The sigma factors of Mycobacterium tuberculosis: regulation of the regulators

Abstract

One of the important determinants of virulence of Mycobacterium tuberculosis is adaptation to adverse conditions encountered in the host cells. The ability of Mycobacterium to successfully adapt to stress conditions is brought about by the expression of specific regulons effected by a repertoire of σ factors. The induction and availability of σ factors in response to specific stimuli is governed by a complex regulatory network comprising a number of proteins, including σ factors themselves. A serine-threonine protein kinase-mediated signaling pathway adds another dimension to the mycobacterial s factor regulatory network. This review highlights the recent advances in understanding mycobacterial σ factors, their regulation and contribution to bacterial pathogenesis.