Affiliation:
1. Department of Microbiology and Immunology, Indiana University School of Medicine-Northwest, Gary, Indiana 46408
2. Center for Pharmaceutical Biotechnology, University of Illinois, Chicago, Illinois 60607
3. Department of Microbiology, University of Wisconsin, Madison, Wisconsin 53706
Abstract
ABSTRACT
In
Staphylococcus aureus
, the SaeRS two-component system (TCS) encoded by the
saePQRS
operon controls expression of major virulence factors, such as coagulase and alpha-hemolysin. The
saePQRS
operon has two promoters: P1 and P3. The P1 promoter, a strong promoter, is autoinduced and can transcribe all four genes. Compared with P1, P3 shows fairly low but constitutive promoter activity, and it transcribes only
saeR
and
saeS
, the two genes encoding response regulator SaeR and sensor kinase SaeS. However, the role of each promoter in
sae
signaling has not been rigorously defined. In this study, we found that the genuine transcription start site (TSS) of P3 is located 78 nucleotides downstream of the previously reported TSS. Subsequently, the P3 promoter sequence was identified and validated by mutagenesis analyses. Deletion of the
saePQ
region including the P1 promoter did not significantly alter the expression patterns of coagulase and alpha-hemolysin, two well-known
sae
target genes. Due to its L18P substitution in a transmembrane domain, SaeS in strain Newman has a constitutive kinase activity. Interestingly, the mutation also rendered the protein unstable, but the protein stability was restored by SaeQ, suggesting a possible SaeQ-SaeS interaction. Ironically, the same mutation seems to increase mRNA stability. SaeR appears to be stabilized by SaeS, possibly by a protein-protein interaction. Chromosomal mutation of P1 did not affect the expression pattern of coagulase and alpha-hemolysin. Based on these results, we conclude that transcription of
saeRS
from P3 is sufficient for target gene activation and that P1 is not involved in the activation.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
64 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献