Post-transcriptional regulation of the virulence-associated enzyme Alg C by the σ22-dependent small RNA Ers A of P seudomonas aeruginosa.

The small RNA Ers A of P seudomonas aeruginosa, transcribed from the same genomic context of the well-known E scherichia coli Spot 42, has been characterized. We show that, different from Spot 42, Ers A is under the transcriptional control of the envelope stress response, which is known to impact the pathogenesis of P . aeruginosa through the activity of the alternative sigma factor σ22. The transcriptional responsiveness of Ers A RNA also spans infection-relevant cues that P . aeruginosa can 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 Ers A is that Ers A does not seem to be involved in the regulation of carbon source catabolism. Instead, our results suggest that Ers A is linked to anabolic functions for the synthesis of exoproducts from sugar precursors. We show that Ers A directly operates in the negative post-transcriptional regulation of the alg C gene that encodes the virulence-associated enzyme Alg C, which provides sugar precursors for the synthesis of several P . aeruginosa polysaccharides. Like Ers A, the activation of alg C expression is also dependent on σ22. Altogether, our results suggest that Ers A and σ22 combine in an incoherent feed-forward loop to fine-tune Alg C enzyme expression. [ABSTRACT FROM AUTHOR]