title: Long-range transcriptional control of an operon necessary for virulence-critical ESX-1 secretion in Mycobacterium tuberculosis.
abstract: The ESX-1 secretion system of Mycobacterium tuberculosis has to be precisely regulated since the secreted proteins, although required for a successful virulent infection, are highly antigenic and their continued secretion would alert the immune system to the infection. The transcription of a five-gene operon containing espACD-Rv3613c-Rv3612c, which is required for ESX-1 secretion and is essential for virulence, was shown to be positively regulated by the EspR transcription factor. Thus, transcription from the start site, found to be located 67 bp upstream of espA, was dependent upon EspR enhancer-like sequences far upstream (between 884 and 1,004 bp), which we term the espA activating region (EAR). The EAR contains one of the known binding sites for EspR, providing the first in vivo evidence that transcriptional activation at the espA promoter occurs by EspR binding to the EAR and looping out DNA between this site and the promoter. Regulation of transcription of this operon thus takes place over long regions of the chromosome. This regulation may differ in some members of the M. tuberculosis complex, including Mycobacterium bovis, since deletions of the intergenic region have removed the upstream sequence containing the EAR, resulting in lowered espA expression. Consequent differences in expression of ESX-1 in these bacteria may contribute to their various pathologies and host ranges. The virulence-critical nature of this operon means that transcription factors controlling its expression are possible drug targets.
authors.affiliation: Division of Mycobacterial Research, MRC National Institute for Medical Research, Mill Hill, London, United Kingdom.
authors.forename: Debbie M
authors.initials: DM
authors.lastname: Hunt
authors.forename: Nathan P
authors.initials: NP
authors.lastname: Sweeney
authors.forename: Luisa
authors.initials: L
authors.lastname: Mori
authors.forename: Rachael H
authors.initials: RH
authors.lastname: Whalan
authors.forename: Iñaki
authors.initials: I
authors.lastname: Comas
authors.forename: Laura
authors.initials: L
authors.lastname: Norman
authors.forename: Teresa
authors.initials: T
authors.lastname: Cortes
authors.forename: Kristine B
authors.initials: KB
authors.lastname: Arnvig
authors.forename: Elaine O
authors.initials: EO
authors.lastname: Davis
authors.forename: Melanie R
authors.initials: MR
authors.lastname: Stapleton
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Green
authors.forename: Roger S
authors.initials: RS
authors.lastname: Buxton
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D008969:Molecular Sequence Data; D005810:Multigene Family; D009163:Mycobacterium bovis / Q000235:genetics / Q000378:metabolism; D020102:Mycobacterium smegmatis / Q000235:genetics / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D009876:Operon; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014158:Transcription, Genetic; D014774:Virulence
chemical_list: D001426:Bacterial Proteins