INVESTIGADORES
COMERCI Diego Jose
artículos
Título:
A MarR-type regulator directly activates transcription from the Brucella abortus virB promoter by sharing a redundant role with HutC
Autor/es:
SIEIRA RODRIGO; AROCENA, G. M.; ZORREGUIETA A.; COMERCI D. J; UGALDE R. A
Revista:
JOURNAL OF BACTERIOLOGY
Editorial:
AMER SOC MICROBIOLOGY
Referencias:
Lugar: Washington; Año: 2012 vol. 194 p. 6431 - 6440
ISSN:
0021-9193
Resumen:
Type IV secretion systems (T4SS) are multiprotein structures that direct the translocation of specific molecules across the bacterial
cell envelope. As in other bacteria, pathogenicity of the genus Brucella essentially depends on the integrity of the T4SS-encodingBrucella essentially depends on the integrity of the T4SS-encoding
virB operon, whose expression is regulated by multiple transcription factors belonging to different families. Previously,
we identified IHF and HutC, two direct regulators of the virB genes that were isolated from total protein extracts of Brucella.
Here, we report the identification of MdrA, a third regulatory element that was isolated using the same screening procedure.
This transcription factor, which belongs to the MarR-family of transcriptional regulators, binds at two different sites of the virBoperon, whose expression is regulated by multiple transcription factors belonging to different families. Previously,
we identified IHF and HutC, two direct regulators of the virB genes that were isolated from total protein extracts of Brucella.
Here, we report the identification of MdrA, a third regulatory element that was isolated using the same screening procedure.
This transcription factor, which belongs to the MarR-family of transcriptional regulators, binds at two different sites of the virBvirB genes that were isolated from total protein extracts of Brucella.
Here, we report the identification of MdrA, a third regulatory element that was isolated using the same screening procedure.
This transcription factor, which belongs to the MarR-family of transcriptional regulators, binds at two different sites of the virBvirB
promoter and regulates expression in a growth phase-dependent manner. Like other members of the MarR family, specific ligands
were able to dissociate MdrA from DNA in vitro. Determination of the MdrA-binding sites by DNase I footprinting and
analyses of protein-DNA complexes by electrophoresis mobility shift assays (EMSAs) showed that MdrA competes with IHF and
HutC for the binding to the promoter because their target DNA sequences overlap. Unlike IHF, both MdrA and HutC bound to
the promoter without inducing bending of DNA. Moreover, the two latter transcription factors activated virB expression to similar
extents, and in doing so, they are functionally redundant. Taken together, our results show that MdrA is a regulatory element
that directly modulates the activity of the virB promoter and is probably involved in coordinating gene expression in response
to specific environmental signals.in vitro. Determination of the MdrA-binding sites by DNase I footprinting and
analyses of protein-DNA complexes by electrophoresis mobility shift assays (EMSAs) showed that MdrA competes with IHF and
HutC for the binding to the promoter because their target DNA sequences overlap. Unlike IHF, both MdrA and HutC bound to
the promoter without inducing bending of DNA. Moreover, the two latter transcription factors activated virB expression to similar
extents, and in doing so, they are functionally redundant. Taken together, our results show that MdrA is a regulatory element
that directly modulates the activity of the virB promoter and is probably involved in coordinating gene expression in response
to specific environmental signals.virB expression to similar
extents, and in doing so, they are functionally redundant. Taken together, our results show that MdrA is a regulatory element
that directly modulates the activity of the virB promoter and is probably involved in coordinating gene expression in response
to specific environmental signals.virB promoter and is probably involved in coordinating gene expression in response
to specific environmental signals.