INVESTIGADORES
GOLDSTEIN RAIJ Jorge
artículos
Título:
Negative transcriptional regulation of the mce3 operon in Mycobacterium tuberculosis.
Autor/es:
SANTANGELO MP, GOLDSTEIN J, ALITO A, GIOFFRÉ A, CAIMI K, ZABAL O, ZUMÁRRAGA M, ROMANO MI, CATALDI AA, BIGI F
Revista:
MICROBIOLOGY-UK
Editorial:
Society for General Microbiology
Referencias:
Año: 2002 vol. 148 p. 2997 - 3006
ISSN:
1350-0872
Resumen:
mce3 is one of the four mce operons in Mycobacterium tuberculosis that
encode exported proteins with a probable role in the virulence of this
bacterium. Upstream of mce3 there is a putative regulatory gene
(Rv1963) that harbours a double tetR-family signature. To study the
role of this putative regulatory gene in the transcriptional regulation
of the mce3 operon, Mycobacterium smegmatis mc(2)155 and M.
tuberculosis H37Rv strains that harboured gene fusions between the mce3
promoter region and the Escherichia coli lacZ gene, either containing
or not containing the Rv1963 gene, were used. The presence of the
Rv1963 gene in the strains greatly reduced beta-galactosidase activity,
suggesting that the Rv1963-encoded protein is a transcriptional
repressor of the mce3 operon. Expression of mce3 by recombinant M.
tuberculosis 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 in vitro conditions. However, no
lifting of repression was induced. The mce3 promoter was defined by
deletion and cloning of the Rv1963-Rv1964 intergenic region in a 200 bp
DNA fragment harbouring the region upstream of the Rv1964 start codon.
Gel-shift experiments determined that the Rv1963-binding site was
located in this region. These results indicate that the mce3 operon is
transcriptionally regulated and that under certain, unknown, conditions
repression of gene expression could be lifted.