No abstract

B is a secondary factor that controls the general stress regulon in Bacillus subtilis. The regulon is activated when B is released from a complex with an anti-B protein (RsbW) and becomes free to associate with RNA polymerase. Two separate mechanisms cause B release: an ATP-responsive mechanism that correlates with nutritional stress and an ATP-independent mechanism that responds to environmental insult (e.g., heat shock and ethanol treatment). ATP levels are thought to directly affect RsbW's binding preference. Low levels of ATP cause RsbW to release B and bind to an alternative protein (RsbV), while high levels of ATP favor RsbW-B complex formation and inactivation of RsbV by an RsbW-dependent phosphorylation. During growth, most of the RsbV is phosphorylated (RsbV-P) and inactive. Environmental stress induces the release of B and the formation of the RsbW-RsbV complex, regardless of ATP levels. This pathway requires the products of additional genes encoded within the eight-gene operon (sigB) that includes the genes for B , RsbW, and RsbV. By using isoelectric focusing techniques to distinguish RsbV from RsbV-P and chloramphenicol treatment or pulse-chase labeling to identify preexisting RsbV-P, we have now determined that stress induces the dephosphorylation of RsbV-P to reactivate RsbV. RsbV-P was also found to be dephosphorylated upon a drop in intracellular ATP levels. The stress-dependent and ATP-responsive dephosphorylations of RsbV-P differed in their requirements for the products of the first four genes (rsbR, -S, -T, and -U) of the sigB operon. Both dephosphorylation reactions required at least one of the genes included in a deletion that removed rsbR, -S, and -T; however, only an environmental insult required RsbU to reactivate RsbV.

No abstract

B , the general stress response factor of Bacillus subtilis, is regulated by the products of seven genes (rsbR, S, T, U, V, W, and X) with which it is cotranscribed. Biochemical techniques previously revealed physical associations among RsbW, RsbV, and B but failed to detect interactions of RsbR, S, T, U, or X with each other or RsbV, RsbW, or B . Using the yeast two-hybrid system, we have now obtained evidence for such interactions. The yeast reporter system was activated when RsbS was paired with either RsbR or RsbT, RsbR was paired with RsbT, and RsbV was paired with either RsbU or RsbW. In addition, RsbW 2 and RsbR 2 dimer formation was detected. RsbX failed to show interactions with itself or any of the other sigB operon products.