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首页> 外文期刊>Infection and immunity >Regulation of the prfA transcriptional activator of Listeria monocytogenes: multiple promoter elements contribute to intracellular growth and cell-to-cell spread.
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Regulation of the prfA transcriptional activator of Listeria monocytogenes: multiple promoter elements contribute to intracellular growth and cell-to-cell spread.

机译：李斯特菌李斯特菌prfA转录激活因子的调控：多个启动子元件促进细胞内生长和细胞间扩散。

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The prfA gene product is a transcriptional activator of Listeria monocytogenes determinants of pathogenicity. In this study, we provide direct evidence that the PrfA protein is a site-specific DNA-binding protein. Additionally, we describe the characterization of two classes of L. monocytogenes mutants which contain transposon insertions either in the prfA structural gene (exemplified by strain DP-L1075) or within the prfA promoter region (exemplified by strain DP-L973). Both mutants are completely avirulent and secrete greatly reduced levels of listeriolysin O and phosphatidylinositol-specific phospholipase C, and both are fully complemented by the introduction of prfA on a multicopy plasmid. The behaviors of the two mutants differ markedly within cultured macrophages. Following infection, no cytoplasmic growth was observed for DP-L1075 whereas DP-L973 escaped from the phagosome and grew in the cell cytoplasm. However, DP-L973 was defective in nucleation of actin filaments and spread to adjacent cells. Transcription of prfA in DP-L973 was directed from a single, previously unidentified promoter (prfAp2) located close to the prfA initiation codon. This promoter is therefore capable of providing sufficient prfA expression for escape from the host cell vacuole but is insufficient for wild-type levels of bacterially induced actin polymerization and cell-to-cell spread. Transcription directed from both prfAp1 and prfAp2 promoters was increased in the absence of a functional prfA gene product, suggesting that PrfA protein contributes to down-regulating its own expression.
机译：prfA基因产物是李斯特菌致病性决定因素的转录激活因子。在这项研究中，我们提供了直接的证据，证明PrfA蛋白是一种位点特异性的DNA结合蛋白。此外，我们描述了两类单核细胞增生李斯特氏菌突变体的特征，这些突变体在prfA结构基因（以DP-L1075株为例）或prfA启动子区域（以DP-L973株为例）内含有转座子插入。这两个突变体都是完全无毒的，并且分泌的李斯特菌溶血素O和磷脂酰肌醇特异性磷脂酶C的水平大大降低，并且都通过在多拷贝质粒上引入prfA来完全互补。这两个突变体的行为在培养的巨噬细胞内明显不同。感染后，未观察到DP-L1075的细胞质生长，而DP-L973从吞噬体逃逸并在细胞质中生长。但是，DP-L973在肌动蛋白丝的成核中有缺陷，并扩散到相邻的细胞中。 DP-L973中prfA的转录是由位于prfA起始密码子附近的单个先前未鉴定的启动子（prfAp2）指导的。因此，该启动子能够提供足够的prfA表达，以逃离宿主细胞的液泡，但是对于野生型水平的细菌诱导的肌动蛋白聚合反应和细胞间扩散是不够的。在缺少功能性prfA基因产物的情况下，来自prfAp1和prfAp2启动子的转录增加，这表明PrfA蛋白有助于下调其自身表达。

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