title: Regulation of the Legionella mip-promotor during infection of human monocytes.
abstract: The opportunistic pathogen Legionella pneumophila, the etiologic agent of Legionnaires disease, is able to invade and multiply intracellularly in human macrophages. This process is controlled by several bacterial virulence factors. As recently demonstrated, one of these virulence factors, the macrophage infectivity potentiator (Mip) protein, is important for invasion and proper intracellular establishment of L. pneumophila in macrophages and protozoa. Knockout mutants devoid of a functional mip-gene enter host cells much less effectively but intracellular replication is not affected. Using a P(mip)-green fluorescent protein reporter construct in L. pneumophila substrain Corby, P(mip) was recently shown to be constitutively active in replicating bacteria. A stringent regulation during the infection process could not be observed, neither in intracellular nor in BYE broth-grown bacteria. For enhanced temporal and quantitative resolution, we examined the activity of mip on RNA level in order to detect short transient regulatory events. Our results show that P(mip) of L. pneumophila is temporarily repressed directly after invasion of the monocytic human cell line MonoMac 6 and regains activity after 24 h of intracellular replication.
authors.affiliation: Abteilung Transfusionsmedizin, AG Infektionsbiologie, Zentrum für Medizinische Forschung, Universitätsklinikum Tübingen, Waldhörnlestrasse 22, 72076 Tübingen, Germany. hagen.wieland@uni-tuebingen.de
authors.forename: Hagen
authors.initials: H
authors.lastname: Wieland
authors.forename: Marion
authors.initials: M
authors.lastname: Faigle
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
authors.forename: Hinnak
authors.initials: H
authors.lastname: Northoff
authors.forename: Birgid
authors.initials: B
authors.lastname: Neumeister
mesh_terms: D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007875:Legionella / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity; D016952:Legionella pneumophila / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D007877:Legionnaires' Disease / Q000382:microbiology; D051739:Microphthalmia-Associated Transcription Factor; D009000:Monocytes / Q000382:microbiology*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014157:Transcription Factors; D014158:Transcription, Genetic; D014774:Virulence
chemical_list: D004268:DNA-Binding Proteins; C497234:MITF protein, human; D051739:Microphthalmia-Associated Transcription Factor; D014157:Transcription Factors