Rot Repression of Enterotoxin B Expression in Staphylococcus aureus

Abstract

The accessory gene regulator (Agr) system is a quorum-sensing system of Staphylococcus aureus responsible for upregulation of certain exoprotein genes and downregulation of certain cell-wall associated proteins during the post-exponential phase of growth. The enterotoxin B (seb) determinant is upregulated by the Agr system. Agr-regulated cis elements within the seb promoter region were examined by deletion analyses of the seb promoter by a hybrid promoter approach utilizing the staphylococcal lac operon promoter. To identify the regulatory pathway for enterotoxin B expression, the seb promoter fused to the chloramphenicol acetyltransferase reporter gene was introduced into mutants of S. aureus lacking agr or different members of the Sar family of transcriptional regulators. Agr control of seb promoter activity was found to be dependent upon the presence of a functional Rot protein, and Rot was shown to be able to bind to the seb promoter. Therefore, the Agr-mediated post-exponential-phase increase in seb transcription results from the Agr system's inactivation of Rot repressor activity.Staphylococcus aureus causes a wide range of diseases, including food poisoning, cutaneous infections, endocarditis, pneumonia, septic arthritis, and osteomyelitis (15,18). A variety of virulence factors are produced by this organism, including multiple exoproteins and cell wall-associated components (5,22,23). Coordinated regulation of expression of the many virulence genes is a critical feature of the pathogenicity of S. aureus, and the regulatory networks might provide sites of possible therapeutic intervention for the treatment of staphylococcal infections. To date, several global regulators have been identified that regulate the production of virulence-associated exoproteins and cell wall components. These global regulators include the accessory gene regulator (Agr), staphylococcal accessory regulator (SarA

The formation ofStaphylococcus aureusenterotoxin in food environments and advances in risk assessment

“…Rot binds to promoter regions, as shown for the seb promoter, thereby repressing the transcription of genes. [72][73][74] When the Agr system is induced during post-exponential growth RNAIII basepairs with rot mRNA. This mediates translational repression of rot mRNA, and subsequently lowers the amount of cellular Rot.…”

Regulation and characterization of rot transcription in Staphylococcus aureus

“…Although the phenotypic characterization of the rot gene has been performed thoroughly, the regulation and characterization of rot transcription are not well defined (McNamara et al, 2000;McNamara & Bayer, 2005;Said-Salim et al, 2003;Tseng & Stewart, 2005). Therefore, in order to determine the transcriptional start site and the promoter structure of the rot transcript and the probable length of the rot open reading frame, primer extension analysis was performed with total RNA isolated from the wild-type RN6390 and sarA mutant strains (Fig.…”

Rot and SaeRS Cooperate To Activate Expression of the Staphylococcal Superantigen-Like Exoproteins

“…The indirect regulation of virulence genes by RNAIII is mediated principally by posttranscriptional control of the transcription factor repressor of toxins (Rot), by which RNAIII prevents the translation of rot (8,19). Rot is a member of the SarA family of DNA binding proteins involved in the repression of genes that encode various secreted proteins and activation of genes that encode cell-associated proteins (11,30,35,47,53,54). …”