Small RNA-based feedforward loop with AND-gate logic regulates extrachromosomal DNA transfer in Salmonella

作者：Kai Papenfort, Elena Espinosa, Josep Casadesús, Jörg Vogel · 发表于：Proceedings of the National Academy of Sciences · 年份：2015 · DOI：10.1073/pnas.1507825112 · 被引用次数：83 · 研究领域：Bacterial Genetics and Biotechnology、RNA and protein synthesis mechanisms、CRISPR and Genetic Engineering

Horizontal gene transfer via plasmid conjugation is a major driving force in microbial evolution but constitutes a complex process that requires synchronization with the physiological state of the host bacteria. Although several host transcription factors are known to regulate plasmid-borne transfer genes, RNA-based regulatory circuits for host-plasmid communication remain unknown. We describe a posttranscriptional mechanism whereby the Hfq-dependent small RNA, RprA, inhibits transfer of pSLT, the virulence plasmid of Salmonella enterica. RprA employs two separate seed-pairing domains to activate the mRNAs of both the sigma-factor σ(S) and the RicI protein, a previously uncharacterized membrane protein here shown to inhibit conjugation. Transcription of ricI requires σ(S) and, together, RprA and σ(S) orchestrate a coherent feedforward loop with AND-gate logic to tightly control the activation of RicI synthesis. RicI interacts with the conjugation apparatus protein TraV and limits plasmid transfer under membrane-damaging conditions. To our knowledge, this study reports the first small RNA-controlled feedforward loop relying on posttranscriptional activation of two independent targets and an unexpected role of the conserved RprA small RNA in controlling extrachromosomal DNA transfer.