title: Plasticity of a transcriptional regulation network among alpha-proteobacteria is supported by the identification of CtrA targets in Brucella abortus.
abstract: CtrA is a master response regulator found in many alpha-proteobacteria. In Caulobacter crescentus and Sinorhizobium meliloti, this regulator is essential for viability and is transcriptionally autoregulated. In C. crescentus, it is required for the regulation of multiple cell cycle events, such as DNA methylation, DNA replication, flagella and pili biogenesis and septation. Here, we report the characterization of the ctrA gene homologue in the alpha2-proteobacteria Brucella abortus, a facultative intracellular pathogen responsible for brucellosis. We detected CtrA expression in the main Brucella species, and its overproduction led to a phenotype typical of cell division defect, consistent with its expected role. A purified B. abortus CtrA recombinant protein (His6-CtrA) was shown to protect the B. abortus ctrA promoter from DNase I digestion, suggesting transcriptional autoregulation, and this protection was enhanced under CtrA phosphorylation on a conserved Asp residue. Despite the similarities shared by B. abortus and C. crescentus ctrA, the pathway downstream from CtrA may be distinct, at least partially, in both bacteria. Indeed, beside ctrA itself, only one (the ccrM gene) out of four B. abortus homologues of known C. crescentus CtrA targets is bound in vitro by phosphorylated B. abortus CtrA. Moreover, further footprinting experiments support the hypothesis that, in B. abortus, CtrA might directly regulate the expression of the rpoD, pleC, minC and ftsE homologues. Taken together, these results suggest that, in B. abortus and C. crescentus, similar cellular processes are regulated by CtrA through the control of distinct target genes. The plasticity of the regulation network involving CtrA in these two bacteria may be related to their distinct lifestyles.
authors.affiliation: Unité de Recherche en Biologie Moléculaire (URBM), Facultés Universitaires Notre Dame de la Paix, 61, rue de Bruxelles, B-5000 Namur, Belgium.
authors.forename: Anne-Flore
authors.initials: AF
authors.lastname: Bellefontaine
authors.forename: Christophe E
authors.initials: CE
authors.lastname: Pierreux
authors.forename: Pascal
authors.initials: P
authors.lastname: Mertens
authors.forename: Jean
authors.initials: J
authors.lastname: Vandenhaute
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Letesson
authors.forename: Xavier
authors.initials: X
authors.lastname: De Bolle
mesh_terms: D020561:Alphaproteobacteria; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002003:Brucella abortus / Q000235:genetics* / Q000378:metabolism; D016935:Caulobacter crescentus / Q000235:genetics / Q000378:metabolism; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D018741:Replication Origin; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; C097706:CtrA protein, Caulobacter; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; C095478:DivK protein, Caulobacter crescentus; C071525:FtsZ protein, Bacteria; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors