M ycobacterium tuberculosis ori C sequestration by MtrA response regulator

Summary The regulators of M ycobacterium tuberculosis   DNA replication are largely unknown. Here, we demonstrate that in synchronously replicating M . tuberculosis , MtrA access to origin of replication ( ori C ) is enriched in the post‐replication ( D ) period. The increased ori C binding results from elevated MtrA phosphorylation ( MtrA ∼ P ) as evidenced by reduced expression of dna N , dna A and increased expression of select cell division targets. Overproduction of gain‐of‐function MtrA Y102C advanced the MtrA   ori C access to the C period, reduced dna A and dna N expression, interfered with replication synchrony and compromised cell division. Overproduction of wild‐type ( MtrA +) or phosphorylation‐defective MtrA D56N did not promote ori C access in the C period, nor affected cell cycle progression. MtrA interacts with DnaA signaling a possibility that DnaA helps load MtrA on ori C . Therefore, ori C sequestration by MtrA ∼ P in the D period may normally serve to prevent untimely initiations and that DnaA – MtrA interactions may facilitate regulated ori C replication. Finally, despite the near sequence identity of MtrA in M . smegmatis and M . tuberculosis , the M . smegmatis ori C is not MtrA ‐target. We conclude that M . tuberculosis ori C has evolved to be regulated by MtrA and that cell cycle progression in this organisms are governed, at least in part, by oscillations in the MtrA ∼ P levels.