Fig. 1: RNA-guided, tDNA-dependent nuclease activation mechanism in NbaSPARDA systems.

a NbaAgo and APAZ-DREN form a heterodimer in the apo state. b Upon gRNA loading, NbaSPARDA undergoes dimerization. c Target recognition of complementary invading ssDNA leads to dissociation of the NbaSPARDA dimer into monomers. d Extension of the guide–target heteroduplex triggers the assembly of NbaSPARDA into a helical filament, accompanied by DREN domain tetramerization required for activation. e In the tetrameric DREN assembly, two DREN domains cooperatively stabilize substrate ssDNA or dsDNA, enabling non-specific collateral cleavage. This widespread nuclease activity results in degradation of both invader and host genomes, ultimately leading to cell death.