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Abstract
In Escherichia coli, small RNAs GlmY and GlmZ feedback control synthesis of glucosamine-6-phosphate (GlcN6P) synthase GlmS, a key enzyme required for synthesis of the cell envelope. Both small RNAs are highly similar, but only GlmZ is able to activate the glmS mRNA by base-pairing. Abundance of GlmZ is controlled at the level of decay by RNase adaptor protein RapZ. RapZ binds and targets GlmZ to degradation by RNase E via protein–protein interaction. GlmY activates glmS indirectly by protecting GlmZ from degradation. Upon GlcN6P depletion, GlmY accumulates and sequesters RapZ in an RNA mimicry mechanism, thus acting as an anti-adaptor. As a result, this regulatory circuit adjusts synthesis of GlmS to the level of its enzymatic product, thereby mediating GlcN6P homeostasis. The interplay of RNase adaptor proteins and anti-adaptors provides an elegant means how globally acting RNases can be re-programmed to cleave a specific transcript in response to a cognate stimulus.
Disclosure of Potential Conflicts of Interest
No potential conflicts of interest were disclosed.
Acknowledgments
We thank Petra Dersch, Ralf Ficner, Eliane Hajnsdorf, Slawomir Milewski, and Jörg Vogel for fruitful collaborations and all members of the DFG priority program SPP1258 for inspiring discussions. Our research on GlmY and GlmZ was supported by grants in the framework of the German DFG priority program SPP1258 “Sensory and Regulatory RNAs in Prokaryotes.”