ChIP-seq analysis of VjbR unveils the tip of the iceberg of the Brucella virulence genetic program.

RODRIGO SIEIRA

Chicago

Congreso; 68th Annual Brucellosis Research Conference; 2015

p { margin-bottom: 0.1in; line-height: 120%; }VjbRis a LuxR-type transcription factor central for the virulence ofBrucella. In addition to its main role as an activator of flagellarcomponents and the VirB Type-IV Secretion System, mutations affectingVjbR cause pleiotropic effects and alter the expression of severalmembrane components. Moreover, high-throughput experiments revealedthat, directly or indirectly, VjbR affects transcription of hundredsof genes, suggesting that it is indeed a global regulator of Brucellagene expression. However, until now, no target DNA-consensus sequencemotif was identified and determination of the genes directlyregulated by VjbR have so far proven elusive. Here, we performed adirect genome-wide assessment of the VjbR-binding sites usingchromatin immunoprecipitation followed by high-throughput DNAsequencing (ChIP-seq), in order to determine the regulon of VjbRunder conditions that trigger the expression of VjbR and mimic theintracellular environment that Brucella encounters within the hostcell. Using these procedures, we obtained high-quality data sets thatallowed us to define 157 bona fide ChIP-seq peaks. Bioinformaticanalysis of the ChIP-enriched regions led to the identification of aVjbR-binding consensus motif displaying structural features thatcomplement previous knowledge of the molecular interaction betweenVjbR and the virB promoter. Taken together, our results provide newinsights on the VjbR-mediated global control of expression and reveala set of direct target genes that might lead to a comprehensiveunderstanding of the mechanisms by which Brucella establishes theintracellular infection within its eukaryotic host.