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Evidence of Complex Transcriptional, Translational, and Posttranslational Regulation of the Extracytoplasmic Function Sigma Factor σE in Mycobacterium tuberculosis

ABSTRACT The extracytoplasmic factor (ECF) sigma factor σE is one of the most studied sigma factors of Mycobacterium tuberculosis. It has been shown to be involved in virulence as well as in survival under conditions of high temperature, alkaline pH, and exposure to detergents and oxidative stress. Unlike many ECF sigma factors, σE does not directly regulate the transcription of its own gene. Two promoters have been identified upstream of the sigE gene; one is regulated by the two-component system MprAB, while the other has been shown to be σH dependent. In this paper, we further characterize the regulation of σE by identifying its anti-sigma factor and a previously unknown promoter. Finally, we show that sigE can be translated from three different translational start codons, depending on the promoter used. Taken together, our data demonstrate that σE not only is subjected to complex transcriptional regulation but is also controlled at the translational and posttranslational levels.