Judah L. Rosner

Learn More
Since the growth of wild-type Escherichia coli in salicylate results in a multiple antibiotic resistance phenotype similar to that of constitutive mutants (Mar) of the chromosomal mar locus, the effect of salicylate on the expression of the marRAB operon was investigated. The amount of RNA hybridizing with a mar-specific DNA probe was 5 to 10 times higher(More)
A crystal structure for a member of the AraC prokaryotic transcriptional activator family, MarA, in complex with its cognate DNA-binding site is described. MarA consists of two similar subdomains, each containing a helix-turn-helix DNA-binding motif. The two recognition helices of the motifs are inserted into adjacent major groove segments on the same face(More)
The promoters of the mar/sox/rob regulon of Escherichia coli contain a binding site (marbox) for the homologous transcriptional activators MarA, SoxS and Rob. In spite of data from footprinting studies, the marbox has not been precisely defined because of its degeneracy and asymmetry and seemingly variable location with respect to the -10 and -35 hexamers(More)
Microarray analyses are providing a plethora of data concerning transcriptional responses to specific gene regulators and their inducers but do not distinguish between direct and indirect responses. Here, we identify directly activated promoters of the overlapping marA, soxS and rob regulon(s) of Escherichia coli by applying informatics, genomics and(More)
Elevated expression of the marORAB multiple antibiotic-resistance operon enhances the resistance of Escherichia coli to various medically significant antibiotics. Transcription of the operon is repressed in vivo by the marR-encoded protein, MarR, and derepressed by salicylate and certain antibiotics. The possibility that repression results from MarR(More)
The AraC family of bacterial transcriptional activators regulate diverse genetic systems. Recent X-ray diffraction studies show that the monomeric MarA and Rob activators bind to their asymmetric degenerate DNA sites via two different helix-turn-helix elements. Activation by MarA, SoxS or Rob requires a particular orientation of the asymmetric binding(More)
The paralogous transcriptional activators MarA, SoxS, and Rob activate a common set of promoters, the marA/soxS/rob regulon of Escherichia coli, by binding a cognate site (marbox) upstream of each promoter. The extent of activation varies from one promoter to another and is only poorly correlated with the in vitro affinity of the activator for the specific(More)
Expression of the marA or soxS genes is induced by exposure of Escherichia coli to salicylate or superoxides, respectively. This, in turn, enhances the expression of a common set of promoters (the mar/soxRS regulons), resulting in both multiple antibiotic and superoxide resistance. Since MarA protein is highly homologous to SoxS, and since a MalE-SoxS(More)
Transcriptional activation of the promoters of the mar/soxRS regulons by the sequence-related but independently inducible MarA and SoxS proteins renders Escherichia coli resistant to a broad spectrum of antibiotics and superoxide generators. Here, the effects of MarA and SoxS on transcription of the marRAB promoter itself were assayed in vitro by using a(More)