RNase Y of Staphylococcus aureus and its role in the activation of virulence genes

Summary RNase Y of Bacillus subtilis is a key member of the degradosome and important for bulk mRNA turnover. In contrast to B. subtilis, the RNase Y homologue (rny/cvfA )o fStaphylococcus aureus is not essential for growth. Here we found that RNase Y plays a major role in virulence gene regulation. Accordingly, rny deletion mutants demonstrated impaired virulence in a murine bacteraemia model. RNase Y is important for the processing and stabilization of the immature transcript of the global virulence regulator system SaePQRS. Moreover, RNase Y is involved in the acti- vation of virulence gene expression at the promoter level. This control is independent of both the viru- lence regulator agr and the saePQRS processing and may be mediated by small RNAs some of which were shown to be degraded by RNase Y. Besides this regu- latory effect, mRNA levels of several operons were significantly increased in the rny mutant and the half- life of one of these operons was shown to be extremely extended. However, the half-life of many mRNA species was not significantly altered. Thus, RNase Y in S. aureus influences mRNA expression in a tightly controlled regulatory manner and is essential for coordinated activation of virulence genes.