MicF RNA

MicF RNA is a small non-coding RNA (sRNA) found in Escherichia coli and other related bacteria. It functions as a post-transcriptional regulator, primarily through base-pairing interactions with target messenger RNAs (mRNAs). This interaction typically leads to translational repression or mRNA degradation, thereby controlling the expression of the target genes.

The primary target of MicF RNA is the ompF mRNA. ompF encodes an outer membrane porin protein, OmpF, which facilitates the diffusion of small molecules across the outer membrane of the bacterium. By binding to the ompF mRNA, MicF RNA inhibits the synthesis of OmpF protein. This regulation is important for bacterial survival in different environmental conditions. Specifically, the repression of OmpF production by MicF RNA is advantageous under conditions of osmotic stress or high temperature, as OmpF is a relatively large pore and its expression could lead to influx of harmful substances or destabilization of the cell envelope.

The expression of MicF RNA is controlled by various environmental factors, including osmotic stress and temperature, as well as by regulatory proteins like the EnvZ-OmpR two-component system. This allows the bacterium to rapidly adapt its gene expression in response to changing conditions. The increased expression of MicF RNA under stress conditions allows for downregulation of OmpF, contributing to stress resistance.

MicF RNA folds into a characteristic secondary structure with multiple stem-loop regions. These structures are important for its stability, interactions with mRNA targets, and binding to the RNA chaperone protein Hfq, which facilitates its interaction with target mRNAs. Hfq binding enhances the efficiency of MicF RNA regulation.

Beyond ompF, MicF RNA has been shown to regulate other target genes, though ompF remains the best-characterized target. These additional targets further contribute to the broader regulatory role of MicF RNA in bacterial physiology and adaptation.