The yeast two-hybrid system detects interactions between Bacillus subtilis σ(B) regulators

σ(B), the general stress response σ 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 σ(B) but failed to detect interactions of RsbR, S, T, U, or X with each other or RsbV, RsbW, or σ(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, RsbW₂ and RsbR₂ dimer formation was detected. RsbX failed to show interactions with itself or any of the other sigB operon products.