Molecular basis of DosR-dependent transcription activation in Mycobacterium tuberculosis

The transcription activator DosR is a key dormancy regulator controlling latent infection of the worldwide pathogenic Mycobacterium tuberculosis (Mtb), but its molecular mechanism remains unclear. Here we determine the cryo-EM structure of an intact DosR-dependent transcriptional activation complex (DosR-TAC), comprising Mtb RNA polymerase (RNAP), DosR, and the hypoxic promoter DNA. The structure shows that two DosR monomers symmetrically dimerize through the N-terminal receiver domains (DosR_RECs) and the distinct α10 helices from the C-terminal DNA-binding domains (DosR_DBDs). Different from its inhibitory configuration, the functional DosR dimer exhibits significant conformational rearrangements, especially at the linker helix, which enable DosR to simultaneously contact promoter DNA and recruit RNAP by engaging the conserved domains (σ^AR4, αCTD, and αNTD). These results coincide with in vitro and in vivo assays. These findings, along with the previous observations, support an 'allosteric activation-recruitment' model for DosR-dependent transcription activation and offer potential targets for developing anti-dormancy strategies against tuberculosis.