Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, 414 E Clark St. Vermillion, SD 57069, USA.
Plasmid. 2010 Jul;64(1):26-35. doi: 10.1016/j.plasmid.2010.03.002. Epub 2010 Mar 21.
Conjugation of the E. faecalis plasmid pCF10 is triggered in response to peptide sex pheromone cCF10 produced by potential recipients. Regulation of this response is complex and multi-layered and includes a small regulatory RNA, Anti-Q that participates in a termination/antitermination decision controlling transcription of the conjugation structural genes. In this study, the secondary structure of the Anti-Q transcript and its sites of interaction with its target, Qs, were determined. The primary site of interaction occurred at a centrally-located loop whose sequence showed high variability in analogous molecules on other pheromone-responsive plasmids. This loop, designated the specificity loop, was demonstrated to be important but not sufficient for distinguishing between Qs molecules from pCF10 and another pheromone-responsive plasmid pAD1. A loop 5' from the specificity loop which carries a U-turn motif played no demonstrable role in Anti-Q-Qs interaction or regulation of the termination/antitermination decision. These results provide direct evidence for a critical role of Anti-Q-Qs interactions in posttranscriptional regulation of pCF10 transfer functions.
粪肠球菌质粒 pCF10 的连接是响应潜在受体产生的肽性信息素 cCF10 而触发的。这种反应的调节非常复杂，包括一个小的调节 RNA Anti-Q，它参与了控制接合结构基因转录的终止/抗终止决策。在这项研究中，确定了 Anti-Q 转录本的二级结构及其与靶标 Qs 的相互作用位点。主要的相互作用位点发生在一个中央环上，其序列在其他响应信息素的质粒上的类似分子中表现出高度的可变性。这个环，称为特异性环，被证明是区分 pCF10 和另一个响应信息素的质粒 pAD1 的 Qs 分子的重要但非必要的因素。特异性环上游的一个带有 U 形转弯模体的环在 Anti-Q-Qs 相互作用或终止/抗终止决策的调节中没有发挥明显的作用。这些结果为 Anti-Q-Qs 相互作用在 pCF10 转移功能的转录后调节中的关键作用提供了直接证据。
