Identification of promoters recognized by RNA polymerase containingMycobacterium tuberculosisstress-response sigma factor σF

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A previously optimized Escherichia coli two-plasmid system was used to identify Mycobacterium tuberculosis promoters recognized by RNA polymerase containing the M. tuberculosis stress response sigma factor σF. The method allowed the identification of five new σF-dependent promoters. Transcriptional start points of the promoters were determined by high-resolution S1-nuclease mapping using RNA prepared from E. coli containing the two-plasmid system. The promoters were confirmed by an in vitro transcription assay. The Mycobacterium smegmatis and Mycobacterium tuberculosis core RNA polymerases, after complementation with σF, were able to recognize all the five promoters. All the promoters contained sequences highly similar to the sequence of the previously identified M. tuberculosis σF-dependent promoter, usfXp1. Comparison of the promoters revealed a σF consensus sequence GtTtga-N14-18-GGGTAT. The σF-dependent promoters may govern expression of genes encoding a transcription regulator homologous to the response regulators of bacterial two-component signal transduction systems and proteins with unknown function.

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