Freitag N E, Portnoy D A
Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia 19104-6076.
Mol Microbiol. 1994 Jun;12(5):845-53. doi: 10.1111/j.1365-2958.1994.tb01070.x.
The PrfA transcriptional activator is an essential determinant of Listeria monocytogenes pathogenesis. prfA expression is governed by three differentially regulated promoters: prfAP1 and prfAP2, which are located immediately upstream of prfA coding sequences, and the adjacent plcA promoter via the generation of a plcA-prfA read-through transcript. A series of promoter deletion mutants were constructed to assess the roles of prfAP1 and prfAP2. Elimination of either prfAP1 or prfAP2 resulted in altered regulation of PrfA-regulated genes after in vitro growth. However, these mutants were fully virulent both in an animal model and in tissue culture models of infection, suggesting that the two prfA promoters are functionally redundant in vivo. In contrast, a mutant lacking both prfAP1 and prfAP2 was 100-fold less virulent and was delayed in escape from the host vacuole. Once in the host cytoplasm, however, the double mutant was apparently normal in cell-to-cell spread.
PrfA转录激活因子是单核细胞增生李斯特菌致病机制的一个关键决定因素。prfA的表达受三个调控方式不同的启动子控制：prfAP1和prfAP2，它们位于prfA编码序列的紧邻上游，以及相邻的plcA启动子，通过生成plcA-prfA通读转录本发挥作用。构建了一系列启动子缺失突变体以评估prfAP1和prfAP2的作用。体外培养后，去除prfAP1或prfAP2都会导致PrfA调控基因的调控发生改变。然而，这些突变体在动物模型和感染组织培养模型中均具有完全的毒力，这表明两个prfA启动子在体内功能上是冗余的。相比之下，同时缺失prfAP1和prfAP2的突变体毒力降低了100倍，并且从宿主液泡中逃逸的过程延迟。然而，一旦进入宿主细胞质，双突变体在细胞间传播方面显然是正常的。
