E3 ubiquitin-protein ligase that mediates E2-dependent, 'Lys-48'- and/or 'Lys-63'-linked polyubiquitination of substrates (PubMed:30503771). Recognizes miRNA-empty Ago1 and triggers its degradation via polyubiquitination independently of the Bag6 complex (PubMed:30503771). By targeting miRNA-empty Ago1, eliminates dysfunctional Ago1 not able to bind miRNA and thereby plays a role in the quality control of miRNA-mediated silencing (PubMed:30503771). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Interacts (via N-terminus) with CG7546 (via Ubl domain). 'Iruka' means dolphin in Japanese. The name was chosen because dolphin preys on the Argonauta octopus, similar to Iruka 'preying' on the protein Argonaute.