TRANSCRIPTIONAL AUTOREGULATION OF THE RcsC-RcsD-RcsB TWO-COMPONENT SYSTEM IN Salmonella typhimurium.

MARÍA DE LAS MERCEDES PESCARETTI; ROBERTO MORERO; MÓNICA A. DELGADO

San Miguel de Tucumán-Tucumán

Congreso; XXXVIII Congreso Argentino de Genética; 2009

Sociedad Argentina de Genética

The Rcs phosphorelay system controls the expression of the colanic acid biosynthesis (cps operon) and the master flagellar regulator flhDC operon?s. The Rcs system consists of the sensor protein RcsC, the response regulator RcsB, and the histidin-containing phosphotransfer protein RcsD, which serve as an intermediary in the phosphoryl transfer from RcsC to RcsB. Although, numerous environmental factors are known to induce the Rcs system, the real signal that leads the activation of this system is unknown. Previously, we found that the RcsB overproduction promotes the Rcs system activation in the rcsC or rcsD mutants, but not in the rcsD rcsC double mutant. Here, we study the RcsB overproduction effect on the expression of the Rcs component genes. Even though that, rcsB and rcsD genes are situated in what appears to be an operon, our results demonstrated that RcsB overexpression resulted in strong repression of rcsD but only weak repression of rcsB. The rcsC expression was not affected by this condition. Our findings shown that differential rcsD and rcsB expression is due to the presence of two promoters controlling the rcsB transcription: i) the PrcsDB previously reported, and ii) the PrcsB located in the 3?-end of rcsD region, described herein. These results suggest that high levels of RcsB negatively regulate the Rcs system.