The ω Subunit Governs RNA Polymerase Stability and Transcriptional Specificity in Staphylococcus aureus

Staphylococcus aureus is a major human pathogen that causes infection in a wide variety of sites within the human body. Its ability to adapt to the human host, and to produce a successful infection, requires precise orchestration of gene expression. While DNA-dependent RNA polymerase (RNAP) is generally well characterized, the role of several small accessory subunits within the complex has yet to be fully explored. This is particularly true for the omega (ω or RpoZ) subunit, which has been extensively studied in Gram-negative bacteria, but largely neglected in Gram-positive counterparts. In Escherichia coli, it has been shown that ppGpp binding, and thus control of the stringent response, is facilitated by ω. Interestingly, key residues that facilitate ppGpp binding by ω are not conserved in S. aureus, and consequently, survival under starvation conditions is unaffected by rpoZ deletion. Further to this, ω-lacking strains of S. aureus display structural changes in the RNAP complex, which result from increased degradation and misfolding of the β’ subunit, alterations in δ and σ-factor abundance, and a general dissociation of RNAP in the absence of ω. Through RNAseq analysis we detected a variety of transcriptional changes in rpoZ-deficient strains, presumably as a response to the negative effects of ω-depletion on the transcription machinery. These transcriptional changes translated to an impaired ability of ΔrpoZ mutant strains to resist stress, and to fully form a biofilm. Collectively, our data underlines, for the first time, the importance of ω for RNAP stability, function and cellular physiology in S. aureus. Two Samples