J Bacteriol, May 1998, p. 2568-2573, Vol. 180, No. 9
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
10"
Promoters from Mycobacteria
andDepartment of Biochemistry, University of Delhi South Campus, New Delhi-110021, India
Received 1 October 1997/Accepted 28 February 1998
Earlier studies from our laboratory on randomly isolated
transcriptional signals of mycobacteria had revealed that the
10 region of mycobacterial promoters and the corresponding binding domain
in the major sigma factor are highly similar to their Escherichia coli counterparts. In contrast, the sequences in
35 regions of mycobacterial promoters and the corresponding binding domain in the
major sigma factor are vastly different from their E. coli counterparts (M. D. Bashyam, D. Kaushal, S. K. Dasgupta, and
A. K. Tyagi, J. Bacteriol. 178:4847-4853, 1996). We have now
analyzed the role of the TGN motif present immediately upstream of the
10 region of mycobacterial promoters. Sequence analysis and
site-specific mutagenesis of a Mycobacterium tuberculosis
promoter and a Mycobacterium smegmatis promoter reveal that
the TGN motif is an important determinant of transcriptional strength
in mycobacteria. We show that mutation in the TGN motif can drastically
reduce the transcriptional strength of a mycobacterial promoter. The
influence of the TGN motif on transcriptional strength is also
modulated by the sequences in the
35 region. Comparative assessment
of these extended
10 promoters in mycobacteria and E. coli suggests that functioning of the TGN motif in promoters of
these two species is similar.
Present address: Eukaryotic Gene Expression Laboratory, National
Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India.
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