Molecular mechanism of the key dormancy regulator DosR-dependent transcription activation in Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) is the etiological agent responsible for the worldwide disease Tuberculosis. DosR is recognized as the key dormancy regulator of Mtb due to its global transcriptional regulation in intracellular adaptation and long-term persistence prevailing in latent infection. However, the molecular mechanism regarding DosR-dependent transcription activation remains inadequately defined. Here, we successfully determined 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. In DosR-TAC, two DosR monomers symmetrically dimerize through their N-terminal receiver domains (DosR_RECs) and the distinct α10 helices of the C-terminal DNA-binding domains (DosR_DBDs). Unlike its inhibitory configuration, the DosR dimer undergoes significant conformational changes within the original linker, isomerizing DosR_REC into a canonical (βα)5 fold. This extended linker affords the DosR_DBDs and DosRI_REC to contact promoter DNA, while concurrently interacting with the conserved domains of RNAP (σAR4, αCTD, and αNTD). Additionally, RT-qPCR and growth curve assays of the wild-type and DosR mutant strains, also unravel the physiological importance of this divergent linker. These findings, together with prior hypotheses regarding DosR, support an allosteric activation-recruitment model for DosR. Altogether, these results highlight the molecular mechanism of DosR-dependent transcription activation critical for dormancy survival of Mtb, and offer potential targets for developing anti-dormancy strategies against persistent tuberculosis.