ArtR, a novel sRNA of Staphylococcus aureus, regulates α-toxin expression by targeting the 5' UTR of sarT mRNA.

Recent studies point to the importance of small-noncoding RNAs (sRNAs) in bacterial virulence control. In Staphylococcus aureus, functional dissections of sRNAs are limited to RNA III, SprD, RsaE, SprA1, and SSR42 only. Here, we report the identification and functional analyses of a novel sRNA, which we have designated ArtR. Our data show that the AgrA protein can bind to the artR promoter and repress artR transcription, suggesting that, after RNA III, ArtR is the second sRNA regulated by AgrA. Furthermore, ArtR is unique in S. aureus and involved in virulence regulation by activating α-toxin expression. ArtR promotes the degradation of sarT mRNA by RNase III and arrests the translation of SarT by direct binding to the 5' untranslated region of the sarT mRNA, suggesting that the activation of ArtR on the α-toxin expression was through SarT. This study reveals another kind of staphylococcal regulatory small RNA that plays a role in virulence control. It also indicates the diversity of small RNA-target mRNA interactions and how these multiple interactions can mediate virulence regulation in this pathogen.