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). 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. 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. Also involved in external sensory organ development. 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. 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.