Department of Molecular Biology, Umeå University, Umeå, Sweden.
FEMS Microbiol Rev. 2011 May;35(3):425-40. doi: 10.1111/j.1574-6976.2010.00255.x. Epub 2010 Nov 5.
Alternative σ-factors of bacteria bind core RNA polymerase to program the specific promoter selectivity of the holoenzyme. Signal-responsive changes in the availability of different σ-factors redistribute the RNA polymerase among the distinct promoter classes in the genome for appropriate adaptive, developmental and survival responses. The σ(54) -factor is structurally and functionally distinct from all other σ-factors. Consequently, binding of σ(54) to RNA polymerase confers unique features on the cognate holoenzyme, which requires activation by an unusual class of mechano-transcriptional activators, whose activities are highly regulated in response to environmental cues. This review summarizes the current understanding of the mechanisms of transcriptional activation by σ(54) -RNA polymerase and highlights the impact of global regulatory factors on transcriptional efficiency from σ(54) -dependent promoters. These global factors include the DNA-bending proteins IHF and CRP, the nucleotide alarmone ppGpp, and the RNA polymerase-targeting protein DksA.
细菌的替代 σ 因子结合核心 RNA 聚合酶，为全酶特异性启动子选择性编程。不同 σ 因子可用性的信号响应变化将 RNA 聚合酶在基因组中不同的启动子类之间重新分配，以进行适当的适应性、发育和生存反应。σ(54) 因子在结构和功能上与所有其他 σ 因子不同。因此，σ(54)与 RNA 聚合酶的结合赋予了同源全酶独特的特征，这需要通过一类不寻常的机械转录激活因子来激活，其活性高度响应环境线索进行调节。这篇综述总结了目前对 σ(54)-RNA 聚合酶转录激活机制的理解，并强调了全局调控因子对 σ(54)依赖启动子转录效率的影响。这些全局因子包括 DNA 弯曲蛋白 IHF 和 CRP、核苷酸警报素 ppGpp 和靶向 RNA 聚合酶的蛋白 DksA。
