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J. Bacteriol., Jan 1996, 418-423, Vol 178, No. 2
JH Heinrichs, MG Bayer and AL Cheung
The expression of cell wall and extracellular proteins in Staphylococcus
aureus is controlled by global regulatory systems, including sar and agr.
We have previously shown that a transposon insertion into the 372-bp sarA
gene within the sar locus resulted in decreased expression of several
extracellular and cell wall proteins (A. L. Cheung and S. J. Projan, J.
Bacteriol. 176:4168-4172, 1994). In this study, Northern (RNA blot)
analysis with a 732-bp sarA probe indicated that two major transcripts
(0.56 and 1.2 kb) were absent in the sar mutant compared with the parental
strain RN6390. Additional transcriptional studies revealed that the sarA
gene is encoded within the 0.56-kg transcript. Notably, a plasmid carrying
the sarA gene together with a 1.2-kb upstream fragment (1.7 kb total) was
able to reestablish the 1.2-kb transcript in the mutant. Although
reconstitution of the parental phenotype by the sarA gene was incomplete,
the introduction of a plasmid carrying the 1.7-kb fragment to the mutant
restored the parental phenotype. Transcription of RNAII and RNAIII, which
encode the structural and regulatory genes of agr, respectively, was
diminished in the mutant but restored to wild-type levels by
complementation with the 1.7-kb fragment. In gel shift assays, cell
extracts of this clone were able to retard the mobility of a labeled RNAII
promoter probe but not an RNAIII promoter element. These data suggest that
sarA and the adjacent upstream DNA are essential to the expression of a
DNA-binding protein(s) with specificity for the RNAII promoter, thereby
controlling agr-related transcription.
Copyright © 1996, American Society for Microbiology
Characterization of the sar locus and its interaction with agr in Staphylococcus aureus
Laboratory of Bacterial Pathogenesis and Immunology, Rockefeller University, New York, New York 10021, USA.
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