Structural insights into transcription regulation of the global virulence factor PhoP from Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb), remaining as the leading cause of the worldwide threat Tuberculosis, relies heavily on its transcriptional reprogramming of diverse stress genes to swiftly adapt to adverse environments and ensure infections. The global virulence factor PhoP plays a pivotal role in coordinating transcription activation or repression of the essential phosphate-nitrogen metabolic remodeling genes. However, what defines PhoP to deferentially act as an activator or a repressor remains largely unexplored. Here, we determine one cryo-EM structure of Mtb RNAP-promoter open complex, three cryo-EM structures of PhoP-dependent transcription activation complexes (PhoP-TACs) consisting of Mtb RNA polymerase (RNAP), different number of PhoP molecules binding to different types of well-characterized consensus promoters, and one cryo-EM structure of Mtb PhoP-dependent transcription repression complex (PhoP-TRC) comprising of Mtb RNAP, PhoP, the nitrogen metabolism regulator GlnR and their co-regulated promoter. Structural comparisons reveal phosphorylation of PhoP is required for stabilization of PhoP-TACs, PhoP specifically recognizes promoters as novel tandem dimers and recruits RNAP through extensively interacting with its conserved {beta} flap and {sigma}AR4 domains. Strikingly, the distinct promoter spacer length and PhoP-GlnR interactions in PhoP-TRC constrain the upstream DNA into a distinct topology and retain PhoP in a novel dragging repression mode. Collectively, these data highlight the dual regulatory mechanisms of PhoP-dependent transcription regulation in governing stress adaptation. These findings provide structural basis for developing potential anti-tuberculosis drugs and/or interventions.