Intracellular induction of Listeria monocytogenes actA expression.
Intracellular induction of Listeria monocytogenes actA expression.
复制标题
细胞内诱导单核细胞增生李斯特氏菌 actA 表达。
DOI：
10.1128/iai.70.3.1087-1096.2002
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发表时间：
2002
影响因子：
3.1
通讯作者：
Freitag,NancyE
中科院分区：
文献类型：
--
作者：
Shetron-Rama,LynneM;Marquis,Hélène;Bouwer,HGArchie;Freitag,NancyE
Following entry into the host cytosol, the bacterial pathogenListeria monocytogenesdramatically increases the expression of several key virulence factors. The expression ofactA, whose protein product is required forL.monocytogenesactin-based intracellular motility, is increased by more than 200-fold in cytosolic bacteria in comparison to broth-grown cultures. Two distinct promoter elements have been reported to regulateactAexpression. One promoter is located immediately upstream ofactAcoding sequences, while the second promoter is contributed by the upstreammplgene via the generation of anmpl-actA-plcBtranscript. A series ofL.monocytogenesmutants were constructed to define the contributions of individual promoter elements toactAexpression. The intracellular induction ofactAexpression was found to be dependent upon theactAproximal promoter; themplpromoter appeared to contribute to the extracellular induction ofactAbut did not affect intracellular levels of expression. TheactApromoter is dependent upon a regulatory factor known as PrfA for transcriptional activation; however, no increase inactAexpression was detected following the introduction of a high-affinity PrfA binding site within theactApromoter. The presence of a mutationally activated form of PrfA, known as PrfA*, increased overallactAexpression in broth-grown cultures of both wild-type andactApromoter mutant strains, but the levels of induction observed were still approximately 50-fold lower than those observed for intracellularly grownL.monocytogenes. Collectively, these results indicate that the dramatic induction ofactAexpression that occurs in the host cell cytosol is mediated through a single promoter element. Furthermore, intracellular induction ofactAappears to require additional steps or factors beyond those necessary for the activation and binding of PrfA to theactApromoter.
