The alternative transcription factor σB in Bacillus cereus governs the transcription of a number of genes that confer protection against general stress. This transcription factor is regulated by protein-protein interactions among RsbV, RsbW, σB, RsbY, RsbM and RsbK, all encoded in the sigB cluster. Among these regulatory proteins, RsbV, RsbW and σB comprise a partner-switching mechanism. Under normal conditions, σB remains inactive by associating with anti-sigma factor RsbW, which prevents σB from binding to the core RNA polymerase. During environmental stress, RsbK activates RsbY to hydrolyze phosphorylated RsbV, and the dephosphorylated RsbV then sequesters RsbW to liberate σB from RsbW. Although the σB partner-switching module is thought to be the core mechanism for σB regulation, the actual protein-protein interactions among these three proteins in the cell remain to be investigated. In the current study, we show that RsbW and RsbV form a long-lived complex under transient stress treatment, resulting in high persistent expression of RsbV, RsbW and σB from mid-log phase to stationary phase. Full sequestration of RsbW by excess RsbV and increased RsbW:RsbV complex stability afforded by cellular ADP contribute to the prolonged activation of σB. Interestingly, the high expression levels of RsbV, RsbW and σB were dramatically decreased beginning from the transition stage to the stationary phase. Thus, protein interactions among σB partner-switching components are required for the continued induction of σB during environmental stress in the log phase and significant down-regulation of σB is observed in the stationary phase. Our data show that σB is temporally regulated in B. cereus.

中文翻译：

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蜡样芽孢杆菌在不同生长阶段通过伙伴转换机制对σB的时间调控。

蜡样芽孢杆菌中的替代转录因子σB控制着许多基因的转录，这些基因赋予了抵抗一般压力的保护作用。该转录因子受RsbV，RsbW，σB，RsbY，RsbM和RsbK之间的蛋白质-蛋白质相互作用调节，所有这些相互作用都编码在sigB簇中。在这些调节蛋白中，RsbV，RsbW和σB构成伙伴转换机制。在正常情况下，σB通过与抗σ因子RsbW关联而保持非活性，这可防止σB与核心RNA聚合酶结合。在环境压力下，RsbK激活RsbY水解磷酸化的RsbV，然后脱磷酸的RsbV隔离RsbW从RsbW中释放出σB。尽管σB伙伴切换模块被认为是σB调节的核心机制，细胞中这三种蛋白质之间实际的蛋白质-蛋白质相互作用尚待研究。在当前的研究中，我们显示RsbW和RsbV在瞬态应力处理下形成了长寿命复合物，导致RsbV，RsbW和σB从对数中期到平稳期都具有高持久性表达。过量的RsbV完全螯合RsbW和细胞ADP提供的增加的RsbW：RsbV复合物稳定性会导致σB的活化时间延长。有趣的是，从过渡阶段到稳定期开始，RsbV，RsbW和σB的高表达水平显着下降。因此，在对数期的环境胁迫期间，σB伴侣转换成分之间的蛋白质相互作用是σB持续诱导所必需的，而在固定相中则观察到σB明显下调。