Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain.
Institute for Bioengineering of Catalonia, The Barcelona Institute of Science and technology, Barcelona, Spain.
Environ Microbiol Rep. 2018 Apr;10(2):202-209. doi: 10.1111/1758-2229.12621.
In this report, we show that bacterial plasmids that harbor the Tn10 transposon (i.e., the IncHI1 plasmid R27) modify expression of different Salmonella regulons responding to the presence of tetracycline (Tc) in the medium. By using as a model the Tc-dependent upregulation of the ibpAB operon (which belongs to the heat shock regulon), we have identified Tn10-tetA (coding for a Tc efflux pump) and adjacent tetC sequences as required for ibpAB upregulation. Characterization of transcripts in the tetAC region showed that tetA transcription can continue into tetC sequences, generating a long 3'UTR sequence, which can protect transcripts from RNA processing, thus increasing the expression of TetA protein. In the presence of Tc, the DnaK and IbpA chaperones are overexpressed and translocated to the periplasm and to the membrane fraction respectively. DnaK targeting unfolded proteins is known to induce heat shock by avoiding RpoH proteolysis. We correlate expression levels of Tn10-encoded TetA protein with heat shock induction in Salmonella, likely because TetA activity compromises protein secretion.
在本报告中，我们表明，携带 Tn10 转座子（即 IncHI1 质粒 R27）的细菌质粒会修饰对培养基中四环素（Tc）存在的不同沙门氏菌调控子的表达。通过使用依赖于 Tc 的 ibpAB 操纵子（属于热休克调控子）的上调作为模型，我们已经确定了 Tn10-tetA（编码 Tc 外排泵）和相邻的 tetC 序列是 ibpAB 上调所必需的。在 tetAC 区域的转录本的特征表明，tetA 转录可以继续进入 tetC 序列，产生长的 3'UTR 序列，该序列可以保护转录本免受 RNA 加工，从而增加 TetA 蛋白的表达。在 Tc 的存在下，DnaK 和 IbpA 伴侣蛋白被过度表达并分别转运到周质和膜部分。已知 DnaK 靶向未折叠蛋白可通过避免 RpoH 蛋白水解来诱导热休克。我们将 Tn10 编码的 TetA 蛋白的表达水平与沙门氏菌中的热休克诱导相关联，这可能是因为 TetA 活性会损害蛋白质分泌。
