Recent Articles

Dubnau E, Fontan P, Manganelli R, Soares-Appel S, Smith I.
Mycobacterium tuberculosis genes induced during infection of human macrophages.
Infect Immun 2002 Jun;70(6):2787-95
PMID: 12010964

We identified Mycobacterium tuberculosis genes preferentially expressed during
infection of human macrophages using a promoter trap adapted for this pathogen.
inhA encodes an enoyl-acyl carrier protein reductase that is required for
mycolic acid biosynthesis (A. Quemard et al., Biochemistry 34:8235-8241, 1995)
and is a major target for isoniazid (INH) in mycobacterial species (A. Banerjee
et al., Science 263:227-230, 1994). Since overexpression of inhA confers INH
resistance in Mycobacterium smegmatis (Banerjee et al., Science 263:227-230,
1994), we designed a promoter trap based on this gene. A library of clones,
containing small fragments of M. tuberculosis DNA cloned upstream of inhA in a
plasmid vector, was electroporated into M. tuberculosis, and the resulting
culture was used to infect the human monocytic THP-1 cell line. Selection was
made for clones surviving INH treatment during infection but retaining INH
sensitivity on plates. The DNA upstream of inhA was sequenced in each clone to
identify the promoter driving inhA expression. Thirteen genes identified by this
method were analyzed by quantitative reverse transcription-PCR (R. Manganelli et
al., Mol. Microbiol. 31:715-724, 1999), and eight of them were found to be
differentially expressed from cultures grown in macrophages compared with
broth-grown cultures. Several of these genes are presumed to be involved in
fatty acid metabolism; one potentially codes for a unique DNA binding protein,
one codes for a possible potassium channel protein, and the others code for
proteins of unknown function. Genes which are induced during infection are
likely to be significant for survival and growth of the pathogen; our results
lend support to the view that fatty acid metabolism is essential for the
virulence of M. tuberculosis.