Role of upstream sequences in the expression of the staphylococcal enterotoxin B gene

The staphylococcal enterotoxin B gene (seb) is positively regulated at the transcriptional level (Gaskill, M. E., and Khan, S. A. (1988) J. Biol. Chem. 263, 6276-6280). The sequences involved in the regulation of transcription of the seb gene have been studied by deletion analysis. A multicopy Staphylococcus aureus plasmid carrying the cloned seb gene was used to generate a series of mutants that are deleted in the upstream region of this gene. The levels of enterotoxin B protein and mRNA produced by the deletion mutants were analyzed. A region between 59 and 93 nucleotides upstream of the transcription initiation site was found to be required for transcription and expression of the seb gene. Deletion of this sequence greatly reduced or eliminated transcription of the seb gene. DNA-protein binding experiments showed that cell-free extracts made from an staphylococcal enterotoxin B-producing strain contain protein(s) that specifically bind to the upstream region. This protein may be involved in the transcriptional activation of the seb gene.