Dual ATPase-activated DNA hemimethylation and cleavage by the MANTIS defence system

Bacterial defence systems act as crucial barriers against horizontal gene transfer and phage infection. While restriction-modification systems were initially discovered and remain common, the self/non-self discrimination in many methylation-based systems remains unclear. The MANTIS (Methyltransferase, ATPases and Nuclease Targeting Inverted-repeat Sequences) defence system, previously known as Gao_RL, has now been elucidated.

Utilizing phage infection and plasmid transformation assays in Pseudomonas aeruginosa, biochemical reconstitution, and structural biology analyses, researchers have discovered that MANTIS establishes self-identity through adenine hemimethylation of specific DNA sequences. The system's activation requires the co-regulators MtsA and MtsB, both of which are necessary for recruiting and activating the methyltransferase MtsC. This discovery reveals an ATP-dependent mechanism for epigenetic modification.

Upon DNA recognition by the MtsABC complex, a dimeric helicase-nuclease effector (MtsD) is triggered to restrict the target site. The restriction activity's efficiency depends on the architecture of the target site: inverted pairs of unmodified sites support robust restriction, while direct repeats or single sites are restricted less efficiently. Virulent phages exhibit strand-biased depletion of MANTIS target sites, indicating an evolutionary pressure to evade restriction.

The findings shed light on how dual ATPases couple self-modification to non-self restriction, providing a framework to understand the growing landscape of methylation-based defence systems.