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Functioning of mycobacterial heat-shock repressors requires the master virulence regulator PhoP.

ABSTRACT

A hallmark feature of (Mtb) pathogenesis lies in the ability of the pathogen to survive within the macrophages under a stressful environment. Thus, coordinated regulation of stress proteins is critically important for an effective adaptive response of Mtb, failure to which results in elevated immune recognition of the tubercle bacilli with reduced survival during chronic infections. Here, we show that virulence regulator PhoP impacts on global regulation of heat-shock proteins, which protect Mtb against stress generated by macrophages during infection. Our results identify that in addition to classical DNA-protein interactions, newly discovered protein-protein interactions control complex mechanisms of expression of heat-shock proteins, an essential pathogenic determinant of Mtb. While the C-terminal domain of PhoP binds to its target promoters, the N-terminal domain of the regulator interacts with the C-terminal end of the heat-shock repressors. Remarkably, our findings delineate a regulatory pathway which involves three major transcription factors PhoP, HspR and HrcA that control recruitment of the regulators within the target genes and regulate stress-specific expression of heat-shock proteins via protein-protein interactions. The results have implications on the mechanism of regulation of PhoP-dependent stress response in Mtb.Regulation of heat-shock proteins which protect against stress generated by macrophage during infection is poorly understood. In this study, we show that PhoP, a virulence regulator of the tubercle bacilli controls heat-shock-responsive genes, an essential pathogenic determinant of Our results unravel that in addition to classical DNA-protein interactions, complex mechanisms of regulation of heat shock-responsive genes occur through multiple protein-protein interactions. Together, these findings delineate a fundamental regulatory pathway where transcription factors PhoP, HspR and HrcA interact with each other to control stress- specific expression of heat-shock proteins. Copyright © 2019 American Society for Microbiology.