New insights on intracellular survival strategies of Brucella by dissection of virulence-associated regulatory networks

RODRIGO SIEIRA

Greenville, North Carolina

Seminario; Invitación como orador invitado a Department of Microbiology and Immunology, East Carolina University; 2016

p { margin-bottom: 0.25cm; direction: ltr; line-height: 120%; text-align: left; }VjbRis a LuxR-type transcription factor central for the virulence ofBrucella.In addition to its main role as an activator of flagellar componentsand the VirB Type-IV Secretion System, mutations affecting VjbR causepleiotropic effects and alter the expression of several membranecomponents. Moreover, high-throughput experiments revealed that,directly or indirectly, VjbR affects transcription of hundreds ofgenes, suggesting that it is indeed a global regulator of Brucellagene expression. However, untilnow, notarget DNA-consensus sequence motif was identified and determinationof the genes directly regulated by VjbR have so far proven ep { margin-bottom: 0.25cm; direction: ltr; line-height: 120%; text-align: left; }VjbRis a LuxR-type transcription factor central for the virulence ofBrucella.In addition to its main role as an activator of flagellar componentsand the VirB Type-IV Secretion System, mutations affecting VjbR causepleiotropic effects and alter the expression of several membranecomponents. Moreover, high-throughput experiments revealed that,directly or indirectly, VjbR affects transcription of hundreds ofgenes, suggesting that it is indeed a global regulator of Brucellagene expression. However, untilnow, notarget DNA-consensus sequence motif was identified and determinationof the genes directly regulated by VjbR have so far proven elusive. Here, weperformed a direct genome-wide assessment of the VjbR-binding sitesusing chromatinimmunoprecipitation followed by high-throughput DNA sequencing(ChIP-seq),in order to determine the regulon of VjbR under conditions thattrigger the expression of VjbR and mimic the intracellularenvironment that Brucellaencounters within thehost cell. Using these procedures, we obtained high-quality data setsthat allowed 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 virBpromoter. Takentogether, our results provide new insights on the VjbR-mediatedglobal control of expression and reveal a set of direct target genesthat might lead to a comprehensive understanding of the mechanisms bywhich Brucellaestablishes theintracellular infection within its eukaryotic host.