Function and mechanism of action of the small regulatory RNA ArcZ in Enterobacterales.

Abstract

ArcZ is a small regulatory RNA conserved in Enterobacterales. It is a Hfq-dependent RNA that is cleaved by RNase E in a processed form of 55 to 60 nucleotides. This processed form is highly conserved for controlling the expression of target mRNAs. ArcZ expression is induced by abundant oxygen levels and reaches its peak during the stationary growth phase. This control is mediated by the oxygen-responsive two-component system ArcAB, leading to the repression of arcZ transcription under low-oxygen conditions in most bacteria in which it has been studied. ArcZ displays multiple targets, and it can control up to 10% of a genome and interact directly with more than 300 mRNAs in Escherichia coli and Salmonella enterica. ArcZ displays a multi-faceted ability to regulate its targets through diverse mechanisms such as RNase recruitment, modulation of ribosome accessibility on the mRNA and interaction with translational enhancing regions. By influencing stress response, motility and virulence through the regulation of master regulators such as FlhDC or RpoS, ArcZ emerges as a major orchestrator of cell physiology within Enterobacterales.