Cascade of extracytoplasmic function sigma factors in Mycobacterium tuberculosis: Identification of a σJ-dependent promoter upstream of sigI

Abstract

A previously optimized Escherichia coli two-plasmid system was used to identify promoters recognized by RNA polymerase containing the Mycobacterium tuberculosis extracytoplasmic function (ECF) sigma factor σJ. The only positive clone revealed a promoter directing expression of the sigI gene encoding ECF sigma factor σI. The transcriptional start point of the promoter was determined and the promoter was confirmed by an in vitro transcription assay with either E. coli or Mycobacterium smegmatis core RNA polymerase and isolated σJ. © 2008 Federation of European Microbiological Societies.