title: Control of the human cell cycle by a bacterial protein, gapstatin.
abstract: The oral gram-negative bacterium Actinobacillus actinomycetemcomitans is a major pathogen in human periodontal disease. Saline extraction releases a range of surface-associated components from this bacterium, including one which exhibits potent anti-proliferative activity as assessed by its capacity to inhibit DNA synthesis by human and other mammalian cells. Cultures incubated with this bacterial fraction for a prolonged period comprise a high proportion of cells containing a 4n level of DNA. Studies using hydroxyurea-synchronized cultures showed that cells treated with the surface-associated fraction were arrested in the G2 phase of the cell cycle and did not enter mitosis. This G2/M blockade was observed only when the bacterial fraction was added to the cells during early S phase. Our data also suggest that the active bacterial component binds to surface receptors expressed by the human cells and may act by a novel mechanism which involves down-regulation of cyclin B1 expression. The anti-proliferative activity of the bacterial fraction, purified by a combination of ammonium sulphate precipitation, HPLC anion exchange and gel filtration, has been shown to be an 8 kDa protein, which we have called gapstatin. Purified gapstatin was shown to be responsible for the the inhibitory effects of the surface-associated fraction on mammalian cells.
authors.affiliation: Maxillofacial Surgery Research Unit, Eastman Dental Institute for Oral Health Care Sciences, University of London, UK.
authors.forename: P A
authors.initials: PA
authors.lastname: White
authors.forename: M
authors.initials: M
authors.lastname: Patel
authors.forename: S
authors.initials: S
authors.lastname: Nair
authors.forename: J
authors.initials: J
authors.lastname: Ashmore
authors.forename: P
authors.initials: P
authors.lastname: Galgut
authors.forename: M
authors.initials: M
authors.lastname: Wilson
authors.forename: B
authors.initials: B
authors.lastname: Henderson
authors.forename: I
authors.initials: I
authors.lastname: Olsen
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000737:chemistry; D000818:Animals; D001426:Bacterial Proteins / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D002478:Cells, Cultured; D003561:Cytarabine / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis; D003703:Demecolcine / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology; D051379:Mice; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D014176:Protein Biosynthesis; D012313:RNA / Q000096:biosynthesis; D011956:Receptors, Cell Surface / Q000378:metabolism; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D018797:Cell Cycle Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D011956:Receptors, Cell Surface; C117537:gapstatin protein, Actinobacillus; D003561:Cytarabine; D012313:RNA; D004247:DNA; D006918:Hydroxyurea; D003703:Demecolcine