Identification and characterization of a second, inducible promoter of relA in Escherichia coli.
The alarmone ppGpp is an important signal molecule for the stringent response. Escherichia coli relA encodes a ppGpp synthetase, and although the regulation of RelA protein activity has been studied extensively, the regulation of relA transcription remains unclear. Here, we describe a novel relA promoter, relAP2. According to quantitative measurement of mRNA by primer extension analysis, the previously reported promoter relAP1 is constitutively active throughout growth, while relAP2 is induced temporarily at the transition state between the exponential growth and stationary phases. A chromosomal transcriptional lacZ fusion (relAP2-lacZ) showed that relAP2 is positively regulated by H-NS and CRP. Furthermore, the reduced activity of relAP2-lacZ in an hns mutant could be rescued by an rpoS mutation, which is sufficient to derepress the relAP2-lacZ activity. These data suggest that transient expression from the relAP2 promoter is controlled by several global regulators. This may account for the complex regulation of relA expression in Escherichia coli.
Nakagawa
Akira
A
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
Oshima
Taku
T
Mori
Hirotada
H
D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D008025:Ligases / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic
D008025:Ligases; C028812:guanosine 3',5'-polyphosphate synthetases