Post-transcriptional regulation of the virulence-associated enzyme AlgC by the σ22-dependent small RNA ErsA ofPseudomonas aeruginosa


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Abstract

SummaryThe small RNA ErsA ofPseudomonas aeruginosa, transcribed from the same genomic context of the well-knownEscherichia coliSpot 42, has been characterized. We show that, different from Spot 42, ErsA is under the transcriptional control of the envelope stress response, which is known to impact the pathogenesis ofP. aeruginosathrough the activity of the alternative sigma factor σ22. The transcriptional responsiveness of ErsA RNA also spans infection-relevant cues thatP. aeruginosacan experience in mammalian hosts, such as limited iron availability, temperature shifts from environmental to body temperature and reduced oxygen conditions. Another difference between Spot 42 and ErsA is that ErsA does not seem to be involved in the regulation of carbon source catabolism. Instead, our results suggest that ErsA is linked to anabolic functions for the synthesis of exoproducts from sugar precursors. We show that ErsA directly operates in the negative post-transcriptional regulation of thealgCgene that encodes the virulence-associated enzyme AlgC, which provides sugar precursors for the synthesis of severalP. aeruginosapolysaccharides. Like ErsA, the activation ofalgCexpression is also dependent on σ22. Altogether, our results suggest that ErsA and σ22 combine in an incoherent feed-forward loop to fine-tune AlgC enzyme expression.

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