CspA regulation of Staphylococcus aureus carotenoid levels and σ^B activity is controlled by YjbH and Spx

Abstract

Staphyloxanthin, a carotenoid in S. aureus, is a powerful antioxidant against oxidative stresses. The crtOPQMN operon driving pigment synthesis is under the control of σ B . CspA, a cold shock protein, is known to control σ B activity. To ascertain genes that regulate cspA, we screened a transposon library that exhibited reduced cspA expression and pigmentation. We found that the adaptor protein YjbH activates cspA expression. Spx, the redox-sensitive transcriptional regulator and a proteolytic target for YjbH and ClpXP, complexes with αCTD of RNAP prior to binding the cspA promoter to repress cspA activity. Increased cspA expression in trans in the inactive spx C10A mutant of JE2 did not enhance pigment production while it did in JE2, suggesting that cspA is downstream to Spx in pigmentation control. As the staphyloxanthin pigment is critical to S. aureus survival in human hosts, we demonstrated that the cspA and yjbH mutants survived less well than the parent in whole blood killing assay. Collectively, our studies suggest a pathway wherein YjbH and ClpXP proteolytically cleave Spx, a repressor of cspA transcription, to affect σ B -dependent carotenoid expression, thus providing a critical link between intracellular redox sensing by Spx and carotenoid production to improve S. aureus survival during infections.

Revisiting the regulation of the capsular polysaccharide biosynthesis gene cluster in Staphylococcus aureus

“…Indeed, it was recently shown that MsaB/CspA binds rsbVWsigB mRNA, thereby increasing transcript stability (Caballero et al , ). Strong influence of MsaB/CspA on SigB activity is consistent with previous findings that MsaB/CspA increases expression of sigB and its target genes (Katzif et al , ; Sahukhal and Elasri, ; Donegan et al , ). With respect to direct P cap regulation, our results indicate that under the conditions employed, the region containing the previously described IR motif functions instead as a promoter for the SigB holoenzyme.…”

One evolutionarily selected amino acid variation is sufficient to provide functional specificity in the cold shock protein paralogs of Staphylococcus aureus

“…This indicated that out of the three CSP paralogs, CspA was solely responsible for promoting STX synthesis (Figure a). Previous studies showed that the deletion of cspB also affected STX production (Donegan et al, ; Duval et al, ). Due to differences in the strains, culture media and bacterial growth conditions between said studies, the expression levels of CSPs might not be comparable.…”

“…STX production is carried out by the proteins encoded in the crtOPQMN operon, which depends on the alternative sigma B factor ( σ B ) for its transcription. Analogously, the activity of σ B is modulated by CspA (Caballero et al, ; Donegan et al, ; Katzif, Lee, Law, Tzeng, & Shafer, ). We previously showed that CspA directly interacts with the rsbV‐rsbW‐sigB operon, resulting in an improved σ B activity (Caballero et al, ).…”

“…Similar variations in band migration had previously been shown for Salmonella CSPs (Michaux et al, ). A possible explanation might be protein modification but this possibility has not been found for CSPs yet (Donegan et al, ). This also applied to several of the chimeric CSPs, which migrated differently when compared to the WT CSPs.…”

“…Therefore, STX has been proposed as a potential target when fighting MRSA infections (Liu et al, ). In addition, CspB has also been implicated in STX production (Donegan, Manna, Tseng, Liu, & Cheung, ; Duval, Mathew, Satola, & Shafer, ), suggesting a putative functional redundancy of CSPs in S. aureus . However, whether a particular S. aureus CSP may be able to compensate for the lack of expression of its counterparts remains unknown.…”