4.1 Mechanistic coherence: Ago domains map to guide binding and catalytic competence

• The review’s central mechanistic claim is that Argonaute’s PIWI domain contains an RNase H-like fold supporting cleavage, and a catalytic residue tetrad is required for catalytic activity; defective tetrads imply cleavage-incompetent yet guide-dependent binding. Catalytic tetrad/PIWI slicer logic
• It also links guide 5′ end recognition (“MID pocket”) and 3′ end binding (“PAZ domain”) to how the guide is positioned for target engagement, including the described ‘seed region’ importance for target binding and cleavage positioning. Guide positioning: MID/PAZ/seed and cleavage site

4.2 It acknowledges where cross-domain generalization is risky

• On prokaryotes, the review repeatedly notes uncertainty about in vivo roles and guide biogenesis/loading, which is crucial because many prokaryotic Ago studies are described as in vitro. Caution about in vivo vs in vitro prokaryotic Ago evidence

5.1 Review-only nature limits falsifiability

Because this is explicitly a review, it cannot by itself resolve disputed points about prokaryotic Ago in vivo defense vs alternative intracellular roles; it depends on the literature it cites and the literature’s own biases and species coverage. Review synthesis + explicit uncertainty

5.2 Cross-kingdom “RNAi vs interference” boundary is not sharply defined

The paper uses the term “RNA interference” broadly for eukaryotic RNAi and discusses prokaryotic Ago interference including DNA targeting; however, the mechanistic and evolutionary equivalence is not established at the level of identical biochemical pathways. This matters because guide nucleic-acid identity (DNA vs RNA) and target cleavage modalities could lead to fundamentally different regimes. Eukaryotic RNAi vs prokaryotic Ago DNA targeting