A global function of sroA in Staphylococcus aureus

Abstract

Staphylococcus aureus is one of the most significant human bacterial pathogens due to its etiological role in deadly sepsis infections and frequent drug-resistant isolates. S. aureus pathogenesis is driven by its virulence factors that are tightly regulated. One factor that plays a role in regulating virulence is the extracytoplasmic function alternative sigma factor, SigS. SigS is necessary for S. aureus virulence, immune evasion, and response to stressors. The Thompson Lab recently executed experiments to characterize the regulon of SigS, resulting in the discovery of two small previously uncharacterized open reading frames (ORFs), SroA and SroB. SigS and SroA form an auto-regulatory loop, with SigS directly regulating sroA transcription and SroA regulating the expression of SigS at the level of RNA stability. Previous studies from the Thompson Lab also identified several potential regulatory targets. From prior transcriptome studies, we identified the narGHJI operon as the strongest inhibitory target. Yet, there are major unknowns about SroA driving this study. The mechanism driving SroA regulation of its targets is not clear. Therefore, in this study, I set out to further understand the post-transcriptional regulation of SigS (a positive regulatory target) and narGHJI (a negative regulatory target). Finally, I also set out to identify the SroA interactome to understand the genome impact of SroA. To characterize the effect of SroA on SigS, I looked at the role of RNases on SigS regulation to determine if cellular RNases are involved in SigS turnover. I also analyzed the expression of narG following SroA over-expression. SroA over-expression did result in decreased narG mRNA levels. Furthermore, SroA RIP-sequencing resulted in the identification of potential RNA interactions that will need additional biochemical verification.