Isolation and identification of three novel transcriptional regulators of the Brucella abortus virB operon

RODRIGO SIEIRA, DIEGO J. COMERCI Y RODOLFO A. UGALDE.

Pinamar, Pcia. De Buenos Aires, Argentina

Congreso; XLI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB) y X Pan-American Association for Biochemistry and Molecular Biology (PABMB); 2005

The Brucella abortus virB operon codes for a type-IV secretion system that is essential for virulence and intracellular mutliplication of the bacterium within host cells. Our previous studies showed that the expresssion of the virB operon is tightly regulated during the first stages of infection of J774 cells. It was observed that the proper regulation of the virB promoter (PvirB) is essential for the bacteriuim to display an effective intracellular infection. Thus, identification of transcriptional regulators and signals perceived by the bacterium to control of virB expression is of high importance. In a previous work we analyzed the PvirB structure and identified a histone-like protein (IHF) that is involved in transcriptional regulation of the virB operon.  Taking into account the arshitecture of the promoter and the localization of the IHF-binding site, we designed specific DNA probes in order to isolate additional transcriptional regulators of the virB operon. Three different proteins were isolated using an affinity purification method and were subsequently identified by mass spectrometry. These factors bind specifically to different regions of the promoter that are involved in intracellular transcriptional regulation. In view of the nature and binding region of each factor, their possible role in control of virB transcription is discussed.