1887

Abstract

is one of the four operons in that encode exported proteins with a probable role in the virulence of this bacterium. Upstream of there is a putative regulatory gene () that harbours a double -family signature. To study the role of this putative regulatory gene in the transcriptional regulation of the operon, mc155 and H37Rv strains that harboured gene fusions between the promoter region and the gene, either containing or not containing the gene, were used. The presence of the gene in the strains greatly reduced β-galactosidase activity, suggesting that the -encoded protein is a transcriptional repressor of the operon. Expression of by recombinant was increased when it was grown in a macrophage-like cell line (J774), compared to the level of expression seen when the recombinant bacterium was grown under conditions. However, no lifting of repression was induced. The 3 promoter was defined by deletion and cloning of the intergenic region in a 200 bp DNA fragment harbouring the region upstream of the start codon. Gel-shift experiments determined that the Rv1963-binding site was located in this region. These results indicate that the operon is transcriptionally regulated and that under certain, unknown, conditions repression of gene expression could be lifted.

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2002-10-01
2020-04-02
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