Regulatory Elements of theStaphylococcus aureusProtein A (Spa) Promoter

Abstract

Staphylococcal protein A (Spa) is an important virulence factor of Staphylococcus aureus. Transcription of the spa determinant occurs during the exponential growth phase and is repressed when the cells enter the postexponential growth phase. Regulation of spa expression has been found to be complicated, with regulation involving multiple factors, including Agr, SarA, SarS, SarT, Rot, and MgrA. Our understanding of how these factors work on the spa promoter to regulate spa expression is incomplete. To identify regulatory sites within the spa promoter, analysis of deletion derivatives of the promoter in host strains deficient in one or more of the regulatory factors was undertaken, and several critical features of spa regulation were revealed. The transcriptional start sites of spa were determined by primer extension. The spa promoter sequences were subcloned in front of a promoterless chloramphenicol acetyltransferase reporter gene. Various lengths of spa truncations with the same 3 end were constructed, and the resultant plasmids were transduced into strains with different regulatory genetic backgrounds. Our results identified upstream promoter sequences necessary for Agr system regulation of spa expression. The cis elements for SarS activity, an activator of spa expression, and for SarA activity, a repressor of spa expression, were identified. The well-characterized SarA consensus sequence on the spa promoter was found to be insufficient for SarA repression of the spa promoter. Full repression required the presence of a second consensus site adjacent to the SarS binding site. Sequences directly upstream of the core promoter sequence were found to stimulate transcription.

Response of corneal epithelial cells toStaphylococcus aureus

“…The observation that agonists of these receptors did not effect CCL20 expression by these cells would be consistent with the previous observation that little TLR2 occurs on the surface of the human cornea normally, 24 suggesting that S. aureus is sensed by these cells via another pathway. It was previously noted that protein A, which is expressed by S. aureus early in log phase, 43 is capable of stimulating TNFα and IL8 expression by corneal epithelial cells in a TLR2 independent fashion, 44 supporting this prospect.…”

Structural and function analyses of the global regulatory protein SarA from Staphylococcus aureus

“…2). The notion of a SarA multimer in binding to DNA was also supported by results of gel-retardation assays, showing a large mobility shift of the protein-DNA complex (9,11,12,(22)(23)(24). It will be of interest to understand how these multiple homodimers bind to their target DNA and their association with each other.…”

Incidence of Methicillin-Resistant Staphylococcus aureus Isolation from Sheep and Goat

“…Approximately 25-40% of the population is colonized with S. aureus. It is also a common cause of skin and soft tissue infections (Francois et al, 2005) and sometimes causes severe disease such as pneumonia, bacteremia, meningitis, sepsis, and pericarditis and food poisoning (Gao and Stewart, 2004;von-Eiff et al, 2001). In animals, S. aureus bacteria isolated and identified as an important opportunist that can cause superficial to life -threatening illness in a variety of animal (White et al, 2003).…”