The phzA2-G2 Transcript Exhibits Direct RsmA-Mediated Activation in Pseudomonas aeruginosa M18

作者：Bin Ren, Huifeng Shen, Zhi John Lu, Haiming Liu, Yuquan Xu · 发表于：PLoS ONE · 年份：2014 · DOI：10.1371/journal.pone.0089653 · 被引用次数：51 · 研究领域：Bacterial Genetics and Biotechnology、Bacterial biofilms and quorum sensing、Antibiotic Resistance in Bacteria

In bacteria, RNA-binding proteins of the RsmA/CsrA family act as post-transcriptional regulators that modulate translation initiation at target transcripts. The Pseudomonas aeruginosa genome contains two phenazine biosynthetic (phz) gene clusters, phzA1-G1 (phz1) and phzA2-G2 (phz2), each of which is responsible for phenazine-1-carboxylic acid (PCA) biosynthesis. In the present study, we show that RsmA exhibits differential gene regulation on two phz clusters in P. aeruginosa M18 at the post-transcriptional level. Based on the sequence analysis, four GGA motifs, the potential RsmA binding sites, are found on the 5'-untranslated region (UTR) of the phz2 transcript. Studies with a series of lacZ reporter fusions, and gel mobility shift assays suggest that the third GGA motif (S3), located 21 nucleotides upstream of the Shine-Dalgarno (SD) sequence, is involved in direct RsmA-mediated activation of phz2 expression. We therefore propose a novel model in which the binding of RsmA to the target S3 results in the destabilization of the stem-loop structure and the enhancement of ribosome access. This model could be fully supported by RNA structure prediction, free energy calculations, and nucleotide replacement studies. In contrast, various RsmA-mediated translation repression mechanisms have been identified in which RsmA binds near the SD sequence of target transcripts, thereby blocking ribosome access. Similarly, RsmA is shown to negatively regulate phz1 expression. Our new finding...