title: Virulence regulator EspR of Mycobacterium tuberculosis is a nucleoid-associated protein.
abstract: The principal virulence determinant of Mycobacterium tuberculosis (Mtb), the ESX-1 protein secretion system, is positively controlled at the transcriptional level by EspR. Depletion of EspR reportedly affects a small number of genes, both positively or negatively, including a key ESX-1 component, the espACD operon. EspR is also thought to be an ESX-1 substrate. Using EspR-specific antibodies in ChIP-Seq experiments (chromatin immunoprecipitation followed by ultra-high throughput DNA sequencing) we show that EspR binds to at least 165 loci on the Mtb genome. Included in the EspR regulon are genes encoding not only EspA, but also EspR itself, the ESX-2 and ESX-5 systems, a host of diverse cell wall functions, such as production of the complex lipid PDIM (phenolthiocerol dimycocerosate) and the PE/PPE cell-surface proteins. EspR binding sites are not restricted to promoter regions and can be clustered. This suggests that rather than functioning as a classical regulatory protein EspR acts globally as a nucleoid-associated protein capable of long-range interactions consistent with a recently established structural model. EspR expression was shown to be growth phase-dependent, peaking in the stationary phase. Overexpression in Mtb strain H37Rv revealed that EspR influences target gene expression both positively or negatively leading to growth arrest. At no stage was EspR secreted into the culture filtrate. Thus, rather than serving as a specific activator of a virulence locus, EspR is a novel nucleoid-associated protein, with both architectural and regulatory roles, that impacts cell wall functions and pathogenesis through multiple genes.
authors.affiliation: Global Health Institute, Ecole Polytechnique Fédérale de Lausanne-EPFL, Lausanne, Switzerland.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Blasco
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Chen
authors.forename: Ruben
authors.initials: R
authors.lastname: Hartkoorn
authors.forename: Claudia
authors.initials: C
authors.lastname: Sala
authors.forename: Swapna
authors.initials: S
authors.lastname: Uplekar
authors.forename: Jacques
authors.initials: J
authors.lastname: Rougemont
authors.forename: Florence
authors.initials: F
authors.lastname: Pojer
authors.forename: Stewart T
authors.initials: ST
authors.lastname: Cole
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005809:Genes, Regulator; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C432969:ESX1 protein, human; C031908:H-NS protein, bacteria; D018398:Homeodomain Proteins; D012097:Repressor Proteins; D037521:Virulence Factors