E3 ubiquitin-protein ligase that mediates ubiquitination and subsequent proteasomal degradation of target proteins. 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. Induces cellular growth arrest by inhibiting the G2/M transition (PubMed:15055544). May play a role in the regulation of the cellular clock function (By similarity). 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. Homodimer. In embryos it is expressed in all blastomeres starting at the mid-blastulla. After 20 somite stage, it is expressed mainly in the posterior part. Expressed in brain, including the eye, the cranial cavity, otic vesicle, optic chiasm and in the gut. Expressed both maternally and zygotically. 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. Belongs to the SINA (Seven in absentia) family.