The Escherichia coli transcriptional regulator MarA directly represses transcription of purA and hdeA.
The Escherichia coli MarA protein mediates a response to multiple environmental stresses through the activation or repression in vivo of a large number of chromosomal genes. Transcriptional activation for a number of these genes has been shown to occur via direct interaction of MarA with a 20-bp degenerate asymmetric "marbox" sequence. It was not known whether repression by MarA was also direct. We found that purified MarA was sufficient in vitro to repress transcription of both purA and hdeA. Transcription and electrophoretic mobility shift experiments in vitro using mutant promoters suggested that the marbox involved in the repression overlapped the -35 promoter motif and was in the "backward" orientation. This organization contrasts with that of the class II promoters activated by MarA, in which the marbox also overlaps the -35 motif but is in the "forward" orientation. We conclude that MarA, a member of the AraC/XylS family, can act directly as a repressor or an activator, depending on the position and orientation of the marbox within a promoter.
Schneiders
Thamarai
T
Center for Adaptation Genetics and Drug Resistance and the Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Barbosa
Teresa M
TM
McMurry
Laura M
LM
Levy
Stuart B
SB
D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D011401:Promoter Regions, Genetic; D014157:Transcription Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C080002:MarA protein, E coli; D014157:Transcription Factors; C084501:hdeA protein, E coli