title: Analysis of the prevalence, secretion and function of a cell cycle-inhibiting factor in the melioidosis pathogen Burkholderia pseudomallei.
abstract: Enteropathogenic and enterohaemorrhagic Escherichia coli express a cell cycle-inhibiting factor (Cif), that is injected into host cells via a Type III secretion system (T3SS) leading to arrest of cell division, delayed apoptosis and cytoskeletal rearrangements. A homologue of Cif has been identified in Burkholderia pseudomallei (CHBP; Cif homologue in B. pseudomallei; BPSS1385), which shares catalytic activity, but its prevalence, secretion and function are ill-defined. Among 43 available B. pseudomallei genome sequences, 33 genomes (76.7%) harbor the gene encoding CHBP. Western blot analysis using antiserum raised to a synthetic CHBP peptide detected CHBP in 46.6% (7/15) of clinical B. pseudomallei isolates from the endemic area. Secretion of CHBP into bacterial culture supernatant could not be detected under conditions where a known effector (BopE) was secreted in a manner dependent on the Bsa T3SS. In contrast, CHBP could be detected in U937 cells infected with B. pseudomallei by immunofluorescence microscopy and Western blotting in a manner dependent on bsaQ. Unlike E. coli Cif, CHBP was localized within the cytoplasm of B. pseudomallei-infected cells. A B. pseudomallei chbP insertion mutant showed a significant reduction in cytotoxicity and plaque formation compared to the wild-type strain that could be restored by plasmid-mediated trans-complementation. However, there was no defect in actin-based motility or multinucleated giant cell formation by the chbP mutant. The data suggest that the level or timing of CHBP secretion differs from a known Bsa-secreted effector and that CHBP is required for selected virulence-associated phenotypes in vitro.
authors.affiliation: Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand; Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Pornpan
authors.initials: P
authors.lastname: Pumirat
authors.affiliation: The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, United Kingdom.
authors.forename: Charles Vander
authors.initials: CV
authors.lastname: Broek
authors.affiliation: Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Niramol
authors.initials: N
authors.lastname: Juntawieng
authors.affiliation: Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Veerachat
authors.initials: V
authors.lastname: Muangsombut
authors.affiliation: Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Pattarachai
authors.initials: P
authors.lastname: Kiratisin
authors.affiliation: Center of Excellence for Flow Cytometry, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Kovit
authors.initials: K
authors.lastname: Pattanapanyasat
authors.affiliation: The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, United Kingdom.
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Stevens
authors.affiliation: The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, United Kingdom.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Stevens
authors.affiliation: Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Sunee
authors.initials: S
authors.lastname: Korbsrisate
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D016957:Burkholderia pseudomallei / Q000235:genetics* / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000235:genetics*; D019295:Computational Biology; D009154:Mutation
chemical_list: D001426:Bacterial Proteins