title: Mitogenic factor (MF) is the major DNase of serotype M89 Streptococcus pyogenes.
abstract: To investigate the role of mitogenic factor (MF) in streptococcal pathogenesis, the structural gene (mf) encoding this protein was disrupted in a clinical isolate of Streptococcus pyogenes H293, to yield the isogenic mutant H363. Growth in enriched broth and on blood agar was unaffected by disruption of mf. Cell-free broth supernatants from H293 and H363 demonstrated identical promitogenic activities when co-incubated with human peripheral blood mononuclear cells, even when diluted 100000-fold, showing that MF is not a major streptococcal mitogen compared with other secreted superantigens. Disruption of mf resulted in complete loss of DNase B production and detectable DNase activity in H363 compared with the parent strain, confirming that the single gene mf, which is present in all group A streptococcal M serotypes studied, encodes DNase B. Despite loss of DNase activity, the virulence of S. pyogenes in a mouse model of necrotizing fasciitis and myositis was unaffected.
authors.affiliation: Department of Infectious Diseases, Imperial College School of Medicine, London W12 0NN, UK1.
authors.forename: Shiranee
authors.initials: S
authors.lastname: Sriskandan
authors.affiliation: Department of Infectious Diseases, Imperial College School of Medicine, London W12 0NN, UK1.
authors.forename: Meera
authors.initials: M
authors.lastname: Unnikrishnan
authors.affiliation: Department of Infectious Diseases, Imperial College School of Medicine, London W12 0NN, UK1.
authors.forename: Thomas
authors.initials: T
authors.lastname: Krausz
authors.affiliation: Department of Infectious Diseases, Imperial College School of Medicine, London W12 0NN, UK1.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Cohen
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology*; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D003851:Deoxyribonucleases / Q000235:genetics* / Q000502:physiology*; D019115:Fasciitis, Necrotizing / Q000209:etiology; D017353:Gene Deletion; D005798:Genes, Bacterial; D006801:Humans; D066298:In Vitro Techniques; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D051379:Mice; D008934:Mitogens / Q000235:genetics* / Q000502:physiology*; D009220:Myositis / Q000209:etiology; D010957:Plasmids / Q000235:genetics; D012703:Serotyping; D013290:Streptococcal Infections / Q000209:etiology / Q000276:immunology / Q000473:pathology; D013297:Streptococcus pyogenes / Q000145:classification / Q000235:genetics* / Q000502:physiology*; D014170:Transformation, Genetic; D014774:Virulence / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D015850:Interleukin-6; D008934:Mitogens; C083356:mitogenic factor, Streptococcus; D003851:Deoxyribonucleases; C020069:deoxyribonuclease B