Academic Medical Center, Center for Infection and Immunity Amsterdam (CINIMA), Department of Medical Microbiology, Amsterdam, the Netherlands.
BMC Microbiol. 2010 Jun 4;10:164. doi: 10.1186/1471-2180-10-164.
Fine tuning expression of genes is a prerequisite for the strictly human pathogen Neisseria meningitidis to survive hostile growth conditions and establish disease. Many bacterial species respond to stress by using alternative sigma factors which, in complex with RNA polymerase holoenzyme, recognize specific promoter determinants. sigma(E), encoded by rpoE (NMB2144) in meningococci, is known to be essential in mounting responses to environmental challenges in many pathogens. Here we identified genes belonging to the sigma(E) regulon of meningococci.
We show that meningococcal sigma(E) is part of the polycistronic operon NMB2140-NMB2145 and autoregulated. In addition we demonstrate that sigma(E) controls expression of methionine sulfoxide reductase (MsrA/MsrB). Moreover, we provide evidence that the activity of sigma(E) is under control of NMB2145, directly downstream of rpoE. The protein encoded by NMB2145 is structurally related to anti-sigma domain (ASD) proteins and characterized by a zinc containing anti-sigma factor (ZAS) motif, a hall mark of a specific class of Zn(2+)-binding ASD proteins acting as anti-sigma factors. We demonstrate that Cys residues in ZAS, as well as the Cys residue on position 4, are essential for anti-sigma(E) activity of NMB2145, as found for a minority of members of the ZAS family that are predicted to act in the cytoplasm and responding to oxidative stimuli. However, exposure of cells to oxidative stimuli did not result in altered expression of sigma(E).
Together, our results demonstrate that meningococci express a functional transcriptionally autoregulated sigma(E) factor, the activity of which is controlled by a novel meningococcal anti-sigma factor belonging to the ZAS family.
精细调控基因表达是严格的人类病原体脑膜炎奈瑟菌在恶劣生长条件下生存并引发疾病的前提条件。许多细菌物种通过使用替代σ因子来应对应激，这些因子与 RNA 聚合酶全酶形成复合物，识别特定的启动子决定因素。脑膜炎奈瑟菌中的 rpoE（NMB2144）编码的σ（E）已知在许多病原体应对环境挑战时是必需的。在这里，我们鉴定了属于脑膜炎奈瑟菌σ（E）调控子的基因。
我们表明，脑膜炎奈瑟菌的σ（E）是多顺反子操纵子 NMB2140-NMB2145 的一部分，并具有自我调控功能。此外，我们证明σ（E）控制甲硫氨酸亚砜还原酶（MsrA/MsrB）的表达。此外，我们提供的证据表明，σ（E）的活性受到 NMB2145 的控制，NMB2145 直接位于 rpoE 的下游。NMB2145 编码的蛋白质与反σ结构域（ASD）蛋白结构相关，其特征是含有锌的反σ因子（ZAS）基序，这是一类特定的 Zn2+结合 ASD 蛋白作为反σ因子的特征。我们证明，ZAS 中的 Cys 残基以及位置 4 上的 Cys 残基对于 NMB2145 的反σ（E）活性是必需的，这与少数被预测在细胞质中起作用并响应氧化应激的 ZAS 家族成员的情况相同。然而，细胞暴露于氧化应激并不会导致 σ（E）的表达发生改变。
总之，我们的研究结果表明，脑膜炎奈瑟菌表达一种功能性的转录自我调控的 σ（E）因子，其活性受一种新型脑膜炎奈瑟菌反 σ 因子的控制，该因子属于 ZAS 家族。
