title: Additional regulatory activities of MrkH for the transcriptional expression of the Klebsiella pneumoniae mrk genes: Antagonist of H-NS and repressor.
abstract: Klebsiella pneumoniae is a common opportunistic pathogen causing nosocomial infections. One of the main virulence determinants of K. pneumoniae is the type 3 pilus (T3P). T3P helps the bacterial interaction to both abiotic and biotic surfaces and it is crucial for the biofilm formation. T3P is genetically organized in three transcriptional units: the mrkABCDF polycistronic operon, the mrkHI bicistronic operon and the mrkJ gene. MrkH is a regulatory protein encoded in the mrkHI operon, which positively regulates the mrkA pilin gene and its own expression. In contrast, the H-NS nucleoid protein represses the transcriptional expression of T3P. Here we reported that MrkH and H-NS positively and negatively regulate mrkJ expression, respectively, by binding to the promoter of mrkJ. MrkH protein recognized a sequence located at position -63.5 relative to the transcriptional start site of mrkJ gene. Interestingly, our results show that, in addition to its known function as classic transcriptional activator, MrkH also positively controls the expression of mrk genes by acting as an anti-repressor of H-NS; moreover, our results support the notion that high levels of MrkH repress T3P expression. Our data provide new insights about the complex regulatory role of the MrkH protein on the transcriptional control of T3P in K. pneumoniae.
authors.affiliation: Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Hospital de Pediatría, Centro Médico Nacional Siglo XXI-IMSS, Ciudad de México, México.|Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Ares
authors.affiliation: Unidad de Investigación en Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad de México, México.
authors.forename: José L
authors.initials: JL
authors.lastname: Fernández-Vázquez
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, México.
authors.forename: Sabino
authors.initials: S
authors.lastname: Pacheco
authors.affiliation: Unidad Académica de Ciencias Químico Biológicas, Universidad Autónoma de Guerrero, Chilpancingo, Guerrero, México.
authors.forename: Verónica I
authors.initials: VI
authors.lastname: Martínez-Santos
authors.affiliation: Unidad de Investigación en Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad de México, México.
authors.forename: Ma Dolores
authors.initials: MD
authors.lastname: Jarillo-Quijada
authors.affiliation: Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Hospital de Pediatría, Centro Médico Nacional Siglo XXI-IMSS, Ciudad de México, México.
authors.forename: Javier
authors.initials: J
authors.lastname: Torres
authors.affiliation: Unidad de Investigación en Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad de México, México.
authors.forename: María D
authors.initials: MD
authors.lastname: Alcántar-Curiel
authors.affiliation: Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, México.
authors.forename: Jorge A
authors.initials: JA
authors.lastname: González-Y-Merchand
authors.affiliation: Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Hospital de Pediatría, Centro Médico Nacional Siglo XXI-IMSS, Ciudad de México, México.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: De la Cruz
mesh_terms: D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors*; D015964:Gene Expression Regulation, Bacterial; D007710:Klebsiella Infections / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000235:genetics* / Q000254:growth & development; D009876:Operon / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012097:Repressor Proteins / Q000037:antagonists & inhibitors*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria; D012097:Repressor Proteins; D014157:Transcription Factors