E3 ubiquitin-protein ligase that mediates ubiquitination and subsequent proteasomal degradation of target proteins. The adapter phyl is required to direct the degradation of the two isoforms of the transcriptional repressor 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. It probably triggers the ubiquitin-mediated degradation of different substrates. A phyl-independent mechanism of degradation exists for isoform beta of ttk that involves motifs in the C-terminus of ttk. 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 with ebi and phyl. Expressed in pupae and in adults, with a higher expression in males than females. The RING-type zinc finger domain is essential for ubiquitin ligase activity. The SBD domain (substrate-binding domain) mediates the homodimerization and the interaction with substrate proteins. It is related to the TRAF family. Flies are viable. In combination with a mutation in ebi, flies show an extra dorsal central bristle phenotype. Flies that lack both sina and sinah show visible eye and bristle phenotypes, which can be explained by an inability to degrade the neuronal repressor, Tramtrack. Belongs to the SINA (Seven in absentia) family.