Regulation of Rot expression in Staphylococcus aureus

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• Repressor of toxins (Rot) is a global regulator of virulence in *Staphylococcus aureus*.
• Rot activity is modulated by the Agr quorum-sensing system, while sigma(B) represses rot expression post-exponentially.

Purpose of the Study:

• To investigate the transcriptional regulation of rot expression in *Staphylococcus aureus*.
• To identify transcriptional factors affecting rot expression, particularly sigma(B) and SarS.

Main Methods:

• Comparative transcriptional profiling of *S. aureus* strains with and without sigma(B).
• Electrophoretic mobility shift assays (EMSA) to study protein-DNA interactions at the rot promoter.
• Affinity purification and N-terminal sequencing to identify DNA-binding proteins.
• Primer extension analysis to investigate rot transcription initiation.

Main Results:

• Rot expression is upregulated in the stationary phase in a sigma(B)-dependent manner.
• SarS negatively regulates rot expression; its absence leads to modest upregulation.
• SarA and SarR proteins were identified as binding to the rot promoter.
• Loss of Rot function in the postexponential phase is attributed to rot mRNA degradation, not transcriptional inhibition.

Conclusions:

• Sigma(B) plays a crucial role in the stationary phase upregulation of rot expression.
• SarS, SarA, and SarR are key regulators of rot transcription in *S. aureus*.
• Postexponential phase loss of Rot function is primarily mediated by mRNA instability.