The small RNA SprY controls RNAIII function and affects Staphylococcus aureus virulence

While a plethora of small regulatory RNAs (sRNAs) have been identified in the human pathogen Staphylococcus aureus, the physiological function of most of them remains unknown. We report the characterization of SprY, a sRNA from S. aureus expressed from a pathogenicity island. RNAIII, a major regulator of S. aureus virulence, was discovered as a potential SprY target by an MS2-affinity purification assay. In silico interaction studies suggest a RNA-RNA pairing between the SprY 5’end and the 13rd stem-loop of RNAIII. Overproduction of SprY leads to a 1.5-fold reduction of RNAIII amount. By affecting the rnaIII expression, SprY affects the amount of RNAIII known targets. Indeed, SprY downregulates hla mRNA translation, but also upregulates other secreted factors such as Ecb and Rot. Furthermore, SprY decreases the hemolytic activity and virulence of S. aureus. Our results lead to propose that SprY is involved in S. aureus virulence through a post-transcriptional regulation of RNAIII. Transcriptome analysis by RNA-seq to monitor the levels of all transcripts in bacterial cells grown in the absence or the presence of a subinhibitory concentration (8 mg/L) of caspofungin.