
authors.initials: VT
authors.lastname: Chow
mesh_terms: D000072283:A549 Cells; D048868:Adaptor Proteins, Signal Transducing; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000494:pharmacology; D015153:Blotting, Western; D059447:Cell Cycle Checkpoints / Q000187:drug effects*; D018797:Cell Cycle Proteins; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects*; D004249:DNA Damage; D051747:DNA-Activated Protein Kinase / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D018613:Microscopy, Confocal; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011994:Recombinant Proteins / Q000494:pharmacology; D013296:Streptococcus pneumoniae / Q000378:metabolism; D013301:Streptolysins / Q000235:genetics / Q000494:pharmacology*; D015534:Trans-Activators / Q000378:metabolism; D000071857:Tumor Suppressor p53-Binding Protein 1 / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D001426:Bacterial Proteins; D018797:Cell Cycle Proteins; C468783:H2AX protein, human; D006657:Histones; C413163:MDC1 protein, human; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D013301:Streptolysins; C498301:TP53BP1 protein, human; D015534:Trans-Activators; D000071857:Tumor Suppressor p53-Binding Protein 1; C032290:plY protein, Streptococcus pneumoniae; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human