The LysR-type transcriptional regulator CysB controls the repression of hslJ transcription in Escherichia coli.
The LysR-type transcriptional regulator (LTTR) CysB is a transcription factor in Escherichia coli cells, where as a homotetramer it binds the target promoter regions and activates the genes involved in sulphur utilization and sulphonate-sulphur metabolism, while negatively autoregulating its own transcription. The hslJ gene was found to be negatively regulated by CysB and directly correlated with novobiocin resistance of the bacterium. cysB mutants showed upregulation of the hslJ : : lacZ gene fusion and exhibited increased novobiocin resistance. In this study the hslJ transcription start point and the corresponding putative sigma(70) promoter were determined. The hslJ promoter region was defined by employing different hslJ-lacZ operon fusions, and transcription of the hslJ gene was shown to be subject to both repression imposed by the CysB regulator and direct or indirect autogenous negative control. These two regulations compete to some extent but they are not mutually exclusive. CysB acts as a direct repressor of hslJ transcription and binds the hslJ promoter region that carries the putative CysB repressor site. This CysB binding, apparently responsible for repression, is enhanced in the presence of the ligand N-acetylserine (NAS), hitherto considered to be a positive cofactor in CysB-mediated gene regulations. Interallelic complementation of characterized CysB mutants I33N and S277Ter partially restored the repression of hslJ transcription and the consequent novobiocin sensitivity, but did not complement the cysteine auxotrophy.
Jovanovic
Milija
M
Institute of Molecular Genetics and Genetic Engineering, Vojvode Stepe 444A, PO Box 446, 11001 Belgrade, Serbia and Montenegro.
Lilic
Mirjana
M
Institute of Molecular Genetics and Genetic Engineering, Vojvode Stepe 444A, PO Box 446, 11001 Belgrade, Serbia and Montenegro.
Savic
Dragutin J
DJ
Institute of Molecular Genetics and Genetic Engineering, Vojvode Stepe 444A, PO Box 446, 11001 Belgrade, Serbia and Montenegro.
Jovanovic
Goran
G
Institute of Molecular Genetics and Genetic Engineering, Vojvode Stepe 444A, PO Box 446, 11001 Belgrade, Serbia and Montenegro.
D000483:Alleles; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; C062886:CysB protein, Bacteria; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D014157:Transcription Factors; C073470:LysR protein, Bacteria