Regulation of cytochrome components by NrrF, a Fur-controlled small noncoding RNA.

NrrF is a small regulatory RNA of the human pathogen . NrrF was previously shown to repress succinate dehydrogenase () under control of the ferric uptake regulator (Fur). Here, we provide evidence that cytochrome , encoded by the polycistronic mRNA , is a NrrF target as well. We demonstrated differential expression of cytochrome comparing wild-type meningococci and meningococci expressing NrrF when sufficient iron is available. Using a -reporter system monitoring translational control and target recognition of sRNA in , we show that interaction between NrrF and the 5' untranslated region of the mRNA results in its repression. The NrrF region essential for repression of was identified by site-directed mutagenesis and is fully conserved among meningococci. Our results provide further insights into the mechanism by which Fur controls essential components of the respiratory chain. Adaptation of cytochrome complex component levels upon iron limitation is post-transcriptionally regulated via the small regulatory RNA NrrF.