REACTIVATION OF THE BACILLUS-SUBTILIS ANTI-SIGMA(B) ANTAGONIST, RSBV,BY STRESS-INDUCED OR STARVATION-INDUCED PHOSPHATASE-ACTIVITIES

sigma(B) is a secondary sigma factor that controls the general stress regulon in Bacillus subtilis. Tile regulon is activated when sigma(B) is released from a complex with an anti-sigma(B) protein (RsbW) and be comes free to associate with RNA polymerase. Two separate mechanisms c ause sigma(B) release: an ATP-responsive mechanism that correlates wit h nutritional stress and an ATP-independent mechanism that responds to environmental insult leg., heat shock and ethanol treatment). ATP lev els are thought to directly affect RsbW's binding preference, Low leve ls of ATP cause RsbW to release sigma(B) and bind to an alternative pr otein (RsbV), while high levels of ATP favor RsbW-sigma(B) complex for mation and inactivation of RsbV by an RsbW-dependent phosphorylation. During growth, most of the RsbV is phosphorylated (RsbV-P) and inactiv e. Environmental stress induces the release of sigma(B) and the format ion of the RsbW-RsbV complex, regardless of ATP levels, This pathway r equires the products of additional genes encoded within the eight-gent operon (sigB) that includes the genes for sigma(B), RsbW, and RsbV By using isoelectric focusing techniques to distinguish RsbV from RsbV-P and chloramphenicol treatment or pulse-chase labeling to identify pre existing RsbV-P, we have now determined that stress induces the dephos phorylation of RsbV-P to reactivate RsbV. RsbV-P was also found to be dephosphorylated upon a drop in intracellular ATP levels, The stress-d ependent and ATP-responsive dephosphorylations of RsbV-P differed in t heir requirements for the products of the first four genes (rsbR, -S, -T, and -U) of the sigB operon, Both dephosphorylation reactions requi red at least one of the genes included in a deletion that removed rsbR , -S, and -T; however, only an environmental insult required RsbU to r eactivate RsbV.