E3 ubiquitin-protein ligase that is required for specification of R7 photoreceptor cell fate in the eye by mediating the ubiquitination and subsequent proteasomal degradation of Tramtrack (ttk) (PubMed:9267026, PubMed:9267027, PubMed:11526076, PubMed:12215542, PubMed:18160715). E3 Ubiquitin ligases accept ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates (PubMed:12215542). Acts via the formation of a complex with ebi and phyl that ubiquitinates the transcription repressor ttk, a general inhibitor of photoreceptor differentiation, in a subset of photoreceptor cells in the eye, leading to the differentiation of cells into neurons (PubMed:9267026, PubMed:9267027, PubMed:11526076, PubMed:12215542). Also involved in external sensory organ development (PubMed:11526076). 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. Component of some E3 complex at least composed of sina, ebi and phyl. Interacts with eff. In many ommatidial precursor cells. The RING-type zinc finger domain is essential for ubiquitin ligase activity. The SBD domain (substrate-binding domain) mediates the interaction with substrate proteins. It is related to the TRAF family. Belongs to the SINA (Seven in absentia) family.